Solar Panels: price, specs, what to know about solar energy

A beginner's guide to solar energy
Ameya Paleja
Photovoltaic power generation
Photovoltaic power generation

yangna/iStock 

As the world strives to reduce its dependence on fossil fuels and move toward more sustainable forms of energy, solar energy is something everybody wants to tap into. A perennial energy source, sunlight is available in most parts of the world for significant periods of time in the day.

To harvest this energy, though, one needs specialized equipment, and solar panels are the most commonly used method. If you do not know how they work, what they are made from, or how much energy they can generate, here's a basic guide to getting you started.

What are solar panels?

Solar panels are devices that convert light into electricity. They are called solar panels because, on most occasions, the light from the Sun, or Sol as astronomers like to call it, is the most abundant form of light and easily accessible, too.

A solar panel consists of a particular layer of silicon cells, a metal frame in a glass casing that has a special film around it, and connections that link the components to each other, making an array. Smaller units inside a panel are called solar or photovoltaic cells, each capable of converting light into electricity.

When arranged on a panel, solar cells can harvest more light being incident in the area and convert it into electricity. This is why one often sees spacecraft equipped with large solar panels designed to cater to the electrical power needs of the space vehicle.

History of solar panels

Solar panels might be common today, but their history can be traced back more than 100 years. Before this, energy from the Sun was being accessed to heat water and turn it into steam to drive machinery.

However, French scientist Edmund Becquerel observed the photovoltaic effect (the generation of voltage and electric current in a material exposed to light). Through experiments with electrolytic cells, he established that the electricity flowing between two platinum electrodes coated in silver chloride or silver bromide is slightly stronger in daylight than in the dark. At the young age of 19 created the first photovoltaic cell that could convert light into electricity.

In 1883, Charles Fritts created the first solar cell using the semiconductor selenium, coating it with an extremely thin layer of gold. Fritts' panel was also installed on a rooftop in New York, but its high cost and one percent energy conversion efficiency made it unviable in the long run.

Russell Ohl first patented solar cells made with silicon, and the first solar panel using silicon cells was created in 1954. These panels were primarily meant to produce power for spacecraft but also found their application in calculators by the 1970s.

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How do solar panels convert light into electricity?

A solar panel consists of a large array of solar cells connected. Solar cells are usually made from silicon, the second most abundant material on the planet after oxygen. Since silicon is a semiconductor, it can act as an insulator and a conductor.

Inside a solar cell, silicon is arranged into two different layers: the P-type, which can receive electrons, and the N-type, which can give electrons away. The p-type silicon is produced by adding atoms—such as boron or gallium—that have one less electron in their outer energy level than the silicon, creating a vacancy. The n-type silicon is made by including atoms, such as phosphorus, that have one more electron in their outer level than silicon.

The N-type layer is placed to face the sunlight, while the P-type is placed underneath the N-type layer.

Solar Panels: price, specs, what to know about solar energy
How solar cells work

The light from the Sun comes in small packets of energy called photons that can cause the N-type layer to lose electrons. These are collected on an aluminum layer underneath, also known as the back sheet. Theoducinghe electrons flow back and forth, this produces an electric current, which can flow down wires and out of the solar cell to a storage device.

What is the efficiency of a solar panel?

The efficiency of a solar panel is the amount of electricity it can produce from the light incident on its surface. Solar panel efficiency is determined under Standard Test Conditions (STC) where the temperature is 25 degrees Celsius and irradiance is 1000 W/ square meter. This is the equivalent of sunlight received on a bright sunny day by a tilted solar panel. An efficiency of 20 percent would mean that a one-square-meter solar panel will produce 200 Watts of electricity.

In the real world, the conditions are impacted by a host of factors such as wind, humidity, UV radiation, chemical exposure, etc., and the actual efficiency of the panel is lower than that obtained during the STC. The material used to make the solar cell can also increase energy conversion efficiency, with monocrystalline solar panels delivering the highest efficiency among commercially available panels.

Behind the business scenes, scientists have been looking to increase the efficiency of solar panels and, in recent times, have managed to crack the 30 percent barrier of solar efficiency. This has been made possible with the use of perovskites, calcium titanate crystals, or materials with similar structural arrangements and properties that can be used to enhance the efficiency of solar cells.

Advantages of solar panels

The most significant advantage of using solar panels is the ability to tap into an unlimited, non-polluting, renewable energy source. As we improve our methods to harvest the energy that is incident on our planet every single day, we will be able to transition to a clean energy source for all our future needs.

Unlike conventional source of power that requires one to be connected to the grid to receive an uninterrupted supply, by using batteries, solar panels can give us the freedom to stay in far-off places and still have easy access to energy. It is hardly a surprise that scientists turned to solar energy to power spacecraft that have traveled to Mars and even beyond instead of relying on nuclear energy.

Once installed, solar panels have long lifetimes with very little maintenance needed. Solar panels need to be kept clean for the highest energy conversion efficiency, but other than that require no maintenance since there are no moving parts in the energy generation process. The energy storage end requires maintenance, but the system usually does more than pay for itself in the years of service.

Users in many places can also sell excess energy generated by the panels to utility companies and earn money for doing virtually nothing once the installation is completed.

Disadvantages of solar panels

Harvesting solar energy is not straightforward, though. While the cost of generating solar power has reduced considerably over the past few years, the upfront cost of installing a solar panel, especially on a small scale, is still reasonably high. Apart from buying the panels, one also needs to purchase the inverter and energy storage solution, which can be pretty expensive.

Harvesting solar energy is also heavily dependent on weather conditions. Even though the panels work under cloudy conditions, a few days of rainy or snowy weather can impact your energy reserves. For those who need to heat water during the night in the winter, a solar panel might not meet the need.

Conventionally, solar panels occupy a lot of space and depending on the size of your house and energy needs, you might need to figure out some extra real estate where they can be installed. The efficiency of home solar panels also depends on the type of roof and the direction it faces. With advances in technology, it may be possible to buy transparent solar windows. But if you want to buy something now, these might not deliver the energy conversion efficiencies you would expect from them.

Installation of solar panels in large numbers to make solar farms has been associated with soil compaction and increased erosion. Post their lifetime, solar panels have become a concern since they are yet to find their way into the recycling economy, and dumping them in landfills can leach heavy metals such as lead and cadmium into the soil.

Innovation in the solar energy sector is taking a new turn, with newer materials being used to make solar panels better and cheaper. Solar panels are set to make a significant impact on how we access energy in the future.

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