Smart energy system design for large clean power schemes in urban areas

Urban areas play a key role in climate change mitigation. We investigate here energy systems design to increase the use of renewable electricity (RE) such as photovoltaics and wind power in cities. We analyzed the hourly temporal and spatiotemporal energy demand and supply patterns in Delhi, Shanghai and Helsinki to understand how energy systems respond to high RE shares, and to determine realizable levels of RE power. The results indicate that if limiting the RE output to the instantaneous power demand, a 20% yearly share of electricity could be reached. Increasing the RE beyond this limit without a smart design adds only limited benefit. Adding short-term electrical storage could increase the RE share of power in Shanghai to 50-70%, in Delhi to 40-60%, and in Helsinki to 25-35%. An electricity-to-thermal conversion strategy in which surplus RE power is utilized for heating, enables to increase the wind power use in Helsinki up to 64% of the yearly electricity demand, but in addition, to cover 30% of the yearly heat demand. Such a scheme would add ca 10% to the overall wind power investment. A high RE share affects the existing power mix and the plant capacity factors, which need to be re-optimized. In the above cases, RE replaces fossil fuel and coal power plants and therefore the CO2 emission reductions from smart design are proportional to the RE shares shown. Smart energy system design could help mainstreaming renewable electricity as part of the cities' carbon reduction strategies.