EESC 119: Energy Vocabulary

Energy

the capacity to do work (units: joules, British Thermal Unit, KiloWatt Hour)

Power

the rate of energy consumption or production (energy / time) (measured in Watts)

• 1 W = 1 J/s

Primary Energy

Energy in the form in which it is found in the environment, before conversion

• Coal

• Crude oil

• Natural gas

• Waste

• Wind

• Biomass (wood)

Secondary energy

Energy that has been converted to a more useful state for consumption (ex. electricity, gasoline)

Energy density

Energy per unit of mass 

Power density

rate of energy [production or use] PER AREA

Capacity (electricity generation)

rate at which a facility can generate electricity at its maximum output (100%)

Capacity factor

= electricity actually generated / electricity generated when operating at full capacity

nuclear is highest; solar PV is lowest

Energy efficiency

useful energy out / energy input; will always be below 100% because energy is required for conversions

System energy efficiency

overall system efficiency = product of the individual efficiencies of each stage

Centralized generation system

large scale generation unit -> transmission network -> distribution network -> individual consumers

intermittent

not continuously available due to natural variability (solar and wind)

dispatchable

turn it on when you want; output exactly when it is needed; controllable

load

electricity demand

baseload

constant energy demand (geothermal, coal, nuclear)

peaking power

power that you can turn on when demand spikes (natural gas and hydro) - able to be turned on and off easily

Energy Return on Investment (EORI)

= energy output / life cycle energy in = lifetime energy out / lifetime energy out (unitless)

⭐if __ goes down, one needs more energy to get that same amount of the resource

hydroelectric has the highest

Levelized Cost of Energy (LCOE)

= Total money spent / lifetime E delivered = $ / MWh (megawatt hours) - average price of electricity for a generator over its lifetime

Life Cycle Assessment

evaluates the environmental impacts of a product or service across its entire life cycle, from raw material extraction to the end of life

• single impacts: GHGs, water use, affordability

• multiple impacts: sustainability

residence time

how long a molecule spends in the atmosphere before being converted into something else

vulnerability

the propensity or predisposition to be adversely affected

adaptation

adjusting to expected changes in climate (biodiversity, climate resilient buildings + infrastructure)

mitigation

reducing emissions and enhancing the sinks (transportation, vehicle electrification, home + building efficiency, industry efficiency, local energy generation, circular economy)

Carbon Direct Removal Strategies

• Ocean fertilization -> increased photosynthesis to remove carbon -> concern over disrupting ecological balance

• Reforestation

• Direct air capture

• Reforestation

• Macroalgal cultivation - seaweed (to take up CO2 and then use it as biofuel or other products)

R/P Ratio

estimate of how long the supply will last (reserves / production)

• R = million gallons

• P = million gallons / year

• Influenced by new discoveries, new tech, and changing production rate