抽水蓄能这项源自19世纪末的技术，因风光等再生能源波动而再度受重视：可在数分钟内吸收或补足电力，降低弃电。英国今年因需求不足而关停风机，据报已浪费逾10亿英镑（约13.2亿美元）。

RheEnergise 在英国德文郡示范「高密度抽蓄」：以矿物粉末调配成密度达水的2.5倍且仍易流动的液体，让上、下槽仅需80公尺落差即可发电；若用水做同等500kW示范，液体体积需超过两倍且上池高度要到200公尺。传统抽蓄在英国可能仅20–25处可行，但其技术宣称可达6,500处；若测试持续成功，目标在2028年前推进10MW商业案。

全球面向扩张：国际水力协会估计抽蓄管线案约600GW，2024年新增装置8.4GW，其中中国丰宁3.6GW为最大。德国Goldisthal上池约1,200万立方公尺、下池近1,900万立方公尺，两条800公尺压力管，最大1.06GW，可连续8–9小时，90秒由停机到满载，单管流量约每秒100立方公尺。澳洲Snowy 2.0完工后可达350GWh，但27公里隧道工程延宕、超支：原估20亿澳元，可能升至150–180亿澳元，仍以150年寿命摊提。

Pumped hydro, first developed in the late 19th century, is being revalued as grids add variable wind and solar. It can ramp within minutes to absorb surplus power or cover shortfalls, reducing curtailment; the UK alone has reportedly wasted over £1 billion ($1.32 billion) this year by switching off wind turbines when demand was too low.

RheEnergise is demoing a high-density twist: a mineral-based fluid mixed over weeks to be about 2.5× denser than water yet still “runny.” In its 500 kW test at a clay mine near Plymouth, the fluid drops 80 meters to drive turbines, then is pumped back up. A water-based equivalent would need more than 2× the liquid volume and an upper reservoir around 200 meters high. The company cites ~20–25 viable UK sites for conventional pumped hydro versus ~6,500 for its approach, aiming for a 10 MW project by 2028 if tests hold.

Scale remains the headline. The International Hydropower Association estimates ~600 GW in the global pumped-hydro pipeline, with 8.4 GW installed in 2024, helped by China’s 3.6 GW Fengning plant. Germany’s Goldisthal links ~12 million m³ and ~19 million m³ reservoirs via two ~800 m penstocks for up to 1.06 GW, reaching full output in ~90 seconds and flowing ~100 m³/s, delivering 8–9 hours. Australia’s Snowy 2.0 targets 350 GWh but faces 27 km tunneling delays and costs rising from ~AUD$2 bn to ~AUD$15–18 bn, with a projected 150-year life.