Integrated operation of renewable energy sources and water resources

To respond to the global climate change, Taiwan has announced an ambitious target for the development of renewable energy, which is characterized by solar power 20 GW and wind power 4.2 GW by 2025, but the intermittency of renewable energy sources might have serious impacts on the existing power grid. Not only the energy system but also water resources will be impacted by the global climate change. In Taiwan, the strength of rainfall increases but the frequency of rain decreases; this factor combined with a disadvantageous topography to store rainfall worsens the water-shortage issues. As a solution of the aforementioned issues related to the renewable energy sources and water resources concurrently, an integrated system and its operating model for renewable energy sources and water resources are proposed according to which hydropower, pumped-storage hydropower, solar power, wind power, desalination plants and the conjunctive use of water between two reservoirs are considered. A mathematical model is established to describe how the system works under various input data. The results show that, with a retrofit of existing old units and the addition of 102-MW new units, the hydropower unit of the proposed system can eliminate a requirement of 853-MW gas-fired power plants during peak loading in the reference case; the cost, US$45 million per year, of power generation can be saved. With 1099-MW pumped-storage hydropower units added, the proposed system and its operating model further enhance the peak-loading support; relative to a battery-storage system in the reference case, the cost of energy storage can save US$166 million per year. As for the desalination plants in the proposed system, the cost of producing water still exceeds that of the planned reservoir in the reference case because of its greater cost of operation. On considering the total benefit from the water and energy sector, the extra expense, US$41 million per year, for desalination can, however, be readily compensated; the proposed system can save more, US$171 million per year, than the reference case.