Proposed changes/additions:
- Rename 0.14-style boilers to "heaters" - no change in behaviour
- Rename 0.14-style steam engines to "Stirling engines" - no change in behaviour, runs off any warmed fluid
- Add proper boilers (already planned for 0.15) - uses energy from fuel/heat pipes to convert water to steam
- Steam - 1 unit water yields some larger amount of steam, higher heat capacity and/or temperature range than water
- Add steam turbine (I believe also already planned) - more efficient than a Stirling engine, but only runs off steam, not hot water
- Start out the same as 0.14, with wood/coal/solid-fuel-fired heaters producing hot water for Stirling engines. So far, so vanilla.
- Research boiler technology, rebuild your power plant to take advantage of these. Boilers can produce steam from cold water, but perform much more efficiently when fed pre-heated water from heaters. Running this steam through your Stirling engines produces more power than hot water.
- Research steam turbines. Replace your old Stirling engines with turbines, increase power output further for the same fuel input.
- Optional step: research nuclear reactors. Heaters no longer required, boilers run off reactor heat pipes.