Glossary: P to R
A-C | D-F | G-I | J-L | M-O | P-R | S-U | V-Z
P
Particulates: Particulates are criteria pollutants that include dust, dirt, soot, smoke and other miniscule solids released into the air and can affect heart and respiratory health. Particulates can be composed of many different chemicals. Their human sources vary but come largely from construction activities like road building. Particulates can also form when emissions from fossil fuels react with sunlight and water vapor to create solid particles in the air.
Passive solar design: Passive solar design is the use of various design techniques in a building to capitalize on heat and light from the sun and reduce the need for mechanical and electric systems. These techniques include daylighting, large south-facing windows, natural shading and ventilation, and building materials that absorb heat from the sun and slowly release it to warm the building. Proper use of passive solar design can reduce heating bills as much as 50%.
Photon: A particle of light that acts as an individual unit of energy.
Photovoltaics: See solar photovoltaics.
Potential energy: Potential energy is stored energy, waiting to be released. An example of potential energy is the energy embodied in ocean waves, which can be captured through ocean energy technologies to produce kinetic energy.
Power: Power is the rate at which work is done. The ratio of work and time determines the amount of power used. For example, imagine that two people start at the bottom of a mountain with the goal of reaching the top. The first person hikes to the top in a short amount of time. The second person scales the rocks to the top which takes a much longer amount of time. The same amount of work was done by both (they reached the top of the mountain), but the hiker has more power since the distance traveled was completed in a shorter amount of time. Power is expressed in Watts.
Q
R
Radial system: A radial system is the most common and simplest type of electric distribution. In a radial system, as opposed to an area or spot network system, a single wire radiates from the main distribution line to an individual customer and power flows one way as opposed to flowing on multiple paths as in network systems. Many clean energy technologies can gain approval to interconnect to a radial system.
Radiant energy: Radiant energy comes from a light source, such as the sun. Energy released from the sun is in the form of photons. These tiny particles, invisible to the human eye, move in a way similar to a wave. Radiant energy can be transformed into electrical energy using solar panels.
Renewable energy: Renewable energy comes from sources that can be replenished on a human time scale, such as biomass (wood), or that are essentially inexhaustible, such as waste and geothermal, wind, and solar energy. Fossil fuels are non-renewable energy sources; there is a finite supply of them. Renewable energy is also often clean energy; it can be generated with few or zero emissions and little to no environmental damage.
Renewable Energy Trust (RET): The Renewable Energy Trust is a public benefit fund dedicated to the development of clean energy in Massachusetts. It focuses in particular on large-scale clean energy development, green buildings and distributed generation, development of the clean energy industry, and public education. Its efforts are led by the Massachusetts Technology Collaborative.