https://www.bbc.com/future/article/20220511-can-gravity-batteries-solve-our-energy-storage-problems"What goes up, must come down" – this is the immutable Newtonian logic underpinning gravity batteries. This new field of energy storage technology is remarkably simple in principle. When green energy is plentiful, use it to haul a colossal weight to a predetermined height. When renewables are limited, release the load, powering a generator with the downward gravitational pull.
A similar approach, "pumped hydro", accounts for more than 90% of the globe's current high capacity energy storage. Funnel water uphill using surplus power and then, when needed, channel it down through hydroelectric generators. It's a tried-and-tested system. But there are significant issues around scalability. Hydro projects are big and expensive with prohibitive capital costs, and they have exacting geographical requirements – vertiginous terrain and an abundance of water. If the world is to reach net-zero, it needs an energy storage system that can be situated almost anywhere, and at scale.1 HP = 746 Watts = 550 ftLb/sec ; 1 KW = 1000 Watts ; 1 MWHr = 1000 KW = 1,000,000 Watts for 1 hour.
550,000 pounds descending at 1 ft/sec for 3,600 feet = 1,000 HPHr = 746,000 Watt Hrs = 0.746 MWHr
1,100,000 pounds descending at 1 ft/sec for 3,600 feet = 2,000 HPHr = 1.49 MWHr
1,100,000 pounds descending at 0.5 ft/sec for 1,800 feet = 1,000 HPHr = 0.746 MWHr
In a valley in southern Switzerland, the striking steel and concrete prototype from Energy Vault, another leader in the gravity battery space, stands more than 20 stories tall. When green power supply exceeds demand, one of several AI-controlled cranes lifts a pair of 30-tonne blocks upwards. When demand outstrips supply, back down they go, generating enough energy for thousands of homes. Metric Tonne = 2,204 pounds; 10.83 ft/story
2,200 x 60 = 132,000 pounds ; 20 x 10.83 = 216.5 ft. ; 216/3600 = 0.06 ft/sec for 1 hour = 216'
132,000/550 = 240 HP per second
at 1 ft.sec. ; at 0.06 ft/sec = 14.4 HP = 10.742 KW = 0.01 MWHr
Well...maybe ONE large air conditioned American home in Phoenix in August...
The moral of the story is that it takes a lot of mechanical flailing around & wear to store energy with dry materials. Energy storage as chemical energy as a liquid fuel is compact & easy to deal with. Hydro works because water is heavy & easy to pump. H2 gas stored in existing "natural" structures such as salt domes or oil wells is useful for Utility power generation and the chemical industry. If a guy already had a 1,500 - 4,000 open shaft, maybe 30' in diameter near his house and money for all the superstructure, cables, generator hardware, rotating equipment necessary, you could certainly achieve gravity energy storage. The O&M cost of such a facility would be interesting to know.
The other moral is that science beyond the comprehension of the liberal arts major reporter/observer ungifted in the use of pencil, paper & practical maths is often perceived as magic..."generating enough energy for thousands of homes"...
Topic: Gravitricity! (Read 580 times)