Is the engine Andrew Porter describes in his comments on thermodynamics (
Letters, 12 February) two-stage?
The efficiency of a single-stage thermodynamic engine cannot exceed the Carnot value, which is only a function of the temperature difference — at most 50 per cent for current technologies/materials.
Anyway, we should be seeking efficient engines to burn hydrogen or otherwise use it in a fuel cell, in anticipation of wider use of this energy source. We also need safe methods of storing and retrieving the gas.
J Gray, Warks
Water Sector Talent Exodus Could Cripple The Sector
Maybe if things are essential for the running of a country and we want to pay a fair price we should be running these utilities on a not for profit...