The Western Electricity Coordinating Council (WECC) is in the midst of a years-long effort to better address uncertainties in its long-range planning studies, and a new report from Johns Hopkins University provides some guidance on how to take a different approach to transmission planning, Byron Woertz, manager of system adequacy planning at WECC, told TransmissionHub Feb. 10.
The use of stochastic programming to analyze different power grid scenarios can produce results that are quite different than single case study models, or the deterministic approach, that has been the norm for transmission planners for years, Woertz said.
Going back a few years, WECC decided it wanted to better address some of the industry uncertainties in its long-range planning studies, and the Feb. 3 report was undertaken in response to that, Woertz noted. The use of stochastic programming, or a probabilistic approach, is designed to give WECC a better understanding of how different scenarios can affect the transmission system, he said.
“We just started down this path and we’re still learning how to apply it,” Woertz said.
The report compares economic modeling techniques and concludes that a stochastic approach would produce a power grid that is better able to account for different unknowns than traditional deterministic models. The interaction of generation changes and the transmission system is not well addressed in current long-range transmission planning, the report said.
With so much uncertainty in the energy sector based on fuel prices, environmental rules, declines in load growth and a proliferation of clean energy technologies, the value of transmission can change quite a bit over time, the report said.
“Depending on what happens in the future, transmission facilities added today may provide far more value than planners anticipate, or may turn out to be costly stranded assets,” the report said. “But it is unrealistic to just wait and see what happens before committing to build, because delays in realizing the benefits of stronger interconnections can also be costly.”
Stochastic planning can result in a transmission network that is more adaptable in the face of all uncertainties, not just those that were included as specific scenarios under a deterministic approach, according to the report. Stochastic planning can produce a diverse set of network investments so that in 10 years, the grid is positioned to respond to whatever load, price, technology and policy scenario occurs, with cost savings compared with “suboptimal” planning, or building the “wrong” transmission lines, the report said.
The cost savings of using stochastic planning rather than case study models “can be as much as or even exceed the cost of the recommended transmission facilities themselves,” the report said. A base case approach from WECC’s 2013 Transmission Expansion Planning Policy Committee (TEPPC) produces costs that are about $11.7bn higher than the stochastic approach based on equal probabilities, the authors noted.
“We recommend that WECC consider implementation of a stochastic model as part of its next planning cycle in order to build confidence that near term (year 10) transmission reinforcements will contribute to an adaptable and robust network,” they said.
“I think we’re doing that” as part of the TEPPC process and the development of WECC’s study program for 2016, Woertz said.
As TransmissionHub reported, the TEPPC received comments from stakeholders during an open season comment period that ended Feb. 1, as part of its process to come up with a study program.
A draft study program is expected to be posted for stakeholder review in April, and because that program will be based on stakeholder input, it likely will not incorporate a stochastic modeling approach, Woertz said.
Once the TEPPC reviews the comments and crafts the study program, it may take a case study and do the same study using a stochastic approach to show stakeholders how it would work so they can have a “side by side” comparison of the different approaches, Woertz said.
By the end of 2016, WECC staff expect to prepare a report on planning activities and submit it to the WECC board, he said.
The challenge in taking the stochastic approach is that it can produce results that are not intuitive based on traditional planning models, Woertz said.
Grid planners may conduct six studies and each one comes up with a different set of needs for more transmission based on the scenarios examined, but there may be one common set of transmission plans among the six studies, he explained. Under the traditional, deterministic approach, that common set of plans is the optimal solution and would be recommended.
But using a stochastic approach, “you might end up with projects that do not show up in any of the six studies,” he said.
Woertz said WECC will work to incorporate stochastic modeling as part of its study program, but he emphasized that WECC does not have authority to see that the program is implemented or make recommendations for building certain projects.
Following a 2014 bifurcation of WECC, with Peak Reliability formed to be the reliability coordinator for the Western Interconnection, WECC focuses on reliability monitoring and enforcement as well as performing transmission planning and performance assessments of the Bulk Electric System in the Western Interconnection.
WECC “does not have the authority to tell anyone to build anything,” but it develops information to share so that market participants can make good decisions, Woertz said.