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Photovoltaic Types
- Single-Crystal Cells are
usually the most efficient. This is because the more perfect
a crystal the PV cell is, the easier it is for electricity
to move through
the material. However, the more perfect a crystal, the more
expensive it
is to manufacture. Single-crystal silicon cells can be easily
identified by their distinctive round or psuedo-square appearance.
- Multi-Crystalline Cells are
similar to ones made from Single-Crystal.
- Thin-Film Modules are
made by spraying non-crystalline silicon material directly onto the protective
glass. There are no individual cells. Commonly used for “Solar Shingles,” thin-film
is less expensive and weighs less, but is also currently less efficient.
- Fabric & Dye-Based photovoltaic
systems are currently under development on a microelectronic scale.
PV Applications
-
A
Grid Interactive Power System (also called Grid-Tie,
Grid-Connected) uses electronic equipment to directly connect the
PV array to the utility
service hook-up in your house. This type of system functions only when
power is also available from the utility and from the sun. Direct-tie
systems are used to offset the energy use of a building, helping
reduce pollution and dependence on fossil fuels.
- An Uninterruptible Power System is
a special type of grid-interactive system with batteries. A UPS can function
as a stand-alone system, providing power to critical loads if the utility
power fails. A UPS has all the benefits of a Grid Interactive system,
plus the added benefit of increasing power reliability at a building.
Advantages of Photovoltaic
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 PV System May Be a Good Choice For You
ü Concerned
About Power System Reliability
ü Interested
in a Healthy Environment
ü Want
to Become More Energy Independent
Will PV 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 PV array and the prevailing
weather conditions. The angle of the sun’s rays hitting the array
depends on the latitude where the array is located, the tilt of
the array, the direction the array is 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, PV array systems in New England
can access on average a maximum of between 5 and 6 peak sun hours
a day. These numbers vary monthly. In the winter, less peak sun
hours are available, but this is slightly offset by the fact that
photovoltaics are more efficient in cold weather, and will produce
more power. Since these are averages, the actual amount of
solar energy available at a particular site, or for a specific
day,
may be significantly different.
Electricity
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 PV array won’t be cost
effective for you. The value of the electricity it produces is
also important. Areas with high electric rates are often good
candidates for PV.
What Do I Need to Use FREE Energy From the Sun?
Array
Mounting Structure
The
best angle for an array to be at is perpendicular to the sun’s rays. A
tracking system will automatically orient the array properly, allowing
the maximum amount of sunlight to be harvested. If the array is to be
permanently fixed in place, mounting the array at an angle equal to the
location latitude will keep the array perpendicular as much as possible,
and will produce the best results. Most roof pitches in New England
are 10/10 to 10/12, nearly optimal for a PV array.
Site
Selection
The
PV array 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), but preventing the
array from being shaded provides more power and prolongs the array life
by keeping an even temperature over the array. The best direction for
an array to face is due South.
Building
Integrated PV
A
building integrated PV array is part of the necessary structure of
the building walls, windows, or roof. The array provides dual
functions of
power generation and protection from the elements. These types of
arrays may be very cost-effective, since the array is serving a dual-purpose,
and a budget is already allocated for building material. Electricity
production needs only to offset any higher incremental costs.
Permits
A
building permit from town authorities may be required by the
town to allow legal construction of a PV array on your property. Depending
on zoning requirements, a public zoning hearing may also be necessary
to obtain a variance, for example if the array is to be roof-mounted
in a
historical district. An electrical permit is required and
can be obtained by your electrician.
System
Protection - The National Electric Code
The
National Electric Code (NEC) was established in 1987 to ensure safety
in electrical systems. When a system is installed, NEC requirements must
be carefully followed, or it will fail inspection. Additionally, many
states require all electrical equipment to be installed by a licensed electrician.
Utility
Interconnection & Net Metering
As a result of
the Public Utility Regulatory Policy Act (PURPA) of 1978, all utilities are
required to purchase power from
a customer who produces an excess of energy, as long as that energy
that meets certain quality specifications. In many states, including all
of New England, the active energy buy back policy is termed “net metering.” Under
this policy, the utility rates the energy the customer produces at a
1:1 ratio to the power consumed. If, at the end of the month, the consumer
has produced more power than consumed, the excess kWh’s are labeled “net
excess generation.” Net excess generation is treated differently by
state. In some states, the excess kWh’s are rolled forward as a credit
to the next month’s bill. For a customer, it is the best metering policy
in the country. In other states, net excess generation is valued at “avoided
cost,” which is what your energy would have cost the utility to
produce (or buy elsewhere in deregulated states).
An
agreement with your utility is needed to legally sell power on the grid
and receive your full, entitled benefits. In deregulated states, separate
agreements are needed with both the electric distribution company and
your power supplier.
Protecting Your Investment
in a Power System
Insurance
A
renewable energy system is a valuable investment in the environment,
in your property, and in your energy needs. PV modules 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, and to meet any utility company requirements for liability
insurance to protect utility personnel. Most homeowner’s policies are
already adequate.
Maintenance
-
Checking
the output of your system periodically will help you verify if
your system is operating properly.
-
Regular
inspection of the outdoor equipment should be done annually and
after unusually severe weather, to ensure the mounting system
is secure and the PV array is unobstructed and undamaged.
-
In
areas of high air pollution, the array may occasionally need
to be cleaned with soft cloth and mild glass cleaner.
-
If
your system has batteries, inspection of the batteries for voltage
differences and terminal corrosion should be done annually. The
batteries are expected to ast 10 years before replacement is
advised.
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 options 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
-
-
-
Hardware
and labor warranties.
-
Handling
of utility interconnection.
-
-
Often
the most effective way of reducing environmental impact and utility
bills is to decrease electricity consumption. By using the most efficient appliances
available, such as those with the Energy Star rating, you will make an
impact! Energy efficient appliances can never produce energy, or provide
power in emergencies, so you still may choose to invest in a PV system. However,
you should be aware that a PV system functions at its best with energy
efficient appliances.
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
.
The
Federal Government has made a commitment to promote solar energy to
enhance the market competitiveness of the United States, to increase the
nation’s
energy security, and to mitigate pollution. In 1997, the Million Solar
Roofs Initiative began. The goal of the program is to install one
million solar energy systems on buildings across the United
States by 2010. The MSR Initiative operates through State and Local Partnerships
coordinated by the US Department of Energy’s Regional Offices. Each Partnership
commits to install at least 500 PV systems, and acts to help identify and
remove barriers to installing these PV systems. Some activities are educating
code officials, identifying financing opportunities, and promoting net
metering. For more information, and to find out about programs in
your area, please visit the MSR Initiative web site at www.MillionSolarRoofs.org.
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