Click on the town names for examples of renewable energy projects.

Montana Green Power

Your Guide to Renewable Energy in Montana


Glossary of Renewable Energy 
Terms and Phrases

(Source: U.S. Department of Energy Solar Now Project)

A B C D E F G H I J K L M 

O P Q R S T U V W X Y Z 


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 sulphuric, nitric and other acids which arise from emissions released during the burning of fossil fuels.

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


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

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.

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



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.


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

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



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



The ration 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.

The capacity to do work.

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. renewables (solar, wind, geothermal, biomass, hydro).


Flat Plate

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

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

Fluorescent light
A device that 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.

A material that 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 that 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 fuels 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."

Pertaining to heat energy extracted from reservoirs in the earth's interior, as is 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 chlorofluorocarbons (CFCs) and carbon dioxide.


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

Hydro power
Power obtained from the natural movement of masses of water.

Incandescent light
A bulb that 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.



The solar radiant energy impinging on the earth.

A device that 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

Nuclear fission
Atomic nuclear processes which involve the splitting of nuclei with the accompanying release of energy.

Nuclear fuel
Energy derived from atomic nuclear processes during fission or fusion.

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



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.



Photovoltaic; pertaining to the production of electricity from light.

Photovoltaic cell
(see Solar cell)


Renewable energy

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

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


Solar cell

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

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

Solar electricity
Electricity produced directly by action of sunlight; photovoltaics

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 berm.

Solar heating
Processes, active or passive, that 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 receiver 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-Intertied system

Utility-Intertied system
A PV installation connected to a utility power line.



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 that produce mechanical or electrical power.

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Next Section: Other Resources


2001 Solar Demo Homes
Solar Power Initiative
Montana Solar Dealers
Ag Solar

Solar Books

Solar Water Heating
Solar Power Links

Solar in Schools

PV Residential Demonstration    

Solar Projects





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