More expensive, highly engineered, extremely low entropy collectors to grab high entropy random heat energy just won’t work (It’s SCIENCE!). This is just the offshore wind boondoggle all over again. Littering the ocean floor with wires and machines will be terrible for the marine ecosystem and we will be left wanting in the end.
Saying they can do it for $78/MWh is pure fantasy and can’t possibly include maintenance, short lifetimes, etc. Wishcasting of the highest order.
Nuclear that costs $98/MWh is a crime. It should be $1-10/MWh. Although I would bet even $98 looks good in the UK right now...
The ocean is an electrolyte solution. It corrodes metals quite aggressively. (A big difference from freshwater hydro plants.) This can be slowed by using plates made of rapid corroding metals like zinc. Zinc plates are standard on boats for this purpose. The ocean will thin plates on ships, particularly where there is vibration. Any metal object in the ocean is on a clock. The ocean is contaminated with tiny flakes of ship paint all over the world, because it's just another surface for life and chemistry to attack.
Sessile sea life colonizes anything placed in the water. If life doesn't bore into it, or grow in narrow crevices (that can start microscopic) it glues itself to the surface. Barnacles, mussels, seaweed, anemones, etc, colonize any surface. The faster the flow of water over that surface the better, as long as life can land and stick long enough to take hold. Tidal flows are perfect for this. Why? Because water flow brings nutrients and oxygen, and there are periods every day when the water is still and things can land and glue on.
There's a method from the tropics for making reinforced coral blocks fast by passing electrical current through the insulated wires in the water. They higher the voltage the better. Sea life doesn't just detect it, it uses the energy in its cells. We do the same. Our mitochondria are fuel cells that burn hydrocarbons and oxygen, putting out CO2 and water, creating an electrical potential out cells use to make ATP which is an energy currency in the cell. But life exists that harvests electricity directly. It stands to reason that something will evolve to bypass all the complex chemical processes cells use to make electric potential if there is current flowing.
FWIW- there are deep sea cold water corals, and life isn't static. Life is constantly evolving, as we have seen with this still current pandemic. If anything could evolve a coral that thrives in upper ocean cold water, it would be miles and miles of high voltage AC current cables in the ocean.
Aside from such problems, harvesting tidal and ocean current flow for energy is great. It was proposed way back in the 1950's.
You guessed right: For our tidal turbines we used cathodic protection (zinc blocks) as well as marine grade paint and anti-biofoul coatings. The zinc cathodic protection then places an upper limit on maintenance intervals.
Silt accumulation is another factor: All turbines were designed with flood and exit holes in the stator, while the rotor was fully contained, watertight and neutrally buoyant.
We also (uniquely) created a subsea electrical current management and turbine control system rather than use tower based electrical management as with most wind farms. Much respect to the electrical engineers for that one.
A few exceptions existed to the mild steel + paint + cathodic protection philosophy that forced us into more expensive materials: For example, the rotor blades needed to be removable, precision mounted and could not guarantee a conductive mount, so we were forced to use Ti64 bolts, which were obnoxiously expensive.
Swansea Bay Tidal Lagoon claims 120-year life span with no mention in the literature what the maintenance costs are, the down time, who maintains, how they're employed, what the indirect local economic benefits or otherwise are. The environmental assessment is lengthy and not readily available on the site with no clear impact of what happens to harbour porpoise and grey seal as they will be monitored after construction.
100,000 tonnes mostly UK steel (?) but no mention of the concrete or construction waste management.
Of one several damning criticisms "National Infrastructure Commission published on 11 July 2018 appears to exclude the role of any form of tidal power in the UK's future green energy mix in favour of wind, solar and electric cars based on a report by Aurora Energy Research looking at the market up to 2050. This states "Offshore wind becomes economical in the 2030s without subsidies, tidal never becomes competitive without government support" Wikipedia 03/12/2022
The real problem is energy. Hydro works because of gravitational potential energy. Typically plants have a head (height difference between forebay and tailrace) of 50-500m. The kinetic energy of even fast water flows is a small percentage of the gravitational potential energy. Some of the highest tidal flow on Earth are in the Bay of Fundy and all they have built is a lousy 20MW plant, which is tiny by conventional hydro standards. Additional problem is the intermittency of the tidal flows, a problem conventional hydro doesn't have.
More expensive, highly engineered, extremely low entropy collectors to grab high entropy random heat energy just won’t work (It’s SCIENCE!). This is just the offshore wind boondoggle all over again. Littering the ocean floor with wires and machines will be terrible for the marine ecosystem and we will be left wanting in the end.
Saying they can do it for $78/MWh is pure fantasy and can’t possibly include maintenance, short lifetimes, etc. Wishcasting of the highest order.
Nuclear that costs $98/MWh is a crime. It should be $1-10/MWh. Although I would bet even $98 looks good in the UK right now...
The ocean is an electrolyte solution. It corrodes metals quite aggressively. (A big difference from freshwater hydro plants.) This can be slowed by using plates made of rapid corroding metals like zinc. Zinc plates are standard on boats for this purpose. The ocean will thin plates on ships, particularly where there is vibration. Any metal object in the ocean is on a clock. The ocean is contaminated with tiny flakes of ship paint all over the world, because it's just another surface for life and chemistry to attack.
Sessile sea life colonizes anything placed in the water. If life doesn't bore into it, or grow in narrow crevices (that can start microscopic) it glues itself to the surface. Barnacles, mussels, seaweed, anemones, etc, colonize any surface. The faster the flow of water over that surface the better, as long as life can land and stick long enough to take hold. Tidal flows are perfect for this. Why? Because water flow brings nutrients and oxygen, and there are periods every day when the water is still and things can land and glue on.
There's a method from the tropics for making reinforced coral blocks fast by passing electrical current through the insulated wires in the water. They higher the voltage the better. Sea life doesn't just detect it, it uses the energy in its cells. We do the same. Our mitochondria are fuel cells that burn hydrocarbons and oxygen, putting out CO2 and water, creating an electrical potential out cells use to make ATP which is an energy currency in the cell. But life exists that harvests electricity directly. It stands to reason that something will evolve to bypass all the complex chemical processes cells use to make electric potential if there is current flowing.
https://en.m.wikipedia.org/wiki/Electric_bacteria
FWIW- there are deep sea cold water corals, and life isn't static. Life is constantly evolving, as we have seen with this still current pandemic. If anything could evolve a coral that thrives in upper ocean cold water, it would be miles and miles of high voltage AC current cables in the ocean.
Aside from such problems, harvesting tidal and ocean current flow for energy is great. It was proposed way back in the 1950's.
You guessed right: For our tidal turbines we used cathodic protection (zinc blocks) as well as marine grade paint and anti-biofoul coatings. The zinc cathodic protection then places an upper limit on maintenance intervals.
Silt accumulation is another factor: All turbines were designed with flood and exit holes in the stator, while the rotor was fully contained, watertight and neutrally buoyant.
We also (uniquely) created a subsea electrical current management and turbine control system rather than use tower based electrical management as with most wind farms. Much respect to the electrical engineers for that one.
A few exceptions existed to the mild steel + paint + cathodic protection philosophy that forced us into more expensive materials: For example, the rotor blades needed to be removable, precision mounted and could not guarantee a conductive mount, so we were forced to use Ti64 bolts, which were obnoxiously expensive.
Swansea Bay Tidal Lagoon claims 120-year life span with no mention in the literature what the maintenance costs are, the down time, who maintains, how they're employed, what the indirect local economic benefits or otherwise are. The environmental assessment is lengthy and not readily available on the site with no clear impact of what happens to harbour porpoise and grey seal as they will be monitored after construction.
100,000 tonnes mostly UK steel (?) but no mention of the concrete or construction waste management.
Of one several damning criticisms "National Infrastructure Commission published on 11 July 2018 appears to exclude the role of any form of tidal power in the UK's future green energy mix in favour of wind, solar and electric cars based on a report by Aurora Energy Research looking at the market up to 2050. This states "Offshore wind becomes economical in the 2030s without subsidies, tidal never becomes competitive without government support" Wikipedia 03/12/2022
The real problem is energy. Hydro works because of gravitational potential energy. Typically plants have a head (height difference between forebay and tailrace) of 50-500m. The kinetic energy of even fast water flows is a small percentage of the gravitational potential energy. Some of the highest tidal flow on Earth are in the Bay of Fundy and all they have built is a lousy 20MW plant, which is tiny by conventional hydro standards. Additional problem is the intermittency of the tidal flows, a problem conventional hydro doesn't have.
Many seaside states have a Tide Mill Rd.
Yep, the ocean just destroys man-made objects plus anything below surface is orders of magnitude in difficulty to maintain. Damn saltwater!