Tracking Solar Concentrator

Tracking the sun and concentrating it's energy is another form of utilizing the Sun's "Mega BTU's" that is available. It is some what more involved capturing the energy this way verses the fixed flat or evacuated tube collectors. Heating a large volumes of water to high temperatures, and storing the energy is the goal here. It's nothing new. Not my idea. It's been going on for more than a hundred years. It is being done more and more, as the many photos below show. There is one that has been in production for years, it is www.acrosolarlasers.com and Dennis Coefield, founder, has been building these dish for 20 years or more. . I have been building one for a while and have repeatedly changed designs. I am privileged to be part of a BETA program with Practical Solar, www.practicalsolar.com. The installation of their tracking heliostats is simple and has performed flawlessly day after day focusing a square of sunlight on a target.. Once into production mode, they will very affordable, allowing people to have 10 or 20 of these 3x3 mirrored heliostats installed in different locations through out a property, all focusing the sun either on to one spot, large or small, or lighting the windows on the north side of the house or both. Below is the Practical Solar team. (Left to right): Rachel Rohr, Dave Howell, and Bruce Rohr, inventor of the heliostat and it's unique tracking program . The tracking system is by a computer program, so it is unaffected by weather such as cloud cover. We have installed six of the heliostats and focusing on one receiver. Results to follow any day.

So where am I with my parabolic dish? The one that I have built is a 9 diam. aluminum G band satellite dish. Not so common any more. I covered it with 2 mil Mylar from a hydroponics site. It worked great but didn't' weather well through a winter. It might have been the glue was to much. It was 3M #77 spray adhesive. I have built several different types of receivers. The latest one did work better than previous ones, but I am going to build a fourth one that will be much larger so the sun's focal point will be larger to cover a larger heating area. I've been heating 30 gallons of 70 degree water to 140 in an hour and half. I have had a lot of trouble coming up with a motor drive for the east to west rotation. I have tried several different mechanisms. I would like to build a cradle such as the one on the Spain dishes below. Closer to the ground, sturdier.

October 4, 2008 We set up six of the heliostats and focused all 48 mirrors on to a receiver that I mounted on a structure approximately 12' high off the ground. The receiver I made out of heavy sheet aluminum, with 50' of copper coil attached to it, though not soldered or even that firmly attached. I insulated the back of it and put a piece of glass over the front of it. It seemed to work well. The 30 gallons of water was at 51.8 F and with in4 hours, it was 140F. For domestic water use, this is very adequate, but the output needs to be higher to heat the large 800 gallon tank.

The 800 gallon hot water storage tank requires 380,000 BTU's to raise the temperature from 100 F to 160 F. One square meter of sun's energy is equal to 3200 BTU's in a perfect 100% effecient collection. If you were to collect 50% of that, then that would be 1600 BTU's per hour that you could harness. The heliostat array is 48 sq ft or 5.5 +/- sq meters = 8800 BTU's at 50% collection. If that was the case, it would take 43 hours to heat the water in the tank. If we tripled the size of the array 144 sq ft by adding more mirrors, we would reduce the charging time to 14.8 hours.

Spain has built 6 of these very large dishes that are powering sterling engines directly off the heat generated. Evidently, 10 kw a piece. That is substantial but no mega watts.

Above is the Sunflower, roof top tracking concentrator. They just received UL approval for the public. Individual mirrors track the sun.