Feasibility study for 100 % renewable energy microgrids in Switzerland

Abstract. The growing worldwide level of renewable power generation requires innovative solutions to maintain grid reliability and stability, due to their variability and uncertainty. As well as stabilising the grid, renewable microgrids are also attractive solutions for regions wishing to produce green electricity independently from the grid, saving potentially high cable laying and grid connection costs. Switzerland does not yet have a large number of installed wind turbines, and despite the ambitious Energy Strategy 2050, not a single wind turbine was installed in 2018. This lack of progress is mainly due to large delays, costs and risks associated with the permitting procedure for wind turbines. The implementation of medium-sized wind turbines smaller than about 30 m may be a possible solution to this lack of progress, as they could experience an easier permitting procedure and higher acceptance among local residents. However, medium-sized wind turbines are less economically viable than larger wind turbines, and one method of making them more economically viable could be to combine them with photovoltaics (PV) and electricity storage into a renewable microgrid system. In this work, twelve sites in Switzerland are chosen for a 100 % renewable energy microgrid feasibility study. For all of these sites, a combination of wind and PV performs consistently better than wind only and PV only. This is due to the fact that wind speeds are often higher when the solar radiation is low, and vice versa. The combination of wind and PV ensures a more constant coverage of renewable energy production and therefore is more efficient. Five of the sites are found to be potentially economically viable, if investors would be prepared to make extra investments between 0.05 $/kWh and 0.2 $/kWh or between $5 million and $20 million upfront for green electricity independence. The Self-Sufficiency Ratio (SSR) is found to range between 1 and 2 for each site, reflecting the extra installed capacity required in order to fully cover every hour of demand in island operation. This could be decreased by connecting to the grid at times of low wind and solar resource and high demand. For the Wind and PV combination, halving battery capital costs reduces Costs of Electricity (COE) by 11 %, decreases the number of wind turbines by 1 % and reduces SSR by 1 %. Halving the wind turbine capital costs reduces COE by 30 %, increases the number of wind turbines by 16 % and increases the SSR by 16 %. Reducing the PV capital costs by 50 % reduces COE by 8 %, decreases the number of wind turbines by 39 % and decreases the SSR by 19 %. The actual implementation of 100 % renewable energy microgrids with medium-sized wind turbines is found to be strongly limited by the area required by the wind turbines as well as by the total number of wind turbines that can be realistically implemented. Additionally, a case study for an extension to a High Performance Computing centre in Canton Glarus shows that a feasible solution is available that meets the requirements. Specific projects are being further examined on a case-to-case basis.