Below you will find answers the most frequently asked questions about solar energy, solar water heating and photovoltaic systems to help you decide for yourself if it seems right for you.
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- What is solar energy?
- Why should I go solar?
- What is photovoltaics (or PV for short)?
- How can we get electricity from the sun?
- How does a solar photovoltaic system work?
- What are the components of a photovoltaic (PV) system?
- What’s the difference between PV and other solar energy technologies?
- How long do PV systems last?
- How much electricity does a photovoltaic (PV) system generate?
- Will photovoltaic electricty ever be competitive?
- Is My Home Suitable for Solar Energy?
- Will My Solar Panels Work When it’s Cloudy?
- Is solar power for everybody? What if I live up north?
- How will a solar energy system affect my home’s resale value?
Q: What is solar energy?
A: Solar energy is the general term used for capturing and using the sun’s energy to perform useful work, such as producing heating for homes or businesses or converting the sun’s energy into electricity. Solar thermal energy systems usually use rooftop panels to produce hot water or hot air for heating solar photovoltaic systems use photovoltaic cells to convert sunlight directly into electricity.
Q: Why should I go solar?
A: It benefits you, it benefits the environment, and it builds a sustainable future. Global warming, rising energy bills, and energy dependence affect all of us. More and more people want to become part of the solution. Solar energy is one of the best ways to make a real contribution to sustainability. More and more areas offer subsidies and rebate programs that make solar the smart choice – financially as well as environmentally. But solar is still new for a lot of people.
Q: What is photovoltaics (or PV for short)?
A: The word itself helps to explain how photovoltaic 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.
Q: How can we get electricity from the sun?
A: Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. When these free electrons are captured, an electric current results that can be used as electricity. 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.
With its newfound energy, the electron escapes from its normal position in an atom of the semiconductor material and 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 (such as a light bulb).
Q: How does a solar photovoltaic system work?
A: A solar photovoltaic system, uses specially prepared silicon materials to convert sunlight into electricity. These materials can be arranged into cells on panels or made into sheet material like a roll of linoleum. When exposed to sunlight, these materials release atomic electrons that produce a direct current (DC) flow of electricity similar to the energy that is stored in batteries. This direct current (DC) electricity can be used to power almost any device that runs on battery power, but is often converted to alternating current (AC) like the electricity on the power grid using a device called an inverter. This alternating current electricity can then be used to operate common household devices that are plugged into a wall receptacle.
Q: What are the components of a photovoltaic (PV) system?
A: A PV system is made up of different components. These include PV modules (groups of PV cells), which are commonly called PV panels; one or more batteries; a charge regulator or controller for a stand-alone system; an inverter for a utility-grid-connected system and when alternating current (ac) rather than direct current (dc) is required; wiring; and mounting hardware or a framework.
Q: What’s the difference between PV and other solar energy technologies?
A: There are four main types of solar energy technologies:
- Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials.
- Concentrating solar power (CSP) systems, which concentrate the sun’s energy using reflective devices such as troughs or mirror panels to produce heat that is then used to generate electricity.
- Solar water heating systems, which contain a solar collector that faces the sun and either heats water directly or heats a “working fluid” that, in turn, is used to heat water.
- Transpired solar collectors, or “solar walls,” which use solar energy to preheat ventilation air for a building.
Q: How long do PV systems last?
A: Photovoltaic (PV) cells are almost eternal in space, however on Earth, between our climate and atmospheric pollution, the connections and the conditioning elements on the panels are slowly destroyed.
Properly installed should last many years. The modules are guaranteed for, on average, 20 years for an 80% yield and are designed to resist in the most extreme climates.
Q: How much electricity does a photovoltaic (PV) system generate?
A: A 10% efficient PV system in most areas of the United States will generate about 180 kilowatt-hours per square meter. A PV system rated at 1 kilowatt will produce about 1800 kilowatt-hours a year. Most PV panels are warranted to last 20 years or more (perhaps as many as 30 years) and to degrade (lose efficiency) at a rate of less than 1% per year. Under these conditions, a PV system could generate close to 36,000 kilowatt-hours of electricity over 20 years and close to 54,000 kilowatt-hours over 30 years. This means that a PV system generates more than $10,000 worth of electricity over 30 years.
Q: Will photovoltaic electricty ever be competitive?
A: Photovoltaic technology is currently on an industrial level. The cost of this type of material has been steadily decreasing over the last 20 years, a decrease that will continue over the next few years. At the same time, the production costs of so-called traditional energy are increasing. Photovoltaic solar energy will therefore become more competitive in time, even without being subventionned.
Photovoltaic production has been doubling every two years, increasing by an average of 48 percent each year since 2002, making it the world’s fastest-growing energy technology.
Q: Is My Home Suitable for Solar Energy?
A: The basic minimum requirements for both solar water heating and PV systems are much the same, calling for unobstructed exposure to the sun during the sunniest part of the day - typically between 9am and 3pm – and the opportunity to mount the panels or cells at an angle around 20-50 degrees to get the most benefit. A south-facing roof which enjoys direct sunlight during the two hours either side of noon is particularly ideal.
Q: Will My Solar Panels Work When it’s Cloudy?
A: Obviously both PV and solar water heating work best when the sun shines, but even on cloudy days, all is not lost. When the sun does peep out from behind the clouds, there can often be enough heat to help warm the water, but there’s no escaping the fact that this sort of solar energy system really does need the sun’s warmth to make a serious contribution to household energy savings.
Modern PV systems run surprisingly well even under overcast skies and will continue to generate at least some electricity at quite low light levels – but as always, the sunnier the day, the better!
Q: Is solar power for everybody? What if I live up north?
A: Anybody who has a good site can benefit from a solar energy system. Once you get it installed, the power is free. And solar isn’t just for the sunny south – solar works in all areas with sunlight.
Q: How will a solar energy system affect my home’s resale value?
A: Studies show that most customers would pay more for a home with a solar system already installed. And of course, as energy costs rise, anything that lowers those costs will add to a home’s value.
