Help understanding solar

[Denim Deb]

I don't claim to really understand much about solar, or about electricity itself for that matter. And, I'll admit to being confused. I'll read stuff on it, and basically, it just confuses me more. The thing that's really got me wondering now is the post on the solar generator. For those that haven't seen that thread, it was a 1800 watt generator that was powered by a 90 watt panel. So, how does that work? I'm wanting to put solar panels on my tack shed. There's no way I can have main power to it, so if I want power, solar it is. I'd love to be able to run a mini fridge during the summer, as well as a small fan. Plus, I have a hot plate, single cup coffee maker and tea kettle I use occasionally. (Right now, I have an extension cord running into it, but use them rarely since I don't want to increase RU's electric bill.) During the winter, I'd like to have a space heater running in there. While I have one that's only 200 watts, I'd kinda like the one I saw in Wally World yesterday. It looks like a wood stove, and has 2 settings, 650 watts, or 1300. I'd probably just leave it on low since I have a small propane heater I use if it's too cold.

I already own an inverter, (I'm thinking 2000 watts), one set of 45 watt solar panels from Harbor Freight, and a deep cycle battery. If I were to get another set of panels, as well as another battery or 2, would this do it? Or is what I'm wanting to do either impossible or improbable or too expensive?

 

[Leta]

Well, making heat with electricity is EXTREMELY kilowatt intensive. Heat is the number one biggest electricity hog, followed by cooling. This is why when you hear about off grid electric applications for heating and cooling, what it actually is is a geothermal pump system. The solar/wind on-site generated electricity is not actually generating heat or cold, it is operation the pump and fans which are moving air from deep inside the earth up into the house. Especially electric heating elements have, in fact, gotten a lot more efficient in the past few years (the best example being on-demand water heaters), yet even with these improvements, heat is *still* the biggest hog.

This rambling preamble is getting at this: you are not going to be able to run an electric space heater off of solar panels. You would have to have a massive solar array and dozens of batteries. It would not even be close to cost effective, and you'd be able to run a space heater for maybe 30 minutes and then your batteries would be emptied. Stick with the propane heater. It is much more practical for an off grid application.

I know two households that are off the grid, both use composting toilets, both heat with wood, both have wood/solar heating systems for hot water, and they still both use propane for back up heat, non-wood cooking, back up hot water, and their clothes dryers. Gas is much, much better for these applications when you are generating your own electricity.

On the other hand, a small fridge is totally achievable, especially if you go with a chest fridge, which is ten times more efficient than an upright. To convert a chest freezer into a fridge, you need one of these. You could also get a small inverter that you plug the fridge into (rather than wiring the solar panels into a big inverter) and then you'd have DC fridge, which is inherently more efficient.

Lights and a fan shouldn't be a problem, either. DC fans and lighting are both easy to find, just look for stores that cater to RVs and truckers. Conventional small appliances like coffeemakers are really all over the place, wattage wise, so you'd probably be better off looking for DC versions of these when you look for the lighting and fans. They might be a little more up front, but there efficiency will mean they'll pay for themselves by negating the need for more solar panels.

Right now, you have a total of 90 watts in panels. If you get 4 hours of sun per day, that's 360 watts per day, or 10 kWh per month, an admittedly optimistic estimate. A chest fridge uses about 0.1 kWh per day, or 3 kWh per month, so that leaves you 7 for lights, fans, coffeemaker, etc. You may need to buy a couple more panels, depending on how often you use this stuff, but I think this is very doable.

 

[dragonlaurel]

Thanks for explaining this. Great info.

 

[xpc]

Leta pretty much nailed it, no electric space heater for you... try snow boots instead.

Propane is twice as cheap as electricity to heat with and grid electricity is 20 times cheaper then photocells. A 2000 watt Honda inverter type generator may be a better alternative in the short run.

Math:

The national average for electric is 10 cents per kilowatt, costing 15 cents an hour for a 1500 watt space heater - propane when bought in bulk is half the price of electric. 1500 watts in solar cells will cost about $3500 and will only produce whilst the sun is shining otherwise it will need batteries. In your instance it will need batteries regardless, and unless you have an expensive true sine wave inverter will lose 15% to the heavens as an additional tax.

A one hour battery bank will cost about $200, quadruple that for a good controller and equalizer charging machine, add in the very large copper cables and controls and you end up with about $5000 in bits and pieces which may only work for a day in cloudy weather.

ps. you can not use car batteries, but rather a more expensive deep cycle fork truck type that is designed for your special purpose. Add another $1000 for an afternoon of electric heat.

 

[sunsaver]

Solar has many practical uses, and over its 30 year life expectancy, it will surely pay for itself many times. But solar heating is different than solar electric. Solar electricity is too expensive for electric heating. There are many people out there who are working for the energy industry, and the oil and gas industry as well, whose sole mission in life is to discredit the effectiveness and deny the benefits of solar power. I have been living off-grid solar for two years now. I have missed out on several power outages. While my neighbors were walking around with candles, i was watching TV. It even works on cloudy days, contrary to the naysayers from the oil and gas industry. So please pm me with your solar questions, instead of throwing yourself to the wolves. Thanks! -your friend, Sunsaver.l

 

[animalfarm]

Solar has many practical uses, and over its 30 year life expectancy, it will surely pay for itself many times. But solar heating is different than solar electric. Solar electricity is too expensive for electric heating. There are many people out there who are working for the energy industry, and the oil and gas industry as well, whose sole mission in life is to discredit the effectiveness and deny the benefits of solar power. I have been living off-grid solar for two years now. I have missed out on several power outages. While my neighbors were walking around with candles, i was watching TV. It even works on cloudy days, contrary to the naysayers from the oil and gas industry. So please pm me with your solar questions, instead of throwing yourself to the wolves. Thanks! -your friend, Sunsaver.l

Agreed. You can run an amazing amount of stuff on solar if you plan it properly, and discipline yourself to not waste. Many fridges take a very small amount of electricity to run, and can run on a cloudy day if not overloading the sytem with useless stuff.

 

[Leta]

Oh, I forgot this:

there is a way to have solar space heating, it just is not electric. Go to YouTube, and search for "solar space heater". There are bajillion videos on how to build one. Basically, what you are doing is building a super insulated box that contains either aluminum tubes or an aluminum sheet with baffles, painted matte black and covered with Lexan. You put inlet and outgo ducts on the back with dryer ducts. You will need a small fan to keep the hot air moving. You have to keep the snow cleaned off of it so it can work. You place your solar space heating panel on the S, SE, or SW side of your building, and you have to drill holes in your wall to get the hot air and the cold air out. You can wire a thermometer and some other upgrades in, so the fan kicks on below a certain temp and kicks off above a certain temp.

CanSolair and SolarVenti are two companies that make these units, but building your own will save you some bucks.

 

[Kiasmama]

great information in this thread!

 

[Gypsi]

I use passive solar to heat my house on sunny winter days. Total equipment: Curtains - close them at night and run the wood stove, open them in the morning as soon as the temp between window and curtain is warmer than room temp. My house has large south facing windows, it was about 64 in the kitchen when I left today, 65 in the living room. I opened the small windows on the south side a couple of inches to air the place out too. It was 72 in here when I got home at 6. Outside temps today didn't reach 60 but it was sunny. And my wood stove needed ash removed, so I needed to let it cool down..

And for your hot plate - I paid $55 on Amazon for a Max Burton 6000 induction cooktop. Requires a 20 watt circuit, brings water to a boil MUCH faster than conventional electric stove. You will need iron or steel pans, it works magnetically somehow. Get a stainless steel percolator and you have coffee. Box says it needs a 20 amp circuit, it's done fine on my 15 amp, so with a couple of solar panels, I'll bet you could get something cooked.. I gave my electric range away a week after I got it. Plan on picking up a couple of more. Will fit in a drawer when not in use, if I'm cooking for a lot of family, I need more than one burner.

 

[Denim Deb]

Remember though, we're talking my tack shed-total size, 8 ft x 12 ft. The hot plate is a single burner one I got for $10. Basically, I use it to heat up lunch, or heat up water to wash my dishes. And when possible, I use a solar shower for heating up water.