But today grid operators increasingly value pumped hydro plants as workhorses able to mediate highly variable wind and solar assets. Pumped hydro plants could help to solve this problem but building them has often been expensive and difficult. Vast reservoirs and towering mountains, historically associated with pumped hydro projects, may no longer be essential. The IHA estimates that 600 GW of pumped hydro projects are in the global pipeline. One project that helped boost that total was the 3.6 GW pumped hydro plant in Fengning, China.