PNNL

Abstract

Unlike other renewable energy sources like wind and solar, tides are highly predictable without specialized forecasting. As a result of this predictability, tidal energy conversion technologies may become more competitive as a renewable resource that introduces less uncertainty—and thus, less volatility—into balancing the electric system. However, although predictable, tides are still a variable energy resource (VER), and the energy available to harness from them fluctuates over time and space. While VERs represent clean, non-emitting sources of power generation, their natural variation in production due to changing weather conditions and daily cycles requires generating reserves over many time intervals and volumes, for both known and unknown variations in production. In order to generate a smooth power profile from tidal resources, sufficient complexity within the timing of tides is necessary within proximity; the resource must be diverse. If these characteristics are realized, it might be possible to demonstrate tidal phase diversity for reduced periods of no or low production and for smoother power output, reducing costs to balance the electric grid compared to other resources. This study surveys areas known to have promise for tidal phase diversity by assessing time series of tidal velocities of representative locations in Alaska and Washington. This paper builds upon previously completed work that analyzed the M2 tidal constituent for the purpose of providing smoother power output through aggregation around the United States. As the most energetic tidal constituent, the M2 represented the dominant trend in the tidal velocity patterns over time, offering a first order analysis of the phenomenon. The work that follows introduces the full suite of tidal constituents from modeled data and verifies that modeled data to help identify locations where tidal resource aggregation (i.e., the sum of tidal power at a cluster of sites) can benefit the grid by minimizing the duration of time during which there is no power availability (slack tides) and producing smoother power profiles in aggregate.