Photovoltaic Systems
What is "PV"?
PV is short
for Photovoltaic. One of the
primary methods of capturing the sun's energy is through the use of
photovoltaic cells or panels. Photovoltaic (PV) technology utilizes the
photoelectric effect and turns photons from the sun's light into
electricity. This was first described by the French physicist Edmund
Becquerel in 1839.
The
photoelectric effect occurs when Ultraviolet (UV) light, composed of
photons, strikes a negatively charged metal plate. This causes electrons
to be knocked loose from the negatively charged plate. These free
electrons are then attracted to the other plate by electrostatic forces.
When this happens, it results in electrical current. This electron flow
is in the form of direct current (DC). If the electrical energy is used
for an alternating current (AC) circuit, an inverter is used to convert
it from DC.
How do I determine what size of a solar powered system I need?
The primary
goal when installing a solar power system is to at least lower your
consumption where you are only charged at the lower tier rates. If you
want to eliminate your electric bill, if possible, gather your electric
bills for the past twelve months. At an average, a 1-KW solar system
will generate about 2,000 KW-hours in a year. Divide your total KW usage
over the last 12 months by 2,000. This should give you a good rule of
thumb number to go with. If your total electric usage is 10,000 for the
year, you would need a 5-KW system to eliminate a majority of your
electrical bill.
Will installing solar panels affect the value of my house?
According to
a study provided by ICF Consulting, solar can add $20 of home value for
every $1 of yearly energy cost savings. If you are seeing a savings of
$250 per month, that equates to a $3,000 annual savings. By using the
ICF formula, it should increase the value of your home by close to
$60,000. The size of your system will determine how much value you gain
by installing a solar system.
Will installing a solar power system increase my home insurance?
Unless you
do the installation yourself, all work should be done by a licensed
professional that meets all city, county, and state guidelines. The
equipment that is installed should also carry UL certifications. Make
sure this is the case before proceeding with any company or individual.
When installed properly, there should be no additional risk to your
home. Therefore your home insurance shouldn’t be impacted at all. If any
leaks occur or any other damage, the warranty you receive from the
installing company should cover those damages. Verify the warranty that
is offered with your installation.
How does weather affect my solar electric system?
All
professional solar electric systems are designed to withstand weather
conditions of all kinds. Modern solar panels hold up well against
lightning, extreme temperatures, and even wind storms typically up to 80
miles per hour. These conditions will however temporarily reduce the
system’s energy production. Although the solar panels are very strong
and durable, severe hail storms could cause some damage, as with any
structure. If you live in an area that has severe thunder storms, you
will want to make sure your insurance includes your solar system.
What's the effect of rain and fog on solar production?
In fog, or
cloudy weather, most systems will still produce up to 20% to 30% of a
normal amount. A steady rain will cut back considerably on production
but does have a side benefit of cleaning the panels.
Will snow covering the panels reduce electrical production?
Immediately
following a snowstorm when the panels are covered, the system production
will be minimal. Fortunately, solar systems are placed where sunshine is
the greatest. Therefore the snow will melt quicker and restore
production as it melts. Also with the tilted mounting of the panels and
the slick surface, the snow will also slide off fairly easily.
How does a solar electric system store electricity so I can use it after
the sun goes down?
The most
common solar energy system is what is known as a "Grid-Tie Only" system.
There are no batteries to store energy. Excess electricity production
goes back into the local utility grid. In the process, your meter spins
backwards. You will receive credit for any power that you "sell" to the
utility company. This is what happens with Net Metering. One drawback
with this system is if there is a black out, you will lose power even if
the sun is shining. The reason is, your inverters sync off of the AC
power coming into your home from the grid. With no power coming in, the
system has to shut down.
What maintenance is required on my PV panels?
Since there
are no movable parts on PV modules, there is virtually no maintenance
needed. The only real routine maintenance that is involved is keeping
the solar panels clean. In many areas, the normal rainfall will keep the
solar panels washed off. In areas where it doesn’t rain much and there
is a significant amount of dust, it will require you to hose off the
panels every 30 to 90 days. Solar production is reduced if dust or any
other debris builds up on the panels. Some have actually set up a
sprinkling system that washes the panels without having to get on the
roof to do so.
How long do PV modules last?
It is
estimated based on tests over a period of decades that single and
polycrystalline modules degrade at a fairly steady rate of 0.25%-0.5%
per year. Based on that information, PV modules should last a long, long
time. Most solar manufacturers offer a warranty of between 20 and 25
years, but the panels are expected to last at least twice that long. The
warranty states that the product will still produce 80% of its original
power output after the 20th year. With an average of six to
eight hours of active sunlight per day should provide up to 40 or 50
years of normal production.
Is it possible to install a grid-tied system now and later put in a
battery-backed system?
Both
off-grid and grid-tied systems use the same solar panels. If you want to
add batteries to a grid-tied system, you will need to replace the
current inverter with a special hybrid device. Although this is
possible, it could be fairly costly.
What kind of warranty do PV systems have?
Most solar
panels have a 25-year manufacturer's warranty, while inverters normally
have a 10-year warranty. The performance efficiency for solar panels is
at least 80% of the original output after 20 to 25 years. Batteries that
are used on a non-grid system should last between 7 and 10 years. The
warranty time varies on batteries depending on the manufacturer.
The actual installation is normally guaranteed for approximately
5 years.
Does my solar system produce electricity on a cloudy day?
Solar
systems will produce electricity even with some cloudy conditions. There
is a certain amount of UV light even with clouds or fog. The solar
production will be diminished considerably, the cloudier it is. You may
easily lose 60-80% of production.
Is there a way to know if my system is producing what it is supposed to?
Yes, you can
monitor your solar production. Some companies offer a web-based tool to
monitor the system in real time. Other companies offer a remote monitor
that is mounted in a convenient place to monitor the output power. Many
of these monitors provide current output production, daily output
readings and even monthly readings. After monitoring your system for a
couple of months or so, you will be able to determine if it is producing
close to normal. If you suspect a drop off, contact the installation
company and they will normally recheck it for you.
Is there a way to keep power flowing during an electrical blackout?
The only way
to achieve this is to have a battery-backed solar system. A grid solar
system will only be powered when the grid is live.
What happens to my solar system when I need to re-roof?
In most
situations, the PV panels can be easily removed and reinstalled. It is
normally a good idea to have your roof in good condition prior to
installing solar panels. If there is a chance of needing to replace
within the next ten years, it is probably a good idea to have the roof
replaced prior to installing your system.
What is net-metering?
Net-metering
measures the difference between the electricity you buy from your
utility company and the electricity that is produced through your solar
energy system. Any production of electrical power in excess is fed back
into the grid. As it passes into the grid, it causes your existing meter
to count backwards. Your electric meter keeps track of the “net”
difference of the electrical energy you provide and the amount you draw
from the utility grid.
Why is net-metering important?
Net metering
allows you to track all energy you produce in excess of your current
usage. If you didn’t have a meter to monitor the difference, you would
need to install a battery storage system. There will be days when your
system produces more than you use and other days where you use much more
than you produce. If your system is designed properly, your usage should
average out.
If I move, can I take my solar electric system with me?
You can take
a solar electric system with you if you move. The real question is
SHOULD I take my system with me? It is usually better to leave the
system on the original house since it increases the resale value of your
home. Also, you may qualify for tax incentives if you install a new
system on a new home.