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
most common method of producing water at safe temperatures for residential
- 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
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
- Automatic, Reliable
- Low Noise, No Moving
- Low Operating Cost
If You Can Say “YES” To
One Of The Following, A Solar Thermal System May Be a Good Choice For
- Interested in a Healthy
- Want to Become More
- Interested in Reducing
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 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
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
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
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
Plumbing codes have been developed to ensure safety in hot water delivery
systems, largely because of the high temperatures and pressures that may
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
- 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
- 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.
- 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
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