31 The first solar cell exploiting the photovoltaic effect to produce electricity dates back to the end of the 19th century. Where are photovoltaic panels usually placed? The latest domestic solar panels produce between 250 and 400 Watts of electricity per hour and between 750 and 850 Kilowatts per hour (KwH) a year. A typical household would need around 10,000 KwH per year, which can be generated by a solar system made up of 20-30 panels. SOLAR POWER The Sun has always been a source of light and heat for all life on Earth: it radiates energy which reaches our planet and is used by every living thing. However, despite its importance, only recent studies have shown how to capture energy from the Sun and use it for everyday needs . There are two different ways of producing electricity from the sun: either using CSP systems or photovoltaic panels . CSP systems Concentrating solar-thermal power (CSP) systems use solar collectors, which consist in mirrors that reflect and concentrate sunlight onto receivers. These receivers collect solar energy and convert it into heat, which is used to transform water, collected in reservoirs, into steam. The force of the steam is then used to produce electricity by activating a turbine connected to a generator. This system is used primarily in very large power plants. Receiver Steam generation system Generator Photovoltaic panels Photovoltaic panels are formed by photovoltaic cells arranged together in order to produce a bigger quantity of electricity. A photovoltaic cell is composed of two different layers of semiconductors, an N-type, semiconductor, which is negatively charged, and a P-type one, which is positively charged. When photons from the sunlight hit the N-type semiconductor, this material releases electrons that form an electric current, which is then captured and used to power electrical devices. At the beginning, photovoltaic cells were only used to power small appliances such as calculators. Nowadays, the number of solar power plants connected to distribution grids has risen a lot. Pros and cons Solar power is a renewable form of energy and can be used both for heating water and buildings and for generating electricity. As a power source, it is totally clean and produces no greenhouse gas emissions. However, solar power is highly dependent on climate Steam turbine and weather conditions; moreover, the cost of installing panels is still very high . Collector field Condenser Power Block Receiver system Condensate tank Thermal storage system 76 to rise: aumentare