GREEN VILLAGE CRIER

GREEN VILLAGE CRIER

ARTICLE IV

by Thomas Maroney PCE

Ondrick Engineering Group

Quincy, Massachusetts

EVACUATED SOLAR TUBE

COLLECTORS

VS.

FLAT PLATE SOLAR COLLECTORS

Solar collectors come in different sizes, types and brands. Making sense out of what is best for your particular use can sometimes be a little confusing. Hopefully, this brief overview will help you make an informed choice. And, as always, you can call us at anytime to discuss your application and use and a GUARDIAN SOLAR SW specialist will gladly assist you simple call us at 941-639-5250 or email Tom Maroney at: norwell69@msn.com he will be sure to reply.

FLAT PLATE SOLAR COLLECTORS

The first type of collector is called a Flat-Plate-Collector and these are the most commonly used collectors for solar hot water systems (direct or indirect feed) today.

The direct feed system is popular in the southern most states because they do not need to protect the units from the winter's freezing conditions. The collectors heated water is circulated directly into the home's hot water tank. The direct feed is the
most efficient heating source for a number of obvious reasons.

The indirect feed system is used mainly in the northern regions where freezing is a concern. The closed loop design uses anti-freeze and a heat exchanger in the hot water tank to prevent any damage that may occur during the coldest of temperatures.


THE UNIT DESIGN


This collectors heating concept is based on a "green house effect" and consist of a closed insulated metal box with a glass or plastic/lexan covering (this is what is referred to as the glazing) or a dark absorbing plate usually made from copper or aluminum and rigid foam insulation. (see illustration on the right) This absorber plates transfer the radiated heat from the sun to a channel of 1/2 copper tubes that distributes the heated water to temperatures around 160-180 degrees F and into the home's hot water tank. The flat plate collector are very popular because of their cost and effectiveness. Mounting can be accomplished on the homes asphalt, steel, rubber and tile roofs or on the ground on stand. They come in a variety of sizes and are used for residential and commercial hot water application with great success!

System Advantages: Readily available, wide selection of sizes and installation methods and materials. Very cost effective and gets the job done.

System Disadvantages: The panels are large and bulky and in some cases heavier than others. Some cases utilize plastic and aluminum back panels to lighten the load. AET makes two grades of cases for different applications while Solene makes a plastic back panel that is noticeably lighter and produces the same BTU's.

Future Predictions: These panels will see some newer technology, designs and materials that will increase their BTU out put. Because of the ever increasing cost of copper costs will continue to climb.

Evacuated Tube Solar Collectors


Evacuated Tube Collectors come in different types as well. Evacuated Tubes are tubes that are manufactured with a vacuum seal in-between the glass layers, preventing heat loss from convection and radiation and maximizing efficiency of energy absorption. They can achieve very high temperatures but are also more expensive to purchase than the Flat Plat Collectors. This is an example of Direct-Flow-Evacuated-Tube collector they also come in various sizes and combinations of tubes. The most commonly used Evacuated Tube collector is the heat pipe and manifold system. In this type of design, heat is transferred from either a flat or curved copper or aluminum fin attached to a heat pipe located inside the evacuated glass vacuum tubing. The water is saturated in the sun's radiation and convection hot water at upwards of 185 degrees is funneled through to the hot water tanks heat exchanger. Because the greater efficiency and higher temperatures this is a very effective way to heat your water.


THE UNIT DESIGN:

The evacuation collection tubes are made of glass and have all the air evacuated from them and are called absorbers. Inside the tubes are copper pipes filled with the domestic water. An insulated header houses heat exchangers that transfers the suns heat to your tank. Some absorbers are being designed to have multiple channels inside the 1/2 copper pipe to aid in generating more heat to the water flowing through.

The Advantages: The evacuated tube system affords more of the sun's radiation exposure by it's round design. The high temperatures that it generates 180- 210 degrees makes it suitable for more applications. The higher productivity lessens the need for more panels. It is suited for both residential and commercial applications.

The Disadvantages: The cost is higher. Some installer's claim that the evacuated tube collector is too hot for a direct feed into a standard solar hot water tank and sharply reduces the life of the tank. Some homeowners think the collectors look ugly on their roofs. The glass tubes are vulnerable because if one breaks the whole unit is down. Also the vacuum seal has a potential for leaking when exposed to years of expanding and contracting.

Future Predictions: The product's prices will fall as this system is very popular in Europe right now and will become more available to the American market. Because of the tremendous heat advantages the Tube system will find it's way into residential, commercial and pool heating systems. In fact as I write this a Hybrid Solar Pool Heat Pump unit is being tested right here in Florida. This Heat pump will be solar assisted and qualify for federal incentives.

Thats the way to go... all we need is a little "American ingenuity"! Any thoughts or comments please pass them along to our website at: http://www.guardiansolarsw.com/ that's all for now solarheads.