Types of Solar Thermal
There are a number of different solar thermal designs, but all
are based on the same simple principle as the harden hose. Each
has its pros and cons, and each is suitable for a specific
application. Consulting with Adros Energy will ensure you get a
system designed to meet your needs.
The terms passive and active in solar thermal systems refer to
whether the systems rely on pumps or only thermodynamics to
circulate water through the systems. The simplest systems are
passive solar water heaters, also called batch or breadbox
collectors. They are the most common in regions that do not
experience extensive periods of below freezing temperatures. The
water in these systems circulates without the aid of pumps or
controls. Active solar water heaters use pumps to circulate
water or an antifreeze solution through heat-absorbing solar
thermal collectors.
Direct vs.
Indirect
An important distinction among solar thermal systems is whether
they are of direct or indirect design. In a direct system, the
water used by building occupants to wash their clothes or bathe
is the same water that is pumped through the solar collector. In
an indirect system, an antifreeze solution is pumped through the
solar heat collector. This warm solution is then used to heat
the water used by building occupants. In this case, water is
indirectly heated.
Indirect Systems
In an indirect system, also known as “closed loop,” a simple
pump moves the antifreeze solution through a loop into the solar
collector, through the collector’s pipes, and out of the solar
collector. This sun-warmed solution flows into a heat-transfer
unit where it warms the cool water into a conventional hot water
tank. This solution never mixes with the building’s water
supply. This is the type of system used in cold climates where
freezing is possible. The antifreeze solution is food based and
does no harm to people, animals or the environment.
Direct Systems
A direct system, also known as “open loop,” is a little simpler.
There is no antifreeze solution and the water heated by the sun
is the same water used in the building. The main problem with
this system is the possible freezing of the water and damage to
the system. You will not see these system used in the Northeast
of the US.
Drain Back Systems
State of the art, fail safe and freeze protection is the best
choice for the Northeast. Collector water is separated from
potable water and the collector water “drains back” into a
special tank to prevent freezing and overheating. The drain back
automatically occurs when potable water reaches proper
temperature or if no sunlight is available.
Solar Thermal Collectors
Solar thermal systems also differ by the type of collector used
to gather and store the sun’s energy. Flat plate collectors are
the simplest and most common type. Copper pipes wind back and
forth through the flat plate collector, which is painted black
to absorb heat and covered with glass, or glazing, to prevent
heat from escaping. Often the pipes are painted black and bonded
to the material of the collector to maximize heat absorption.
Figure 1:
Evacuated Tube and Flat Panel Solar Thermal Collectors
Solar pool
heating systems use a similar design, but sometimes glazing is
removed to save money and prevent the pool water from becoming
super heated. Some non-glazed systems look like flat black mats.
Inside the mats is a network of headers through which the water
slowly passes.
More advanced systems like evacuated tube collectors and
parabolic mirror collectors can heat water or other fluids to
much higher temperatures appropriated for industrial needs.
Adros Energy is a leader in designing and installing solar
thermal systems in the Northeast area of the United States and
is ready to help you save money and the environment by producing
hot water from the power of the sun. Weather you are heating hot
water for domestic use or to heat a pool or other area, we are
ready to help you answer all the questions you may have.
Planning and Sizing a Solar PV System
The two most important factors in planning a solar electric
system are your daily power consumption, or loads and the amount
of sunlight that you have, or insolation,
Power Consumption: The Kilo-Watt-Hour
The easiest way to calculate your power consumption is to look
at your electric bills from the past year. This will tell you
how much you use in Kilowatt hours. Each Kilowatt hour (kwh) is
1,000 watts A kwh is the amount of electricity used in one hour.
WOW! That’s a lot! Watch your electric meter spin, it is showing
kwh usage. The faster it spins the more power you consume, and
pay for.
High power uses include stoves, refrigerators, electric water
heaters and well pumps. To get the most from your use solar
electricity you may need to make want to swap old high power
consuming appliances for energy star rated ones and make changes
in you the way you consume electricity.
Insolation
Insolation is sunlight intensity that is measured in equivalent
full sun hours. One hour of 100% sunshine on a solar panel or
array equals on full sun hour. Even though the sun is up for 12
hours a day, all of those hours are not considered full sun
hours. There are two reasons for this: the sun in the morning
and late afternoon is shining through more atmosphere than at
mid-day. Also in the early and late times of the day, the angle
of the sun is too sharp relative to the surface of you solar
panels. Panels are more able to use light that is closer to
perpendicular to their surface.
The most productive hours of sunshine for solar electricity are
from 9 am to 3 pm. In some parts of the US, these may be the
only hours of sunlight in the winter. So we use both the average
full sun hours and the winter full sun hours to help in
designing systems. In the North East area we get between 3.5 to
4 full sun hours a day on average. See the average sun chart.
Figure 2:
Insulation factors for the US
Energy Evaluation
By calling Adros Energy you can receive an evaluation of your
uses of electric and how a solar system may be designed to fit
your unique needs. We need to look at the orientation of the
roof to determine how well the system would work. We would also
evaluate if a ground mount option will work. We would use a
solar pathfinder to determine if any shading will exist
through-out the year. The solar pathfinder will not only give us
a snapshot of the shading now, but for the entire year.
Figure 3: Sun exposure with a solar pathfinder
