Environmental efficiency evaluation in high solar wind penetration region with fractional optimization-based operational planning

The article develops and demonstrates the fractional optimization to evaluate the environmental efficiency of the regional-scale energy system with heat pumping and thermal storage. The fractional optimization gets converted into the equivalent quadratic one via the proposed iterative algorithm. The proposed method makes converting a fractional equation into a different one with an auxiliary variable, and it makes us free from heuristic parameter tuning that makes balancing the weight of objective coefficient when the objective function is composed of some terms. We consider the operational planning problem of the mixed energy grid, including electricity and heat. It manages power generations and a heat pump with thermal storage as an application. The numerical studies take into account the open data measured by the most western region of Japan, where the region gets applied the installation/connection of variable renewable energy sources of 25.7 GW at the moment even not every capacity starts operation. As a result, the CO₂conversion factor reaches 0.21 kg-CO₂/kWh in the best case. It is confirmed that a heat pump with thermal storage can absorb the electrical output from variable renewable energy sources up to 2.72 TWh/y.