Solar Basics
Solar Glossary O - P
- One Sun
- The maximum value of natural solar insolation.
- Orientation
- The alignment of a building along a given axis to face a specific geographical direction. The alignment of a solar collector, in number of degrees east or west of true south.
- Overhang
- A building element that shades windows, walls, and doors from direct solar radiation and protects these elements from precipitation.
- Packing Factor
- The ratio of solar collector array area to actual land area.
- Panel (Solar)
- A term generally applied to individual solar collectors, and typically to solar photovoltaic collectors or modules.
- Parabolic Dish
- A solar energy conversion device that has a bowl shaped dish covered with a highly reflective surface that tracks the sun and concentrates sunlight on a fixed absorber, thereby achieving high temperatures, for process heating or to operate a heat (Stirling) engine to produce power or electricity.
- Parabolic Trough
- A solar energy conversion device that uses a trough covered with a highly reflective surface to focus sunlight onto a linear absorber containing a working fluid that can be used for medium temperature space or process heat or to operate a steam turbine for power or electricity generation.
- Passive Solar (Building) Design
- A building design that uses structural elements of a building to heat and cool a building, without the use of mechanical equipment, which requires careful consideration of the local climate and solar energy resource, building orientation, and landscape features, to name a few. The principal elements include proper building orientation, proper window sizing and placement and design of window overhangs to reduce summer heat gain and ensure winter heat gain, and proper sizing of thermal energy storage mass (for example a Trombe wall or masonry tiles). The heat is distributed primarily by natural convection and radiation, though fans can also be used to circulate room air or ensure proper ventilation.
- Passive Solar Heater
- A solar water or space-heating system in which solar energy is collected, and/or moved by natural convection without using pumps or fans. Passive systems are typically integral collector/storage (ICS; or batch collectors) or thermosyphon systems. The major advantage of these systems is that they do not use controls, pumps, sensors, or other mechanical parts, so little or no maintenance is required over the lifetime of the system.
- Passive Solar Home
- A house built using passive solar design techniques.
- Peak Sun Hours
- The equivalent number of hours per day when solar irradiance averages 1 kW/m2. For example, six peak sun hours means that the energy received during total daylight hours equals the energy that would have been received had the irradiance for six hours been 1 kW/m2.
- Peak Watt
- A unit used to rate the performance of a solar photovoltaic (PV) cells, modules, or arrays; the maximum nominal output of a PV device, in Watts (Wp) under standardized test conditions, usually 1000 Watts per square meter of sunlight with other conditions, such as temperature specified.
- Performance Ratings
- Solar collector thermal performance ratings based on collector efficiencies, usually expressed in Btu per hour for solar collectors under standard test or operating conditions for solar radiation intensity, inlet working fluid temperatures, and ambient temperatures.
- Phase-Change Material
- A material that can be used to store thermal energy as latent heat. Various types of materials have been and are being investigated such as inorganic salts, eutectic compounds, and paraffins, for a variety of applications, including solar energy storage (solar energy heats and melts the material during the day and at night it releases the stored heat and reverts to a solid state).
- Photobiological Hydrogen Production
- A hydrogen production process that process uses algae. Under certain conditions, the pigments in certain types of algae absorb solar energy. An enzyme in the cell acts as a catalyst to split water molecules. Some of the bacteria produces hydrogen after they grow on a substrate.
- Photovoltaic (PV; Solar) Array
- A group of solar photovoltaic modules connected together.
- Photovoltaic (Solar) Cell
- Treated semiconductor material that converts solar irradiance to electricity.
- Photovoltaic Device
- A solid-state electrical device that converts light directly into direct current electricity of voltage-current characteristics that are a function of the characteristics of the light source and the materials in and design of the device. Solar photovoltaic devices are made of various semi-conductor materials including silicon, cadmium sulfide, cadmium telluride, and gallium arsenide, and in single crystalline, multi-crystalline, or amorphous forms.
- Photovoltaic (Solar) Module or Panel
- A solar photovoltaic product that generally consists of groups of PV cells electrically connected together to produce a specified power output under standard test conditions, mounted on a substrate, sealed with an encapsulant, and covered with a protective glazing. Maybe further mounted on an aluminum frame. A junction box, on the back or underside of the module is used to allow for connecting the module circuit conductors to external conductors.
- Photovoltaic (Solar) System
- A complete PV power system composed of the module (or array), and balance-of-system (BOS) components including the array supports, electrical conductors/wiring, fuses, safety disconnects, and grounds, charge controllers, inverters, battery storage, etc.
- Photovoltaic-Thermal (PV/T) Systems
- A solar energy system that produces electricity with a PV module, and collects thermal energy from the module for heating. There are no commercially available systems available (as of 11/97).
- Power (Solar) Tower
- A term used to describe solar thermal, central receiver, power systems, where an array of reflectors focus sunlight onto a central receiver and absorber mounted on a tower.
- Preheater (Solar)
- A solar heating system that preheats water or air that is then heated more by another heating appliance.
- Pyranometer
- A device used to measure total incident solar radiation (direct beam, diffuse, and reflected radiation) per unit time per unit area.
- Pyrheliometer
- A device that measures the intensity of direct beam solar radiation.
About the list of terms on this page.
The U.S. Department of Energy Efficiency and Renewable Energy Home Page is a great starting point for learning about renewable energy methods and sources. To assist the educated consumer, the website provides calculators and guides of all kinds to assist the consumer in saving money, saving energy and making the most of the renewable energy sources available. The solar energy terms and definitions on our glossary pages were extracted from the extensive DOE EERE glossary of terms about all aspects and forms of energy.