Fuel cells play a pivotal role in energy supply. They are the key technology for converting a fuel, whether hydrogen or methanol, back into electricity. In this way, energy is made transportable on the one hand and available on a decentralized basis on the other. The whole thing works powerfully, efficiently and in an environmentally friendly manner. The latter above all because fuel cell technology emits no nitrogen oxides (NOx), carbon monoxide (CO) or particulate matter. The byproduct of both hydrogen fuel cells and direct methanol fuel cells is primarily heat. And this can also be put to the best possible use. Through power-heat cogeneration. Power-heat-what? Power-heat coupling! Or heat-power cogeneration – this is a much less familiar term. What is it all about? This text provides the answer – and much more. Because cogeneration has many facets and is just as versatile as the associated fuel cell. Here we go: Combined heat and power coupling simply explained.
Cogeneration is a process in which electricity and heat are produced simultaneously through what is known as coupling. Unlike the combustion engine in a car, however, the waste heat is not lost in cogeneration. It is fed into a connected – as the name suggests – coupled heating system. The advantages are obvious: cogeneration systems work more efficiently because they get twice the benefit, so to speak, from the fuel they require. Seen in this light, electricity and heating technologies are growing much closer together on the road to a greener future with a more sustainable energy supply. Combined heat and power also plays a decisive role in the considerations of many state governments in order to be able to use energy even more efficiently and sustainably. However, in order to make this development a success, the fossil fuel-based cogeneration systems used to date must be replaced. But how exactly does cogeneration work?
One of the best-known combined heat and power systems is called combined heat and power unit. As mentioned, this cogeneration function not only provides decentralized energy, but also ensures that the heat is not lost. It consists of an internal combustion engine powered by oil or gas, which drives electricity via a generator. Systems that rely on a fuel cell are also becoming increasingly popular. Here, the fuel cell replaces the fossil combustion engine for an even more efficient form of electricity and heat generation. The waste heat released during combustion – which in the case of the fuel cell is cold combustion – is captured and transferred to the heating system via a buffer tank. This increases the efficiency of mechanical power generation. Conventional power generators often only achieve efficiencies of up to 40 percent. This means that they are only able to use 40 percent of the energy present in the fuel (oil, gas). Combined heat and power plants, on the other hand, are true efficiency wonders. They achieve efficiencies of 95 percent and more1. Through the combined generation of electricity and heat, i.e. smart cogeneration, they can use almost all the energy in the fuel.
It should be noted that with cogeneration in a combined heat and power plant, the generation of electricity and heat are roughly in a ratio of one to three. With an electrical output of one kilowatt, the heating system in the house can use a thermal output of about three kilowatts. The high efficiency of cogeneration saves costs. And the state even subsidizes the installation and use of a combined heat and power unit, i.e. a cogeneration plant. In contrast to the heat produced, the electricity generated within one’s own four walls can be fed into the public grid. Operators of combined heat and power plants thus benefit from several subsidy options. The so-called Combined Heat and Power Act provided for a temporary surcharge payment. Until the end of 2020, private individuals could submit applications for subsidies for combined heat and power plants. The subsidy was based on the electrical output of the cogeneration plant. However, under the Mini Cogeneration Plant Directive, the limit of eligible plants is 20 kilowatts electric (kWel). Although private individuals will no longer be able to submit new applications for cogeneration subsidies to the Federal Office of Economics and Export Control as of January 01, 2021, there are other options.2
Homeowners who want to renovate their property in an energy-efficient way can take advantage of low-interest loans from the Kreditanstalt für Wiederaufbau (KfW). To do so, applicants must meet a number of requirements in order to be able to use the fuel cell in the combined heat and power system. As part of its own program, KfW provides funding of 28,200 euros per fuel cell in the 0.25 to 5.0 kW electrical output class for installation in a new or existing property.3 The electricity generated by the system can be self-consumed or fed into the grid. Sounds strange at first, but it may be a good deal for many homeowners.4 Based on the KWKG, people who feed electricity into the grid receive 0.254 cents per kilowatt hour (kWh/as of 12/2020).5 Since the framework conditions change continuously, the KWKG is adjusted annually. One thing, however, has endured. With the CHP levy, the state finances a central component of the energy transition: The replacement of coal as a fuel for the simultaneous generation of electricity and heat with gas and renewables.
This conversion is a prerequisite for being able to end coal-fired power generation as planned by 2038 at the latest. The German government has also set itself another important goal: to reduce climate-damaging greenhouse gases by 80 to 95 percent by 2050. Fuel cell systems for stationary applications are already making a significant contribution to this and have key technology potential. They produce electricity continuously and efficiently – without climate-damaging emissions. If hydrogen or synthetic natural gas is used as the fuel, CO2 savings can be as high as 100 percent. The German government has also recognized the inexhaustible potential of fuel cells and is not only promoting their use in combined heat and power plants. At the same time, with the National Hydrogen Strategy, it has confirmed that H2 and the associated fuel cell technology, in their function as a key technology, are the means of choice to successfully finalize the energy transition. As a fuel cell pioneer, SFC Energy has been shaping this development since the very beginning and will continue to make its contribution to a greener power supply. Here you can find more products and applications of the EFOY fuel cell by SFC Energy.
1 Solar Energy Research Association: fuel cells in cogeneration an energy option for the future? (Ludwig Jörissen, Jürgen Garche, Bern Rohland…)
3 Credit Institute for Reconstruction https://www.kfw.de/inlandsfoerderung/Privatpersonen/Bestandsimmobilie/Förderprodukte/Energieeffizient-Bauen-und-Sanieren-Zuschuss-Brennstoffzelle-(433)/
4 National Organization Hydrogen and Fuel Cell Technology NOW-GmbH.
5 BDEW, German Association of Energy and Water Industries: https://www.bdew.de/presse/presseinformationen/umlage-nach-kwk-gesetz-bleibt-2021-nahezu-konstant/