There is a lot of information and misinformation around solar photovoltaic (PV) and solar thermal energy. We hope we can answer most of your questions below. If not, our expert staff is willing to answer any further questions on the phone or via email. The basics...
Qs: What is photovoltaics (solar electricity), or 'PV'?
Ans: A PV system is made up of different components. These include PV modules (groups of PV cells), which are commonly called PV panels; a charge regulator or controller for a stand-alone system; an inverter for converting alternating current (ac) rather than direct current (dc) is required; wiring; and mounting hardware or a framework.
Qs: What are the components of a photovoltaic (PV) system?
Ans: The word itself helps to explain how photovoltaic (PV) or solar electric technologies work. The word has two parts: photo, a stem derived from the Greek phos, which means light, and volt, a measurement unit. So, photovoltaics could literally be translated as light-electricity. And that is just what photovoltaic materials and devices do; they convert light energy to electricity.
Qs: How does the system work?
Ans: Daylight hits the photovoltaic cells and is converted to clean electricity. The inverter converts the electricity from direct to alternating current, for use in the home. When the solar energy system is producing more power than is needed it is exported to the grid. At night, power is imported from the grid in the normal way.
Qs: What's the difference between PV and other solar energy technologies?
Ans: There are four main types of solar energy technologies: 1. Photovoltaic (PV) systems, which convert sunlight directly to electricity by means of PV cells made of semiconductor materials. 2. 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. 3. 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. 4. Transpired solar collectors, or solar walls, which use solar energy to preheat ventilation air for a building.
Qs: What is the difference between a kilowatt (kW) and a unit or a kilowatt hour (kWh)?
Ans: A kW is a thousand watts and a unit of power. It measures the rate of energy conversion. A kWh is the amount of work done, or energy used, when a kW of power works for one hour.
Qs: What is a kWp, and how does it relate to kW and kWh?
Ans: A kWp is the kilowatt 'peak' of a system. This is a standardized test for panels across all manufacturers to ensure that the values listed are capable of comparison. The test conditions for module performance are generally rated under Standard Test Conditions (STC) : irradiance of 1,000 W/m2, a module temperature at 250C and a solar spectrum of AM 1.5. This spectrum can be found here, but is unlikely to be of any interest to anyone outside the industry. Suffice to say that it is a standardized test.
Qs: Do Solar Panels create energy?
Ans: A basic tenet of thermodynamics is that energy is never actually created only converted; solar panels convert solar energy into electricity rather than just creating it.
Qs: Will they work during the winter?
Ans: Yes. Solar panel suppliers have enhanced the efficiency of solar power systems to the extent that it is now a very viable option in all climates. The important thing to bear in mind is that solar power depends on intensity of light, not necessarily direct sunlight. So even when it's overcast, your solar panels will be producing clean electricity.
Qs: Does the system need batteries?
Ans: Batteries are only required if you want a truly off-grid solution and independence from any power cuts that might occur. They are also required if you own a property which is not attached to the grid in order that power produced during the day can be stored for use in the evening. Batteries add significant costs to a solar system so are normally only never offered with a grid tied solar PV system.
Qs: What does energy conversion efficiency mean?
Ans: Energy conversion efficiency is an expression of the amount of energy produced in proportion to the amount of energy consumed, or available to a device. The sun produces a lot of energy in a wide light spectrum, but we have so far learned to capture only small portions of that spectrum and convert them to electricity using photovoltaics. So, today's commercial PV systems are about 7% to 17% efficient, which might seem low. And many PV systems degrade a little bit (lose efficiency) each year upon prolonged exposure to sunlight. For comparison, a typical fossil fuel generator has an efficiency of about 28%. Researchers are working on ways to convert more of the energy in sunlight to usable energy and increase the efficiency of PV systems, however. Some experimental PV cells now convert nearly 40% of the energy in light to electricity