ENVR 201: Energy Systems I

Vocabulary practice flashcards covering fundamental definitions, scales, accounting principles, and figures from Energy Systems I.

Energy Units

Units used to measure energy quantity, including Joules ($\text{J}$), Calories ($\text{Cal} = \text{kcal}$), kilowatt-hours ($\text{kWh}$), Terawatt-hours ($\text{TWh}$), British Thermal Units ($\text{BTU}$), and ergs.

Power Units

Units used to measure the rate of energy flow or work done per unit of time, including Watts ($\text{W}$), kilowatts ($\text{kW}$), Terawatt-hours per year ($\text{TWh/year}$), and horsepower.

Primary Energy

Energy in its initial form found in nature before undergoing any human-engineered conversion or transformation process.

Final Energy

Energy delivered to the end consumer (such as electricity at a wall outlet or gasoline at a pump) prior to final end-use conversion.

Useful Energy

The net energy available to perform intended work after accounting for energy lost during final end-use conversion processes.

Energy Services

The ultimate benefits or valuable outcomes obtained by consumers using energy, measured in non-energy units (e.g., lighting, mobility, or comfortable indoor heating).

Efficiency (Energy)

A unitless conversion ratio bounded between $0 \le e \le 1$, defined as the proportion of input energy that is successfully converted into useful output energy.

Efficacy (Energy)

A measure centered around obtaining a specific valuable or desired outcome through the utilization of energy.

Solar Flux at Earth

The rate of solar radiation energy per unit area reaching Earth, equal to $1361\,\text{W/m}^2$ at top of atmosphere and $0.5\text{--}1\,\text{kW/m}^2$ at Earth's surface.

Rooftop PV Power Density

The electric power output generated per unit area of rooftop photovoltaic panels, equal to $150\,\text{W/m}^2$.

Human Total Energy Supply

The rate of global primary energy consumption across all human society, equal to $19\,\text{TW}$.

Total Anthropogenic $\text{CO}_2$ Radiative Forcing

The net rate of heat energy added to Earth's climate system by human carbon dioxide emissions, equal to approximately $\sim 2.2\,\text{W/m}^2$, or $310\,\text{TW}$ globally.

2060 Primary Energy Demand Projection

The projection that global primary energy demand will grow by only $\frac{1}{3}$ up to 2060, with per capita primary energy peaking by 2030.

2060 Energy Mix Vision

A long-term vision in which global energy inputs consist almost entirely of renewable sources plus nuclear power, with a minimal possible remainder of $\text{CH}_4$.

Global Primary Energy Use by Source

Historical measurement in terawatt-hours of global primary energy supply categorized by sources such as traditional biomass, coal, oil, gas, nuclear, hydropower, wind, solar, biofuels, and other renewables.

United States Energy Consumption Flow (2024)

A Sankey flow diagram mapping total US energy supply ($94.6$ Quads) through electricity generation, sector demand, resulting energy services ($32.34$ Quads), and rejected energy ($62.27$ Quads).

Primary Energy Use Per Person (2025)

A global distribution map measuring primary energy supply per person in kilowatt-hours across different geographic regions.