Cogeneration (CHP) is a concept with high returns. If large or small cogeneration plants can be installed in or nearby cities, they can realise a return greater than 90% by using both the electricity and the heat created during the process. Coal-, oil- and gas-fired power plants built far from cities often have a return of only 35-40% because due to the great distance to industry and cities the heat cannot be used efficiently or at all.
Various fuels can be used for cogeneration systems, as shown in the above drawing: both fossil and renewable fuels and also waste products. Larger or smaller cogeneration plants are used mostly for the heat production of district and urban heating systems.
Cogeneration systems are available from 1 to 40,000 kW. The cost per kW varies from 250 euros/kW for large systems to 3100 euros/kW for small systems [Erhorn-Kluttig et al., 2011]. In recent years micro- and mini-cogeneration and gas compression heat pumps have also been developed.
The German “Zuhausekraftwerke” initiative is very interesting. The energy company LichtBlick installs gas-powered cogeneration systems that remain the property of the company in large houses, housing complexes, schools, offices, etc. Homeowners pay for their energy use and receive a significant discount. The electricity that is produced is delivered to the power grid. The homeowner is not inconvenienced by maintenance.
The intention is initially to install 100,000 of these ‘home power plants’. This is equivalent to two large gas power plants. The home power plants are infinitely variable and are a good supplement to an energy supply based on sustainable sources. All of these systems together create a ‘swarm of power’. The home power plants are equipped with a heat buffer that provides the house with the necessary heat for heating and warm water. If the central programming doesn’t work or if there is not enough heat available in the buffer chamber, the system converts to on-site programming.
Recently Volkswagen and LichtBlick have started the development of a smaller plant for individual/single-family homes. [LichtBlick, 2012]