Big, 24′ X 8′ Solar Collector Using PEX Tubing – Step by Step How to Build
This video shows step by step how I built my 24′ X 8′ solar collector, which uses pex tubing instead of copper. By using pex, it is much easier to build and …
25 Responses to Big, 24′ X 8′ Solar Collector Using PEX Tubing – Step by Step How to Build
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Hi Dennis. Yes, that is at one gallon a minute. I have a spreadsheet that does the calculation. Yourube won’t let me post links, but if you join SimplySolar, I can share it from there.
G. Scott Davis
March 15, 2013 at 4:16 am
You say the pex system gave a 30 degree rise, Fahrenheit.
Have you worked out the power generated?
I guess you need to know the quantity of water heated 30 degrees in one minute.
I’m not that bright to work this out but wonder if you did?
Nice projects!
Dennis yoj
March 15, 2013 at 4:51 am
I’m Working around the character limit with a self reply. The flashing is then painted. In my working with Pex for radiant floor heating, I found it to be a tough to wrestle material so I’d consider a concentric circle pattern or some thing to reduce the fight. For your shape I’d consider a split into two spirals that exit at their centers joining 4 the return. That would also mean slower processing through the array (higher temp) but faster transit back to the Tank (I think - it is late :^) )
oxenpaul
March 15, 2013 at 5:28 am
A thought for those that follow. The initial heat-up period to get the collector up to a high enough temp to get started would be extended by having to cook that plywood anew every day. Evacuated tube makers try to reduce their internal mass 4 faster starts – losing less net heat to warm up. So, I wonder if you could have ditched the second layer of plywood and gotten thicker insulation then depressed into it a path for the pex (3/4 of the diameter say) then cap with flashing having a 1/4 dent.
oxenpaul
March 15, 2013 at 6:25 am
I favor basking in direct sunlight like one would enjoy standing in front of a woodstove . I use mirrors , that is it.. I stand behind my window or sliding glass door and let as many mirrors reflect sunlgiht toward me. Same can be applied to a smaller solar collector that can hit as high as 500 degree F. CSP really means way high temperature not just 200 degrees. You will need Pyrex glass for your collector that can handle higher temp for heating circulated air .
junkyardnut
March 15, 2013 at 7:14 am
Hi VederchiHarry,
Typical collectors have an efficiency of about 50%. I agree, the pex collector is running less, but I think the similar CPVC design has remedied that, Please see my later CPVC collector video. Gary over at Build It Solar did a side by side comparision with Copper / Aluminum and they were almost identical! I think this PEX version could be made more efficient with additional, parallel runs as well, mirrioring the CPVC design.
G. Scott Davis
March 15, 2013 at 8:09 am
area = 192 sq feet.
solar power = 100 W/sq feet/hour (best part of the day)
time = 4 hours
maximum solar energy = 192sq feet x 100W/sqfeet/h x 4h = 76’800 W = 76.8 kW
Now, he says that it can warm up 200 gallons from 85 to 125°F in 4 hours. This requires an energy of 19.54 kW
Therefore the effiency is : 19.54/76.8 = around 25%
Best solar pannels have an effiency of 80% (and even up to 90%).
With 75%, we have : 75% x 192 sq feet x 100W/h/sq feet = around 14kW/h
VederchiHarry
March 15, 2013 at 8:53 am
Welcome, thanks for joining the group! It is much easier to discuss solar there where posts aren’t character constrained!
G. Scott Davis
March 15, 2013 at 9:26 am
Hi Brandon, thanks for your thoughts and interest!
I’m only losing 2F – 3F on the run back to the house. For example, if the fluid leaves the collector at 135F, it reaches the storage tank (more than 100 feet away) at about 132F.
G. Scott Davis
March 15, 2013 at 9:52 am
ha, I realized I’m really really interested in this… so I just joined your group!
BrandonFound
March 15, 2013 at 10:05 am
continued…… I used to install utilities and know most everything about conventional water heating systems (gas and electric, solar is my new frontier). Do a simple test, drill a small hole in the PEX just above where it runs underground. Drill another hole just above where the PEX leaves the soil or enters the house. Insert a small electric thermometer like you’d use to take a fever in both holes and do the math. If there’s concerning heat loss I believe I have a solution.
BrandonFound
March 15, 2013 at 11:02 am
I’m familiar with PEX and the material you used to insulate the PEX during the sub-terrain run to storage. Your going to be losing a lot more heat than you think if your app is as it is shown in this video. That insulation, while cheap, convenient and temptingly tailor made for the situation is only meant to keep scolding hot water warm on a journey no longer than 100 feet through structure that itself acts as a thermal insulator, IT IS DESIGNED TO LOSE HEAT ENERGY.
BrandonFound
March 15, 2013 at 12:00 pm
I’m not being sarcastic, I’m genuinely interested in what you have to say so do you care to enlighten us on an application that will yield closer to the 100% 14kW/h potential?
BrandonFound
March 15, 2013 at 12:48 pm
Yes, please see my thermal storage video for how I’m handling heat storage and heat transfer.
G. Scott Davis
March 15, 2013 at 1:06 pm
so do you have any suggestions on heat transfer and/or storage. I have below freezing temps. so I have to use a closed loop system with some sort of exchanger and potable hot water storage tank
Kubotajoesfarm
March 15, 2013 at 2:01 pm
I’m sorry but your model is not very efficient. You’re getting only 4.3 kW/h (efficiency = 25%) where You could get up to 14 kW/h with the same area.
VederchiHarry
March 15, 2013 at 2:05 pm
Yes, i agreee that closer spacing would work better. I’ve been thiking about putting a secon run in parallel between the first using two Ts, which would effectively give a 3″ spacing and also reduce flow resistance. Please see my CPVC collector video for the good performance I’m getting with more closely spaced tubes.
G. Scott Davis
March 15, 2013 at 3:05 pm
Hi, the pex is procted from UV in two ways. First, the SunTuf glazing is UV protected, so that keeps the harmful rays from hitting the pex. Second, the pex itself is painted black, which is a second layer of protection from UV rays.
G. Scott Davis
March 15, 2013 at 3:18 pm
you could have put the pipes much closer together and got loads more heat gain.
a10fjet
March 15, 2013 at 4:10 pm
lol wikipedia says pex deteriorates extremely fast in UV light. dunno if its true but if it is youre boned
a10fjet
March 15, 2013 at 4:59 pm
Hi Scott, I’d thought of doing it pretty much this way actually – just wanted your input as you’d actually made it.
I was thinking of using irrigation tubing as it’s really cheap, and it made of HDPE, which has almost twice the heat conductivity of PVC – just not completely convinced of it’s pressure when hot, as it’s not designed for this application.
Thanks for your reply.
Drafty01
March 15, 2013 at 5:05 pm
Hi, no under floor radiant heat is easy! It’s is really just building a pex collector in reverse. Simply run the pex under your floor, put flashing around it to help spread out the heat and then stuff batt insulation between the joists.
G. Scott Davis
March 15, 2013 at 5:35 pm
Hi Scott, great presentation. There are not many this good on Youtube, with all the facts & figures as well. I live in Auckland, NZ, and like you, would like to make a dent in the domestic hot water bill, as the price of power just keeps going up. Do you have a video for the underfloor heating system you put in? I was considering doing this, but seemed an expensive project to do.
Drafty01
March 15, 2013 at 6:18 pm
Hi, please take a look at my solar thermal storage vide. I think that will fill in the blanks.
G. Scott Davis
March 15, 2013 at 7:16 pm
Hi Scott
Great video and helping me as great deal..My question is can you show me your entire system and how it works from start to finish.. Maybe a diagram? How do you keep your hot water and in what? Thanks for doing these vids its a big help to me as I am getting started on saving money on utilities..
John Cline
March 15, 2013 at 7:24 pm