What Is Photovoltaic Solar Energy And How It Work?

Solar Energy / By
Photovoltaic Solar

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What is photovoltaic solar technology.

photovoltaic solar technology is a technology that uses solar panels to convert sunlight directly into electricity without the need for an external energy source.

It converts light from the sun into electric current through the photovoltaic effect.

It is considered an energy source that does not produce any pollution, while being extremely economical.

A great number of photovoltaic solar panels are used today as a source of energy for many households and complexes.

A photovoltaic cell is made up of silicon covered with a layer of an oxide (usually called “crystalline silicon”, that simulates the properties necessary to capture light from the sun and transform it into electricity.

Contrary to most people’s belief, when light falls on the cell, it does not pass directly through it, but rather its photons (particles of light) knock electrons loose within the silicon which in turn moves forward towards electron collectors at both ends where a circuit is complete and thus causing a flow of electricity.

In 1767 Joseph Priestley discovered that gases generate electricity if exposed to sunlight.

In 1839 Johann Heinrich Geissler created the first known prototype of a photovoltaic cell by covering a metal plate with selenium.

The invention of the silicon solar PV cell was announced in 1941 by Russell Ohl when he demonstrated it as part of the “sunpower project” at Bell Laboratories.

However, while other researchers were also working on solar cells during this time period, including Charles Fritts who reported his findings to American Physical Society in 1883 and Frank Irvine who presented his findings at the World Power Conference in 1955; but their early developments are not comparable with today’s modern devices due to various performance and efficiency shortfalls.

By 1954 scientists from six countries (including Russia) had developed efficient silicon solar cells but it wasn’t until the 1970s that large-scale manufacturing of photovoltaic arrays started.

Solar cells today are part of a vast industry and market, which uses semiconductor technology to convert sunlight into electricity.

PV is also widely used in remote power generation, such as telecommunication stations, off-grid homes, and rural electricity supply applications.

The majority of solar cells are now made from crystalline silicon (c-Si), accounting for over 90% of global production.

The c-Si material can either be deposited onto the substrate by chemical vapor deposition or spun on by an automated machine called a spinner.

However, other materials like copper indium gallium selenide (CIS/CIGS) and cadmium telluride (CdTe) are also used.

Each material has its own inherent advantages and disadvantages.

Solar cells made of silicon have been used for over 30 years and now dominate the market due to their high efficiency, low cost, abundance in nature, and ability to be fabricated at a large scale with easily available facilities.

While manufacturing techniques improve constantly, their performance is inherently limited by the materials which constitute them.

Silicon solar cells consist of two doped layers of p-type and n-type silicon called a p–n junction that create a boundary between electrically conductive regions in the top layer and an electron band gap region below it that does not conduct electricity; hence cannot transport electrons from one side of the device the other.

This situation creates a potential barrier which keeps the electrons from moving freely between the layers, so that when sunlight is absorbed by this layer the energy can only be released if an electron in filled up in its place and thus generates an electric current (by photon-assisted electron emission).

Solar cells are measured with respect to their efficiency at converting sunlight into electrical power.

The best laboratory confirmed cell efficiencies supercede 60%. A typical lab cell made of multicrystalline silicon has a conversion efficiency of 15% to 22%, while solar panels on photovoltaic modules typically have overall efficiencies of around 15–20%.

Newer processes and techniques such as heat treatment allow for more improvement in efficiency than just gradual increase with process alone.

The most efficient solar cells are made by depositing a thin layer of amorphous silicon on the top of an expensive substrate, such as sapphire or diamond.

These efficiencies are realized where inexpensive semiconductors can be used, such as in space applications, or very expensive ones for terrestrial use, such as building integrated photovoltaic’s (BIPV) to produce highly efficient power conversion systems that are also lightweight and flexible.

However other research is focused on how nanostructured layers with different band gaps than bulk silicon could allow for higher efficiency at lower cost due to lower processing temperatures and potentially high surface area per mass ratio.

The first commercial solar cell was presented by Fritts in 1954; he demonstrated this device to the American Society of Photovoltaic Engineers.

This device used a p-n junction constructed with selenium and produced around 1 mW at 91% efficiency.

The first photovoltaic solar panel was introduced by Bell Labs in 1962, which sold for $84 each.

As well as being expensive, silicon based solar cells are also relatively inefficient compared to other semiconductor devices such as CIGS cells or modern thin film solar cells (see AMSC and First Solar), due to their indirect band gap.

Amorphous silicon (a-Si) – known as “amorphous” because its structure is non-crystalline – is deposited using plasma-enhanced chemical vapor deposition methods on suitable substrates (usually glass, plastic or metal).

Amorphous silicon absorbs the most sunlight of any semiconductor material.

Because it is deposited from a gas onto a flat surface without requiring high temperatures, amorphous silicon can be made with almost arbitrary form factors and has hence been used for making flexible cells (see Asahi Kasei) and very thin wafer-based cells.

This property also makes amorphous silicon useful in photovoltaic applications where space limitations require small devices.

However, in spite of its superior energy conversion efficiency as compared to crystalline silicon (c-Si), it suffers from other tradeoffs.

When used in solar panels, it is not transparent to light so cannot be used on windows or anything that requires transparency such as a solar powered car, it easily cracks and is hard to handle when making thin films (due to the highly viscous nature of liquids in this state) and due to its relative lack of strength is not flexible enough for small bends.

Cadmium telluride (CdTe) absorbs light across most of the spectrum with an efficiency comparable to that of silicate-based cells.

CdTe has been used in many prototype devices over the years, but there are high costs associated with this technology as a result of the use of toxic cadmium compounds which are potentially damaging to living tissue.

Silicon makes up about 90% by weight of most commercial PV modules; however, more than twice as much semiconductor material must be used to achieve the same power output for a CdTe module as for a silicon-based cell of the same dimensions.

The benefits of photovoltaic solar technology

Benefits of photovoltaic solar technology include an absence of moving parts, installation without the use of heavy lifting equipment so it can be done by relatively unskilled personnel.

These benefits are offset by the cost of photovoltaic solar panels. This cost is lessened by government subsidies in many countries.

Absence of moving parts

Unlike large hydroelectric dams, which require a constant flow of water through turbines to generate power, or nuclear reactors that consume some fuel every day and produce radioactive waste, photovoltaic systems do not require constant attention.

As long as they receive adequate sunlight to produce more power than they consume on an annual basis, they are low-maintenance.

Installation without the use of heavy lifting equipment

Photovoltaic panels are often light and small enough to be installed on a building’s existing structure or roof. Typically, all that is needed is a screwdriver and wrench.

Photovoltaic panels are also light enough that they can be mounted on a structure or building using only wire, cable ties, and a minimum of four bolts with wing nuts.

Placing photovoltaic panels on existing structures such as buildings can reduce the cost of power generation because building owners and local municipalities do not need to pay for the expensive process required to obtain permits from city hall before starting any construction.

The installation of photovoltaic systems that power buildings such as homes and businesses can be done without the intervention of utility companies.

Photovoltaic panels do not produce noise or emissions during operation.

There can be a slight hum, however, when the inverter converts the DC current to AC current.

The inverter may produce an audible hum in certain conditions, even if prevented from doing so by a “fuse” or circuit breaker.

This can be remedied by ensuring proper grounding and wiring of the inverter, if necessary.

No moving parts

Photovoltaic panels have no moving parts, so they have no mechanical wear and tear.

They also require less time to install on a roof, which means construction crews can spend more time on other jobs.

Solar panels that are not properly grounded or installed in an area filled with metal can create an electrical hazard when they are wired to a grid connection, which is not the case with wind turbines.

No fuel consumption

Due to their passive nature, photovoltaic panels have no fuel consumption.

This means that photovoltaic panels are not dependent on firewood, propane or gasoline to operate. (See renewable energy).

No emissions

Photovoltaics have been shown to produce no air pollution nor greenhouse gases during operation and disposal of the devices cause little environmental impact.

Photovoltaic cells do contain toxic metals such as lead, cadmium, and selenium in their crystalline structure but according to a paper published by [Okonski], “all these materials can be collected at the end of cell life-cycle with relative ease”.

There is also potential for mining operations to extract additional valuable materials from photovoltaic modules. Unlike fossil fuels such as coal which release dioxide, photovoltaic modules produce no particulates, sulfur dioxide, or other gases.

In addition, they do not consume water for cooling purposes and the coolant fluids they use are already present in the building during the summer, so no additional water is needed.

Solar Energy Pros And Cons

The pros are the following:

1. Cheap to maintain and use, once they are in place.

2. Solar energy is easy to transport if you have a portable solar panel that you can move easily from one place to another.

3. Solar energy does not create greenhouse gas emissions, which means it is considered one of the cleanest and most environmentally friendly sources of energy.

4. It is free to use.

You will not have to pay anything in order for you to harness solar energy in order to power your home or business, unlike wind energy where you may be required to pay an installation fee so that a company can put up wind turbines for you, given the fact that there are plant and equipment costs involved also.

5. Solar-powered homes do not create noise pollution, since they do not need any machinery and other equipment that produces loud noises such as generators and others, which means it is quiet all throughout the whole day long.

The cons are the following:

1. It is not good for the electrical grid, since it can’t be regulated and used as a backup source when needed during blackouts or power failures.

2. It is not easy to transport from one place to another if you are using solar panels that are already placed on your homes and buildings.

3. It is not good for cooling homes or rooms, since it relies on the sun and heat to function well and produce electricity, which means that during winter time or rainy days solar energy cannot be produced at all.

4. The price of producing and delivering power through solar energy may exceed its benefits when compared with other conventional forms such as coal, natural gas and others, given the fact that there are very few photovoltaic manufacturers in the world today and their production rates cannot produce a high enough supply to match increasing demand.

This will only make photovoltaics even more expensive than they already are in such a case.”

How does a photovoltaic cell work?

An article on the National Renewable Energy Laboratory website explains that “In order for a semiconductor device to be considered a photocell, it must produce electricity directly from light.

There are three basic types of photocells:

1. Solar cell

Converts light energy to electrical energy; cells that do this are most widely used for electrical power generation

2. Photovoltaic (PV) cell

The term “photovoltaic” is derived from two words, photos and volt, which together mean ‘electricity from a solar cell’. PV cells convert sunlight directly into DC electricity.

3. Light-emitting diode (LED)

A semiconductor device that converts electricity to light.”

While photovoltaics are in direct competition with the conventional grid-based sources of power such as coal, natural gas and nuclear plants on a large scale, they can be used in conjunction with the conventional energy sources to meet an area’s electricity needs.

For example, solar panels can be placed at a remote or island location where it may not make economic sense to build a traditional power plant.

These areas are typically off-grid locations that do not have access to the electricity grid, and thus must rely on diesel-fueled generators for their electricity supply.

Photovoltaic panels can be a cost effective solution in these situations since they produce no air pollution and use no water in their operation (they only create steam when operating), two factors which contribute to lower costs if comparing them with other power plants.

In addition, fossil fuels such as coal require more manpower to extract than sunlight does in order for it to produce electricity, another cost saving factor.

In some countries such as Australia and New Zealand, photovoltaic power has been widely used for the remote areas such as desert locations.

The world’s largest solar demonstration is at a single location in the Australian desert near Cooktown.

Known as Solar One, it consists of nine square kilometers (about 3 1/2 square miles) of panels.

In these cases, utility-scale PV systems are typically employed which can be mounted on racks that are typically located about 6 feet above the ground or roof tops of buildings.

The technology behind this kind of system allows them to be spaced apart from 50 to 300 meters (160 to 980 feet), and they produce an average output power density up to 15 watts per square meter (70–200 watts per square foot).

In addition, utility-scale PV systems generally have a much higher overall capacity than small stand-alone solar power panels.

The fact that photovoltaic cells are located on a vast array of places such as rooftops and carports means that the need to transport electrical energy is not as important.

Instead the electricity can be simply transmitted to wherever it needs to go using wires which is not difficult considering that most developed countries already have wires installed in their cities and towns for regular electric usage.

This will make the costs of implementing PV technology significantly lower than other forms of alternative energy such as fuel cells or wind turbines.

In order for photovoltaics to economically compete with conventional forms of power, the cost of production must be reduced.

PV’s relatively high installation and maintenance costs are still a concern for power companies; however, because they operate on such large scales (typically 1-2 MW per system) these concerns have been lessened.

They have also included a 25-year guarantee to insure long term performance which can only help to improve their public image in addition to driving down the overall costs associated with them.

The future of photovoltaics looks bright as many countries around the world are tackling global warming by reducing their carbon emissions by focusing on renewable sources of energy.

As mentioned before it is not economical or practical for most small scale applications, but with efforts from many different sectors it has become an important part of the answer to global warming and the future of alternative energy.

In recent years, it has become clear that in order for a country to be truly prosperous, its citizens need many things including food, water and electricity (and usually in that order).

It is also obvious that an increase in the consumption of electricity will dramatically increase the production of CO2 emissions into our atmosphere which is bad for environmental preservation (at least in theory).

So how can we achieve a good standard of living with sustainable growth? The answer lies in solar energy; one researcher believes

Photovoltaic cells and their applications in everyday life

3 example of Photovoltaic cells and their applications in everyday life: 1. In spacecrafts 2. On satellites 3. In houses

1. Photovoltaic cells and their applications in spacecrafts.

Photovoltaic cells are used in spacecrafts to generate electricity, it uses solar energy instead of chemical thrusters. It is generally used for orbiting satellites and space probes.

They are the most important source of power in satellites

Photovoltaic cells on spacecrafts can be used to produce electricity for the spacecraft’s systems.

Power on the satellite can be generated by solar panels called photovoltaic arrays, which convert sunlight into electricity.

The power can be used to compensate for the energy loss caused by some components such as the instruments’ electronic devices.

A photovoltaic array on a satellite is a large surface, typically several meters across, covered with many solar cells or thin-film photovoltaic modules.

2. Photovoltaic cells and their applications On satellites.

Satellites generally use photovoltaic cells to generate electricity for its systems.

Spacecrafts are expensive and they need large amounts of power to operate, so the photovoltaic cells on satellites are generally used to power spacecrafts systems.

Photovoltaic cells are widely used in satellites because they offer a viable alternative to traditional forms of electrical generation such as chemical thrusters which is very inefficient and costly.

These conventional methods take time to be activated and stopped thus adding unwanted weight and complexity to the satellite.

Photovoltaic cells are compact, less complex than traditional solar panels, but most importantly can provide supplemental or even primary power for many low energy applications using small commercial space qualified PV modules that can work well in this environment while being maintenance free for long periods of time.

In fact recent advances with large format thin-film PV arrays integrated onto rigid structures have opened up new possibilities for space panels.

3. Photovoltaic cells and their applications on houses.

Photovoltaic Cells can be used to produce electricity in houses, you can have a solar panel mounted on your roof or even all around the house’s wall to collect sunlight during the day.

The photovoltaic cells generate direct current (DC) which is then converted into alternating current (AC).

We use this AC power to run most of our electrical devices such as televisions, computers, refrigerators, etc.

A typical photovoltaic cells is connected in series with an inverter or regulator circuits to keep the voltage at safe levels and match it with the load requirements.

This allows us to take advantage of renewable energy sources like the sun to reduce the consumption of natural resources (what they call sustainable growth).

PV-powered homes are being built in many locations, with a growing number of people having PV systems on their houses or as part of an off-the-grid system for homes.

The first solar powered home was constructed by Suntrix Systems Ltd in Australia.

Their 3 kW rooftop system feeds more than 10 times the electrical demand of this average two bedroom house, and at peak hours it sends excess back to the grid.

4 example of benefits that can be obtained from using photovoltaic cells

1. Environmentally friendly

There is no pollution generated by the photovoltaic cells, unlike chemical fuel or nuclear power, it does not produce any harmful waste or emissions, and it does not require any fuel to operate.

2. Less pollution into our atmosphere

The photovoltaic cells generate electricity directly from sunlight or light sources and therefore do not depend on the natural gas or coal like hydroelectric dams or nuclear power do.

3. Less dependence on fossil fuels

By using a solar panel and producing our own electricity from renewable energy sources we are reducing the need to import fossil fuels or buy more electricity from the power companies.

4. Long life cycle and maintenance free for long periods of time

The photovoltaic cells are generally designed to last for 30 or more years, and if properly maintained they will keep generating electricity without any failure for a long time.

Some companies offer maintenance plans for solar panels which extends their lifetime up to 20 years.

5. Sunlight is free and abundant on our planet

Solar energy comes from the sun which is a reliable and renewable source of energy, it does not depend on fossil fuels to operate or produce pollution.

Why do some countries use more than others?

Its because those countries that are poor, but rich on coal, cannot afford expensive technology like photovoltaic cells, so they rely on cheap methods such as oil, coal or nuclear power that can do more harm than good.

There are many rich countries that use photovoltaic cells to produce electricity and reduce their dependence on fossil fuels, which are not only expensive but also polluting the environment.

Some countries such as Germany have been using renewable energy for more than 20 years, and they are one of the biggest users in the world.

Others such as Japan which have advanced technology and much higher incomes use more than 11 terawatt-hours (11 trillion watt hours) per year.

The reason why can be found in their governments and the population; some governments have implemented strict programs to require companies and residents to use solar energy, and many people are willing to buy photovoltaic cells.

In developing countries such as India, China is planning on building more than 20% of its new generating capacity from renewable sources by 2020.

They also plan on getting 30% of their electricity generation from non-hydroelectric renewables by 2030, which means a total of 1/5 of their projected power should come from solar energy systems or wind farms.

China is also going to invest $156 billion in renewable energy over the next decade, including $70 billion for projects abroad (“Once burned, twice shy”, 2011).

Solar companies are only expected to profit by 40% in 2011, which means that most solar panels will be sold by subsidizing their prices.

However when the prices of photovoltaic cells declines it is the companies who come in last place that suffer the most and many have been forced out of business (“Once burned, twice shy”, 2011).

The future of the photovoltaic industry

The future of the photovoltaic industry is promising, with its increasing use in countries around the world, it can generate large amounts of electricity without any pollution, but it does not come without any disadvantages.

If the sun is not shinning, or if there are gray clouds in the sky we cannot use solar energy.

Though they can be used effectively even on cloudy days when there is a lot of sunlight (clouds have many layers and let through some light rays).

What to Take Away?

Photovoltaic solar technology has been around for decades, and is a renewable resource that can be used to power anything from homes to cars.

It’s also the most popular form of solar energy in the world today, with more than half of all photovoltaic devices found in either panels or cells.

There are two main types – amorphous silicon (a-Si) and crystalline silicon – but regardless which you choose to utilize as your primary source of electricity production, just know that it’s good for both our planet and your wallet!