PNNL

Abstract

The North Olympic Peninsula of Washington State is subject to frequent and often lengthy power outages due to its remote location and the topology of the distribution and transmission systems feeding its power. However, it also has ample marine energy (ME) resource potential from both tidal and wave energy. This report describes a case study feasibility analysis for the installation of marine-energy-fed microgrids located in two communities on the North Olympic Peninsula—Sequim and Port Townsend. The locations of the case studies were determined through a rigorous stakeholder engagement process, which incorporated both the interests of the communities and the proximity of ME resources. The specific sites for the microgrid within the communities were also informed by community feedback, as well as the topology of the distribution system and the location of the proposed tidal energy generators. Although wave energy was initially considered, it was not included in the analysis, as tidal resources are much stronger for the chosen case study locations. For each of the case study locations, a microgrid feasibility analysis was performed and produced several different microgrid sizes for each location, including a combination of photovoltaic (PV) and tidal resources as well as a battery and back-up diesel generation. The different sizes offer different potential benefits and would need to be weighed based on the priorities of the community, such as a desire to be independent from fossil-fuel resources, which need to be stored, or overall project installation costs. A distribution system analysis was also performed for the Sequim case study location, providing a hosting capacity analysis, an estimate of interconnection costs, and a grid-connected simulation. The hosting capacity analysis demonstrates the effect of additional renewable energy generation on the existing distribution system grid and outputs the capacity limits at which the additional generation could cause violations on the grid if mitigation strategies are not employed. For the Sequim location, the chosen microgrid location, Guy Cole Center, is located almost two miles from the proposed location of the tidal generator, at the mouth of Sequim Bay. This distance would result in significant interconnection costs if the community wanted to install a new distribution line to directly connect the tidal generator and the microgrid. As such, it is recommended that a different microgrid location is chosen if the City of Sequim wants to pursue this project or that they install a microgrid at Guy Cole Center with only PV resources, which can be located on site and would be sufficient to supply power to the building. The Port Townsend microgrid location at the wastewater treatment plant is located closer to the proposed tidal generator location. However, a distribution system analysis was not able to be performed for this site and would be necessary to make further recommendations with respect to interconnection costs. While this site has much stronger tidal resources than those for the Sequim site, there is little space available for the installation of solar panels. Thus, it is recommended to only include tidal resources in a microgrid at this location unless another nearby site is identified for solar panel installation. Both case studies provide a starting point for the communities to explore installing a microgrid to improve community resilience. Next steps would involve a more detailed design process, the acquisition of funding, and environmental reviews. This analysis could also be replicated for other communities interested in installing microgrids or extended for the same communities by exploring different buildings or even several buildings connected by networked microgrids.