yup I agree entirely to all points. I am sure there is a formula though to work it out under 'ideal conditions' (what ever that means!)I am not an expert, but I do not think there is a simple answer.
It is a matter of reducing the R/H of the incoming air.
The lower this is the quicker the grain moisture reduces.
Also you cannot the grain moisture below certain points if the R/H is too high.
So basically the more heat you put in the quicker the grain moisture will come down
Using today's prices, kero at 45p and wood chips at 110 per tonne makes biomass hard to justify.Does this help?
Balring Farm, Mintlaw (courtesy of Hamish Watson) Hamish grows 283ha (700ac) of combinable crops (2,100t) and installed a 100t tray drier with stirrers in 2007 (previously had 2 mobile driers). The tray drier was supplied from Clark & Sutherland and cost approx £60,000 which included the shed.
The tray drier used two burners fuelled by gas oil, normally operating at 55oC with an electric fan blowing the hot air through the grain. A full tray (100t wet grain) would take 12hrs of drying (20% mc grain dried to 14%mc) plus a further 3hrs of cooling. Depending on the grain’s moisture content it would normally take 1,000l of gas oil to dry 100t of grain (10,000kWh, 1L diesel = 10kWh). The annual cost to dry the combinable crops was £14,700 and rising annually.
The economics Previously to dry 100t of grain would take 1,000l gas oil @70p = £700 or £7/t Using biomass, 100t grain would require 2.5t wood @ £ 50 = £125 or £ 1.25/t A saving of £ 5.75/t or £ 12,075 per year for the farm (2,100t) If eligible for RHI, can earn £7,711 for drying the grain which is index linked for 20-years Effectively the crops are dried for free, plus £ 5,086 surplus.
Balring Farm, Mintlaw (cont) Assumptions:
• Dry 2,100t pa using the biomass burner.
• Throughput of the tray drier 100t in 18hrs = operating for 378hrs
• 378hrs @ 400kw = 151,200 kWh
• 151,200 kWh @ 5.1p (tier 1) = £7,711
Without RHI, pay-back of the £34,000 capital cost would be 3-years from the savings in fuel cost. With RHI, pay-back is less than 2-years plus crop drying in the future is free.