Sharing Low Carbon Electricity between the Pacific Northwest and California.

On September 6th Gridworks hosted our third workshop in our “Sharing Power” series, a collaboration between California, Oregon and Washington to achieve greater benefits for West Coast consumers as the resource mix on the western grid evolves to include a higher percentage of renewable resources. The workshop was attended by almost fifty people from a wide variety of public and private entities.  The focus of the workshop was a study being undertaken by the California ISO to examine the potential for increased transfers of low-carbon electricity between the Pacific Northwest and California.  At the request of the CA state energy agencies, the CAISO — working in concert with the Bonneville Power Administration (BPA) and other transmission owners — is examining the potential for:


  • Increasing the dynamic transfer capability of the AC interties between the PNW and CA,
  • Automating manual controls in support of sub-hourly scheduling on the DC intertie,
  • Increasing the capacity ratings of the AC and DC interties, and
  • Assigning Resource Adequacy (RA) value to hydro generation imports from the NW that could be shaped through the use of hydro storage capacity in the NW.



In order to determine whether or not any necessary infrastructure upgrades would be cost-effective, the CAISO will run a production simulation using the ABB Gridview model.  This modeling will help to determine whether there are sufficient resources to support any increased transfers.  The CAISO is using the WECC Anchor Data Set (ADS) for 2028 as the starting point for its resource assumptions, but is reaching out to hydro owners in the NW to obtain more detailed data about the operations of those facilities.


Gridworks convened this workshop to foster more in-depth dialogue among interested parties regarding the production simulation study.  The slide presentations from the workshop are posted on the Gridworks website. The CAISO first presented its plans and the data analysis of NW hydro production that is has undertaken to date.  Since the ADS relies on historical data from 2008-09 to represent a “typical” hydro year, it does not capture the full range of NW hydro production variation from year to year, which can vary from less than 13,000 average MW per year in a dry year to almost 20,000 average MW in a wet year.  The CAISO hopes to be able to run study cases that utilize high, low, and average hydro conditions in order to capture a range of potential outcomes.


Workshop Highlights

John Fazio of the NW Power Council described the range of NW hydro production in different types of water years and monthly variations that can occur even in years with similar water availability overall.  He noted that the water storage capabilities of the NW dams are relatively small in comparison to the annual runoff that passes through the system.  There are also many non-energy related constraints on the use of the hydro system, including flood control, endangered species protection, irrigation and navigation, which can take priority over power production.  In addition, climate change is expected to result in more rain and less snow in future years, which will tend to change the pattern of runoff to earlier in the year.


The NW Power Council has developed a model called Genesys that takes all of these constraints into account and provides, based on the volume of runoff in a given year, the monthly energy and hourly maximum and minimum generation levels available from the system.  These maximums and minimums can be used to constrain the hydro dispatch produced by a production cost model such as Gridview, or the Aurora model more commonly used in the NW.


Ryan Egerdahl of BPA followed Mr. Fazio and provided additional detail regarding the portion of the NW system controlled by Bonneville.  The participants then engaged in a lively conversation about the potential for increased beneficial exchanges of energy and capacity between the NW and CA systems.  While CA benefits from exports of surplus energy from the NW in most water years, the NW also depends on imports from CA to meet its reliability needs during its peak winter period, particularly in dry hydro years.



One of the goals of this study process is to determine whether CA can place greater reliance on the capacity and flexibility of the NW system to meet its RA requirements.  The sustainable peaking capacity of the NW hydro system is dependent upon both the amount of water in the system and the amount of time for which the capacity is needed.  For example, the sustainable capacity to provide energy output for four hours is typically much greater than would be possible for ten hours.  This suggests that NW imports can help to meet s need for power in the evening, when solar production drops off.  Similarly, returning that energy during off-peak hours can help to sustain the production capability of the NW system, particularly in drier years.  But in the springtime when heavy hydro runoff occurs, the NW system may be operating at maximum capacity much of the time, and even spilling water when the volume of runoff exceeds hydro production capacity.


These many complexities demonstrate why a high-quality study is necessary.  Following the workshop CAISO and the NW Council met the following day to discuss in greater detail the modeling techniques and necessary data exchanges to help advance the study work.  CAISO will provide preliminary results during its regular Transmission Planning Process (TPP) stakeholder meeting in November, and if all goes well, more detailed conclusions may be available by the time the 2018-19 plan is released in early 2019.  Gridworks will monitor these developments and assist wherever possible.


Beyond the specifics of this particular study, the workshops that Gridworks has convened among parties from the NW and CA have helped to foster greater mutual understanding and cooperation, and lay the groundwork for mutually-beneficial commercial transactions between the regions for years to come.