Inspired by Nature

Solar Heating System at Garber Residence

Wednesday, March 14, 2012
Inspiramental Blog

Robin and I are happy to have finally turned the majority of our water heating over to the sun!

We’ve accomplished this by installing solar heat collectors, circulation loops, heat exchangers, and storage tanks.  Normally, one heat exchanger, one solar storage tank would suffice, but we’re interested in seeing first-hand the performance of the new poly collectors that just came to market in 2011.

Panels 1

As of 12 March 2012 our residential solar water heating system is pretty well wrapped up.  We haven’t finished insulating because we may be able to use some fittings left-over after our next solar water heating installation on Gibraltar Island.

We installed two parallel systems in order to compare the different technologies.  As of this record, 13 March 2012, they have been keeping pace.  Both 40 gallon storage tanks are exactly the same at 121.1 degrees Fahrenheit.

One (ET) collects the sun’s heat via a glass and copper Evacuated Tube collector and transmits that heat through water in ¾” K soft copper tubes to the basement.  The other (FP) is a polymeric Flat Plate collector transmitting the solar heated water through PEX tubing.

The net aperture of the ET is 33 ft2.
The net aperture of the FP is 40 ft2.

The ET is rated by SRCC to perform at 33,900 BTUs on a clear day.
The FP is rated by SRCC to perform at 32,000 BTUs on a clear day.

Here are the links to the SRCC data if you’re looking for more details:

Panels 2

The systems are the same except for the collectors and piping material.  I expect that the ET will outperform the FP in the winter and probably annually.  However, there is a significant price difference between the two, especially due to the ability to use PEX tubing rather than copper tubing, which is why I’m excited about the new poly collectors.

In these systems food grade glycol is circulated between the collectors and the heat exchangers.  Potable water is circulated between the heat exchangers and 40 gallon solar storage tanks.  Thus preheating the water before it goes into the propane water heater.  Right now when hot water is drawn from the propane heater instead of being refilled with 54 degree water it will be refilled with 120 degree water.  In summer the solar preheat should be up to 150 or 160.  We’ve installed a tempering valve to insure that the water never reaches a faucet greater than 130 degrees.

Sam Garber

You can get a step by step look at all the steps to the project and more final photos on our Flickr account here.