It sounds like this article is suggesting new technologies for the batteries. Atlhough I may have missed it here, a few months ago I thought there was a rather large development being planned to use old batteries for these types of applications - specifically, those that still have life but could no longer be used in hybrids.
I'am pleased that I've pointed you to a new aspect of pumped hydro. There is a really good presentation of the Gravity Power concept on YouTube. If you want to learn more about this concept than you should give it a try. Takes 51 minutes and has some Q&A at the end.
Tom Mason, the CEO of Gravity Power has long experience in the energy sector and I've the feeling that he knows what he is talking about. Will be interesting what they learn from the planned small size pilot project.
Thanks for the links, DaveWR. That illuminates the challenges behind pumped hydro. It sill seems to have some virtues, in that rain can offset some of the evaporation, and there is value in recreational use.
DanielJoseph, your comment is very well said. A well designed small home power source should replace the water heater, providing heat, and hot/purified water as well. A lot of energy in the form of heat goes up the chimney from my gas water heater.
Is anyone working on using wind and solar to lift iron up a rachet belt to a tower. Hold it there as potential energy. Letting it compress air or liquid provides potential energy that can be converted to electrical energy as it's allowed to descend. Hmm, is any of the energy of a lowering elevator car saved for use in raising the car? Some hybrid automobiles save some of the braking energy in batteries.
I think that current battery grid storage solutions are very good to provide fast response to short term changes in load or demand and help to stabilize the grid in areas which are not very well connectet. But the batteries are still to expensive to provide hughe storage capacities needed for long term (days) storage.
I would like to point all hydro storage fans to the concept of pumped hydro without a lake. The company Gravity Power (http://www.gravitypower.net/index.aspx) has developed an underground storage with pumped hydro in a closed system which is modular and scales up to 600 MWh with 2400 MW peak power. Round trip efficiency is around 80%.
Second concept is developed in Germany by Eduard Heindl who proposed a pumped hydro storage which lift a huge rock mass with hydraulic pressure (200 bar) and potentially scales to 1 TWh capacity (http://lageenergiespeicher.de/en/hhs-storage.html)
Both concepts use existing pumped hydro technology and can be sited more easily than conventional hydro storage sites. Especially in Germany where some times more than 30% of electric energy is produced by PV and wind turbines, large scale storage will be required to keep the grid stable.
Yes, you can electrolyze water and then burn the hydrogen in an engine, but consider the round-trip efficiency. Electrolysis is only about 70% efficient, and the best binary cycle engines are close to 60% efficient. Multiplying these together gives you 42%. This doesn't include additional losses associated with compressing the hydrogen for storage. Thus for every 100 kWh of electricity you put in, you get back less than 42. Batteries and pumped storage, by comparison, have round-trip efficiencies of at least 80%.
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