Renewable Energy Glossary

1 A B C D E F G H I J K L M N O P Q R S T U V W Y

OCPDs

Overcurrent protection devices (OCPDs) are circuit breakers or fuses that protect conductors and equipment from overheating and failure caused by current flow higher than their ampacity.

Ohm's Law

Defines the relationship between voltage (V), current (A), resistance (R), and watts (W) in electrical circuits. Frequently used equations derived from Ohm's Law are V = A x R and W = V x A.

One Sun

A sun intensity of 1,000 watts per square meter.

Open Circuit Voltage

The maximum voltage available from a PV module or array; at this point current (and thus power) is zero.

Open Loop System

A potable water or “direct” solar hot water system, generally for use in freeze-free climates.

Operating Guideline-100

A protocol for certifying solar collectors known as OG-100; each certified collector has a rating; www.solar-rating.org.

Operating Guideline-300

A protocol for certifying entire solar systems known as OG-300; each system has a rating and estimated performance in a number of cities in the U.S. www.solar-rating.org.

Orientation

The direction, either north, south, east, or west, that a building or solar collectors face. In general, a passive solar building and solar collectors should be oriented south.

OSHA

The Occupational Safety and Health Administration (OSHA) was created by Congress to make and implement standards to ensure a safe and healthy working environment.

Overcurrent Protection

Circuit breakers or fuses that protect conductors and equipment from overheating and failure caused by current flow higher than their ampacity.

Overcurrent Protection Device

Circuit breakers or fuses that protect conductors and equipment from overheating and failure caused by current flow higher than their ampacity.

Overhang

A building element that shades windows, walls, and doors from direct solar radiation and protects these elements from precipitation. When properly sized and integrated, overhangs allow direct solar gain when it is wanted in the winter and prevent solar gain from entering the space in the summer.

Overshot Waterwheels

A traditional water wheel can achieve about 60% efficiency, which approaches the efficiency of modern turbines. These have been used for mechanical waterpower, and are occasionally used for electrical generation, though they are slow and need a gearbox. One advantage is that they are fish-friendly.

1 A B C D E F G H I J K L M N O P Q R S T U V W Y

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