By

Mark Ranum

400 feet of 1/2 inch poly pipe is coiled in a box constructed of 2x4 and 2x2 lumber with a 2 inch construction foam backing. Not pretty but the idea was to build it cheap, fast, and with a big payback ratio.

 

 

 

 

 

A sensor is placed on the output line of the solar panel. In this case it is just an indicator but this will be replaced with a control sensor. (a controller has yet to be ordered)

 

 

 

The finished unit with 6 mil plastic stretched over it. Note that the plastic is not clear but rather just what I had available on the farm at the time. Good old chucks of lath from a remodel project were used to secure the plastic. Nothing fancy! Note the legs on the end of the unit. Dumb idea as the unit needs to sit on side for stability! It's called learning on the run.

Most folks in the solar industry would undoubtedly laugh at this home-brew solar panel. It is crude for sure. However, it is currently pumping 150 F water into our "turned off" 80 gallon electric water heater. The calculated performance is an amazing 2500 BTU based on observed temperature rise and water flow. Bottom line is that it has supplied our total needs for hot water for a family of four on sunny days. An additional panel and another 80 gallons of storage hooked in series would probably yield enough hot water to get us through a couple days without the sun. A LP fired high efficiency unit (a project still sitting in the box) will be installed to boost and cover needs when the sun isn't sufficient.

• Total cost including the used circulation pump was under $100
• Total time for construction and installation was about 12 hours. (need to refine yet)
• Fair weather configuration only as it will not stand freezing temperatures. (water in collector)
• Needs to be configured with heat exchanger and non-toxic antifreeze for winter use.
• Observed temperatures exceed ratings for poly pipe. (perhaps PEX would be a better choice.)
• System is needing a differential controller ($150 for a good one) and is currently operating on a home built controller.

We will keep you posted on refinements and improvements to the system. Solar can be done by the average Joe and it can be done inexpensively. An interesting point in this little experiment is that things can happen if you get yourself out of the perfection mode and just get down to the doing of it. I had to grit my teeth as I did some less than perfect things while hastily throwing this panel together. Had I not done that, it would never have happened as time is extremely tight on this little farm.

 Well, on to the next project for the day!

Mark Ranum

The solar panel below is still working well when the sun is out. That has been a rare occasion lately during the best solar harvest hours of 10:00 AM to 3:00 PM each day. A homebuilt controller built out of surplus items is currently in use but it's accuracy is poor. The results are lost BTU's and times that the pump runs hot water to the panel instead of the other way around. When that happens, the panel becomes a huge radiator and releases bought and paid for heat to the environment. As soon as the budget allows, we will be installing a second panel and a differential controller that senses storage temperature and collector temperature. That controller will do the balancing act to make sure the right thing happens with the pump. Even with the current setup, our electric bill has been cut exactly in half! That means the system has already paid for itself in a little over a month of operation.

The experience so far with the hastily built panel has been surprisingly good. The addition of another panel and the controller should make it a great summertime energy saver. We'll have to see how well this system converts to a year round collector. For sure the "glazing" will have to be improved from the current 6 mil plastic to something that offers some thermal R value. I envision two layers of 6 mil greenhouse quality clear plastic with an air space between them. Insulation will also have to be added to the sides of the unit in addition to the back. None toxic antifreeze will replace the water in the collector loop and a homebuilt heat exchanger will need to be installed in the basement.

As it is right now, the panel has also come in handy for the farm fauna as one of our cats decided to have a litter of kittens under the panel. In case you are concerned, they are doing well.

Mark

The crude system built so hastily is performing great! It still churns out enough hot water to just meet our needs. Doubling the collector space and refining the storage would give us all the hot water we could want. One notable improvement would be to have the hot water from the panel enter the storage tank at the bottom. I'm thinking this would not allow the tank to stratify as much and would make better use of the 80 gallons storage space. Right now, it appears to heat just the top of the tank. Also, the definite weak points in the plumbing are the two washing machine hoses used to hook to the tank. I just noticed today that they have ballooned and will have to be replaced. The system will be shut down until I get the chance to do that. We will go with a higher quality hose. Overall, though, I can't believe how well this is working and how little attention it requires.

Mark