The action of light on a biological system that results in the dissociation of a substrate, usually water, to produce hydrogen.

A region of transition between semiconductor layers, such as a p/n junction, which goes from a region that has a high concentration of acceptors (p-type) to one that has a high concentration of donors (n-type).

A process for carrying out a reaction in which the reactants are fed in discrete and successive charges.

A type of electrical current, the direction of which is reversed at regular intervals or cycles; in the U.S. the standard is 120 reversals or 60 cycles per second; typically abbreviated as AC.

A quantity of (solid) biomass fuel equal to 2,400 pounds bone dry.

A component of a electrochemical battery. A 'primary' cell consists of two dissimilar elements, known as 'electrodes,' immersed in a liquid or paste known as the 'electrolyte.' A direct current of 1-1.5 volts will be produced by this cell. A 'secondary' c ...

In reference to solar energy systems, the angle at which direct sunlight strikes a surface; the angle between the direction of the sun and the perpindicular to the surface. Sunlight with an incident angle of 90 degrees tends to be absorbed, while lower an ...

A unit of measure for an electrical current; the amount of current that flows in a circuit at an electromotive force of one Volt and at a resistance of one Ohm. Abbreviated as amp.

The temperature at which a material ignites.

A method of predicting heating and/or cooling loads using instantaneous load calculation at different outdoor dry-bulb temperatures, and multiplying the result by the number of hours of occurrence of each temperature.

The power conduit of an electric power plant; the starting point of the electric transmission system.

A chemical change in a substance that results from the passage of an electric current through an electrolyte. The production of commercial hydrogen by separating the elements of water, hydrogen, and oxygen, by charging the water with an electrical current ...

A device, such as a steel plate, used to check, retard, or divert a flow of a material.

A type of heating fuel derived by refining crude oil that has a boiling range at atmospheric pressure from 400 degrees to 550 degrees F.

In a solar energy system, refers to all components other than the collector. In terms of costs, it includes design costs, land, site preparation, system installation, support structures, power conditioning, operation and maintenance costs, indirect storag ...

42 U.S. gallons (306 pounds of oil, or 5.78 million Btu).

Two metals of different coefficients of expansion welded together so that the piece will bend in one direction when heated, and in the other when cooled, and can be used to open or close electrical circuits, as in thermostats.

A thin coating of a material applied to a photovoltaic cell surface that reduces the light reflection and increases light transmission.

The usually unfinished space above a ceiling and below a roof.

The measure of seasonal or annual efficiency of a residential heating furnace or boiler. It takes into account the cyclic on/off operation and associated energy losses of the heating unit as it responds to changes in the load, which in turn is affected by ...