Reply #17: The PV cells [View All]

that power my co-ops well take a big hit in output when clouds move overhead.
Normally,in clear sunlight,it produces power at around 35-38 volts.When clouds obscure the sunlight that number drops to around 10 volts.That is low enough to shut off the controllers for our system
Then again,these are ten year old cells.I have seen newer cells that do a lot better.I have seen a demo setup of the latest and greatest cells produce 30 volts and half an amp of power on a totally overcast day.
Proper testing and installation is crucial.A house I am working on was deemed unsuitable by a solar company after they did their sunlight survey due to to much shade from trees.The homeowner almost wasted tens of thousands of dollars until me and a roofer talked him into getting surveys done befor buying a system.