ENVR 201 - Energy Systems I Flashcards

Flashcards reviewing key energy terms, units, accounting concepts, figures, and system characteristics from ENVR 201.

Primary Energy

Energy in its natural, raw form prior to any human conversion or transformation.

Final Energy

Energy delivered to the consumer's boundary following conversion and distribution.

Useful Energy

The fraction of final energy that directly performs a desired task after end-use conversion losses.

Energy Services

The end-use benefit or valuable outcome obtained from using energy (e.g., heating or mobility), measured in units other than standard energy units.

Efficiency (Energy Accounting)

A unitless energy conversion ratio $e$ constrained between $0 \times e \times 1$ (or $0 \times e \times 1$).

Efficacy

A measure centered on obtaining something valuable from energy use, rather than a unitless ratio of energy inputs to energy outputs.

Units of Energy

Units used to measure total energy capacity or work, including Joule ($J$), Calorie ($\text{Cal} = \text{kcal}$), kilowatt-hour ($\text{kWh}$), terawatt-hour ($\text{TWh}$), British Thermal Unit ($\text{BTU}$), calorie, and erg.

Units of Power

Units used to measure the rate of energy flow or consumption over time, including Watt ($W$), kilowatt ($\text{kW}$), terawatt-hours per year ($\text{TWh/year}$), and horsepower.

Human Total Energy Supply

The global rate of continuous energy supply required for human activity, equal to $19\text{ TW}$.

Solar Flux at Earth

The solar energy flux reaching Earth, equal to $1361\text{ W/m}^2$ outside the atmosphere and $0.5\text{--}1\text{ kW/m}^2$ at the surface.

Rooftop Photovoltaic (PV) Power

The typical power density produced by rooftop photovoltaic panels, equal to $150\text{ W/m}^2$.

Total Anthropogenic Radiative Forcing of CO2

The net radiative forcing increment caused by human emissions of $\text{CO}_2$, measured as approximately \text{\tt\tilde{}} 2.2\text{ W/m}^2 or $310\text{ TW}$.

2060 Primary Energy Demand Projection

A long-term projection in which total primary energy demand grows by only $\frac{1}{3}$ up to 2060, per capita primary energy peaks by 2030, and the supply mix consists almost entirely of renewables and nuclear power.

Characteristics of a Good Energy System

A high-quality energy system relies on renewable (or low-mining) sources, has low environmental impact, provides broad access (especially to electricity), and ensures reliability, resilience, high efficiency, and low cost.

Global Primary Energy Use by Source Chart

A chart showing total global primary energy supply in terawatt-hours ($\text{TWh}$) from 1800 to 2025 across fuel sources such as traditional biomass, coal, oil, gas, nuclear, hydropower, wind, solar, biofuels, and other renewables.

United States Energy Flow Diagram (2024)

A LLNL Sankey diagram showing United States total energy consumption of $94.6\text{ Quads}$ in 2024, yielding $32.34\text{ Quads}$ of energy services and $62.27\text{ Quads}$ of rejected energy.

Global Per Capita Primary Energy Use Map (2025)

A world map illustrating primary energy consumption per person in kilowatt-hours ($\text{kWh}$), highlighting variations ranging from below $1000\text{ kWh}$ per person to over $100,000\text{ kWh}$ per person.