Optimizing Tidal Energy Converters

by Cassandra Burgess

In order to make tidal energy converters economic enough to compete in the energy market, it is essential to build them as efficiently as possible, but also important to design them to avoid environmental impacts on the habitats in which they are installed. These impacts can be more difficult to predict when planning an array of tidal energy converters than a single turbine. Roberts, Nelson, Jones, and James worked to solve these two problems by creating a modeling framework that optimizes the placement of tidal energy converters in Cobscook Bay, Maine. The model uses restrictions on water height and velocity based on the region so it can be applied to other regional sites as well. It also allows researchers to input environmental restrictions on the decrease in velocity due to the turbines, and on changes in the bed shear stress at the site. These constraints represent points at which the turbines might change fish behavior by causing fish to congregate in the turbine wakes, and at which erosion of the ocean floor becomes serious. Using these restraints the researchers found that the non-environmentally constrained system had an output 19% higher than the originally planned placement, and the environmentally constrained system had an output of 16% higher.

For the purposes of this modeling process the environmental constraints were set arbitrarily. In future models, research would be necessary prior to the planning of the tidal energy converters to determine what levels of change the ecosystems could reasonably withstand. Once this is determined, the model can optimize the placement of tidal energy converters while minimizing the environmental impact. This model differs from previous models because it is on a much finer scale. While previous models have been able to accurately predict the impacts of tidal energy converters on a broad scale, this model looks at the fluid dynamics near the turbines themselves. This improvement allows for analysis of the environmental impacts near the turbines, as well as for better information on the turbulence and velocity changes created, both of which affect the power output of nearby turbines. Because this model was able to optimize both energy output and environmental impact, two areas most concerning when constructing a tidal energy array, the researchers recommend that it be used in the planning for future array sites.

 

Roberts, Jesse, Nelson, Kurt, Jones, Craig, James, Scott, 2014. A Framework for Optimizing the Placement of Current Energy Converters. 2nd Marine Energy Technology Symposium, April 15-18, 2014. [GSSS: Optimization Tidal Roberts]

https://vtechworks.lib.vt.edu/bitstream/handle/10919/49219/99-Roberts.pdf?sequence=1

 

How to Reduce California’s Greenhouse Gases by 80%

by Emil Morhardt

According to the latest runs of a complex computer energy model (CA-TIMES) coming out of the University of California at Davis (Yang et al. 2015), the energy scene across California may be quite different by 2050. The model is not designed to predict what will happen, but instead to examine the economic and policy implications of just about every possible major perturbation of energy generation and use in the state to get us to the current policy goal of an 80% reduction in greenhouse gas emissions from 1990 levels. What results is a series of least-cost scenarios to get to various policy-driven energy endpoints. The bottom line is that greenhouse gas emissions can be reduced enough to meet the 80% goal at low to moderate costs, but not without major investments in wind and solar power generation, production of synthetic fuels directly from biomass using the Fischer–Tropsch synfuel pyrolysis process (more about that in upcoming posts), and hydrogen production and distribution infrastructure to power fuel cells. Continue reading