Simple and cheap solar hot water idea

Daox · 09-19-08, 12:24 PM

IMO solar hot water should be used pretty much everywhere. This is a great place to start and doesn't have to be expensive. In fact, you don't even really need to go with solar commercial products. Here is a rough idea I have.

If you live in a warm climate it could be as simple as running a cold water line to a black painted tank in your yard or on the roof. You then run an outlet line from that tank to the water heater. This allows your heater to pull in preheated water from the outside tank. At the very least, the water is heated up to ambient temperatures which will be much warmer than ground water temperature. If your ground water is 60°, and the ambient temperature is 90° outside, and your water heater is set to 120° you could cut your hot water energy useage (and bill) by 50%. All you would need is a tank and some PEX tubing and fittings!

The problem arises when you have freezing conditions. Even still, you could use the previous sytem for the warm months of the year!

As a side note, the cold water could even be passed through a heat exchanger in the house before going to the tank to help cool off your house.

toyobug · 09-23-08, 05:37 AM

This sounds like a really good idea. You could always have an inline valve in the line coming from your outside tank to shut it off during the winter. I guess you would want to drain out some of the water from the outside tank to prevent it from freezing.

When a friend of mine built his house, he designed it in such a way that ALL of the plumbing was on ONE wall. This saved on initial costs. In addition he placed his hot water heater in the attic, for the same reason you mentioned. (we live in south Mississippi).

Do you have any good links to purchase solar water heaters?

Daox · 09-23-08, 07:53 AM

That sounds like a nice setup your friend has.

I had a few links to sites but a few of them no longer sell everything they used to. I haven't ordered from any of them yet. Solar Direct has a much larger selection as well as being able to buy individual parts.

Solar Direct
Solar Energy

toyobug · 09-23-08, 08:10 AM

Thanks.

I'll check those links out.

webaware · 05-03-13, 08:27 AM

I'm planning on making some solar water heater panels out of old radiators, painted black, placed in boxes lined with expanded polyurethane sheeting, covered with 'twinwall' acrylic sheeting.
The plan is for the water in the panels to circulate through the indirect loop inside an immersion tank. This tank will provide pre-warmed water to the main immersion tank in the house.
The pre-warming immersion tank, and panels are all to sit on a flat roof section of the house (immersion tank in a well lagged box).
I'd like to have the solar heated water loop driven by conduction. I thought that a vertical 2m 22mm copper pipe connected to the hot-out side of the panel array might give sufficient draw to power the loop.
Any thoughts or useful links please.

Daox · 05-30-13, 01:20 PM

It doesn't sound like it'll work incredibly well to me. What kind of radiators are you talking about? The inlet and outlet need to have that vertical height differential to give you the convection that you need. A setup with a small pump will really increase efficiency though by keeping the whole system cooler, thus loosing less heat to the environment.

nexsuperne · 06-01-13, 04:51 PM

Don't use plastic sheeting. 4mm single plate glass is far better. Use rockwall behind the single plane non-convector fin radiator and make the box just big enough to get some rockwall around the sides. Mount the panel below the tank, with the top outlet from the matt black radiator to the top of your indirect coil. It shouldn't thermosyphon after sunset if the panel is low enough. Optimum angle is whatever your latitude is minus 15 degrees for summer and plus 15 degrees for winter. I guess you're in the northern hemisphere, so angle your panel to the south.

webaware · 07-15-13, 12:25 PM

Thanks for the feedback, guys!
I'm going to take the advice to pump rather than gravity feed.
New plan is to have a PV panel, 12V Leisure battery, car-plugin 12vdc:230ac inverter running the pump. A little control circuitry should only run the pump when the panel's generating sufficient power.

Regarding glass v plastic - I've found a source of reject double glazing panels (mismeasured etc.). I'm going to see if I can use them.

nexsuperne · 07-15-13, 01:27 PM

Webaware, why use an inverter? You will be loosing at least 10% in efficiency instantly. Get a 12 volt 1/2" bsp threaded diaphragm pump, like a shurflo or similar from ebay for about £40. Thats what I did, and it will pump up to 30 metres head height! My main tank is 12 metres above the wood burner, and it shifts water at 12 litres a minute with ease.

webaware · 07-17-13, 04:07 AM

I didn't know 12V pumps were available - thanks for that!

09-19-08, 12:24 PM	#1
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	Simple and cheap solar hot water idea IMO solar hot water should be used pretty much everywhere. This is a great place to start and doesn't have to be expensive. In fact, you don't even really need to go with solar commercial products. Here is a rough idea I have. If you live in a warm climate it could be as simple as running a cold water line to a black painted tank in your yard or on the roof. You then run an outlet line from that tank to the water heater. This allows your heater to pull in preheated water from the outside tank. At the very least, the water is heated up to ambient temperatures which will be much warmer than ground water temperature. If your ground water is 60°, and the ambient temperature is 90° outside, and your water heater is set to 120° you could cut your hot water energy useage (and bill) by 50%. All you would need is a tank and some PEX tubing and fittings! The problem arises when you have freezing conditions. Even still, you could use the previous sytem for the warm months of the year! As a side note, the cold water could even be passed through a heat exchanger in the house before going to the tank to help cool off your house. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

09-23-08, 07:53 AM	#3
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	That sounds like a nice setup your friend has. I had a few links to sites but a few of them no longer sell everything they used to. I haven't ordered from any of them yet. Solar Direct has a much larger selection as well as being able to buy individual parts. Solar Direct Solar Energy __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

05-03-13, 08:27 AM	#5
webaware Lurking Renovator Join Date: Mar 2011 Location: wales, uk Posts: 9 Thanks: 6 Thanked 0 Times in 0 Posts	Convection Driven Solar Water Heater Advice Wanted I'm planning on making some solar water heater panels out of old radiators, painted black, placed in boxes lined with expanded polyurethane sheeting, covered with 'twinwall' acrylic sheeting. The plan is for the water in the panels to circulate through the indirect loop inside an immersion tank. This tank will provide pre-warmed water to the main immersion tank in the house. The pre-warming immersion tank, and panels are all to sit on a flat roof section of the house (immersion tank in a well lagged box). I'd like to have the solar heated water loop driven by conduction. I thought that a vertical 2m 22mm copper pipe connected to the hot-out side of the panel array might give sufficient draw to power the loop. Any thoughts or useful links please.

05-30-13, 01:20 PM	#6
Daox Administrator Join Date: Aug 2008 Location: Germantown, WI Posts: 5,525 Thanks: 1,162 Thanked 374 Times in 305 Posts	It doesn't sound like it'll work incredibly well to me. What kind of radiators are you talking about? The inlet and outlet need to have that vertical height differential to give you the convection that you need. A setup with a small pump will really increase efficiency though by keeping the whole system cooler, thus loosing less heat to the environment. __________________ Current project - To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. & To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

09-23-08, 05:37 AM	#2
toyobug avid DIY'r Join Date: Sep 2008 Location: MS. Gulf Coast Posts: 154 Thanks: 0 Thanked 1 Time in 1 Post	This sounds like a really good idea. You could always have an inline valve in the line coming from your outside tank to shut it off during the winter. I guess you would want to drain out some of the water from the outside tank to prevent it from freezing. When a friend of mine built his house, he designed it in such a way that ALL of the plumbing was on ONE wall. This saved on initial costs. In addition he placed his hot water heater in the attic, for the same reason you mentioned. (we live in south Mississippi). Do you have any good links to purchase solar water heaters?

09-23-08, 08:10 AM	#4
toyobug avid DIY'r Join Date: Sep 2008 Location: MS. Gulf Coast Posts: 154 Thanks: 0 Thanked 1 Time in 1 Post	Thanks. I'll check those links out.

06-01-13, 04:51 PM	#7
nexsuperne Helper EcoRenovator Join Date: Feb 2012 Location: 30 miles east of London, UK Posts: 88 Thanks: 12 Thanked 19 Times in 18 Posts	Don't use plastic sheeting. 4mm single plate glass is far better. Use rockwall behind the single plane non-convector fin radiator and make the box just big enough to get some rockwall around the sides. Mount the panel below the tank, with the top outlet from the matt black radiator to the top of your indirect coil. It shouldn't thermosyphon after sunset if the panel is low enough. Optimum angle is whatever your latitude is minus 15 degrees for summer and plus 15 degrees for winter. I guess you're in the northern hemisphere, so angle your panel to the south.

07-15-13, 12:25 PM	#8
webaware Lurking Renovator Join Date: Mar 2011 Location: wales, uk Posts: 9 Thanks: 6 Thanked 0 Times in 0 Posts	Thanks for the feedback, guys! I'm going to take the advice to pump rather than gravity feed. New plan is to have a PV panel, 12V Leisure battery, car-plugin 12vdc:230ac inverter running the pump. A little control circuitry should only run the pump when the panel's generating sufficient power. Regarding glass v plastic - I've found a source of reject double glazing panels (mismeasured etc.). I'm going to see if I can use them.

07-15-13, 01:27 PM	#9
nexsuperne Helper EcoRenovator Join Date: Feb 2012 Location: 30 miles east of London, UK Posts: 88 Thanks: 12 Thanked 19 Times in 18 Posts	Webaware, why use an inverter? You will be loosing at least 10% in efficiency instantly. Get a 12 volt 1/2" bsp threaded diaphragm pump, like a shurflo or similar from ebay for about £40. Thats what I did, and it will pump up to 30 metres head height! My main tank is 12 metres above the wood burner, and it shifts water at 12 litres a minute with ease.

07-17-13, 04:07 AM	#10
webaware Lurking Renovator Join Date: Mar 2011 Location: wales, uk Posts: 9 Thanks: 6 Thanked 0 Times in 0 Posts	I didn't know 12V pumps were available - thanks for that!