Considering future energy options: Extrapolations from a real experiment

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4 August 2014

I had the opportunity last week to spend some time with a good friend, a fellow physicist with whom I shared nearly 40 years of collaboration and conversations largely around the subject of energy. My friend is Fritz Wagner, the former director of the Institute of Plasma Physics (IPP) in Greifswald, Germany, and a recognized international expert in plasma physics, experimental fusion devices, and analysis of the world’s current energy situation. 

Since Wagner retired as the IPP director five years ago, he has spent much of his post-retirement years studying the global energy situation and potential solutions. Given that the economic health of a developed nation is proportional to the availability and use of energy resources, this subject is clearly connected to our well-being. Many factors influence this issue, including the often competing demands of economically efficient energy production, control of CO2 release, and the global interconnectivity of energy production and use. A singular goal would be to minimize the all-too-frequent conflicts over the acquisition and distribution of hydrocarbon fuels. 

Wagner recently published an important study on an optimal mix of renewable and conventional energy sources based on a unique and ongoing experiment in his home country of Germany. Germany is not only the economic powerhouse of the European Union; it also is the world’s renewable energy kingpin. Germany’s sophisticated energy infrastructure and its interaction with the rest of the EU power grid draws attention to the need for balancing energy production with demand, and for achieving stability in the power transmission interconnections across political boundaries. 

Why is Germany so interesting as a test case for these important problems? With an installed renewable energy (RE) production capability of 36 GW photovoltaic (PV) and 32.5 GW wind, the total renewable energy production now exceeds the typical base electrical load (40 GW) for the entire country. Since there is very little energy storage capability in Germany (nor anywhere else for that matter), the peak energy production from RE generation sources must be shipped to other countries through the European grid, and the production level of existing thermal energy plants must be turned down. Transporting the power to other consumers on the EU grid often leads to a situation where Germany is paying other countries to absorb the power—leading to the strange situation of negative electricity prices. The alternative of turning down a thermal plant is restricted due to technical and economic considerations. Such plants basically operate between two limits, and the start-up and turn-off costs are high because large thermal plants are not designed for intermittent use. The problem of localized energy production exceeding demand could also be dealt with if technology existed for large-scale energy storage. Presently, in Germany, the existing storage capacity based on pumped hydroelectric facilities is only 50 GWh, which is a factor of 660 less than is needed in an ideal situation for load balancing with the present demand curves. In addition, the prospects for any new high-capacity energy storage capability based on batteries or chemical conversion technologies are far from near-term use, with respect to both scalability and cost. 

Wagner published his analysis of the present energy situation in Germany in a recent paper,[i] which he also highlighted at the International School on Energy sponsored by the European Physical Society and the Italian Physical Society.[ii] He outlines an option for both Germany and the rest of the European Union that entails optimizing the mix of renewable energies versus conventional sources, and taking full advantage of strengthened interconnections within the EU-wide power grid. The analysis attempted to minimize the necessary backup needs, with consequent reductions in the required storage capacities and CO2 production. Wagner’s analysis shows that such an optimum mix for Europe has an installed capacity of RE that is about 40% of the residual base load. In addition, there is an optimal mix of PV- to wind-produced energy because of the diurnal and geographical production variation of these two energy sources. By balancing the geographic variations across the very different environments of Northern and Southern Europe, overall variations are minimized in a case optimized for the entire continent. 

Given that there are no near-term prospects for scalable storage capacity, other options are possible—such as using price variability to influence the night/day demand variations. Somewhat surprising is that with the optimal installed RE capability, daytime becomes the time of larger production capability and thus offers the lower cost of delivery to consumers. Larger scale use of electric cars may offer some storage capability, and given the need for a roughly equal capacity for large-scale thermal plants, options for heat cogeneration and electrolytic generation of hydrogen or methane may also be viable options.

This analysis could be extended to North America. The continent has large areas suitable for PV plants (the American West) and significant capability for wind generation. Moreover, there is a much more economically favorable conventional generation capability based on the recent exploitation of natural gas captured by hydraulic fracturing of shale gas reserves. However, it is difficult to imagine that the present US political environment would yield anything like the power feed-in tariff benefits offered by the German government to propel the nation forward to become a world leader in renewable energy. The basis for nuclear-based energy generation is zeroed out in Wagner’s analysis, given the post-Fukushima political liabilities and the subsequent actions by the German government to phase out power generated by existing German fission plants by 2022. The other nuclear option (fusion) is neither part of the near-term nor the mid-term equation. Both Dr. Wagner and I began our scientific careers in fusion research, and Wagner spent his entire professional career working in this frontier field of research. We both agree that for inclusion in any analysis of energy generation, this technology is not part of the world’s energy sources for the foreseeable future. However, its prospects to minimize the waste and fuel cycle concerns of fission and to avoid the deficiencies of intermittent electricity sources—which become increasingly obvious from the German “real experiment”—are so great that worldwide research efforts in this energy frontier should be continued, if not intensified.

[i] Friedrich Wagner, Eur. Phys. J. Plus 129, 20 (2014); DOI 10.1140/epjp/i2014–14020–8.

[ii] Friedrich Wagner, “Features of an intermittent energy supply,” lecture at the EPS-SIF International School on Energy, Varenna, Italy, July 2014.