Green Collar Careers - Solar
A solar collector is a device that collects the energy from the sun
and transfers that energy to a different media in the form of heat.
Most of the heat comes from the longer wavelength light in the
Infra-Red (IR) range. Infra Red is the reason you feel the
warmth of the sun through a window.
A system can either be passive, meaning it doesn't move, or active
such as a solar concentrator that tracks the sun. Not all
experts may agree on the definitions of active and passive systems as
there are so many different designs that may use various mechanisms to
move fluid exchange mediums or move the collector to track the sun.
Typical Non-Tracking Systems
Glazed flat-plate collectors are insulated, weatherproofed boxes that
contain a dark absorber plate under one or more glass or plastic
(polymer) covers. Unglazed flat-plate collectors—typically used for
solar pool heating—have a dark absorber plate, made of metal or
polymer, without a cover or enclosure. While these are the least
expensive systems, they are also the the least effective at capturing
heat. Typically the peak water temperature will only rise about
30-50° warmer then the ambient air with a ceiling of about 140° F.
Integral collector-storage systems
Also known as ICS or batch systems, they feature one or more black
tanks or tubes in an insulated, glazed box. Cold water first passes
through the solar collector, which preheats the water. The water then
continues on to the conventional backup water heater, providing a
reliable source of hot water. If water is the fluid exchange medium
they should be installed only in mild-freeze climates because the
outdoor pipes could freeze in severe, cold weather. Typically
the peak water temperature will only rise about 60-70° warmer then the
ambient air with a ceiling of about 150° F.
Simple evacuated-tube solar collectors
They feature parallel rows of transparent glass tubes. Each tube
contains a glass outer tube and metal absorber tube attached to a fin.
The fin's coating absorbs solar energy but inhibits radiative heat
loss. These collectors are used more frequently for U.S. commercial
applications. While being the most expensive, the lack of
thermal convection losses also make them the most efficient.
Typically the peak water temperature will 180° F. and ambient air
temperature has very little effect if the manifolds are properly
Water is not the only fluid
exchange medium used, its just the one most people think of.
Some evacuated tube systems may use air, helium, or some other gas and
due to the lower mass, the temperatures can easily reach 400° F.
Non-evacuated systems lose too much heat to convection to take
advantage of this characteristic.
evacuated-tube solar collectors
Similar to the evacuated-tube solar collectors the difference is they
work on the principal of boiling the primary fluid medium in the
absorber tube causing it to rise to the top, and then exchanging the
heat in the boiled liquid with a second medium. After the
primary medium exchanges the heat it liquefies and falls back to the
bottom of the absorber tube to repeat the process. The primary
medium is sealed in the absorber tube and since the heat exchange
takes place only at the highest point it needs only one manifold.
Solar Concentrator Tracking Systems
Solar concentrators focus a large
area of sunlight on a small target concentrating a large area of
energy on a small collector. Solar concentrators offer some
advantages in temperatures and performance although the cost is higher
due to the required tracking system. Two types of solar
concentrators are available today:
Every satellite dish uses a parabolic shape to reflect concentrated
radio waves on a receiver and given a highly reflective surface, they
could also reflect sunlight. There are several designs of
systems ranging from perfectly curved mirrors to an arrangement of
tiny flat mirrors mounted to a curved surface of an engineered
parabolic shape. These mirrors can concentrate an incredible
amount of heat on a small area. Recalling that a square foot of
sunlight in Kansas City will provide about 205 BTU's/hour, a parabolic
mirror of 8 feet in diameter will produce over 10,000 BTU's in an
hour. Focus that energy on a sphere large enough to hold 1
gallon of water and it will boil a gallon of tap water in 5 minutes.
Where a parabolic mirror is shaped to focus energy onto a sphere, a
parabolic trough works much better with tubes and are much easier to
manufacture. Coupled with an evacuated tube collector and
Stirling engine the parabolic has a very bright future in solar
Use the Search Tool below to research existing systems that may
fit your local market needs best.