BB73

Hi everybody,

I just wanted to let you know about my improvements done on my little shelter i put up on my balcony.



This pic shows how it was at the beginning. It turned out, that it could keep the temperature just about 2 ° C ( 4° F) above ambient temperature, so I started thinking of what to do.
First, I added a layer of bubble wrap which I attached to the inside, but this didn't help much to keep temps higher.

I read about simple solar heating of swimming pools and adapted that for my greenhouse. Water has a very good heat capacity. I bought a 200 liter (50 gallons) water tank, which will be connected to black irrigation waterpipes, which will serve as solar heat absorber. A small pump (used for garden fountains) will constantly pump the water from the tank through the pipes and back into the tank.
I'm going to install the pipes at the south facing side inside my greenhouse. Putting them inside makes me able to use the pipes as heat radiator during the night.
Untill now, I just got the tank set up, because I'm waiting for the pump to arrive next week.
Even now the 200 l of water heat up from 10 - 12 ° C in the morning to 20 - 21 ° C at sunset. That's a difference of about 10°C (or 18°F). This energy will be radiated back during the night, so I'm having around 5° C ( 8 - 9° F) above ambient temperature for the first 6 - 7 hours already.
I'm hoping to increase the water temperature to around 30° C (85 F) (at sunset) with the absorber installed.
Even on cloudy days there's still some soalr radiation which will heat up the water. I will keep a electric heating cable as a backup for extreme colds.
The cost for running that heating will be very cheap. Only the pump will use electric power, but consumes only 8 W per hour. Still the set up costs some, but little money, but this can be saved in electric bills. One, maximum two seasons should be enough for amortization - depending on your electric power rates.

Another benefit is, that the greenhouse is not heating up so quickly in full sunlight, because some heat energy goes into the water to be heated up.

I will post some pics after everything is set up and running (hopefully successful)!

rick2001

Great idea, please post pics of the work in progress 'cause I'm very interested in your project!!!!

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Jack Daw

I sure hope to read more about the design too.

Nice idea!

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Thnx to Marcel, Ante, Dr. Chiranjit Parmar and Francesco for the plants I've received.



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Dalmatiansoap

Im also using water heating capacity for some extra heat inside my "DIY" greenhouse. Noting so compicate but enough usefull.

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RobG7aChattTN

With my greenhouse I'm not sure the water tanks really do all that much. Maybe yours will do more since your greenhouse is smaller (so your system is larger in relation to your greenhouse). I can't help but wonder if that small pump might use almost as much electricity as a small ceramic heater. You probably will need to run the pump 24 hours a day and the heater might be able to run only at night and many of them have a built in thermostat.

BB73

My pump will consume only 192 W per day. The pump has the power to pump up to 600 l (150 gal) per hour. That's three times the volume of my tank.
A ceramic heater would consume the same power in less than 30 minutes if it's a small one.
I don't mind the money for electricity - I want to see if this can done myself.

BB73

My system is now running.
In total I have pipes with a length of 11 meters (36 ft), diameter 2.5 cm (1 inch) and with a surface of about 0.9 square meters (9.7 sq. feet) installed.
They're served with a pump with a maximum capacity of 600 l/h (160 gal./hour).

I can regulate the flow rate and I think I'll put it down to a minumum, because I read that's best for solar absorbers.
My tank has a capacity of 200 l (53 gal.).

On the pics you see all the pipes facing the south side of my greenhouse and the small pump (connected to the green pipes which serve as inflow and output pipes to/from the black absorber pipes).
I'll cover them with black insulating material from the back, so the sunlight will reflect and the additional heat can be absorbed by the pipes.
I'm planing to run the system (with an automatic time switch) only during daytime and heat up the water in the tank. The pump can handle up to 35° C (95 F) warm water, but I don't expect it to go that high.
I hope that the heat radiation of the tank's surface will be enough to get some extra warmth for my plants.
If it won't be enough I can install an extra heating circuit, with an seperate water pump to let the warm water flow through at night. I have a temperature controlled automatic switch, which I could use for the pump to start below a certain temperature and stop again if temperature is high enough. But that's still optional. I'll see how it works for now.
In the last days the water at the top of the big tank reached around 21° C (70 F) in the day, but the water at the bottom was cooler, because there was no circulation. Now there is, because the pump gets cool water from the bottom and the water gets back in the tank at the top.
From tomorrow on, I could post updates and let you know if it works and the water get's warmer. Today it was too late to see some effects.

RobG7aChattTN

You might want to run the pump all night as well to help to distribute the heat from the water to the air in the greenhouse. The beauty of the system is that it will reduce temperature during the day when most greenhouses get too hot and radiates that stored warmth at night. I tried large 500 gallon tanks of water that were white with no water flow. The water stayed cold and I feel it did little to radiate warmth at night. I'm thinking about painting them black and adding a solar pump to circulate water. Solar would only operate during the day, but my greenhouse is too far from my house to plug a pump in. During the day my greenhouse often gets far too hot and I wish I could capture some of that heat in water. They make some really nice, thin black plastic water tanks for just this purpose but they are very expensive. They don't use a pump, but cover a large area and are relatively thin so the water heats up and releases that heat fairly easily. Anyhow, good luck. It looks like a good system and I hope it works for you.

BB73

I thought about using the pump for distributing the heat at night, but then I read how solar collectors are usually built and I decided to put some black insulating foam mat from behind. This should increase the heat collected by the pipes during daytime.
And I don't want to remove the insulation every night, so the warm air can circulate throughout the greenhouse.

Generally water has the best heat capacity, so any "storing" of heat energy is done best with water. But as you experienced yourself, a larger water tank itself doesn't heat up that good.

The other system you're describing has a large surface which absorbs heat far better. And at night it radiates back. Here in Europe they're selling inexpensive flexible water pipes with a large diameter. Beckmann-KG - BETA-SOLAR Wärmespeicher Sorry website only in german, but the pics will make it clear.

I've seen a very interessting system for greenhouses which has extra absorber panels, perfectly exposed to the sun, a 3,000 liter tank and seperate heating ciruit which runs along the roots of the plants. Everything is temperature controlled, like a heating system for the house. http://www.mazdasolar.com/shop/syste...3Dposition1%26It's from a test system installed in Nicosia, Cyprus. The company unfourtunately has no English website, but there are serveral tools for online translation of websites. Google has one itself.