Daniel, Thanks for the intel. According to the specs I read the SW 325 mono-thai's can't handle a lot of wind from the back of the module. I'd be installing them with a pretty steep angle to keep the snow off them most of the time so snow load not too worried about but wind may be an issue. I'd thought of the 3 rail mounting as well - that is a good idea. Also thought of putting a wind shield behind the array to lessen wind loads from the north.
Was going to use a 10 kW since our modules stay pretty cool in the spring and get good reflectance off the snow. It was like 200 bucks more for the 10 kW over the 7.6 kW so figured it was worth it. Not sure of the economics of the Powerstor battery up here. We just get one rate per kWh any time of the day. Biggest loads on the utility are when it's cold and dark. Most people just keep a Honda generator around for emergencies. Maybe run it once a year. Best, Greg Egan I can?t vouch specifically for the Thai modules, but we also like SW a lot. They used to have more flimsy frames (30mm only I think, which did not allow them to be used for some racking) The new line has thicker 33mm box frames that allow them to go most places, using most racking systems with our lower snow loads (relative to AK at least).
I?d say though, all things being equal, in Alaska I?d be reluctant to use a 72cell module due to the extreme snow loads, or if I did, I imagine I?d use a 3-rail mounting system. Usually the 72cell modules have a slightly lower load rating due to their larger size using the same frame thickness. Solarworld lists the allowable loads (-loads for wind, + loads for snow plus wind) using several different mounting arrangements, I?d at least check that out using your knowledge of local snow loads. There are stronger framed 72cell modules out there that?s for sure (Suniva, Trina, Canadian Solar, I?m sure there are more).
Just curious, 8kW of PV, and a 10kW inverter? Are you planning on future expansion? If not, we usually would use a SE7600US on that size and then the client has the option to add batteries in the future, as the SE7600 is the only inverter they currently plan to make compatible with the Tesla Power Wall, and other similar battery systems.
With Regards,
Daniel Young, NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90
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