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philb 09-02-12 08:34 PM


Originally Posted by Acuario (Post 22420)
I have been given an evacuated tube solar water heating system and am thinking of how to incorporate it into a climitized greenhouse system.

My idea is to use the solar water heater to collect heat during the day and to have it connected to an underfloor heaing system in the greenhouse to maintain the soil temperature overnight and during the morning. The heating panels would be covered with soil in raised beds.

I'm also thinking of using a temperature/humidity sensor coupled to a processor based control system and (if I can work out how to construct them) motorised roof windows. The controller will control the heating/watering/windows to maintain an optimum growing condition.


I don't see why your ideas would not work. It will take some experimenting to get it right.
I think 1/2" PEX may fit the bill if you bury it in raised beds as long as you are out of the root and tool zones. There are plenty of hydronic valves and thermostats on the market.

You would have a large mass to heat, so I would think you need to start heating early. Also you'd need to store heated water for the days with no sun or make provisions for alternative heat sources. Lots of variables. Check Gary's site out for the tools and more ideas. BuildItSolar: Solar energy projects for Do It Yourselfers to save money and reduce pollution

I know of a few greenhouses in Kansas that have a one foot wide trench in the center of their greenhouses. I've been told they are 10 to 12 feet deep. They are concrete lined and water filled. That provides a tempering effect year round but limit growing in the winter.

Indyplumber 09-02-12 09:34 PM

Saw an article in Mother Earth News (i think) where someone made a greenhouse out of hog panels...very strong and able to withstand snow build-up. I have an old 75 gallon gas water heater and was thinking of DIY on the panel with PEX for the heat exchanger. It would be a drainback system. I also have some small circulator pumps, one for the panel (minimal head pressure) and one for the loop. I suppose I could run just one for the whole thing-though the loop then the panel-but I'm not sure the pumps I have could handle the friction though the loop then the panel w/o burning up.

If I REALLY wanted to do it right, I would also have a PV panel with a small wind turbine backup to power a bank of batteries, which would in turn power some grow lights set up with a photocell and a timer. The timer to turn on the lights at 6AM and off at 8PM and a photocell to turn them off when its daylight enough. (hmmm maybe even enough power to run some 12v pumps).

I'm not sure what temp the ground needs to be to encourage growth though...gotta look into that.

amber12 09-11-12 05:36 PM

Excellent idea of using solar water heater. I really want to have a greenhouse someday too and I will since I love gardening. My only suggestion is to make sure you study and have knowledge of the temperature you need to maintain in order to grow different veggies.. good luck :)

Acuario 09-29-12 06:20 AM

The greenhouse is almost finished
10 Attachment(s)
I have now almost finished my all year greenhouse. The greenhouse is 13 square metres in size and (as we suffer from very strong winds where I live) it is fixed to a shed I had built. The shed also houses all the control system for the greenhouse.

I built a control system using a PIC16F877A development board I bought on ebay, along with a few extra bits - display, keyboard etc. and I'm using DS18B20 1-wire temperature sensors for both the greenhouse and solar hot water control system.

The controller has settings for lighting (to control growth lights) these have settings for morning and evening times and a photo resistor to detect the light level and so turn on/off the lights as necessary.

There are 2 watering programmes that turn on an electronic valve for watering - there are 8 watering nozzels (4 each side).

There is a day time and night time heating program, the heating controls the underfloor circulating pump. There is also the ability to cool (not yet implemented though).

There is a control program for the solar heating that circulates water through the water panel and storage tank. Temperatures of both are monitored by 1-wire thermometers.

In the attached photos you can see the inside with the growing lights and watering nozzels, the control system and the individual programs and the whole control system. Also there are photos of the underfloor heating.

I have a few things growing in there now as you can see. I had a slight accident with over-temperature which is why the tips of the leaves of the lettuices are a bit brown.


Daox 10-03-12 09:41 AM

Wow, that is quite the setup! I'd love to hear more about how you went about making/insulating and designing the system.

Geo NR Gee 10-03-12 11:16 AM

Very nice setup. How are you cooling down the greenhouse? Are you using the roof vents, or are you going to install a fan? Are you going to keep track of how much this costs to operate?

Again, great job! Thanks for the inspiration.


Acuario 10-05-12 02:58 PM

Cooling has still to be solved. I have the control circuit pretty much built and the controller can activate the necessary relay. I'm pretty sure I'm going to use 12V computer fans - I have a box of them I bought years ago. The problem I have with using the windows is the wind we have where I live. Should it suddenly get windy it would rip the windows off, this is why it's built behind a shed; the shed is in the path of the prevailing winds.

The cost to operate is zero :-). You can't see them in the photos but there are solar panels on the roof that are connected to the batteries. These supply enough power to run everything. They were salvaged from a house I was working on when the owners had a grid supply connected.


Daox 10-05-12 06:16 PM

Can you tell us a bit more about the constructino of the green house? It looks like you used aluminum structural members and I'm guessing twin wall polycarbonate sheeting for some insulation value. Is the ground insulated at all? How is the tubing run in the floor? Do you have any pictures of the progress of the construction?

ecomodded 10-05-12 07:08 PM

I noticed the LED panels you have in the greenhouse, are they 200 watt panels ? have you grown with them before , i assume they will be lowered over the plants or are they strictly supplemental.

Acuario 10-09-12 01:40 PM

The greenhouse itself was bought as a kit (1000+ pieces, like a giant Meccano set!) so I can't claim any fame for that. It is an aluminium frame with 4mm polycarbonate windows so there is some insulation.

The base is only really insulated in a few spots as a result of the polystyrene mounting panels for the underfloor heating (the black panels in the photo). Apart from this there is no additional insulation. As the temperature here rarely drops to freezing it shouldn't need too much insulation as the sand and gravel floor shoud store some heat and the heated floor should (hopefully) do the rest.

The construction itself took about a day and a half. The instructions were in picture form with writing in German so a bit of guess work a couple of times!

The shed itself is concrete block - as I'm not a builder I employed someone to build it for me so it would have straight walls and not be dangerous....

The lamps are LED and are 15W each panel, total 60W. With the small solar system I have there isn't capacity for much more. They are fixed to the roof so we'll see... We are now harvesting food from there and have more vegetables on the way.


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