AC: Electrical energy which alternates cyclically between positive and negative in polarity. In many countries, including the U.S., the polarity reversal is made to occur 60 times per second (60 hertz). 

Acid Rain: Rain mixed with sulfuric, nitric and other acids which arise from emissions released during the burning of fossil fuels. 

Ampere (amp): The number of electrons flowing past a given point in an electrical conductor in a given amount of time; this is the electrical current. 

Ballast: A charging device in fluorescent lights which give a "jump start" to the gas inside the tube to make it start glowing steadily. 

Biomass: Living materials (wood, vegetation, etc.) grown or produced expressly for use as fuel. 

Biomass fuels: Wood and forest residues, animal manure and waste, grains, crops and aquatic plants are some common biomass fuels. 

BTU: British Thermal Unit—A measure of heat energy; the amount needed to raise the temperature of one pound of water by one degree Fahrenheit. 

Calorie: Metric thermal unit: a measure of heat energy; the amount needed to raise the temperature of one kilogram of water by one degree Centigrade. This is the large Calorie (used relating to food energy content) definition. The small calorie of fuel research is the amount of energy needed to raise the temperature of one gram of water by one degree Centigrade. 

Concentrator: A tool that uses lenses and/or mirrors to focus and enhance the sun's rays onto the photovoltaic surface. 

Conservation: Achieving the use of less energy, either by using more efficient technologies or by changing wasteful habits. 

DC: Electrical energy which does not cyclically alternate in polarity: e.g. electrical energy from a battery or solar cell. 

Efficiency: The ratio of desired work-type output to the necessary energy input, in any given energy transformation device. An efficient LIGHT bulb for example uses most of the input electrical energy to produce light, not heat. An efficient heat bulb uses most of its input to produce heat, not light. 

Energy: The capacity to do work. 

Energy-efficient: Electrical lighting devices which produce the same amount of light (lumens) using less electrical energy than incandescent electric light bulbs. Such devices are usually of the fluorescent type, which produce little heat, and may have reflectors to concentrate or direct the light output. 

Energy sources: Energy sources are 1. fossil fuels (coal, oil, gas); 2. nuclear (fission and fusion); 3. renewable (solar, wind, geothermal, biomass, hydro). 

Flat Plate: A photovoltaic surface installed to face south at a tilt angle equal to the latitude. 

Flat-plat tracker: A device mounted under a photovoltaic panel that moves the panel to follow the path of the sun. 

Fluorescent light: A device which uses the glow discharge of an electrified gas for the illuminating element rather than an electrically heated glowing conductive filament. 

Fossil fuels: Fuels formed eons ago from decayed plants and animals. Oil, coal and natural gas are such fuels. 

Fuel: A material which is consumed, giving up its molecularly stored energy which is then used for other purposes, e.g. to do work (run a machine).

Fuel cell: A device which produces electricity with high efficiency (little heat) by using a fuel and a chemical which reacts with it (an oxidizer) at two separate electrical terminals. An electric current is thereby produced. 

Fuel efficiency: The amount of work obtained for the amount of fuel consumed. In cars, an efficient fuel allows more miles per gallon of gas than an inefficient fuel. 

Gaia Hypothesis: The idea that Earth is a living system. Life helps create the environment it needs in order to live. Gaia is the ancient Greek word for "Mother Earth." 

Geothermal: Pertaining to heat energy extracted from reservoirs in the earth's interior, as in the use of geysers, molten rock and steam spouts. 

Geothermal energy: Heat generated by natural processes within the earth. Chief energy resources are hot dry rock, magma (molten rock), hydrothermal (water/steam from geysers and fissures) and geopressure (water saturated with methane under tremendous pressure at great depths). 

Global warming: The gradual warming of the earth due to the "greenhouse effect". 

Greenhouse effect: The trapping of the sun's radiant energy, so that it cannot be reradiated. In cars and buildings the radiant energy is trapped by glass: in the earth's atmosphere the radiant energy is trapped by gasses such as CFCs and carbon dioxide. 

Hydro: A prefix meaning produced by or derived from water or the movement of water, as in "hydroelectricity". 

Hydropower: Power obtained from the natural movement of masses of water. 

Incandescent light: A bulb which uses the ohmic resistance in a conductor to produce light upon the passage of an electrical current through it. The conductor is usually in the form of a wire or filament. 

Insolation: The solar radiant energy impinging on the earth. 

Inverter: A device which changes direct current (DC) into alternating current (AC). Direct current is created by photovoltaic modules or batteries and converted to AC through the use of an inverter. 

Nuclear fission: Atomic nuclear processes which involve the splitting of nuclei with the accompanying release of energy. VERY DANGEROUS TO HUMANS!!!

Nuclear fuel: Energy derived from atomic nuclear processes during fission or fusion. VERY DANGEROUS TO HUMANS!!! AND EARTH

Nuclear fusion: Atomic nuclear processes which involve the fusing of nuclei with an accompanying release of energy. VERY DANGEROUS!!!

OTEC: Ocean thermal energy conversion technology, which uses the temperature differential between warm surface water and cold deep water to run heat engines to produce electrical power. 

Ocean energy: The vast amount of potential energy within the oceans. 

PV: Photovoltaic; pertaining to the production of electricity from light. 

Photovoltaic cell: SEE SOLAR CELL BELOW, it means the same thing

Renewable energy: Energy from sources that cannot be used up: sunshine, water flow, wind and vegetation. 

Renewable energy devices: Solar collectors, wind machines, hydroelectric turbines, etc. are typical examples. 

Solar cell: Device made of semiconductor materials which produces a voltage when exposed to light. 

Solar cooling: The use of devices which absorb sunlight to operate systems similar to gas-fired refrigerators. 

Solar electricity: Electricity produced directly by action of sunlight. 

Solar greenhouse: A conventional greenhouse in which mass is added for heat storage, double glazing is used, and the north side is attached to a house or beam. 

Solar heating: Processes, active or passive, which derive and control heat directly from the sun. 

Solar process heat: The use of sunlight to drive industrial processes directly. 

Solar thermal energy systems: Systems using concentrating collectors to focus the sun's radiant energy onto or into receivers to produce heat. 

Stand-Alone system: A PV installation not connected to a utility power line. A 'direct system' uses the PV-produced electricity as it is produced, e.g. a solar-powered water-pumping station. A 'battery storage system' stores the PV-produced electricity for use a later time, e.g. at night or on cloudy days. 

Utility-Interactive System: A PV installation connected to a utility power line. 

Weather: The result of unequal heating of the earth's atmosphere, as a function of terrain, latitude, time of year and other secondary factors. 

Wind machines: Devices powered by the wind which produce mechanical or electrical power.