Following the German government’s tightening of the country’s climate protection targets in June 2021, CO2 emissions are now to be reduced by 65 percent by 2030 in comparison to 1990. Previously, the goal was 55 percent. In building technology, the focus is on climate-friendly power generation and heating. With the Buildings Energy Act, which came into force last year, the government wants to promote energy-efficient construction and renovation in equal measure. This makes sense: from 1990 to 2020, greenhouse gas emissions from buildings fell by 43 percent to 120 megatons of CO2 equivalents. In order to achieve the targeted reduction of 65 percent by 2030, the German government’s plan for the building sector relies on an integrated approach consisting of consulting, CO2 pricing and tax incentives for energy-efficient renovations and climate-friendly new construction.
Thanks to subsidies of up to 50 percent through premiums and a repayment bonus, heat pumps for heating and hot water are a popular option in buildings. Heat pumps take advantage of the thermal energy stored in the environment, which is obtained from the soil, groundwater or ambient air. Geothermal and groundwater pumps are the more efficient options because ground temperatures remain stable throughout the year. State subsidies can offset the high acquisition costs involved. These pumps thus represent an attractive combination of climate neutrality, low heating costs and low-maintenance operation. Electric heat pumps are primarily installed in new buildings, but they are also an option when renovating old buildings.
Untapped potential remains in photovoltaic systems
Photovoltaic systems have been used in building services engineering for over 30 years now. After starting with Germany’s “1,000-roof program” in 1990, the number of systems installed on single-family homes and duplexes stood at 1.3 million at the end of 2020 according to the international market research and consulting firm EUPD Research. Despite this massive increase, there is still lots of room for improvement. Across Germany, some 11.7 million properties in this building class would support the use of solar modules, representing loads of untapped potential. The Buildings Energy Act addresses this by crediting 30 percent of the electricity generated by systems without power storage towards a building’s annual primary consumption. For systems that do store power, the figure is 45 percent.
For larger buildings such as hospitals, public pools or offices, cogeneration units are a suitable option. These systems use the heat produced in electricity generation to keep such facilities warm. While oil and gas are sometimes still used to power the generator, renewable fuels improve its climate footprint significantly.
Heating buildings with green hydrogen remains a vision – for now
Speaking of renewable fuels, green hydrogen may be a wildcard here. Produced through the electrolysis of water using only renewable energy sources, it would make it possible to operate heating systems without any emissions at all. For old buildings, there is the option of converting gas boilers. Due to the lower heating value per volume unit of hydrogen, however, this is far from a technical triviality. Fuel cells that can generate electricity and heat at the same time are a possible alternative, but the acquisition costs are high. According to a joint study by the Fraunhofer Institutes ISE and ISI, the quantities of green hydrogen available in Germany are still very modest; it would therefore need to be imported for the most part. To prevent this from thwarting the goal of reducing greenhouse gas emissions overall, we need “hydrogen (...) produced as regionally as possible, since long delivery routes can worsen the CO2 footprint,” points out Andrea Appel, project manager for hydrogen development at VDE.
The Smart Quarter Durlach project in Karlsruhe demonstrates how current technology can optimize CO2 emissions in existing buildings. The innovative concept has interconnected five buildings with a total of 175 apartments and equipped them all with heat pumps, photovoltaic systems and natural gas cogeneration units. The individual components are controlled by an intelligent energy management system, and error detection algorithms based on artificial intelligence ensure maximum efficiency. The results of related simulations have been remarkable: in addition to producing over 50 percent less CO2, the concept significantly reduces costs for the project’s operator.
Germany’s climate targets for the building sector are indeed ambitious. We will only meet these goals by developing even more efficient future-oriented innovations like these alongside the established technologies in this area – and quickly deploying them as soon as they are ready for industrial use.
is a freelance journalist in Friedrichsdorf (Hesse), Germany, who specializes in finance, green investments and science.