Highlights: the use of electrolysis for balancing an electrical grid, the efficiency of creating hydrogen at high pressures
Jim Shnell responded to the above article by Nicholas Keyes
The blog submitted by Nicholas Keyes on March 18, 2015, “The Energy Future, as seen from Denmark,” discusses, and in part draws from, a new ESMAP report entitled Bringing Variable Renewable Energy Up to Scale. The blog does an excellent job of shedding light on, and bringing to life, some of the main issues and ideas in the Report. Although the Report and the blog explain the problems and describe possible solutions very clearly, we would suggest a slightly different analysis and we would offer a set of solutions that we consider to be significantly better.
The blog notes that Denmark “generates a third of its annual electricity demand from wind, and solar capacity is growing as well” and states that, for green energy, “there is no better place to get a glimpse of the future than Denmark.” Based on information in the blog and in the Report, however, it seems that a better place to get such a glimpse might be Norway. The Report notes that “In Denmark, the aggregated wind capacity dropped 90 percent over 6 hours in January 2005.” How did Denmark survive such variability in its supply of electricity? The blog itself notes that Denmark “enjoys the great advantage of . . . electricity system interconnectors with neighboring countries” and that “Norway . . . can import and export electricity whenever Denmark has a surplus or is running a deficit.” It sounds like, if we are going to follow Denmark’s example in the future, we had best understand how Norway fulfills such a supporting role. Norway’s ability to provide such support is in large part the result of its reserves of hydropower, which in turn are a result of Norway’s terrain and climate. The blog notes that “Such advantages are hard to replicate, but that does not mean that transitioning to an electricity grid powered to a large extent by solar and wind is out of reach.” We agree with that statement whole-heartedly. We also agree with the blog’s position that some of such a supporting role can often be fulfilled by reservoir hydro (although droughts and other effects of climate change may often challenge that resource) and demand response (although, in developing countries where electricity is in short supply, cutting back demand may not be a very effective tool).
It is when the blog and the Report suggest reliance on energy storage and natural gas-fired power plants for such support that we differ. We also differ with the suggestion that wind and solar power should be harnessed to convert biomass into transport fuels. We start from the premise that one of the primary objectives in harnessing wind and solar power is to avoid the creation of greenhouse gases by the combustion of carbon-based fuels. The most significant shortcoming in wind and solar power is that they are intermittent, and if the electrical grid is going to rely on them for more than 30% of its capacity, it must be balanced for the variability and lack of predictability of those resources. Burning a fossil fuel to balance the grid is, however, antithetical to the purpose for moving to wind and solar power in the first place. (The use of wind and solar power to create biofuels which then create greenhouse gases is also antithetical to the purpose for moving to wind and solar power.) The fact that hydropower creates no greenhouse gases and is baseload power makes it ideal for the purpose of balancing, but there are many areas of the world where there is not sufficient hydropower, and many other areas where drought is making the use of hydropower problematic. Geothermal is another source of energy that is baseload and creates no greenhouse gases, but in most parts of the world there is not enough geothermal energy that can be accessed through conventional methods to provide the amount of balancing that would be needed.
There are, however, vast geothermal resources in the deep ocean floor, with enough energy to provide the foundation for the solution to global warming. We focus on the geothermal energy from the ocean rift zones, which wrap around the world for a distance of over 65,000 kilometers and release the energy from magma that rises continually from the mantle to the ocean floor to create new ocean crust, thus providing vast amounts of energy. We can harvest several times as much thermal energy from the rift zones as the total amount of energy used by people worldwide. Such geothermal energy is not only vast, and distributed around the world (and therefore, suitable as a foundation for the global solution to global warming); it also enables baseload generation of electricity and produces virtually no greenhouse gases or other pollution. This thermal energy could be used to generate electricity by drilling wells in, and placing turbine-generators on, the ocean floor, where they would operate by remote control and transmit the electricity to shore by high voltage direct current transmission lines. Because of the extremely high temperatures in the rift zones and the high pressures at such ocean depths, the resource is supercritical and therefore highly efficient, reducing the cost of the electricity below the cost of electricity from fossil fuels.
The foregoing factors might initially suggest the use of ocean geothermal energy to provide all the electricity that we need. A quicker solution to climate change would, however, use ocean geothermal resources to provide enough baseload energy to balance wind and solar power. The excess electricity produced by ocean geothermal energy and not needed for the grid can then be used for electrolysis, to produce hydrogen that will replace petroleum as a transportation fuel and a heating fuel. (Steam reformation of methane should not be used to produce hydrogen because it creates greenhouse gases.) Denmark, Germany and a few other countries have advanced more quickly than most countries in adopting wind and solar power, and they are therefore more concerned with balancing wind and solar power. Other countries, especially those with insufficient power for their grids, are likely to need more baseload power. Ocean geothermal energy can, however, be a very valuable resource to all countries, because it can perform both baseload and balancing services at the same time without reducing its production of energy.
Geothermal resources usually generate electricity in baseload operation and reach their maximum efficiency in that mode. By pairing an ocean geothermal electricity station capable of generating, for example, 100 MW with a nearby ocean geothermal electrolyzer that uses 100 MW, as well as connecting the electric station to the grid, the station is essentially fully dispatchable with respect to the grid because the “extra” electricity will be converted into hydrogen. The use of ocean geothermal resources to support the electrolysis is important because supercritical water has properties that render electrolysis of supercritical water significantly more efficient than electrolysis of water at standard temperature and pressure. In addition, scientists at Lawrence Berkeley National Laboratory and Argonne National Laboratory have recently developed hollow nanoscale frameworks of platinum and nickel, which use 85% less platinum and provide more than 30 times as much catalytic activity as existing catalyst structures. Electrolyzers can, however, operate efficiently at only 5% of their capacity, so up to 95 MW of electricity could be sent to the grid when needed for balancing, baseload power, etc. Moreover, the U.S. National Renewable Energy Laboratory recently determined that electrolysis is ideal for grid balancing because electrolysis can be turned down, and the electricity diverted to the grid, in less than 2 seconds. The system described above would first be a standby supplier of up to 95 MW of electricity, including balancing power, to the grid (presumably in exchange for capacity payments for 95 MW and energy payments for the electricity used) and second (but, in many countries that use a lot of wind and solar power, predominantly) a supplier of hydrogen to replace petroleum in exchange for energy payments for the electricity used in electrolysis. It could respond both to the needs of very green countries, and to the needs of less-green countries, flexibly as all of those systems continue to evolve in the future.
The two separate branches of the energy industry, the production of electricity for the grid upon demand and the production of fuels to inventory, will thereby be unified, and one can be used to balance the other without the need for large amounts of battery storage, which is both expensive and inefficient (since batteries actually consume electricity rather than producing it).
Moreover, the adoption of ocean geothermal energy in support of solar and wind power will accelerate the development of all three forms of renewable energy, and can eliminate the use of fossil fuels.
The Ocean Geothermal Energy Foundation is a nonprofit corporation formed to support the research and development of the system described above. We will be attending the World Geothermal Congress in the week after next to meet with people and, on the afternoon of Friday, April 22, to present our paper describing the system. If you happen to be attending the Congress, we would appreciate an opportunity to meet with you, and hope that you can attend our presentation. In the alternative, for further information, please visit our website at www.oceangeothermal.org or send us an email at firstname.lastname@example.org