Eric Hanson wrote:Secondly, I have thought about a version of pumped hydro I call a mass battery. In the mass battery, excess energy would raise up a heavy mass, say a huge block of cement, using a worm drive to elevate along a shaft. After the mass is elevated, the worm drive would disengage would detach and a spur heat attached to a generator would generate electricity as the mass lowered back to ground. The mass battery is my own idea, would only apply to stationary applications, is completely hypothetical/untested, but would not spontaneously lose energy just by sitting.
S Bengi wrote:
Energy is gathered from wind, solar, or fossil generators on the grid as electrical energy and sent to Malta’s energy storage system.
The electricity drives a heat pump, which converts electrical energy into thermal energy by creating a temperature difference.
The heat is then stored in molten salt, while the cold is stored in a chilled liquid.
The temperature difference is converted back to electrical energy with a heat engine.
Electricity is sent back to the grid when it is needed.
Eric Hanson wrote:TJ,
I am afraid I misread your earlier post regarding using pumped hydro from waste energy from nuclear plants. This is another area I find fascinating for its complexity and diversity of often conflicting opinions.
Commercial nuclear power plants are basically designed to run at a specific power output level and while they can change their output, they often can’t respond to rapidly changing power needs. When they do change power, they do so slowly. Several tons of uranium still put out a lot of heat even if the reactor gets SCRAMed (Military nuclear plants are a different matter). Also, when the nuclear reactions are increased, they have to heat a LOT of water which soaks up that energy. It’s not that a nuke can’t change power settings, but they run best at a constant power output.
So how do they meet an increasingly erratic power demand? Some reactors run at a more or less constant power output and make up the difference with natural gas fueled gas turbines that adjust to load quickly. As you pointed out, others run slightly above average load and store the excess either in pumped hydro storage or compressed air in geological storage. Neither solution is perfect.
Strangely dovetailing with the OP’s comments about molten salts is the molten salt nuclear reactor that used molten salts as both coolant and fuel. These are experimental reactors that operated in the 50’s and 70’s with a movement to restart them today. Some hate the idea and some love it, but either way, an important factor in its safety system is that salts are used to capture and store the heat and have an enormous capacity to store that heat without creating associated pressure and the accompanying risk of a steam explosion like at Chernobyl (but not Fukushima—just to be clear, that explosion was NOT a nuclear explosion, it was a hydrogen gas explosion that would also be extremely unlikely as a molten salt reactor uses no cooling water that serves as a source of hydrogen).
Sorry if I rambled again, but I find energy in all its forms a fascinating concept. I am trying to be neither pro, nor opposed to any energy form in any of my commentary. I am just trying to describe the relationship we have with it. I can also barely resist the opportunity to discuss the qualities of molten salts.
Thanks for your patience,
Eric Hanson wrote:S Bengi,
For high temperature heat storage and heat transfer, molten salts are very hard to beat. I am curious about the overall efficiency of this system as each step in the process loses a portion of the overall energy so I am intellectually interested in how much energy the system delivers compared to how much it receives. Also, over time the hot side will cool over time and the cold side will warm. But over short time spans (such as overnight heat storage, maybe even a couple of days depending on power needs and circumstances) this setup could have real potential.
Extremely cool idea though. I did my masters research in the history of energy and I am starting to contemplate going for my PhD in the history of energy and by now I have an almost unhealthy fascination with all things energy. I now see energy everywhere. I see it in my coffee in the morning, sunshine streaming into my windows in the day, my Christmas tree—EVERYTHING! I especially like new forms, sources, methods of generating and storing energy.
If I don’t stop now, I will ramble on incessantly so I will conclude by saying again, very cool and you have piqued my interest.