Renewable Energy Glossary

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Capacity Factor

The relation between average power and rated (or maximum) power. A hydro turbine can often average more than 50% of its rated power on a good site, whereas a wind turbine or a solar array will produce well below 50% capacity factor.

Cellulose Insulation

A type of insulation composed of waste newspaper, cardboard, or other forms of waste paper combined with a fire retardant.

Centralized Generation

Electricity that is produced at large power plants and transmitted great distances through power lines to the end user.

CFLs

Compact fluorescent light bulbs (CFLs) use a quarter of the energy of incandescent bulbs, while generating the same amount of light. When operating, an electric arc is drawn along the length of the glass tube. The ultraviolet light produced by the arc activates a phosphorescent coating on the inside of the tube wall, which then emits visible light.

Charge Controller

In battery-charging systems, charging is optimized by controlling battery voltage. If the voltage rises above the set point, then the charging current is reduced to prevent further rise, ensuring that the batteries do not get overcharged. In microhydro systems, the turbine current must not be reduced, so the surplus current is diverted to a dump load.

Check Valve

A valve that allows flow in one direction only. Can be configured as a swing gate or spring actuated.

Circuit Breaker

A type of overcurrent protection device that automatically operates when there is excess current on a circuit.

Circulator Pump

An electromechanical device that moves liquids. SWH systems use hot water circulators that are normally rated at 240 degrees F.

Clamp-On Current Meter

A meter that measures amperage by clamping an insulated meter around a conductor to read the induced electron flow.

Clerestory

A vertical window placed high in a wall at the eaves, or between a lower roof and a higher roof, used for light, heat gain, and possibly ventilation.

Closed Loop System

A solar hot water system in which no part is vented to the atmosphere or fed with fresh liquid. Closed loop SWH systems are configured as antifreeze and drainback systems where the collector loop fluid is recirculated. Also known as indirect systems.

Cob Construction

A traditional building technique using hand-formed lumps of earth mixed with sand and straw.

Collector

See solar thermal collector

Collector Loop

The plumbing loop in a solar hot water system that includes the solar collectors. The collectors heat the fluid in the collector, and the heated fluid can be used directly (if water) or the heat can be exchanged to a potable water loop.

Collector Tilt

The measure of the angle between the collector slope and a horizontal plane.

Compact Fluorescent Light Bulbs

Bulbs that use a quarter of the energy of incandescents, while generating the same amount of light. When operating, an electric arc is drawn along the length of the glass tube. The ultraviolet light produced by the arc activates a phosphorescent coating on the inside of the tube wall, which then emits visible light.

Competent Person

The OSHA definition of a competent person is “one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.”

Condensation

The process of changing vapor into liquid by extracting heat. This occurs when warm, moist air comes in contact with a colder surface and deposits moisture onto that surface.

Condenser Bulb

Heat exchanger at the top of a heat pipe in an evacuated tube collector.

Conditioned Square Footage or Space

Area in which air is heated, cooled, cleaned, or otherwise managed for comfort.

Conditions of Use

The environmental conditions affecting equipment or conductors, which include ambient temperature, temperature adders for rooftops, multiple conductors in a conduit, and other location-based conditions such as dust, submersion potential, and indoor or outdoor locations.

Conduction

Heat transfer from a hot object to a colder object through direct contact.

Conductor

A conductor allows electrical current to flow. The term conductor is also used to refer to a wire.

Conduit

A pipe or tube for protecting electrical wire or cable.

Continuity

An electrical path exists between two points.

Continuous

A continuous circuit may carry maximum current for three hours or more; the NEC states that PV system currents are to be considered continuous.

Controller

This term is most often used to describe an electronic control box that is sold with the turbine, and fulfills multiple functions including a rectifier, brake-switch for manual short circuiting, circuit breakers, meters, and sometimes even MPPT capability. The controller usually also regulates the voltage.

Convection

Heat transfer by the natural or forced movement of fluid, typically air or water.

Cross-Flow Turbine

Also known as the Banki-Michell turbine, or Ossberger turbine, a simply constructed impulse turbine that can use large and variable flows. Water is fed through a slot-shaped nozzle into a cylindrical runner, passing through the vanes again as it leaves. Flow is controlled over a wide range by adjusting the width and/or length of the nozzle.

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