How does a photovoltaic plant work?

The photoelectric effect, or the production of electrical energy from light, is the key to this type of energy installation. They are the ideal solution for isolated areas of the planet: they are modular in size and have a low-cost maintenance. In addition, as they operate from a renewable source, they reduce atmospheric pollution. In the following post we will learn about the main components of a photovoltaic solar plant and how it produces energy.

The interest and importance of the sun in our lives has always been present. As early as Egypt and ancient Greece, concave mirrors were used to concentrate the sun’s rays and harness sunlight for domestic use. The Romans were the first to realize that by installing glass in their windows they could heat their homes. They also discovered the greenhouse effect, building glass houses to grow crops inside.

Today, it is also the case that the demand for energy is growing all the time. According to the Electricity Market Report (IEA), global demand will grow by 3 % in 2021. Renewables are expected to increase by 6 %. Therefore, we need to use less polluting energy sources that favour the persistence of our ecosystem and reduce CO₂ emissions into the atmosphere. And, what better alternative than solar energy?

Today we focus on photovoltaic solar energy. Knowing how it works and its main components will help us to better understand this type of technology.

“Photovoltaic cells -present in photovoltaic panels- produce a photoelectric effect, i.e., they absorb light particles and generate electricity.

Photovoltaic panels:

In these installations, everything starts with the photovoltaic panels, which consist of photovoltaic cells that produce a photoelectric effect, i.e., they absorb light particles, or photons, from solar radiation (light), and expel electrons, thus generating direct current (electricity).

There are several types of photovoltaic panels or structures: fixed; mobile (solar trackers that, as their name suggests, track the sun); and floating, those that we see on water in reservoirs or lakes. The mobile ones can also be bifacial, as they collect energy at the front and at the back, thus increasing their efficiency by up to 30 %.

Direct current boxes:

The transport of the energy produced to our homes goes, first, through a system of cables and the DC boxes.

Inverter:

A key point of this type of installation are the inverters, which are responsible for transforming direct current into alternating current. Together with the inverters, step-up transformers or step-up transformers are installed, which are responsible for raising the voltage from low to medium voltage.

Medium voltage evacuation line:

Once the voltage in the step-up transformers is raised, the electrical current is transported by an underground or overhead cable to the step-up substation.

Substation:

Through an underground line, the power arrives at a substation, where the control building and the main transformer are located, which raises the voltage again, from medium to high voltage.

Evacuation and transmission lines:

Finally, a high-voltage line dumps all the energy into the power grid, and from there, it reaches our homes.

Weather stations:

It makes sense that, being plants that are fed by a natural resource, they should have this type of facility to analyse temperature, humidity or wind direction, and thus optimise their operation.

“Photovoltaic plants respond to energy demand and the scarcity of energy resources in isolated rural areas.

So why is photovoltaic technology so widespread and what are its advantages? Apart from being a renewable energy, whose source is inexhaustible and non-polluting, it responds to the energy demand and the scarcity of energy resources in isolated rural areas and is modular in size. In addition, it requires low economic and human maintenance costs. Although it is true that the costs of photovoltaic modules and those associated with them have been rising steadily over the last year, which could cause some delays in the implementation of projects.

And if we compare it with solar thermal energy, what are the differences between them? Well, mainly their management capacity and their adaptation to energy demand. Unlike photovoltaic plants, solar thermal plants are dispatchable, i.e. they can adapt energy production to demand. In addition, they can be hybridised with fossil fuel plants to reduce their emissions into the atmosphere. However, solar thermal plants require a large investment of human and economic capital, which favours the socio-economic and technological development of the areas where they are installed. If you want to know more details about how a solar thermal plant works, visit our post “How does a solar thermal parabolic trough collector plant work?”

In any case, and despite the current circumstances arising from the pandemic caused by COVID-19, photovoltaic solar energy continues to be the sustainable energy solution that breaks records in terms of installed capacity in the last year and accumulated installed capacity, as shown by the data in the latest report from the International Energy Agency. In the ranking by country, China continues to lead, followed by the European Union and the United States.

Rocío Castro Moreno, Communication Department of Abengoa.