Is Solar Heating For You? Analysis Method
"...a solar heating system that is uniquely efficient."
"IS SOLAR HEATING FOR YOU?, PART 1" |
"PART 2" | "NARRATIVE DISCUSSION"
This analysis can be used to estimate solar performance on a monthly and annual basis.
Please understand that the analysis is based upon average solar energy values and that actual performance may be
more or less. Feel free to print out the worksheets that follow.
STEP ONE: First find out what the solar resource
is for your area (S) on a monthly basis. Go to the INFO LIBRARY
and you will find a link to a website that will provide this information for various collector
tilt angles. You will find out how much solar energy shines upon a square foot (or square meter) of surface
area on a monthly basis.
STEP TWO: Then, figure how much of this solar
resource will actually be harvested by your solar energy system (S'). This
is function of collector efficiency and the system operating temperature.
Higher temperatures lower efficiency. Multiply (S) by the known energy
factor of the particular system (consult the manufacturer or designer),
to calculate (S').
STEP THREE: Calculate how much heat you need
(L, for Load) on a monthly basis. Use a standard heat loss analysis method
such as Manual J. Contact Radiantec for
a simplified procedure. You can also consult a plumbing and heating contractor
or perhaps your local utility.
STEP FOUR: Calculate S'/L. This value is the
amount of solar energy harvested in relation to the amount that is needed.
A value of 1.0 or higher means that the system will harvest as much energy
as is needed.
STEP FIVE: Factor usefulness. The solar
heating system (or the house itself) must be able to store solar energy
and release it when needed. If there is not enough storage, the harvested
solar energy will not all be useful. Some solar energy will be wasted (or
diverted to another use) because the storage is full. Also, there may not
be enough energy storage to go through unseasonable weather. The chart
below is from a solar heating system that is uniquely efficient. There
is a large energy storage system and an energy efficient house above.
(Solar Option One) http://www.radiantsolar.com/optionI.php
It is seen that most of the harvested solar energy is useful on a "one to
one" basis until a high solar heating fraction is reached. At that point,
more solar energy is needed to meet the load because of diminishing returns.
Use a chart that is specific to the solar energy system that you are thinking
about using. Bear in mind that the chart above is from a highly efficient
system, (Solar Option One) http://www.radiantsolar.com/optionI.php, and that
less storage will result in lower performance. The chart will tell you what the actual
solar heating percentage is predicted to be.
Worksheet C will help you calculate other factors such as cost benefit. The DOE Report
in INFO LIBRARY presents two completed
calculations. There is one for a house in Boston, MA, and another for one in Denver, CO.