FAQ

BP Solar Systems

How will I use the electricity from a BP Solar energy system?

The electricity generated by a BP Solar energy system works just like the electricity delivered by your local utility. After passing through a component called an inverter, the direct current (DC) electricity generated by photovoltaic panels is converted to alternating current (AC), the type of electricity that you normally access through the outlets in your home or business facility. This AC electricity is either fed into your home for your use, or is fed back into the electricity grid if you are generating more than you are consuming.

Will a BP Solar energy system cover all my electricity needs?

Residential: Depending on your energy consumption and providing you have enough space, a solar system can be appropriately sized to meet all of your electricity needs, but in most cases it is not necessary for a system to cover all of your needs in order to be cost-effective. For instance, if your utility charges are based on a tiered rate structure, you pay an incrementally higher rate for each kilowatt-hour that you use. In this case, simply eliminating the most expensive portion of your consumption has a noticeable effect on your monthly utility bill. Your BP Solar Distributor or Dealer will assist you in deciding what size system is best for your home.

Commercial: Depending on your energy consumption and provided you have enough space, a solar system can be appropriately sized to meet all of your electricity needs, but in most cases it is not necessary or practical. Sizing a system to provide a portion - say 10% to 40% - of your facility's electricity demand, will reduce electricity demand during expensive peak daytime and summertime rate periods, while still maintaining a supply of electricity for remaining demand from your utility.

How much electricity will a BP Solar energy system produce?

The amount of electricity generated by a BP Solar energy solution is dependent upon several factors, primarily site compatibility and your local geographic and environmental conditions. Your Power Partner can provide an assessment of the energy a solar electricity system could provide for your home or business facility.

Will I need a utility provider? Will I need to be grid connected?

Residential: Unless you choose a standalone system with batteries, you will still need to be connected to the grid through your local utility. While you generate the bulk of your own electricity during the peak hours of daylight and demand, your utility will seamlessly take over and continue to supply your electricity at night and on very cloudy days. For remote, off-grid applications in which utility access is not feasible, standalone battery-backed systems are ideal.

Commercial: Unless you plan to generate all required power through an on-site generation system other than a solar electric system, your facility will still need to be connected to the grid through your local utility. While a BP Solar energy solution will generate a portion of your facility's electricity during the peak hours of daylight, your utility will seamlessly take over and continue to supply your electricity at night and on very cloudy days.

What will happen to a Grid Connect system during an electrical black out?

By law, any solar electricity system without generator backup must shut down until utility power returns in order to assure a safe working environment for utility line workers. The grid connect inverter will automatically shut itself off within a few milliseconds of a blackout, to avoid the potential of a dangerous "brown-out" in your home and to prevent back feeding the grid.  You will need a battery back-up system to maintain power during a blackout.  Discuss the basic requirements of this with your Power Partner.

How safe is a BP Solar energy system?

Solar energy systems are virtually maintenance free, and have no moving parts, they are very safe. BP Solar components carry all appropriate/recommended electrical certifications. As with any electrical appliance, you should always use proper care when handling solar system components, we recommend that installation and maintenance of solar systems be handled by trained solar installers and licensed electricians.

The science of photovoltaics

The solar cell is the heart of a solar electricity system. This is where the sun's energy is captured and turned into usable electricity for everyday use. Although making solar cells requires advanced technology, when connected together in a solar module, they are simple to use.
 
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, computer chips and other electronic devices.

A photovoltaic (PV) device (generally called a solar cell) consists of layers of semiconductor materials with different electronic properties. In a typical BP Solar 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 character. 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.

More about solar modules

The solar module (or panel) is comprised of several individual solar cells that are connected together and encapsulated in a protective envelope behind a sheet of protective glass. Combined with a metal frame and equipped with connectors, solar modules can be transported and connected in the field in a safe and practical manner.

By connecting solar panels in certain configurations (called a solar array), one can dictate the current and voltage of the array, thus dictating the electricity the system produces. The size of your solar electricity system will be dictated by the amount of space available or amount of daily energy required (loads) and the amount of solar energy available at your location. A professional supplier can assist you by performing a detailed analysis and preparing a quotation based on the analysis.

The output of a solar module is measured and rated in the factory at Standard Test Conditions (STC). For example a BP Solar 3160 is rated at 160 watts. This rating is used to size systems as well. An array of 20 BP 3160s on a home comprises a 3,200 watt system, commonly referred to as a 3.2 kilowatt (kW) system.

Solar and the environment

Photovoltaics (PV) are probably the most benign method of power generation known. They are silent, produce no emissions, and use no fuel (other than sunlight!). The production of PV of course, varies among manufacturers. BP Solar makes extensive use of recycled materials and even uses waste from other industries as raw material. BP Solar's PV technology is based on silicon, the second most common element on the earth's surface. As used in solar modules, silicon is non-toxic. A BP Solar module will re-generate the energy used in its manufacturing process in one to four years, depending on the application and location.

Solar performance factors

Weather naturally affects the performance of PV, but not entirely as you might expect. The amount of sunlight, of course, is most important in determining the output a solar electricity system will produce at a given location, but temperature is also important. Contrary to most people's intuition, photovoltaics actually generate more power at lower temperatures with other factors being equal. This is because solar PV cells are electronic devices and generates electricity from light, not heat. Like most electronic devices, PV operates more efficiently at cooler temperatures. In temperate climates, PV will generate less energy in the winter than in the summer, but this is due to the shorter days, lower sun angles and greater cloud cover, not the cooler temperatures.

PV is naturally inefficient in low sun and cloudy conditions. Typically, the output of any industrial solar module is reduced to 5-20% of its full sun output when it operates under cloudy conditions. Thus, PV does generate electricity in cloudy weather although its output is diminished.

What does BP Solar say about the efficiencies of various crystalline cells?

It sounds like a simple question. However, in practice there are a few variables. The simple answer is approximately 14 to 16% for monocrystalline cells (such as the BP Series) and 13 to 15% for polycrystalline cells (such as the SX Series). High efficiency monocrystalline cells (such as the BP Satumcells) featured on page 6 and 7, have an efficiency of approximately 16.5 %.

Variables include the type of anti-reflective coating the cell receives (most mono cells don’t use it; all poly cells have it) and also its encapsulation in a module. Both factors improve efficiency of a cell. Module efficiency is another matter. Polycrystalline cells make better use of the modules surface area while mono cells can’t be a s closely packed due to their shape.

For the end user, module efficiency is the most relevant perspective and the easiest to calculate. First, take the outer dimensions of the module’s rate power and divide it by its surface area. The resulting Watts per Square Meter will give you an estimate of the modular efficiency of an specific module, where 1000 Watts per Square Meter represent 110% efficiency.

What does BP Solar say about how modules are rated?

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), the intensity of radiation (1kW/square meter) and the spectral distribution of the light (air mass 1.5 or AM1.5, which is the spectrum of sunlight that has been filtered by the passing through 1.5 thickness of the earths atmosphere). These conditions correspond to noon on a clear sunny day with the sun about 60° above the horizon. The 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 the temperature is usually close to 25°C, a minor adjustment corrects output characteristics to the 25°C standard temperature.

 

Glossary

Solar Modules

Solar electric (photovoltaic or PV) modules convert the sun's light energy into direct current (DC) electricity. In most applications the panels are placed on the roof of a house. In a RAPS application, panels can be placed elsewhere on the property, in the best place to gain the greatest access to the sun.

 Inverter

In grid connect applications, the inverter converts the electricity produced by the solar PV modules from direct current (DC) to alternating current (AC), the same kind of electricity you use in your home.  In RAPS and recreational applications when back up batteries are used. The inverter is connected to the battery bank, and provides mains-type AC electricity to the system. The inverter needs to be sized to suit the system's electrical requirements. Your Power Partner will be install the inverter suitable to your size and type of application.

Solar Site

This exclusive wireless in-house display communicates with your Solar Energizer grid connect system to provide you with a digital readout of useful information - how much electricity your system is producing, how much your house is using, current time, solar intensity, and the cumulative electricity production of your system. This Solar Site comes supplied with a Solar Energizer grid connect system.

Utility Net Meter

The system connects to your main electrical supply. A net meter tracks net power usage, spinning forward when electricity is used from the grid, and backwards, generating a credit, when your system creates more electricity than is used. Your Power Partner will help liaison with the utility in your area to ensure you have the correct meter.

Regulators

In RAPS and recreational applications regulators (also called controllers) are installed to stope the battery bank from being overcharged when it is full. Solar panels produce unregulated, highly variable power flow and regulators controls the flow of this power.

Batteries

In RAPS and recreational applications, the energy collected from the modules is stored in large batteries. They are usually of lead-acid - either 'sealed' or 'flooded cell'. Your Power Partner will configure the size of battery bank you need according to your lifestyle and application. A properly sized, well maintained battery bank is vital to guarantee a reliable, long lasting system. Batteries require regular maintenance, such as topping up flooded cell type batteries with distilled water and charging and discharging to a timetable. Your Power Partner will discuss all of this with you during your initial consultation.

Battery Chargers

In RAPS and recreational applications battery chargers may be needed to charge batteries during periods of little or no sun. Batteries can be powered from either a direct DC charger, petrol powered generator or 240 Volt mains power. Your Power Partner has a variety of battery chargers available and will install the charger best suited to your lifestyle and application.

Courtesy of BP Solar