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greenhouse Greenhouse heating...I must be dreaming!

C

chilliover

I came across this brilliant idea to make a solar powered greenhouse heater but i really must be dreaming about it. I was thinking of connecting let's say a 14w solar panel to a battery with a transformer in between. Then the battery can be used to operate a small heater of some sort. I will also be attaching a thermostat to control the temp.

Ok so this sounds too easy to be true. I mean why haven't people done this already. My partner reckons this is not possible and i too am starting to believe this. I am not a techy person so have no designs.

But really can this be made?
 
14Watts is nothing...

you 100 W light bulb emits and draw 100 Watt... would you heat your greenhouse with 1/6 of a 100 watt bulb?


so surface wise, a solar panel is not efficient enough for a green house....
also your green house has the popose of gathering the heat of the sun in itself.

personnaly install a wood stove and heat it with wood. if you have acces to lots of wood and scrap to burn that should be much better than investing into solar panel...
 
My little space heater is 900/1300w. It is supposed to heat one room up to about 400 sq ft on high. So for you, you would need like 64 panels to run it on low....
 
i'm going to attempt to engineer a geothermal heating/cooling setup for the next greenhouse i erect. ground 6 feet under stays roughly 60 F degrees around here year round. theoretically we are going to lay a bunch of pipe down there and pump the contents thereof (alcohol/water mix possibly) through radiators in the greenhouse. also theoretically we may be able to power the pump with solar. my attraction to this rather than simply burning wood which i have tons of is the fact that it cools as well as heats. it is much more difficult to cool a greenhouse efficiently in this area than heat it.

if anyone has any first hand experience with such a system i'd love to hear it. i have a friend who heats his home with something similar and i'm just sort of intellectually bastardizing it.
 
The wattage of the solar panel is only important in how long it takes to charge your batteries...if you were running a standard smallish electric heater you would be using at least 900 watts. You would have to use an inverter to convert the battery's dc voltage to ac. The inverter is what would have to be able to handle the wattage of the heater. Then you would have to figure out how long your inverter could run the heater on battery power. You could add more batteries in parallel to increase the amount of time the inverter could power the heater...Then we're back to how long does the panel take to charge 2 batteries now...it can definitely be done...just need some know how with the electrical side. I would rig a backup heater to come on at a lower temp off wall power just in case your system fails or the charge runs out.

If your single panel does not charge the batteries fast enough...you would have to add another. There are calculators available online to figure out just how many panels/batteries are required for specific daily wattages. You can run your entire home off solar...so you could run your heater off of it. My guess though is that at best a 900 watt heater would drain a typical car battery in 15 to 30 minutes...a lager deep cycle type battery might last an hour. So to get you through the night you would need at least 10 batteries and enough panels to charge them all at your latitude and with your average cloud cover...These are guesses on my part, some research would be needed by you to get the actual #'s required.

Problem is that once you've designed and priced out all the req's you will figure out it will probably take 10 years to pay yourself back in electric bill savings.
 
I agree with stc3248.
I thought about a Greenhouse with solar panel and LED lighting to avoid the use of inverters, designing everythin in DC (clip fan, thermostat...).
But after some calculation I discovered that to provide enough light for a small Lightbox it would have required lot of batteries....and still nowadays, solar panel are too expensive!
 
You'll need to pay attention to the a.h. rating of the batteries also. So a deep cycle battery would be better suited towards using a specific amount of power for a set period of time. You'll need to make sure your solar panels you have can charge your battery bank quick enough as to not discharge the batteries during use. I say battery bank because constantly draining a single battery to a little charge overnight running a heater can't be good for it. So saying that, the more batteries you have the smaller amount of current draw you will have to each individual battery. You can use this calculator to figure out some a.h. stuff. 12v 220 a.h. battery could power a 900 watt heater for ~1.22 hours. Now I'm not sure if this calculator factors 900w/120vac=7.5a or not... http://www.alternate...alcbat06-2.html This battery puts out 11 amps an hour for 20 hours http://www.usbattery..._us185hcxc.html, its a.h. rating is 220 while its a 12v battery. Here is their complete list of batteries if you want a 6v battery more suited towards solar power http://www.usbattery...deep_cycly.html
First use this calculator http://www.usbattery...nergy_chart.htm
Then this calculator http://www.usbattery...%20%202V%29.htm with a built in calculator. The site just has a lot of good info on their batteries to give you an idea of stuff...
You'd probably need an inverter along the lines of this http://www.solarhome...nverter12v.aspx which will take your 12v dc in from the battery bank and put power out at 1000W at 115v ac.
now you just need to find a solar panel that can create enough power to charge your battery.
You would also probably benefit from a solar panel charge controller as to no over charge your batteries. That is, if you opt to have enough solar panels that this could be a possibility. I'm gonna guess that the total cost at the cheapest will be at least $1000.

Now I'm not super knowlegeable about all this so this was my best guess at what would be needed for this. I gathered all my info from lots of googling. I hope any information that i posted wasn't misleading...
 
With all that being said...there are some added benefits to using a solar system. It is a bit overwhelming but there are a ton of new incentives for going solar. They include things like tax breaks and even being able to sell power back to the grid in some places. (your excess power produced actually flows back onto the grid) There are also some cities that will offset some of the cost of putting up the system. My town doesn't buy back the power, but my buddies house is solar, and on sunny days his meter actually turns BACKWARDS! Pretty trippy, even in summer running AC at 68 degrees all day on 100+ degree days he gets $0 electric bills. His system has over 300 batteries and a whole hillside of panels...our grid is supposed to start paying for his excess within the next couple years.

All this is a far cry from the original post of maybe one small panel and 1 battery...but it is food for thought. The most effective way to make your greenhouse more efficient is through an efficient design. Recycling some of the heat you produce anyway...for example the dryer vent, geothermal heat, or banking the solar heat provided during the day by using heat syncs. Then obviously through proper insulation....

Sorry for writing a book...
Shane
 
Since we're speculating I say do a mulit prong approach. First put low power heat strips/pads next to the plants. Like the ones used for lizards. Wrap it around the plants. They don't give off much heat but they are right next to the plant. Next move all your compost and your neigbors' composting bins in the greenhouse. That will provide a little warmth. Next vent your laundry dryer into the green house also have the sewage (in a thin walled metal pipe) run through there too. Between hotshowers and the fact the water is above freezing that will help some. Next make sure that the green house walls are burried. Paint what you can black. Finally, use a recirculating solar water heater again with the pipes close to the plant. Any space that is not used should have bags of water for thermal mass.

The key to all this is making everything compact and insulating where you can.

Will it work? Probably not. But it will keep you off the streets which is good for you and society.
 
Best approch is WIND... create yourself a windmill coupled with a car alternator (or more alternator)or directly with a heat resistor and when it will have enough wing to make your alternator work regen the batt pack or the "heat" ele,ment will just heat the place...
but this is the basic aproch without too much control to provide heat when you want it...
but can be a great start
 
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