Utilization of water conserved by interprovincial renewable energy substitution for thermal power: Incremental benefits and advanced reservoir operation rules

Renewable energy has been rapidly developed and transmitted across provinces to accelerate carbon neutrality in China. Water has been saved in power-receiving regions due to interprovincial renewable energy substitution for water-intensive thermal power (RST). The re-utilization of the water saved by RST through various ways is an urgent issue to be addressed. To establish the correlation between the saved water and related source reservoir and further utilize the saved water to maximize its incremental benefits, a general model framework is proposed to quantify the saved water and reallocate it to cope with emergency events and promote hydropower-based reservoir operation. The model is applied to an energy-water system centered around Henan Province. The incremental benefits and optimal reallocation mode of the saved water have been revealed. The results indicate that RST produces an annual water savings of 175.160 million m(3) in Henan Province, which contributes to the increase in hydropower generation and emergency water supply ranging from 14.584 GWh to 32.267 GWh and 0 to 1.724 x 10(8) m(3), respectively, under different hydrological scenarios. To boost the incremental benefits of water reallocation under RST, the source reservoir should concentrate on the emergency water supply in dry years and enhance hydropower generation in wet years. Conserving the saved water for future use would produce additional 12.771 GWh to 22.324 GWh of hydropower generation in the following year. As RST capacity increases from 40 to 320 TWh, the marginal revenues of hydropower generation and emergency water supply decrease by 75.4% and 40.7%, respectively, in wet years. This indicates that water supply from different sources should be rearranged to maximize total benefits according to the volume of water saved by RST and the marginal revenue characteristics. The general framework can be extended to other energy-water systems to assess incremental benefits and propose adaptive reservoir operation rules, which provides new insights into water management from the perspective of renewable energy substitution.