Storing excess nuclear and fossil power

Under a recent blog post here, numerous readers commented that green gas could be made from electricity when the price on the power exchange is low or even negative. Craig Morris says that is exactly what will happen – it’s just not “green gas.”

CO2 to Methanol plant

CO2 to Methanol plant in Iceland. (Photo by ThinkGeoEnergy, CC BY 2.0)

The very day that I posted my conclusion that power from excess renewable electricity would not be competitive anytime soon, Germany opened its largest power-to-gas (P2G) facility, which aims to run for at least 4,000 full-load hours a year (a capacity factor of nearly 50 percent). Clearly, Germany continues to pursue this power storage solution, and these facilities will largely be hooked up to the grid and purchase electricity when prices are low (or even negative) on the power exchange.

My readers are correct when they say this situation considerably changes the calculation. I would simply clarify what I meant in my previous post when I wrote, “This scenario is indeed more likely than (green) hydrogen for the interim”: we are not talking about storing merely excess renewable power here, but excess grid power – and that includes electricity from nuclear and fossil fuels.

We need to keep two things in mind. First, the price of any excess renewable power in Germany will essentially always be the average feed-in tariff until the policy is fundamentally changed. So if we pay an average of 10 cents for a kilowatt-hour of green electricity, that is also what the excess green power we store as gas will cost. The price on the exchange is completely irrelevant for feed-in tariffs.

Second, while low/negative prices on the exchange need to be taken as an incentive to consume/store electricity, a business model based on low exchange prices is not sustainable. Renewables are cutting into the profits of conventional power firms in Germany. Indeed, in mid-June rating agency Moody’s downgraded German energy giant RWE to Baa1, just two steps away from junk bonds. In comparison, the firm had an A3 rating in 2011 – the year of Fukushima.

Were P2G to be rolled out soon on a large scale, it might indeed kill several birds with one stone. If it were to increase demand at a time of low prices on the exchange, the result would be slightly higher prices – and slightly greater profitability for the conventional power sector (feed-in tariffs for renewables would remain completely unaffected). Dispatchable capacity would then not be in such financial straits, and the need for capacity payments would be greatly reduced.

P2G from electricity that costs only three cents per kilowatt-hour might even be competitive with the cost of power plants for peak demand. We will simply have to wait until Audi and Etogas reveal the expected price curve for their system.

Let’s just be clear about what we are talking about: not “green gas,” but gas from the German grid, which largely consists of fossil and nuclear power. And conventional energy providers, not providers of renewable power, would benefit from higher exchange prices. Furthermore, green gas from 100 percent renewable power is unlikely to be cost-competitive in the next decade.

The good news is that the process will probably work on a large scale and could indeed be competitive even from largely renewable power by the 2030s. Germany would then not have to wait until 2050 to have 80 percent renewable power.

Craig Morris (@PPchef) is the lead author of German Energy Transition. He directs Petite Planète and writes every workday for Renewables International.


Craig Morris (@PPchef) is co-author of Energy Democracy, the first history of Germany’s Energiewende.


  1. Nichol Brummer (@Twundit) says

    Interesting, this. The negative prices on the exchange are not a problem for renewable producers, thanks to the feed-in tarrif. So this technology only solves a problem for the conventional producers. But it also helps stabilise the grid with even larger fraction of renewables .. while eventually the feed-in tariffs will be slowly removed, completely. And by that time, there would be a problem for renewables, if energy cannot be stored. Can we dream of things like electrolytic steel, based on even more ‘too much’ renewables, after that?

  2. Kent Otho Doering says

    Dear Craig: As an American ex-pat vet residing for decades in Munich an outsourcing for German industry – sometimes green for 4 decades, I`d like to add my two cents. There are two types of gas under discussion here. There is “bio-gas”, referred to as “Grün” by people here, and there is syn gas, back up buffering system advocated by Linde and B.M.W..
    Munich utilities has been doing both for decades.

    Stadtwerke München, SWM, Munich Utilities have two- bio gas systems, true green gas. One is in Grosslappen, north of Munich.
    The Grosslappen plant takes vegetable wastes, i.e. unsold, rotting vegetables and fruits, collected separately from the wholesale markets, vegetable and fruit stands, and supermarkets, chops it, and mixes in whatever grass and leaves it street sweeping and parks commission also pick up, and from the “green” – “compost” garbage it picks up separately in suburban districts like Pasing, Grünwald, Solln, etc. This “compost” is chopped, and mixed with sewage sludge collected from the sewage system– and goes into big”paddle stirring “methane generators”. They also put “methane collector pipes on the old garbage hilly garbage cumps they greened decades ago when they built a waste to power garbage incineration plant. That bio-gas also goes into the system- and it is burnt in a small Gas turbine- Steam Turbine, combined cycle power plant at 60% efficiency – which also feeds heat addtional heat into the extensively built out and connected long distance heating grid. New material is constantly coming in, so the top layers are removed via archimedian screw pumps- and the methane enriched wet sludge is incinerated in teh 400 mw garbage incineration plant at Oberföhring.

    (Everything I throw in the trash and flush down the toilet is returned to me in the form of power and long distance heat – in the waste to power system.)

    Munich´s Hellabronn Zoo is just acros the Isar River from a large, efficient Combined Cycle, GaS, Gas Turbine and Steam Turbine power plant.

    Power plant south was upgraded from coal to natural gas because it is a fast ramping system to that can be quickly ramped up and down to accomodate for variable solar and wind variability. They squeeze even more energy out of the 60 % gas fired, efficient system boosting it to 95% efficiency, by feeding the steam into the extensively built out district heat system for condensation and recycling in the Rankine cycle.

    The municipal Hellabronn Zoo long ago hooked all of its buildings up to the efficient, long distance, heat hot water grid, which made it an ideal candidate for true “Green Gas” power and heat. Stadtwerke Munchen, SWM, the city owned utility- built another paddle methane digester on site. A shredder takes all the uneaten plant feed, which used to be just composted, and mixes that with shredded manure and straw from all the animal houses. That generates enough “Green Gas” – to fire another
    small, combined cycle GaS, gas turbine-steam turbine, power plant on site.
    That Combined Heat Power system more than covers all the zoo needs from the animal manure, and it now exports power and heat into the grids.

    The SWM will squeeze even more power out of the zoo´s internal district heat system by installing, experimental, state-of-the-art, alpha-Stirling motors driving A++++ super efficient generators on the heat grid to building interfaces.
    That is – the complex combined cycles look like this:

    Manure methane recapture => feeds “green” bio-gas to a gas turbine – driving A +++ generator- its hot exhausts -> heat steam for the Rankine cycle steam turbines => steam recondensed by local district heat to the animal houses =>Alpha Stirling power on the heat grid building interfaces => goes to ultra-efficient, perment magnet and resonance aided, 42 kHz high pulsed- efficient “fuel cell” syn-gas generation -of 500 cubic liters per hour per input kWh. This is “heat recapture, counter-entropic engineering”.

    That is, a GaS plant has a 60% “green gas” to power conversion efficiency. We squeeze more power out by feeding steam heat into district heating – for 95% energy exploitation efficiency in Combined Heat-Power mode. Advanced Stirling motors at the heat grid -building interfaces – driving A ++++ rated generators generate more power onto the grid- which includes special new “fuel cells” with high gas output per input kWh.

    That is, the added Stirlings on the Zoo bio-gas poweredsystem – will generate another 5000 kWh of power going to efficient syn-gas- generation- namely 2000 cubic meters of SynGas an hour which flow back under the Isar River to the big 500 MW – GaS system. . The Hellabronn “bio-gas” system is thus “overunity”.

    And that shows the way to the next massive changes to the Munich system.
    5000 German cattle, pig, and poultry farms already use bio-gas digester – and bio-gas power systems, many of which are primitive and crude. Still and all, those five thousand farms generate a full 800 megawatts of power, an average 24 hour constant output of 160 kWh per farm.

    Dr. Axel Berg, S.P.D., is an ex- member of Federal German Parliament, and was 1st Assistant Federal Minister of Environmental Protection- for ten years under both the Red-Green and Black Red coalitions, and is now C.E.O. of the German section of “EuroSolar” in Munich. Dr Berg and I are of the opinion that the best way to cover the short fall of solar at night is to provide more incentives to all 200.000 farms which come into question- to build out ultra-efficient “bio-gas” combined heat power systems.

    Bio-gas manure methane now escaping into the atmosphere has a “greenhouse gas” effect 25 times higher than co², so it makes common sense to burn as much as possible instead of natural gas in power and heat systems.

    We can boost the average output gas to power per farm by using state-of-the-art electro-paddle stirred fermentation units and using new automotive technology- driving A +++ generators, for power, and additional Stirling motors on the exhaust systems, or in the case of some advanced farms,using ultra-efficient fuel cells for combined heat power – with Stirling motors on the heat exhausts gerenating more power.
    That is, using optimized systems, we can boost the average farm “bio-gas” recapture power heat outputfrom 160 kWh average to between 250 and 300 kWh per farm.
    A lot of farms have solar on the rooftops and participate in wind co-ops. However, Munich utiites and other utilities are now taking a different build out approach. These are combined heat power systems, and thus receive direct German subsidies from the carbon eco-tax fund of Euros per producing kilowatt. There are other eco-tax subsidies for “bio-waste” systems. And the utilities themselves can participate in the build out providing forward financing and optimized-state-of the art technology.

    There are still two hundred thousand German farms tht can be built out to optimized manure methane-bio gas power heat systems (which also eliminate heating oil or nat gas heat costs as well.) An average farm consumes about 2.500 liters of heating oil a year. Cutting that at .80 Euro cents a liter… helps for additional amortization of the system.. as that is a savings of €2.000 right there.

    Optimization boosts average output capacity from 160 kWh to over 220. (Multiply that times 200.000 and see the potential now being tapped – 44.000.000 kWh, or 44.000 mWh, or 44 GW, the equivalent of 44 nuclear reactors or 220 coal burning power plants. Of course, we don´t need to run those bio-gas systems 24 hours a day. There is all the rooftop solar going in, meaning they do not have to generate power for at least 6 hours a day. And then, peak demand starts to drop in the afternoon when all the schools and universities close, offices close, and drops even further when commuter systems go back to”normal” after high pulse during rush hours.
    Domestic demand, now covered by wind, also drops off radically at night between 10 p.m. and 4 a.m.
    That is why German city owned utilities will also provided incentives to the farmers to use manure – bio-gas, compressed gas storage tanks-and double capacity of the ICE-Stirling or fuel cell-stirling CHP systems. The build out will provide cost effective, fast ramp up, distributed SMART GRID back-up baseline power. Dr. Axel Berg points out that makes no sense to use agrarian bio gas to generate power when all the still building out, rooftop solar is up and operating during the day, nor to use it between 10 P.M. and 5 A.M. when industrial, office, school, commercial, and household demand is at a minimum draw.
    We will apply that “extra bio gas” power from 5 A.M. to 11 A.M. when solar really starts to kick in, and from about 4.OO p.m. to 10.00 p.m. to meet peak load demands when solar is starting to produce a lot less.

    The increase in the build out of manure methane bio-gas is already starting to happen, as city owned utilites are signing a lot of production and power delivery deals with regional farmers. Farm bio-syn gas will be the chief cost effective, fast ramp baseline power backup for all the rooftop solar that went in and is still going up at increasing paces as heat recapture sysetems drop the cost of materials and production and new design breakthrughs double efficiencies. (Next gen solar panels will be half as much to produce with double the capacity – not needing F.I.T.s which will expire at 52 GW installed. So, we can expect installed capacity of about 204 GW (capacity, not delivered power) by the end of 2025. According to Dr. Berg, agrarian bio-gas systems will provide baseline back up for at least 90 GW of actual delivered solar power, and the combination of both will provide more than 35% of actual German power needs- at any time of day or year.

    There is Green “bio-gas” which is already in use and extensively building out as described above, and there are “syn-gas” sy<stems as proposed by B.M.W. and Linde. It is not a matter of "either-or", but a rather both. And that is the path currently being pursued by Munich Utilities.

    Let us get back to the brilliant long distance heat hot water system- which is already over 600 km long and being expanded to 800 km by the end of 2026 and more intensively connected.
    Putting 5000 big 250 kw Stirling motor units on 5000 heat grid- large building interfaces will "squeeze" another 1.250 MW out of the already ultra-efficient CHP system,and putting 25 kw Stirling motor units of 15.000 small building- heat grid interfaces will "squeeze" yet another 375.000 kW, or 375 MW – total additional Stirling power- 1625 MW, the equivalent of 1.5 small nuclear reactors. 625 MW will go to Munich industries at low costs (keeping the region, energy cost effective) and a full 1000 MW will be going into advanced syn gas we were discussing- hydrogen mixed with co² recaptured from the big waste to power systems – broken down on tightly spaced electrocatlytic plates- with the carbon combined with the hydrogen for easy to handle artificial methane. (Hydrogen is very tricky due to "hydrogen embrittlement"..At 400 liters per input kWh, or 4000 cubic meters per input mWh, that means an additional 4.000.000 cubic meters of syngas an hour – feeding back into power plants, factories, heating systems (all using combined heat power systems feeding power back to the grid in semi-closed loop systems.

    Munich already divested of nuclear in 1992 to invest in hydrolectric- and provides over 160.000 two person households with "green" hydro-electric power. Using the profit center of its long distance heat power system, it built out a massive mass transit system- over the last 40 years which slash fuel consumption- 6 subway lines which weave across town, and 14 light rail, low entry streetcar lines, (all brake energy recycling) and 400 ultra efficient, microwaved air intake, turbo injection diesel busses. (They cooperate with German Rail/Deutsche Bahn- which built out 8 cross town commuter lines out in 15 different directions. (currently running nuclear, but shifting to new, floating, anchored, on-stream hydroelectric systems.) Daily ridership of the MVG system is about 2.6 million passengers a day, saving a lot fuel for commuting. I advisedly note that Munich Utilities also used profits from the district heat to massively invest in inland onshore wind, big coastline wind, and offshore wind-projects – still building out. They supply over 760.000 two person households with energy from wind (total wind-hydro-output – thus currently supplies over 920.000 two person households , i.e. most residential – for those sbuscribing to Munich Utility power, and wind brouight in via HVDC also powers the subway, light rail, and some of the commuter rail systems (the most advanced and "green" urban transit system in the world.) it operates its own rooftop solar systems on city owned hospitals and schools, and on top of the two Munich trade fair centers. In addition they also re-distribute over 420 mw of daytime rooftime solar fed in on the feed in tariff system- (when both wind and solar are working, they can ramp down the Gas sytems to 10% on weekends, and even some during the week.) The coal fired power plant will also be converted to GaS with two big Siemens gas turbines rated at 200 mw apiece and use syngas plus "magnetic resonance steam igntion systems" now being developed to fire the system, doubling capacity to 800 mw
    Solar, wind, Bio-gas, Syngas plus MRSI will enable Munich to be totally off fossil fuels ahead of schedule- by about the time the remaining nculear power plants are scheduled to shut down- while covering the shortfall from that.

    And I haven´t reven touched all the revolutionary "energy efficiency" systems going in. The Munich region already has a per capita fossil fuel consumption and co² emission rate that is 70% below any comparable city in the U.S. (cutting fuel purchases means "MARGINS".
    Sustainability is a booming sector, and it is one factor which has helped to create another 28.000 new jobs in the region in the first half of this year. The region is booming due to cheaper, clean energy and excellent, clean transportation infrastructure and demand for "clean tech." The State of Bavaria just reported that city, state, and Federal taxes are now up by 28 billion Euros in the first half of the year, up totally by 52.000 billion. (the other benefit of clean tech) and unemployment is down to less than 5%.
    Energy efficiency systems going into governement owned buildings also slash consumption and costs by between 40 to 60%, another factor in the balanced budget situation here in Germany.

  3. Patrick Kalinowski says

    Thank you Mr. Kent Otho Doering ! No disrespect to Mr. Craig Morris, but your comment is more interesting that the article you are commenting on.

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