How about this:
http://en.wikipedia.org/wiki/Gemasolar_Thermosolar_Plant- Thermosolar Plant: Water in a bucket heated in a furnace produces salt (only way to do so, unless "salt ore" is to be introduced). 4 salt buckets produces a salt block (how to keep buckets? Maybe like mushroom soup bowls.). Salt blocks are heated, when within range of lit Solar Mirrors (lit Solar Mirrors must be detected 25 blocks below the salt on a flat plane, in a 25 block radius). I'm thinking the salt blocks become "molten salt blocks" when the right conditions are met. The Solar Mirrors would just be some metallic structures on the ground, and must have a certain amount of light level to become "lit Solar Mirrors".
- Turbines: Turbines must have water directly under it, and a heat source 3 blocks below it (no other way), or just water above it for a dam. Water beneath the turbine is used up and disappears every so often, so a constant water supply is needed. Heat sources are lava, molten salt, working furnaces, anything burning (fire itself at that position), radioactive sources, etc.
*Further ideas
-Power cell: Essentially a portable battery. Power cell goes in a power cell charger (much like a furnace, but powered by wire), producing a full power cell that can be used for many things, like jet packs, generators, etc.
-Generators: uses up power cells to power other things through wires, much like a turbine.
P.S. Essentially, this is extremely realistic. Maybe to have iron or other metal between the water and heating source as a conductor. There are few effective means of extracting energy from a heat source otherwise. Although, I don't see why it can't be futuristic.