How Solar Cells Work

You've probably seen calculators with solar cells -- devices that never need batteries and in some cases, don't even have an off button. As long as there's enough light, they seem to work forever. You may also have seen larger solar panels, perhaps on emergency road signs, call boxes, buoys and even in parking lots to power the lights.

Although these larger panels aren't as common as solar-powered calculators, they're out there and not that hard to spot if you know where to look. In fact, photovoltaics -- which were once used almost exclusively in space, powering satellites' electrical systems as far back as 1958 -- are being used more and more in less exotic ways. The technology continues to pop up in new devices all the time, from sunglasses to electric vehicle charging stations.

The hope for a "solar revolution" has been floating around for decades -- the idea that one day we'll all use free electricity fro m the sun. This is a seductive promise, because on a bright, sunny day, the sun's rays give off approximately 1,000 watts of energy per square meter of the planet's surface. If we could collect all of that energy, we could easily power our homes and offices for free.

What hinders solar energy?

ACCORDING to Director General, Board of Investment a solar energy policy would soon be announced hoping that it would open doors for huge investment and lucrative returns in the country. Addressing the office-bearers of the Korangi Association of Trade and Industry he said investors would be encouraged to invest in solar energy plants up to 10 megawatts under the new policy.

The statement of the official indicates that at long last the Government has realised the potential of the solar energy and steps are being contemplated for development and application of this endless source of energy. Pakistan these days is not only facing energy shortage but also the rates of electricity are soaring every now and then making it extremely difficult for a common citizen to pay off monthly electricity bills. As there seems to be no respite in foreseeable future the problems of the consumers can be mitigated by resorting to other methods of generating electricity, solar being one of them. Most of the countries are doing it successfully for decades and their population is benefiting through the use of this free and environment friendly resource. In Pakistan too, some villages have been electrified through solar energy and their inhabitants are not only getting light but also powering fans. Similarly, some companies have introduced solar heaters and geysers but all these experiments are limited to pilot stages and no worthwhile plan has so far been initiated to take advantage of this massive source of energy on the commercial scale. This is despite the fact that we have an Alternative Energy Development Board and a number of countries and companies are keen to invest in the field. We would, therefore, urge the Government not to indulge in rhetoric and take practical measures for development of solar technology in the country, which can help overcome our energy woes to a great extent. Solar power can take care of household energy requirements and the energy so saved could be used for commercial and industrial purposes.

Solar Energy Technologies

The Solar Energy Technologies Program focuses on developing cost-effective solar energy technologies that have the greatest potential to benefit the nation and the world. A growing solar industry also stimulates our economy by creating jobs in solar manufacturing and installation.

Photovoltaics
The Photovoltaics subprogram aggressively funds a diverse set of PV technologies that have potential in many markets that will help solar electricity achieve grid parity.

Concentrating Solar Power
The Concentrating Solar Power subprogram is making CSP competitive in the intermediate power market and developing advanced technologies that will reduce system and storage costs.

Systems Integration
The Systems Integration subprogram is breaking down the regulatory, technical, and economic barriers to integrate solar electricity into the electric grid.

Market Transformation
The Market Transformation subprogram works with external partners to address non-technical issues that are barriers to the widespread adoption of solar technologies.

Solar Energy

Solar energy is truly the new wave of the future. Though the use of solar power has been around for many years, the need and demand for it is growing steadily every day as the need for conserving the most popular energy reserves are being stressed more and more. We are simply using too much electrical energy and doing so in a way that is harming our environment. As a result, we are forcing the need to seek out alternative, non-harmful means of energy, thus, the increase in solar energy use and technological advancements of it.

Solar energy is becoming more popular being used in everything from watches to building infrastructures. Solar energy is even being used to fuel automobiles and will most assuredly be a large part of the energy we will use going into the future. There are many advancements currently being made on the solar energy technology that is already working, advancements that will allow solar driven technologies to run even longer on solar energy than ever before.

The direction of solar energy is a positive one. And, though much of the technology behind it is still very expensive for the average person to buy, as advancements are made, the price will become more affordable. We will be able to save our environment. We will be able to use the energy of the sun, effectively and efficiently. Solar energy will probably eventually make most other types of energy power obsolete. The technology will be so advanced and cost effective that one will be able to purchase solar products and save extraordinary amounts of money on gas, battery replacements, etc. And, our environment will be the better for it to. There will be less toxic emissions being emitted into the air. There will be less waste dumped into our landfills.

The study and science promoting solar energy needs to be supported by the public. We need the important advancements provided by solar studies in order to be able to save our world, our only planet. The sun can naturally and harmlessly support our needs, but we just need to have the opportunity to make the necessary advancements so that it can.

How can you help? Contribute to solar energy causes. Purchase solar energy products that are already on the market. Speak to others about the importance of using solar energy. Have solar energy products installed in the new businesses you build. Be an advocate. Be a supporter. Do what you can to help save this world. Everything you can do does make a difference. It will save our world.

Pakistan is most suitable for solar power:

As solar power does not make sense for all locations in the world. The initial cost of installing solar panels or other sources of solar energy is high, and that is not easy for most people to get around. No matter how much some people would like to get involved in the movement to independent energy, it is cost prohibitive.To achieve the highest level of efficiency, which is the entire point of going solar in the first place, you need the proper amount of roof space to support the panels your house may require. Not only how much space is available, but also the location of your home is also relevant to whether or not you can maintain solar energy. Some houses simply do not receive enough sunlight to produce substantial energy. This could mean that either your house is not positioned favorably in relation to a tree or other house.
As you can see, the cons of implementing solar power in your home are primarily cost and location related, but if those two items do not pose issues for you, the good news is…

If solar power is looked at through a long-term lens, you will eventually make back what you originally spent, and possibly start saving money on your investment

Let’s not forget that solar energy increases the value of your home too. Solar power is not subject supply and demand fluctuations in the way that gas is. Silicon, the primary component of solar panels, is also being more widely produced, therefore, less and less expensive with each passing year.

Solar power is independent, or semi-independent. This is great because you can supply your home with electricity during a power outage. Solar power can also be used in remote locations, places where conventional power can’t be reached. On a larger scale, solar power also reduces our need to rely on foreign sources for power.

And last, but certainly not least, it’s good for our planet! Solar energy is clean, renewable and sustainable. It does not fill our atmosphere with carbon dioxide, nitrogen oxide, mercury or any other pollutants. It is a free and unlimited source of power, unlike expensive and damaging fossil fuels.

Solar cell applications

Applications for solar cells are varied, but often involve instances where normal power sources are not available, for example in space probes. More prosaically, they are also used in calculators and wrist watches.

When used in combination - solar modules, or photovoltaic arrays - they can help provide alternative power sources in combination with the electricity grid.

Solar Cell history
The photovoltaic effect was first discovered by Edmond Becquerel in 1839, and the likes of Albert Einstein continued his work. In 1921 Einstein was awarded the Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect".

The first silicon p-n junction (a combination of N-type and P-type semiconductors) solar cell was made at Bell Labs in 1954, with solar cells first being used to power satellites, such as the Vanguard I, in 1958.


In the following, we bring together resources from Electronics Weekly and UK and EU governmental bodies to provide detailed reference information about solar cells.

Manufacturing solar cells

In general, solar cells are made from thin flat layers of semiconductor that include a p-n junction across the whole area of the cell.

A photon hitting the structure creates an electron-hole carrier pair (an exciton) which is separated by the junction. This develops a potential difference between the front and the back of the cell which can produce a current externally.

There is a relationship between the energy in the photon and the bandgap of the structure which governs the success rate of photon to exciton conversion.
Essentially: a particular semiconductor will only efficiently convert one colour of light - or more accurately, light between two wavelengths with sensitivity peaking somewhere near the middle.

For example, 'single junction' silicon solar cells can only absorb the near-infra red part of the sun's spectrum and have a light to electricity conversion efficiency somewhere around 20 per cent.
GaAs and other compound semiconductors can be used to form junctions with other bandgaps, and these junctions can be stacked to harvest a broader range of wavelengths - or photon energies - depending on whether you are thinking classically or in quantum terms.

Providing they are stacked in the right order so the top layers pass unused light through to lower layers, efficiencies of around 40 per cent can be achieved. The current record is almost 50 per cent.

Double and triple junction cells very expensive, and are found on satellites and transcontinental solar racing cars.

Single crystal junctions achieve the efficiencies mentioned above, but are not the cheapest way to produce solar cells.

Amorphous silicon deposited on glass offers around six per cent efficiency at far lower cost than single crystal silicon, and is frequently seen on solar-powered calculators.
Polysilicon on glass is between amorphous and single crystal silicon in both cost and efficiency.

It is widely believed that, depending on latitude, a minimum efficiency of 10 per cent is required to make cost-effective large-scale solar power installations - and the raw materials will have to be cheap.

Researchers are looking at alternative materials to achieve these aims.

For example: single crystal solar cells are made from IC-grade silicon wafers, whereas less pure silicon could be used with negligible loss in efficiency.

The question of whether an industry will form to produce these less pure wafers remains to be answered.

Organic semiconductors can be used to make solar cells, dopes with materials including carbon nanotubes.

Currently efficiency is a few per cent at most and the cells degrade rapidly in sunlight, but some predict organic solar technology will be the one to take off. In the mean time, these cells are likely to develop enough to be used in solar-powered portable electronics.

Out in the far field are solar cells based on structures that mimic photosynthesis, and various liquid and solid bulk technologies, such as the dye-sensitised solar cells in which the excitons form in dye; titanium dioxide pulls away the electrons; and an electrolyte takes away the holes.

With some forms of organic solar cell, as well as solid dye-sensitised cells, it may be possible to make large areas very cheaply on printing presses.

As the manufacture of nano-scale material powders becomes possible, researchers are not only reviewing existing solar cell types, but looking at schemes in which the light is absorbed by particles of similar size to its wavelength.