Re: Solar office
As as been said quite often,,,do your math. Calculate your loads,,, using a kill-a-watt or some similar device. Then calculate your potential from any give set of PV hardware. A simple calculation is (not perfect,, but simple) take the name plate rating of a PV panel, multiply that by the number of hours of GOOD sun, (usually ~4 in most cases over the course of a year,, maybe as much as 6 if you are in a really good location) and divide that number by 2. This will give you the useable 120volt watt hours (wh) you can expect in an average day. The number two factors in all the system (in) efficiencies, panel, wiring charge controller, inverter losses etc.
For example,, your 45 watt panel, 45X4hours/2=90 watt hours,, enough to light 15 watt cfl for 5 hours.
Now a couple of other things to consider. Modified sine wave inverters CAN destroy some electronic devices right away. They can also burn out 120 vac motors quite quickly. Also most cheap MSW inverters have terrible efficiency curves,,,so the above example only gets worse.
If I could give two pieces of advice to newbies, the first would be avoid the "ready, fire , aim" syndrome by doing your math,, and doing your homework. The second would be buy from experienced, dedicated solar retailers rather than Harbor Freight, Northern Tool, or much of E-bay. There are good reasons that people like this site sponsor have good reps to go along with the products they sell. They have been tried and tested by some very smart people,,, such that newbies don't have to reinvent the wheel.
One other piece of advice I would give newbies is battery based solar is, on average, twice the price per watt hour as grid tie. If you are looking to do any solar to "save money" you are twice as far behind using a battery. Even grid tie is not going to save you money,,, unless you have done EVERTHING you can do to conserve,,, and then you have to build a real system,,,, and even then the payoff comes in multiple number of years,, at best.
Last edited by icarus; April 22nd, 2009 at 19:18 PDT.
Please note, being a moderator does not add any weight to my opinions 300 watts Siemens/BP panels,plus a Sun 90,, making ~400. ~30 amps into Rogue MPT-3024, 450 ah of Trojan T-105, Morningstar ts300 inverter, a Tri-Metric meter.a collection of antique generators, plus 2 Honda eu-1000i's (also a BS2512 IX controller) and assorted other stuff!