As a result of the nuclear power phase-out decision and because fossil fuels release too much CO2, the Federal Government's Energy Strategy 2050 aims to reduce energy consumption and to promote the expansion of renewable energies. The Swiss Federal Office of Energy has set targets both for the reduction of CO2 emissions and for the development of renewable energies. Both objectives are challenges for the electricity grid that call for a restructuring of the energy system. In this context, decentralised, multi-energy-hub systems (MES) may be an important asset, as they harness energy from various sources and distribute it locally. Each of these systems has several "energy hubs", allowing neighbourhoods and municipalities to cover at least part of their electricity needs on their own.
But what is required for reasonable planning of such multi-energy systems? How can the decentralisation of the energy supply structure be accomplished? Where is solar power better suited than hydropower? Which is the most cost-effective storage technology?
The joint project "Sustainable decentralised power supply" answers these questions. Kristina Orehounig and her colleagues at the ETH Zurich have prepared two case studies and developed a detailed method to adapt decentralised multi-energy systems to the respective local conditions and to optimise them. The Altstetten neighbourhood in Zurich and the rural village of Zernez in the canton of Graubünden were studied more closely.
To plan a multi-energy system, it is essential to know how much energy is required in the given area. The Orehounig team therefore determined the evolution of the energy demand in these two regions between now and 2050. To do so, they calculated the current energy requirements for electricity, heating and hot water. To forecast the future, they took into account the annual building renovation rate as well as the increase in temperature to be expected as a result of climate change. To implement a sustainable multi-energy system, one must also know how much energy the renewable sources in the area provide. In a second step, the researchers therefore calculated the potential increase in renewable energy production both in rural and urban areas. This would make it possible to decentralise energy production, and communities could cover at least part of their energy needs on their own, without resorting to fossil fuels. The potential of photovoltaic systems on roofs and ground source heat pumps on properties was investigated for both Altstetten and Zernez. Since the potential for large hydroelectric power plants in Switzerland has largely been exhausted, the researchers contemplated the use of a small hydroelectric power plant with a capacity of 2.3 megawatts in Zernez. Wind power was also considered. As the average wind speeds in both regions are low, a wind turbine for low wind speeds was simulated.