NChE - Innovative Solutions Challenge:
Prompt: Tackling Air Pollution in San Diego
Proposed Solution: A wave turbine design to supplement San Diego’s power production facilities.
Currently Proposed Solutions:
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Traditional Fossil-fuel power plants run at ~40% efficiency, However increasing efficiency requires increased power input (due to process) offsetting any payoffs.
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Biomass reactors, as well as effluent and biomass digesters end up feeding methane burning power plants. While this does reduce external waste, it adds to carbon emissions in the air. (CO2 is a less potent greenhouse gas than CH4 .)
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Methane generation can be done using airborne CO2 . However, the output of this process will not produce more energy than the energy input - thus being good for methane generation, but not for power production.
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Renewables provide a cleaner power source when deployed, however, the process of making and setting up the devices required is usually intensive in material, and transport costs, but maybe this isn’t the whole picture?
Current Tidal Energy Solutions:
Tidal streams
Turbines are placed in fast-flowing streams created by the tides
Water is ~1000x denser than air → tidal energy produces more power at the same flow rate than wind
Severe environmental impact, higher output
Barrages
Operates as a large dam, effectively creating a pool or lagoon
Closes at high tide and releases water through the turbines
Very significant environmental impact, more expense, higher output
Tidal lagoons
Functions similarly to a barrage with a body of water partly enclosed by a natural or man-made barrier
Fills and empties naturally and energy can be harvested 24/7 without implicit operation
Minimal environmental impact, lower output
Drawbacks of Tidal Turbines:
Size
If they are deployed close to an active shipping route, the turbines must be small enough for a boat to pass over while still being large enough to effectively produce energy from the water.
If larger turbines are required, deployment must be far out at sea, or in a secluded area to avoid interruptions to ships/boats.
Water movement
Without sufficient water speed, Water turbines will not spin and will not produce any electricity.
The turbines need to be in shallow enough water to get the full effect of tidal movements
Noise
A large concern of underwater turbines is the possibility of disrupting natural marine life 10
Installation of turbines out at sea can take a long time and require large drilling operations for permanent installment.
Maintenance
Far-offshore turbines are difficult to maintain due to distance and depth of installation.16
Fluid leaks into the turbines can cause them to malfunction and require urgent repairs.
Proposed Turbine Solution:
The current design is limited to smaller waterways, and thus has a lower output. Scaling the project could provide new potential deployment locations and a higher power output.
Turbine Features and Manufacturing:
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Inspired by vertical wind turbines, but oriented horizontally to optimize water flow and power generation, while lowering operating depth.
The compact design allows the turbine to be transported fully assembled and thus quickly deployed.
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Lightweight composite vanes and casing with hydrophobic coatings (Dursan) to prevent erosion due to sea-water, and prevent algal buildup.
Infused epoxy and carbon fiber to construct the blades of turbine
Potential future prospect to use recycled thermoplastics or modified recyclable thermoset plastic (pDCPD) to construct turbine vanes and base.
Heavy stone bases to anchor the turbine to the seafloor, could be made with recycled building materials. (Could be replaced by a cheaper ballast configuration)
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Approximating the cost based on other known turbines and scaling it to be more in line with this design lands at around ~$200k per turbine using traditional manufacturing methods.
This cost could be reduced by larger production numbers or by substituting regular materials with recycled plastics or other material/design alterations.
Potential deployment locations to minimize environmental impact.
Schematic of the proposed turbine design. (All measurements in mm.)
Short/Long term impacts of turbine deployment.
Short Term Impacts:
The turbines are designed to be prefabricated and then hauled into position using a barge like vehicle then lowered into position via a crane.
Cabling can be installed on the turbine just prior to deployment by being trailed along the seabed.
Long Term Impacts:
Due to the turbines being installed in man-made canals and channels, energy may be harvested from the tidal currents away from routes used by marine life, thus eliminating a lot of the issues traditional tidal turbines face.
The noise and turbulence already present in the busy nautical route will overshadow any addition due to the turbines themselves, due to the proximity to the already busy area, any wiring or power transmission facilities will be non-invasive to any new native environment.
Potential Future Expansions:
Expansions:
Install more turbines within Mission Bay, San Diego
Install new turbines in Zuñiga Shoal, San Diego
Harness tide energy from ships coming through the naval base
Install wave generators close to the canals
Harness energy from the waves before the wave breaks installed around the canal opening
Improvements:
Materials
Research new approaches to using metals in sea-water, including active/passive corrosion resistant coatings.
Research plastic recycling as a viable method to clear landfills and use them as environmentally safe materials for subterranean projects
Find new areas in which to install turbines with less of an environmental impact
Explore more efficient and environmentally-friendly designs