Coal-fired power: How much longer?

Author: Prof. Dr.-Ing. Klaus Görner University of Duisburg-Essen, Chair of Environmental Process Engineering and Plant Technology and Rhein Ruhr Power e.V.. (As of November 2016) The threat of climate change has triggered a rethinking of energy supply and consumption worldwide. The Paris climate protection resolutions (COP 21) have virtually agreed on binding reduction targets worldwide for the first time. In this context, however, it is important to emphasize that countries such as the USA, China and India are already responsible for more than 50% of CO ₂ emissions today - and the trend is upwards, both in absolute terms and proportionally. This does not mean that we as an industrialized nation can and should sit back with a share of less than 2%. Quite the contrary. But we must also be aware of the limited impact potential of our efforts.

In the European Union, the process of energy transformation already has a longer history: the EU heads of government agreed at the EU summit in Brussels in October 2014 that emissions of the climate-damaging greenhouse gas CO2 should be reduced by 40% by 2030 compared to 1990 levels. In Germany, the climate targets were formulated in a much stricter and more ambitious way. Starting with the Meseberg resolutions (see also [1]), EEG 2014 [2] and currently updated in the Renewable Energy Sources Act EEG of 13.10.2016 [3], the goal was formulated to reduce CO2 emissions by 40% by 2020 compared to 1990. About 40 % of these emissions are energy-related, so that an important starting point can be seen here. The COP 21 resolutions are about to be implemented in national plans and laws in Germany.

Energy supply in Germany

Until about 6-7 years ago, energy supply in Germany was strongly characterized by fossil and nuclear primary energies and centrally oriented power plant structures. The nuclear phase-out law [4] of August 6, 2011 ends the nuclear energy era in Germany by 2022. This already entails a severe cut in our energy supply structure, especially for electricity, as e.g. in 2011 about 17.7% of the electricity generated in Germany came from nuclear energy. In this context, the regional component of this phase-out should also be emphasized: nuclear power plants are very much located near centers of consumption in the south of the Republic. If these are decommissioned, other generation plants would have to be built here or electricity would have to be transported there from other parts of the country - e.g., from the north - via high-voltage lines. However, the transmission capacity of the existing transmission lines is currently insufficient for this. For the period after the Grafenrheinfeld NPP is shut down in 2022, high-voltage transmission capacities must be built to supply the south. Bavaria in particular has pushed for underground cabling in this connection, but this would entail considerable additional costs in economic terms. Also a completion is not to be expected before 2025.

You could lead now that straight in the south the development of the renewable energies was strongly advanced - wind energy in Baden-Wuerttemberg and Photovoltaik current production (PV) in Bavaria - in order to cover regional need. On the surface, this is correct. However, since wind and sun are not always available, a secure supply of electricity must be provided for these periods. In Germany, periods of up to 10 days without significant wind and solar power feed-in must be expected. In these periods it does not use also to increase the generation capacities simply only - figuratively beside a wind turbine a further to set -, because then evenly both wind turbines do not turn and feed no river in.

A secured current offer can be manufactured also only conditionally by a net development, since there are - related to Europe - regional differences in the wind and sun presentation, these are not sufficient however, in order to cover our deficits. Incidentally, a Europe-wide energy transition should be carried out under the premise that individual countries should not try to cover their share of green electricity by importing from others. This would be an inadmissible sleight of hand.

Another possibility is the expansion of electricity storage facilities. Hereby the current produced at times of high wind and/or solar power supply in the surplus could be stored in and at the "correct" time again be stored out. According to estimates by some research institutions, which have summarized their results in studies and which were published in a representative VCI paper [5], an electricity storage capacity of 10-20 TWh (10,000 to 20,000 GWh) is needed for Germany to stabilize the grid. This compares to current pumped storage capacity of 20-40 GWh, about a factor of 500 less than required. This alone shows that conventional storage alone cannot meet this challenge. Only chemical storage, in which electricity is converted by electrolysis into hydrogen or - with a further step - into methane, stored and later reconverted into electricity, could provide such a capacity. This technology pathway is known as "power-to-gas," but is still one to two decades away from large-scale deployment [6].

CO2 savings targets

In addition to the energy industry, sectors such as heat and transport will also have to contribute to a much greater extent to achieve CO2 savings targets. If one relies on strong electrification here, then this requires a much stronger expansion of RE generation capacities and this in the next 5 to 10 years. However, such a forced expansion again increases the requirements for a dispatchable power supply to ensure the residual load.

In the end, the existing power plant park, in which essentially fossil energy sources such as natural gas, hard coal and lignite are used to generate electricity, can be used. Natural gas has the lowest specific CO2 emission values - these are about a factor of 2 lower than those of lignite. Hard coal is in between with a value of approx. 840 (735 to 939) kg CO2/MWhel. After that, natural gas-fired power plants, e.g. combined cycle plants with an electricity generation efficiency of over 60 %, perform best from a technical point of view. However, in the current "energy-only" market, these plants are only used at very few hours of the year due to the "merit order" principle. This can be explained by the fact that the price of natural gas is roughly equivalent to the generation costs of coal-fired power. If one takes into account an average efficiency in gas-fired power generation of 50%, electricity from natural gas becomes about twice as expensive as generation from coal.

Technically and economically, this means that coal-fired power plants are currently the only plants with which secure and dispatchable power generation can be realized. Hard coal production will be abandoned in Germany by 2018, but a global provenance (origin or availability) of coals and a stable world market ensure stable prices and geostrategic supply independence in the long term. Hard coal prices have fallen even further in the last two years under the influence of the extraction of low-cost unconventional gas in the USA. In this context, lignite is the only domestic energy source.

The power plant fleet has been reduced in capacity from about 120,000 MW of installed capacity to less than 90,000 MW, essentially decommissioning older plants and thus making a not inconsiderable contribution to environmental protection and also to CO2 reduction. These plants are very load-flexible or could be upgraded for this purpose at a manageable cost. In this context, flexibility means being able to ramp up or ramp down the power plants very quickly in order to cover the residual load, i.e. the difference between the required grid load and the generation from renewable energies. Only under the given market conditions, there is almost no willingness to invest in upgrading these plants, although this would be urgently necessary.

Conclusion

In summary, it can thus be stated that we have a very stable electricity interconnected system in Germany, which is also an essential component of a European interconnection. Renewable energies already have a not insignificant share of electricity generation in Germany (2016: over 34%; for the first time, RE has the largest share of gross electricity generation in D) and this will also continue to increase significantly in the coming years and decades. Such a development is also highly desirable for climate protection reasons. The speed of the transition from fossil to renewable power generation alone is too ambitious due to purely politically motivated targets, and there is no master plan that specifies the shares of the various energy sources for power generation along the way. The imponderables and uncertainties at both the technical and economic levels are too great. It would therefore be irresponsible to phase out coal in addition to phasing out nuclear energy. Such a double paradigm shift would overtax us both technically and economically. We will therefore continue to rely on coal for power generation in Germany for some time to come. Worldwide, we build and offer the most efficient coal-fired power plants. Globally, there is a strong reliance on coal and also from this point of view it would be negligent not to export our highly developed power plant technology to countries such as China and India, but to build plants there with significantly lower environmental standards.

Literature:

[1]    Meseberg Resolutions: Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety (BMUB), August 24, 2007, retrieved March 16, 2014. [2]    Renewable Energy Sources Expansion Act 2014, entered into force on August 01.2014 [3]    Act on the Introduction of Tenders for Electricity from Renewable Energies and on Further Amendments to the Law on Renewable Energies (Renewable Energies Act EEG 2016), entered into force on 13.10.2016 [4]    13th Act Amending the Atomic Energy Act (Atomic Energy Phase-out Act), entered into force on 6.8.2011 [5]    Future of energy storage - an interim report by the German Chemical Industry Association (VCI). VCI, 8.10.2013 [6]    Virtual Institute: electricity to gas and heat - flexibility options in the integrated electricity-gas, heat system. Brochure of the Cluster Energy Research NRW (CEF.NRW), 2014