What is the sun

The sun is a G2 star, slightly larger than an average star in our galaxy. In its core, every second, 700 million tonnes of hydrogen are converted into helium through nuclear fusion reactions, releasing an amount of energy equal to 386 billion billion megawatts.

The energy produced by nuclear reactions inside the sun travels the distance separating our star from the Earth in 8 minutes. Once it reaches us, it has a power of 1,350 watts per square metre of ground: this value is known as the "solar constant", as it does not vary over time.

The surface of the Earth receives 175,000 TW (1 terawatt = 1 million million watts) of solar energy. This means that the sun continuously floods the Earth with an amount of energy thousands and thousands of times greater than all the energy used globally by humankind.

Today on Earth we use around 15 terawatts of energy to power the global economy. The sun supplies 175,000 terawatts to our planet. So this should certainly be the most widely used source… As it was in the past, in the first 500,000 years of human history.

Solar energy is renewable.

Solar energy, hydroelectric power, wind energy, biomass, waves and marine currents are renewable energy sources. That is, they renew themselves in perpetuity, unlike fossil fuels (oil, coal, pet coke); they are widespread in nature, they circulate and are virtually inexhaustible. Their conversion into electrical energy usable by humans has a lower environmental impact than any other energy source.

At an international level, renewable energies are the main tools identified for achieving all the greenhouse gas emission reduction targets set out in the Kyoto Protocol and for reducing dependence on oil-producing countries. Italy, as a member state of the European Union, has set itself a 20% target for energy production from renewable sources, energy saving and reduction of CO2 emissions, to be achieved by 2020. All renewable energy sources, with appropriate technologies, can be converted into useful secondary energy, which may be thermal, electrical, mechanical or chemical.

Solar energy, in particular, can be converted into thermal energy (for uses such as domestic hot water or space heating, and for the passive climate control of homes) or into electrical energy through many different technological systems that exploit the physical phenomenon of the photovoltaic effect or concentrating solar power.