AP Environmental Science Unit 6 Notes: Conserving Energy to Reduce Environmental Impacts

Energy conservation (APES meaning)

Reducing the amount of energy humans use (especially fossil-fuel energy) by changing technology, behavior, and systems so the same services require less energy overall.

Conservation of energy (physics law)

The principle that energy cannot be created or destroyed, only transformed; not what APES means by “energy conservation.”

Energy efficiency

Getting the same service (useful output) with less energy input (e.g., LEDs providing the same light with less electricity).

Behavioral energy conservation

Reducing energy use by changing actions or habits (e.g., turning off lights, driving fewer miles, adjusting thermostat settings).

Demand reduction

A broad category that lowers total energy demand through both efficiency upgrades and conservation behavior.

Energy production chain (life-cycle of energy use)

The linked stages where impacts occur: extraction, processing/transport, combustion/use, and waste heat losses.

Extraction impacts

Environmental harms from mining/drilling fuels, including ecosystem disturbance, water pollution risk, and land use.

Combustion

Burning fossil fuels to release usable energy; also releases air pollutants and greenhouse gases (notably CO₂).

Air pollutants from fossil fuels

Harmful emissions such as nitrogen oxides (NOx) and particulate matter produced during combustion.

Greenhouse gases (GHGs)

Heat-trapping gases released by human activities; fossil-fuel energy use commonly increases CO₂ emissions.

Waste heat

Energy lost to the environment (often as heat) rather than converted into useful work; a major source of inefficiency.

Thermal pollution

Warming of natural water bodies (often from power plant cooling discharge), which can stress aquatic ecosystems.

Power (P)

The rate of energy use; mathematically P = E/t and commonly measured in watts (W).

Energy use (E)

Total energy consumed over time; for constant power, E = P × t (often measured in Wh or kWh).

Kilowatt-hour (kWh)

A common electricity billing unit of energy equal to 1000 watt-hours.

Efficiency (formula)

Percent of input energy converted to useful output: (useful energy output ÷ total energy input) × 100%.

Electrification

Switching end uses from direct fuel burning to electricity (e.g., heat pumps, electric vehicles); benefits depend on device efficiency and the electricity generation mix.

Demand-side management (DSM)

Strategies to reduce or reshape electricity demand (especially peaks) using tools like pricing, demand response, and smart devices.

Time-of-use pricing

Electricity pricing that varies by time of day, typically higher during peak demand to encourage shifting usage.

Demand response programs

Programs where customers reduce or shift electricity use when the grid is stressed to lower peak demand.

Marginal energy source

The power plants/fuels that reduce output first when demand drops; determines how much pollution/emissions conservation actually avoids.

Rebound effect (Jevons paradox)

When efficiency lowers the cost per use, people may use more of the service, offsetting some expected energy savings.

Embodied energy

Energy used upstream to extract raw materials and manufacture a product (part of life-cycle impacts), not just energy used during operation.

Externality

A cost or benefit not included in market prices (e.g., health and climate damages from fossil fuels), which can lead to overuse of energy and underinvestment in efficiency.

Payback period

A simple economic metric for an upgrade: upfront cost ÷ annual savings; estimates how long it takes for bill savings to “earn back” the initial cost.