What is solar energy?

Solar energy

Solar energy, one of the main sources of renewable energy, plays a key role in the transition toward cleaner economies that protect the environment, improve people’s well-being, and ensure the sustainability of companies.

At a time when caring for our planet and the environment is a priority, it is important to know what exactly solar energy is, how it works, and how to extend its use as a source of electricity generation.

Solar energy is harnessed from the sun in the form of electromagnetic radiation (light, heat, and ultraviolet rays). By installing solar panels or collectors, it can be used to capture thermal energy (photothermal) or to generate electricity (photovoltaic).

Technological breakthroughs have transformed solar energy into one of the most efficient and affordable in the renewable sector. This unlimited energy source, in addition to contributing to the sustainability of the planet attracts investment, generates employment, and increases the competitiveness of companies.

What types of solar energy are there?

The classification of solar energy into different types is distinguished, firstly, between active solar energy and passive solar energy, depending on whether the energy captured from the sun requires transformation into another type of energy or not. 

Solar panels on a Repsol service station

Photovoltaic solar energy

A photovoltaic system is an installation that produces electrical energy using photovoltaic modules, capable of transforming solar radiation directly into electrical energy. Solar panels contain photovoltaic cells that when they receive direct light, ionize, and release electrons that interact with each other and generate electrical current.

Solar panels on a house

Solar thermal energy

Solar thermal energy uses collectors (thermal solar panels) to transform solar radiation into heat. These collectors collect and store solar radiation to heat water that is later used to for heating or hot water systems for hygiene, residential or industrial use.

The energy that is generated through this process can also be used to produce electricity, using the heat to boil water that produces steam and turn, for example, the turbines of a generator.

A house

Passive solar energy

With regards to passive solar energy, an energy transformation is not required as it uses techniques such as bioclimatic architecture, based on the location and materials used in the construction of a property, to acheive cooling and lighting of the house. In other words, while active solar energy requieres additional equipment and a process to convert the captured energy (into electricity, in the case of photovoltaics, and into heat, in the case of thermal), passive solar energy is harnessed directly.

How do the installations work to obtain active solar energy?

Solar energy requires an energy transformation of the sun's heat or radiation into thermal or electrical energy. 

  • Photovoltaic solar energy: This occurs when photons that travel through sunlight collide with the solar panel cells and produce electrons. The electrons move by exchanging positions and creating an electricity flow between the layers of the solar panel. The more intense the light, the greater the electricity flow. More information on our page about how solar panels work.
  • Thermal solar energy: The workings of thermal solar energy is relatively simple, consisting of a system for collecting solar energy (solar collector), a device for storing the energy obtained (collection vessel), and lastly, a way of distributing the carrier fluid for consumption.
How can solar energy be used and applied?


Technological innovation in the field of renewable energies has allowed solar energy to be applied in multiple areas:

  • Electricity: installing photovoltaic panels to produce electrical energy is the most widespread use of solar energy. 
  • Heating: through the use of solar thermal panels, solar radiation can be used to heat the water that powers the radiators and underfloor heating of people’s homes. 
  • Hot water: solar thermal energy in homes is a really interesting alternative for producing hot water for sanitary use due to its efficiency and sustainability. 
  • Irrigation: generating electrical energy for agricultural irrigation is one of the many different uses of solar panels. The main advantage of this system is that the season with the highest demand for water in this area usually coincides with the season with the highest solar radiation. 
  • Lighting: photovoltaic solar energy allows for the automation of street lighting, which is an interesting energy saving and a firm commitment to renewable energy sources.
Solar panels in a field

How is Repsol involved in solar energy?

Repsol’s is committed to being a sustainable and responsible company that responds to society’s demands. That’s why we have been the first energy company to commit to reaching net-zero emissions by 2050. In line with these objectives, we have developed several projects in the field of solar energy.

Solar panels in a field

Solar farms: Valdesolar, Sigma, and Kappa

We have three three solar farms in Badajoz, Cádiz, and Ciudad Real, highly favorable areas for producing this type of energy, with a capacity equivalent of the consumption of more than 860,000 homes.

The Valdesolar project, in Bajadoz, will be the largest solar park developed by Repsol with an installed capacity of 264 MW to produce 514,490 megawatt-hours (MWh) per year, which will supply electricity to some 140,000 homes. In addition, it will prevent the emission of more than 211,000 tonnes of CO2 per year.

Kappa, the group’s first solar park, will have an installed capacity of 126.6 megawatts (MW) and will supply electricity to some 71,000 people. It is also expected to help reduce the emission of about 250,000 tonnes of CO2 per year into the atmosphere.

With regards to Sigma, the project is located in the province of Cádiz and has an installed capacity of 204 MW.

Solar panels on the roof of a house

Solar panels on a roof of a single-family house

Repsol Solify is the new comprehensive self-generation solution for photovoltaic energy aimed at individual customers and businesses that offers 100% renewable energy. This turnkey product includes everything from managing the installation licenses, assembling the solar panels, and remotely monitoring installation to ensure they are in good condition.

A man reading a newspaper on a balcony

Solar communities

Repsol Solmatch is the first big Solar Community in Spain. This commitment to distributed, or decentralized generation, is based on the activation of solar communities.

How do they work? Panels are installed on homeowners' roofs for free so that households located within 500 meters can enjoy 100% renewable energy.

Repsol service station with solar panels on the roof

Self-consumption solar panels

We are committed to solar panels for the energy self-consumption of our facilities. We install them in our network of service stations. Thanks to this project, we reaffirm our commitment to sustainability by promoting the use of renewable energies and caring for the environment.

Renewable energy generation certification logo

Guaranteeing the 100% renewable origin of the electricity we offer with the highest certification

The Spanish National Commission on Markets and Competition (CNMC) awarded us the highest certification – the A label – for the environmentally-friendly origin of the electricity we offer. This makes us the only major retailer, in terms of customers supplied, to be awarded this label for the second year in a row.

Ilustración de una ciudad

Everything you should know about solar energy

Get all your questions answered about this economical and endless renewable energy.