Solar energy is a combination of heat and light produced by the sun. The sun is the basis of all life on Earth. All forms of renewable and fossil energies are somehow related to solar radiation. The average solar radiation over the course of one year arriving at the top of the Earth's atmosphere at any point in time is roughly 1,366 watts per square meter. Depending on the Sun angle at different times of the year, scattering processes in the Earth's atmosphere, the cloud cover effect and absorption, the Earth's surface receives a direct irradiance of at least 250 W/m², according to World meteorological Organization. This represents a daily irradiation of approximately 6 kWh/m².   

The overall power of solar radiation on Earth is estimated at 180,000 million megawatts, more than 15,000 times the world's present installed electric power. About 1.9 x 10⁸ TWh per year is absorbed by the land surfaces of the Earth, in comparison to the worldwide energy consumption of 1.3 x 10⁵ TWh per year. Thus, each year, sunlight provides over 1000 times our actual total energy consumption. In modern applications, solar energy can be used in solar thermal or solar photovoltaic for respectively heat or electricity supply.

Solar Thermal energy
Solar thermal energy is the process of converting sunlight into thermal energy. It is a direct utilization of solar heat. In green building construction, solar thermal is often used in a passive way to satisfy comfort needs without producing any amount of energy. This is accomplished through the use of passive systems and techniques such as adequate design of buildings, an appropriate installation of windows, patios and suntraps and the use of specific building materials to optimize the amount of light, heat and the ventilation inside a building. 

In temperate climates, heating buildings may require the use mechanical systems. When the sunlight can be harnessed; instead of using electrical powered systems, solar thermal systems offer an interesting alternatives for heating or hot water supply. The most common solar systems are solar water heater for hot water and solar floor heating system. These mechanisms allow not only to save on energy cost, which is good for our pocket but more importantly to cut on carbon emissions and contribute in global efforts to save the planet.

Solar Photovoltaic energy
Solar photovoltaic energy is the process of converting sunlight into electric current.The photons contained in solar radiation have the potential to set into motion electrons making some specific materials, called semi-conductive materials (silicon sulfide crystals, cadmium sulfide, etc.) or molecules such as chlorophyll. The flow of electrons create an electric field which generates a direct electric current. Photovoltaic cells are therefore a source of DC. A standard solar panels module is made of 36 PV cells and delivers a voltage of 18V with a nominal power of 50 W distributed over 0.5 m2. The PV solar panels are usually installed in rooftops or in ground-mounted solar farms. 

The first solar PV cells were installed on satellites and other spacecrafts. Solar PV gained a sudden interest after the first oil crisis of 1973. Since, the technology has tremendously improved and large solar power plants are operational in many countries accross the globe. According to the International Energy Agency (IEA), by 2014 the cumulative photovoltaic capacity has reached 178 GW, sufficient to supply 1% of the world's total electricity consumption of currently 18,400 TWh.