Solar Electricity FAQs
What is photovoltaics (solar electricity) or “PV”?
The word itself helps to explain how photovoltaic (PV) or solar electric technologies work. First used in about 1890, the word has two parts: photo, a stem derived from the Greek phos, which means light, and volt, a measurement unit named for Alessandro Volta (1745-1827), a pioneer in the study of electricity. So, photovoltaics could literally be translated as light-electricity. And that’s just what photovoltaic materials and devices do; they convert light energy to electricity, as Edmond Becquerel and others discovered in the 18th Century.
How can we get electricity from the sun?
When certain semiconducting materials, such as certain kinds of silicon, are exposed to sunlight, they release small amounts of electricity. This process is known as the photoelectric effect. The photoelectric effect refers to the emission, or ejection, of electrons from the surface of a metal in response to light. It is the basic physical process in which a solar electric or photovoltaic (PV) cell converts sunlight to electricity.
Sunlight is made up of photons, or particles of solar energy. Photons contain various amounts of energy, corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the PV cell (which is actually a semiconductor).
With its newfound energy, the electron escapes from its normal position in an atom of the semiconductor material & becomes part of the current in an electrical circuit. By leaving its position, the electron causes a hole to form. Special electrical properties of the PV cell (a built-in electric field) provide the voltage needed to drive the current through an external load (ie. light bulb).
What is a kWh?
A kWh (pronounced “kilo watt hour”) is a specific amount of electricity. 1 Kwh is identical to 1 unit of electricity that is shown on your electricity bill. An electrical item having a rating of 1kW will consume 1kWh for every hour it is on at full power.
What are the components of a photovoltaic (PV) system?
There are two types of PV systems. Grid-tied and battery back-up. The most common, a grid-tied system, includes PV modules (groups of PV cells), which are commonly called PV panels; framework; an inverter; wiring; & mounting hardware. The lesser common, a battery back-up system (also known as a stand-alone system) includes PV modules; framework; an inverter; a charge controller; one or more batteries; wiring & mounting hardware.
What is an inverter?
There are two kinds of electricity, DC (direct current) and AC (alternating current). Homes that are connected to utility power use AC electricity. Flashlights, small radios and automobiles use DC electricity. Solar inverters convert the electricity from your solar panels (DC) into power that can be used by the plugs in your house (AC).
There are different kinds of inverters. String inverters convert DC to AC using one inverter for many panels. A newer and far more efficient type of inverter, called micro inverters, are used on a 1:1 ratio. One micro inverter per panel. An inverter converts power at the lowest producing panel rate. Therefore, when a cloud passes by a system on a string inverter and covers only one panel, the entire system will not produce it’s full capacity. A system with micro inverters would only be affected on the one panel with it’s own micro inverter. Solar systems that use string inverters cannot be easily added to, as a full new string inverter with it’s own panels, wiring, electrical upgrade, etc. would need to be added. On the other hand, a solar system that uses micro inverters could easily add as few panels with micro inverters as desired. This provides the customer with much more flexibility in the future should they decide to change their electricity use habits. A customer could add a hot tub or pool. To become less dependent on fossil fuels, they might want an electric car. With the use of micro inverters the solar system could easily be added to.
Why should I purchase a PV system?
People decide to buy solar energy systems for a variety of reasons. For example, some individuals buy solar products to preserve the Earth’s finite fossil-fuel resources and to reduce air pollution. Others would rather spend their money on an energy-producing improvement to their property than send their money to a utility. Some people like the security of reducing the amount of electricity they buy from their utility, because it makes them less vulnerable to future increases in the price of electricity. Finally, some individuals live in areas where the cost of extending power lines to their home is more expensive than buying a solar energy system.
How long do photovoltaic (PV) systems last?
A PV system that is designed, installed, and maintained well will operate for more than 20 years. The basic PV module (interconnected, enclosed panel of PV cells) has no moving parts and can last more than 30 years. The best way to ensure and extend the life and effectiveness of your PV system is by having it installed and maintained properly. Experience has shown that most problems occur because of poor or sloppy system installation.
Can I use photovoltaics (PV) to power my home?
PV can be used to power your entire home’s electrical systems, including lights, cooling systems, and appliances. PV systems today can be blended easily into both traditional and nontraditional homes. The most common practice is to mount modules onto a south-facing roof or use a ground mounting frame of some sort.
Can I supply electricity for my business?
Commercial facilities with access to a good southern exposure can be great candidates for solar photovoltaic systems. Restaurants, bakeries, beauty salons, health clubs, and hotels are all potentially good sites. A commercial installation generally makes use of the same components as residential systems but may need larger arrays. Bristol Electronics can help you determine the applicability of solar for your site.
What is net metering? Is it available where I live and work?
Net metering is a policy that allows homeowners to receive the full retail value (the per kWh price you are paying for your usage PLUS a $.06/kWh premium for EVERY kWh produced, if within Vermont) for the electricity that their solar energy system produces. The term net metering refers to the method of accounting for the photovoltaic (PV) system’s electricity production. Net metering allows homeowners with PV systems to use any excess electricity they produce to offset their electric bill. As the homeowner’s PV system produces electricity, the kilowatts are first used for any electric usage within the home. If the PV system produces more electricity than the homeowner needs, the extra kilowatts are fed into the utility grid and a credit is generated for future use.
How do I know if I have enough sunlight for PV?
A photovoltaic (PV) system needs unobstructed access to the sun’s rays for most or all of the day. Shading on the system can significantly reduce energy output. Climate is not really a concern, because PV systems are relatively unaffected by severe weather. In fact, some PV modules actually work better in colder weather. Most PV modules are angled to catch the sun’s rays, so any snow that collects on them usually melts quickly. There is enough sunlight to make solar energy systems useful and effective nearly everywhere in Vermont.
Does PV work in cloudy weather?
The sun must be “out” in order to gather maximum solar energy, however, as long as there is ambient light, a photovoltaic system will produce some power.
How big a solar energy system do I need?
The size of solar system you need depends on several factors such as how much electricity or hot water or space heat you use, the size of your roof or the size of the property to install a ground mounted system, and how much you’re willing to invest. Do you want the system to cover your complete energy needs or to supply a portion of them? Bristol Electronics can help you calculate your options, however the following calculation may help to get you started:
To determine your desired system capacity, Please fill-in the following if you know your average monthly electricity costs in dollars
Enter your average monthly electricity cost in dollars: $___________
Multiply the above line by 12 to get your average annual electricity cost in dollars: $____________
Divide the above number by .145 (or YOUR average cost of one kWh over the past year): ________ total kWh last year
Multiply the above number by .70 (For every kWh you use, you are charged one rate, for every kWh you make, you are paid 6 cents higher, this calculation allows for that benefit): _____________
Divide the above number by 1000: ________ kW ~ This is the size system you should consider.
Will my property taxes go up if I install a solar energy system?
In Vermont real estate taxes are generally not charged on solar systems at this time. Please check with your local town clerks office to confirm this within your town.
Will a solar energy system add equity to my home?
We are finding financial institutions are lending money based on the added equity and real estate appraisers are recognizing the added value for resale
Do I have to change my habits to use a solar a PV system?
No however, you may find yourself parked in front of your electric meter on sunny days watching it spin backward with a gigantic smile on your face. You may find that you choose to use your electricity in different ways than you have in the past. You may find that you are more conservative with your usage or maybe this year you will splurge and have a larger holiday light display?
Where are the panels installed?
In a shade-free location, usually on a sloped or flat roof, although a rack on the ground is an option. South-facing panels are ideal, but West-facing panels are also possible.
What is the proper orientation of the solar collector?
Collectors should be mounted on an un-shaded area of a south-facing roof. They can face up to 45 degrees west of south with some decrease in performance. Mounting the panels on an outbuilding or a ground mounted system might be an option for these homes.
Will I have electricity during power outages?
For the safety of electrical workmen our standard systems do not operate during power outages. We can offer an upgrade that enables the system to automatically disconnect your property from the grid and to provide power from the panels and a battery back up in your property during power outages, however these upgrades are “usually” cost prohibitive.
How much do solar photovoltaic systems cost?
An installed solar photovoltaic system can range from $4,000 to $45,000 for residential purposes. The cost greatly depends on how much power you wish to produce, the mount type (roof mounted or ground mounted) and other installation details. Bristol Electronics provides free site evaluations to help you understand your particular needs and costs. Financial incentives such as rebates and tax credits will significantly reduce this price (by as much as 41% for some). Savings will increase as a greater percentage of your electricity is produced by free solar energy.
Are there financial incentives in addition to the fuel savings?
Federal and State tax credits, incentives and rebates from utilities have been created to encourage the use of solar technologies. Some apply only to residential installations and some are intended for commercial and government use. Funding, incentives and expiration dates change frequently. Currently, there is a federal tax credit available to help lower the final cost for residential systems. It is 30% of the installed cost and is scheduled to expire in 2016. The State of Vermont also offers a rebate to residential and commercial property owners who install solar photovoltaic systems. Bristol Electronics can help you figure out which tax credits and incentives you qualify for.