Problem: Wind and solar energy sources simply can't produce power at all times. Energy storage is needed to store energy from the sun and wind when it's produced for use later. No economical, widespread energy storage method currently exists that would allow a substantial portion of the electrical grid's electricty to be supplied by these renewable sources.
Solution: An inexpensive, compressed air energy storage system with 60-70% efficiency could be widely scaled, hopefully enabling terawatts of grid energy storage in the next two decades.
Technology that might make it possible: Water is used to cool air temperature during compression and increase temperature during expansion, making the system more efficient.
This solution is well thought out and considers the response of the fossil fuel markets and companies. A large expansion of renewables will just cause fossil fuel prices to go down to the cost of extraction and processing. Reducing emissions down to 20% of current levels is sustainable. Fossil fuels could only be used for high value purposes,
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