What role is there for heat pumps?
Heat pumps make use of the heat naturally available in the environment. They are therefore one of the most appropriate solutions for increasing the proportion of renewable energy and energy efficiency in all applications that require heat. As such, they will play an increasingly important role in heating buildings and industrial processes.
A heat pump is a device that transfers heat from a cold environment to a warm environment, for example from a basement at 11°C or a lake at 5°C to a building at 20°C. As a result of this heat transfer, the basement or lake will cool down a little more, while the building will warm up. Refrigerators are heat pumps that continuously extract heat from the interior compartment to keep it cold. This heat is vented to the outside, resulting in the flow of warm air usually located at the back of the refrigerator.
Naturally, the heat flow always goes from hot to cold (the fire warms the room, not the other way around). In order to force the heat to flow in the opposite direction - i.e. from cold to warm - the heat pump needs an energy input. This is usually electricity (as in the case of a refrigerator that is connected to the mains), but it can also be high-temperature heat (typically above 150°C) such as that provided by burners or waste heat. The efficiency of a heat pump is measured by its coefficient of performance (COP), which expresses the ratio between the amount of heat it can provide and the amount of energy consumed to operate the system. The higher the COP, the more efficient the heat pump will be. For example, a COP of 3 for an electric heat pump indicates that it will provide 3 kWh of heat for every 1 kWh of electricity consumed. The smaller the difference between the cold source and the environment to be heated, the higher the COP [→ Q60].
Heat pumps make use of the heat naturally present in the environment, in the ground, in the air outside and in the water. As most of Switzerland’s large cities are located close to a lake or river, the development of district heating networks powered by heat pumps should help to substantially reduce heating energy consumption and emissions in urban areas. In addition, all buildings have foundations in the ground and can therefore extract heat from the ground or even store excess heat [→ Q77]. This also applies to parking lots, tunnels or any other work in contact with the ground.
Heat pumps can also use waste heat, i.e. recover heat from exhaust air, sewage water, etc. What’s more, because of their versatility, they can be easily combined with other energy equipment, thus increasing the overall efficiency of the system. Here are three examples:
- In combination with combined heat and power units [→ Q27], heat pumps reduce fuel consumption by 40 to 60%.
- Heat pumps supplied with electricity by photovoltaic panels can compete energetically and economically with solar thermal systems [→ Q50].
- Heat pumps can be used to raise the temperature of industrial waste heat to the point where it can be used in the manufacturing process. This can reduce the size of the boiler used to provide heat for the process.
Given their many advantages, it is clear that heat pumps will play a major role in the energy transition in Switzerland and elsewhere.
- Favrat, Maréchal & Epelly (2008)
- Favrat, D., Maréchal, F. & Epelly, O. (2008). The challenge of introducing an exergy indicator in a local law on energy. Energy, 33(2). 130–136.
- Favrat (2006)
- Favrat, D. (2006). Services énergétiques du futur. GWA (Gas, Wasser, Abwasser), 86(5). 383–388.
- Favrat (2006)
- Favrat, D. (2006). Efficacité énergétique, moteur de l’évolution technologique. Les cahiers de l'énergie, 64. 30–32.
- Favrat (2005)
- Favrat, D. (2005). Pour une meilleure conception des systèmes énergétiques. GWA (Gas, Wasser, Abwasser), 3. 183–190.
- Favrat (2007)
- Favrat, D. (2007). Pompes à chaleur en constant progrès. Les cahiers de l'énergie, 65. 44–47.
- Favrat, Daniel (2012)
- Favrat, Daniel (2012). 20 ans de contribution du LENI-EPFL à la recherche sur les pompes à chaleur, presented at the 18. Wärmepumpentagung von BFE-Forschungsprogramm “Wärmepumpen und Kälte”.
- Favrat, Daniel (n.d.)
- Favrat, Daniel (n.d.). Progress and perspective in heat pumping technology and applications.
- Pelet, X and Favrat, D and Voegeli, A (1997)
- Pelet, X and Favrat, D and Voegeli, A (1997). Performance of a 3.9 MW ammonia heat pump in a district heating cogeneration plant: Status after eleven years of operation. Compression systems with natural working fluids, IEA Annex, 22.
- Zehnder, Michele and Favrat, Daniel (2005)
- Zehnder, Michele and Favrat, Daniel (2005). Experiences with hermetic scroll compressors with intermediate vapor injection port in heat pumps for high temperature lift heating applications.