Solar Energy Glossary

What Is Solar Energy?

Solar energy is energy that comes from the sun. A solar energy system harnesses the sun’s energy and turns it into electricity. You may come across these often complex and technical terms while learning about solar energy and solar energy systems. To aid in your understanding of these topics we have compiled a glossary of commonly used solar energy terminology.

Terms To Know

Alternative Energy (renewable energy) —  energy harnessed from a limitless source like wind or sunshine. Non-renewable energy sources include fossil fuels which are a limited resource. 

Alternating Current (AC) — A type of electrical current, the direction of which is reversed at regular intervals or cycles. 

Ampere (amp) — A unit of electrical current or rate of flow of electrons. 

Annual Solar Savings — The annual solar savings of a solar building is the energy savings attributable to a solar feature relative to the energy requirements of a non-solar building.

Balance of System — Represents all components and costs other than the photovoltaic array. It includes design costs, land, site preparation, system installation, support structures, power conditioning, operation and maintenance costs, indirect storage, and related costs.

Base Load — The average amount of electric power that a utility must supply in any period.

Battery Capacity — The maximum total electrical charge, expressed in ampere-hours, which a battery can deliver to a load under a specific set of conditions.

British thermal unit (Btu) — The amount of heat required to raise the temperature of one pound of water one degree Fahrenheit.

Cell (Battery) — A device that converts chemical energy into electrical energy. A battery usually consists of several cells electrically connected together to produce higher voltages.

Concentrating Solar Power (CSP) — A solar technology that uses mirrors to reflect and concentrate sunlight onto receivers that convert solar energy to heat. This thermal energy is then used to produce electricity with a steam turbine or heat engine driving a generator.

Conductor — The material through which electricity is transmitted, such as an electrical wire, or transmission line.

Direct Current (DC) — A type of electricity transmission and distribution by which electricity flows in one direction through the conductor. 

Discharge — The withdrawal of electrical energy from a battery.

Distributed Energy Resources (DER) — A variety of small, modular power-generating technologies that can be combined with energy management and storage systems and used to improve the operation of the electricity delivery system, whether or not those technologies are connected to an electricity grid.

Efficiency —  Efficiency is the term used to describe how well a solar energy system converts sunlight into power. 

Electricity — Energy resulting from the flow of charged particles, such as electrons or ions.

Electric Current — The flow of electrical energy (electricity) in a conductor, measured in amperes.

Electrical Grid — An integrated system of electricity distribution, usually covering a large area. An electrical grid delivers energy from the producer to the consumer. 

Electron — An elementary particle of an atom with a negative electrical charge.

Energy Density — The ratio of available energy per pound; usually used to compare storage batteries.

Full Sun — The amount of power density in sunlight received at the earth's surface at noon on a clear day.

Hybrid System — A solar electric or photovoltaic system that includes other sources of electricity generation, such as wind or diesel generators.

Inverter — A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.

Life-cycle Cost — The estimated cost of owning and operating a photovoltaic system for the period of its useful life.

Ohm— A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current of 1 ampere.

Peak Demand/Load — The maximum energy demand or load in a specified time period.

Photovoltaic (PV) –– A complete set of components for converting sunlight into electricity by the photovoltaic process, including the array and balance of system components. 

Photovoltaic Cell (Solar Cell) — The smallest semiconductor element within a PV system to perform the immediate conversion of light into electrical energy.

Power — The amount of electrical energy available for doing work, measured in horsepower, Watts, or Btu per hour.

Solar Energy — Electromagnetic energy transmitted from the sun (solar radiation). 

Solar Energy System — A device, array of devices, or structural design feature, which provides the generation or storage of electricity from sunlight. 

Large-Scale — A solar energy system that occupies more than 40,000 square feet of surface area.

Medium-Scale — A solar energy system that occupies more than 1,750 but less than 40,000 square feet of surface area.

Small-Scale — A solar energy system that occupies 1,750 square feet of surface area or less.

Reserve Capacity — The amount of generating capacity a central power system must maintain to meet peak loads.

Roof-mounted Solar Energy System —  A solar photovoltaic system mounted on a rack that is ballasted on, or is attached to, the roof of a building or structure.

Volt — A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.


Department of Energy Solar Glossary 

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