Is powering a 1500 watt heater extreme for a DIY'er?

[John P.]

Hi Folks, and thanks for being here!

My wife has a greenhouse that's roughly 325 sq ft.

She wants to grow vegetables during the winter. We have AC power going into the greenhouse but want to alleviate the costs. She has two heaters that run at 1500 watts. The plan is to use one of these extra heaters on an off-grid solar panel (with inverter) to keep it at 60 degrees f. Once the battery level drops, a charge controller will kill the circuit. The other AC connected heater will then initiate when the temp. falls to 55 degrees.

If I purchase two marine deep-cycle batteries (12v 51 ah each), keep them inside the greenhouse (for some warmth) and charge them during the day, would they be sufficient to power 1500 watts?

Despite all preliminary calculations, I cannot comprehend the value of amp hour in terms of continous watt usage. Will the batteries drain after only five minutes of use?

btw- we live in central PA.

Thanks in advance for any help!

John

[Mike90250]

Forget it. Solar PV will come nowhere near what you need. What will help, is thermal mass storage. Get some water containers, black preferablly. You can get black 5 gallon plastic paint buckets. Put them in the greenhouse where they will get warmed by the sun, they will release heat all night long.
Park old batteries in the sun, the heat they soak up, will almost be more than they can
store electrically.
example, 100AH deep cycle battery. has 50AH useable power in it.
50AH x12V = 600Wh of heat. About 5-10 minutes of running the heater.
Solar heat is about 40% efficient, solar electric is about 14%. Black buckets of water, and if it's really cold, fill them with hot water from your gas fired water heater. Triple glaze the windows, cover with blankets at night.

[John P.]

Thank you Mike,

An innovative idea, without a doubt.

The Mrs. is putting a plan together to make this work. We'll experiment in a week or two to determine temperature variations at night with and without the buckets. Looking forward to the results!

And thank you for the amp-hour calculation. I have a better understanding for other (less demanding) projects.

Kindest regards,
John

[John P.]

Update

Taking the advice, I used three 5-gallon plastic buckets, painted them black (paint specifically for plastic) and filled them with water.

The buckets heat up well during the day. During the night, I was able to compare the greehouse's lowest temperature.

Without the buckets: 51 degrees fahrenheit in 45 degree night temp.
With the buckets: 59 degrees in same 45 degree outside temp.

The buckets alone helped. Now to work on the additional recommendations!

Thank you.

John

[Aussie Bob]

Wow, I didn't think just buckets would have such an impact on the temp there. That's a good heating solution that doesn't cost an arm and a leg.