Friday, May 16, 2008

My Solar Water Heating Project

My interest in renewable energy has led to experiments with solar electricity and to home heating with bio-fuels, so I guess it’s only natural that I would want to experiment with solar water heating as well. My latest project is an attempt to build a solar-powered water heater for my above-ground swimming pool. I’m not concerned with storing hot water, so I won’t need a tank. I just want to be able to raise the water temperature in the pool during the day.

I started with a plan to pump water from the pool, circulate it through tubing where it would be heated by the sun, and return the heated water back into the pool. I planned to mount PVC tubing to the side of a storage shed, and to paint the tubing black to increase its ability to absorb the sun’s heat. As the experiment progressed, family members hinted that the backyard was beginning to look like a wastewater treatment plant. I had to admit that they were right, and I decided to change my approach. Since the storage shed has an insulated ceiling, I decided to take advantage of the heat that builds up in the attic. Instead of mounting the tubing on the side of the shed, I’ve mounted it to the inside of the roof. I currently have 120 feet of 1” PVC pipe installed, and I’ll add as much as 200 feet more if necessary. The cost for the tubing is $2.42 per 10 foot section. I’ve purchased a small pump, and it seems to be able to circulate the water. I won’t know how well the system works until I can test it on a hot day. I’m currently using a 55 gallon plastic drum as a substitute for the pool.

Mounting the tubing in the attic means that it will be out of sight and out of mind during the winter. I won’t have to clean around and under the pipe array. I’ll just have to make sure that the pipes are drained, and gravity will help with that. In addition to its use as a pool water heater, I also have the option of using it as a solar-heated shower. I can make that conversion by connecting a garden hose to the pipe array, instead of pumping water from the pool. Regulating the amount of flow should also regulate the water temperature. The entire project will cost less than $300.00, and it should last for years. I’ll post additional details later, but here are some pictures of the project as it stands today.





Many thanks to Solar Gary for ideas and advice on solar water heating strategies. Anyone considering a related project should check out his website for ideas: http://www.builditsolar.com/

John

1 comment:

Solar John said...

Progress Report:

I was able to test the system today and was somewhat pleased by the results. I draw water from the pool, pass it through 160 feet of PVC tubing in the roof of my storage shed, and return the heated water to the pool. I measured a temperature increase (water in vs. water out) of about 3 degrees. This may not seem like much, but the steady stream of water returning to the pool seems a lot warmer than the small measured increase. The overall temperature of the pool water increased in time, but it's hard to say how much of that was the result of the solar heating system and how much of it was due to the direct heating of the pool by the sun.

The outside temperature today was in the high 80's. I'm sure system performance will improve as the outside temperature increases later this summer. Still, I'm going to add pvc tubing, which will also improve performance. I'll add 40 feet to the 160 feet of pvc tubing already installed. A warmer day and more tubing is sure to make a big difference. Check back later for another performance report. sj