- May 26, 2009
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I have played with solar a fair bit and am building a solar arrangement for my coop. I am not even thinking of attempting to use it to heat my water as heat generated by electricity takes a LOT of power. I am building mine more for lighting and to run some muffin fans for ventilation in the summer time as well as opening and closing my coop door controlled by a photocell.
If you do try heating your water with that 7 watt tank heater, I would recommend building a thermostat of some sort that will only cause the heater to come on when the temp drops below 40ish. I would also think about finding a 12v heat source. Power inverters are VERY lossy devices and cost you a lot of power to even be turned on (7 watts out costs a lot more than just 7 watts in, it takes power to form that AC wave), so your inverter may draw as much or more than your load in this case just by being turned on. If you let it run 24/7 at 14ish watts you will need a pretty high amp hour battery to have the capacity to carry you through the night and through overcast days, and I would recommend a MUCH larger panel. Keep in mind that even deep cycle batteries should never be drawn down to less than 70% if you want any kind of life out of them.
Solar power is expensive, anyone that lives off grid will tell you that they do not use alternative power methods because they want to save money. They do it because it is their only option or they are doing it for the environment (at the cost of extra $ to themselves).
Another thing to keep in mind is that you are talking about 7 watts out of your inverter at 110v. The way electric power (watts) is calculated is by voltage times current (in AC current it is even a little more complicated as you have to start talking RMS voltage vs peak, blah, blah, blah) so theoretically speaking if you are using 7 watts out of your inverter at 110v your inverter will be drawing somewhere in the ballpark of .7 amps continuously from your battery.
This may explain it better than I can
http://www.donrowe.com/inverters/inverter_faq.html#size
The best resource in the world for talking solar power, wind power, or hydro is here
www.otherpower.com
If you do try heating your water with that 7 watt tank heater, I would recommend building a thermostat of some sort that will only cause the heater to come on when the temp drops below 40ish. I would also think about finding a 12v heat source. Power inverters are VERY lossy devices and cost you a lot of power to even be turned on (7 watts out costs a lot more than just 7 watts in, it takes power to form that AC wave), so your inverter may draw as much or more than your load in this case just by being turned on. If you let it run 24/7 at 14ish watts you will need a pretty high amp hour battery to have the capacity to carry you through the night and through overcast days, and I would recommend a MUCH larger panel. Keep in mind that even deep cycle batteries should never be drawn down to less than 70% if you want any kind of life out of them.
Solar power is expensive, anyone that lives off grid will tell you that they do not use alternative power methods because they want to save money. They do it because it is their only option or they are doing it for the environment (at the cost of extra $ to themselves).
Another thing to keep in mind is that you are talking about 7 watts out of your inverter at 110v. The way electric power (watts) is calculated is by voltage times current (in AC current it is even a little more complicated as you have to start talking RMS voltage vs peak, blah, blah, blah) so theoretically speaking if you are using 7 watts out of your inverter at 110v your inverter will be drawing somewhere in the ballpark of .7 amps continuously from your battery.
This may explain it better than I can
http://www.donrowe.com/inverters/inverter_faq.html#size
The best resource in the world for talking solar power, wind power, or hydro is here
www.otherpower.com
