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General Information of Solar Panel

 

Introduction

Solar swimming pool heating is the most const-effective application of solar energy. Unglazed collectors (solar panel), which are the simplest and least expensive of all collectors, are used almost universally for heating pools and spas.

General Classification and Application of Solar Collectors

Solar collectors (panels) can be classified into two major categories based on the working fluid used to cool them. These two are “liquid” and “air”. Each of these two categories can then be sub-classified according to average temperature range over which they are intended to be used effectively. These classifications are: “low temperature”, “medium temperature” and “high temperature”, with some overlap among the classifications depending on the construction of the individual collector model.

Medium Temperature Collectors

Medium temperature collectors typically are flat-plate collectors, enclosed in an insulated case, with one or two glazing. The intended temperature range of operation is from about 15 to 200 degrees F above ambient temperature. For the lower end of this range, single-glazed collectors with non-selective absorber plates are most cost effective. In the middle and high end of the range, selective plates with one or two glazing become more cost effective.

Unglazed Flat Plate Liquid Collectors

Unglazed liquid flat collectors are used almost exclusively for swimming pool heating. The only major components of a liquid flat plate unglazed collector are the absorber plate and the water passages. Since no insulation or glazing is needed there is no need for an enclosure.

Unglazed metal collectors for swimming pools almost always have copper in contact with the water flowing through them. Many of them use aluminum for the absorber plate or fins, because of its lower cost relative to copper or other effective materials. Some are all copper, with very thins absorber plate or fins to reduce cost, but at the sacrifice of some efficiency. Water tubes may be soldered, brazed, snapped into grooves or inserted into spring-loaded extrusions.

Selective coatings are not used on properly designed unglazed solar collectors, because it serves no purpose. The temperatures of operation are low enough to make radiation losses negligible.

Desirable Design Features of Unglazed Collectors

Unglazed solar collectors have potentially high efficiency by comparison to any other type when each is used in its intended operating temperature range. The elimination of glazing and case reduces the losses of incident energy otherwise caused by absorption in and reflection by the glazing, and partial shading by the case. To ensure the availability of this high efficiency, the collector must have a high “fin efficiency”. The factors that make fin efficiency are the following:

A. High Surface Adsoptivity. This is available through use if flat black paint with absorptivity of .95 or better, which can be maintained if a high quality weather resistant baked paint is used over the appropriate baked primer. Less expensive panels frequently omit both primer and baking, soon resulting in loss of absorptivity, and perhaps early onset of corrosion.

B. Optimum tube spacing: Wide spacing of tubes reduces collector cost, while close spacing increases cost, but improves efficiency. Fin efficiency drops rather fast as the tube spacing is increased above about four inches, depending on the thinckness and thermal conductivity of the fin metal, and effectiveness of thermal bond. The highest quality, most cost effective collectors have sufficient spacing typically no more that 4 inches, with large area tight bonding to the water tubes.

Another highly desirable design and construction feature is secure attachment of headers to water tubes. High quality collectors have the tubes brazed or welded to the headers and supported mechanically by insertion into sockets extracted directly from the header metal by a “t-drill”. In addition to high level insurance against leaks, and breakage at joints and from wind vibration, this method of attachment provides smooth easily balanced flow and eliminated the possibility of eddy corrosion.

The high flow rates demanded for swimming pool heating make ample sizing of headers important. Properly sized headers will minimize pump energy demand, and will reduce installation plumbing costs. The best quality collectors typically have 1 1/2 inch nominal headers, permitting up to 400 square ft. of collectors to be connected header-to-header without parallel connections.

Installation Site Conditions Necessary

The collector area required will depend on the surface area of swimming pool, the water temperature we wish to maintain, the amount of pool shading and the direction the solar collectors face. Typically the area that will be efficient is 60% the area of our pool surface (length*width*.6). For less favorable solar collector orientation the collector are required may be as large as the pool surface area.

Solar Pump

Solar Controls


Solar Swimming Pool Heating Diagram

Solar Panel Installation

Step 1

Step 2

Align mounts on top of rafters, then pre-drill with a pilot bit to avoid splitting the rafters. The rafters can be found with a stud finder, typically they are either 16’’ or 24’’ apart, allowing for mounts to be placed every 48’’

Step 3

Secure the mounts to the roof with stainless steel lag bolts.

Step 4

Thread the post into the base.

Step 5

Continue installing all of the mounts required.

Step 6

Place 3/4’’ metal roof flashing over the mounts.

Step 7

After the new roof has been applied, secure metal channel on top of the mounts.

Assemble aluminum solar panel racks and secure the racks to the metal channel.

Step 8

Upon completion of the racking system, secure the solar panels.

Important Characteristics of Metal Collectors
A. Rigid construction
B. Can be rack mounted
C. No spaces and gaps between panels
D. Fire resistant
E. More expensive to manufacture
F. Heavier than plastic panels
G. Higher shipping costs
H. Need to be drained if freezing is possible

Go Solar Company
12439 Magnolia Blvd. #132
North Hollywood, CA 91607
818-566-6870
www.solarexpert.com

 
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