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Clean Energy Glossary

Clean Energy Made Easy

Check out our clean energy glossary and learn the terms.

Renewable energy is complex. Stay up to date with the latest terminology and definitions.

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

Terms

Definition

A


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Alternative Energy

Energy generated in ways that do not deplete natural resources, like nuclear and solar. These energy sources represent the 'alternative' to coal, oil and natural gas. Solar power is both renewable and alternative because it will always be abundant and emits no greenhouse gases. Nuclear power is alternative but not renewable since it uses uranium, a finite resource.

Atmosphere

The layer of gases that surround the surface of Earth or another planet outward into space. The density of the atmosphere increases closer to the Earth's surface due to gravity pulling the gases and microscopic suspended particles of dust, soot, smoke or chemicals inward and decreases the farther away from the Earth's surface outward toward space. – Britannica

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Battery Energy Storage

Devices that enable renewable energy to be stored with the ability to help manage your energy use by reducing your peak loads and directly powering demand when energy rates are at their peaks; increasing resiliency by powering your electric needs during a grid outage; and on a larger scale, it can help reduce the usage of plants during high times of demand and may provide additional revenue streams to customers through programs such as demand response.

Biomass

Organic waste from agricultural, livestock and lumber industry products, dead trees, foliage, etc. and considered a renewable energy source. Biomass can be used as fuel and is most often burned to create steam that powers steam turbine generators. It is also used to make transportation fuels like ethanol and biodiesel, and chemicals like pyrolysis oil that can be burned like oil to produce energy.

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Carbon Footprint

The total amount of greenhouse gases generated by an individual’s actions. Reducing your individual carbon footprint helps combat climate change, improve public health, save biodiversity and more.

CO2

A colorless, odorless, nonpoisonous gas that is a normal part of Earth's atmosphere. Carbon dioxide is a product of fossil fuel combustion as well as other processes. It is considered a greenhouse gas as it traps heat (infrared energy) radiated by the Earth into the atmosphere and thereby contributes to the potential for global warming. – EIA

Carbon Emissions

The carbon dioxide emitted from the burning of fossil fuels that cars, factories, planes and cement manufacturing produce that are harmful to the environment. They account for the largest amount of greenhouse gases and are associated with global warming.

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Dam

A barrier built to hold back water and form a reservoir to generate hydroelectricity, the first form of clean renewable energy. Duke Energy’s first power plant was a hydroelectric dam. It provided electricity to the area’s emerging textile industry and, later, the region’s growing appetite for the convenience that electricity could provide. Today, we're the second-largest investor-owned hydroelectric operator in the U.S.

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Electrification

The process of powering by 100% electricity – our goal by 2030. By 2050, renewables will be Duke Energy's largest generation source.

Emissions

The release of gases into the atmosphere, such as carbon dioxide during fuel combustion. – EIA

Energy Efficiency

The ratio of service provided to energy input as in lumens to watts in the case of lightbulbs. Services include lighting, refrigeration, heating and cooling, industrial processes and vehicle transportation. Energy efficiency offers reduction of energy use without compromising service. Also, reducing the amount of energy needed for a specific purpose or service using technology. – EIA

Environmental Attribute

The credits, benefits, emissions reductions, offsets and allowances attributable to a project or energy source, including (a) any avoided emissions of pollutants to the air, soil or water such as sulfur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO) and other pollutants; (b) any avoided emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride and other greenhouse gases (GHGs) and the reporting rights related to these avoided emissions, such as green tag reporting rights and renewable energy credits.

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Flywheel

A rotating mechanical device used to store rotational energy that can be called up instantaneously. At the most basic level, a flywheel contains a spinning mass in its center that is driven by a motor. When energy is needed, the spinning force drives a device similar to a turbine to produce electricity, slowing the rate of rotation. – ESA

Fossil Fuels

An energy source formed in the Earth's crust from decayed organic material. The common fossil fuels are petroleum, coal and natural gas. – EIA

Fuel Sources

What is used to generate the energy that is added to the grid. Across the U.S., Duke Energy owns and operates a diverse mix of regulated power plants – using fuel sources including hydro, coal, nuclear, natural gas and solar. Fuel sources can be both renewable like hydro and solar as well as non-renewable carbon-generating sources like coal and natural gas. The fuel source and generation mix for your region will impact your carbon footprint from your electricity usage.

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Geothermal

A renewable energy resource produced by the Earth's internal heat to generate electricity or heat and cool homes. There are three common types of geothermal power plants: dry steam, flash steam and binary steam. Geothermal heat pumps are a type of geothermal energy that collects and transfers heat from the ground.

Greenhouse Gases

Gases such as water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride that are transparent to solar (short-wave) radiation but opaque to long-wave (infrared) radiation, thus preventing long-wave radiant energy from leaving Earth's atmosphere. The net effect is a trapping of absorbed radiation and a tendency to warm the planet's surface. – EIA

Generation Mix

The process of producing electric energy by transforming other forms of energy; also, the amount of electric energy produced, expressed in kilowatt-hours. – EIA

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Home Charging (EV)

Electric car charging that takes place at home. Two types of residential EV chargers are in market: Level 1: standard wall outlet (120-volt) and Level 2: 240-volt outlet (dryer plug).

Hybrid

Hybrid electric vehicles are powered by an internal combustion engine and one or more electric motors, which use energy stored in batteries. A hybrid electric vehicle cannot be plugged in to charge the battery. Instead, the battery is charged through regenerative braking and by the internal combustion engine. The extra power provided by the electric motor can potentially allow for a smaller engine. The battery can also power auxiliary loads and reduce engine idling when stopped. – Energy.gov

Hydroelectric Power

The use of flowing water to produce electrical energy. – EIA

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Interconnection

Two or more electric systems having a common transmission line that permits a flow of energy between them. The physical connection of the electric power transmission facilities allows for the sale or exchange of energy. – EIA

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Kilowatt (kW) and Kilowatt-hour (kWh)

Units used to measure energy based on watts (W), which measure rates of power generated or used in a period of time. A kWh is a measure of power consumption of 1,000 watts for one hour. One kilowatt-hour is equivalent to 1,000 watts used over one hour.

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Load

An end-use device or customer that receives power from the electric system. – EIA

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Megawatts (MW) and Megawatt-hour (MWh)

Units used to measure energy based on watts (W), which measure rates of power generated or used in a period of time. A megawatt is equivalent to 1 million watts of electricity. One megawatt-hour is equal to 1 million watts used over one hour.

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Net Generation

The amount of gross generation less the electrical energy consumed at the generating station(s) for station service or auxiliaries.

Net Energy Metering (NEM)

Net metering is a billing mechanism that credits solar energy system owners for the electricity they add to the grid. A home may generate more electricity than it uses during daylight hours and if the home is net metered, the electricity meter will run backward to provide a credit against what electricity is consumed at night or other periods when the home's electricity use exceeds the system's output. Customers are only billed for their "net" energy use.

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Offset (Carbon)

A carbon offset is the reduction of 1 metric ton of CO2e from the atmosphere through projects like reforestation or wetlands restoration. These projects increase CO2 absorption and compensate for carbon emissions elsewhere.

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Power Purchase Agreement (PPA)

An arrangement where a developer installs, owns and operates an energy system, such as a solar array, on a customer’s property. The customer then purchases the system's electric output for a predetermined period. The developer is responsible for the operation and maintenance of the system for the life of the contract. Customers can enjoy all the benefits of a simple setup and turnkey operations coupled with significant cost savings, lower emissions and no operational risks.

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Renewable Energy Resources

Energy resources that are naturally replenishing but flow limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy resources include biomass, hydro, geothermal, solar, wind, ocean thermal, wave action and tidal action. – EIA

Renewable Energy Certificates (RECs)

A REC legally conveys the environmental attributes of 1 megawatt-hour (MWh) of electricity generated from a renewable energy source (e.g., solar, wind, biomass, hydro). RECs are used to track renewable energy from the point of generation to a purchaser of green power.

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Solar

A type of renewable energy that converts sunlight into electrical energy through photovoltaic (PV) panels or mirrors that concentrate solar radiation. This energy can be used to generate electricity or be stored in batteries or thermal storage. – Energy.gov

Sustainability

Meeting our own needs without compromising the ability of future generations to meet their own needs, including natural, social and economic resources and concerns for social equity and economic development.

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Transmission

An interconnected group of lines and associated equipment for the movement or transfer of electric energy between points of supply and points at which it is transformed for delivery to customers or is delivered to other electric systems. – EIA

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Utility-scale Solar

A facility that generates solar power and feeds it into the grid, supplying a utility with energy. Virtually every utility-scale solar facility has a power purchase agreement (PPA) with a utility, guaranteeing a market for its energy for a fixed term of time.

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(Electric) Vehicles

Vehicles that run on battery power instead of gas and do not burn carbon emissions. There are three major types of EVs: all EVs, plug-in hybrid EVs and fuel cell EVs. Transportation is the primary source of greenhouse gas emissions in the United States, accounting for 27% in 2020, and decarbonizing the transportation sector by switching to EVs will be critical to meeting net-zero carbon goals.

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Wind Energy

A sustainable form of electric generation that mostly uses a wind turbine to convert kinetic energy of wind into electrical energy to generate electricity. There are three major types of wind energy in the United States: utility-scale wind, off-shore wind and distributed, or “small,” wind. Duke Energy Renewables generates about 2,300 megawatts of wind power at 21 wind farms across the country, providing enough zero-carbon energy to power more than half a million homes.

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Zero Emissions

Energy sources that do not emit any waste or harmful products that pollute the environment or disrupt the climate. Duke Energy plans on being carbon free by 2050.