I have a US book dedicated to sustainability, It suggests 30-40 Deg.
My guess is that the PV surface needs to be as close as 90 Deg to the sun.
I considered the lower value for grain store but this compromises the height to eves. or makes the ridge outside allowable height.
My next idea was for a roof of a "Northern Lights" configuration.
I have yet to decide but it passes my mind that a steep pitch would be more acceptable if you have in mind the building could end up as a dwelling.
The world is changing quickly. I was told by someone who should know that UK plans to plant 35000 acres of trees a year. Biomass will get priority as it is the only way to produce jet fuel. The present plans run to 2050.
Optimum angle will depend on latitude of the site because you are looking for as close to a 90 degree angle of incidence from the sun rays to the surface of the panel. The angle also varies throughout the year & depending on what the power is used for, you may benefit from tailoring towards the winter optimum to get the maximum from the winter sun.
Maintaining grass quality during mid-season grazing is important. Farmers can maintain quality by entering ideal grazing covers of 1,300 – 1,500kg DM/ha, and grazing down to a residual of 4cm every rotation.
If you are now in a situation where cows are not cleaning out paddocks as well as they should be, leading to the development of steamy grass within the sward, here are some options.
Common options for rejuvenating swards include:
Take a silage cut, probably into bales, remove the material and start again with the aftermath...