How solar power generation works
The sun emits a phenomenal amount of energy towards the Earth. This can be expressed in two ways: in its thermal form, or through the photovoltaic effect. Panels are used to harness one or the other, or both, as described below:
Photovoltaic solar power
Photovoltaic solar panels are designed to convert solar energy directly into electricity. Their operation is based on thephotovoltaic effect, a phenomenon discovered by physicist Alexandre Edmond Becquerel in 1839. Photovoltaic cells, generally made of silicon, are the key elements of these panels, capturing solar photons to release electrons and generate an electric current.
There are three main photovoltaic cell technologies: monocrystalline silicon, polycrystalline silicon and thin-film. Monocrystalline cells offer the highest efficiency, reaching up to 22%, while polycrystalline cells have a slightly lower efficiency, generally between 15% and 18%. Thin-film cells are less efficient, but their flexibility and low cost make them attractive for certain applications.
The development of photovoltaic solar panels has been driven by technological advances and government policies favoring renewable energies. Lower production costs and greater efficiency have made photovoltaic solar energy increasingly competitive with traditional energy sources. What’s more, innovation in materials, such as perovskite-based cells, points to even greater potential for improving the efficiency and durability of solar panels.
The solar photovoltaic market has grown rapidly in recent years, with worldwide installed capacity exceeding 700 GW by 2020. This expansion is mainly due to the development of large-scale solar power plants and the widespread adoption of photovoltaic panels on the roofs of residential and commercial buildings. Leading countries in solar photovoltaics include China, the United States, India, Japan and Germany.
It is by far the most widely used solar energy technique.
Solar thermal
Solar thermal is a technology that converts solar energy into heat, which can then be used to generate electricity or for direct thermal applications. There are two main categories of solar thermal: low-temperature solar thermal for residential and industrial applications, and high-temperature solar thermal for power generation in solar power plants.
Low-temperature solar thermal systems include solar water heaters and solar heating systems for domestic hot water and space heating. These systems use solar collectors, usually flat-plate glass collectors or evacuated tube collectors, to capture solar energy and transfer it to a heat transfer fluid. The heated water can then be stored in a hot-water tank or used directly for heating.
High-temperature solar thermal power plants generate electricity by using the sun’s heat to create steam, which drives a turbine connected to a generator. The main high-temperature solar thermal technologies are parabolic concentrator plants, solar tower plants and Fresnel linear reflector plants. These plants use mirrors to concentrate solar energy on a receiver, where the heat is transferred to a fluid, usually water, molten salt or another heat-transfer fluid.
Several countries have invested in the development of solar thermal power plants, including the USA, Spain, Morocco, South Africa and China. Notable solar thermal power plants include the Ivanpah power plant in the USA (392 MW), the Andasol power plant in Spain (150 MW), the Noor solar power plant in Morocco (580 MW planned), the KaXu solar power plant in South Africa (100 MW) and the Delingha solar power plant in China (50 MW).
In 2019, installed capacity worldwide stood at 6.2 GW, mainly in China and the USA.
Hybrid solar
Hybrid solar panels combine solar photovoltaic and solar thermal technologies in a single system, optimizing the use of solar energy. They produce both electricity and domestic hot water. Their operation is based on two key elements:
- On the one hand, photovoltaic cells capture the sun’s light energy and convert it into electricity.
- On the other, a thermal system is integrated into the panel to harness the heat produced by the photovoltaic cells. This thermal system consists of a network of tubes through which a heat-transfer fluid, usually glycol water, circulates, absorbing the heat generated by the cells and transferring it to a domestic hot water tank or heating system.
Hybrid solar panels offer several advantages:
- they make better use of space, as they combine two technologies in a single device.
- they offer greater energy efficiency, as they recover both light and heat energy from the sun, reducing energy losses and increasing overall system efficiency.
- photovoltaic cells are better cooled thanks to the integrated thermal system.
Specific solar energy applications
Solar energy has a number of specific applications, including agrivoltaics (combining agriculture and photovoltaic production), solar-powered vehicles, outdoor residential applications (solar street lamps, solar roof tiles, etc.) and, more broadly, applications for private individuals.
Agrivoltaics
Agrivoltaics is an innovative approach that combines solar energy and agriculture to optimize the use of land and resources. There are several types of agrivoltaics, such as horizontal, elevated, greenhouse-integrated, livestock and aquatic. Each of these types has its own characteristics and advantages, depending on how the solar panels are integrated into the agricultural landscape.
It reduces competition for land, improves energy efficiency and provides environmental and economic benefits. Agrivoltaic projects can be adapted to local conditions and the specific needs of agriculture, offering a sustainable solution to energy and agricultural challenges. The concept has evolved over the decades, with increasing support from governments, researchers and companies who recognize the potential benefits of this innovative approach.
Solar-powered vehicles
There are:
- Solar boats are marine vehicles powered by solar energy, offering an ecological and sustainable alternative to traditional engines. The typology of solar-powered boats varies according to size and purpose, including small craft, shuttles, touring boats, luxury yachts and research vessels. Solar panel and battery requirements depend on factors such as boat size, cruising speed, range and weather conditions, with solar panel capacities ranging from 500 W to 200 kW and batteries from 2 to 1,000 kWh.
- Thesolar airplane is an aircraft powered by electric motors driven by solar energy. It uses solar panels, usually placed on the wings and fuselage, to convert sunlight into electricity. This electricity is then stored in on-board batteries, which power the aircraft’s engines and systems. Solar-powered aircraft offer an environmentally-friendly and sustainable means of air transport, with virtually unlimited potential for autonomy, subject to favorable weather conditions and adequate energy storage capacity. However, this is not currently being realized in practice.
- The solar car is an electric vehicle equipped with integrated solar panels that convert solar energy into electricity to power the vehicle’s engine and auxiliary systems. The solar energy generated is stored in on-board batteries, which are used to power the electric motors and ensure driving autonomy. These vehicles combine the advantages of electric cars, such as zero local emissions and low running costs, with the free, renewable energy of the sun. Solar cars have the potential to reduce dependence on fossil fuels and contribute to the fight against climate change, while offering a sustainable alternative for personal and collective mobility.
Solar energy for residential applications
Outdoor residential
A number of applications integrate photovoltaic panels into outdoor elements, for both private individuals and local authorities:
- Solar street lighting involves fitting solar panels and small batteries to street lamps, to make them self-sufficient.
- Solar tiles are roofing tiles that also act as photovoltaic panels.
- Solar windows are glass surfaces incorporating photovoltaic cells to convert sunlight into electricity. They combine the transparency of a conventional window with the production of renewable energy, saving considerable space.
- For a long time, the solar road was a very attractive idea, but its implementation has largely been a failure.
Residential and consumer goods
Other innovations mainly concern private individuals. These may include innovations for the home:
- Solar cooking uses the sun’s energy to cook food without consuming fossil fuels. They come in a variety of forms, including parabolic solar ovens, solar box ovens and solar tube cookers. These devices capture and concentrate the sun’s rays to generate heat, enabling food to be cooked. Although cooking times can be longer than traditional methods, solar cooking is ecological, economical and sustainable. It offers an interesting alternative for reducing our carbon footprint and conserving energy resources.
- Solar water heaters produce domestic hot water using the sun’s energy. They are made up of solar thermal collectors that capture the heat, a hot-water tank to store the heated water, and a circulation system, often a heat-transfer fluid. They reduce consumption of traditional energy sources, such as gas or electricity, and help cut CO2 emissions. Solar water heaters are an ecological and economical solution, with financial aid available to encourage their installation.
Other consumer goods
- Photovoltaic fabrics integrate lightweight, flexible photovoltaic cells into textiles to convert sunlight into electricity. These innovative materials offer many advantages, such as the ability to integrate solar power generation into a variety of applications (awnings, tents, clothing) in an aesthetically pleasing and functional way. What’s more, their lightness and flexibility make them easy to install, and enable them to be used on curved or irregular surfaces, opening up new opportunities for harnessing solar energy.
- Transparent photovoltaic films use organic photovoltaic cells to offer an aesthetic and versatile alternative to traditional solar panels. Their advantages include transparency, lightness and flexibility, enabling easy integration into various architectural and urban projects.
- Solar lawnmowers, for mowing the lawn powered by low-carbon electricity.
Solar energy around the world
At the start of the 21st century, the global energy landscape was at a turning point. In 2000, global solar capacity was still modest, representing just 1.2 GW. But the potential of this clean, renewable energy source was beginning to be recognized, and governments began to invest in its development.
Between 2006 and 2010, solar capacity grew substantially. Government investment and technological advances boosted global solar capacity from 6.7 GW in 2006 to 40 GW in 2010. During this period, the solar energy boom began to manifest itself in countries such as China, the United States and India, which adopted the technology on a large scale.
Between 2010 and 2015, solar power deployment accelerated further. Global solar capacity jumped from 40 GW to 227 GW, thanks to increased government commitment and falling solar panel costs. This period also saw many other countries follow the example of the world leaders and invest in solar energy.
The 2015-2020 period saw sustained growth, with global solar capacity reaching 714 GW by 2020. Lower costs and increased investment in the sector have contributed to this rapid expansion. More and more countries have recognized the environmental and economic benefits of solar power, driving a global energy transition to a more sustainable future.
The five major players – China, the United States, Japan,India andGermany – dominate the sector, accounting for around 70% of global solar capacity, with China accounting for almost half (254 GW by 2021). In second place is the USA, with an installed solar capacity of 76 GW in 2021.
- https://www.maison-travaux.fr/maison-travaux/renovation-par-type/energies-renouvelables-renovation-par-type/solaire-energies-renouvelables-renovation-par-type/energie-solaire-ca-fonctionne-fp-183097.html
- https://www.planete-energies.com/fr/medias/decryptages/la-cellule-photovoltaique-comment-ca-marche