Electrical Systems Quiz - Topic 6

Topic 6: Electrical Systems

• Topics Covered: Power system, Power Plants, Electricity Tariff, Power Factor, Power Generation, Gas Turbine Cycle, Steam Turbine Cycle, Combined Cycle and Cogeneration, Solar Thermal

• Lectures: Sept 23, 24, 26, 30, Oct 1, 3, 7, 8, 10, 14, 15

Power System

• System Load: Time intervals (daily, weekly, seasonal, annual), Usage (residential, industrial, commercial, agricultural), End-usage (lighting, air conditioning, pumping, etc.)

Load Curve

• Graphical Representation: A visual representation of electrical load (power) over time
• Energy Requirement: The area under the load curve indicates the energy needed
• Importance: Crucial for plant operation (preparation, shut-down, coordination, etc.)

Typical Load Curves

• Various examples of load curves are shown
  • Industrial plant with single shift
  • Commercial shops
  • Street Lighting
  • Urban load curve

Understand Load Curve

• Peak Load: Maximum demand (growth and capacity addition) = important factor for investment.
• Average Load: Total energy/time duration, impacts cost

System Load Factor

• Definition: Average load/peak load
• Significance: Important planning objective to increase system load factor

Capacity Factor

• Definition: Average load/plant capacity
• Applications: Total energy produced/maximum possible production, part load operation.
• Factors: Plant efficiency, operating cost, recovery potential

Load & Capacity Factors

• Load and capacity factor always ≤ 1
• Inadequate utilization of installed capacity
• Parts load operation of plant
• Impact on efficiency
• Impact on increased fuel consumption and higher cost
• Instability in rapid rate increase of load

Utilization Factor

• Definition: Peak load/plant capacity
• Purpose: Shows the extent to which plant capacity is used to meet the peak demand, important in power system planning
• Importance: Reliability of power system and capacity addition planning

Connected Load & Diversity Factor

• Connected Load: Sum of equipment ratings.
• Demand Factor: Peak load/connected load
• Diversity Factor: Sum of individual peak load/actual peak load; important for load factor improvement; inverse of diversity factor equates to coincidence factor

Power Plants: Dispatchability

• Dispatchable: Coal, natural gas, nuclear power plants (can generate and dispatch power on demand)
• Non-Dispatchable: Wind, solar (no control over generation/dispatch)
• Peak Load: Plants used intermittently (low operating costs).
• Base Load: Plants operating continuously (high capital costs)
• Intermediate: Plants with moderate capital and operating costs

Non-Dispatchable Power Plants

• Characteristics: Variable power (solar, wind).
• Factors: Production varies with resource and has low capacity factor, high capital cost.

Electricity Tariff

• Components: Maximum demand charges, Energy charges, power factor penalty/bonus rates, fuel cost adjustments, meter rentals, time of day (TOD) charges, surcharges.
• Details for various consumers: Residential, agricultural, industrial, commercial, public works

Power Factor

• Effect: Improves energy efficiency.
• Importance: Improves energy efficiency and reduces losses.
• Impact: Penalty for low power factor.

Basics of Power

• Power Terms: Active (P), Reactive (Q), Apparent (S) power
• PF: Power factor, cos(0−ψ), phase angle difference between voltage and current

Power Generation: Thermal Route

• Types: Coal, nuclear, biomass, and geothermal are dispatchable.
• Cycles: Thermodynamics cycles/working fluids

Gas Turbine Cycle

• Simple Gas Turbine: Open cycle/combustion turbine
• Analysis: Closed loop approximations/Brayton cycle (isentropic and constant-pressure heat transfer)
• Components: Compressor, combustion chamber, turbine.
• Assumptions: Air as working fluid; closed-loop cycle, constant properties of air.

Ideal Brayton Cycle

• Equations: Energy balance (Qin, Qout), temperature-pressure relationships
• Efficiency and Power: Calculations relate efficiency and power outputs to various inputs.
• Importance: Illustrates an ideal model for comparison with real-world systems.

Brayton Cycle: Modifications

• Intercooling: Cooling the compressed air between compressor stages
• Reheating: Heating the combusted gas between turbine stages
• Regeneration: Recovery of heat from the turbine exit to raise the temperature of the combustion air

Brayton Cycle: Non-idealities

• Turbine/Compressor Efficiency: Account for actual work versus ideal work.
• Pressure Drop: Consideration for pressure loss through different components.

Steam Turbine Cycle

• Rankine Cycle: Two isentropic work steps and two constant pressure heat steps; different working fluid than Brayton cycle
• Modified Carnot Cycle: Addressing two-phase fluid condensation, liquid droplet formation, and superheating the vapor.
• Additional Considerations: Superheating, deaerator effects, steam extraction and feed water heating/reheating, pressure ratios, dryness fractions.

Reheat Cycle

• Reheater: Employed between turbines, improving efficiency by increasing the heat input to the turbine (3-4 percentage point improvement).
• Optimal Pressure Ratio: Factors of 0.2 - 0.3

Regeneration Cycle

• Feed Water Heating: Steam extracted from turbines to preheat the feed water, enhancing cycle efficiency.
• Improvements: 7 - 13 feed heaters, 10 - 13% efficiency improvement.

Deaerator

• Purpose: Removes dissolved gases to avoid corrosion.
• Function: Heating, separation, and removal of dissolved gases to protect plant components.

Combined Cycle

• Multi-cycle Approach: Combines Brayton and Rankine cycles to produce more efficient power plants.
• Advantages: High efficiency, increased power output, potentially reduced cost.

Cogeneration

• Heat integration: Combined heat and power generation
• Use cases: Appropriate for situations with significant heat demand
• Industrial Application: Suitable for chemical, manufacturing facilities.

Solar Thermal/PV

• Solar Thermal: National thermal power plant testing.