Electric production

localyokel

Member
Arable Farmer
Does anyone have some figures of how much electricity a hectare of solar panels produce compared to a hectare of maize through an AD plants.
 

Exfarmer

Member
Location
Bury St Edmunds
It is normally reckoned to need 5 acres for 1 megawatt although today I suspect you could squeeze them in 3.5
But at 5 acres you are getting roughly 200,000 units production per acre
I will eave it to @sjt01 to answer production from maize through AD
 

sjt01

Member
Mixed Farmer
Location
North Norfolk
Maize silage might produce about 0.5MWh/tonne, depending on dry matter, ME and efficiency of digestion and generation. At an average yield of about 18 tonnes/acre inland, less here near the coast, that is 9 MWh/acre/year.

A generally taken yield for PV is 900 MWh/MW peak, so for 1 MW on 5 acres, 200 kW on 1 acre (@Exfarmer values) there would be 900x0.2 MWh per annum, or 180 MWh/acre/year.

So PV yield is 20 times AD from maize yield.

Caveats - PV is peaky output, AD can be level output. Efficient use of AD also utilises as much of the waste heat from generation as possible, we are able to utilise about 1.2 kWh of heat for every 1 kWh of electricity we generate. We are also utilising the lower quality silage at the top, sides and bottom of the clamp, leaving the best for the dairy herd.

If PV panels were the price they are today, 15 years ago, we would have had a digester for slurry only, just for heat production, supported by PV and battery.
 
Last edited:

Y Fan Wen

Member
Livestock Farmer
Location
N W Snowdonia
If PV panels were the price they are today, 15 years ago, we would have had a digester for slurry only, just for heat production, supported by PV and battery.
I've just noticed a reference in Wikipedia about Currys selling panels in 2006 for 1k each! Didn't go on long!
 

Exfarmer

Member
Location
Bury St Edmunds
Maize silage might produce about 0.5MWh/tonne, depending on dry matter, ME and efficiency of digestion and generation. At an average yield of about 18 tonnes/acre inland, less here near the coast, that is 9 MWh/acre/year.

A generally taken yield for PV is 900 MWh/MW peak, so for 1 MW on 5 acres, 200 kW on 1 acre (@Exfarmer values) there would be 900x0.2 MWh per annum, or 180 MWh/acre/year.

So PV yield is 20 times AD from maize yield.

Caveats - PV is peaky output, AD can be level output. Efficient use of AD also utilises as much of the waste heat from generation as possible, we are able to utilise about 1.2 kWh of heat for every 1 kW of electricity we generate. We are also utilising the lower quality silage at the top, sides and bottom of the clamp, leaving the best for the dairy herd.

If PV panels were the price they are today, 15 years ago, we would have had a digester for slurry only, just for heat production, supported by PV and battery.
my experience is much closer to 200MWh for 200Kw of installed panels but you are correct in the official figures .
of course as you say the output from AD is far more useful and can be stored easily to enhance production at the critical times in morning and evening
 

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