Going geothermal

Yesterday Gareth Hughes and I visited the Contact Energy geothermal power complex at Wairakei. It was a chance to see how the power stations work including how the energy is managed and how water and waste is treated It was a fascinating opportunity to go inside the older facility at Wairakei built in the 1950’s and 1960’s and to walk through the new power station being tested as we speak at Te Mihi. We were shown the bioreactor that was developed to treat the water from the Wairakei plant before it is returned to the Waikato River and to see the test bores and drill sites. The Contact people were very helpful and welcoming. We had lots of questions for them because renewable and truly sustainable are not always synonymous.

Catherine and Gareth at Wairakei Geothermal Plant
Catherine and Gareth at Wairakei

The new geothermal plants being developed reuse more of their water and are very efficient. Wairakei is being adapted but will close around 2026. The technology was described as “bespoke” as every geothermal field is different and requires different management. I was particularly interested in the reinjection process into deep water aquifers because Contact had raised concerns about my Resource Management Amendment Bill on rivers impacting on their consents to discharge geothermal fluids into the earth and underground water. We met after the Select Committee submission process and negotiated how we could amend my Bill to achieve my goals for rivers and allow their geothermal discharges to be status quo under law. This has been a positive process as was the visit. Interestingly Contact had brought one of their senior staff to meet us and debate the NZ Power proposal which they are concerned about in terms of their shareholders. A lively discussion on the price of power and the modelling we are proposing ensued. Gareth and I were pretty upfront about making power work for citizens and industries, not just the shareholders of the big 5 companies. We support geothermal power, all kinds of renewables and a positive intervention for a fair price to all our people.

The geothermal resource is being well managed and sustained, the story of its development is extraordinary in terms of renewable energy, and it was great to meet the people who run the power stations on the ground. The political debate about a fair model that that brings power to all the people wasn’t resolved yesterday but we are more than happy to engage in it.

108 Comments Posted

  1. The document I linked to only discusses the required changes, so I don’t know if the unchanged part mentions a minimum size. In any case, the System Operator (Transpower) will choose the lowest expected cost combination of Frequency Keepers which can provide the required amount of regulation, typically +/-50MW. So if there is just one small offering, it is unlikely to be included in the combination as for most of the combinations of Frequency Keeper options, the 50MW can be met without adding in the small station, or it can’t be met even with the small station. However knowing this, the companies owning the bigger frequency keepers may opt to offer just short of the required total so that the small station can be included in their mix, but they would need to see a benefit to themselves to do so.

    I agree that this rule amendment is a sensible step for the EA to take.


  2. Which is good news. There is clearly a lot that the EA don’t know (yet) and this is a tentative step so as not to preclude anything other that a straight generator that the rules today clearly do.

    I suspect that should a “real” proposal be tabled that says that to be economic we need the control range to be -10MWh to +10MWh then that is just a pair of numbers to be entered into the trading system and would be acceptable. The trading system calculates the range and mid-point from the entered numbers. There should be no reason why the midpoint should not be zero. The reality is that the system operator would just purchase more straight generation than if the control range was 10MWh to 30MWh.

    The real oddment is that there is no minimum size of participant. Can one participate at 10MW load? 1MW? 100KW? Where does it start to make sense? Presumably if one can offer 1MW at the lowest price then one would get selected, in this brave new multi-keeper world…

  3. The Electrical Authority are taking steps to make it easier for switchable loads to be used for frequency keeping:

    However they don’t seem to have grasped the concept of a single station that can both inject and absorb power and switch between the two in real time, such as either a station with generation and switchable loads, or a station with reversible storage. (I say this because they don’t mention the sign of the minimum or maximum power levels.)


  4. “Let us also assume I’ve got an electric car, which needs recharging. Its drawing 5KVA from the grid. As noted above, the frequency of the grid has dropped below nominal. My charger reduces its load to 3KVA.”
    The frequency returns to 50Hz, so does your charger stay at 3KVA or does it ramp back up to 5KVA? If the frequency peaks a little above 50Hz, will smart chargers draw more power if they can? You end up with some chargers drawing more power than others because of slight differences in their measurement of the frequency.

    As I said above, what would work is for the smart devices to measure the time error and react to that. Also if the meter has the smarts, the load(s) can be simpler, and all the mucking around with rebate cards can be avoided too.


  5. The frequency and rate of change of frequency are not indicators of supply or load

    Yes, they are. Really. Or perhaps using slightly more exact terminology, they are indicators of the imbalance of supply and load.

    Lets take an example. The frequency is below the nominal. The frequency keeper will ramp up its output to attempt to restore frequency to the nominal. I’m sure we agree on that. It does so because the low frequency is a sure sign that there is more load than generation.

    Lets also assume I’ve got an electric car, which needs recharging. Its drawing 5KVA from the grid. As noted above, the frequency of the grid has dropped below nominal. My charger reduces its load to 3KVA. I (and many others who do the same thing) have helped to stabilize the frequency by reducing the load on the grid.

    Because my car charger behaves this way, I don’t pay $20c a KWh for my recharging power, I pay $14c/KWh. Of course, I pay 20c/KWh as its on the same meter as everything else, but there’s a sealed box on the charger with a card, and I take this card down to the dairy or the NZ Post office every now and again and a rebate appears on next months bill.

    Joe down the road only pays $6c for the juice that heats his swimming pool. I could charge my car on that tariff too, but don’t want to risk it not being charged up in the morning. Joe doesn’t mind if his pool temperature is anywhere over cold, he’s not fussed what temperature it is, but its really cheap for him to have his pool heated. His pool heater is connected to his WiFi, so his billing happens automagically.

    Its all possible. With technology available today. This isn’t a techncial problem, its a tariff problem. If the right tariffs were there then the boxes would be on the shelves overnight.

    Of course: the software that drives these little boxes has to be smart; the box has to learn (and keep learning) by how and when much each box should reduce or increase its load, to ensure that the grid doesn’t become unstable.

  6. The frequency and rate of change of frequency are not indicators of supply or load as the frequency keeping stations adjust their output to bring the frequency back to 50Hz.

    With the cheap availability of GPS equipment, it is now possible to receive a very accurate time signal nearly anywhere. The difference between this time signal and the time signal from clocks synchronised to the 50Hz mains frequency is kept to within 5 seconds by the frequency keeping stations but could lag slightly at times of high load and lead at times of low load, so this might be a usable signal to control the types of loads that you suggest. For this to work, the GPS receiver would need to be incorporated in the metering equipment and signal to the load that the price had increased or decreased so that if the load were able to respond (and the owner of the load wanted it to respond) then it could do so. The load could then become a frequency keeper in its own right, as you are suggesting. However I suspect that it would still need a control link from a central station so it could handle some unusual situations if they arise, including the aftermath of power outages.

    The loads could include recharging systems for electric vehicles of course.


  7. “The price signal isn’t a real-time control signal, it is a tariff, a tariff one is entitled to use if one has plant that meets certain specifications.”

    The tariff sets the price. The frequency (and rate of change of frequency) sets when you can use that cheap electricity.

  8. You implied it when you wrote:
    “By having plant that responds to frequency, a customer can take advantage of dirt cheap electricity when the network is under-loaded and over-generated.”


  9. Again: where do you get the idea that frequency and price are related? This discussion would go a lot better if you read what I write.

    I had the suggestion in your last paragraph some years ago. Although it still a good idea, it is an alternative, parallel idea to frequency responsive loads, not a replacement.

  10. dbuckley – while at first glance the power frequency would appear to indicate how much load there is and therefore the price, on closer analysis it simply isn’t true. Instead the instantaneous frequency is a better indication of how much the load is changing, but it is also affected by how much the supply is changing too. It can’t be otherwise because day or night, the average frequency has to stay at 50Hz give or take no more than 5 seconds. It is one of the requirements of the frequency keeping station to keep clocks on time to within 5 seconds.

    To make matters even more confusing, the amount of frequency swing is not just related to the excess or shortfall of supply versus demand, but is also determined by how much inertia is connected, and will swing more when a lot of motors and generators are shut down, such as early mornings.

    What would work is for the power retailers to transmit signals to their meters indicating the current price of power and for this to be passed on to equipment that can adjust its load accordingly. Whether this is via ripple control, cell phone technology or internet is up to the power companies. The key detail is that the price updates could be as often as every half hour, and would be linked to the electricity spot price. It is not sufficient to signal to the load that the spot price of electricity has fallen if the meter that is going to charge the consumer doesn’t also receive this signal.


  11. ChrisM – all the information you have provided just shows that my statement (that frequency keepers are usually or always hydro) wasn’t far from the truth as it was a few weeks ago. The frequency keeping station in the South Island is Hydro. In the North Island, when Mighty River Power are or were frequency keeping, they use hydro as well. When Genesis are frequency keeping, they can use some hydro and coal or gas. So the frequency keepers are usually hydro. I have no information about any changes in the last month.

    And yes, I am well aware that Transpower is the System Operator.

    However all this is largely irrelevant to the point that I was making, which was that adding some resistive load directly under the control of the frequency keeping station could be used to reduce the average generation from this station and allow more generation to be used from intermittents, as well as giving more power range to that frequency keeper.

    I don’t disagree that adding to the amount of wind generation will require more frequency keeping reserves, and I can even go along with the idea that the operators of the wind farms should be paying for that extra frequency keeping cost, based on the extent that their wind turbines are disturbing the system frequency. This would encourage them to select turbines that can control their ramp up rate for example. There will be a number of problems to be faced as we try to increase the share of power generated by renewables, and these problems will require a range of solutions.


  12. Trevor

    I do wish you could comprehend the articles you link to, or even just read them.
    The three stations are probably Maraetai 1, Marataei 2 and Tokaanu – they had the special governors in the NZE days.
    Did you actually read what Genesis said about the difficulties of using them for frequency keeping especially as the submission was about the problems of wind. Since then, the situation has got a lot worse – that is what the EA article is about. Genesis was effectively opting out as they were having problems keeping there turbines within operating conditions because the swings were so big. With MRP doing it using small hydro machines, the management became very poor. I believe that Stratford got the main contract 1st July- the system does seem smoother – and rumour is that it is worth about $10M a year just as an MFK – all a subsidy for wind generators.
    The System Operator, which is Transpower not EA, doesn’t deign to converse with mere mortals but prefers to reign by imperial fiat. They don’t publish either successful tenderer or the cost but his is the services they were looking for:

  13. So ChrisM, was that contract for just half an hour, or have things changed since the EA put this on their site:

    Since Mighty River Power Ltd have been providing frequency keeping in the North Island, which station(s) do they use to do that?

    I tried to find more information and came across this 2005 submission:
    It says that of the four North Island frequency keeping stations, three were hydro (page 5, point 18). Has this changed since?


  14. Where on earth do you get the idea I’m talking about “longer term responses”?

    I’m talking about instant. Fractions of a second.

    The price signal isn’t a real-time control signal, it is a tariff, a tariff one is entitled to use if one has plant that meets certain specifications. A price signal that encourages certain behaviour.

    The actual real-time control signal is inherent in AC electricity; it is the frequency. Frequency goes up, increase your load. Frequency drops, you decrease your load. By having plant that responds to frequency, a customer can take advantage of dirt cheap electricity when the network is under-loaded and over-generated.

    This approach to frequency management makes conventional frequency control look, well, sluggish. How sluggish? Well, watch NI frequency in real time.

  15. Please get it right Trevor.
    The frequency keeping in the North Island is mainly thermal and it has been that way for years – since Huntly commissioning. They have special governors for the purpose. Currently the contract is with with the GE peakers at Stratford.

  16. Agreed in principal but the frequency keeping station must respond quickly to load changes. If the load drops suddenly, then it needs to reduce its output or switch in its own load. It cannot wait to see if other stations react or other load is switched on. My suggestion reduces the amount of water consumed by the frequency keeping station (which in New Zealand is usually or always a hydro station).

    You are talking about longer term responses, which is more about maintaining margins. For this purpose, price signals sent to the loads make more sense than having loads respond to changes in frequency. After all, the frequency only changes and stays changed if the frequency keeping station can’t do its job.


  17. But a better idea is to allow customers to use that power that would otherwise be dumped. It could do something useful. Heat municipal swimming pools for example.

    The problem remains one of tariffs, not technology. There are any number of organizations who would have loads that could be “the loads of last resort” to absorb excess power should the wind blow a bit hard. And who could drop load should the wind experience a lull.

    To take a step backwards: we need to have frequency regulation on the generation side because generation never matches load, so we ramp generation up or down a bit to keep frequency to as near as possible to 50hz. Or, as postulated above, we could, if the frequency rises, just switch on additional loads to restore equilibrium.

    If we’ve got that far, then having a proportion of the loads as responsive loads at outset can augment the generation frequency keeping, by “doing the right thing” when there is a generation/load imbalance.

  18. dbuckley suggested that multi-megawatt resistive loads were cheap, so it would be possible to get rid of excess generation cheaply. I think I know just the place for it:

    If 10-20MW of electronically controlled resistive loads were installed at the frequency keeping stations under the direct control of the frequency keeping software, then instead of running at 50MW +/- 50MW, they could run at 40MW +60/-50MW, increasing the range of control but also reducing the average amount of water required to maintain control, allowing another 10MW (or more) of intermittent or must run generation to be used with minimal waste. The only waste would be if there were a significant further drop in demand or a surge in generated power requiring the extra loads to be switched in until the system settles down again.

    (The target output level would only need to be lowered during periods of low demand, and can operate normally at other times.)

    This would not give a large saving but every little bit helps, allowing a small increase in the amount of intermittent power that the system can handle.


  19. And how are they going to justify running gas fired generation and not renewables when the renewables can generate, so the water gets spilled or the wind farms get feathered?


  20. I think that it is fairly safe to rely on their profit seeking managers to cut back the expensive to operate fossil fueled generation and to use as far as practical the renewable generation.

    I think you fundementally misunderstand the nature of the business upon which you are commenting, and in particular, who margin and profit are accounted for, and the fact that their profit needs to be seen to be reasonable.

    It is the Labour / Green position that the electricity industry are rorting consumers. It is the electricity industries position that they only make about 5% on their costs so they are not profiteering.

    Both these statements are true.

    For the electricity companies to make the most money they have to have the highest consumer electricity price possible, and it has to be justifiable (ie not a visible 15% margin) and thus they need as high a cost basis as is reasonably possible, and therefore they should choose the more expensive option, as it leads to the better justfiable profit.

    You are concluding that they will try to minimise costs to maximise margins. I think that will prove to be wrong. They could do that today, and and could have done so for the years since the reforms, but they haven’t and don’t, so why should the imposition of an ETS make a jot of difference to their behaviour? Where is the evidence that adding an ETS will turn the established principles upside down?

    Simply put, if you add an ETS cost into their costs, they will pass on their cost with a margin on top to the consumers. Do the sums, and the ETS is in favour of the electricity industry; it is an opportunity to increase absolute profit by increasing prices whilst being able to justify the increase in electricity prices being “due to the ETS”.

  21. dbuckley – The tax or ETS would increase the electricity price to consumers by taxing generation that releases CO2. If consumption drops as a result, which generation do you think the electricity generation companies are going to cut back – the ones with the zero fuel cost and no CO2 emissions and therefore no CO2 tax, or the ones with the significant fuel cost and the high CO2 charges? I think that it is fairly safe to rely on their profit seeking managers to cut back the expensive to operate fossil fueled generation and to use as far as practical the renewable generation. So CO2 emissions will fall, if not now then when the stupid fossil fuel burners go bankrupt.


  22. Well. If we still owned all the electricity companies we could simply direct them to develop more renewable energy sources.

    Then the gray cardiganed engineers, on 80 to 150k a year, would go ahead and do it.

    We could even, heaven forbid, fund it through taxation from current tax payers, or by some QE, as we did for some of the original generation, instead of putting our money into dodgy ponzi schemes, like Kiwi saver which will disappear, in the next inevitable GFC.

  23. BJ says of me:

    Notice how you just invoked the BAU must continue as is in your tacit assumptions?

    Indeed, as that is the current and probable future reality.

    But…….. if there were to be significant structural changes in the electicity industry, which would dump the current spot price market system, then you could start again in terms of thinking how you want to optimise electicity for the nation. One could preferentially choose less environmentally damaging generation where possible.

    Under such circumstances, one can actually change things directly, rather than attempting behavioural change (a derivitive of direct change) using the clumsy inequitable tool that is a carbon tax.

  24. Electricity companies don’t actively promote electricity consumption, though they do benefit from any increase.

    I believe they tacitly have encouraged consumption. Or perhaps they have encouraged peak load.

    For the benefit of just about everyone other than ChrisM, it is important to note that the investment required in generation, transmission and distribition is based on the peak load at an instant, whereas the revenue and running costs are determined by the total consumption over a period of time.

    The clever people who built New Zealands electricity system knew this, and thus to constrain necessary investment as far as possible, they installed one of the worlds most comprehensive consumer demand control arrangements, ripple control.

    When the pseudo-market-reforms came in, effective ripple control had to go. Why? Because the industry needed more money.

    By abandoning ripple control and building to peak load, the investment in the electrical system could be increased dramatically, so that the peak could be handled. More generation and transmission.

    Of course, all this had to be paid for. And this cost of course appears on our bills. And the eleccy compnaies profits are a measure of what they make after all the revenue minus all the costs. So more investment means more costs means more justifiable revenue means numerically larger profits, whilst still appearing as a sane percentage.

    Which is one of the ways that you can take a raw indegient that costs $5 or $10 and sell it to consumers for $200 and still only make a 5% profit. (I say one of the ways as there are many other costs on that $10 or whatever, many of them with good justification)

    So by actively changing NZ from a demand limited to free demand approach, then yes, I do believe that the electricity companies are encouraging consumption. Or at least, peak consumption, but perhaps not the total GWH/year.

  25. Ok Trevor and BJ, I’ll play for a moment.

    Lets assume that what works for petrol works for electricity, and you lump a tax onto the price consumers pay, and lets further assume that the total electicity consumed reduces. Thats your plan, right?

    In what way does this need to reduce carbon emissions? There is no direct link between what you and I consume, and how it is generated; we just get electrcity, others make the energy mix (and thus environmental consequence) calculation. So it is entirely conceivable that we may pay more for our electricity, overall less electricity is generated, yet there are more CO2 emissions.

    This is the law of unintended consequences at work.

  26. dbuckley – while electricity may be a “must buy”, how much electricity is the result of a number of decisions. If the price of electricity increases, some consumers will install better insulation and/or double glazing to reduce their consumption. Consumers may also replace resistive heating with heat pumps, and this may include hot water heat pumps. If the electricity price increases more than the price of gas, consumers may switch to gas water and/or space heating. If gas and electricity prices rise, solar water heating becomes more attractive. Consumers may also switch to night rate power when they can. Inefficient appliances may be swapped for more efficient but more expensive appliances.

    To say that the only choice is which power company to use is far from the truth.


  27. Trevor

    You should have quoted the line further on in the article
    “None is in prospect of being built in the near future”.
    These were all farms that they applied for consents long ago and have been working their way through the court process. They also would have had significant carbon credits built into their costings. Often the power companies will take appeals through, even if they are for plant never built, just to stop precedents.
    You are saying that they aren’t being built because of current low prices. So the price of electricity needs to go up to make them viable? This is in contradiction to the NZ Power proposal.

  28. “Other than the windfarm being currently built in the Wellington region, why are no other plant being contemplated?”


    identifies a total of four companies with plans to build wind farms in the Wairarapa.

    The real question is why these plans are not being implemented yet, and the answer has to include low prices for coal and gas generation. If the ETS hadn’t been watered down, some of these wind farms might now be under construction.


  29. I think that for me the principle difficulty is that I understand very thoroughly that the market is good for some things… and is NOT good for quite a few others.

    When someone touts a “market driven solution” as though it were some sort of recommendation of that solution, I cringe. The question of whether the market has the nous to actually choose wisely has to be answered before that can be applied to the solution as a positive or negative recommendation.

  30. DBuckley – I suggest that you examine the experiences of BC and Sweden which actually tried it.




    I was aware of their working, but wasn’t looking hard at details. Only Sweden has really done it hard.

    Electricity is a “must buy” for pretty much every household and corporation.

    How much electricity one buys is to some degree a matter of choice. The demand is not very elastic though (so I do take your point), just as our housing is not very efficient.

    However, the laws of supply and demand were not repealed with respect to electricity. Raising the price DOES reduce demand on the individual level. However, population is increasing and it takes a long time for the electricity demand to respond to the pain. So far we’ve done ourselves a lot of damage with market driven solutions. No sign of sanity in the general population being in evidence the beatings will continue. Self-abuse being the most popular form of abuse in any country.

    Our population is increasing and our “productivity” depends greatly on electrical power availability. We have very little in the way of structured pricing to allow smarter load shifting behaviour. I can time my washing to go at 3 AM, but it doesn’t do me a lick of good on my power bill.

    The reality is that differential changes can’t happen under the current arrangements

    Notice how you just invoked the BAU must continue as is in your tacit assumptions?

    That’s actually a problem for almost everyone. I fall into it myself often enough. There is no experience base for being that far outside the box.

    I don’t actually LIKE the Carbon Tax because it retains too much of the economic trap we are in intact… but I have no doubt at all that the alternatives, from a “small government is best” perspective, will all appear vastly worse.

    Remember, I’m the guy who WANTS to completely nationalize the major power generation in the country and issue money based on our renewable generation capacity. I actually shouldn’t be arguing with you at all 😉

  31. ChrisM – thanks for the additional information. It all gives more food for thought.

    I agree that the best place for new pumped storage is in the North Island, preferably as far north as possible (but not much beyond Whangarei and not too much beyond Auckland). However the cheapest places are not usually the places that would be best for transmission.

    Re Pukaki/Tekapo: It is not necessary to raise the Pukaki end of the canal by a full 20m to get the water to flow the other way. For one, the required gradient is less if the cross sectional area of the canal is larger, which it would be if you raised the water level. Also the flow rate while pumping the water up does not have to be as high as when generating power – we can choose the peak flow rate/power input accordingly. Another option would be to lower the canal floor. However I did ask about the levels when no water was flowing, as it occurred to me that the top of the canal at the Pukaki end might be at the same height as at the Tekapo end, in which case some water could flow back the other way without any canal modifications. One limit would be how low the water could be at the Tekapo end and still be pumped up. As the existing turbines are almost certainly unsuitable for this application, new turbines could be fitted that could handle the lower water level.

    I agree with your comment “Modifying existing plant to meet new and significantly different functions almost never works as well as planned”. The question is whether the result is close to the expectation or falls woefully short. If the project is carefully thought through and there are reasonable margins, modifications can be successful. Certainly at the current prices for new dams and canals, using existing infrastructure is likely to be cheaper than finding a new location and starting from nothing – but only if it works. Therefore some of these ideas are worth a quick look at least.

    Of course one of the cost limits for storing off-peak electricity is the cost of extra intermittent generation. If the storage cost is too high, it will be cheaper to build extra generation and allow the excess off-peak energy to go to waste. However if the price of electricity is high enough the rest of the time, some users will adapt to making use of the cheap or practically free off-peak electricity, i.e. use demand management.

    Having extra renewable generation also allows more spatial diversity, and/or more diversity of types of generation. Both act to even out the generation so there are fewer occasions that generation will be very low or very high, thus reducing pressure on storage systems such as the hydro lakes. However as with most things, the law of diminishing returns applies, and there will still be times that the hydro lakes and other despatchable generation will be required to meet most of the demand. The trick is to ensure that there will be enough water in those lakes at those times – and to have a “Plan B”.


    PS: frequency keeping in the North Island is normally performed by a hydro station. However my understanding is that the thermal stations do much of the ramping to meet demand changes.

  32. Changing BAU so as to avoid more electrical demand is a darned good idea, but it is actually significantly more intrusive and more dependent on government intervention than the tax you wish to avoid imposing.

    A tax we know works.

    You think?

    Electricity prices have been rising since there was electricity, and over the century plus of history we have, there is no evidence that the increase in price per KWh has caused a reduction in demand. If anything, exactly the reverse is true.

    Electricity is a “must buy” for pretty much every household and corporation, and electricity isn’t a capital cost, its a revenue item, paid out of cashflow, be that salary and wages, or revenue stream.

    The only way that a tax works when applied to electricity is for those consumers that can choose where they are getting their electricity from, and given the way that electricity is generated and traded in NZ, no consumer actually has that choice.

    At a wholesale level, the theory would be that a carbon tax would make fossil fuel power more expensive, so less coal and gas, the geothermal is flat out all the time anyway, that leaves hydro. (the rest is so small as to not really count). So we use hydro more preferentially, which I suppose is really good. Right up to we get a dry year, and then we burn fossil, and then our electricity prices all go up.

    The only way a carbon tax can make a change is if it can be used to adjust prices differentially, so option A increases in price whilst option B stays the same (or becomes cheaper). The reality is that differential changes can’t happen under the current arrangements, all that will happen is prices all rise. Consumers get stung. Environment gains, well, nothing.

    So I refute your “A tax we know works” statement when applied to electricity in the strongest possible terms.

  33. there will be increased periods where electricity supply exceeds demand

    We can always dispose of excess electricity. Always. Fan heaters in the multi-megawatt range are widely available, just heat the air. Excess power could be disposed of more usefully, sure. That is just a question, as I’ve noted above, of will, and tariffs. It is not an engineering problem requiring in need of a engineering solution.

    Having said that, to ameliorate frequency instability caused by variable wind, there are now some interesting solutions out there, including grid scale batteries (which i still don’t think are a good idea) and the beacon flywheel system. But a much better idea is to match instantaneous demand to supply using frequency sensitive loads. Again, this isn’t an unsolved engineering problem, just a problem of will and tariff.

  34. Trevor
    I will give only the basics of an explanation. You can google the rest.
    To reverse the flow, you need to raise the headpond end 20m. That will require the movement of millions of cubic metres of material which will need to be dug out of the nearby terrain. The increased pressure is also likely to mean that the canal would need to be lined with plastic. The Tekapo canal has no provision for a spillway so load changes need to be very carefully managed. For most canals, the generation is near baseload with very slow load changes.

    Modifying existing plant to meet new and significantly different functions almost never works as well as planned. Inevitably, it is always cheaper and better to build dedicated plant designed for the purpose. See if you can find a pumped storage plant converted from a power station on a river scheme.

    If you want wind turbines to replace thermal, then the pumped storage needs to be in the North Island, preferably north of Whakamaru. Look up Dinorwig to see what would be needed and thats only 9GWh. Not only is generation needed, there is all the extra transmission lines. Thermal generation provides about 2000MW baseload over the critical periods. The pumped storage needs to provide at least this amount for a five day period – the return period between weather systems. From the windrun and generation data during the recent drought, it would be necessary to cover 10 days if the climate change models are to be believed. There is also the provision of both inertia and frequency keeping, currently provided by thermal plant.

    All of your suggestions will significantly increase the cost of power generation from the modifications needed to existing plants as well as the cost of the new stations. This can’t be reconciled with lowering the cost of generation to below 7c a unit.

  35. ChrisM – sorry I missed your post from yesterday morning until now. It appears to have been stuck in moderation, not for the first time. Do you log in?

    You asked “Currently, it looks like Aviemore and to a lesser extent Waitaki, are used for load following. If they aren’t available, what stations are going to do that job?”

    If the demand is low enough with respect to the generation from intermittents and must-run etc to warrant pumping water back up, then the load following stations will be at their lowest output level. In the case of Aviemore, this could be zero for a while, although for extended periods Aviemore would have to let some water through to stop Waitaki falling too far. Since there are morning and evening demand peaks, this isn’t a problem. Once demand increases (or supply drops), the pumps stop and any further shift back to normal will allow Aviemore and Benmore to restart. Does this answer your question?


  36. ChrisM – I am no longer sure you even understand the problem I am trying to solve. As we try to add renewable sources of electricity generation such as wind, solar, tidal, wave and run-of-river hydro, there will be increased periods where electricity supply exceeds demand – even with as much hydro shut down as practical. Since this is likely to include Benmore and Aviemore being shut down, your comment about the 500MW of Benmore is irrelevant.

    Note that I am aware that Benmore usually controls the South Island grid frequency, so I am aware some changes may be required to allow increased flexibility. And when I say “shut down”, I am referring to water flow. The turbines can still be spinning with the tail water depressed ready to start generating immediately it is required, although if water was being pumped up from Aviemore to Benmore and supply dropped or demand increased, the first reaction would be to reduce the amount of power going to those pumps. As you point out, there is little point in pumping water back up while the generators are running.

    And yes, I realise that both Tekapo A and Tekapo B would need pumping capability if water was to be pumped from Pukaki back to Tekapo. This simply means that this option could accept more power.

    So the only “stupid comment” is based on your recollection of a 10m drop over the length of the canal. What happens when the water isn’t needed and the flow drops to zero?


  37. I totally agree that demand reduction will be part of the mix, but we are arguing about someone ELSE’S BAU. The fantasy that nothing has to change and the IDEA that the cost of things that he sees out there today is the only cost that will actually apply to our actions.

    You know that isn’t true. We can pay that “made up” cost or our grandchildren WILL pay an inescapable cost several times over if we fail to do so. One way or another. Working within the constraints of the system one has to put a price on it that makes it clear what the environment demands.

    Changing BAU so as to avoid more electrical demand is a darned good idea, but it is actually significantly more intrusive and more dependent on government intervention than the tax you wish to avoid imposing.

    A tax we know works.

  38. dbuckley
    I don’t disagree with most of what you say. However, I have my own views on several points. Electricity companies don’t actively promote electricity consumption, though they do benefit from any increase. I think there will continue to be growth in the demand for several reasons. One is the natural increase to match the trends of growing population and smaller households. I believe this would cause about a 3% increase in demand. The other and bigger change is most of the societal changes being promoted to protect the environment are for increased electrification. These include items like electric cars, electrification of the rail system and promoting heat pumps to replace fireplaces. Airconditioning in offices to remove the heat from electronic goods like computers is now near essential, where it used to be gas fired boilers for the radiators to warm them up. The demand from electrical appliances is still growing and despite all the promotions, people still leave them on standby. I also believe that there is research out there showing that when families change their heating source from something like radiant heaters to heat pumps, they don’t change their electricity consumption much, but live in a warmer environment. Pricing does seem to be the major driver of demand, even though it also causes fuel poverty. My albeit anecdotal impression is that the younger generation is a lot worse than their parents. I don’t think education campaigns to switch off have much effect so I don’t know how to bring about the change.
    O&M of stations has got a lot more expensive over the last 20 years. Compliance with regulations and the market requirements are now a major cost. Also consent renewal and even compliance with existing consents is very expensive.
    New stations are invariably more expensive than the generation they replace. The best sources were rightly used first. The civil works now have to be built to a lot tougher standards and the grid connection requirements are a lot more complex. All of these may well be of immense benefit, but they add to the cost.

  39. Add an effective cost of $150 a ton of CO2 emitted and what is THEN most “cost effective”?

    But that cost isn’t a real cost; its a made up cost, with no basis in reality, applied, basically, just because you can. We, as a nation, can choose to apply that cost, or not to apply that cost. If we, as a nation, choose to apply that cost, then you and I just get to pay it out of our pockets. It doesn’t actually change anything.

    Back to reality: the most cost effective form of electrical generation is avoidance, and if we wanted to, we could just be a more efficient nation, and thus generate less. But that isn’t going to happen when you have an electricity industry that is measured on how much money it generates, either for the government, or for shareholders, that really doesn’t matter a jot.

    We actually have enough generation, and a decent enough mix that actually works, even if it isn’t optimal from any of financial, engineering or environmental perspectives. Avoidance can remove the need to increase or generating stock. But not the need to replace rotting plant, I agree.

  40. It is only the most “cost effective” option when the long term costs are irresponsibly and irrationally discounted. Add an effective cost of $150 a ton of CO2 emitted and what is THEN most “cost effective”?

    You apparently don’t believe those costs exist so you are apparently willing to build coal powered plants. Which 98 out of 100 scientists, who actually KNOW what they are talking about, will refuse to countenance. This is basically hubris on your part.

    You know that the science is there and you are rejecting it, but your expertise in one place is NOT carried over to climate science.

    Your motivation in trying to hold up the BAU model as the one that has to be adopted is unknown to us. What we know is that it is entirely broken and cannot be sustained. Not that “we don’t want to sustain it” but it CANNOT be sustained.

    That the end result will alter the environment our civilization relies on so severely that we potentially could be reduced to scattered bands and tribes of hunter-gatherers with legends of a former greatness, and ruins full of objects we don’t even understand. That is, after the dead bodies are cleared away somehow.

    Which makes your advocacy of BAU a bit foolish here, no matter how smart you THINK you are.

    NZ has to manage on the power it has. There will be none available for import. It has to manage without just digging stuff out of the ground to burn, as burning THAT has a cost our children have to pay.

    You offer us BAU and we are telling you that BAU is the road to hell. Thanks, but no thanks.

  41. Trevor, if you don’t want me to make caustic flames, don’t make stupid comments. The canal between the tailrace of Tekapo A and the penstock entrances of Tekapo B has a slope on it to match the hydraulic gradient at full flow. From memory, it is about a 10m drop. Also the canal starts at the tailrace of Tekapo A. so that needs reversing as well.

    Oh and by the way, your grand scheme for using Aviemore water means Benmore can’t be used for generation so that takes 500MW off the grid. Or do you plan to generate and pump at the same time.

    The reason why BAU is there, is because it works and is generally the most cost effective option. It isn’t perfect, but most of the limitations are there because of societal onstraints. This is why there has been rapid adviances in areas like NDT or monitoring systems. If someone comes up with a good idea, it will rapidly get adopted. Unfortunately almost all of the proposals, even if practical (which most aren’t), fail even the simplest cost benefit analysis.

  42. “So Aviemore ain’t anywhere near big enough and that was the only viable existing lake.”

    And we can’t consider Tekapo/Pukaki because there is a canal linking them and we would have to pump water back up the canal. End of discussion.

    ChrisM – you will need to explain just why it is impossible to pump water along a canal before ruling out using most of the Waitaki scheme for pumped storage. You say we need 500GWh, without giving a basis for this fugure. Tekapo and Pukaki store much more than this each, yet you dismiss them just because there are canals involved?

    I haven’t heard a constructive idea from you yet. Do you have a vested interest in Business As Usual?


  43. I misunderstood your original plan. Pumping from Aviemore up to Benmore increases the value of all of the Aviemore water to 3GWh. The minimum flow out of Waitaki is also only 150cumec. The Green Party among other were objectors to lowering it to 110 cumecs. However the gist of the rest of my comments still hold.
    Currently, it looks like Aviemore and to a lesser extent Waitaki, are used for load following. If they aren’t available, what stations are going to do that job.

    At present, LNG can come out of the US is very cheap and they haven’t even touched the big resources there or under Europe. That is why all those plants in PNG and Australia are running into financial difficulty. Anyway, who says we need to import LNG. There is plenty of shales under NZ to fracc and there is the coal in both the Te Kawhata, Aria and Benneydale areas that could feed a replacement Huntlys. The plans are still in the NZE folder.

    Other than the windfarm being currently built in the Wellington region, why are no other plant being contemplated? Could it be that there are no longer Labour appointees on the SOE boards? A lot of the farms got built with carbon credits from the EU. Now they have collapsed in price, they aren’t economic. Several companies have even let their rights lapse. No-one wants the birdchoppers, other than a few advocates who like to feel holier than thou without any understanding.

  44. ChrisM – we finally agree on something, even if it is only the meaning of an acronym. Now let me see if I can agree with anything else you said…

    “Aviemore is 7.44GWh/1000CMD.”

    You said earlier that Aviemore was 199CMD, so I take it this is the storage. So the 7.44GWh/1000CMD must be its peak output power/flow rate assuming 24 hour operation. Or 310MW at 1000 cumecs. This is in agreement with the head of around 38m and an efficiency around 80%.

    Of course the idea that I am suggesting is to pump water from Aviemore up into Benmore, not from Waitaki into Aviemore, so your figures are irrelevant. Benmore’s head is around 90m, giving much more energy per CMD.

    Benmore is a major transmission node, so a lot of power comes into Benmore and goes out. Why would the transmission equipment need a massive capital investment to support this idea? Transformers and cables don’t care which way the current flows.

    And as I pointed out a long time ago, it isn’t Green Party members who are making the decisions in the generation companies to install wind generation. These decisions are taken by top managers, and if the wind farms are uneconomical, they would be out of a job. Instead, they install more. This tells me that the people who actually have the real cost data believe that the wind generation is NOT too expensive to stand alone.

    What price will LNG be if we have to import it to run the North Island thermal stations when our CNG resources run down? How reliable will that supply chain be when Japan and other countries also want LNG?


  45. Trevor
    You are right. I didn’t put the full text down, just what the letters of the acronym meant. It is Cubic Metre per second for a Day. But even your very simple analysis isn’t there. The water takes a real time to flow from one dam to the next. In the case of Aviemore, it is quite short – about 20 minutes either way so we can say it’s instantaneous. This isn’t the case for the North Island though where the storage would need to be.

    Aviemore is 7.44GWh/1000CMD. Taking the losses of pumping into account it drops to about 6GWh/1000CMD. To be anything effective on the system as pumped storage, it needs to be probably at least 10GWh. To replace thermal by wind/solar, there needs to be 500GWh. So Aviemore ain’t anywhere near big enough and that was the only viable existing lake.

    You also waste a lot of power pumping it up to a higher lake so the value of the generation while pumping would need to drop. If there is no thermal generation on in the must run, then the is no low nighttime prices. They just hold water back. There is also the massive capital investment to change the station, the transmission and protection equipment. And for what? To support a generation method that is too expensive and undispatchable to stand alone. Yeah Right.

  46. One other note Chris… an idea is not in the same category as a proper project plan. You seem to want any idea from anyone to be fully analyzed and feasible before it is mentioned here.

    With all due respect, you need to cool your jets. The FIRST step is to discuss the ideas and work out whether they make sense. Discuss. That means talking it through with others, some of whom will know reasons why those ideas aren’t practical to SOME problems and some of whom will THINK they know why, but will be discussing different problems. The discussion is apt to get a bit human and messy.

    Insisting on the conditions you are insisting on before presenting an idea for discussion is an excellent way to stifle innovation and prevent progress… doing things that we KNOW will work all the time and ridiculing new ideas is not productive for the society as a whole.

  47. ChrisM – I get the distinct impression you don’t even know what the units are of the figures you are quoting! CMD doesn’t make sense as cubic metre days either. However cumec days makes more sense, where a cumec is one cubic metre per second, making a cumec day equal to a volume of 86,400 cubic metres, i.e. the volume of water that would flow in one day at a rate of 1 cubic metre per second.

    I can work with that.

    If the flow out from Lake Waitaki needs to be 200 cumecs, and we want to pump water up from Aviemore into Benmore, and both Aviemore and Waitake start out full, we would need to let water flow from Aviemore into Waitaki after 0.71 days, i.e. 17 hours. But the nighttime trough in demand is only 6-8 hours. This could allow us to store some night-time wind/wave/tidal generation for morning or evening use.


  48. Yes Chris, and if you keep coming up with ignorant and sophist arguments relating to what is happening to the planet you will also be flamed.

    There’s really no need though. In some deep engineering ways where your expertise lies you can always find things that non-engineers might get wrong, but in the doing you betray both your own ignorance of everything ELSE and your sorry lack of any ability to get along with other people.

    Sheldon has nothing on you.

    Pumping water back up-river would need rather a lot more pipe than I’d imagine I want to invest in, and the simpler answer of closing down flow to the minimum needed to keep the river flow above its minimum, so as to accumulate power behind the dams, would be a lot more efficient as long as the dams had unfilled capacity.

  49. Trevor

    You are right. CMD is a cubic metre day. Probably the standard unit of storage in a lake in flow units.
    I have in a previous blog posting on Frogblog given the requirements for calculating storage needed for pumped storage schemes. However, it is simple enough from first principles using the energy equations. In those previous exchanges, I also gave the costs using industry data.

    If you keep coming up with uncosted or impractical ideas, you will continue to get flamed.

  50. ChrisM – what the f*** is CMD? I tried Google and the closest I could find is cubic metres per day, which doesn’t square with your numbers. There are a number of other definitions of CMD, but they don’t make sense here either. Please don’t use industry-specific abbreviations without giving their meaning – or have you slipped 6 orders of magnitude?

    You have access to more details than I have, so it makes it harder for me to find the numbers to do the calculations. But believe me, I can use a calculator and I do know how to make the calculations. I also know that to reduce pH, you add acid, i.e. a reduction in pH is acidification, whether or not the solution is basic (pun intended).

    You like rubbishing people don’t you? However you don’t like actually answering the questions, such as how much would it cost?

    “I covered in an earlier post just how big any useful pumped storage needs to be.”
    …but you didn’t bother saying where these numbers came from, or what your assumptions were.


  51. If the oceans are predicted to drop to a pH of more than 7.5 even at 1000ppm CO2, that doesn’t make them acid.

    No… it makes them comparatively MORE acid. That is what “acidification” means. It will eventually bring the pH to the definition of actual “acid”.

    Comparatively worse for living things that have evolved in the LESS acid environment that has existed for the past what…. 3 million years?

  52. Wind needs to be under the same rules as everyone else.

    OK… if you insist, but the way THAT works is everyone else works on the same basis as wind. Intermittent… and we all get used to it. /sarc

    You don’t impose rules on reality. You work with and negotiate with reality. You of ALL people have to know that.

    You keep on making assumptions about BAU being the only way to play the game and the fact is that BAU is the single guaranteed to lose strategy for playing this particular game.

  53. Take away the latter and no-one will build any new plant unless they get a guaranteed higher price.

    Government too? Really?

  54. Trevor

    You really have no idea, do you! Please actually try to do some calculations before you fire off your missives.

    I covered in an earlier post just how big any useful pumped storage needs to be. Even for the tiny (and effectively useless) scheme you are now advocating, the lakes on the Waikato are very small storage. The biggest is Maraetai at just under 12GWh. If the water is pumped back up, where is the water going to come from to keep Karapiro discharging? Aviemore is 199CMD and Waitakei 142CMD. If the minimum flow is supposed to be about 200cumecs, where is the water to fill Benmore coming from? Much of the rest of the generation on the Waitaki comes from canals – going to reverse those, are you? To turn generators into pumped storage systems costs a lot of money – no doubt from the cheaper power to consumers pot- and it also needs new consents which everyone then objects to.

    And if you want to slag off with ad homs about my supposed views, rather than acknowledge your mistakes, you could at least get your facts right. If the oceans are predicted to drop to a pH of more than 7.5 even at 1000ppm CO2, that doesn’t make them acid. Or is even basic chemistry beyond you as well?

  55. “Most (New Zealanders) seem not to want a unreliable yet very expensive all renewable system…”

    and we agree totally with this. However there may be ways of increasing the proportion of renewable electricity generation that do not degrade the reliability or add significantly to the cost. With your knowledge and intellect, why don’t you humour us and help us to find some of these ways, whether or not you believe in AGW or ocean acidification or Peak Oil.

    For example, if as you say the stations on the Waikato river (like those on the Waitaki) are largely discharging into the next station’s lake, is it feasible to enhance these stations to be able to pump the water from the lower lake back up into the higher lake at times when there is surplus generation? If not, can you explain why not. If this is feasible, have you any idea of the cost or how much power could be stored this way?


  56. bjchip
    They already integrate intermittent generation into the grid. Run of the river being the easiest that you would understand. Wind needs to be under the same rules as everyone else. It can be dispatchable. Just means that the windfarm or solar plant owner needs to make up generation from other plant in its portfolio or its own embedded storage to meet its bid. Then it isn’t subsidised by either the other generators or the consumer.

    Lowering the cost to the consumer but pushing for more expensive generation (either wind farms or carbon tax) is squaring the circle. Reliable generation is paid about $70/MWh average by the market. The cheapest new generation is about $120/MWh. At present, the generators subsidise new and replacement plant from the “profits” on their existing. Take away the latter and no-one will build any new plant unless they get a guaranteed higher price. And unless they have hidden it very well, there has been no detail on how the system will work with comparative pricing – only arm waving and Tee-shirt slogans.

    Generation information generally has to be dumbed down for the masses into things they understand, albeit incorrectly – as you proved. The hydro is mainly their massive projects like Three Gorges. I though the Greens were against big dams. The percentage of production of renewable is increasing (it is coming of a very low base so any number looks big) but the Chinese government is putting most of its resources into new coal burners. Those are the things they are buying with hard foreign exchange. They are not replacing coal with renewables, just building a bit less new coal. By 2015, they will emit more CO2 than USA and UK combined and India will probably be #2. Makes anything NZ does like farting in the wind, or is it being totally symbolic that you are into?

    The links open OK for me. Maybe the Chinese secret police have you on their black list;). They are building transmission lines as well as the new generation to the outer provinces:
    The second and third of these links is about a line mainly there to access a massive coal resources with a bit of renewables chucked in to appease the environmentalists who don’t understand details.

  57. The rest of the industry has to, so why should wind get a free pass?

    There are inherent assumptions in your question that need to be understood.

    Fundamentally you are asserting that intermittent sources of energy should be IGNORED because they are intermittent. Trevor was pointing out how they should be INTEGRATED with existing sources.

    We don’t see things that way Chris. Energy is valuable even when it is intermittent. Even more valuable if we have storage for it, but we need to find ways to make use of it when it IS there, and to conserve other resources and use them in the times when the less reliable isn’t there.

    The NZ Power proposal was to lower the price of generation

    The proposal was to lower the price TO THE CONSUMER. The details of generation costs are a subtly different matter. There is no particular urge on our part to foster unreliable power. We want RENEWABLE power, and that is more expensive to build reliable or requires adaption of demand. The contradiction only exists if one excludes the role of government and assumes something like the BAU we currently have.

    Moreover, the last time we had this much CO2 in the atmosphere the sea level did indeed go 10 meters higher. Which is what Kerry said.

    I believe you misunderstood intentionally to make insult from it, but even if not, your response shows us exactly why we doubt you outside your field of expertise.

    The sea level rise is accelerating. If it gets to where that becomes noticeable it is already way too late to stop. Right now the rate of rise is showing some seriously increased variability.


    I don’t think this is a “good” sign. Nor is there any doubt at all that the IPCC is underestimating the rise.



    Lets go over the bottom line again here.

    BAU is dead. It CANNOT continue, and the only questions that need to be answered are how much renewable we can build and how much we have to adjust to not having the power always available at the flick of a switch.

    Doing it the old way is not an option. Just because it is CURRENTLY cheaper doesn’t make it less costly overall.


  58. ChrisM – you provided the Chinese power capacity charts to prove your point and now you are saying that what they show is misleading. So why supply them?

    However unless the capacity factors have changed, the charts show a bigger increase in wind, solar and hydro generation as a percentage – how can it be otherwise? A 7 times increase in solar installed capacity is always going to give around a 7 times increase in solar generated power, not a 40% increase.

    And China are also building some new transmission lines – big ones. I recall a 1MV 5GW line hitting the news a while back. And there are others.


    PS: I couldn’t make sense of that urumqi link. It seems to have been translated by computer.

  59. Also Trevor, you don’t seem to understand where China is building its renewables. Most are out on the western arc, beyond the range of their grid and with no easy other energy source available. It is all part of the rural/remote electrification projects.

    New Zealand does have the choice. Most seem not to want a unreliable yet very expensive all renewable system and the justifications put forward for changing have been dodgy at best.

  60. Trevor29

    I thought you were bright enough to realise the difference between installed MW and production. I was wrong. Multiply the data by their load factor – it gives a totally different picture.

    The major reason why the Chinese do wind and solar seems to be to give their local industries a market base. However, their QA is still very variable so they aren’t selling. That’s why there are all those solar cell failures after 3 years – not a great capital investment!. The overseas market, mainly subsidised by the EU, collapsed so they are now trying to absorb the glut without much success. Look at the output from some of their plants – way under design because of the unreliability.

    The MW produced by the last hydros on the main hydro rivers (Waikato Waitaki, Clutha, Rangitaiki) at minimum flows is quite low – less than 200MW. The intermediate dams also have low minimum flows as almost all except Aratiatia discharge into the next dam’s lake. To that has to be added the run of the river schemes and the CHP plants. Must run is generally dominated by the big thermal units – about 200MW each for the CCGTs and 100MW for each Huntly steamer. They are needed, even in Denmark, to provide grid inertia, generation close to load centres and back up power because wind is so unreliable.

  61. “…the production percentage from the various sources is staying about constant…”

    Wind 45/1053 => 100/1475 is an increase from 4.3% to 6.8% in just 4 years – hardly constant.

    Solar increases by a factor of 7 as the total increases by just 40% – a massive scaling up.

    Coal drops from just under 70% to just over 63% – slipping more than 6% in just 4 years.

    To me, China seems to be ramping up their renewables as quickly as practical, but because renewables have started from a low level, it takes time to ramp up to a level that allows the non-renewables to be reduced.

    New Zealand doesn’t have that excuse when it comes to hydro or geothermal, and we should be able to ramp up our use of wind faster than we are doing.


    PS: I may have picked the wrong dam when I mentioned minimum flow. (It was late.) However Waitaki will be one and Roxburgh will be another, and several of the Waikato River stations will also have minimum flow requirements.

  62. Trevor

    China might be installing some renewables but the are installing a lot more coal burners. This site here indicates that the production percentage from the various sources is staying about constant despite the 50% increase.
    And I don’t see much sign of India doing anything other than token Greenism here:

    And you are correct that you included all the renewables. However, the must run on the hydros is very little and only applicable to a few dams – as Clyde discharges into Lake Roxburgh, I don’t even know if it has a minimum flow. It is generally in floods that they spill water because of no demand for generation. And your post then talked (as did your 4th post)about two shifting geothermal supporting the intermittents not the must runs.

  63. ChrisM said: “However the very first comment was about not running geothermal to accomodate wind generation.”

    If you re-read my post, you will see that it mentions “wind and other intermittent or must-run generation”, i.e. it includes solar, tidal, wave, run-of-river and even full hydro with storage like the Clyde dam – systems that have a minimum river flow even though they are despatchable.


  64. ChrisM said:
    “That is why their power prices are so high and their energy intensive industries are moving to Asia where the coal burning power stations are being built.”

    And which countries are installing the greatest amount of wind and solar generation? Asian countries are around the top of that list.


  65. Kerry

    You are a joke. When the information matches your prejudices, you demand that they follow the science predictions. Even demanding an enquiry. When it doesn’t give the result you want, you discredit it as part of some great rightwing conspiracy. Think fraccing or GE.
    Disregard predictions. The actual data on sea level is here:
    with trends here:
    It is still on track for the mid range of the original IPCC predictions done way back in 1988

  66. Yeah right CM. As the IPCC reports have been shown to be overly optimistic, so far, and the last time sea level was 10m higher, atmospheric CO2 was at 400ppm, AND we are showing no signs of stopping at 400ppm. 10m is not exactly out of the range of probability with our current rate of rise in green house gas production.

    As for wind strengths, at the time I wrote the above I was looking at the now-casts from ships, lighthouses etc. The wind was over 10knots where we were, by the way. My planet is the real one, where we do weather reports 4 hourly.

  67. bjchip

    You are right that the headline post was about geothermal. However the very first comment was about not running geothermal to accomodate wind generation. I.e. subsidise it. Same with pumped storage.
    The point I was making about wind (which is now up to 218MW is that it is not dispatchable – IT IS NOT RELIABLE. If you think it is, tell me how much electricity (to withing 5MW)it will be generating in 22 hours time. The rest of the industry has to, so why should wind get a free pass? One has to run back up plant to support the unreliable wind, which also are another subsidy.
    The Eupropean experience is that the windfarm owners make more money out of the credits and subsidies than they do from actually selling the generation at market rates. They were in the ridiculous position of being paid not to generate! That is why their power prices are so high and their energy intensive industries are moving to Asia where the coal burning power stations are being built. The high power and energy prices are also why fuel poverty has become a big issue.
    The NZ Power proposal was to lower the price of generation (which is only 40% of the power price) yet all the Green’s policies are to promote generation that is not reliable and more expensive than what it replaces. Can you not see the contradiction?

  68. Careful Chrism, your ideological blinders are showing you nothing….

    Like what Key really is…


    Don’t you think the best option for NZ consumers is just to keep the current system.

    No. Your problem, now reading some of the OTHER posts you present, is that the full cost of things is not anywhere in your analysis. You can look where you like and as long as CO2 and its damage is not costed the fossil resources seem cheap. This will be the case until the price changes enough due to scarcity that it cripples the BAU rapists.

    However, Mother Earth won’t put up with it. She’s going to kick the wingnuts in the balls.

    Germany has a more ideologically driven “Green” movement. They closed their nuclear plants – and wound up shooting themselves in the foot. The Danes did their target practice in 1985 when they outlawed nuclear energy. The energy resources in that area are such that the only way to support their population in the mid-term would be nuclear.

    Nor is there a claim anywhere that “wind is so good” that it stands alone as an energy source. To make it do THAT one has to have serious energy storage of some sort, and Solar at those latitudes and climates is a seasonally available luxury. The Danes need to work with tidal flow through the straits and they need to start building and researching energy storage, not CCS.

    The Danes did close Enstedvaerket-3 but are still driven by profit in a world where coal and oil are subsidized heavily simply by the fact that there is no tax on CO2.

    As for the generation here, nobody has ever claimed wind is “reliable” on its own. So you are building more men of straw. Wind is generating NOW… pick a moment and one can find less or more…


    The thing is that wind comes in 3 flavors for the turbines. Too much, not enough and just-right. Much like the 3 bears of the story. As the turbine designs improve they’ll work better in the higher wind velocities, but for NZ something else might work better.


    Comparing mature tech to new is not reasonable either. What uses is a baby?

    …but the NZ availability is higher than almost anywhere on the planet, and IF some of my peers suffer from myopia about pristine views and not building on ridgelines I don’t have that problem, and I am sure we could double the capacity factor by being a bit more clever still…


    Of course, this thread WAS about geothermal.

    There is near no efficiency gains compared to using air in NZ.

    That’s true on average but in the nasty part of winter when the humidity is high and the temperature just at freezing, the pumps suffer from icing and THAT pulls efficiency way down. Which isn’t something that happens to the non-air heat pumps.

    You do have a way of looking only at the things you want to see.

  69. Kerry
    And what’s all this about a sealevel rise of 10m by 2100 from AGW. That is just so last century. Haven’t you been following the story? It has now morphed into Climate Disruption or Extreme Weather.
    And you are definitely not part of the consensus. AR5 Chapter 13 says:
    “It is very likely that the rate of global mean sea level rise during the 21st century will exceed the rate observed during 1971–2010 for all RCP scenarios. For the period 2081 to 2100, compared to 1986 to 2005, global mean sea level rise is likely to be in the range 0.29–0.55 m for RCP2.6, 0.36–0.63 m for RCP4.5, 0.37–0.64 m for RCP6.0, and 0.48–0.82 m (0.56–0.96 m by 2100 with a rate of rise 8–15 mm yr–1 over the last decade of the 21st century) for RCP8.5.”
    remembering that likely means only greater than 50%

  70. Kerry, don’t worry your salvation is at hand. The wind generation is now up to 2MW. And I don’t know which planet you are beaming in from, but the Met Service shows the only places in the country at noon with wind speed over 5 knots are Akaroa and Stewart Island. Though no doubt, they are part of the great conspiracy as well. Maybe, Big Oil is paying them off.

  71. What are you trying to say?

    The oil industry is NOT subsidised? Pull the other leg.

    Wind could be producing most, if not all, of our power right now. Given the present wind strength on the West coast.

  72. By the way wind is so reliable that right now, of the 5746MW being consumed in NZ, wind is producing 0MW. Way to go.

  73. Careful Kerry, your tinfoil hat is in view. I’m certain you know where Elvis is living in retirement as well.

  74. Therein lies one of our problems. A lot of less than environmentally and/or socially optimal solutions are ignored because subsidies to vested interests, and the worship of “the market” make them less economically viable.

    Worship of the “free market” and “free trade” resulting in importing cheap substandard Chinese solar panels which killed research in the USA and Europe into more efficient solar power.

    Oil industry subsidies, including regime changes to keep US pump prices down, make alternatives less easy to market.

    Subsidies to the trucking industry, a big contributor to National by the way, in New Zealand, and the so called “open coast” a license to kill for companies like Mearsk, stop coastal shipping getting off the ground and make rail look nonviable.

    Wind and solar, and many other environmentally sound solutions, look more expensive, but if they were subsidised to anything like the extent that fossil fuels are, or even if we simply stopped subsidising polluters and green house gas emitters, the balance changes.

    Not to mention that, importing fossil fuels, adds about a billion a year to our current account deficit and hence our cumulative interest bill.

  75. You forgot to add in the extra costs of frac gas. Like the sea level rising 10 metres by 2100.

    Makes solar and wind a lot cheaper.

    You are also ignoring the costs of all the subsidies to the fossil fuel industry. Don’t forget every war fought by Western countries since WW2 was over oil. That has cost a bit also.

  76. Kerry Thomas

    I think you also have forgotten to put the sarc tag on

    Solar installation costs have only come down because the Chinese are dumping panels on the market from their overproduction. They are still a lot more expensive than fracc gas through a CCGT which is about 4c/unit, inclusive of capital cost. They are also finding the new solar panels are lasting 2-3 years.

    If wind is so good, why haven’t the Danes decommissioned any of their coal fired power stations? Why is their domestic power the most expensive in Europe. Why is Germany rapidly building more lignite burners? Why is Britain backpedalling on there renewable options now they realise that clearfelling forests to feed Drax maybe isn’t a good idea.

    That isn’t hysteria, it is just the real world that a lot of people don’t seem to be able to cope with.

  77. Caught by the editor again.

    Meant 100% renewable ELECTRICITY generation.

    100% Renewable for transport is a long way off, if ever.

    However we can go a long way with the use of electricity for urban transport, bioenergy from our waste streams, energy use reduction, such as building insulation and smarter transport, direct heat from waste and solar, wind and tidal power, and smaller scale hydro.

    There is no one answer, but NZ is well provided with alternative energy sources. And opportunities to reduce energy use.

  78. “Unreliable and expensive wind”.

    Not the experience of those who have tried it.

    Even solar costs are getting down towards those of oil and gas generation.

    100% renewables is not an unreasonable goal, and likely to be much cheaper in the long run, as the USA cannot push down the price, of ever more expensive to extract hydrocarbons, forever.

    Methinks, I see another example of hysterical reaction from power company types, who see their anticipated gains from ripping off New Zealanders, being taken off them.

  79. I know about the proposed pumped storage system that was going to be in the hills above the Clutha. The costs of that system were eyewatering and it didn’t include transmission. All just to support unreliable and expensive wind.
    Don’t you think the best option for NZ consumers is just to keep the current system. NZ Power was supposed to lower costs to the householder wasn’t it. All the suggestions so far has just been making it a lot more expensive.

  80. ChrisM asked me “And did you ever calculate how big a lake you need? It needs to be about the size of Lake Taupo, 300m above it lower reservoir with a 3 metre working range.”

    No, but I know somebody who has done some calculations on a pumped storage system that could hold even more than that. How does 10,000GWH sound? That would more than triple our current hydro power storage. The only snag is that it would be in the South Island.


  81. Trevor

    You have never worked regular nightshifts, have you. Most operators are on 12 hour shifts, they generally only do two nights in a row before going on days for a couple then they have their “weekend”. Any more nightshifts than that destroys their life. That means you need a lot more operators than you think. And no, it isn’t something that is economic to bring someone semi-skilled in for. If they are operators, they need to be able to all the tasks, not just an edited set.

    Poihipi Road only ran that way because they were consent constrained and they were trying to maximise income. This was especially so when Vector ran it (at a loss). They would have run baseload if they could. The station also was originally running on dry steam wells. Those wells are now near dead and the station is mainly supplied by liquid feeders working through flashplants.

    Running geothermal steam turbines off their fully open position is quite inefficient. It also causes significant wear on components like valves and turbine blades. The machines also need to be gagged so they don’t respond to grid underfrequency. So not only is income down, but maintenance costs go up (running at low part load can stuff a set of turbine blades within a month and they cost a telephone number to buy replacements, plus take months of outage time to fit them).

    Even if they are present,ramping dry steam wells up and down causes all the gases that accumulate in the steam play havoc with condenser vacuum and efficiency. Liquid feed wells don’t take kindly to being throttled. They also can be quite destructive to plant with a slugging flow regime which often occurs at low flows. As they generally need to be controlled at the wellhead or flashplant, that requires two people for safety reasons, especially in the middle of the night. This staffing would be in addition to the one in the control room. Remote sensing gives nowhere near the information a good operator doing a walkdown does. There are many nights when the price doesn’t drop, and it often goes down in the middle of the day.If you take today as an example, the power price troughed to the same level about 4am and 3pm. Stations do occasionally get constrained off because of grid or consent reasons. Then they usually put the station to the vents while they bring in operators to either close the plant down, or bring it back up to full load when the constraint is lifted.

    The costs and benefits of different generation regimes are regularly examined, and baseload is always the best by a very large margin. If the system wants them to support wind, then wind needs to pay for that. It will make electricity even more expensive.

  82. ChrisM – I apologise for misinterpreting what you wrote. I am used to people referring to a position as a position for one individual, rather than for 4.3 individuals.

    If a hypothetical geothermal power station is run at full output except for 4 hours per night, and is ramped down over 2 hours and ramped back up over another 2 hours, one shift of operators would need to know how to do this and be manned to the required level. This would cost $100k+ per position required, not $500k. If multiple operators were required to perform this process, I can see that it makes sense to have at least 2 operators on with the necessary training, with enough operators in the operator pool trained to this level to allow for holidays, etc. However I don’t see that all the operators would need to be fully trained to this level to perform all of the necessary supervision, checks, etc. If it requires that much manpower, then there may be a case for remote sensing and/or remote control which might not be justified if the plants don’t vary their output.


  83. ChrisM – I don’t have to – you already did it for me:
    “Poihipi Road was two shifted early on because they had consent constraints, but that stopped years ago when Contact built a pipeline from Wairakei to supply it.”

    It ran for years that way. Do you know of a reason why it couldn’t be run that way again?


  84. Scamp

    With your comment about your drilling experience, you left off the /sarc tag.

    They couldn’t drill 4knm wells 30 years ago. However in 1988, a 1500m well cost about $1M and power was about 8c / unit. The 50% is industry average for production wells within a known resource – read it in the literature. For exploration, it is a lot closer to oil industry averages.

    In Rotorua, they closed a lot of downhole heat exchangers within the 1.5km so those wells weren’t doing any mass withdrawal. The policy enacted by the government of the time went against DSIR advice. I had an interest at the time, having worked for the taskforce. By co-incidence,I was on the same flight to Wellington from Rotorua as the Minister after he made the public announcement. Mr Butcher sneaked onto the plane and kept his head down until halfway back. I gather it was a pretty fiery time at the meeting.

  85. Trevor
    You keep on harping on about turning down geothermal and that you know one is suitable. However, you continue to do a Winston Peters, and never reveal your knowledge. Please tell us which one it is.

  86. ChrisM.
    – $25M wow. How much did it to cost to drill wells relative to the price of a KWh in say 1980?
    – 50% sounds bad. Which wells are you referring to?
    – Practical experience … I have an auger
    – You are right, down hole heat exchangers don’t usually have a mass loss. That is the extreme I was referring to.
    – Correct. In Rotorua those within the 1.5Km zone were shut. The ones around me kept working and many still are. The government encouraged heat withdrawal from the groundwater flowing to the lake. The discouragement was for mass withdrawal within any 2-phase zones.
    – Yes, Ground source heat pumps are also good in hot climates. Starting to sell well in Aus. In fact they work anyway that there is a heat difference.
    – DSIR and MOW were gutted or sold 20-30 years ago. So what’s your point?

  87. dbuckley – agreed, but if there is enough supply in the wee hours, the tariff might need to be pretty low to get enough demand. Reducing the output of the geothermal plants would help, which in turn would encourage more renewable generation to be added knowing that there would be a market for their output most of the time.

    However good demand management would also help. An obvious candidate (but not necessarily the best one to start with) is hydrogen generation for the ammonia/urea plant or for the oil refinery.

    Pumped storage would also help balance supply and demand.


  88. Trevor29:

    For a few hours early each morning, electricity demand drops and spot prices for electricity drop also, more so in summer, and sometimes even to zero, as must-run and intermittent power generation exceeds demand

    You are trying to address this as an engineering problem, and the simple fact is that it isn’t.

    The only reason supply exceeds demand is not that there is excess supply, but insufficient demand. This is a trivial economics problem, if that electricity was available at the correct tariff, then there would be a market for it.

    If the electricity industry was run by engineers, thats exactly what would happen. But it isn’t, its run by business people, and they see every KWh of electicity sold cheaply as KWh of electricity they cant sell at a higher price some other time. And, of course, they are right.

  89. Trevor
    Your also justify your beliefs with the statement:
    “when New Zealand is heading towards 90% or more of its electricity generation from renewable resources. How can we meet peak demands with little or no use of fossil fuels? You are arguing the economics of my suggestion based on Business As Usual (BAU), but BAU will lead to a global catastrophe.”

    There are just so many assumptions in here. Who says BAU on the NZ scale will lead to global catastrophe? Not the 97%, I hope. We have no impact on the world’s emissions and most of ours was supposed to be methane, for which atmospheric concentrations have near stabilised despite all our extra cows. The moral high ground is pretty cold comfort when the lights go out. China and India make a few soothing noises but are still building coal burning power stations flat out. Even Germany has resumed building Lignite powered stations.
    We can easily meet the 90% by damming more rivers, but the Greens are against that, except when it is pumped storage to support wind. And did you ever calculate how big a lake you need? It needs to be about the size of Lake Taupo, 300m above it lower reservoir with a 3 metre working range. As I have stated before, there is almost no geothermal left, except in protected fields. The Greens are also saying they are going to lower electricity prices to the consumer and at the same time as reducing consumption of fossil fuels by converting more transport and the like to electric. That lower prices cannot be reconciled with all the new generation that will need to be built just to replace thermal, let alone meet added demand. I note that last night, wind provided next to no generation when it was needed. Today was a little better. It will also need the new transmission lines and power storage systems that will have to support them.
    All we get is armwaving and assurances that there is a realistic plan. I can’t find anywhere actual details of how the cheaper power prices will work using the data from the last 10 years. Even Think Big actually published the real numbers.

  90. Trevor29
    Earlier you accused me of not reading what you wrote. Please do the same. To cover one position on a 24/7 basis takes 4.3 operators. Each one gets about $100k plus incidentals. Operators take about 5 years to fully train after their trade qualification. They aren’t the downtrodden masses anymore and even at that pay, we lose them to overseas. It is why so many of them vote National or ACT as well as belong to the union.

    You are yet again demonstating abysmal ignorance about how plant actually works. Bringing load up and down is a lot more than just pushing a button. There are flows to change, plant & pumps to start/ stop and a lot of kit that needs monitoring during the changes. It also needs regular walkdowns. In the power station environment, expert systems actually means systems for experts.

    You are right about not all fields are suitable for this. The ones in NZ that are actually suitable number zero.

  91. ChrisM – I am thinking about longer times frames than you appear to be discussing, when New Zealand is heading towards 90% or more of its electricity generation from renewable resources. How can we meet peak demands with little or no use of fossil fuels? You are arguing the economics of my suggestion based on Business As Usual (BAU), but BAU will lead to a global catastrophe.

    And I reject your notion that more operators at $500k per position would be needed to control the geothermal plants. How many people were on $500k salaries when the plants were first run up? After a few cycles, don’t you think the normal operators wouldn’t learn about how to manage the field? And if it really takes expert knowledge to control the plant, couldn’t an expert system be devised to assist the operators? Remember that I am only suggesting changing the output level, not stopping and restarting the plants. And I have already accepted that not all geothermal fields may be suitable for this.


  92. John

    That data on Arsenic is out of date. Wairakei contributes very little to the river now since they have gone for about 80% re-injection.


    To go deeper than about 3km (the current deep wells) costs a lot of money – A 4km well would be about $25M and a lot less than 50% success rate. As they go deeper, permeability is harder to find unless you do fraccing. As for the rest of your ideas, you haven’t any practical experience, have you. It shows.

    If you have a downhole heat exchanger, you don’t have re-injection as there is no mass withdrawal to start with. Doh!. Many of the downhole heat exchangers in Rotorua were closed twenty years ago because the government of the day didn’t understand the difference between heat and mass withdrawal.

    Ground source heat pumps are only necessary for very cold climates. There is near no efficiency gains compared to using air in NZ.

    And you are wrong about the developments being only DSIR and MWD. They were in the early days but it has gone way past that. Acidification of brine comes out of the States and Binary plants are Israeli technology. NZ has been not at the forefront for 40 years.

  93. Hi jc2

    Sorry, I don’t have any specific information, although it is an alternative that I have thought about. One of the problems with pumped storage is that you need a low source of water as well as the elevated store. I am not aware of any North Island lakes which would suit this. However several pairs of lakes on the Waitaki seem promising.

    The catch is that we need the stored power in the North Island, rather than the South. Therefore to replace North Island fossil-fueled generation with South Island pumped storage, the transmission lines will need a significant upgrade. Also pumped storage has a cycle efficiency to consider. (I think this is about 85% but don’t quote me on that.) When transmission line losses are added, it makes more sense to me to look at storing the energy in its original form – hot rocks in the case of geothermal.

    Long term, I expect that pumped hydro storage will be implemented in the South Island to handle South Island wind farm outputs, while the North Island will use other options, and the HVDC link will need to be upgraded further. We might even see pumped sea-water hydro storage developed in the upper North Island.


  94. Hi Trevor,

    If enough power is available at $0/MWH, that sounds like an argument for pump storage into our existing hydro reservoirs. The limiting factors would be transmission and capital costs. Do you have numbers around this, which would enable a calculation?


  95. Trevor29
    No geothermal power station in NZ on the main grid is currently two-shifted at all – I was looking at their generation data yesterday on another issue. Like Dbuckley says, they are baseloaded for very good reasons. The Ormat plants actually have a reverse generation regime where they generate more at night that during the day because of their design. Poihipi Road was two shifted early on because they had consent constraints, but that stopped years ago when Contact built a pipeline from Wairakei to supply it. To my knowledge, the only field in the world operated the way you suggest is Geysers, and that is only because they made monumental investment blunders in the 80s.
    Taking your suggestion and adding 15% more plant would add about $40M to a plant like Kawerau. It would also need more operators to ramp it up and down at about $500k per position. The plant would need to be a lot more complex to cope with changing conditions and there would need to be consent changes. Then look at grid prices. The potential extra income isn’t there to justify that loading. Do the real numbers, not just dreamland stuff.

    With regards to re-injection, if you are inside the resistivity boundary (which generally also defines the production area) and in the formation that production comes from, there is a fair chance you will get thermal breakthrough and kill production. It is all published in reports on both Tiwi and Ohaaki. Both of those field collapsed their production and could only recover by very expensive changes to their field management
    For small installations (<20kW), downhole heat exchangers are best. They have been used successfully at both Rotorua and Taupo. There is a lot of good data on those and with no brine brought to the surface, there is no need for re-injection.

  96. For a few hours early each morning, electricity demand drops and spot prices for electricity drop also, more so in summer, and sometimes even to zero, as must-run and intermittent power generation exceeds demand. What I am suggesting is that we should look at ways of reducing generation which has a storage element, so the intermittent generation can run, thus preserving that stored power for later. Geothermal in general doesn’t have the flexibility to do this, but in part this is due to a lack of plant. Adding 10-20% more plant would allow higher output most of the time, with reduced output when demand (and prices) are low. Yes, the payback per dollar spent on plant may be less, but not much less because of the low margins between the cost of operating that plant and the low off-peak electricity prices. The income from the resource will be greater because more of the generation will occur at higher price times.

    Not all geothermal fields will be suitable for this. I know of one that is, because that is what they were doing for years.


  97. The Mighty River share offer document offers good insight into geothermal generation; this type of station is expensive to build, but cheap to run, at about $10/MWH, about twice that of hydro. Given the average spot price is around $70/MWH, they on average provide a reasonable margin.

    Thus geothermal is eminently suited to base load applications, and their lack of flexibility makes them the prime base load generator. Its easy to modulate hydro, geothermal less so.

  98. ChrisM You paint a pessimistic picture of our ability to learn how to drill deeper, and/or to better extract the heat from the rock where most of the energy is. Yes it is a heat mining operation, but I suggest that smart location of injection can optimise this. Drilling deeper means accessing higher temperatures.

    There may be merit in varying take from the fields within certain limits. That is obviously already done as part of the standard operations, power station maintenance, well workovers etc. Probably wouldn’t want to do this on a daily basis – but perhaps over the year to balance the wet and dry periods. Isn’t that happening already?

    ChrisM. One extreme of reinjection is down-hole heat exchangers and this is already done small scale. Rotorua had/has(?) examples of multiple houses connected to one well, thereby providing heating (and geothermal fluid for bathing) at a reasonably acceptable cost.

    Of course the other end of geothermal is ground-source-heat-pumps for small scale use. (See the GNS website.) This doesn’t even need to have a geothermal (hydrothermal) system. In fact I understand this is the boom area in many other countries.

    I do wonder at the disparity in the scale of investment in the development of geothermal compared to the scale of investment in prospecting and exploration. All the systems being developed were proved by MOW and DSIR.

  99. ChrisM – I never said that the reinjection needed to be performed close to the core production area. The main point that I was making is that the need for reinjection increases the cost to the point where it is uneconomical for very small operations. Do you accept this point at least?


  100. Trevor29 – yet again your demonstrate that your knowledge is superficial at best.
    Geothermal power stations are strip mining heat. Even when optimised for the field, which generally can only be done in hindsight, they still cause net mass withdrawal as well as heat extraction. That pressure drawdown means it will have an effect on surface geothermal features. This is why there are protection orders on most of the geothermal fields that aren’t currently being exploited for power.
    And you are totally wrong on re-injection. Reinjection has to be done outside the core production area. Otherwise the ~120°C fluid will quench the 270-320°C inflows and the former is useless for geothermal power. Reinjection is done for consent reasons, not for optimal field performance reasons. At the lower temperature, the fluid is super-saturated with silica so can’t be used for heat extraction because of deposition (including a few toxics) and environmental problems.
    The ideal situation from a field management point of view is to balance heat and mass extraction with recharge. With reasonable pressure drawdown, this can be achieved in the short term. However, thermal breakthrough from cold inflows gradually degrade the resource. The speed at which this happens is partially dependent on the imbalance between inflows and outflows. Volcanic eruptions also disrupt geothermal fields as Waiamungu showed.

    The best way for managing fields is steady state operation. Ramping them up and down, even over a long time period, causes a lot of field management issues. Also, geothermal costs about $3M per installed MW. If that extra generation isn’t being used, it makes the power from the in-service generation more expensive. Who is going to pay for this when the Greens have said that power will be cheaper? If you want storage and ramping ability, building large dams with big lakes is the most cost effective option.

  101. I was wondering what Gareth Hughes and Catherine Delahunty learnt from Contact about sustainability versus renewability.

    Yes geothermal has a future in NZ. But, what kind of future?

  102. Using geothermal resources to generate electricity is actually not very efficient due to the relatively low temperatures of the heat. It is more efficient to use the geothermal heat directly if uses for this heat can be found, such as for drying, water heating or space heating. To maximise the use of the resource, the geothermal fluids should be reinjected where practical, as this conserves both the remaining heat in the fluids and conserves the fluids themselves, while providing a safe way of disposing of the minerals in those fluids. It is not going to be cost-effective for an individual home to do all of this just for home space and water heating, but area-wide schemes or schemes for (or including) schools, retirement complexes, or commercial or industrial sites should be viable.

    There has got to be some benefit from living on the ‘ring of fire’.


  103. “We had lots of questions for them because renewable and truly sustainable are not always synonymous.”
    Care to expand?

  104. While I support the development of geothermal power, I see one trend that I think needs to change. In general, the power companies who build geothermal plants build them to maximise the use of the geothermal resource providing the plant operates at constant full power almost 24/7. While this maximises their profit for a given investment, it leads to the geothermal plant competing with wind and other intermittent or must-run generation at times of low demand. I would rather see extra plant installed at geothermal fields so that the field’s resources can be fully utilised without the plant running at full power all the time. This would allow the plant’s output to be higher at times of higher demand and lower at times of low demand, and would also allow the geothermal to provide some backup for the intermittent generation.

    Unfortunately ramping the output of some geothermal fields up and down is not always easy, particularly fields with both liquid and steam output, but any means to allow a controlled variation in the output level would be welcome, whether it be daily, weekly or even increasing the output over winter and decreasing it over summer.


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