9.3 Generation Statistics
The energy resources in the MISO footprint continue to evolve. Environmental regulations, improved technologies and ageing infrastructure have spurred changes in the way electricity is generated.
Fuel availability and fuel prices introduce a regional aspect into the selection of generation, not only in the past but also going forward. Planned generation additions and retirements in the U.S. from 2014 to 2018 separated by fuel type shows the increased role natural gas and renewable energy sources will play in the future (Table 9.3-1).
|The increased fuel-mix diversity from the addition of the South region helps limit the exposure to the variability of fuel prices.|
The majority of MISO North and Central regions’ dispatched generation comes, historically, from coal. With the introduction of the South region, MISO added an area where a majority of the dispatched generation comes from natural gas. The increased fuel-mix diversity from the addition of the South region helps to limit the exposure to the variability of fuel prices. This adjustment to the composition of resources contributes to MISO’s goal of an economically efficient wholesale market that minimizes the cost to deliver electricity.
After the December 2013 integration of the South region, the percentage of coal units decrease as the amount of gas units increase as shown by trend lines (Figure 9.3-2).
* Based on 5-minute unit level dispatch target
Renewable Portfolio Standards
Renewable portfolio standards (RPS) require utilities to use or procure renewable energy to account for a defined percentage of their retail electricity sales. Renewable portfolio goals are similar to renewable portfolio standards but are not a legally binding commitment.
Renewable portfolio standards are determined at the state level and differ based upon state-specific policy objectives (Table 9.3-1). Differences may include eligible technologies, penalties and the mechanism by which the amount of renewable energy is being tallied.
|State||RPS Type||Target RPS (%)||Target Mandate (MW)||Target Year|
|MN||Standard – all utilitiesXcel Energy
Solar standard – investor-owned utilities
Table 9.3-1: Renewable portfolio policy summary for states in the MISO footprint
Wind energy is the most prevalent renewable energy resource in the MISO footprint. Wind capacity in the MISO footprint has increased exponentially since the start of the energy market in 2005. Beginning with nearly 1,000 MW of installed wind, the MISO footprint now contains 13,661.85 MW of wind capacity as of June 3, 2015.
Wind energy offers lower environmental impacts than conventional generation, contributes to renewable portfolio standards and reduces dependence on fossil fuels. Wind energy also presents a unique set of challenges. Wind energy is intermittent by nature and driven by weather conditions. Wind energy also may face unique siting challenges.
Capacity factor measures how often a generator runs over a period of time. Knowing the capacity factor of a resource gives a greater sense of how much electricity is actually produced relative to the maximum the resource could produce. The graphic compares the total registered wind capacity with the actual wind output for the month. The percentage trend line helps to emphasize the variance in the capacity factor of wind resources (Figure 9.3-5).