Sustainability & Renewable Energy (Lectures 1–6) Flashcards

What are the three main parts of a power system?

Generation, Transmission, and Distribution.

Why are power plants often built far from populated areas?

To be closer to fuel sources and reduce logistical costs.

What are the three main fossil fuels used for power generation?

Coal, Oil, and Natural Gas.

What is natural gas mostly composed of?

Methane (CH₄).

How are oil and gas transported to power plants?

Pipelines, ships, or rail.

Describe the basic power plant cycle.

Boiler → Turbine → Generator → Condenser.

What creates a vacuum in the condenser?

Cooling water lowers turbine exhaust pressure for better efficiency.

Typical main boiler steam conditions?

~2400 psi, 340°C; Superheated ~565°C; Reheat ~535°C at 550 psi.

What is the main function of a steam turbine?

Convert steam thermal energy into mechanical energy.

How is grid frequency maintained?

Turbine governors adjust steam input to maintain 50 Hz.

What is fly ash?

Fine ash particles carried away by flue gases.

What percentage of a plant’s cost is pollution control?

About 40% of plant cost, and ~5% of total power generated.

Name an advantage of gas turbines.

Fast start-up/shutdown and modularity.

What is a combined-cycle plant?

Uses both gas and steam turbines for ~56–58% efficiency.

How is voltage induced in a generator?

Moving a conductor through a magnetic field.

Formula for generator frequency?

f=(P×N)/120 where P=poles, N=rpm.

Main producer of electricity in power systems?

Synchronous machines.

Two rotor types?

Cylindrical (high speed, steam turbines) and Salient-pole (slow, hydro turbines).

What is ACSR?

Aluminum Conductor Steel Reinforced, used for transmission lines.

Main advantage of AC transmission?

Easy to step voltage up or down with transformers.

Define base load.

Minimum continuous demand served by efficient baseload plants.

Define spinning reserve.

Extra generator capacity running below max output, ready for sudden load.

Define Distributed Generation.

Small-scale generation near loads, often renewable or flexible.

Motivations for DG?

Lower costs, less transmission loss, improved reliability.

Advantages of diesel generation?

High efficiency, quick installation, scalable, good at low load.

What is turbocharging?

Increasing intake air pressure to improve engine performance.

Name three CSP types.

Parabolic trough, Solar dish/Stirling, Power tower.

Typical efficiency of biomass power plants?

Less than 20%.

What are Pelton, Francis, Kaplan turbines used for?

Pelton (high head), Francis (medium), Kaplan (low head, adjustable pitch).

General reaction in a fuel cell?

H₂+O₂ → H₂O+electricity

Name 3 fuel cell types.

PAFC, PEMFC, SOFC (Molten carbonate and Alkaline also exist).

What is NPV?

Net Present Value, compares project costs over time with discounting.

IRR meaning?

Discount rate where NPV = 0, comparable to investment returns.

Declining vs Inverted Block Rates?

Declining: cheaper with higher demand; Inverted: more expensive for higher use.

Why use time-of-use rates?

Encourage shifting loads off-peak.

Peak clipping definition?

Reducing peak load by direct control of appliances.

Valley filling?

Using off-peak energy to raise load factor.

Solar constant value?

~1.377 kW/m².

Earth’s tilt angle?

23.5°.

Solar noon definition?

When Sun is directly over local meridian.

What adjustments are needed?

Longitude adjustment, equation of time, daylight savings.

Name three types of solar radiation hitting collectors.

Direct-beam, diffuse, reflected.

What does a pyrheliometer measure?

Direct beam radiation.

Pyranometer?

Measures total usable solar radiation.

What is the photovoltaic effect?

Light-induced voltage in a material.

Who discovered PV effect and when?

Edmond Becquerel, 1839.

Band gap meaning?

Energy needed to excite an electron from valence to conduction band.

What is doping?

Adding elements to silicon to create n-type or p-type material.

What forms the basis of a diode?

A p-n junction.

What is the depletion region?

Zone at junction with no free carriers; forms an electric field.

Series vs parallel wiring effect?

Series ↑ voltage, parallel ↑ current.

Why is MPP important?

Ensures PV operates at maximum efficiency despite varying sunlight.

How does shading one cell affect a module?

Can reduce output by ~2/3.

Purpose of bypass diodes?

Prevent hot spots and allow current bypass in shaded cells.

List thin-film PV materials.

Amorphous silicon, GaAs, CdTe, CuInSe.

Three PV system configurations?

Grid-connected, Stand-alone, Directly coupled.

Key advantage of direct coupling?

Simplicity and reliability (e.g., water pumping).

Difference between STC and PTC?

STC: lab conditions (25°C cell, AM1.5, 1 sun);
PTC: field conditions (20°C ambient, 1 m/s wind).

What reduces real PV performance?

Temperature, wiring, dust, shading, inverter inefficiency.

Rule for sizing fuses and disconnect switches?

Rated for 1.25× expected voltage and current.

What does BOS include?

All components besides PV panels (wiring, mounting, labor).