We don’t want to freeze in winter. Most of the heating systems worldwide still run on coal, oil, or gas. But this creates a lot of CO2 and this heats up the climate. What are the alternatives for the future?
Heating with coal, oil, and natural gas causes around a quarter of global greenhouse gas emissions. That can be changed, says Wolfgang Feist, founder of the Passive House Institute in Darmstadt: “Buildings can be supplied in a climate-neutral way and that can be done with renewable energies worldwide”
It is particularly useful to make the buildings fit so that no energy is wasted. “With good insulation and ventilation systems, compared to conventional buildings, 80 to 90 percent energy can be saved in new buildings and 75 to 80 percent in old buildings through energy-efficient renovation,” Feist told DW.
The remaining demand can then be met from a mix of renewable energies. This can vary depending on the region, says the professor of building physics, and a pioneer in efficient construction. “I see district heating with renewable energies and heating with environmental heat and a heat pump as important sources.”
The use of wood or wood pellets is also a way to meet the heat requirements for individual buildings. However, this is “not a sensible option for the complete heat demand of cities and industries,” emphasizes Feist. Because that is not sustainable, the demand for biomass would be too great.
Frankfurt wants to become climate neutral
In order to become climate neutral by 2050, the city of Frankfurt is using various technologies, explains Paul Fay from the city’s energy department. He coordinates the renovation, for which the city has drawn up a master plan together with scientists. This includes efficient passive houses and the energetic renovation of old buildings in the city.
Frankfurt wants to generate part of the required heat energy with solar power on the roofs, another part is to bring district heating pipes into the city quarters. There, heat is to be fed in that arises from the burning of waste and wood or comes from computer centers as waste heat. Environmental heat from the ground can also be used with the help of heat pumps.
How does a heat pump work?
In principle, a heat pump works like a refrigerator. In a closed multi-stage system, heat is generated in a compressor and cold in the evaporator.
A liquid coolant removes heat from the environment in order to heat buildings or water. The heat pump draws the energy from the ground, groundwater or air.
Heat pumps need electricity to drive them, their output depends primarily on the heat source.
“We examined 60 heat pump systems in older buildings in Germany,” says researcher Marek Miara from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. The result: “In the older buildings, heat pumps with air as the heat source generate an average of around three-kilowatt hours of heat from the one-kilowatt hour of electricity. And heat pumps with groundwater and soil as the heat source generate an average of 3.9 times as much heat,” Miara told DW. Systems in new buildings are more efficient.
Key technology with strong growth
Heat pumps are a very central component in the scenarios for climate-neutral energy and heat supply. Worldwide, heat pumps are now replacing more and more fossil heating systems. “We see a very positive trend globally. We are experiencing a golden age for heat pumps, it will be a mass-market,” says Thomas Nowak from the lobby organization European Heat Pump Association (EHPA). According to the EHPA report, 18 million heat pumps were sold worldwide in 2018, 1.3 million of them in Europe. Worldwide sales increase by ten percent annually.
Less CO2 with a heat pump
In Europe, heat pumps have so far been very widespread and popular, especially in the Scandinavian countries. In these countries, electricity is already generated primarily by climate-friendly wind and hydropower. According to calculations by Fraunhofer ISE, heaters with heat pumps in Sweden generate around 90 percent less CO2 emissions than heaters with natural gas.
In the EU and many other countries around the world, a lot of electricity is still generated with coal and gas. But according to calculations by the Fraunhofer researchers, heat pumps are also more climate-friendly there than heating with natural gas. On average in the EU countries, the CO2 saving effect compared to natural gas heating is around 60 percent and in Germany around 30 percent.
If electricity is becoming increasingly climate-friendly through the expansion of wind and solar power, as is currently the case in Germany, the CO2 saving effect for heating with a heat pump will continue to grow.
If the drive power comes from 100 percent renewable energies, heating with heat pumps becomes climate neutral.
The heat transition needs politics
Energy and building experts agree that it is possible to switch to climate-neutral heating technology in all buildings and in the industry worldwide. “However, there is still a lot of training required. Craftsmen, architects and builders often lack the knowledge of how everything can be optimally coordinated and how much energy and money can be saved,” said Andreas Nordhoff in an interview with DW. Nordhoff is a consultant for passive house technology and also trains architects and craftsmen.
Politics is also important for climate-friendly heat supply. “What we need now is a ban on new oil heaters. These are particularly harmful to the climate and therefore the new installation must be prohibited from now on,” says Nicolas Besser, project manager for energy and climate protection from the German Environmental Aid (DUH). “Compared to oil heating, heating with natural gas is somewhat more climate-friendly but also climate-damaging. That is why we also need a ban on installation and that from 2025”.
In order to achieve climate goals, the DUH is calling for an immediate climate protection program for buildings. With financial support, buildings were to be renovated, municipal heating networks expanded, and the exit from oil and gas heating accelerated.