Ive started my Solar hot water project

Share with us your alternative energy ideas and projects. Tell us about your experiments, no matter how far-fetched they may seem.

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Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Sat Jul 16, 2011 2:46 pm

I live in Florida in a doublewide (alone) , and plan on never having to use the electric water heater again. Fortunately being alone, I dont use alot of hot water at any one time . Today, i built the 36x36" wooden box out of 2x12's and 1/2" plywood back for which a 300' roll of 3/4" Pex-B high temp. tubing will sit in . Its rated at 200f. @ 100 psig and i plan on regulating the amount of suns rays into the Pex Collector so i get approx. 120 f. leaving water temp. The absorber will be a thick piece of sheetmetal painted high temp. flat black which the Pex coil will sit on. Since UV light destroys plastic tubing in no time, i will wrap a single layer of h.d. tin foil so no UV light hits the raw Pex coil ( I suppose ill paint that tin foil flat black also , although its not meant to conduct heat to the Pex tubing ) . For the face of the box, I have a 36x36" double pane Low E window in sash that will sit on the face of the Box . Low E glass lets maximum suns rays thru but lets very little heat exit via the glass which means it will be a good greehouse effect. I plan on using CPVC 3/4" straight lengths rated at 180 f. @ 100 psig running from the Collector Box to the Water Heater which is about 8' above the Collector with a 25' horizontal run . I was going to go the thermosyphon route but i dont think it will work very well with the long run and 300' coiled Pex tubing...so, Ill simply splice the CPVC into the supply water line right off the water heater with a bypass valve arrangement . The line pressure will force the water out of the Pex tubing and directly into the supply line each time a hot water faucet is opened in the house.

Once i get the project totally done, ill post some operating data for consideration. Luckily all i require for a daily shower is about 5-6 gallons of water which is what 300' of 3/4" Pex tubing holds so i can eliminate any kind of a storage tank as well as circ. pump and controls.
My only concern is the stagnation temp of the water sitting in the Pex tubing all day long till i take my shower at 6 pm, so, to limit the amount of suns rays coming into the Collector Box, I thought id hook on a large piece of shiny sheetmetal (of varying sizes) to regulate the suns effect on a seasonal basis.

Any thoughts, tips, etc... appreciated .


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flcruising
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Wed Jul 20, 2011 10:21 am

Take some pictures and keep us posted!
[color=blue]Aaron[/color]

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Wed Jul 20, 2011 10:40 am

Hello to my neighbor Aaron ! I finally got around to starting this project . Upon further consideration, im not going to just splice into the hot water supply line off the water heater, but rather, first try thermosyphoning into the water heater from the Solar Collector ....as im told theres a risk of Legonaires disease of you dont keep the tank at 120 f. If it doesnt thermosyphon once im done, then ill opt for a 12 vdc 350 gpm 1.8 amp hi. temp. Pump (with 1/2" threads) ive seen on Ebay for a measily $55 .00 . So far, I have the 36x36" Collector Box built from 2x12's , have the 300' Coil of Pex Tubing in it and wrapped with a layer of h.d. Tin Foil to guard the Pex from the Suns UV light , and have the entire Box and Tin Foil painted a high-temp. Flat Black Paint. Its sitting out in the sun right now as I type to emit the smell and smoke and to get the paint firmly adhered before I put the Double Pane Window Sash over the top of the Box , which ill do tomorrow . Ill run the CPVC tubing in the crawl to the Hot Water and connect everything this week yet, i hope. Will keep everyone posted and Im taking a video as it progresses. David.

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DaveyB
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Location: Peoria, AZ

Thu Jul 21, 2011 1:54 am

If you add the pump, you may want to consider adding a solar panel to generate the power for it. Since it's a 12v pump, you would need to use a converter to convert 120v AC to 12v DC, and that thing will suck up electricity whether the pump is drawing power or not. A solar panel will only generate electricity, at the needed voltage, when the sun us shining, and when it isn't, then your water heater won't be working either so the pump should be off !!

Just a though!

DaveyB
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Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Thu Jul 21, 2011 8:27 am

DaveyB wrote:If you add the pump, you may want to consider adding a solar panel to generate the power for it. Since it's a 12v pump, you would need to use a converter to convert 120v AC to 12v DC, and that thing will suck up electricity whether the pump is drawing power or not. A solar panel will only generate electricity, at the needed voltage, when the sun us shining, and when it isn't, then your water heater won't be working either so the pump should be off !!

Just a though!

DaveyB

I appreciate the tip . I was going to use the 2 almost new RV Deep Cell Batteries i have in the garage and have been keeping charged. Each is 100 amp/hours . I figured id trickle charge them overnight once per week ; since the draw on the pump is only 1.8 amps at 12 vdc and id only be running the pump during daylight hours.. they wont be taxing the batteries much at all.


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flcruising
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Thu Jul 21, 2011 2:38 pm

I would keep K.I.S.S in mind - keep it simple stupid (not indicating you).

The solar panel is a good idea and it would only work with the sun shining which is when the water would need moving anyways. But actually, DaveyB, solar panels generate DC voltage, so a simple solar car battery charger/maintainer may be all that's needed, and not an inverter.
[color=blue]Aaron[/color]

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Fri Jul 22, 2011 8:29 am

Update. Did a preliminary check of the Solar Collector effectiveness by simply filling the Pex Tubing Coil while the entire Collector Box was just sitting on my driveway ; filled the Pex using Well water at 60 f. and after 5 hours on a partly cloudy day of 92 f. outside....the water was at 122 f. I had expected it to be higher and i think the tin foil wrapped around the Pex Coil to ward off UV rays might be inhibiting good solar absorption , plus, the window sash was just sitting loosely on the top and not permanently sealed so i was probably allowing some heat to escape . Mfr's Pex data says Pex cant be painted but im tempted to paint a small section of it using Krylon plastic paint good to 200 f. and let it sit in the box for a few sunny days to see what happens.

Any thoughts ? Thanks.

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flcruising
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Fri Jul 22, 2011 11:22 am

Why did you go with PEX? Temperature?

Definitely the foil is hindering the heat absorption. I suggest you replace the PEX with HDPE. Black is very common, but the difficulty may be the temperature. They do have it 200psi, which may work for you since your pressures are much lower even at a higher temperature. So a 200psi rate pipe @ 73* may be a 100psi pipe @ 120*.

Other suggestion would be to single glaze as the low-e is rejecting the radiant heat you are trying to capture, and the glazing is mainly for protecting in cold climates. Think about alternatively applying a UV blocking window film as it may allow you to remove the foil and achieve greater life from the pex, but it may still work against you and potentially reject the infrared you need to reach the pipe.
[color=blue]Aaron[/color]

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Sat Jul 23, 2011 7:48 am

Aaron, I talked to a guy that has the same project as myself installed and operating...using a big roll of Pex-B ... and he said he painted his Pex flat black and its held up very well over time...so, I just painted mine in hopes it will offer some UV protection. I went with Low E glass because I read the suns rays get thru good but doesnt let heat escape very much , so i thought it would be ideal for my Wooden Collector Box. Anyways...I just painted the Pex Coil again this morning and have it set in position against the house wall waiting for the sun to round to bake it good, then ill put the Double Pane Window on later and retake the temp. inside the box and of the exit water.
Ill post the data.

I did look into the black Polytubing at Farmers Supply but concluded it wouldnt be suitable for me.

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flcruising
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Mon Jul 25, 2011 10:20 am

Visible light is not what you are trying to capture. Radiant (infrared) heat is the spectrum from the sunlight that you need. Low-E glass is counterproductive.

Read here - http://en.wikipedia.org/wiki/Low_emissivity

Read in particular the last sentence of paragraph 1 of 'Low-emissivity windows'
[color=blue]Aaron[/color]

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Mon Jul 25, 2011 10:35 am

I see. Well., live and learn i guess. Anyway, got the Collector Box completed and filled it with cold well water at 58 f. Put the Collector Box on a 30 degree angle ... its a mostly sunny day , 90 f. outside, left it for 5 hours . Took temp of Box inside : 160 f. Took temp. of exiting water : 158 f. Decided to simply splice the Collector Water directly into the house hot water line instead of using the Water Heater as a Storage Tank (with pump) -- will have to be very careful to cool it down at the shower faucets ...but I expect ill have hot enough water for showers in our winter months as all i require is 95 f. shower water ,ideally. Its my first solar project and if i do it again, ill go a more efficient route with different type of glass and probably another 300' of Collector Tubing.

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flcruising
Posts: 606
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Location: Florida Panhandle

Tue Jul 26, 2011 10:15 am

Where's the pictures?
[color=blue]Aaron[/color]

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Tue Jul 26, 2011 11:34 am

flcruising wrote:Where's the pictures?

Im waiting till ive spliced it into the house hot water supply pipe then im going to take a video of the whole thing . Ill post the URL here. I tested the Collector again at 10:30 a.m. this morning under mostly cloudy skies , 80 f. outside .... and the Box as well as the exiting water was at 121 f. The real test comes this winter .

Imcalleddavid
Posts: 9
Joined: Sat Jul 16, 2011 2:24 pm

Mon Aug 01, 2011 8:20 am


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flcruising
Posts: 606
Joined: Mon Dec 03, 2007 2:18 pm
Location: Florida Panhandle

Mon Aug 01, 2011 11:58 am

Not to be critical, but your design has 1 huge flaw - most of the piping is not exposed to the sun's rays!

You would gain ALOT more efficiency by going larger with your box and coiling the pipe up in it so every coil has sun exposure.

http://rimstar.org/renewnrg/solar_pool_ ... diy_fp.htm

Lot's of useful information here - http://builditsolar.com/
[color=blue]Aaron[/color]

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