Renewable Energy and Environmental Hydrology Vocabulary

Vocabulary flashcards covering solar radiation metrics, wind turbine parameters, geothermal technologies, biomass heating values, wave energy converters, groundwater hydrology, hydropower classifications, and reservoir management.

Global Horizontal Irradiance (GHI)

The total amount of shortwave radiation received from above by a horizontal surface to the ground, combining Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DIF).

Direct Normal Irradiance (DNI)

The solar radiation received per unit area by a surface held constantly perpendicular to straight-line rays coming directly from the sun.

Diffuse Horizontal Irradiance (DIF)

The solar radiation component accounting for illumination arriving from clouds and scattered blue light from the sky.

Derate Factor

A fraction representing cumulative system losses that reduce a solar panel's nameplate rating, specific to each installation.

Pyrheliometer

A measurement instrument used to measure direct beam radiation at normal incidence.

Pyranometer

A measurement instrument used to measure total beam plus diffuse radiation on a horizontal surface.

Betz Limit

A physical restriction establishing that no wind turbine can convert more than $\frac{16}{27}$ (approximately $59.3\%$) of the kinetic energy of the wind into mechanical energy.

Coefficient of Performance ($C_p$)

A dimensionless efficiency factor representing how effectively a wind turbine captures available wind power, bounded theoretically by the Betz Limit.

Dry Steam Plants

Geothermal power plants operating at high resource temperatures ($> 200^\circ\text{C}$) where direct flow of underground steam spins the turbine directly.

Flash Steam Plants

Geothermal power plants operating at high resource temperatures ($> 150\text{ to }200^\circ\text{C}$) that use high-pressure hot water separated into steam to drive turbines.

Binary Plants

Geothermal power plants operating at lower to moderate resource temperatures ($74^\circ\text{C}$ and above) using a closed-loop system where geothermal fluid vaporizes a secondary low-boiling-point working fluid.

Higher Heating Value (HHV)

The gross calorific value of biomass including the latent heat of water vapor condensation, assuming all combustion water vapor condenses back into liquid form.

Lower Heating Value (LHV)

The net calorific value of biomass excluding water vapor condensation heat, representing practical thermal energy since combustion exhaust water remains vaporized.

Attenuator

A wave energy converter type consisting of a long multi-segment floating structure aligned parallel to wave direction that flexes as waves pass.

Point Absorber

A wave energy converter type consisting of a floating buoy that moves up and down with waves, driving hydraulic pumps or generators.

Oscillating Water Column

A wave energy converter type consisting of a partially submerged hollow structure where rising and falling water compresses and decompresses trapped air to spin a turbine.

Unconfined Aquifer

An aquifer where the upper surface (water table) is at atmospheric pressure, making it highly susceptible to drought and surface contamination.

Confined Aquifer

An aquifer bounded above and below by impermeable layers (aquitards/aquicludes), containing water under high pressure that can result in an artesian well.

Aquitard

A restrictive geological layer with low permeability that slows the flow of groundwater.

Aquiclude

A restrictive geological layer that is entirely impermeable and stops the flow of groundwater.

Zone of Aeration

A subsurface moisture zone where pore spaces contain both air and water.

Zone of Saturation

A subsurface moisture zone where pore spaces are entirely filled with water.

Large Hydro

A hydropower classification for impounding systems with capacities greater than $10\,\text{MW}$ utilizing massive dams and reservoirs.

Mini-Hydro

A hydropower classification for systems generating between $> 100\,\text{kW}$ to $10\,\text{MW}$, typically requiring grid connection and specialized operational know-how.

Micro-Hydro

A hydropower classification for systems generating $100\,\text{kW}$ and below, partially grid-connected and requiring professional know-how.

Run-of-River (RoR)

A hydropower facility type that channels natural river flow through a penstock without damming, minimizing environmental impacts.

Pumped Storage

A hydropower facility type that acts as an energy buffer by moving water between reservoirs rather than producing net energy.

Intake Structure

A run-of-river component that collects water from the forebay and directs it into the conveyance system.

Headrace

A run-of-river component consisting of a channel that carries water from the intake structure toward the turbine or penstock.

Penstock

An enclosed pipe that delivers high-pressure water directly to hydro turbines.

Head Tank (Surge Tank)

A pressure neutralizer in a hydropower conveyance system that dampens excess pressure variance.

Saltwater Encroachment

An environmental hazard caused by excessive coastal pumping, creating a cone of depression that draws denser saltwater into the freshwater lens.

Land Subsidence

An environmental hazard caused by over-withdrawal of subsurface fluids, depleting hydrostatic pressure and leading to the compaction of overlying sediment layers.

Dead Storage (Zone 0)

The lowest portion of a reservoir that cannot be drained by gravity and often accumulates sediment.

Firm Yield (Safe Yield)

An operating metric defined as the maximum amount of water consistently guaranteed available from a reservoir based on historical streamflow records.