use of refridgeration of warm air to dry crops -

[madfarmer]

Hullo all

I am building an experimentle small scale dryer to dry grass and similar crops, with the intention of upscaling to a full scale dryer depending on the results, I am now researching if it will be worthwhile using heat recovery and or drying the incoming air. It would appear that heat pumps can work on a 3 to 1 ratio, say 15kw recovered heat would cost about 5kw electric input. Is this, although obviously a huge over simplification is it basically achievable? I estimate after the air is exhausted it will be 80 to 100% humidity, with a temp difference over ambient of only 5-10 deg C. some expected parameters ( if useful for background info ):

incoming air ambient say 18-28 deg C. humidity 60-70%
drying air requires 60+ deg C.
air flow probably somewhere around 40 m3 / minute

Any thoughts / advice will be gratefully received.


Thanks for all the advice and suggestions. I always intended to use electric heat elements as the main source, particularly on this prototype, it would appear to be sensible to use heat only at the first stage, as a proof of concept, financial considerations dictate the cheapest options to begin with ( am talking financial outlay to begin with with running costs a secondary consideration at this point) when/if I think this 1st stage looks promising then heat recovery etc. will follow. When I said that RH will increase I was referring to the the warm air passing through the wet crop, drawing moisture out of the crop and dropping in temperature.
Some interesting lines to follow up re Perrys and woodchip drying though, thanks again