Environmental Engineering Reference
In-Depth Information
Paper pellets:
Paper compressed and bound into uniform diameter pellets to be
burned in a heating stove.
Parabolic dish:
A high-temperature (above 180°F) solar thermal concentrator, gen-
erally bow-shaped and with two-axis tracking.
Parabolic trough:
A high-temperature (above 180°F) solar thermal concentrator
with the capacity for tracking the sun using one axis of rotation.
Particulate:
A small, discrete mass of solid or liquid matter that remains individu-
ally dispersed in gas or liquid emissions. Particulates take the form of aero-
sol, dust, fume, mist, smoke, or spray. Each of these forms has different
properties.
Passive solar:
A system in which solar energy alone is used for the transfer of ther-
mal energy. Pumps, blowers, or other heat-transfer devices that use energy
other than solar are not used.
Peak demand:
The maximum load during a specified period of time.
Peak watt:
A manufacturer's unit indicating the amount of power a photovoltaic cell
or module will produce at standard test conditions (normally 1000 watts per
square meter at 25°C).
Peaking plants:
Electricity generators that are operated to meet the peak or maxi-
mum load on the system. The cost of energy from such plants is usually
higher than from baseload plants.
Peat:
Consisting of partially decomposed plant debris, peat is considered an early
stage in the development of coal. Peat is distinguished from lignite by the
presence of free cellulose and a high moisture content (exceeding 70%).
The heat content of air-dried peat (about 50% moisture) is about 9 million
Btu per ton. Most U.S. peat is used as a soil conditioner.
Permeability:
The ability of a rock to transmit fluid through its pores or fractures
when subjected to a difference in pressure; typically measured in darcies
or millidarcies.
Petrochemical feedstocks:
Chemical feedstocks delivered from petroleum princi-
pally for the manufacture of chemicals, synthetic rubber, and a variety of
plastics.
Phenology:
The study of periodic plant and animal life-cycle events and how these
are influenced by seasonal and interannual variations in climate.
Photosynthesis:
The manufacture by plants of carbohydrates and oxygen for car-
bon dioxide and water in the presence of chlorophyll, with sunlight as the
energy source. Carbon is sequestered, and oxygen and water vapor are
release in the process.
Photovoltaic (PV) cell:
An electronic device consisting of layers of semiconductor
materials fabricated to form a junction (adjacent layers of materials with
different electronic characteristics) and electrical contacts and being capa-
ble of converting incident light directly into electricity (direct current).
Photovoltaic (PV) module:
An integrated assembly of interconnected photovoltaic
cells designed to deliver a selected level of working voltage and current at
its output terminals, packaged for protection against environmental degra-
dation, and suited for incorporation in photovoltaic power systems.
