I thought it would be cool to have a Stirling Generator/Machine, that produces EU/kU and works by changing the temperature of Liquids/Fluids.
Basically how it would work:
The Stirling Machine has 4 internal/external tanks.
In tank 1, you put a warm/hot fluid.
In tank 2, you put a cold fluid.
The machine generates energy by taking warm fluid from tank 1 and putting the corresponding cold fluid into tank 3 and taking cold fluid from tank 2 and putting the corresponding warm fluid into tank 4.
Of course there have to be some restrictions, for example that the temperature of the (warm->)cold fluid you get can not be higher than the temperature of the (cold->)warm fluid.
So you could make energy from cooling down lava into phahoehoehoehoehoe lava and simultaneously heating up water to springwater.