beginner here, need help keeping my work trailer warm

kennedy759

I am currently installing a harbor freight 45w kit on my chicken coop to provide light and to power a 100w heated water dispenser(I have a 400w inverter). any way thats ok, but my main project is a way to heat my carpet cleaning trailer when temps are below 32 degrees as its full of pumps and hoses full of water. currently I use a 1500w space heater run from the grid. from my reading on this forum its hard to power resistant heat using a PV system, any ideas on how I can set this up. I know the space heater has to be sucking up a lot of power being run 12 to 24 hours a day. on the coldest days I would back it up with a second heater run from the grid

gww1

Re: beginner here, need help keeping my work trailer warm

The make or you could make solar hot air heater that would give you some help during days that the sun comes out, The simplest is like the guys who stack the soda cans in an insulated box and cover it with glass cold air goes in the bottom and hot air comes out the top some of the fancy ones have fans. Some are made with black metal with a gap covered in glass. Maby sI can't even reamember the name so you could do a search. It would probly give you the most heat for your buck.

http://www.builditsolar.com/Projects/SpaceHeating/ShopThermosyphon/ShopThermosyphon.htmMaby something like this

Good luck
gww

PS I got chickens too.

mike95490

Re: beginner here, need help keeping my work trailer warm

Sadly, the cardboard box the panels came in, will burn longer and produce more heat, the the normal HF 45w kits will.

If the panels did produce 45 watts, in a 3 hour winter day, you could harvest enough power (135 watts) to power a 100w bulb, for 1 hour. (actually somewhat less because of system losses)

For heating - forget solar electric. Try a Mr Buddy propane heater on lowest setting.

BB.

Re: beginner here, need help keeping my work trailer warm

I would highly suggest you get a Kill-a-Watt type meter and start measuring your loads.

For example, your 45 watt solar panel with ~3 hours of sun in the winter:

45 watts * 0.52 system eff * 3 hours per day = 70.2 Watt*Hours per sunny winter day
70.2 Watt*Hour of stored energy / 100 watt heater = 0.7 hours = 42 minutes per day run time

Insulation, design to prevent icing (bring up heat from earth, possibly a window to allow sun to defrost the inside, insulate everywhere you can) will be a big help.

In general, solar electric is very poor choice for defrosting power... It can be done, but you really need to insulate and understand your power needs (Kill-a-Watt meter or similar).

-Bill

waynefromnscanada

Re: beginner here, need help keeping my work trailer warm

It can be done, but I'd highly recommend you win the lottery first, or you may still be owing on the bill while on your way to your final resting place.
That's not a joke and not intended to be sarcastic, unfortunately it's reality.
As suggested by others, solar off grid electric is a very poor match for electric space heating. When all things are known, you'll very likely come to realize that grid power for electric heat is far cheaper and far more reliable than solar electric.
You have pumps etc that cannot stand being frozen, Early Winter especially, brings short dark and stormy days with often very little and sometimes no solar electric power available for many days. Run your batteries dead a couple of times and they're toast. Cold toast. Not to mention your frozen pumps.

gww1

Re: beginner here, need help keeping my work trailer warm

I still say that you mention you are going to use a backup 1500 watt heater using grid to heat the shed then the solar thermal siphon like in the link I provide may save some of the time the 1500watt space heater runs.
gww

kennedy759

Re: beginner here, need help keeping my work trailer warm

Thanks this feedback has been very helpful for a beginner. So see if this calculation is correct. Lets say I want to run the 100w chicken water heater 4 hrs per night. So if I have

255w solar panel*.52 eff*3 hrs of sun=398 Watt*Hours of storage.

398 Watt*Hours/100 Watt heater=3.98 hrs of run time. Also where does the .52 eff number come from? Also if I add two 100w panels can I use the same charger controller, or do I need one that can handle the higher watts?

(clarify units. -BB)

BB.

Re: beginner here, need help keeping my work trailer warm

I fixed your units a bit (Watt is a rate, like miles per hour; Watt*Hour is an amount, like miles driven).

Watts is how fast you are using energy.

Watt*Hours is how much total energy you have used over time.

The 0.52 derating for off grid power system--Very quickly:

0.81 solar panel derating from marketing Wattage rating
0.95 solar charge controller efficiency
0.80 flooded cell storage battery energy efficiency (typical worst case)
0.85 AC inverter efficiency (typical)

0.81 * 0.95 * 0.80 * 0.85 = 0.52 = 52% end to end system efficiency

And, you cannot really use 100% of the solar power every day--You should plan on only using ~66% to 75% of your base/required loads of the forecasted output of your solar power system (you may do better, you do worse). To use more energy, people use will power their "optional loads" on clear sunny days, and on poor sun days, they cut their loads are crank up the genset.

-Bill

kennedy759

Re: beginner here, need help keeping my work trailer warm

found an aquarium heater that uses 7.5 watts, should be able to run it about 9 hours. another lesson learned-use low energy sucking devices!

inetdog

Re: beginner here, need help keeping my work trailer warm

kennedy759 wrote: »

found an aquarium heater that uses 7.5 watts, should be able to run it about 9 hours. another lesson learned-use low energy sucking devices!

The true secret is to find a way to only heat the things you need to protect from freezing.
Heating the whole carpet trailer was clearly the wrong way to go about that.