Germany's expansion target for 2030 is quite clear: 115 gigawatts of installed onshore wind energy are envisaged in the recently adopted amendment to the German Renewable Energy Sources Act (EEG). The fact that the necessary annual addition of 10 gigawatts this year has so far fallen far short of expectations is not mentioned there. "The situation with new permits leaves a lot to be desired," the German Wind Energy Association (BWE) said at the beginning of August. The lack of gas supplies from Russia also makes it clear: a quick solution to strengthen renewables in the energy sector is needed.
Wind energy and heat can go hand in hand.
Converting wind power into green heat
When one thinks of renewable energy, the first thing that comes to mind is electricity. Around 50 percent of it – which is a significant share – comes from renewables in Germany. The situation is quite different with heat: Only 15 percent comes from renewable sources. Yet more than 50 percent of the total final energy consumption is for heat. The industrial sector, where process steam and heat are needed for the most part, even accounts for about two-thirds of this. While green electricity is now becoming suitable for mass consumption, green heat is still a rare commodity.
Where wind power volumes potentially affected by curtailment or electricity from de-subsidised wind power plants face a high demand for heat, the solution is simple: power-to-heat technologies with a storage component connect the electricity market with the heat market and thus solve several problems at once.
Lesser down times for wind turbines …
On the side of electricity generation, there is the fundamental problem of volatility. If there are generation peaks that exceed the capacity of the electricity grid, a shutdown of the wind power plant is unavoidable. Through sector coupling, however, these excess quantities can be shifted quickly from the electricity grid to the heating grid. For wind farm operators, this means a huge improvement by maximising wind yields, reducing connection costs and even generating additional revenue through heat supply. The situation is similar for wind farms that continue to be operated after the legally guaranteed "Renewable Energy Law" (EEG) subsidy under German law expires. Here, the operator can also generate stable, electricity exchange-independent revenues by selling excess heat.
… and better use of the capacities …
For grid operators, such a shift serves as a relief. By making better use of existing grid capacities, there is less time pressure on investments in the further expansion of the grid. Without having to wait long for grid expansion, energy yields can already be increased by fully utilising the existing wind power potential. This makes the wind farm business case much more attractive, which should also have a positive effect on the further expansion of wind power plants. Along the way, sector coupling can promote the acceptance and approvability of new projects on site by supplying surrounding industries and communities with green and price-stable heat. This makes it easier for project planers to enable the participation of residents and located businesses.
A power-to-heat storage system serves as a link between renewable electricity and heat. ©LUMENION GmbH
… can make green energy cheaper.
By shifting the generation peaks, the volatility of the feed-in into the electricity grid and thus the need for balancing energy is reduced. Together with the reduced investments in grid expansion, grid fees are thus kept in check and renewable energies become even more affordable for the end consumer.
„A cross-sectoral energy system is the system of the future with which we can reliably cover our demand for heat without losses on the part of wind power.”
Peter Kordt, CEO of LUMENION GmbH
Using peaks to storage renewable electricity as heat
Thanks to an effective use of electricity peaks, larger parts of the demand for heat in the industrial and building sector can be supplied with CO2-free energy. Especially in the industrial sector, heat- and steam-powered processes can thus be further decarbonised and climate targets in companies can be achieved more quickly. An important factor in the shift from fossil fuels is the greater security of supply provided by renewables.
Through electricity-heat coupling, the heating market can also take advantage of particularly favourable electricity prices. This also provides economic incentives to push ahead with the transition towards to a greenhouse gas-neutral energy supply.
Power-to-heat storage provides maximum flexibility
Power-to-heat technologies such as thermal energy storage systems are a particularly useful link between the electricity and heat market. With an efficiency of up to 95 percent, they store large amounts of energy from generation peaks quickly, reliably, and cost-effectively. By separating energy supply and demand, they provide more flexibility in the electricity grid. On the other hand, they guarantee a stable heat and steam supply for energy-intensive industries, as the lack of electricity during off-peak hours can simply be compensated for by the previously stored energy.
Example of a storage system integrated into the heating system of a residential complex ©LUMENION GmbH
A simple loading principle: Fast in – steady out
Usually, these storage systems can be charged in a short time. A resistance heater then converts the electricity fed into the system into heat, which is transferred to the storage core. Depending on the storage material, which can range from steel to salt or sand, it is heated until the maximum storage temperature is reached. Thanks to insulated covers, there are very marginal losses of the energy stored within some days. Nevertheless, thermal energy storage systems were not designed for long-term storage.
Whenever energy is needed, they can be discharged just as easily: The stored heat then passes through to a heat exchanger, which discharges process heat or process steam in a desired temperature for any application. Some of these systems offer the possibility to simultaneous charging and discharging which ensures maximum availability and optimises the use of resources.
An integrable key technology for the energy transition
Thanks to the modular design of these sector-coupling storage solutions, they are individually scalable so that their capacity is linked to the specific needs of customers. As they are usually based on industry-proven techniques, they make it possible to enter new technological terrain while retaining proven industrial processes and infrastructures. The difference to fossil-fuelled boilers: they make it possible to protect the respective business case against rising energy and CO2 costs while ensuring the supply of green, greenhouse gas-neutral energy. Thus, they represent an important key technology for reducing CO2 emissions and make the most effective use of fluctuating wind power possible – in the shortest possible time and not just in 2030.
This Article is part of issue 03-2022 of the current issue of German Wind Power Magazine, the international magazine of the German Wind Energy Association (BWE) about innovations of the German wind industry. You can read the full magazine here, online and for free.