Sanyo Modules Guaranteed Power

You Get Watt You Pay For and More!

A 180 watt Sanyo module, supplied by SunWize, produces a minimum of 180 watts - backed up with individual module test data!

• Approximately 5% higher power than other crystalline modules - providing a higher rebate in some states (per PTC ratings*)

• More power, less installation space required

That's why SunWize GTS Grid Tie Systems rely on Sanyo modules. Prepackaged systems available from 1400 to 3000 watts. Visit our web site, www.sunwize.com or call 800-817-6527 for more information.

*PTC stands for PVUSA Test Conditions. PTC watt rating is based on 1000W/m2 irradiance, 20° ambient temperature and 1 m/s wind speed.

MITSUI COMTEK CORP. SUtlWW/ZG

The Advanced Technology Subsidiary of Mitsui & Co., TECHNOLOGIES

Most solar heating collectors are used for domestic water and home heating. These jobs require that the collectors operate at temperatures above what is needed for domestic hot water (100 to 140°F; 38-60°C) and human comfort in the winter (60 to 70°F; 16-21°C). This project is a bit different. The Oneida Nation just needed to keep their greenhouse above freezing in the cold Wisconsin winters, a perfect job for solar heating, and much more efficient than the traditional uses of solar thermal collectors.

A 1,200 square foot greenhouse is kept warm in winter by a 306 square foot solar collector and radiant floor system.

The Oneida Nation is a sovereign nation with a long and proud history. Their efforts toward economic self-sufficiency have resulted in a variety of enterprises. The Tsyunhehkwa Center produces organic foods and other products on an 83 acre site in northeastern Wisconsin. Just outside of Green Bay, the center has a 1,200 square foot (119 m2) greenhouse that they use for giving their plants a head start in the late winter. The greenhouse is heated with a radiant floor heating system. Tubing in the concrete slab is heated with water circulating through a 37,000 BTU, 50 gallon (190 l) water heater.

The only fuel that was readily available to the greenhouse was propane. Even with an efficient radiant floor system (covered in depth in HP49 and HP79), the heating costs to keep the greenhouse from freezing were substantial. The Oneida Nation has a strong belief in keeping the earth's environment healthy for future generations, and is a big supporter of renewable energy.

Richard Lane and the Solar Mining Company (SMC) have worked with the Oneidas before on many solar heating projects. When they needed to find a better way to heat the greenhouse, Richard was the natural person to call. He formerly ran the Packerland solar heating system in Green

Bay. It consisted of 5,000, 4 by 8 foot (1.2 x 2.4 m) collectors, the largest system in the world. When the Oneidas described the greenhouse situation, Rich knew it was a great candidate for a solar heating system. Keeping a building from freezing is a piece of cake for a solar heating system— even in Wisconsin.

Starting plants early extends Wisconsin's growing season.

Starting plants early extends Wisconsin's growing season.

solar hydronic greenhouse

Maxi-Collectors

In Wisconsin, solar hot water systems are almost all closed loop antifreeze systems. The winter weather won't tolerate anything else for failsafe freeze protection. Greenhouses tend to heat themselves in the daytime, but they are subject to tremendous heat loss through the transparent glazing (glass or plastic) when the sun isn't shining. The collector size that would fit the Oneida's budget and put a serious dent in the heating bill was about 300 square feet (28 m2) of surface area—the equivalent of about ten, 4 by 8 foot collectors.

The winter weather in Wisconsin can play havoc with scheduling outside work, which is best kept to a minimum. Since this was a mid-winter project, the best way to proceed was to build a custom maxi-collector of the size needed, inside the SMC shop in nearby De Pere. A maxi-collector is a large solar heating collector that combines the components for multiple smaller collectors into a single enclosure. For this project, custom absorber plates were plumbed inside the insulated enclosure that SMC built. The collector was built to the maximum width of about 40 lineal feet (12 m)—any

The 8 by 40 foot maxi-collector is all one unit, custom built for the greenhouse.

larger would place undue strain on the collector header piping because of the expansion and contraction of the copper tubing.

In addition to helping with the outside work schedule, the cost was less with a custom-built maxi-collector. Historically, solar heating collectors have been either a modular installation of standard factory sizes or completely custom built on the job site. The maxi-collector is kind of in between these two design ideas, taking advantage of the

Solar Collector Efficiency

The efficiency of any solar heating collector is dictated by two significant factors, assuming the equipment is built to industry standards. The amount of sunshine available is of major importance. The other factor is the difference between the outside temperature and the operational temperature of the collectors.

The lower the operational temperature, the better the efficiency. As any solar heating collector gets hotter than the surrounding air (ambient outdoor temperature), it starts losing heat to that colder air. As this temperature difference gets greater, the efficiency suffers. The drop in production of heat can be significant when the weather is cold and you need to heat water to 140°F (60°C). A solar heating collector shows dramatically better performance when the job is simply keeping a greenhouse at about 40°F (4°C).

The graph may assist you in understanding this concept of the efficiency of a typical solar collector at different operational temperatures. Flat plate collectors are capable of making steam (212°F; 100°C at sea level), but they won't make much—they're too inefficient at elevated temperatures. The colder it is outside and the hotter the collectors need to be, the less they produce.

The heating industry uses the Greek letter delta (A) to signify difference, and temperature difference is often referred to as delta T (AT). As the AT increases, the collector efficiency decreases. Because of the low operational temperature required in the greenhouse, this particular system will produce more than a fifty percent increase in heat when compared to more typical, higher temperature, domestic water heating systems.

Collector Efficiency per Temperature Differential

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