Nowadays, the building sector is responsible for around 40% of the total energy consumption and 33 % of the CO2 emissions. However, we are aiming to being CO2-free in this sector by 2050, which means the heating demand has to be reduced by improving buildings, and the remaining heating and cooling demand has to be covered by renewable energy sources.
There are some technologies which can help us to deal with this challenge:
1. The use of solar energy including solar thermal energy and PV technology
2. Heat pump technology including air source heat pumps and geothermal heat pumps
3. Thermal Energy Storage, Heat Pumps, and Hybrid Renewable Energy Systems.
Solar heating systems are most commonly hybrid systems with a solar fraction of 25 %. The other system is either the conventional heating system or a heat pump. Large solar systems with large seasonal stores are becoming interesting for district heating networks; these systems are often combined with heat pumps to reduce the supply temperature to the solar collector and increase the solar fraction. Solar cooling is always carried out by a heat pump, which in the case of solar thermal is by an adsorption or absorption heat unit, in the case of PV by a compression unit. Presently, solar cooling is dominated by PV systems.
However, there are some other advantages of heat pumps: they can use electricity from intermittent sources like wind and PV, and, in combination with stores, they can contribute to smart grids. They will act as the main heat generation system for district heating and cooling systems, using natural sources as well as heat recovered from industry, and they will be the key technology for making the market for heating energy efficient and CO2-free.