Saturday, May 19, 2012
Today, as we have for the last 3 years, we put into practice our "green building" commitment by coating our Organic Food Depot grocery store roof white in Virginia Beach.
It is a fairly well established fact that having a white roof reduces heat load by 30% - 40% http://www.gizmag.com/white-roof-heat-island/21758/, and I know on our own house which has a white roof, it's what makes the difference between whether our undersized A/C system works or not.
For our grocery stores, the internal equipment heat load plus the external solar load can overwhelm an A/C unit, leading to premature failure, an expensive replacement I can tell you from experience. Therefore, anything we can do to lessen the summer heat load in a cost effective manner, is something we look for, and coating our roof white certainly makes a huge difference.
However, we don't "paint" our roof white, both because runoff might affect nearby wetlands, and because we actually want the coating to wash off by Winter.
So we use Kool Ray Liquid Shade from Continental Products.
It's made for greenhouses, is non-toxic and is designed to wash off over time. http://www.continentalprod.com/greenhouse/kool/kool.htm
As you can see from this first photo, after a winter, most of the previous year's coating has been removed by rain. This gives us radiant absorption during the winter. The roof, being back to black, acts like a solar collector. We get the best of both worlds - cooling in the summer, heat in the winter.
It took 4 of us about half a day to roll on the new coating. The roof is a black, 8,000 sq. ft. EPDM rubber membrane. We used three 5-gallon pails, mixed 1:1 with water, and a small amount of "extra stick" for longer adhesion. Cost was minimal, around $500.
The result is bright white and reflects sunlight well. The A/C units on the roof which had been running when we started, stopped during the installation, and only ran sporadically the rest of the day, so clearly the coating had an immediate effect.
We know it works, though we haven't tried to quantified it precisely.
If all the businesses and even homeowners in Tidewater were to adopt white roofs, the savings in cooling costs would be substantial, not to mention the fact that we would no longer need to build new power plants.
Getting homeowners to make their roof white is probably not going to happen. It has no aesthetic appeal. Businesses, however, are another story, and the payback could be calculated.
Saturday, May 12, 2012
In an talk filmed at TED's offices, Amory Lovins of the Rocky Mt. Institute talks about his new book, "Reinventing Fire" and gives a well reasoned proposal for switching the U.S. from oil, gas and nuclear to Renewable Energy by 2050 without it costing the U.S. anything - in fact, saving literally trillions that we're going to spend following the "business as usual" route.
It's well worth the 27 minutes running time.
Wednesday, May 9, 2012
Tuesday, May 8, 2012
I found lots of advertisements with numbers, such this one from Zomeworks:
few years back
I had my windows replaced. The advertised savings was 35%. Silly me, I did not measure and compare the new and old performance factors. However, they really needed to be replaced anyway, as the old aluminum frames were very cold in the winter. There was a benefit, but since I didn't measure, I can't quantify it.
The Solar equinox was 20 March, so elevation was @ 36 degrees, azimuth: 180 degrees. Due solar South was checked at solar noon with a triangle, (11:03 on the 15 of Apr). If the shadow didn't lie within itself, I was out of alignment. I adjusted the frame until it was aligned. If you want to find out about solar noon, NOAA has a geo-location solar calculator that is really easy to use http://www.esrl.noaa.gov/gmd/grad/solcalc/.
The Enphase Envoy unit does the data logging, so that make measurement and tracking performance info accurate.
The Tracker rotated on a 68" x 1/2" conduit pipe. The bearings were three 3/4" PVC pipes strapped to a wooden frame that held the panel. It pivoted with ease and was adjusted once an hour by two 24" opposing ratcheting bar clamps. On the day of the test it was a bit windy, so I rigged a damping system using a 5 gallon water bucket and bungee cord attached to one side.
Because of the distance from the test rigs to the Enphase microinverters (which were on the roof), I used a 100 ft. extension cord and MC-4 connectors plugged into the correct connections.
The test results for the static mount showed the 1.0 KW produced a bell curve graph.
The tracking mount produced a 1.3 KW mesa shaped graph, and a 30% gain over the static mount.
The test was not perfect, it had location shading and connection losses, but the results were positive.
My test results show that a tracking system will have a gain of approximately 30% more measured power, as the advertised Zomeworks statement suggests, than a static mount system.
If you want to conduct your own experiment, contact me for further details.