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Solar Collector Types

Solar collectors convert light energy to thermal energy; the heat transfer fluid then removes the thermal energy and transports it. The three most common collector types are flat plate, evacuated tube, and concentrating.

  • Flat plate collectors are constructed from parallel tubes that run through black absorber plates. A liquid, either water or another heat transfer fluid, is heated as it is pumped through the tubes in the absorbers. These are the most common method of producing water at safe temperatures for residential uses.
  • Evacuated tube collectors are a special type of flat plate collector where the tubes are in a vacuum. This greatly reduces heat losses, so they can operate more efficiently at high temperatures.
  • Concentrating collectors use a curved mirror shaped like a parabolic trough to concentrate reflected light on a fluid-filled tube. The heat transfer fluid can be water or oil, depending upon the design temperatures of the system.

Solar Thermal Applications

1. A Domestic Hot Water system transfers energy captured by the collectors to a solar storage tank. In climates with the potential for freezing temperatures, a dedicated heat transfer fluid containing propylene glycol, (a non-toxic antifreeze), is used to perform the transfer. Such a system is known as a closed loop system because the liquid flowing through the collectors is continuously reused and isolated from the fresh domestic water supply. The solar storage tank is an insulated water tank that serves as a preheat tank to any conventional (or non-conventional) water heating system. In this way, heat energy from the sun can be used to offset the energy required to heat water at any time, mitigating pollution, reducing dependence on fossil fuels, and saving on energy costs.

2. A Space Heating system operates in the same way as a solar domestic water heating system, and can be interfaced with a conventional heating system.

3. A Pool Heating system circulates the chlorinated pool water directly through the solar collectors, when sufficient solar energy is available, using the existing pool filter and pump. These systems are used to extend the swimming season, and are shut down in the winter. A higher quality swimming experience can be had without an adverse environmental and economic impact. Pool heating applications usually use plastic flat plate collectors for cost-effectiveness, and because less of a temperature rise is required.

Advantages of Solar Thermal Systems

  • Automatic, Reliable Operation
  • Low Noise, No Moving Parts
  • Low Operating Cost
  • Non-Polluting
  • Modular, Portable
  • Non-Flammable

If You Can Say “YES” To One Of The Following, A Solar Thermal System May Be a Good Choice For You

  • Interested in a Healthy Environment
  • Want to Become More Energy Independent
  • Interested in Reducing Energy Costs

Will Solar Thermal be Effective Where I Live?

Solar energy is one of the most reliable forms of energy in the world. In fact, most energy ultimately has come from the sun. Even under adverse weather conditions, a guaranteed minimum amount of energy will be available daily from the sun.

The amount of power available from the sun at any one moment depends on the angle of the sun’s rays hitting the collectors and the prevailing weather conditions. The angle of the sun’s rays hitting the collector array depends on the latitude where the array is located, the tilt of the array, the direction the collectors are facing, the hour of the day, and the season of the year. Prevailing weather includes factors like cloud cover, air clarity, temperature, and wind chill. Solar insolation maps take into account all of these factors typical for a geographic region. As shown on the Department of Energy’s (DOE) solar resource map, collector systems in New England can access on average a maximum of between 4 and 5 peak sun hours a day. These numbers vary monthly. Since these are averages, the actual amount of solar energy available at a particular site, or for a specific day, may be significantly different.


Energy Prices

Even if your site does not seem to have as much sun as other areas of the world, this does not necessarily mean a solar thermal system won’t be cost effective for you. Areas with high electric or fuel rates are often good candidates.

What Do I Need to Use FREE Energy From the Sun?

1. Collector Mounting
The best angle for a collector to be at is perpendicular to the sun’s rays. Mounting the array at an angle equal to the location latitude will keep the collector perpendicular to the sun as much as possible throughout the year, and will produce the best results. Most roof pitches in New England are 10/10 to 10/12, nearly optimal.

2. Site Selection
The solar collectors should be sited in an area free of shading for as much of the day as possible. Some shading is permissible during the early morning and late evening hours (before 9 AM and after 3 PM), when the direct radiation from the sun is minimal anyway. The best direction for an array to face is due South.

3. Permits
Before installing a solar thermal, or any renewable energy, system on your property it is wise to check with the local town authorities to determine if a building permit, electrical permit, or plumbing permit is required; what portion of the installation must be done by licensed electricians, plumbers, etc.; and what safety inspections of the system will be required. A public hearing may be necessary to obtain any variances if the system is installed in a historical area, etc. At a minimum, most towns require that a licensed plumber implement the domestic water piping.

4. System Protection – Plumbing Codes
Plumbing codes have been developed to ensure safety in hot water delivery systems, largely because of the high temperatures and pressures that may be present. When a system is installed, these requirements must be carefully followed. Not all local code officials, insurance providers, and lenders are familiar with solar thermal systems, so it could be important to contact and educate these parties when you plan to install a system.

Protecting Your Investment

A renewable energy system is a valuable investment in the environment, your property, and in your energy needs. Solar collectors are certified to withstand severe environmental conditions. However, it is recommended that you verify that your existing homeowner’s policy is sufficient to cover the value of the system.


  • Tracking your energy bills and checking the operating temperatures and pressures of your system periodically will help you verify if your system is working properly.
  • In a closed loop system, the heat exchange fluid may need to be replaced approximately every two to five years, because like any antifreeze, it will break down and lose its effectiveness over time if exposed to temperature extremes.
  • Like conventional water tanks, solar storage tanks should be periodically drained and flushed of sediment, which could restrict fluid flow and foul pumps.
  • As in a conventional water system, the circulation pump strainer and/or filter should be periodically cleaned and replaced as necessary.
  • Regular inspection of the outdoor equipment should be done annually and after unusually severe weather, to ensure the mounting system is secure and the collectors are unobstructed and undamaged.
  • In areas of high air pollution, the glazing may occasionally need to be cleaned with soft cloth and mild glass cleaner.

KW Management Can Help You Reach Your Energy Goals

KW Management, Inc’ seeks to make a positive impact on quality of life and the environment by promoting clean, efficient, and renewable energy technologies. We work with world-class manufacturers to provide excellent equipment, analysis, and project management services in the most cost-effective manner, and to provide the information needed for customers to make choices about the energy oprions that best meet their individual goals.

With our packaged systems, all of the component selection, sizing, and safety compliance has already been done for you.

We also provide these essential time and money-saving services

  • Site assessment.
  • Project management.
  • Hardware and labor warranties.
  • Maintenance contracts.
  • Custom project design.

An Important Note…
Often the most effective way of mitigating pollution, reducing dependence on fossil fuels, and minimizing energy costs, is to decrease hot water consumption. Insulating tanks and hot water lines; using low flow appliance heads; and taking advantage of technology such as on-demand heaters, waste-water heat recovery products, and intelligent controls, are all viable choices we can help you with!

So we can offer you the best service, please take a moment to fill out the enclosed questionnaire and return it. We will review the information you provide and contact you to answer any questions you may have or schedule a site visit . Our prepackaged systems will fit on most standard buildings, but a site visit will best determine the ability of your site to harness energy from the sun.

Many states require that all solar thermal systems installed within their borders comply with requirements as set forth by the Solar Rating & Certification Corporation (SRCC). Solar collectors are tested to meet these requirements by the FSEC in the United States, and by the National Solar Test Facility in Canada.



KW Management, Inc.
55 Lake Street | Nashua, NH 03060
Phone: 603-598-0181 | Fax: 603-598-5188

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