What are photovoltaics?

How does it work?

Is PV difficult to use?

How are modules rated?

What size solar system will I need?

Can solar systems be expanded at a future date?

Can 240V AC appliances be used?

Will any maintenance be required?

Are there different types of solar (PV) modules?

What size battery will I need in my non-grid-tied system?

Are special cables and fuses required?

Q. What are photovoltaics?

A. Photovoltaics are solid-state semiconductor devices that convert light directly into electricity. They are usually made of silicon with traces of other elements and are first cousins to transistors, LEDs and other electronic devices.

Q. How does it work?

A. A photovoltaic device (generally called a solar cell) consists of layers of semiconductor materials with different electronic properties. In a typical BP Solarex crystalline silicon cell, the bulk of the material is silicon, doped with a small quantity of boron to give it a positive or p-type character. A thin layer on the front of the cell is doped with phosphorous to give it a negative or n-type haracter. The interface between these two layers contains an electric field and is called a junction. Light consists of particles called photons. When light hits the solar cell, some of the photons are absorbed in the region of the junction, freeing electrons in the silicon crystal. If the photons have enough energy, the electrons will be able to overcome the electric field at the junction and are free to move through the silicon and into an external circuit. As they flow through the external circuit they give up their energy as useful work (turning motors, lighting lamps, etc.) and return to the solar cell. The photovoltaic process is completely solid-state and self-contained. There are no moving parts and no materials are consumed or emitted.

Q. Is PV difficult to use?

A. In a word, no. Although making PV cells and modules requires advanced technology, they're very simple to use. PV modules are generally low-voltage DC devices (although arrays of PV modules can be wired for higher voltages) with no moving or wearing parts. Once installed, a PV array generally requires no maintenance other than an occasional cleaning, and even that is not imperative. Most PV systems do contain storage batteries which can require some watering and maintenance similar to that required by the battery in an automobile.

Q. How are modules rated?

A. PV modules are rated at a well- defined set of conditions known as Standard Test Conditions (STC). These conditions include the temperature of the PV cells (25 C or 77 F.), the intensity of radiation (1 kW/square meter), and the spectral distribution of the light (air mass 1.5 or AM 1.5, which is the spectrum of sunlight that has been filtered by passing through 1.5 thicknesses of the earth's atmosphere). These conditions correspond to noon on a clear sunny day with the sun about 60 degrees above the horizon, the PV module directly facing the sun, and an air temperature of 0 C (32 F). In production, PV modules are tested in a chamber known as a flash simulator. This device contains a flash bulb and filter designed to mimic sunlight as closely as possible. It is accurate within about 3 1%. Because the flash takes place in only 50 milliseconds, the cells do not heat up appreciably. This allows the electrical characteristics of the module to be measured at a single temperature, the ambient temperature of the module/factory. Since this temperature is usually close to 25 C, a minor adjustment corrects output characteristics to the 25-degree standard temperature.

Q. What size solar system will I need?

A. The size of your system will be dictated by the amount of daily energy required (loads) and the amount of energy available at your location. A professional supplier will assist you by performing a detailed analysis and preparing a quotation based on the analysis. Using energy efficiently will reduce the cost of your system.

Q. Can solar systems be expanded at a future date?

A. Yes. All systems will be designed to grow with your needs. Some minor components may need replacing, but they are generally inexpensive. It is important to point out to any supplier hat you may wish to expand your system in the future.

Q. Can 240V AC appliances be used?

A. Yes. By installing an inverter in your system the DC electricity produced by Solar Panels can be converted into 240V AC. Solar systems are versatile and therefore you can use 240V AC and DC voltages if required.

Q. Will any maintenance be required?

A. Yes, but only a small amount. Modern Solar Systems can provide a large amount of information to assist you and can automatically perform some functions. Ensuring that the Solar Panels are clean and that the battery water level is sufficient are the major tasks. Systems that are grid tied and have no batteries are extremely low maintenance.

Q. Are there different types of solar (PV) modules?

A. Yes. Modules are available in different power outputs, frame types, cell technology, life xpectancy and efficiency. These factors will determine the best panel to suit your needs. If you are comparing brands make sure you know what you are getting. All firms have a wide range of high efficiency solar modules to suit virtually every application.

Q. What size battery will I need in my non-grid-tied system?

A. Car batteries are not suitable for use in solar systems. Only batteries designed for repeated charging and discharging will provide a good level of performance and life expectancy. There are a wide range of batteries which are all specifically designed for use in solar systems.

Q. Are special cables and fuses required?

A. Yes. Even if there is an inverter in your system, there will still be some DC electricity. DC electricity requires larger wire and in some cases, special fusing and protection. Ensure that your installer is experienced in regard to DC electricity, knowledgeable in the relevant standards and preferably accredited. All firms have designed and supplied components for hundreds of different applications - we have categorized them here as • 'Homes and Lives' for those applications that affect the way you live, like cleanly powering your urban home, bringing electricity to remote villages and rural homes, powering remote hospital and school facilities or simply powering your camper van, RV or boat. • 'Industrial' for telecommunications, oil and gas, beacons, navigation aids, lights, farming products and other such products and systems for helping industry. • 'Commercial' for systems applied on offices and factories for powering your companies work and image."