Solid Energy fires up coal seam gas generator

It is an interesting proof of concept that unfortunately emphasises the least efficient use of the coal seam methane resource. Scoop captured the press release:

Speaking today at Solid Energy’s Annual Meeting in Auckland, Chief Executive Officer, Dr Don Elder says that in a first for New Zealand, coal seam gas is now producing enough electricity for 500 to 800 homes, using one of the world’s cleanest forms of thermal energy.

The on-site generator is currently fed by four wells taking gas from a 32 hectare section of the coalfield. Gas flow from this small pilot has the potential to power as many as 1000 homes but it is not yet known if the local network connection can accept that much electricity.

Coal seam gas can be used for industrial energy, electricity generation and could be injected into gas transmission systems to supplement gas resources.

While it ceratainly is unique to be using coal seam gas in New Zealand, burning it to produce electricity, where up to two thirds of the energy can be lost in the form of waste heat, is a poor use of a non-renewable resource. This is particularly true here, where it is common knowledge that renewables, including baseload geothermal, are cheaper than thermal baseload.

That last use mentioned in the quote is the future for natural gas in New Zealand – direct use in homes and in industry, where the heat is what is wanted, and where using electricity to create heat is in fact wasteful. The long transformative journey from gas > heat > electricity >  heat for many uses is a waste of a finite resource.

Coal seam gas does have a future in New Zealand, particularly given the rapid dwindling of our big gas fields. We can expect serious shortfalls in gas supply here in NZ by 2015 if current trends – and waste – continue. Let’s be smart about how we use it – this time.

17 Comments Posted

  1. This (coal-gas generation) wouldn’t be so bad if it was run as peak-shaving plant, i.e. not run when electricity demand is low, but only during high or peak demand periods, since this usually requires gas generation to be run anyway. I suspect however that to save money, they will put in only enough plant to consume the available gas if the plant runs continuously, thus forcing down electricity prices when demand is low. This will have some impact on the returns from wind, wave and flow-of-river hydro generation which could meet this demand.


  2. If we are burning gas it is basically methane – of all the Carbon based compounds it gives the best Hydrogen bang for the Carbon buck Not as hot as some others but far lower impact than burning coal directly.

    If we are burning coal, someone has made a mistake.


  3. Robin F: It is not just CO2. Inevitably there will be other combustion products.

    Coal also contains various contaminants which also are released into the environment or which need to be disposed of in landfills. These include sulphur, mercury, other heavy metals including uranium, and radon gas. It has been reported that more radioactive material is released into the environment from a coal-fired power station (including mining) than from a properly run nuclear power plant of the same output. Not that I am suggesting nuclear power for New Zealand!


  4. dbuckley:
    Two counter examples for you:
    If I take a 50% combined cycle gas-fired powe station and use it to power heat pumps with a 300-400% apparent efficiency – say 350% – then the overall effectiveness is 175%. That is almost double what a boiler can achieve.
    If instead, I install a Combined Heat & Power unit with 40% electrical output, 40% heat output and 20% waste, and that feeds my heat pumps, I get only 140% out from the heat pumps and 40% out from the CHP giving a total output of 180% – twice that of your 90% efficient boilers.
    The key to achieving these high heat outputs is that for space heating and domestic hot water heating, the required temperatures are low – 60C for hot water and less for space heating. Where higher grade heat is required, the heat pumps are less effective and direct use comes in. However the value of the electricity generated is more than that of the gas consumed so CHP may still be cost-effective.
    I believe that what is killing CHP may be the short term thinking of the bean counters and the mistaken believe that low gas prices are here to stay. I believe that gas prices will rise, and faster than electricity prices (as we move towards 100% electricity from renewables) so that instead of gas prices pushing up the price of electricity (due to using gas to generate electricity), what we will see is electricity prices being pulled up by gas prices (as users substitute gas with electricity, possibly with real-time demand-side management responding to the instantaneous electricity price).


  5. Trevor29: It is true, heat pumps have an apparent efficienecy of 300-400% however converting coal / oil / gas to electricity has an efficiency of under 40%, and then you need to add transmission losses on the way, plus energy required for spinning reserve on generation, and supply load mismatch.

    When you consider that a decent gas boiler has a conversion efficiency of over 90% then all the agro (and capital expense) of converting to electricity and back again doesn’t make good economic sense.

    You have cogeneration upside down. You size cogen for the heat output required, and then the electricity is the free byproduct. Time was when this was a great idea, best commercialised (in my opinion) by the now almost forgotten Fiat totem in the 70s, but now that (again) we have boilers that are over 90% efficient its better for most purposes to use less fuel than it is to use more fuel and have a byproduct. There are cases when that is not true, of course, greenhouses that want heat and CO2 being one good example.

    In summary – and as a big fan of CHP it saddens me to say so, but – as a generally applicable technology, CHP has had its day.

  6. I always did like the cogeneration of power and heat and have since I first studied post-soviet mongolia all those years ago when i was in intermediate. As an added bonus the, soviet built, underground hot water pipes which run to the appartment blocks provide a nice warm niche for the homeless children created as a consequence of the soviet occupation 😛

  7. Gas space heating and gas water heating takes more energy than heat pumps, particularly when the outside temperature isn’t too cold. Heat pumps get very good energy returns when they are working with low temperature differences.

    The best use of gas for heating is co-generation, where the heat is a byproduct, but this is quite expensive to consider for domestic use.


  8. I thought that the north island was actually sending power to the south island not too many weeks ago. Y’know during the low lakes quick ring ring up the power commision to let us take another 2 metres of water situation that occured. I can’t have dream’t the entire issue………………..can I?

  9. Back on topic – Trevor29 – why do you consider the use of gas for home heating (or water heating) to be “a waste”?

  10. Johan: The electricity you actually use at some point in time may be generated from any source. Power companies that sell you “all green” power do nothing of the sort.

    What it means is that they will inject into the grid the number of KWh of electricity that their customers use. The customers use power from the grid.

    Depending on your perspective, its either the same thing or totally different.

    Kevyn: The stats are interesting but dont represent reality, again because of the nature of the elctrical grids we have: In the SI we have 100% renewable generation, but that doesn’t mean 100% of the power we use comes from renewable sources, we often get juice from the NI and some of that juice will be thermally generated.

    Many a SI fella wants to pull the plug on the interisland link, which would make our power 100% renewable, except for the times when the lights go out.

  11. Kevyn
    I live in Epsom and we use Trust Power, who claim they only use renewable resources. We have never had any problems with supply but I assume they may have base load problems occassionally? I also note they are not the most popular supplier in Auckland. My point is that there are options available to Aucklanders to get electricity supply from renewable sources.

  12. Kevyn

    Aren’t Aucklanders’s embarassed or ashamed that barely one-third of their electricity is generated from renewable sources? Or don’t they know? Or don’t they care?

    Do we have an option?

    As an Aucklander I dont have much choice in deciding were my electricity comes from. Renewable or not.

    No, not ashamed at all. Would only be ashamed if I had a choice of either a renewable or non-reneable supplier. Which we dont.

    Do we care, yes we do but we have no choice.

    So free up the RMA and lets build the tidal generator between the Hauraki and Manukau Harbours, The windfarms at Waiuku and Kaukapakapa, etc.

    You will be pleased to know that electricity is generated from our landfill dumps using the methane gasses to run turbines. (Greenmount has been running for over 10 years and Meola Road I think is still operational – but could be wrong).

    Wonder if the gasses produced at the Mangere sewerage works could be used to run a few electricity turbines? Seeing that it is now a fully contained operation.

  13. I bet the Huntly coal seam is only a stones throw from the gas pipeline to Auckland 😯

    Aren’t Aucklanders’s embarassed or ashamed that barely one-third of their electricity is generated from renewable sources? Or don’t they know? Or don’t they care?
    *Assuming Auckland/Northland consumes one-quarter of NZ’s electricity.
    Remainder of North Island consumes half of NZ’s electricity, two-thirds from renewable sources.
    South Island consumes one-quarter of NZ’s electricity, 100% renewable sources.

  14. There is one less efficient use of the resource – flaring it off!

    While direct use of gas for cooking and industrial heat is more efficient than using it for generation, using it for home heating or domestic hot water heating is a waste. Cogeneration at sites needing low temperature heat is one of the more efficient uses.

    I believe the long term future for natural gas is none of these – it is as a transport fuel for light vehicles where pure electric power isn’t feasible.


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