Photovoltaic energy, how does it work?

The emergence of renewable energy has gone hand in hand with the harnessing of the sun, but how does photovoltaic energy work and how does it reach your home?

The sun, that incandescent ball that occupies our sky and around which practically all human cultures that have ever existed have revolved, revolve, and will revolve (literally and literally). A cultural and religious veneration that, far from being banished by an increasingly less mystical humanity, is turning into scientific exploitation through energy. And the fact is that this 4.603 billion-year-old star—barely an adult compared to the age of other stars—is vital for life on Earth (we don’t think it’s necessary to explain why at this point), but also for the production of clean, sustainable, and inexhaustible energy: photovoltaics. Thus, in just a few decades, we have gone from living with our backs to the sun—from an energy perspective—to experiencing a photovoltaic fever in which we have begun to harness the potential of our sun king to generate electricity. But have you ever wondered how photovoltaic solar energy works? Well, today we’re going to enlighten you. Put on some sunscreen, we’re starting.

Perhaps the first and most necessary thing to do is to clarify what photovoltaic solar energy is. This type of energy is obtained by converting the sun’s radiation into electricity thanks to the so-called photoelectric effect; which basically consists of the emission of electrons (which will later become electricity) as a result of electromagnetic radiation striking a material, in this case the photovoltaic cells located on the surface of photovoltaic panels, regardless of their size and technology. These, in turn, have a series of layers of electrically semiconductor material, whether silicon or other materials, covered by a glassy layer that allows the passage of solar radiation and minimizes energy loss, although currently the maximum efficiency is 20% in the most advanced installations. In this way, the sun’s rays that remain inside are “trapped” within the photovoltaic panel thanks to the generation of an electrical field that runs through an electrical circuit that travels through the electrical installation.

We now have our beloved sun rays, whose intensity will determine – within the capacity limits of our installation – the power we will be able to generate, trapped in our electrical circuit thanks to the “magic” of science. Now it’s time to convert these into real electrical energy that we can use.

Well, as the “trapped” photons release electrons, they generate more and more electricity through the photovoltaic panel circuit, which cannot use all the generated electrons and redirects them back to the so-called negative panel so that they can re-enter later in the process. Thus, this cyclical process allows the production of what we know as direct current, which is stored in batteries to be later converted into alternating current (the one we consume at home) thanks to the work of the second great protagonist of our explanation: voltage inverters.

How does photovoltaic energy work?

These inverters are key, since without them it would be impossible for us to take advantage of photovoltaic solar energy. Thus, the work of these devices equals the energy current to that which we can find in any socket in a home thanks to the transition from DC to AC. The explanation for this need to invert the current is that direct current, as its name indicates, offers a regular flow that runs in a unidirectional manner, while alternating current works thanks to a power and direction that constantly changes with different intervals that form power peaks and valleys. In this way, the inverters constantly change the direction of the direct current to alternating current; thus we can take advantage of it for our domestic use, since it is much easier to adapt the specific voltage of our appliances to alternating current.

Solar energy and its global contribution

Well, it is at this moment where, to continue with the explanation, we have to stop at what types of photovoltaic installations exist. Basically, we can divide them into two large groups:

• Photovoltaic installations connected to the electrical grid
• Photovoltaic installations not connected to the electrical grid

Let’s look at the differences in operation and what other elements come into operation to guarantee their use.

Photovoltaic solar installations connected to the electrical grid

These types of installations, whether self-consumption (those we install in our private homes to supply ourselves with “free” energy) or a central installation (a large installation that generates photovoltaic solar energy and distributes it to different consumers), are interconnected with the large electrical grid; allowing it to feed on its surpluses (in the case of self-consumption) and production (in the case of power plants).

Photovoltaic solar installations not connected to the electricity grid

This second classification is the least common, but very present in worlds such as agriculture, as well as in remote or difficult-to-access places. Basically, these are installations that operate in what are known as “energy islands” to satisfy the energy demand of autonomous installations. Thus, these types of photovoltaic installations, much simpler in operation since they do not require additional switchgear as they are not connected to the main electrical grid, can act as generators of electrical energy for lighting, for irrigation systems for plantations or as support for other generation systems such as diesel generators.

To do this, and returning to the point where the energy has already passed through the solar panel and is safely stored in our battery, these installations require another additional element that differentiates them in terms of operation: the regulators. This element basically works as a protection system for the battery against electrical overloads or possible inefficient or irresponsible uses of the stored energy. In this way, the batteries, well protected, dump the energy into the autonomous electrical grid (wiring and domestic/agricultural/industrial installation) and the latter makes use of it. It’s that easy.

Photovoltaic energy: sustainable and cheap

Until very recently, the debate about photovoltaic energy, as with other renewable energy sources, was far-reaching. The clouds that threatened to cover the sunny “photovoltaic sky” were none other than doubts about its very viability as an energy source. Like any technology, photovoltaics paid the price of extra costs in its initial phase, which, after several years in which it has demonstrated its versatility, it has managed to overcome thanks to technological maturity and a sustained drop in installation prices.

Thus, just two years ago, a milestone occurred in the history of photovoltaic solar energy when the  International Energy Agency (IEA) published its 2020 annual energy report (World Energy Outlook), where it ruled that solar energy is not only competitive and efficient, but also “the cheapest electricity in history”; that’s something. The key to this is the cost of capital for solar energy projects, which allows solar energy to be produced at a price of less than $20 per megawatt hour and, for this reason, becomes one of the reasons why financing entities look favorably on the provision of capital to promote new solar projects given its high profitability.

Today, photovoltaic energy generation capacity has reached the psychological barrier of 1,000 GW thanks to the contribution of an excellent 2021 course in which 168 GW of capacity added to the global electricity grid. This is confirmed by the Global Market Outlook for Solar Power report from SolarPower Europe, which also highlights that this is the ninth consecutive year in which the photovoltaic industry has broken its annual installation record. A trend that is expected to be repeated in 2022, when forecasts point to solar energy installations exceeding 200 GW for the first time.