ESEGH flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Betz limit

The theoretical maximum fraction of wind kinetic energy an ideal rotor can extract, equal to 16/27 or about 0.593 of the incoming wind power.

Tip-speed ratio

The ratio of blade tip speed to wind speed, lambda = omega*R/v. Turbines operate near an optimal value, typically 6 to 8 for three-blade machines.

Per-unit system

A normalization method where quantities are divided by base values (Z_base = V_base^2/S_base), making per-unit impedances identical across transformer voltage levels in power flow studies.

Swing equation

The differential equation (2H/omega_s)*d2delta/dt2 = P_m - P_e relating generator rotor angle acceleration to the imbalance between mechanical and electrical power.

Surge impedance loading

The power a transmission line delivers when its reactive losses equal reactive generation, approximately V_LL^2/Z_c, typically near 400 ohms overhead.

Droop control

A governor or inverter control where frequency deviation is proportional to power change, e.g., 5% droop means full power change for a 5% frequency change.

SAIDI and SAIFI

Reliability indices: SAIDI is customer-minutes interrupted divided by total customers; SAIFI is customer interruptions divided by total customers.

PV temperature coefficient

The rate at which module power decreases per degree Celsius above 25 C STC, typically -0.3% to -0.45% per degree C for crystalline silicon.

Fill factor

The ratio of maximum PV power to the product of open-circuit voltage and short-circuit current, FF = P_max/(V_oc*I_sc), indicating cell quality.

Air mass AM1.5

The standard solar spectrum reference where sunlight travels 1.5 times the vertical atmospheric path, used for testing and rating PV modules.

Pumped storage efficiency

The round-trip efficiency of pumping water uphill and generating on release, typically 70 to 80 percent, making it the largest form of grid storage.

Coefficient of performance

The ratio of useful heating or cooling output to electrical input in kilowatts; COP approximately equals EER divided by 3.412.

Load factor

The ratio of average load to peak load over a period. Low values indicate peaky consumption and higher per-kWh delivery costs.

Affinity laws

For fans and pumps, flow scales with speed, head with speed squared, and power with speed cubed, so reducing speed cuts power sharply.

Demand response types

Price-based programs (time-of-use, real-time, critical-peak pricing) and incentive-based programs (direct load control, demand bidding, interruptible tariffs) shift or curtail load.

IPMVP options

Measurement and verification options A (retrofit isolation, key parameters), B (retrofit isolation, all parameters), C (whole facility), and D (calibrated simulation).

U-value and R-value

U-value is thermal transmittance in W/m2-K; R-value is its reciprocal. Lower U-value and higher R-value indicate better insulation.

Life-cycle assessment

A method per ISO 14040/14044 with four stages: goal and scope, inventory analysis, impact assessment, and interpretation, used to quantify environmental burdens.

Global warming potential

A factor converting a gas mass to CO2-equivalent over a time horizon; methane GWP100 is about 28 to 30 and nitrous oxide about 265 to 298.

Grid emission factor

Total GHG emissions from electricity generation divided by total generation, expressed in kg CO2e per kWh, used for location-based Scope 2 accounting.

Environmental impact assessment

A structured process of screening, scoping, baseline study, impact prediction, mitigation design, and monitoring applied before approving major projects.

LCOE formula

Levelized cost of energy equals the discounted sum of investment, O&M, and fuel costs divided by discounted energy output, giving a per-kWh lifetime cost.

Merit order effect

Low-marginal-cost renewable generation displaces higher-cost plants in dispatch, lowering wholesale electricity prices and shifting the supply curve.

Net metering vs net billing

Net metering credits exports at the retail rate; net billing credits exports at avoided cost or wholesale rate, reducing the value of behind-the-meter generation.

Feed-in tariff

A policy paying a fixed, above-market price per kWh for renewable generation over a long contract, contrasting with competitive auctions and renewable portfolio standards.

GHG Protocol scopes

Scope 1 covers direct emissions, Scope 2 purchased electricity and heat, and Scope 3 all upstream and downstream value-chain emissions.

Scope 2 dual reporting

Reporting purchased electricity emissions both location-based (grid average factor) and market-based (contractual instruments such as RECs and PPAs).

Emission calculation identity

Emissions equal activity data multiplied by an emission factor, for example kWh times kg CO2e per kWh, or liters of fuel times kg CO2 per liter.

ISO 14064-1

The standard specifying principles and requirements for organizational GHG inventories: relevance, completeness, consistency, accuracy, and transparency.

Climate risk equation

Climate risk equals hazard multiplied by exposure multiplied by vulnerability, where hazard is the event, exposure the assets at risk, and vulnerability the susceptibility.

TCFD pillars

The four disclosure pillars: governance, strategy, risk management, and metrics and targets, covering physical and transition climate risks.

SSP5-8.5 scenario

A high-emissions Shared Socioeconomic Pathway used in climate stress testing, representing fossil-fuel-intensive development and strong warming.

Stranded assets

Fossil fuel reserves or carbon-intensive infrastructure that may lose value under decarbonization policy, demand shifts, or technology change.