U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Electricity Monthly Update
With Data for November 2016 | Release Date: Jan. 26, 2017 | Next Release Date: Feb. 24, 2017
Highlights: November 2016
- According to the NOAA, November 2016 was the 2nd warmest November on record.
- Wholesale electricity prices remained near the low end of the 12-month range at all hubs across the country due to the above average temperatures experienced throughout the country.
- For the first time since May 2016, the price of natural gas at Henry Hub was below the price of Central Appalachian coal on a $/MWh basis.
|November 2016||% Change from November 2015|
|Total Net Generation
|Residential Retail Price
|Natural Gas Price, Henry Hub
|Natural Gas Consumption
The output range of large electric coal-fired steam turbines varies widely
Large coal-fired steam turbine generators vary widely in their range of output. To follow varying demand on electric systems over time, the collective output of generators must be able to increase and decrease rapidly. The recent significant increase in generation from renewable resources, whose output varies depending on resource availability, has added another source of variation that thermal generators need to be able to respond to. As a result, the operating ranges of these generators are becoming more important.Source: U.S. Energy Information Administration, Form EIA-860, Annual Electric Generator Report
Note: Large means summer capacity greater than 100 megawatts (MW)
The chart above shows the output range of an important class of generators-large (>100 MW) coal-fired steam turbines--which represents about a quarter of the U.S. electric generating fleet. Recently, more of these generating units have taken on the role of marginal generators as a result of competition from natural gas-fired combined-cycle units. This means that the coal units are more often called on to increase and decrease their output.
The operating range of a generator is defined as the span between its summer peak capacity and its minimum load. Although the maximum output of a generator is typically set by thermal limits, the minimum value is often determined by technical factors such as mechanical and electrical instabilities, and by business considerations such as the higher operating costs associated with running a unit at lower levels of output. Anticipating the increasing importance of unit output ranges, EIA began collecting minimum load in 2013 in addition to peak capacity.
A key implication behind the minimum load of a generator is the ability to keep a unit operating when demand for power from that generator drops. If demand falls below the minimum load, the unit must shut down. For most conventional generators, repeated start-ups create significant maintenance challenges that increase operating costs and decrease equipment life. Large steam turbine units that have historically operated as baseload generators are particularly susceptible to cycling problems.
The ability of these systems to operate more flexibly, perhaps by increasing their operating range by lowering their minimum load, may be an important competitive advantage as generation from renewable resources increases.