Solar energy

The sun: a clean, reliable, renewable energy source

In 1839, Edmond Becquerel first observed the photovoltaic effect: the creation of electrical energy in a material upon exposure to light. But the world would have to wait until the conquest of space in the 1960s and the oil crisis of the 1970s for solar technology to be fully understood, developed and mastered. Today, with sustainable development a growing concern, solar energy is increasingly being seen as a viable solution to our energy needs.

Solar energy is produced as a result of nuclear fusion within the sun. This energy travels outward into space in the form of rays. The sun’s rays transmit two main forms of energy:

– thermal energy, or heat, which we have always used to heat our homes and greenhouses, for example. This “passive solar gain” can result in significant energy savings.

– light energy, in the form of photons, which can be converted to electricity using certain materials that naturally release electrons when exposed to light. This phenomenon, known as the “photovoltaic effect” is the basis of all solar energy systems.

The effectiveness of a solar energy system depends on a number of factors: the number of hours of sunshine, the season, weather conditions, albedo (the reflecting power of the surrounding surface), etc. Solar panels are always tilted and oriented to capture a maximum of light.

The sun is a highly stable and predictable resource, which makes solar technology correspondingly reliable and easy to use. And because the sun’s energy is converted directly into electricity by a semiconductor, and requires no fuel or moving parts, it creates no pollution. As a result, solar energy is one of the cleanest, most renewable forms of energy around.

How a solar energy system works

In a solar panel, each photovoltaic cell is made of light-sensitive semiconductor material. Such materials, of which silicon is a prime example, release their electrons when exposed to photons (particles of light).

In nature, electrons released by light-sensitive materials recombine immediately and do not generate any electricity. But a photovoltaic cell forces the released electrons into a particular direction to create an electric current.

To do this, one layer of semiconductor material, such as modified silicon, is placed on top of another: one has a positive charge, the other, a negative one. When the cell is exposed to sunlight (i.e. photons), the electrons released travel from one layer to the other, generating an electric current.

This direct current travels along wires connecting the cells to each other, and the current from all the panels is collected via a series of combiner boxes. Inverters in substations then convert the direct current into alternating current for transportation on the electric grid. Finally, a series of transformers step up the voltage so that the solar energy system can connect with the grid.

Generally speaking, one megawatt (“MW”) of solar energy produces enough electricity to meet the annual needs of more than 100 Canadian homes (consuming an average of 12 megawatt-hours (“MWh”) per year).