How Does Solar Power Create Electricity?

Harnessing solar power is something humankind has been doing for centuries. From the ancient sundials that helped people keep track of time to today’s modern photovoltaic technologies.

Solar energy is a renewable energy resource that is more affordable now than ever before and is used to produce electricity for a wide variety of residential and commercial uses. Electricity produced from sunlight will be a key part of our journey toward sustainable energy in the future.

Using solar power to generate electricity at home is a very appealing option for a number of reasons: not only would you be reducing your overall environmental footprint and greenhouse gas emissions, but you would be reducing your bills and could even generate some income by selling back excess energy into the grid.

It is therefore a no-brainer that in the European Union a target has been set to encourage EU countries to roll out renewable sources of energy such as solar power in order to achieve the overarching target of at least 32 percent by 2030.

How can solar energy be used to produce electricity?

Human ingenuity has developed two different ways how to harvest the energy of the sun and turn it into electricity:

Solar thermal systems and Solar photovoltaic systems

A solar thermal system generates electricity indirectly by capturing the heat of the sun to produce steam, which runs a turbine that produces electricity.

A solar photovoltaic system produces electricity directly from the sun’s light through a series of physical and chemical reactions known as the photovoltaic effect.

Let’s examine each of these systems in more detail.

How does solar thermal generate electricity?

You might be familiar with solar thermal technology from a widely publicized series of photos that debuted in the press in 2013, featuring the Ivanpah Solar Power Facility in the Mojave Desert, California. At the time, it was the largest solar power plant in the world. The array of 170,000 heliostats, which look like large mirrors are tracking the sun’s movement across the sky to power over 140,000 households [1].

Mirrors are one of the main components of the solar thermal system. They reflect sunlight onto a receiver containing a heat-transfer fluid, which is warmed up by the sun. The fluid used for this purpose is often molten salt, which is a mixture of 60 percent sodium nitrate and 40 percent potassium nitrate.

Molten salt has a great capacity to store and transfer heat [2]. This allows the storage of the heat generated from the sun for periods of time with no sunlight.

For example, Gemasolar power plant in Spain can store enough heat to produce electricity for an extra 15 hours with no solar input [3].  

The rest of electricity generation process is much the same as it is at coal-fueled power plants. The heat transferred by molten salt creates steam that runs steam turbines, which power a generator that produces electricity.

How do photovoltaic solar panels generate electricity?

The energy of collected sunlight is transformed directly into electricity thanks to the photovoltaic effect. In short, this effect takes place when photons (tiny electromagnetic particles) of light are absorbed by a specific material, which in turn releases electrons from atoms. Released electrons are then available to do the electrical work, such as powering a light bulb.

Although we cannot see the photovoltaic effect with our own eyes, we can look more closely at the solar panels where this process takes place.

What are photovoltaic solar panels?

Solar panels have become a familiar sight to many of us. Other than the classic, dark blue panels, scientists have also been working in the past years on diverse alternatives such as producing more aesthetically pleasing green-colored panels or cyanobacteria-powered bio-panels. But no matter how they look, solar panels serve as devices for capturing the energy of light.

One solar panel consists of many smaller units called photovoltaic cells. Inside these cells, the photovoltaic effect takes place. On average, one cell produces around 0.5 volts. Multiple cells are wired together in series to increase their output.

Solar cells are made of a semiconducting material, such as silicon, placed between two conducting materials to establish an electric field. Commercially available cells contain phosphorus to provide negative electric charge and boron for the positive charge.

The electric field pushes electrons knocked by photons out of the silicon layer to metal plates on the sides of the cells, where they are transferred in a form of direct current [4].

One of the biggest disadvantages of photovoltaic systems is the conversion rate of the sunlight into electricity, otherwise referred to as the efficiency. At most installations, this number remains between 15 and 18 percent. This means that over 80 percent of the sunlight falling on the solar panel is not transformed into power.

Where does the electricity go next?

When the solar energy is captured and collected by the solar cells, it is converted into direct current. The current flows into an inverter, a device that transforms the direct current into alternating current, which is used to power our electronic devices [5].

For any extra solar-generated electricity that is not used right away, there are two primary options and one hybrid option of their utilization. These are:

• On-grid systems

On-grid systems feed electricity back into the electrical grid. Electricity companies typically give customers credits for any extra electricity that is fed back into the grid from their solar panels. You can use these credits to draw electricity from the grid on days when your solar array doesn’t produce any. One drawback to this type of solar system is that when the grid is down, the system might not be utilized.

• Off-grid systems

Off-grid systems are standalone solar systems that rely on batteries to store solar energy for use during the night and at other times when more electricity is needed than is generated by the solar system.

• On-grid solar systems with a battery backup

On-grid solar systems with a battery backup feed solar energy-generated electricity back into the grid when the grid is operating, but in the event of a grid blackout, these systems will switch to an off-grid mode. In this off-grid mode, the backup battery is used to supply stored solar power, and the solar panels charge the battery [6].

How can you generate solar electricity at home?

If you are looking into options for making your house more eco-friendly and saving some money, solar power is probably one of the most attractive renewable energy options. In fact, solar power is becoming the cheapest way to generate electricity, according to Bloomberg New Energy Finance analysts.

The cost of solar has fallen to about a third of levels in 2010, even among some of the poorest countries [7]. Solar panels are also relatively compact and can be placed on rooftops, balconies or different places on your property.

So can you generate solar electricity at home? The simple answer is yes, you can. Indeed, there is a term for generating power at home: it is called micro-generation and refers to the stand-alone generation of low carbon heat and/or electricity which is feasible for the average home [8].

How to do it is a fairly straightforward question too: by installing a set of photovoltaics. Having said that, while going off the grid entirely may be difficult for many homeowners, generating a portion of a home’s electrical needs is definitely possible with solar power.

The extent to which solar power generation is an attractive option for your own houseful will be largely determined by the following factors:

• the availability of the key resource – the sun
• space for the solar system size you need to power your household’s energy needs
• the level of cost and investment involved
• the local permits required

These are important considerations you will need to take into account and look into before planning to invest in a solar power system.

How much energy do solar panels produce?

In terms of how much energy you will be able to generate, this largely depends on the availability of the sun. Solar photovoltaic panels use the sun’s energy to create electricity to run appliances and lighting.

This doesn’t mean that it needs to be sunny all the time for power to be generated, as the technology relies simply on daylight.

How to get the best energy output from your solar panels?

Solar cells, which are usually placed on the roof, are made up of layers of semi conducting material which create an electric field, when the sun shines on them, causing electricity to flow. The stronger the sun, the more electricity is produced [8].

But how much power you will generate will also depend on where the solar panels or tiles are placed. Roofs are an option that is preferred by a number of people, but to maximize energy there needs to be no shade on the panels, especially during the prime sunlight hours of 9 a.m. to 3 p.m.

If you are able to install your solar system to face the South this will provided an optimum potential for energy generation. This is very important as even if just one of a solar panel’s 36 cells is shaded, power production will be reduced. With today’s modern technology, solar panels are light and solar tiles, in particular, can replace traditional roof tiles.

Most photovoltaic units installed in homes are linked to the utility grid. This allows for the power collected through the solar powers to be fed directly into the utility power distribution system of the house or building. In this way, the solar energy system installed reduces demand for power from the utility when the solar array is generating electricity – thus lowering the utility bill. These types of solar energy systems are also known as “on grid” or “battery-less” and they make up approximately 98 percent of the solar power systems installed today [9].

Both of these concepts show us that we are capable of satisfying our demand for electricity by harvesting power from renewable resources. The only limitations arise from the technology available at the moment. This is an issue that can be tackled over the time, especially if we focus our full attention on finding solutions to current obstacles such as the low efficiency of residential photovoltaic systems.

Who knows? Perhaps the twenty-first century will someday be known as the era of the “Renewable Energy Revolution.”

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