- Cement takes 5 MJ/kg - 
- A 200kW panel produces 4300 MJ per day. 
- (1 kHwr = 3.6 MJ)
- Solar array can produce 860 kG of cement per day. That is 43kg. 20 sacks of portland cement per day. That is $10 per bag - or $200/day
- The value of electricity only is $120 - so that is value added electricity right there.
- With 200kW at $100k installed - that is 500 days to payback time.
- Molecular weight of lime - CaCO3 - 40+12+48 = 100. MW of lime - CaO - is 56% of the original. So about half gone. 
- The open source microfactory with 200kW solar power yields about 20 sacks of cement per day starting from limestone. Cost of delivered gravel is $10/ton.
- Cost per day in lime - $20. 10% costs of materials.