The field of clean energy involves a wide range of specialized terms and concepts. This glossary provides clear, concise explanations of key terminology to help you navigate discussions about renewable energy, energy efficiency, and the transition to a more sustainable energy system.

All A B C D E F G H I J-L M N-O P-Q R S T U-Z

A

Active Solar

Solar technologies that use mechanical devices such as pumps and fans to collect, convert, and distribute solar energy, often for heating water or generating electricity.

Alternating Current (AC)

An electric current that periodically reverses direction. Most household appliances operate on AC, while solar panels and batteries produce direct current (DC) that must be converted to AC.

Anaerobic Digestion

A biological process that breaks down organic matter in the absence of oxygen to produce biogas, which can be used as a renewable energy source.

B

Baseload Power

The minimum amount of electric power that needs to be supplied to the electrical grid at any given time. Traditionally provided by coal or nuclear plants, now increasingly supplemented by renewable sources with storage.

Bioenergy

Renewable energy derived from biological sources such as wood, agricultural residues, food waste, or algae, which can be used to produce heat, electricity, or transportation fuels.

Building-Integrated Photovoltaics (BIPV)

Solar power generating products that are seamlessly integrated into building materials, replacing conventional building materials in parts of the building envelope.

C

Capacity Factor

The ratio of actual energy output over a period of time to the potential output if the facility operated at full nameplate capacity continuously during the same period.

Carbon Capture and Storage (CCS)

A technology that captures carbon dioxide emissions from sources like power plants and stores it underground to prevent it from entering the atmosphere.

Community Solar

Solar installations that allow multiple customers to benefit from a single, shared solar array, providing access to solar for those who cannot install it on their own property.

D

Decarbonization

The process of reducing carbon dioxide emissions across the economy, particularly by decreasing the use of fossil fuels and increasing renewable energy sources.

Demand Response

Changes in electricity usage by end-use customers to better match supply, often in response to price signals or incentives to reduce consumption during peak demand periods.

Distributed Generation

Electricity generation that occurs close to where it will be used, such as rooftop solar panels, rather than at a centralized power plant.

E

Energy Efficiency

Using less energy to perform the same task or produce the same result, reducing energy waste and often leading to both cost savings and environmental benefits.

Energy Storage

Technologies that store energy for use at a later time, helping to balance supply and demand and integrate variable renewable energy sources into the grid.

Electric Vehicle (EV)

A vehicle that uses one or more electric motors for propulsion, powered by electricity from batteries, fuel cells, or other sources, rather than fossil fuels.

F

Feed-in Tariff (FiT)

A policy mechanism that offers long-term contracts to renewable energy producers, typically based on the cost of generation of each technology.

Fuel Cell

A device that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent into electricity through a pair of electrochemical reactions.

G

Geothermal Energy

Thermal energy generated and stored in the Earth, which can be harnessed to generate electricity or provide direct heating and cooling.

Green Hydrogen

Hydrogen produced through electrolysis powered by renewable electricity, resulting in minimal carbon emissions during production.

Grid Parity

The point at which the cost of generating renewable energy equals or is less than the cost of conventional grid power.

H

Heat Pump

A device that transfers heat from a cooler space to a warmer space using mechanical energy, used for both heating and cooling buildings.

Hydroelectric Power

Electricity generated by harnessing the energy of falling or flowing water, one of the oldest and largest sources of renewable energy worldwide.

I

Inverter

A device that converts direct current (DC) electricity, such as that produced by solar panels, into alternating current (AC) electricity used by most household appliances.

Irradiance

The power of solar radiation per unit area, typically measured in watts per square meter (W/m²), a key factor in determining solar energy potential.

J-L

Kilowatt-hour (kWh)

A unit of energy equal to one kilowatt of power sustained for one hour, commonly used to measure electricity consumption.

Levelized Cost of Energy (LCOE)

A measure of the average net present cost of electricity generation over a facility's lifetime, used to compare different methods of electricity generation.

M

Microgrid

A localized group of electricity sources and loads that normally operates connected to the traditional grid but can disconnect and function autonomously.

Megawatt (MW)

A unit of power equal to one million watts, commonly used to measure the capacity of power plants.

N-O

Net Metering

A billing mechanism that credits renewable energy system owners for the electricity they add to the grid, allowing them to offset their consumption.

Offshore Wind

Wind farms installed in bodies of water, typically on the continental shelf, which can generate more electricity than onshore wind due to stronger and more consistent winds.

P-Q

Passive Solar

Building design that uses the sun's energy for heating and cooling without mechanical systems, through orientation, materials, and design elements.

Photovoltaic (PV) System

A technology that converts sunlight directly into electricity using semiconductor materials, commonly known as solar panels.

Power Purchase Agreement (PPA)

A contract between a power producer and a buyer, typically a utility, which specifies the terms of electricity sale including price, duration, and delivery point.

R

Renewable Energy Certificate (REC)

A market-based instrument that represents the property rights to the environmental, social, and other non-power attributes of renewable electricity generation.

Renewable Portfolio Standard (RPS)

A regulatory mandate to increase production of energy from renewable sources such as wind, solar, biomass, and other alternatives to fossil and nuclear electric generation.

S

Smart Grid

An electricity network that uses digital technology to monitor and manage the transport of electricity from all generation sources to meet the varying electricity demands of end users.

Solar Thermal Energy

Technology that harnesses solar energy for thermal energy (heat), which can be used for heating water, spaces, or generating electricity.

Sustainable Development Goals (SDGs)

A collection of 17 global goals designed to be a blueprint to achieve a better and more sustainable future for all, with SDG 7 focusing on ensuring access to affordable, reliable, sustainable, and modern energy for all.

T

Tidal Energy

A form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity.

Transmission Grid

The network of high-voltage power lines that carries electricity from power plants to substations near population centers.

U-Z

Utility-Scale Solar

Large solar power plants designed to provide electricity to the power grid, as opposed to distributed generation for local consumption.

Vehicle-to-Grid (V2G)

A system where plug-in electric vehicles communicate with the power grid to sell demand response services by returning electricity to the grid or throttling their charging rate.

Zero-Net Energy Building

A building with zero net energy consumption, meaning the total amount of energy used by the building on an annual basis is roughly equal to the amount of renewable energy created on the site.

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