The processes that a work input/output system undergoes and in which the initial and final states are identical.

A water heater that heats water before it is directly distributed for end use as required; a demand water heater.

The transfer of heat through a material by the transfer of kinetic energy from particle to particle; the flow of heat between two materials of different temperatures that are in direct physical contact.

The period of low energy demand, as opposed to maximum, or peak, demand.

The path followed by electrons from a generation source, through an electrical system, and returning to the source.

A measure of the amount of light incident on a surface; measured in foot-candles or Lux.

The process of breaking down organic material; reduction of the net energy level and change in physical and chemical composition of organic material.

The concept of capturing and converting the energy available in the motion of ocean waves to energy.

A refined petroleum product suitable for use as a fuel in internal combustion engines.

The force that pulls a wind turbine blade, as opposed to drag.

The quantity of heat necessary to raise the temperature of a specific mass of a substance by one degree.

The flow of heat from one area to another by conduction, convection, and/or radiation. Heat flows naturally from a warmer to a cooler material or space.

All the components of the appliance used to condition interior air of a building.

A type of heating system where heat, resulting when electric current flows through an "element" or conductor, such as Nichrome, which has a high resistance, is radiated to a room.

A device consisting of two dissimilar conductors with their ends connected together. When the two junctions are at different temperatures, a small voltage is generated.

The ratio of a photovoltaic cell's actual power to its power if both current and voltage were at their maxima. A key characteristic in evaluating cell performance.

A type of heat pump that uses the ground, ground water, or ponds as a heat source and heat sink, rather than outside air. Ground or water temperatures are more constant and are warmer in winter and cooler in summer than air temperatures. Geothermal heat p ...

A wood or gas burning heating appliance that fits into the opening or protrudes on to the hearth of a conventional fireplace.

The ability of a building construction assembly (partition, wall, floor, etc.) to resist the passage of fire. The rating is expressed in hours.

This is an independent regulatory agency within the U.S. DOE that has jurisdiction over interstate electricity sales, wholesale electric rates, natural gas pricing, oil pipeline rates, and gas pipeline certification. It also licenses and inspects private, ...