Water availability and heat
As a result of climate change it is expected that summer precipitation will decrease while winter precipitation will increase. Furthermore, more frequent heavy rainfall is expected, especially in winter. At the same time, the temperature will rise in Germany. These changes affect the availability of water in particular.
High temperatures and marginal rainfall may cause a lack of cooling water in thermal power plants, such as coal, natural gas and nuclear power plants. Cooling water is essential for the generation of electricity in thermal power plants if no other cooling systems, such as air-cooling devices are available. In most cases, the cooling water is taken from flowing waters into which warm water is subsequently fed into again.
Long heat waves limit the availability of cooling water. The water volume decreases because of low water levels and rivers warm up with rising air temperatures. Since warmer water has a lower cooling effect, larger amounts of water are needed to reach a cooling effect. In case safety-significant or water law thresholds are met, heated river water may not be used as cooling water. Also the reintroduction of cooling water into warmed up rivers is problematic in terms of the rivers’ ecosystems. For that reason, it is restricted by law. In extreme cases, thermal power plants have to be shut down.
Low water levels in rivers reduce the output of hydroelectric power plants. In addition, low water levels affect the inland waterway transport and thus impede the transportation of fuels such as coal for thermal power plants. This can lead to fuel supply shortages. Heat also affects the efficiency of air-cooling systems of thermal power plants and gas turbines. High summer temperatures can limit the energy production as well as the energy distribution by causing damage to underground cables and transmission losses in overhead lines. During long periods of heat, all these factors can lead to an energy supply shortage. In this respect, conventional energy supply is particularly vulnerable due to its centralised power generation in large power plants. The failure of one or more of these systems can significantly affect the power supply.
Yet climate change can also increase the water level and the flow force temporarily. In mild winters when precipitation is not stored as snow but flows off as rain water instead, the greater flow rate can increase the output of hydroelectric power plants.
Extreme weather events
Climate change can have an impact on the frequency and intensity of extreme weather events. These include floods, heavy rainfall, storms, hail and thunderstorms. Already a single extreme weather event can cause huge damage to the energy infrastructure. Storms and lightning strikes, but also large snow masses (as in Münster in 2005) can damage energy conversion plants and power lines. This can endanger the electricity transmission and distribution. Since the 1970s, supply failures have increased. Increasing temperature decrease the efficiency of photovoltaic modules, which can also be damaged by hail or storm. During severe storms it can be necessary to turn off wind turbines. Furthermore, severe storms can affect the accessibility of offshore wind power plants and damage on- and offshore wind turbines. However, during long-lasting lulls, for example under stable high pressure weather conditions, wind turbines cannot produce electricity. Furthermore, snow layers affect the productivity of photovoltaic systems.
In addition, heavy rainfall and floods affect the operation of raw material and fuel production plants, for example, oil, gas, coal and lignite production facilities. At the same time, floods restrict the inland waterway transport of fuels and the transport on railway lines and roads that run parallel to the rivers. As a result, thermal power plants may suffer from a lack of fuel supply. Floods can also threaten power plants through flooding, including containments, and suspension of plants. High water levels can also affect the electricity production of hydroelectric power plants if the necessary drop height at barrages is reduced. Floods also pose a potential risk to transformer stations, substations and other network components: cable lines can be flushed out, poles can be damaged or water can undermine pole foundations. Floods can also have an impact on the gas and district heating network, for example by flooding transformer stations or gas pressure control systems. Apart from affecting the public energy supply, floods can also impair energy conversion and heating systems in private households. They can cause damage to boilers or power lines. Flooding of electrical components of photovoltaic systems can cause short circuits and thus damage the modules.
Floods can also significantly damage biomass production areas (see also Climate impacts in forestry and agriculture). Heat, droughts, hail and heavy rainfall are other weather conditions that are capable of affecting their output. Potential results are supply shortages and increased energy prices.
As a result of higher temperatures, the cooling demand of households and production facilities increases. Also the transport and storage of goods can increase the cooling requirements. The resulting increased electricity demand can lead to supply shortages, especially during periods of reduced production possibilities, for example during long periods of hot weather. Warmer winters, however, can reduce heating requirements.