heat pump for cooling condenser and boiling mash

[hefezelle]

Short version:
Has anyone used a single heat pump to both cool the condenser and boil the mash? It seems this should be vastly more energy efficient, and decrease cooling water consumption as well as electricity/gas/wood consumption.

To elaborate:
For both ethanol and water it takes about five times as much energy to vaporize (assuming the liquid is already at boiling temperature) as it takes to warm the liquid up from 0°C (32°F) to said boiling point. That means when running a still the biggest chunk of energy isn't used for warming up the load, but for introducing a phase change from liquid to gas in the boiler. This evaporation happens at a fairly constant temperature range (some degrees blow boiling point of water for a mash, or some degrees above the boiling point of ethanol for low wines).

The same amount of energy used for evaporation is given off by the steam as it condenses into a liquid, which again happens at a narrow range of temperatures, but at a somewhat higher temperture than in the boiler. Now, instead of discarding the heat given off at the condenser and introducing new energy to the system in the boiler, how about using a heat pump to transfer the heat from the condenser down into the boiler, "reusing" it so-to-speak?

One would need a heat pump designed to operate at that temerature range (ca 70°C/160°F on the "evaporator" side and ca 110°C/230°F on the "codenser" side of the heat pump cycle), which sadly implies you can't just use a fridge cooling cycle. I guess you would still need some additional heating of the boiler, even if the mash were already close to boiling point at the beginning of running the still - but in theory it should be significantly less than in a conventional setup.

It seems that other people have had the same idea, or at least a similar one before, but since the configuration mentioned in that thread is somewhat different than what i was thinking of (i guess, not entirely sure there), i decided to put this into a separate place. Also, there was never any conclusive answer in that old thread.

Please chime in if you spot something i haven't thought of, and tell about it if you have first hand experience!