On September 15, 2009, the Minnesota Office of Energy Security released the results of the Dispersed Renewable Generation Transmission Study, showing that regional transmission upgrades will be necessary if there is to be continued renewable energy development in the Upper Midwest region. The purpose of the two-phase transmission study was to examine the potential in Minnesota for siting 1200 MW of dispersed renewable generation, defined as wind, solar, biomass and hydroelectric projects with a nameplate capacity of 10 to 40 MW. While the potential sites for DRG were limited to Minnesota, the study examined the regional transmission grid to determine the feasibility of DRG development, specifically considering the status of and upgrades that would be necessary for the Midwest ISO network.
Phase II of the study examined the feasibility of installing an additional 600 MW of DRG—120 MW in each of the five outstate Minnesota transmission planning zones—in 2013, without having to make upgrades to the transmission system. From Minnesota's more than 2,200 outstate transmission substations, a short list consisting of the 40 sites most appropriate for DRG interconnection was identified for the study. DRG installation at these 40 sites was then evaluated on the basis of individual site, zonal and statewide factors to determine the amount of DRG installation the transmission system could support without requiring upgrades.
Of particular significance to anyone interested in developing new renewable energy facilities in Minnesota, or in the broader MISO market, the study clearly showed that an additional 600 MW of DRG cannot be installed without significant transmission upgrades. In the site-alone analysis, only 16 of the 40 short-list locations were found to support 40 MW of DRG installation without requiring transmission upgrades. On a zonal level, two of the five outstate transmission planning zones can support 50 total MW of DRG additions, while the other three zones can each support only 40 total MW of additional DRG capacity. Statewide, however, only an aggregate of a mere 50 MW of new DRG projects can be supported. The study estimated that the cost of the regional transmission upgrades required to meet the goal of 600 MW of DRG statewide would be just over $121 million.
The Phase II study results highlight the transmission constraints that exist throughout the Midwest ISO network in general, and Minnesota in particular. Analysis of the baseline model used in the study showed a stressed transmission system already operating at design capacity in 2013. This is due to the roughly 6,500 MW of projects currently in the MISO queue with signed interconnection agreements scheduled to be online by 2013. While significant transmission projects and upgrades are scheduled for completion after 2013, these projects and upgrades will not address the lower voltage constraints that make up the majority of the limitations for DRG projects.