Need advice on a Solar powered Green house project.

Hello new to the Forum but i need some help. I know enough about electronics to rewire a tractor and do some small hobby projects but this one is a bit more complicated them i'm use to. I'm not even sure what i want to do is possible.

I'm building a greenhouse and I had an idea to make it a lot more useful to me. I've seen people do amazing things with solar power including a guy on YouTube make a solar power bulldozer. So i thought it might be possible to make a heated greenhouse. i only need to keep the temperature above 32 degrees in the winter and 50 degrees in the spring. This would be a huge advantage for my hobby farm. I live in northern Ohio AKA the land of ice and snow. If i could hook up a heater and thermostat to keep the temperature in a small 16'x8' greenhouse above freezing all year long i could start plants early and keep some year round.

I figure i will need an inverter, charge controller, 3-4 12vt car batteries, and two big solar panels maybe 275 wat. I'll point one east and one west at an angle so at least one will be getting sun all day so long as i knock the snow off of them.

So is this something that would even work? i know nothing about calculating power usage so I don't even know if a solar panel can put out enough power to keep a heater going. I'm willing to put $1400 down on this if I can get a heated green house but i don't even know if solar panels are capable of providing that kind of power.

Thanks.

It isn't impossible but it may be impractical.

The problem is heating is by far the greatest consumer of power and the time you need it most is when the least is available. Look at it this way, even for a small green house you probably need at least 1KW of heating (like a small portable domestic electric heater) and your panels in direct sunlight could produce 275W. That means if there were no other losses it would take about 4 hours of direct sunlight to allow 1 hour of heating. In practice, expect maybe 60% - 70% efficiency when you take into account the charger, battery losses and an inverter to step the battery voltage up again so lets say 5 hours of sunlight for 1 hour of heating.

Now you can see the dilemma, in mid winter the days are shortest and the sun is lowest in the sky but the heat demand is highest. To get full power from the PV the panel needs to be directly facing the Sun and at best with a fixed installation you can only achieve that twice a year, that's what some systems use steerable panels but don't go down that route unless you really want a challenge!

What might be more practical is to use PV power to extend the lighting period so your plants think the days are longer, that uses far less power. You would still need a more reliable heating source though.

Brian.
(10 degrees more north than you!)

Well I'm building the greenhouse this fall. I already have some of the stuff to get the solar idea going.

I figure I'll start out with adding lighting for extended hours. Then see about heating.

If I have to add a few solar panels every year that's fine. A heated greenhouse would be such a huge advantage to my farm that it's worth it.

I need at least 50 apple trees and 100 blueberry bushes next year. If I had that greenhouse I would have a much better survival rate when they come in.

I also want to get a automatic solar pump for my irrigation system but that seems like it would be pretty simple. Unless there is some issue I don't know about.

To heat houses, etc., it is common to let the sun shine on black-painted tanks which contain circulating fluid (water-based or refrigerant). Pump the heated liquid to a heat exchanger (or heat pump) inside your greenhouse. A return loop carries cooled liquid back to the black tanks.