THM: more complicated than you might think.
take-home messages for each sectiion
exajoule (EJ) ~ quadrillion British Thermal Units
EJ ~ 10
|2006 Energy Flow (percentages of ~100 Quads)|
|2004 Electricity Flow: 40.8 Quad BTU|
Produced electricity is 1/3 of fuels used to produce it.
Profits. Most states regulate profits as
fixed percentage of costs -- due to monopoly position
Attempts at deregulation has produced only limited saving and redistribution of suppliers.
Different use create different loads
Industrial use is predictable & sets base load.
Cyclic use, for example, due to residential and commercial uses can typically double the load at some hours.
Peak load ( >20%) arise from peaks in daily and seasonal demand. Utilities may buy power from other utilities with spare capacity.
Conclusion: Peak users pay more than cyclic users who pay more than base users.
Economy of scale is the reasonable belief that costs are not
linear in plant size: truer for plants with larger
fraction of capital costs.
Minus is that idled large plant impacts supply more than small.
Screening curves plots total cost of generating facility versus hours of operation.
Total costs include:
Capital costs: planning, construction, fees, and interest amortized over estimated lifetime of facility.
Operating expenses: fuel, salaries, maintenance.
Intercept is capital cost per installed kWh.
Slope is steeper for greater running costs.
Note: Some curves stop due to limits on sun light, average wind availability or water behind a dam.
IGCC is Integrated Gasification Combined Cycle
[(1) gasification of heavy-sulfur coal into clean gas;
(2) gas-driven generator plus waste heat used to make steam in a separate steam turbine]
Two essential elements.
Generator voltage has increased with time, typically 20-30 kV. Transmission line voltage has increased also, 300-1500 kV. So ratio of reduction in losses due to higher line voltages are 102 to 105.