It is easy to see the effect of the sun’s heat on objects. Ice cream and ice cubes melt; people move indoors, preferably to air-conditioned spaces. Sunlight has a different effect. Sunlight powers plant growth and creates vitamin D in the human body.
Innovations in the solar energy industry demonstrate that light energy from sunlight can also provide at last some of the world’s energy supply today and that it may prove to be the preferred global power source of the future.
Currently, the world relies on fossil fuel energy to power most of its economies and societies; that energy source, however, is also playing havoc with the atmosphere and environment. As the planet struggles with climate change and excess CO2 emissions from fossil fuel energy sources, science is looking at solar energy as a viable, economically and environmentally sound energy alternative. In the past 250 years, scientists have developed solar energy systems that capture sunlight as a source of electrical energy. Collected in sufficient amounts, sunlight can inexpensively and reliably power homes, appliances and even industries.
How solar panels work – converting light into electricity
A system of solar panels that collect sunlight for power is called an “array.” Each array is made up of hundreds of solar cells. Each cell is made up of special metals and silicon, a semiconductor substance that has some of the properties of metals, and some of the properties of an electrical insulator. The silicon can both collect the light (with the metal aspects, called “n-type silicon”) and contain its energy within the cell (the insulating part, called “p-type silicon”).
Sunlight is composed of photons. When photons hit the solar cell, they transfer their energy to loose electrons contained in the n-type silicon. The loose electrons take on more energy than other electrons in the silicon and shift over to the p-type silicon, creating a current. The n-type silicon is left with a positive charge, and the p-type attains a negative charge. Continued bombardment by sunlight causes the shifts of electrons to occur continuously, creating a steady current of electricity that is transferred through and out of the cell as DC current. Inverter systems convert the DC current to AC current, which is used in American homes.
Measuring the power of solar electricity
Energy is measured by how much force it takes to move an object. The standard measurement of force is a Newton (named after Sir Isaac Newton), represented by an N. The basic energy measurement unit is a Joule (named after Sir James Prescott Joule – J), which will move one N a distance of one meter. A watt (named after James Watt – W) is the amount of energy needed to move 1 Joule per second.
Electricity is measured in kilowatts (kW), or units of 1,000 watts. We measure electric use by how much is used per hour (kWh). The power of a single kilowatt hour can power 10 100-watt light bulbs for one hour. The average US household uses about 8900 kWh per year.
Labs testing solar panels calculate their energy output using a “peak sun” measurement of 1,000 watts of sunlight per square meter of surface. A 1kW solar energy system generates almost 1,000 kWh per year in cloudy regions and almost double that in sunny climates. The kW generation rate will be part of the calculation of how many solar panels will be needed to power a specific home in a specific location.
Strategic solar panel siting ensures maximum solar power
For optimal solar exposure, proper positioning of solar arrays is critical. In the northeast states (Vermont, Massachusetts, Connecticut), home solar panels should face true south to capture optimal exposure to the sun all year round. Installations in more southerly states — California, Colorado, Missouri — will generally get more solar exposure than solar arrays in northern states. A simple Google Earth view of any American home can provide the geographical registrations for the true south direction.
Installations that don’t have a true south face will need to increase their solar exposure with more or larger panels. Mounting them on brackets to orient them in a more southerly direction will also increase solar exposure. For those who don’t want solar panels on their homes, or their location is just not suitable for a solar panel installation, the panels can be sited in another location — mounted on panels on the ground or on buildings close to the home, like sheds or garages.
For all solar panel installations, avoiding shade and shadow from trees or adjoining structures will improve the collection of solar energy.
In 2013, the MIT Sustainable Design Lab introduced its solar map of Cambridge Massachusetts, which provides energy-saving estimates for solar power of 17,000 rooftops in the city. Calculating for base solar exposure, roof angles, weather data and shade or shadowing detail, the map can predict the perfect location for a solar installation on each building. Still a prototype, the technology will almost certainly be informing home and business owners about optimal solar array siting locations in the near future.
Solar power is reducing global reliance on fossil fuels and, at the same time, providing a reliable, clean, and economical source of electricity for thousands of American homes.
RGS Energy, founded in 1978, was the first solar energy system provider and installer in the United States, and is still the market leader. To learn how solar could lower your electric bills and to get a free quote, visit www.RGSEnergy.com.