Renewable heat

When heat is generated from renewable energy – such as biomass and solar thermal – one speaks of “renewable heat,” but the term can also encompass the recovery of waste heat for heating applications.

Because heat makes up roughly 40 percent of German total energy consumption, the potential for renewable heat is greater than for renewable electricity, since overall electricity only makes up 20 percent of the country’s energy consumption.

Nonetheless, Germany has not had the same success in promoting renewable heat, partly because it has never offered feed-in tariffs for it. The German government has a goal of getting 14 percent of the country’s heat from renewable sources by 2020.

German policies for renewable heat

Under the Renewable Heat Act, all new buildings are required to have a heating system with a minimum share of renewable energy. Unfortunately, this is progressing too slowly – a 2017 study from DENA Germany’s building sector is only projected to decrease its emissions by 67 percent compared to 1990 if renovations and electrification of heating continue as they have so far. It is difficult to make a one-fits-all policy for buildings, because the sector varies so greatly. Likewise, renovations must be accepted and encouraged by the people who live in them.

In addition, there is a lack of political momentum to change the regulations in the building sector such that there is a minimal level of renewable energy for public buildings (attempts to introduce such a measure failed in the German coalition negotiations in 2017).

Renewable heat from biomass

Up to now, most renewable heat has come from biomass, with the most common feedstock being woodchips, firewood, and, increasingly, wood pellets. Germany’s Market Incentive Program also supports the generation of renewable heat from biomass, with strict requirements for efficiency and emissions. In addition, waste heat from biomass units is used in district heat networks. Indeed, Germany’s Renewable Energy Act requires that most biomass units recover part of the waste heat produced in the process of generating electricity (this is called “cogeneration of heat and power“).

Renewable heat from heat pumps and solar thermal

Increasingly, new technologies using renewable energy sources are appearing on the market. In addition to biomass, for instance, there is “shallow” geothermal, in which heat is taken from just below ground or from groundwater. This heat can then be used in combination with heat pumps, as can heat from ambient air. In 2017 a record number of heat pumps – almost 80,000 – were installed in Germany.

Solar thermal collectors can be also installed on homes and businesses to cover demand for heat. At the end of 2017 Germany had 2.32 million solar thermal systems, an increase of 78.000 from the previous year.

In the case of buildings, in particular, the investments in efficiency may offset consumption over decades, but the upfront costs may still be prohibitive. To overcome such obstacles, Germany has implemented a Market Incentive Program (MAP) which provides funding for renewable heat systems such as solar thermal collectors, modern biomass heaters, and efficient heat pumps. Its funding has grown to over 300 million euros.

Solar thermal fails to take off

Nonetheless, this market has not grown nearly as quickly as the PV sector. One reason for solar thermal’s sluggishness is that Germany does not have special feed-in tariffs for solar heat, only for solar power. Solar heat has therefore depended partly on government rebates funded by an eco-tax and emissions trading. Although the cost of solar thermal collectors has decreased, overall system costs have not, partly due to persistently high installation costs.

In addition, the market for solar thermal collectors has been largely restricted to small one and two family house applications. Other countries, particularly Denmark, have favored large ground-mounted collectors, offering five-fold decreased collector prices and competitive heat generation costs. In Germany, even though the systems are supported financially, this market segment has potential to develop further. As part of the federal government’s “Strategy for the Efficiency of Buildings”, further activities to support large solar thermal installations in district heating have been announced.

Solar thermal collectors were able to supply 29.5 PJ of primary energy consumption of renewables in 2017 (an increase of 4.9 percent since the previous year). However, solar heat still covers a relatively low amount of Germany’s heat demand.