Solar 12 volt heater

[Steve S]

I'm looking to put together a 12 volt heater run by a solar panel that I can use in the trailer or use in the greenhouse during the winter or even in the shop to take the chill off.
Where do I start and what do I need?

[dcg9381]

Steve, energy in = energy out, best case. That is, the greenhouse is probably taking more radiant heating than you'd get if you connected a solar panel to a 12V heating element.

Look up electric heaters for the car that plug into a 12V 20A cigarette lighter. You'll find, best case, that they're probably about 200 watts and get pretty poor reviews for heating the cab of the car. Just to get that much power out of a single panel, about 200 watts, the panel costs start at over $200. Add a battery and a basic inverter and it starts to get expensive for a heater that can't heat the cab of a small car in winter.

What *might* work is storing the energy in a bank of batteries, but you'll need several. And again, they're expensive and need to be deep cycle. From these batteries you could run an electric heater for a very limited time, with time being limited by the output of your heater and number of batteries... But you'd need to control how much the batteries are allowed to discharge (sunlight isn't consistent) and run the heater for limited time. DIY, able to power a 200 watt heater for an 8 hours, you're probably talking well over $1k in panels, smart inverter, and batteries, assuming you've got very consistent sunlight.

Most homes in northern climates that need renewable heat sources use geothermal. The pump water into the ground until it's warmer than air, then circulate the water in the floor of the house. Solar could power the pump, but doesn't provide enough energy for the heat itself.

Solar is good for some limited heating situations - like solar hot water, but most of the time that water is sitting around and being heated very slowly. It's not a good solution for a situation that needs consistent heat energy...



PM me if you have more practical solar questions.

[Steve S]

K I was just in the shop and I have one of these, with 2 batteries would it run a heater overnight?
During the day the heats not a big thing but I built one of these and it throws off an amazing amount of heat!
So am I on track or should I just use an electric heat

[Steve S]

Anyone Or does anyone know of a good solar site

[Steve S]

Originally Posted by dcg9381

Steve, energy in = energy out, best case. That is, the greenhouse is probably taking more radiant heating than you'd get if you connected a solar panel to a 12V heating element.

Look up electric heaters for the car that plug into a 12V 20A cigarette lighter. You'll find, best case, that they're probably about 200 watts and get pretty poor reviews for heating the cab of the car. Just to get that much power out of a single panel, about 200 watts, the panel costs start at over $200. Add a battery and a basic inverter and it starts to get expensive for a heater that can't heat the cab of a small car in winter.

What *might* work is storing the energy in a bank of batteries, but you'll need several. And again, they're expensive and need to be deep cycle. From these batteries you could run an electric heater for a very limited time, with time being limited by the output of your heater and number of batteries... But you'd need to control how much the batteries are allowed to discharge (sunlight isn't consistent) and run the heater for limited time. DIY, able to power a 200 watt heater for an 8 hours, you're probably talking well over $1k in panels, smart inverter, and batteries, assuming you've got very consistent sunlight.

Most homes in northern climates that need renewable heat sources use geothermal. The pump water into the ground until it's warmer than air, then circulate the water in the floor of the house. Solar could power the pump, but doesn't provide enough energy for the heat itself.

Solar is good for some limited heating situations - like solar hot water, but most of the time that water is sitting around and being heated very slowly. It's not a good solution for a situation that needs consistent heat energy...



PM me if you have more practical solar questions.

Thanks, I'll pm you with a few questions

[dcg9381]

Originally Posted by Steve S

K I was just in the shop and I have one of these, with 2 batteries would it run a heater overnight?
During the day the heats not a big thing but I built one of these and it throws off an amazing amount of heat!
So am I on track or should I just use an electric heat

It's 40 watts. Assuming you could store 8 hours of electricity from it, you could power a 40 watt heater for about the same amount of time, best case.

A 40 watt heater puts off less heat than a reading lamp in your living room. It's not going to work.


The "other" solution I saw is likely some sort of water heater - looks like it stores heat (hot water) in those cans. That would likely work much better and be much more cost effective.

[Festus2]

Steve -
If you are looking for something to "take the chill off", it appears as though the most cost effective way to do that is to go out and buy an electric heater such as an oil-filled one that can be used more safely in an RV situation.

Living where you do, come Fall and winter, there isn't a lot of solar energy available. The skies are mostly overcast and you don't get a lot of clear, sunny days during these seasons. In addition, the initial cost of the panels, batteries, controllers, and whatever "heating" units you go with (tin cans, etc.), the cost just doesn't make a lot of sense.

I'd simply go with BC Hydro, use an electric heater and be done with it.

[Steve S]

Originally Posted by Festus2

Steve -
If you are looking for something to "take the chill off", it appears as though the most cost effective way to do that is to go out and buy an electric heater such as an oil-filled one that can be used more safely in an RV situation.

Living where you do, come Fall and winter, there isn't a lot of solar energy available. The skies are mostly overcast and you don't get a lot of clear, sunny days during these seasons. In addition, the initial cost of the panels, batteries, controllers, and whatever "heating" units you go with (tin cans, etc.), the cost just doesn't make a lot of sense.

I'd simply go with BC Hydro, use an electric heater and be done with it.

Nawww, going with hydro is called giving up and I'm not going to give up I have a heater in the trailer, I'm looking to go solar with the greenhouse and was just asking for advice.
The pop can solar heater works great and blows out at 75 with the sun out on cold days and that's pretty good
The winter days here have a lot of sunshine which creates power to harness that can be stored and that's where my focus is. As for the expense I can't really call anything an expense that'll pay for itself down the road
The goal is to be completely off grid as who want's to pay monthly bills?
There's always a better way to do things if you ask me. Like it seems that alot of people here have septic/toilet problems but I've never has a problem since the conversion

[dcg9381]

If money isn't a consideration, I can help you figure out what you need...
You'd need to tell me what kind of heater is adequate for keeping that greenhouse warm through the night. Based on that power draw, can calculate power needed. Likely you're going to need a bunch of batteries, pretty easy to get 3+ days that are cloudy...

Read: Expensive.

I'm all for off grid. In your case where you need electric heat, likely a propane based water heater or something similar is probably most cost effective. Solar usually pays back against the grid, but in this case, the lifetime of your batteries and the number of batteries necessary may mean that long term it costs more to collect and store the energy you need for this particular application...

[Steve S]

Originally Posted by dcg9381

If money isn't a consideration, I can help you figure out what you need...
You'd need to tell me what kind of heater is adequate for keeping that greenhouse warm through the night. Based on that power draw, can calculate power needed. Likely you're going to need a bunch of batteries, pretty easy to get 3+ days that are cloudy...

Read: Expensive.

I'm all for off grid. In your case where you need electric heat, likely a propane based water heater or something similar is probably most cost effective. Solar usually pays back against the grid, but in this case, the lifetime of your batteries and the number of batteries necessary may mean that long term it costs more to collect and store the energy you need for this particular application...

When I get home I'll get the specs off the heater, at this moment I already know that I'll need an extra panel and 6 volt batteries. It's going to take a lot of heat to heat a greenhouse as there's no insulation. Sourcing heat from the ground is starting to look good
Just for the recorded I'm just trying different options and trying to do things like building my own stuff. As for costs if I was to buy everything from the solar store I'm looking at around 4 grand and that's hard to justify for a small greenhouse, I'll post a few pics.
The biggest problem with everything is that I would need to store the heat and the energy as you say the sun doesn't shine everyday

[JRTJH]

We had a 6x8 greenhouse in Louisiana. It had an aluminum frame and the "panels" were made of clear plastic corrugated material. It was "somewhat insulated with air gaps formed by those panels. http://www.harborfreight.com/6-ft-x-...use-69714.html

Even in Louisiana, it was "costly" to try to keep it warm during the winter. Up here, our "greenhouse" is a seasonal item. We use it in the spring to "hasten the growing season" but when the frost starts in November, anything in the greenhouse either becomes "freezer fodder" or we have to bring it inside. I wouldn't attempt to heat a greenhouse in this "tundra" LOL

[Steve S]

Originally Posted by JRTJH

We had a 6x8 greenhouse in Louisiana. It had an aluminum frame and the "panels" were made of clear plastic corrugated material. It was "somewhat insulated with air gaps formed by those panels. http://www.harborfreight.com/6-ft-x-...use-69714.html

Even in Louisiana, it was "costly" to try to keep it warm during the winter. Up here, our "greenhouse" is a seasonal item. We use it in the spring to "hasten the growing season" but when the frost starts in November, anything in the greenhouse either becomes "freezer fodder" or we have to bring it inside. I wouldn't attempt to heat a greenhouse in this "tundra" LOL

Yeah John I'll be doing the learning curve this yr with the cold

[mikell]

Wood stove $1000
Semi load of logs $2500 good for 3 years
Spend the rest on a couple of panels batteries and some led's

[Steve S]

That's an expensive wood stove A pellet stove would be better as they're cheap and can be loaded for the night.
So far with two panels the heater runs fine during the night ( I check @ 2am ) and it's running fine.
It's amazing how much power can be stored even in this crap weather.