Geothermal and Hydropower Flashcards

What is the primary environmental concern associated with geothermal power plants using open-loop hydrothermal systems?

Answer: Emission of hydrogen sulfide (H₂S) gas

Open-loop hydrothermal systems release hydrogen sulfide (H₂S), a toxic gas naturally present in geothermal fluids, requiring scrubbing systems to meet air quality standards.

A run-of-river hydropower project generates electricity without a large reservoir. What is the main trade-off compared to storage hydropower?

Answer: Less predictable and dispatchable power output

Run-of-river projects cannot store water, so generation fluctuates with natural streamflow, making output less predictable and limiting dispatchability compared to reservoir-based plants.

In binary-cycle geothermal plants, what role does the working fluid (e.g., isobutane or isopentane) play?

Answer: It absorbs heat from geothermal brine and vaporizes to drive a turbine

In binary-cycle plants, a secondary working fluid with a lower boiling point absorbs heat from geothermal brine via a heat exchanger, vaporizes, and drives a turbine before being condensed and recirculated.

The penstock in a hydropower facility performs which function?

Answer: Conveys pressurized water from the forebay or reservoir to the turbine

The penstock is a large pipe or conduit that carries water under pressure from the intake or forebay downhill to the turbine, converting potential energy into kinetic energy.

Which geothermal resource type is characterized by temperatures above 150°C and is best suited for direct electricity generation?

Answer: High-enthalpy hydrothermal reservoirs

High-enthalpy hydrothermal reservoirs with temperatures above 150°C contain sufficient thermal energy to flash steam or operate binary cycles for economical electricity generation.

A pumped-storage hydropower facility consumes electricity during off-peak hours. What is the primary purpose of this operation?

Answer: To store energy by pumping water to an upper reservoir for later generation

Pumped-storage hydropower uses off-peak surplus electricity to pump water uphill, storing gravitational potential energy that is later released through turbines during peak demand periods.

What distinguishes Enhanced Geothermal Systems (EGS) from conventional geothermal power production?

Answer: EGS creates or enhances permeability in hot dry rock through hydraulic stimulation

EGS artificially creates or enhances fractures in hot dry rock through hydraulic stimulation, enabling water circulation and heat extraction in areas lacking natural hydrothermal reservoirs.