Energy and Global Climate Change in New England
Solar energy comes from using the sun as fuel to create heat or electricity. Solar technologies fall into two categories: passive and active. Passive solar produces heat and provides lighting for structures. Active solar produces electricity using a technology called Solar Photovoltaic (PV), or heat, hot water or electricity a technology called Solar Thermal.
Solar energy is considered environmentally friendly because the sun is a natural energy source that does not require the burning of fossil fuels and the associated air emissions. In addition, it is considered renewable since the energy produced from the sun does not deplete any natural resources, and will never run out.
Solar energy, however, is what is called an intermittent source, which means it is not always available. When it is cloudy or raining, the sun is unavailable to provide light, and solar energy systems are unable to produce energy. Therefore, many systems are designed with either some kind of energy storage feature, or a backup source of energy, such as the electric grid. These additional features allow the end user to continue to operate even when the sun is not shining.
Solar PV: Solar PV is the most common application in New England and generally the one with which people are most familiar. PV is one of the most environmentally friendly technologies available and is very easy to install on a building or property. PV technology uses the electrical properties of materials known as semiconductors to produce electricity. When hit by sunlight, a semiconductor material creates an electrical charge which can then be transferred through a circuit to anything that uses electricity. In a PV system, these semiconductors are produced in the form of cells, which are then assembled in a structural panel. Panels can then be assembled into larger groups, or arrays, to produce increasing amounts of electricity, depending on the amount of energy needed. Solar arrays can vary in size to provide the electricity needed for a home, office, or larger facility.
Passive Solar: Passive solar energy uses the sun's energy, simply through the way the structure is oriented, designed, and/or constructed. Buildings that use passive solar design can use fewer or smaller-scale active technologies to meet the remainder of their heating and lighting needs (e.g., smaller and cheaper mechanical systems). Because the sun's energy is free, maximizing use of passive solar techniques before adding active technologies can significantly reduce ongoing energy costs.
Solar Heating: When passive solar is not enough, supplemental heating can often be provided by other active solar technologies. Small scale water and space heating often use a solar collector that concentrates heat in either water pipes or an air handling system that then distributes the hot air or water through the building as necessary. More complex technologies such as Parabolic Trough Collectors or Evacuated Tube Collectors can be used for larger commercial and industrial heating applications.
Solar Thermal Electric: While most solar technologies are used in small-scale applications, solar thermal technologies can also be used on a much larger scale. These technologies are similar in concept to solar heating technologies, using sunlight to generate heat. They differ in that they create enough heat to power a generator that is then used to produce electricity. Around the country, the ability of utility scale applications of this technology to produce electricity is being tested.