Renewables force WECC to rethink grid operations
The Western Electricity Coordinating Council (WECC) coordinates and promotes bulk electric system reliability in the Western Interconnection, which extends from southern Canada into northern Mexico and from the Pacific Ocean to the Colorado/Kansas border. The vastness and diverse geography of the region served create unique challenges in coordinating the operation of the interconnected system and in maintaining reliable service across nearly 1.8 million mi2 (Sidebar 1).
Steve Beuning, director of market operations for Xcel Energy and chair of the WECC Seams Issues Subcommittee, spoke to the need for a paradigm shift in the way the Western Interconnection operates to satisfactorily address the challenges posed by injecting large amounts of renewable energy into the grid.
He began his presentation, “A Stakeholder’s View of the Proposed WECC Balancing Market,” with a review of Xcel Energy’s capabilities (Sidebar 2) and acknowledgement of customer demands for clean energy. Two states Xcel operates in—Minnesota and Colorado—have RPSs requiring that 30% of the kilowatt-hours come from renewables in 2020. Beuning reviewed the variability and uncertainty associated with wind and solar, citing less predictable and less controllable flows on the grid from large-scale penetration.
Another potential sticking point for grid operators is optimizing the line-up of conventional resources for backing-up intermittent renewables. There’s no standard methodology used by balancing authorities to determine the type and quantity of conventional resources required to maintain system reliability, he said. One result of this could be that overly conservative system operators might commit resources in excess of those required to balance generation and load, increasing costs and emissions.
Next, Beuning provided needed perspective on the challenge of renewables integration. By 2019, he estimated, state RPS targets in the Western Interconnection would require a minimum of 50 GW of renewable resource nameplate capacity. If those targets increase, as they have in California and Colorado recently, to an average of 27% across the WECC, wind capacity could hit 69 GW and solar 13 GW.
Those numbers themselves don’t mean much, so Beuning provided an example of the impact they could have on the grid. He cited the May 2010 “Western Wind and Solar Integration Study” prepared by GE Energy for DOE’s National Renewable Energy Laboratory as the source. He said, “At renewable production levels possible within the next decade, the state of Wyoming could have variable generating capability installed that exceeds demand variability by a factor of 57.
Traditional balancing-area methods that seek to internalize such high variability would be quite stressed, Beuning continued, adding that it wouldn’t be economically feasible to build enough gas turbines to handle the assignment.
However, data from the study demonstrate that fast intra-hour dispatch across the WECC could be used to mitigate the balancing-area challenge. Beuning pointed to a geographic diversity benefit for this approach. You spread variability over a larger area, he said. There are clouds here, sunshine there and no wind here but wind there, simulating weather patterns from the podium with his hands.
Likewise, there’s a coordinated balancing effect to working region-wide rather than within a smaller utility-controlled balancing area. It can mitigate the variability that a given plant might have to handle, thereby reducing the number of on/off cycles, steepness of ramps, etc. The market signal created allows others to respond when opportunity and price are right.
Another benefit is that the amount of local generation required to offset balancing-area variability can be reduced, thereby holding down the cost of electric service.
In general, Beuning said, in the WECC outside California, the balancing-area mindset is traditional “utility.” Specifically, operations focus on fixed hourly energy interchange (exports or imports) and all net variability is contained internally. He said that this traditional style of operation already poses significant challenges to some utilities in the Western Interconnection.
One of the behaviors of many western utilities is their fierce independence and disdain for federal “interference” in their operations. Beuning suggested that the traditional mindset in the region might have to change to accommodate large-scale renewables integration and pointed to the California Independent System Operator Inc and others as having demonstrated viable solutions.
He next summarized some of the work WECC was doing to assure a reliable, well-functioning grid in the future—such as developing what it calls an Efficient Dispatch Toolkit. First tool, the Enhanced Curtailment Calculator, already is being used on a limited basis. Its job is to allocate curtailment responsibility during congestion. Second tool is the Energy Imbalance Market (EIM), to provide fast regional dispatch of generation.
The EIM would rely on security-constrained economic dispatch of voluntary generator offers on a regional basis. Positive operational impacts expected include increased reliability and lower operation costs. Perhaps, most importantly, the EIM retains existing utility balancing areas, but achieves a “virtual consolidation” for operating purposes.
Key point: Although the EIM proposal includes a regional balancing-market function, it does not establish a regional transmission organization or a consolidated regional transmission tariff. This feature is important to several WECC utility stakeholders. The EIM as presently configured would be different than any other market footprint in the nation. Beuning said gas-turbine operators should like it because cost recovery is through a regional market rather than indirect allocations through tariffs.
A benefit/cost analysis of EIM is funded in the WECC’s budget for next year with the goal of completing the study by next summer. Open items include the need to develop a tariff for use by participating systems. Plus, a market monitor for detecting and mitigating abusive market or scheduling practices. Assuming WECC stakeholders approve the proposal, it still must pass muster with NERC and FERC.