In addition to its emphasis on the generation of electricity by wind and solar, a key role for thermal energy in Germany’s transition away from nuclear- and coal-generated electricity is confirmed in “12 Insights on Germany’s Energiewende,” published by Agora Energiewende, a joint initiative of the Mercator Foundation and the European Climate Foundation. From the introduction of the report:
“In June 2011 the German Parliament ended a long debate of several decades over the future of the country’s energy system with a historical decision. It was historical because of its ambitious goal: Germany wants to transform its power sector from nuclear and coal to renewables within the next four decades. The decision was also historical because it was an almost unanimous vote, a consensus of ruling and opposition parties. This transition of Germany’s energy system is called Energiewende. Germany will phase out nuclear energy; the remaining nuclear power plants will be gradually closed down by the end of 2022.”
The following is extracted from the sixth chapter of the report, “Insight 6: Integration of the Heat Sector Makes Sense”:
The heat sector offers enormous potential for increasing system flexibility. As the power system is adapted to the fluctuating output from wind and PV power, it is important to keep in mind its interaction with other energy sectors. In the future, the heat sector will play a pivotal role in the transition of the power system. There are three reasons for this:
By 2020, Germany´s consumption of thermal energy will be double that of electricity.
1. Energy consumption for heating is twice as large as for electricity; gas and oil must (almost) entirely be replaced to achieve emission targets. Total energy consumption in the heat sector in Germany is twice as large as that in the electricity sector (See Figure 8). To meet Germany’s official targets for greenhouse gas reduction – 80% to 95% by 2050 – energy consumption for heating must decrease and renewables must replace oil and gas in heat genera-tion almost entirely. Due to the limitations of biomass, biogenic fuels are likely to assume only a small share of that burden. In the long run, both the heat sector and the transportation sector must increase their utilization of electricity from wind and PV.
2. Heat is easy to store – contrary to electricity. Unlike electricity, heat is easy to store. Heat for homes (warm water and interior heating) can be stored easily in insulated water tanks at private residences, in city-wide district heating systems, or in decentralized local heating networks. Thermal storage systems like these can supply heat for several hours or days at very low cost. Energy losses are far lower than those associated with power storage. The properties of heat also extend to cold, which can be stored for short periods at relatively low cost with relatively low levels of energy loss, for example in commercial refrigeration.
In Germany, wind power generation potential is strongest during winter months, when the need for heating is greatest.
3. Most heat is needed in winter, when winds are strongest. Most of Germany’s heating needs arise from October to April. These are also the months in which winds – and wind power – are strongest (see Figure 9). This is an advantageous correlation, as electricity from wind is likely to be the least expensive source of energy for Northern Europe.
CHP plants already provide a link between the electricity and heat sectors; in the medium term, dual-mode heating systems, capable of using either fuel or electricity will be deployed; over the longer term, integration will occur by using a common fuel – natural gas, biogas, or power-to-gas.
Combined heat and power plants (CHP) produce both heat and power and already provide a link between the electricity and heat sectors. While operation today mostly follows the demand for heat, these facilities can be easily upgraded to be responsive both to demand for electricity as well as demand for heat. This upgrade is done by the addition of a thermal storage system – if there is little demand for heat, but only for power little wind) the plant produces power and stores the heat. This approach is already being used by municipal utility companies (Stadtwerke) and other electricity producers. Facilities in Flensburg, Lemgo, and Hamburg are already considering installation of, or have installed such power-to-heat systems.
In the medium term, dual-mode heat systems will be used. Such systems link the power and heat sectors and provide a high degree of flexibility by producing heat either with fossil fuels or with electricity. At times of high power production from wind and sun these systems use electricity to generate heat, taking advantage of the low power prices. When wind and sunlight levels are low, and power prices are high, they use natural gas or oil instead.
Longer-term, both sectors will increasingly be linked by a common and interchangeable gaseous fuel – natural gas, biogas, or power-to-gas. This fuel can be used for centralized or decentralized electricity generation, for electricity and heat generation in CHP plants, or in systems used only for generating heat. The advantage of such a gaseous fuel is that it can be stored over long periods, and an extensive storage infrastructure – caverns, pipeline networks – is already in place.
Read also our latest edition of Hot Cool with focus on Germany including the “Energiewende”