The German government has set a target of generating 80 percent of the country’s electric power with renewable sources by 2050. However, renewable energy generation depends on natural sources and therefore it is difficult to control. Consequently, experts have been working for years on ways to store surplus power or adjust consumption to generation. Potential intelligent components in future energy systems could be buildings. This would also make a carbon-neutral building stock a more realistic possibility.
That is the conclusion reached by Thomas Auer, Professor for Building Technology and Climate Responsive Design at TUM’s Department of Architecture. He worked with Prof. Thomas Hamacher and Prof. Ulrich Wagner from the Department of Electrical and Computer Engineering to develop a simulation tool to link the electric power and building sectors.
“Everyone keeps looking for ways to save energy in new buildings. The talk is all about zero energy buildings – but new buildings are not our biggest problem,” says Prof. Auer. “The major part of our building stock dates back to the time before 1980 – in other words, it predates the German ordinance on thermal insulation. We can’t remedy the overall situation with a few new buildings here and there.” Auer shows how existing buildings can be used intelligently to help bring about the energy transformation. And he is not referring to energy retrofits, which are often difficult to implement.
Buildings as load management buffers
Auer proposes linking the operation of buildings more closely to the electric power network to balance out the fluctuating supply from renewable sources. In the winter there is more wind – and therefore more wind energy – than in the summer. This could be used to supply heat by means of heat pumps. At present, most heating in Germany depends on fossil fuels, specifically oil and gas.
The excess power generated by solar cells in the summer months could help to cool buildings – a function that will become more important through the effects of climate change, says Prof. Auer. “We need to adjust the setpoint temperature of rooms to the peak generation in the power network. That would turn the building stock into a sort of buffer for load management – in other words a means of managing power consumption.” This way, huge power loads could be shifted towards the building stock in a very short period of time.
In the simulation, the team of researchers linked a model of Germany’s overall energy supply system to a detailed model of the building stock. The energy supply model incorporates various development scenarios for renewable energy sources up to 2050. The building stock model is able to represent up to 75 percent of the current energy demand for heating in Germany and takes into account several building types and energy efficiency classes. For example, the energy consumption of an office building differs from that of a one-family home. In addition, this model permits the study of scenarios based on the different possible upgrade decisions and energy technologies used in buildings. Auer calculates the electric power consumed within one hour – known as the load profile.
The combined simulation shows that under this approach, a carbon-neutral building sector would be possible by 2050 – although the use of electricity to operate buildings could almost double peak power demand during a cold period with lack of wind and sun. This would require an upgrade of the power infrastructure.