_ Frank Hennig, graduate engineer, expert for power plants, author. Munich, May 2, 2021.
Problems of the German energy transition
The prerequisite for the use of electricity in a power grid is a stable balance between generation and consumption, which is characterized by a frequency of 50 Hertz. Therefore, the emerging energy storage issue cannot be dealt with in isolation from other issues relating to the German energy transition.
In the balanced relationship between production and consumption, only network losses occur. The intermediate storage of electricity requires expenditure and running costs. Storage systems do not add value and have a negative impact on efficiency. Therefore, the immediate use of electricity is preferable to its storage. From an economic point of view, the expansion of the electricity network is therefore preferable to the construction of energy storage facilities.
The German energy transition is taking place from a CO2-centered point of view and neglects two essential points of the energy policy target triangle: supply-side security of supply and economic efficiency.
At the beginning of 2021 it becomes clear that the federal government does not have a master plan that would secure the timely replacement of the conventional power plant capacities that are to be shut down. Therefore, from 2023 imbalances in the form of insufficient coverage of the electricity demand are foreseeable in Germany, especially in the area south of the Main line, the so-called “south zone”.
A study by the University of Stuttgart and the German Aerospace Center (DLR) examined the country’s power balances in 2018 and found that there were “still” sufficient generation capacities for the period up to 2025. However, the supply capacities of German lignite power plants and imports were still included in this estimation. Unfortunately, the expected import volumes, which will primarily come from nuclear, coal and hydropower, are not contractually secured between Germany with the other EU member states and non-EU third parties.
The German Solar Industry Association (BSW) is assuming a power generation gap as early as 2022. A peak import demand of 30 gigawatts (GW) is forecast for 2023.
The domestic electricity supply in Germany will decrease as a result of the nuclear and coal phase-out. In connection with the decreasing supply, electricity prices in the wholesale trade will rise driven by the market. Energy-intensive industry in particular is burdened by additional network costs. This development can already be seen in the greater Hamburg area. The cause is the shutdown of the Krümmel, Brunsbüttel, Moorburg and, in future, Brokdorf power plants.
In northern Germany, too, there will be no more excess capacities in the foreseeable future. Wind energy will only temporarily generate a larger amount of electricity and it is unclear who will secure the large north-south power lines in the future.
The nuclear phase-out requires the replacement of this low-emission and controllable energy generation. In 2019, 75 terawatt hours (TWh) of nuclear power were still being produced in Germany. In relation to the 125 TWh of wind power, replacing the lost nuclear power with wind power would require the additional operation of around 18,000 wind power plants, only considered as an annual average and without taking into account timely production. This would not replace a single kilowatt hour of electricity from coal. By 2023, almost 15,000 megawatts of secured capacity will be taken from the grid across Germany.
Especially southern Germany is not in a wind suitable area. In the south and east of the region, the average wind speeds at a height of 150 meters are 3 to 6 meters per second. The switch-on speed of the systems is two meters per second. Excessive expansion of wind power, especially in southern Germany, does not make economic sense and does not generate any significant amounts of electricity as a yield.
Realistic and unrealistic power storage options
In order to avoid times of undersupply in the power grid, it would be possible to store electricity as ambient energy when there is high electricity production, instead of selling or exporting it at low to negative prices. The available technologies can be used for short and medium-term storage, i.e., in the range from seconds to a few days. The conversion of electricity production from secure, needs-based generation to meteorological and time-of-day-dependent and thus volatile generation would require inter-seasonal storage, i.e., shifting the summer energy surplus into the winter months. There is currently no economically viable technology for problem.
There are various proven methods of storing electricity. A distinction is made between mechanical, chemical, electrical, thermal and, more recently, virtual processes. The optimal variant has emerged for each area of application.
Pump storage plants have existed for large-scale technical applications for around 100 years. They represent the largest capacity today (40 gigawatt hours (GWh) with around 7 GW of storage capacity), are technically mature and reliable with an efficiency of over 70 percent. They are particularly suitable for load balancing over periods of hours to a few days and could theoretically take over supplying Germany for about half an hour at the moment. There are regulatory, economic, and political obstacles to further building such plants. New investments are unlikely.
Other mechanical storage methods such as compressed air, flywheel or ball pump storage are unsuitable for large-scale use.
Battery technologies have recently become a bearer of hope for the energy storage dilemma. However, their electricity storage costs are high. Their suitability lies above all in ultra-short periods of time, which makes them ideal for providing primary control power in the network. The effects of chemical aging caused by the numerous loading and unloading processes are still unclear.
The use of many individual batteries as swarm storage on the way of the V2G (Vehicle to Grid) is also far from being effective. There is a lack of sufficient e-mobiles on the German market and the willingness of electric vehicle owners to make some of their battery capacities available to suppliers is uncertain.
Swarm storage in the form of domestic basement storage can help smooth the daily electricity cycle and also offer a cost advantage for the owner. However, they cannot even begin to compensate for the large fluctuations in solar and wind power feed-in (currently around 50 GW with a rising trend).
At the moment, hydrogen is named the main solution for electricity storage. However, hydrogen is not an energy resource, but an energy carrier. It is versatile in terms of energy and material and can be easily stored in the gas network. In addition, Germany has almost 50 large gas storage facilities. Hydrogen must be produced using energy, for which there are various technologies and energy resources (Tab 1.).
Tab. 1. Hydrogen production by production type and CO2 intensity
|Hydrogen “colour” code||Production type||CO2 intensity
|Black||from petroleum or coal||very high
|Gray||from natural gas, by steam reformation||high|
|Blue||from natural gas, with CO2 capture||medium|
|Turquoise||from natural gas, by thermal fission (pyrolysis)
|Yellow||from natural gas, by nuclear power electricity electrolysis
|Red||from natural gas, by pyrolysis wit HTR nuclear power
(high temperature reactors)
|White||from natural occurrences (low occurrences)||low
|Green||from natural gas, through green electricity electrolysis||low|
Source: Compiled by the author.
Production using green electricity electrolysis is the most expensive process. According to BASF, 10 megawatt hours (MWh) of energy are required to produce one ton of turquoise hydrogen with methane pyrolysis, and 55 MWh for green hydrogen. The costs of green hydrogen are correspondingly higher. Electrolysis also requires around 9 liters of fresh water per kilogram of hydrogen.
Green hydrogen is unsuitable for storing electricity. The P2G2P process chain achieves an overall efficiency of around 25 percent. So it is not a storage, but a waste of natural resources.
The availability of very high (and also cheaper) quantities of green electricity for mass hydrogen production does not exist in Germany. This is why the federal government’s hydrogen strategy focuses on imports, but these are unclear with regard to future dates, quantities and prices. In addition, there are restrictions regarding the fact that electricity generated from renewable sources must also benefit the producing country (energy colonialism must be ruled out) and possible foreign policy differences, such as currently with Morocco.
The Renewable Energy Sources Act (EEG) puts electricity storage at a disadvantage. It is treated as a consumer, which has to pay grid fees and levies for electricity storage. The EEG only promotes the expansion of generation plants, especially random feeders such as photovoltaics and wind power.
Electricity storage systems can currently become more economical due to greater price fluctuations in electricity and the associated high prices that occur at times of shortages.
There will be no private investments in large storage facilities in the legally unreliable environment of the energy transition. Foreign investors in particular will not be inclined to be involved in Germany’s energy sector outside of the subsidised areas.
If the goal is “100 percent renewable”, it is long overdue to give the producers of renewable energy also system responsibility.
In 2020, the Greens politician Hans-Josef Fell and the Energywatchgroup proposed tying the feed-in tariff to constant or controllable output and promoting so-called combined power plants that produce according to demand. This is the only feasible way to control the escalating system costs and avoid electricity storage.
At the same time, the regulations have to be changed in favor of electricity storage systems in order to possibly find private investors.
If this does not succeed, the only option is to make greater use of other flexibility options. This would mean financing electricity storage, as well as reserve power plants, special network-related equipment, the security readiness of power plants, the so-called network boosters and the network expansion through levies, fees and tax money. This would be the next step towards a state-regulated and organized energy industry in which market approaches no longer exist at all.
Various model calculations for the storage requirements of an electricity system based primarily on wind and solar power result in the enormous capacities required. A five-day perion when solar/wind power generation is very low would require a storage power supply of around 8 TWh. Currently less than 0.05 TWh are available. A 120-fold increase in current capacities would be necessary. At the same time, significant excess capacities from volatile producers would be required to fill the storage facilities.
Small-scale storage in the basements of households is possible, but their total capacity is limited.
In addition to the expansion of storage facilities in the basements, a limited flexibility potential can be increased in the short term through combined heat and power (CHP). In contrast to electricity, heat can be stored well and with little loss. The use of heat storage in CHP systems enables a more variable distribution of energy depending on demand in the direction of heat or electricity.
The large-scale use of low-emission hydrogen is not calculable in view of the questionable quantities and prices available.
It is conceivable to import natural gas to which hydrogen is added that has already been produced with low emissions. Gazprom wants to build such an infrastructure and produce turquoise or yellow hydrogen, which is also low in emissions, but cheaper than green hydrogen. Pipeline transport has also a clear advantage over the transport of highly compressed and deep-frozen hydrogen or methane by ship.
There is the possibility of using flexibility options in the network operation. On the one hand, electricity can be imported within the European electricity grid. In view of foreseeable bottlenecks, long-term contracts should be concluded with foreign suppliers so as not to be exposed to the sometimes violent price fluctuations on the spot market.
On the other hand, demand site management (DSM) can have a smoothing effect. Regulations for smoothing peaks in the load profile could initially relieve peaks in consumption on a voluntary basis, later becoming mandatory. This procedure can be designed with comparatively little loss of comfort. An orderly brownout helps prevent a blackout. The aim must be to avoid drastic measures for forced regulation up to and including “load shedding”.
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Image: ifo Institute (2021).