What Are Photovoltaic (PV) Cells & How Does PV Work?

Photovoltaics is the direct conversion of light into electricity at the atomic level. Photovoltaics are best known as a method for generating electric power by using solar ‘cells’ to convert energy from the sun into electricity. Photovoltaic cells power solar powered panels you can buy and have installed on the roof of your home or walls (Building Integrated Photovoltaics or BIPV).

Each pv cell is made from a few layers of semiconducting material – commonly Silicon (Si). When sunlight shines on the pv cell it creates an electric field across the layers (known as the photovoltaic effect). The photovoltaic effect refers to light (actually, photons of light) knocking electrons into a higher state of energy to create electricity. Virtually all photovoltaic devices are some type of photodiode.

Solar cells produce direct current electricity from sun light, which can be used to power equipment or torecharge a battery. The first practical application of photovoltaics was to power orbiting satellites and otherspacecraft, but today the majority of photovoltaic modules are used for grid connected power generation. In this case an inverter is required to convert the DC to AC. There is a smaller market for off-grid power for remote dwellings, boats,recreational vehicles, electric cars, roadside emergency telephones, remote sensing, and cathodic protection of pipelines. WIKIPEDIA

Put simply, the stronger the sunshine that day, the more electricity is produced by the solar panels that day. The amount of electrical energy the photovoltaic cell generates in full sunlight is measured in kilowatt peak (kWp).

Photovoltaic Panels on Roof

PV cells come in many types, shapes and colours, from grey “solar tiles” that mimic normal roof tiles, to solar panels and transparent cells (for your conservatory, and glass, for instance).

Is My Home Suitable to Generate Solar Electricity?

Is solar electricity right for you?

  • Do you have a sunny place to install photovoltaic panels? You’ll need a roof ,or wall, that faces within 90 degrees of south in the UK, and a roof which is not overshadowed by buildings or trees or something else which prevents the sun shining directly on the pv system. If the surface is in shadow for parts of the day, your solar panel system will generate less energy.
  • Do you need planning permission for solar panels? In Scotland, England, Wales and Northern Ireland, you probably do need planning permission for most domestic or residential solar electricity systems, as long as they’re kept below a certain size – but you should ALWAYS check with your local town planning officer, especially if your house is a listed building, or is in a conservation area or especially a World Heritage Site. Take note!
  • Is roof you site under strong enough? Today’s Solar panels are not light and the roof of your home must be strong enough to take their actual weight, especially if the solar panel array is placed on top of existing roof tiles.

Average Cost Of Photovoltaic Cells

What is the cost of photovoltaic cells for sale? Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics has declined steadily since the first solar cells were manufactured.

Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have supported solar PV installations in many countries.

Cost, Savings and Maintenance of Solar Panels

Costs for installing a solar electricity system vary a lot – an average system (2.2kW) costs around £12,000 (including VAT at 5%). Per kW, solar electricity systems can cost in the region of £4,500 to £8,000 per kW, but costs per kW should reduce as system size increases. Energy Saving Trust

How Much Do Domestic Photovoltaic Cells Systems Cost? The cost/price of domestic or residential pv systems to buyvary (we have photovoltaic cells systems for sale in sizes 1 – 4KW) and we can also install free solar panels for your home under the UK government feed in tariff! Contact us to find out more about buying a pv system, or having photovoltaic solar panels installed on your roof!

In general:

  • if you need to have major roof repairs, solar PV tiles can offset the cost of roof tiles
  • solar panels built into a roof are usually more expensive than those that sit on top but the more electricity the solar system can generate, the more it costs but the more it could save
  • solar tiles cost more than conventional solar panels
  • Savings made from photovoltaic cells can be considerable – around 1 tonne of CO2 a year.
  • A 2.2 kWp system can be expected to generate around 40% of a household’s yearly electricity needs.
  • If the installed system is eligible to receive the Feed In Tariff it could generate savings and income of around £900 per year.
  • Maintenance of solar pv is generally easy – but you’ll need to keep the solar panels relatively clean and make sure trees don’t begin to overshadow them, for instance.

Selling Your Own Electricity Back To The Grid

You can make money on the excess electricity your pv cells generate by selling it back to the Grid through a scheme called Feed in Tariffs (FITs). Certification for solar products and photovoltaic installers is now provided through the UK Microgeneration Certification Scheme.

Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels comprising a number of cellscontaining a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon,polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium selenide/sulfide. Due to the growing demand for renewable energy sources, the manufacturing of solar cells and photovoltaic arrayshas advanced considerably in recent years. WIKIPEDIA

Global Solar Power
Average solar irradiance, watts per square metre. Note that this is for a horizontal surface, whereas solar panels are normally mounted at an angle and receive more energy per unit area. The small black dots show the area of solar panels needed to generate all of the world’s energy using 8% efficient photovoltaics.

What Are The Benefits of Solar Electricity?

  • Reduce your carbon footprint: A carbon footprint is the measure of the impact your activities have on the environment around you, and in particular, relevant to climate change. A carbon footprint relates to the amount of greenhouse gases produced in day-to-day lives via the burning of fossil fuels for electricity purposes, transportation and heating etc etc. The carbon footprint is a measurement of all greenhouse gases we individually produce and has units of tonnes (or kg) of carbon dioxide equivalent. Solar electricity (using solar photovoltaics), of course, is a form of  GREEN, renewable energy and as such does not release any harmful carbon dioxide (CO2) or other pollutants. A typical solar PV system in a modern home could save homeowners around 1tonne of CO2 per year – that’s around 25 tonnes over its lifetime!
  • Save money on your electricity bills: sunlight is 100% free, so once you’ve paid for the initial installation your electricity bills will be cut GREATLY. By having a regular home photovoltaic system installed, customers can produce around 40% of the electricity their household uses in a whole year.
  • Store electricity for a cloudy day: if your home isn’t connected to the UK national electricity grid via the Feed-in Tariff, you can store the excess electricity generated in batteries to use later when you need it.
  • Sell electricity back to the Grid: if your solar pv system is producing more electricity than you use, or when you can’t use it, someone else can use it – so you could make a bit of money too, through the Government’s Feed-in Tariff.
  • An Environmentally friendly energy source.
  • Works throughout the year using only daylight.
  • Could reduce your electricity bill to nothing depending on the size of system purchased and the amount of electricity you use.
  • Enhance the value of your property
  • Power Companies will buy back your extra electricity at 41.3p per/unit from April 2010
  • No maintenance required, with an expected life of 30 years plus.
  • Silent operation
  • Clean and Tidy Installation which requires minimal extra space.
  • Council planning authorisation not necessary. (in many situations…)

Advantages of Solar PV

  • The 89 petawatts of sunlight reaching the Earth’s surface is plentiful – almost 6,000 times more than the 15 terawatts equivalent of average power consumed by humans.
  • Additionally, solar electric generation has the highest power density (global mean of 170 W/m²) among renewable energies.
  • Solar power is pollution-free during use. Production end-wastes and emissions are manageable using existing pollution controls.
  • End-of-use recycling technologies are under development  and policies are being produced that encourage recycling from producers.
  • PV installations can operate for many years with little maintenance or intervention after their initial set-up, so after the initial capital cost of building any solar power plant, operating costs are extremely low compared to existing power technologies.
  • Solar electric generation is economically superior where grid connection or fuel transport is difficult, costly or impossible. Long-standing examples include satellites, island communities, remote locations and ocean vessels.
  • When grid-connected, solar electric generation replaces some or all of the highest-cost electricity used during times of peak demand (in most climatic regions). This can reduce grid loading, and can eliminate the need for local battery power to provide for use in times of darkness. These features are enabled by net metering. Time-of-use net metering can be highly favorable, but requires newer electronic metering, which may still be impractical for some users.
  • Grid-connected solar electricity can be used locally thus reducing transmission/distribution losses (transmission losses in the US were approximately 7.2% in 1995).
  • Compared to fossil and nuclear energy sources, very little research money has been invested in the development of solar cells, so there is considerable room for improvement. Nevertheless, experimental high efficiency solar cellsalready have efficiencies of over 40% in case of concentrating photovoltaic cells and efficiencies are rapidly rising while mass-production costs are rapidly falling. WIKIPEDIA

Disadvantages of Solar PV

  • Photovoltaics can be costly to install.
  • While the modules are often warranteed for upwards of 20 years, much of the investment in a home-mounted system may be lost if the home-owner moves and the buyer puts less value on the system than the seller.
  • Solar electricity is not produced at night and is much reduced in cloudy conditions. Therefore, a storage or complementary power system is required.
  • Solar electricity production depends on the limited power density of the location’s insolation. Average daily output of a flat plate collector at latitude tilt in the contiguous US is 3–7 kilowatt·h/m² and on average lower in Europe. Solar cells produce DC which must be converted to AC (using a grid tie inverter) when used in existing distribution grids. This incurs an energy loss of 4–12% WIKIPEDIA

More Info On Photovoltaics

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 was first noted by a French physicist, Edmund Bequerel, in 1839, who found that certain materials would produce small amounts of electric current when exposed to light. In 1905, Albert Einstein described the nature of light and the photoelectric effect on which photovoltaic technology is based, for which he later won a Nobel prize in physics.
The first photovoltaic module was built by Bell Laboratories in 1954. It was billed as a solar battery and was mostly just a curiosity as it was too expensive to gain widespread use. In the 1960s, the space industry began to make the first serious use of the technology to provide power aboard spacecraft. Through the space programs, the technology advanced, its reliability was established, and the cost began to decline. During the energy crisis in the 1970s, photovoltaic technology gained recognition as a source of power for non-space applications. NASA

Photovoltaic Systems

What are photovoltaic systems? A number of solar cells electrically connected to each other and mounted in a support structure or frame is called a photovoltaic module. Modules are designed to supply electricity at a certain voltage, such as a common 12 volts system. The current produced is directly dependent on how much light strikes the module.

see caption

Multiple modules can be wired together to form an array. In general, the larger the area of a module or array, the more electricity that will be produced. Photovoltaic modules and arrays produce direct-current (dc) electricity. They can be connected in both series and parallel electrical arrangements to produce any required voltage and current combination.

see captionToday’s most common PV devices use a single junction, or interface, to create an electric field within a semiconductor such as a PV cell. In a single-junction PV cell, only photons whose energy is equal to or greater than the band gap of the cell material can free an electron for an electric circuit. In other words, the photovoltaic response of single-junction cells is limited to the portion of the sun’s spectrum whose energy is above the band gap of the absorbing material, and lower-energy photons are not used.

One way to get around this limitation is to use two (or more) different cells, with more than one band gap and more than one junction, to generate a voltage. These are referred to as “multijunction” cells (also called “cascade” or “tandem” cells). Multijunction devices can achieve a higher totalconversion efficiency because they can convert more of the energy spectrum of light to electricity.

As shown below, a multijunction device is a stack of individual single-junction cells in descending order of band gap (Eg). The top cell captures the high-energy photons and passes the rest of the photons on to be absorbed by lower-band-gap cells.

see captionMuch of today’s research in multijunction cells focuses on gallium arsenide as one (or all) of the component cells. Such cells have reached efficiencies of around 35% underconcentrated sunlight. Other materials studied for multijunction devices have been amorphous silicon and copper indium diselenide.

As an example, the multijunction device below uses a top cell of gallium indium phosphide, “a tunnel junction,” to aid the flow of electrons between the cells, and a bottom cell of gallium arsenide.

Cells require protection from the environment and are usually packaged tightly behind a glass sheet. When more power is required than a single cell can deliver, cells are electrically connected together to form photovoltaic modules, or solar panels. A single module is enough to power an emergency telephone, but for a house or a power plant the modules must be arranged in multiples asarrays. Although the selling price of modules is still too high to compete with grid electricity in most places, significant financial incentives in Japan and then Germany, Italy, Greece and France triggered a huge growth in demand, followed quickly by production. In 2008, Spain installed 45% of all photovoltaics, but a change in law limiting the feed-in tariff is expected to cause a precipitous drop in the rate of new installations there, from an extra 2500 MW in 2008, to an expected additional 375 MW in 2009.

A significant market has emerged in off-grid locations for solar-power-charged storage-battery based solutions. These often provide the only electricity available. The first commercial installation of this kind was in 1966 on Ogami Island in Japan to transition Ogami Lighthouse from gas torch to fully self-sufficient electrical power. Due to the growing demand for renewable energysources, the manufacture of solar cells and photovoltaic arrays has advanced dramatically in recent years.

Photovoltaic production has been increasing by an average of more than 20 percent each year since 2002, making it the world’s fastest-growing energy technology. At the end of 2009, the cumulative global PV installations surpassed 21,000 megawatts. Germany installed a record 3,800 MW of solar PV in 2009. Roughly 90% of this generating capacity consists of grid-tied electrical systems. Such installations may be ground-mounted (and sometimes integrated with farming and grazing)  or built into the roof or walls of a building, known as Building Integrated Photovoltaics or BIPV for short. Solar PV power stations today have capacities ranging from 10–60 MW although proposed solar PV power stations will have a capacity of 150 MW or more.

World solar photovoltaic (PV) installations were 2.826 gigawatts peak (GWp) in 2007, and 5.95 gigawatts in 2008, and 7.5 gigawatts in 2009. The three leading countries (Germany, Japan and the US) represent nearly 89% of the total worldwide PV installed capacity. According to Navigant Consulting and Electronic Trend Publications, the estimated PV worldwide installations outlooks of 2012 are 18.8GW and 12.3GW respectively. Notably, the manufacture of solar cells and modules had expanded in recent years.

Germany installed a record 3,800 MW of solar PV in 2009; in contrast, the US installed about 500 MW in 2009. The previous record, 2,600 MW, was set by Spain in 2008. Germany was also the fastest growing major PV market in the world from 2006 to 2007 industry observers speculate that Germany could install more than 4,500 MW in 2010. The German PV industry generates over 10,000 jobs in production, distribution and installation. By the end of 2006, nearly 88% of all solar PV installations in the EU were in grid-tied applications in Germany. Photovoltaic power capacity is measured as maximum power output under standardized test conditions (STC) in “Wp” (Watts peak). The actual power output at a particular point in time may be less than or greater than this standardized, or “rated,” value, depending on geographical location, time of day, weather conditions, and other factors. Solar photovoltaic array capacity factors are typically under 25%, which is lower than many other industrial sources of electricity. Therefore the 2008 installed base peak output would have provided an average output of 3.04 GW (assuming 20% × 15,200 MWp). This represented 0.15 percent of global demand at the time.

The EPIA/Greenpeace Advanced Scenario shows that by the year 2030, PV systems could be generating approximately 1,864 GW of electricity around the world. This means that, assuming a serious commitment is made to energy efficiency, enough solar power would be produced globally in twenty-five years’ time to satisfy the electricity needs of almost 14% of the world’s population.

Pros & Cons ….

Photovoltaic systems have a number of merits and unique advantages over conventional power-generating technologies. PV systems can be designed for a variety of applications and operational requirements, and can be used for either centralised or distributed power generation. PV systems have no moving parts, are modular, easily expandable and even transportable in some cases. Energy independence and environmental compatibility are two attractive features of PV systems. The fuel (sunlight) is free, and no noise or pollution is created from operating PV systems. In general, PV systems that are well designed and properly installed require minimal maintenance and have long service lifetimes.
At present, the high cost of PV modules and equipment (as compared to conventional energy sources) is the primary limiting factor for the technology. Consequently, the economic value of PV systems is realised over many years. In some cases, the surface area requirements for PV arrays may be a limiting factor. Due to the diffuse nature of sunlight and the existing sunlight to electrical energy conversion efficiencies of photovoltaic devices, surface area requirements for PV array installations are on the order of 8 to 12 m2 per kilowatt of installed peak array capacity.

What Is The Optimum Orientation of Solar Panels?

For best performance, terrestrial PV systems aim to maximize the time they face the sun. Solar trackers aim to achieve this by moving PV panels to follow the sun. The increase can be by as much as 20% in winter and by as much as 50% in summer. Static mounted systems can be optimized by analysis of the Sun path. Panels are often set to latitude tilt, an angle equal to the latitude, but performance can be improved by adjusting the angle for summer or winter.

Making The Most Of Solar Electricity

To make electricity you produce go further:

  • invest in energy efficient appliances.
  • use energy when it’s sunyn is out – do your laundry during the day to take advantage of the free electricity!

If all suitable roofs in the UK was installed with solar photovoltaic’s (PV), we would surpass the countries complete electricity requirements. Solar photovoltaic’s offer huge potential to deliver environmentally friendly energy to help the climate.

In Summary

“Photovoltaic” is a conjunction of two words: “photo”, with Greek origins, meaning light, and “voltaic”, from “volt”, which is the measurement used to define electric potential across a point.

Solar radiation is transformed using Photovoltaic cells. The cell consists of one or two layers of a semi-conducting element. When light shines on the cell it provides an electric field across the layers, causing electricity to flow. The better the strength of the light, the bigger the flow of electricity is.

The most abundant semi conductor material made use of in photovoltaic cells is silicon, a material readily available in sand. There is no limitation to its availability as a raw material as silicon is the second most plentiful element in the Earth’s mass.

A photovoltaic system therefore does not need intense sunlight to function. It will additionally produce electricity on overcast days. Due to the reflection of sunlight, slightly cloudy days may even produce higher energy yields than days with a clear blue sky.

Photovoltaic Cells For Sale! Contact Us Today For A Free Quote!

Photovoltaic cells for sale? The installation procedure can be done with minimum disturbance, is backed with a 25 year guarantee and most notably – there is government allowances currently available (in Scotland). We can also put together a tremendous financial deal – why not give us a call for a survey right away and start to get “ELECTRICITY FOR FREE”.