EW-I-3: Ambient temperature-induced power reduction in thermal power plants

The picture shows a riverbed that has almost dried up and is lined with rows of trees. A cooling tower rises in the near background.Click to enlarge
Hot and dry summers may give rise to difficulties with the abstraction or discharge of coolant water
Source: Photograph: © Markus Volk / stock.adobe.com

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents

 

EW-I-3: Reduced power generation due to ambient temperature in thermal power plants

Heat and drought can restrict electricity generation in thermal power plants by impairing the degrees of efficiency or as a result of problems with coolant water abstraction or the discharge of coolant water into water courses. Although the hot summers of 2003 and 2006 resulted in striking deficiencies, a significant trend has so far not been discernible. Detailed data for 2018 have not yet become available.

A bar chart shows the ambient temperature-related electricity production of thermal power plants in gigawatt hours in a time series from 2001 to 2017. The values fluctuate between less than 100 gigawatt hours for 2002 and 2,500 gigawatt hours for 2003. From 2007 onwards, the values become comparable and range between 300 and 1,000 gigawatt hours. There is no trend so far.
EW-I-3: Reduced power generation due to ambient temperature in thermal power plants

A bar chart shows the ambient temperature-related electricity production of thermal power plants in gigawatt hours in a time series from 2001 to 2017. The values fluctuate between less than 100 gigawatt hours for 2002 and 2,500 gigawatt hours for 2003. From 2007 onwards, the values become comparable and range between 300 and 1,000 gigawatt hours. There is no trend so far.

Source: VGB PowerTech e.V. (non-availability-module of power plant-information system KISSY)
 

Heat impacts on electricity generation in conventional power plants

In recent years, the energy transition associated with phasing out nuclear and coal-fired energy production, has resulted in thermal power plants becoming less important in the energy system. Its role will decline further for years to come. By contrast, renewable energies were able to increase their share of gross electricity consumption to almost 38 %.54

Despite the considerable increase in the contribution of renewable energies to electricity supply in recent years, thermal power plants will continue to play an important role in the German energy supply system for some time.

Owing to their operating principle, thermal power plants depend on the discharge of process heat by means of cooling. Usually, in water-rich Germany water is used for cooling purposes. In the case of freshwater cooling systems the water abstracted from a river is cooled down either directly by means of continuous-flow cooling or fed back into the water course after the cooling process in a cooling tower (drainage cooling). Circulatory cooling systems require a distinctly smaller supply of water from water courses.

If ambient heat and drought prevent process heat from being discharged in sufficient quantities, the degree of efficiency of cooling systems and thus also of power plants declines. Above all however, low water levels and increased temperatures in water courses may trigger the imposition of legal restrictions on water usage. These regulations stipulate how much freshwater for cooling purposes may be abstracted from water courses and to what extent and at what temperature heated coolant water is permitted to be discharged back into the water course. This can mean that in hot weather and drought conditions, the operator has no option but to reduce electricity generation in the power plants in question or even to cease production entirely.

In recent years, the hot summers of 2003, 2006 and 2018 have demonstrated the consequences that electricity generation may be exposed to as a result of heat and drought. In 2018 there were not just problems owing to temperature-related restrictions on the availability of coolant water; there were also difficulties with the supply of coal, as low water levels restricted the availability of transport.

In 2003, 38 nuclear power plants were forced all over Europe to cut their electricity generation during the summer heat. In Germany this applied e.g. to power plants in the Isar and Rhine basins. In 2006, there were restrictions to electricity generation owing to coolant water temperatures in thermal power plants on the banks of the rivers Weser and Elbe. In those years, the competent water authorities had to grant exemptions from legal regulations in some cases in order to safeguard the reliability of supply.

The time series on restricted electricity supply illustrates the amount of electricity which thermal power plants were unable to generate owing to temperature-related external influences. This illustration is based on data regarding just under two thirds of the installed capacity of thermal power plants in Germany. So far, the most incisive restrictions were recorded in the hot summer of 2003. In that year thet deficit in electricity generation totalled 2.6 terawatt hours.

54 Pressemitteilung des UBA: Bilanz 2018 – Anteil erneuerbarer Energien steigt auf 16,6 Prozent
www.umweltbundesamt.de/presse/pressemitteilungen/bilanz-2018-anteil-erneuerbarer-energien-steigt-auf

 

Interfaces

EW-R-4: Water efficiency of thermal power plants

 

Objectives

Increasing the safety of supply especially in cases of extreme events by complementary decentralised and diversified generation structures which include renewable energies (DAS, ch. 3.2.9)

Determining and assessing potential supply risks and establishing measures for the reduction of any such risks (DAS, ch. 3.2.9)