DIY Solar Collector Construction 101
 

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What follows are answers to some of the most basic, common questions that folks have as they begin thinking through the construction of their solar projects.  We've tried to keep these answers as concise as possible.  If your questions aren't covered here, if you want more information or you simply want to share your plans and connect with other solar enthusiasts, we encourage you to join the Yahoo Group Simply Solar!
 

 

I'm not sure what I want to build yet.  Where do I start?

 

If you haven't yet read through the Frequently Asked Questions, start there.  The FAQ page provides a lot of information to help you think through the type of project that you would like to build. Once you have a better idea of what you want to build, then come back to this Construction 101 page for tips on the actual construction.


Is building and installing a solar collector system difficult?

 

No!  More precisely, it certainly doesn't have to be.  While some collector designs can be challenging, there are very easily built design options that work great!  You certainly don't have to be an accomplished "do-it yourselfer" to build and install very efficient solar collectors.  The only power tools some designs require are an electric drill and possibly a jig saw!  All the parts and materials you'll need are readily available at your local hardware store or ordered on line.

 


Do you have step by step plans for easy to build, solar collectors?

 

Yes, this pictorial will take you though all the steps for building a very easy to construct, back pass, hot air collector:

http://www.builditsolar.com/Experimental/AirColTesting/TestingFirstGo.htm

This page details the construction of a basic hydronic (liquid) collector using copper tubing:

http://www.builditsolar.com/Projects/SpaceHeating/DHWplusSpace/CollectorConstruction.htm 

And this page details the construction of a very easy to build hydronic (liquid) collector using pex tubing (no copper pipe to buy and no soldering required!):

http://www.builditsolar.com/Experimental/PEXCollector/Construction.htm

 


What is PEX, where do I find it and how do I connect it?

Pex is the tubing that is often used in under floor radiant heat systems, to transport fluid to your solar panels and to collect heat inside some solar panels like these:

       

Pex is generally available in sizes from 3/8" up to 2".  Sizes most commonly used are 1/2" for runs up to 300 feet and 3/4" for longer runs.  Pex will handle temperatures up to 200 degrees, is flexible, easy to work with and will last 50 years or more.  Many brands, such as Mr. Pex from Pex Supply are also accepted for potable (drinking) water use.

Some types of pex include an oxygen barrier, which may increase the service life of cast iron pumps.  If your goal is to keep all oxygen out of your system, you'll want that feature.

One type of pex, called Pex-Al-Pex, has a layer of aluminum that allows the pex to hold its shape when bent.  Since it is less flexible, you may not want to pull Pex-Al-Pex through rafters in an under floor radiant heat project, but it is perfect for use running fluid to a collector and inside collectors (as long as care is taken to avoid high stagnation temperatures).

Pex is widely available.  If it's not at your local Home Depot or Lowes, you can order it on line at very competitive prices from sites like this one:  http://www.pexsupply.com.  

Pex can be connected in a variety of ways including push on fittings like Sharkbite or Gatorbite, compression, press, crimp, clamping and expander fittings. Sharkbite fittings are available at Home Depot or from sites like http://www.pexsupply.com/SharkBite-Push-Fit-Fittings-588000.

Sharkbites are the easiest to use, literally just pushing on to Pex, copper and PVC. They make a permanent, leak free connection and don't require any tools. Nothing could be easier! On the other hand, since crimping connections are less expensive, if you have a lot of connections to make (and you aren't using Pex-Al-Pex), it may be worth purchasing a crimping tool.  There are some great, "how to" videos that demonstrate each of your pex connection options here:  http://www.pexsupply.com/resources/videos

Some flavors of Pex-Al-Pex may have slightly different dimensions.  While folks are successfully using Sharkbites with 1/2" Pex-Al-Pex, you may want to consider using compression fittings like these:  http://www.pexsupply.com/PEX-Compression-Fittings-364000

For more information:
http://en.wikipedia.org/wiki/Cross-linked_polyethylene


What do you recommend to use for a clear glazing?

Suntuf is light, very easy to work with (cut and drill), tolerates high heat, is strong to the elements, inexpensive (less than $20 for a 8 foot X 26 inch piece), UV protected and readily available at most Home Depots.  Tuftex is carried at Lowes and is similar.  If your local Home Depot doesn't have Suntuf in stock, ask them where the closest store is that has Suntuf 8' X 26" clear roofing panel.  The SKU number they'll want is 282688.  If their answer is too far to drive, ask them to order it for you.  Most Home Depots are happy to.

You'll also need screws and wiggle strips.  Those you can order on line yourself from the Home Depot web site if you like.  Here are the links to everything you'll need:

The Glazing (clear, 8' X 26" panel):
http://www.homedepot.com/h_d1/N-5yc1vZ1xh7/R-100021329/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

The Screws:
http://www.homedepot.com/h_d1/N-5yc1vZ1xmv/R-100095071/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

And the Wiggle Strips:
http://www.homedepot.com/h_d1/N-5yc1vZ1xh7/R-100078282/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053


Suntuf is a great option for glazing, but it is by no means the only one.  Here is a great list with pros and cons of many glazing options:
http://www.builditsolar.com/Projects/SpaceHeating/Glazing.htm


How do I attach Suntuf to my frame?

       

Suntuf is light, easy to work with and makes an excellent, inexpensive glazing.  It can be drilled with a regular bit (though the Suntuf documentation recommends a stainless steel bit designed for metal) and it can be easily cut with hand or power tools.  Here are links for all the parts you will need to install SunTuf:

 The Glazing (clear, 8' X 26" panel):
http://www.homedepot.com/h_d1/N-5yc1vZ1xh7/R-100021329/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

The Screws:
http://www.homedepot.com/h_d1/N-5yc1vZ1xmv/R-100095071/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

And the Wiggle Strips:
http://www.homedepot.com/h_d1/N-5yc1vZ1xh7/R-100078282/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053

Here is how I went about attaching Suntuf to my frame:

1.  I began by attaching the wiggle strips to the top and bottom of the frame, with just enough screws to hold them in place:

 
I'm actually screwing in a support for the glazing here - 1 every 24 inches

 2.  Then I put the Suntuf on, a panel at a time:

 
Use a 1/4" bit to give the Suntuf room for thermal expansion when you pre drill the screw holes.

 These are the screws:

 

3.  Each panel overlaps the next (they are 26"), so just keep adding panels:


Two panels overlap at the center screw

 

View from bottom looking up

 


View from top looking down

 I am really impressed with the appearance of the finished product.

 

For more information, please see the Suntuf manual:
http://www.palramamericas.com/docs/upload/F409_Suntuf_Install-5-22-09.pdf

How do I choose a pump (and what do I need to attach it to PEX)?

In a drain back system, where water is pumped up to the collector and then drains back to your thermal storage tank when the pump shuts off, the most essential criteria for choosing a pump is maximum head pressure.  Maximum head pressure is the highest elevation a pump can lift water, so your pump has to have a higher rating than the distance in elevation from your pump to your panels.  For example, the Taco 009 pump has a head range of 35 feet, while the Taco 007 only has a head range of 10 feet.  If you decide to build a system where the fluid is always in the tubing (closed loop), head pressure is not an issue.

The second criteria is flow rate.  According to homepower.com, the optimum flow rate is .015 gallons per minute for each square foot of collector, or about 1/2 gallon per minute for each 4' X 8' collector.  There is plenty of margin in either direction, but if your flow rate is too low, your collector will run hotter and you will lose more heat out through the glazing, reducing efficiency.  Depending on the length of your tubing run and its diameter, you will lose flow velocity pumping the fluid through your tubing, so choose a pump with a flow rate higher than what the total square feet of collector indicate.  

One other thing to consider is choosing between cast iron and bronze pumps.  Bronze pumps are more expensive, but will not rust.  If your system has contact with air, or you are using tubing that doesn't have an oxygen barrier, the cast iron pump may eventually rust.

There are lots of pumps to choose from here:  http://www.pexsupply.com/Taco-Cast-Iron-Pumps-289000

When you purchase your pump, you will also need to buy two flanges.  These determine the size connector that the pump will accept.  The smallest flanges available for Taco pumps are 3/4 inch:  http://www.pexsupply.com/Taco-110-251F-3-4-Taco-Iron-Freedom-Flange-Pair-1973000-p

If you are connecting your pump with the 3/4" flanges above to 1/2 inch pex, here is what you will need:

The nipple hat screws into the flanges:  A4322075 Conversion Nipple, R20 x 3/4" NPT  (quantity 2)
http://www.pexsupply.com/Wirsbo-Uponor-A4322075-Conversion-Nipple-R20-x-3-4-NPT-2091000-p

The compression fitting for the pex that screws on to the R20 conversion nipple above:  A4020500 1/2" QS-style Fitting Assembly, R20 thread (quantity 2)
http://www.pexsupply.com/Wirsbo-Uponor-A4020500-1-2-QS-style-Fitting-Assembly-R20-thread-2073000-p

Of course, plumbers tape, available at your local Home Depot, is always a good idea to help ensure leak free threaded connections.


How do I turn the fan for a hot air collector or water pump for a hydronic collector on and off?

You can control the fan or pump by either using an inexpensive snap switch (around $7) or a differential controller.  You can find a variety of snap switches here (most guys use the one that turns on at 110 and off at 90):  https://www.pexsupply.com/pex/control/search?SEARCH_STRING=snap+disc

A common sense warning.  The 120 volts coming out of your electrical socket can seriously injure or kill.  Be absolutely positive that you have made proper connections, that there are no shorts, that everything is insulated and that you are using extreme care before plugging in your circuit!

Jeff, on our SimplySolar group, was kind enough to draw up these schematics to use with a snap switch:

Above, only a two wire extension cord is used.

 

If a three wire extension cord is used, you can optionally ground the fan or collector.


Another, easy and inexpensive option is to use an extension cord with a sensor built right in, preset to turn on at 95F and off at 83F:  Note that the outlet of this cable is not a regular AC outlet, so you may need to cut that off and wire your fan.

http://www.coolerguys.com/840556091769.html?productid=840556091769&channelid=FROOG

Here are two videos that Steven, from our SimplySolar group, was kind enough to put together that provide a great education and show the entire process.  The first explains the basic concepts of snap disk wiring and details the connections to be made.  The second Shows the actual wiring of a fan with the snap disk. In this example, the snap disk controls a regular AC outlet. That way it is easy to swap out fans by simply unplugging them from the wall outlet that is controlled by the snap disc.

 

 

 

 
 
How do I solder copper pipe?

If you are one of the many solar enthusiasts who don't consider yourself a "do-it yourselfer", soldering copper pipe is not an obstacle. You can connect copper pipe easily without ever having to learn to solder at all!  Simply use the readily available, push on Sharkbite connectors for secure, leak proof connections.  That said, learning to solder isn't hard at all. Here are the basic steps, followed by a video demonstration:

1.  Clean the joint faces really, really well with emery cloth or wire brush ... twice.

2.  Apply a thin layer of flux to the pipe and fitting, slide the pipe and fitting together and give the pipe or fitting a quarter turn.  Note - some folks get great results by only applying flux to the pipe, not the fitting.

3.  Measure out one pipe outside diameter's worth of solder and make a 90 degree bend.

4.  Relax.

5.  Apply the flame to the base of the fitting from the bottom and the solder from the top.

6.  Relax.

7.  Once the solder starts melting, immediately feed it in at the same spot without drawing it around, until the measured amount is consumed.  Then pull the solder and the flame away.  The joint will be completely filled (but will lack a cosmetic fillet).

To clean the metal surfaces until they are shinny (no oxidation to get in the way of the solder bond), you can use emery paper, fine sandpaper or a bush. Clean both the pipe and the fitting. You can buy inexpensive wire brushes just for this purpose which makes it fast and easy. Get the brushes for the size of pipe you plan to use. One female brush for the pipe end and one male brush for the fitting.

Then apply flux with a small brush - you just need a thin layer to prevent oxygen from getting at your clean metal.

To apply heat, use a propane torch sold at hardware stores for this purpose. Don't apply more heat than necessary.  The hottest part of the flame is the tip of the blue flame towards the middle of the main flame. Apply most of the heat to the thick fitting, not so much to the thin pipe and when the flux pops and bubbles, apply solder on the side away from the heat - that is the coolest place, so if it melts solder, the whole joint will be hot enough. The solder is drawn into the fitting on its own (capillary action). Solder flows towards the heat, so by heating the fitting more than the pipe, the solder will flow into it, even uphill! You don't need much solder - just one pipe diameter's worth.  Don't use too much heat or you will see the solder "boil" which makes a porous bond. Use enough heat to melt the solder and let it flow all around the bond, but no more.

Test for leaks. If it leaks, apply more heat and solder.

You can buy a kit that includes torch, propane, flux, solder, and brush to apply flux. Wire cleaning brushes are sold separately for the pipe size you are using.

You can't solder a pipe with water in it.  Even an occasional drip will cool the pipe and prevent the bond. The pipe and fitting must stay dry while you solder.

This short video take you through all the steps and demonstrates just how easy it is to solder copper pipe:



What's the easiest way to build a thermal storage tank?

 If you are generating more heat than you need while the sun is shining, or if you plan to heat your domestic hot water, you'll likely need a thermal storage tank.

 Fortunately, tanks can be easily and inexpensively built in place with readily available building supplies.  Here are complete construction details:  http://www.builditsolar.com/Projects/SpaceHeating/SolarShed/Tank/Tank.htm

And here is a YouTube video describing my thermal storage tank:

 


What do I need to install a trench out to my collector and what should be in the conduit?

Whether you are just digging down 8 inches and using glycol for freeze protection, or you are planning to dig below the frost line, you'll want to give careful thought to what you bury.  Once it is buried, you sure don't want to dig it up again!

One teenager and one adult dug and filled this 8 inch deep, 100 foot trench in one weekend by hand.

    

Here is a list of what is included in the 4" PVC sewer pipe conduit:

-  2 runs of 1/2" Pex-Al-Pex (wrapped with insulation)
-  6 runs of 22 gage speaker wire (5 to splice in for wired thermometers and 1 for the differential controller sensor)
-  1 run of electrical wire (I put an outdoor electrical outlet on one of the panel posts which was handy during the construction phase)
-  1 run of LMR 400 coaxial cable (nothing to do with solar, but I'm an Amateur Radio operator and it was a great opportunity to get another run of coax back to the woods).

If I had it to do over again, I'd put in 3/4" pex for better flow.

 

How do I install thermometers to monitor the temperature at various points in my system?

No matter what type of solar collectors we build, we all need temperature sensors to monitor how well they are working.  By having multiple sensors along the path of your fluid / air route, you can accurately determine the efficiency of your collector(s), how much heat you are losing in the run out to the collector and how well your heat transfer coil is working.  By isolating the performance of the collector without the other influences, we can do a much better job of comparing how well different collector designs work, as well as determining accurately the effects of any tweaks we make to our systems.  In addition to all that, it's very cool and a lot of fun to show your friends all the free heat you are capturing! 

Here is the display I have along my desk so that I can monitor multiple temperature points along my system at a glance:


I'm considering building a frame to hold the displays.

It had been unusually cloudy for almost the entire week so the readings are lower than normal.  Reading the white thermometers from left to right:

1.  Tank temperature (200 gallon) has already risen from 66 to 81.5 as of 10:46 AM.

2.  (Egg shaped thermometer)  fluid entering the first, 8' X 8' collector is 81.3  (minimal loss in journey through 100' trench)

3. Fluid exiting first collector / entering pex collector is 92.3

4.  Fluid exiting the pex collector is 121.1

5.  Internal pex collector temperature > 160.

So, my total temperature rise with the two collectors combined is about 40 degrees.

Installing temperature sensors is easy.  Since most of the points we are monitoring are a distance away, we have to lengthen the wire from the thermometer to the sensor.  While it may be tempting to get wireless thermometers, I recommend going the wired route.  You aren't going to want to go out in the dead of winter to change batteries.  Also, you will want to monitor multiple points and the wireless thermometers may interfere with each other. 

Any inexpensive wired thermometer will work.  There are lots to choose from under $10.  They are available at Target, Walmart, Home Depot, etc.  You can also order them on line here:  http://www.partshelf.com/wired-indoor-outdoor-thermometers.html

Here are the steps for installing your temperature sensors:

1.  Run wire, such as 22 gage speaker wire, from your display location to where you plan to attach a sensor.  If you need a lot of wire, with a little Goggling you can find 1,000 foot rolls on line for $40 - $60.

 
I included six runs of wire in my 100', buried, 4" PVC sewer pipe conduit.


2. Purchase your outdoor, wired thermometers.


3.  Cut the wire from the thermometer to the sensor:

 
5.  Strip the ends:

    


6.  Repeat the process with the speaker wire and twist the ends together:


7.  If you really would rather not solder, you can always simply twist on wire nuts and go to step 10.  Otherwise, hold your soldering iron against the wire so that it gets hot enough to take solder.  If you've never soldered wire before, don't worry, it's easy.  

 


8.  Touch your solder to the wire, not the tip of the iron.  These wires are small, heat quickly and are very easy to solder.  The solder will flow on to the wire:

     


9.  Wrap with electrical tape:

 


10.  Decide on the location that you want to monitor, pull the insulation away and tape the sensor against your pipe with electrical tape:

     


11.  Cover with insulation and tape the insulation with electrical tape to hold it together:

 


12.  Repeat steps 5 - 9 to connect the sensor wire end to the other end of the speaker wire.


What is an easy, inexpensive way to ensure my system never builds up pressure?

If you install a drain back system where the water drains directly back into a thermal storage tank that's not air tight (most aren't), your system will never build up pressure and you don't have to worry about it.  On the other hand, if you have a system that uses a heat exchanger and there isn't a place for the fluid to expand as it warms, there will be some pressure build up.  

You can easily accommodate that in two ways.  The most conventional approach is to use an expansion tank.  I started out with one like this:

They are available here, http://www.pexsupply.com/Expansion-Tanks-353000, and the smallest ones ($20 - $30) work fine for our purposes.

The only trouble with the expansion tank is that I couldn't see or monitor my flow rate and what was happening with my system.  As an alternative, I came up with this approach; which only costs as much as an old iced tea jar, guarantees your system will never build up pressure and as an added benefit, purges any air that may find its way into your system:

Here, the pex tubing feeding the pump (behind the jar) draws water out of the container.  Fluid returning after it has passed through the coil in the thermal storage tank empties back into the jar.  It is important that both ends of the pex stay below the water level or some of your fluid may siphon back and over flow the jar when the pump shuts off.  My jar happens to be at about the lowest point in the system, but works fine.

Monitoring your flow rate is easy.  While your pump is running, just pull the returning pex pipe out of the jar and time how long it takes to fill a small glass.

I've been using this approach since August, 2009 and it is working fine.  I keep an eye on the volume in the jar, which fluctuates with temperature, but seldom requires topping off.
 


How do I build a frame for my collector?

Building a collector frame is easy.  It's really nothing more than an insulated box with something clear on top.  All the information for building mine is included here:  http://www.n3fjp.com/solar/BigProject/BigProject.htm


What is a differential controller and how do I install it?

An electronic switch that turns off or on based on the difference between two temperatures. In a solar hot water system, the controller measures the temperature at the collector and compares it to the water temperature in a storage tank to turn the pump on or off. 
 

SimplySolar - Solar Forum and E-mail Groups!

It turns out that there are other folks like me who also enjoy sharing ideas and learning from each other's experiments!  If you have an interest in brainstorming solar projects that are easy and inexpensive to build and neighborhood friendly, or want some help with a project that you have underway, please join us!

I originally set up an e-mail group - SimplySolar, for that purpose.  The e-mail group has served us well, but with overwhelming growth and interest in the e-mail group, to better keep content organized and give members the option to easily follow only the threads that interest them, we have just set up a new Simply Solar on line forum!  SimplySolar is about brainstorming and sharing ways to implement solar heat in easy ways that the average homeowner, who may not be much of a "do-it-yourselfer" (like me), can use to put money back in their pockets, green back in the environment and have a lot of fun along the way!  If solar excites you, we would love to have you join our forum:

Click to visit or join the Simply Solar Forum