In terms of profiting from surplus electricity, Bitcoin (or cryptocurrency mining in general) is a great option as it's exceptionally simple to scale up and down in accordance with available cheap surplus. One major benefit that miners are taking advantage of is locating in close proximity to energy stations, reducing the inefficiency of transporting electrical energy over distance. This turns effectively "wasted" energy in to a solidly efficient energy store for infinite amount of time— for example: 1 BTC will always be equal to 1/21000000 of the total supply.