Urban energy system design from heat perspective
© Alain Herzog/EPFL
In his PhD thesis, Jakob Rager proposes a methodology to minimize the lifetime energy or overall systems costs while integrating renewable sources with thermal energy storage.
Increasing the share of renewable energy production in Switzerland is one of the major goals of the Swiss energy strategy for 2050. Because most renewable energy sources are intermittent, energy storages become an important part of the energy system.
In the build environment of Swiss cities, the heat demand represents the biggest share of the final energy use and the potential of solar energy use is largely unused. When using a solar thermal collector to produce heat, an overproduction in the summer is reached while the winter demand is not met. Shifting the overproduction to fall or winter months requires the installation of thermal energy storages.
In his PhD thesis, Jakob Rager under the supervision of Prof. François Maréchal (IPESE), therefore propose a methodology based on optimization techniques that minimizes the lifetime energy system costs while integrating renewable energy in the form of heat from solar thermal collectors with long and short term thermal energy storages. The example of a solar thermal collector and different thermal storages shows that using seasonal storages can be economical especially in combination with daily buffer storages. Those kind of systems can already be found today in Denmark.
The global sensitivity analysis of the results shows that uncertain operating costs due to non-renewable energy sources in the energy system such as the natural gas or oil price can lead to substantial higher overall costs. It is therefore interesting to hedge against the risk of higher operating costs over the lifetime of the energy system with higher investment costs into energy conversion technologies and storages. The investment can be justified through more efficient energy conversion systems or conversion systems that have almost no operating costs through the use of renewable energy such as solar thermal panels in combination with energy storage.
Urban Energy System Design from the Heat Perspective using mathematical Programming including thermal Storage, Jakob Rager, 2015