New coalmine questioned and high-density hydro planned: 10 top stories of the week 12 Feb 2021 High-density pumped hydro could store energy in small hills Thousands of hillsides around the UK could host a new type of pumped-hydro energy storage system, its developers have claimed. Unlike conventional hydro power, the system from RheEnergise uses dense liquid instead of water. The fluid is two-and-a-half-times denser than water, and could therefore potentially provide two-and-a-half-times the power of equivalent conventional systems. Cumbria coalmine permission to be reconsidered Cumbria County Council is to reconsider planning permission for a controversial coalmine project, which would be the first such deep coalmine in the UK for three decades. The council will reconsider planning permission in light of new information about the government’s ‘carbon budgets’ and net-zero aims.