AHC/WI: Offshore Electricity Production

Delta Force

Banned
This is not about marine energy (tidal, wave, and wind), but about building conventional and nuclear thermal power stations offshore.

The earliest proposals for this emerged in the 1950s and 1960s and involved placing nuclear reactors on barges or ships to supply energy to ocean and river communities. In the 1970s the Offshore Power Systems concept was developed, which would have gotten around the issue of NIMBYism by putting nuclear reactors on artificial islands several miles offshore, which would reduce the number of people potentially at risk from a nuclear incident. There's also Flexblue, a recent proposal which involves placing commercial derives of naval propulsion reactors on the ocean floor to power coastal communities.

Most proposals have been based around nuclear energy, but I'm wondering if it could be feasible for conventional power stations as well. Radiation was becoming an issue in the 1970s, but so was air pollution. Prior to the development of advanced smokestacks and emission filters, the pollution from conventional power plants tended to be heavy, but it was localized.

In terms of locations, the continental shelf would be ideal for fixed infrastructure. It tends to be no deeper than 200 meters (490 feet) and typically extends 80 kilometers (50 miles) offshore. It would also be possible to simply use power barges or ships. Power could be transmitted by an undersea cable.

Could going offshore have been a feasible response to the requirements for extensive pollution controls and public safety studies for new conventional and nuclear power stations? If thermal power stations were built offshore, could it help the development of other marine power systems such as tidal, wave, and wind systems?
 
I think offshore thermal is an excellent idea. I'm seeing perhaps one drawback: delivery of fuel. Are there colliers leaving major ports? Or tankers tying up? Or oil/gas pipelines?

With that in mind, & given onshore wind is steady & strong, IMO offshore windfarms make the most sense. Place them just beyond the horizon visible from shore & out of shipping lanes. The good thing about this is, they can be sited on large interior bodies of water, like the Great Lakes, Lake Winnipeg, Great Bear & Great Slave, & elsewhere, too.:cool:
 

Delta Force

Banned
I think offshore thermal is an excellent idea. I'm seeing perhaps one drawback: delivery of fuel. Are there colliers leaving major ports? Or tankers tying up? Or oil/gas pipelines?

With that in mind, & given onshore wind is steady & strong, IMO offshore windfarms make the most sense. Place them just beyond the horizon visible from shore & out of shipping lanes. The good thing about this is, they can be sited on large interior bodies of water, like the Great Lakes, Lake Winnipeg, Great Bear & Great Slave, & elsewhere, too.:cool:

It would probably depend on the location. In the Gulf of Mexico, North Sea, Caspian Sea, Bohai Bay, Persian Gulf, and other areas with natural gas, some or all of it could simply be sent by pipeline to offshore power stations. Colliers could be used to deliver coal, and it's likely only a small fleet would be needed because ships can carry far more coal than trains. Petroleum would be more difficult because it would need refining prior to use.

Because transmission infrastructure would already be in place, marine energy could benefit from improved access to the grid. They could supplement or replace coal generation as it becomes more regulated and less economically competitive, and potentially power lines operating at reduced capacity due to offshore natural gas field depletion.
 

trurle

Banned
Not feasible until the land cost become prohibitive. Artificial islands construction is expensive ($2000/m2 typical), and ships are simply not large enough (the conventional 1GW coal-burning power plant is about 100kt, not including coal (9 kt per day). Can be built lighter, but with increased maintenance which mean more expensive electricity.

https://en.wikipedia.org/wiki/The_World_(archipelago)
 
Not feasible until the land cost become prohibitive. Artificial islands construction is expensive ($2000/m2 typical), and ships are simply not large enough (the conventional 1GW coal-burning power plant is about 100kt, not including coal (9 kt per day). Can be built lighter, but with increased maintenance which mean more expensive electricity.
100,000 tonnes on a ship or barge is easy; fuel supply wouldn't be prohibitive, in much of the world it comes by sea anyway. It would be relatively straightforward to design a barge that could accommodate a 1,000 MW coal-fired plant and a 30 day supply of coal. It would wind up a similar size to some of the larger FPSOs used for offshore oil & gas production.

Berthing arrangements to allow a collier to come alongside would be the hangup. For FPSOs they get quite involved, and liquid hydrocarbons can be pumped. Handling solid fuel would be a pain in the backside in anything above a flat calm.

Offshore nuclear removes the fuel supply problem almost entirely, and has a lot to recommend it. The big advantage for offshore power plants is that you can set up a single facility and build them production-line style instead of having to set up a new workforce, and accomodation for them, at each new power plant. With the fixed site, you can have specialised facilities and a skilled workforce and reap economies of scale.
 
.... onshore wind is steady & strong, IMO offshore windfarms make the most sense. Place them just beyond the horizon visible from shore & out of shipping lanes. The good thing about this is, they can be sited on large interior bodies of water, like the Great Lakes .... & elsewhere, too.:cool:[/QUOTE]
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NIMBY politics can be the biggest obstacle to new technology. For example, a few years back I was involved with a risk analysis study for some projected wind turbines along the (dry) North Shore of Lake Erie, Ontario. Local politics turned so viscous that I withdrew after the first phase of analysis.
Before I withdrew, I suggested building wind turbines in shallow water a few hundred metres off-shore. Lawyers replied: "Sorry, but that is considered 'navigable waters' and construction is forbidden."
Hah!
That shore has such a shallow slope that the only boat that can sail within a kilometre of that shore is a canoe!
Apparently the rules were written back when canoes were the primary means of transportation and recreational canoeists have stubbornly resisted any infringement on their recreational waters.
 
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Because it's extremely capital intensive, never been demonstrated at an industrial scale, and doesn't work at all on most of the planet.
Actually, someone made a very good point about OTEC a while back that I've been wondering about since. There are a significant number of tropical islands where a substantial proportion of the energy demand is in the form of coolth for hotels. This is usually provided (very expensively) by air conditioning, often powered by diesel generators since the islands are usually not big enough to pay for a more complex power station.
Now in a situation where you build an OTEC plant this makes it a lot more viable than just a source of electricity: the cold water itself helps you avoid very significant electrical demand and once the pipe has been laid it can be brought to the surface very cheaply. Where air conditioning might represent a large fraction of your electrical demand, this makes OTEC plants very substantially more economic than they would be just as a source of electricity.
 
Delta Force said:
supplement or replace coal generation as it becomes more regulated and less economically competitive, and potentially power lines operating at reduced capacity due to offshore natural gas field depletion.
I'm taking you to mean not using coal offshore, & using natural gas or wind, instead.
trurle said:
Not feasible until the land cost become prohibitive. Artificial islands construction is expensive ($2000/m2 typical)
I'm imagining something closer to an offshore oil rig than an artificial island--or just a series of offshore wind turbines, like Denmark has already built (without cost becoming prohibitive).
RLBH said:
100,000 tonnes on a ship or barge is easy; fuel supply wouldn't be prohibitive, in much of the world it comes by sea anyway. It would be relatively straightforward to design a barge that could accommodate a 1,000 MW coal-fired plant and a 30 day supply of coal. It would wind up a similar size to some of the larger FPSOs used for offshore oil & gas production.
A 300-500Kt supertanker conversion wouldn't be out of the question; my question is, does this have the stability in wave action of a fixed platform? Wouldn't that create problems with either the power cable ashore, or the fuel feed pipeline (if any)?
RLBH said:
Offshore nuclear removes the fuel supply problem almost entirely
It does create issues of contamination from nuclear materials you don't get from wind.

Something else to consider: if these offshore stations are like oil rigs, & are permanent, does this have spinoffs for things like oceanography? (I'm picturing using the rig as a "dive camp".) Does it encourage development of ocean thermal conversion?
RLBH said:
doesn't work at all on most of the planet.
Actually, if designed correctly, it works in a surprising number of places. The deep water requirement is to get the delta-t from ocean surface; in Arctic/Anarctic latitudes (I'm thinking northern Labrador, Hudson Bay, Great Slave/Bear {again...}, Kamchatka, northern Norway, south coast of Alaska, Aleutians), the seawater-to-atmosphere delta-t is higher than than the "traditional" deep-water OTC.
 
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gas or oil fired stations could be built 'at the well head' and transmit the power ashore by cable rather than piping the gas / oil ashore ...

particularly if the gas fired stations were gas turbine plant ...
 
zippy said:
gas or oil fired stations could be built 'at the well head' and transmit the power ashore by cable rather than piping the gas / oil ashore ...

particularly if the gas fired stations were gas turbine plant ...
That makes a lot of sense.:cool:

And we're back to the OTC model: an offshore permanent rig with need for quite large onsite crewing & quite large footprint. This could "anchor" oceanographic research, kelp farming, ocean mineral extraction, dive tourism...
 
gas or oil fired stations could be built 'at the well head' and transmit the power ashore by cable rather than piping the gas / oil ashore ...

particularly if the gas fired stations were gas turbine plant ...
Problem is that gas pipelines are a good bit cheaper and easier to lay than HVDC cables - and maintenance costs are much lower for the plant when onshore than offshore. The difference is pronounced enough that power-to-gas has been seriously suggested as a way to get the output of the more remote offshore wind farms back to land.
 
I'm taking you to mean not using coal offshore, & using natural gas or wind, instead.

I'm imagining something closer to an offshore oil rig than an artificial island--or just a series of offshore wind turbines, like Denmark has already built (without cost becoming prohibitive).

A 300-500Kt supertanker conversion wouldn't be out of the question; my question is, does this have the stability in wave action of a fixed platform?
With the mooring system designed right, a floating platform can be plenty steady enough for industrial operations. There are a fairly substantial number of them out there, and there are plausible concepts for moored offshore wind turbines.

I wouldn't start with a supertanker, though, at least not for coal. Maybe a bulk coal carrier, if one were available cheaply, but really I'd prefer a clean-sheet design. Oil or gas, shipping the fuel onshore would be cheaper. For combustion power, this only comes close to economic sense if you're depending on imported coal or want to simplify siting for nuclear power plants.

Wind is a slightly different animal, of course, and the case for building turbines offshore is as good as the case for building them at all.
Wouldn't that create problems with either the power cable ashore, or the fuel feed pipeline (if any)?
Not really - risers for cables and fluids are proven technology. Requires a bit of attention in the design, but anyone operating offshore oil and gas platforms knows how to do it.

So far as oceanography goes, ROVs operating in certain North Sea/West of Shetland oilfields spend their time between maintenance jobs exploring the seabed and studying marine life. One of the Scottish universities came up with the scheme, it costs the oil companies next to nothing, and the ROV operators apparently find it a pleasant change from their usual work.
 
RLBH said:
With the mooring system designed right, a floating platform can be plenty steady enough for industrial operations. There are a fairly substantial number of them out there, and there are plausible concepts for moored offshore wind turbines.
Fair enough.
RLBH said:
I wouldn't start with a supertanker, though, at least not for coal. Maybe a bulk coal carrier, if one were available cheaply, but really I'd prefer a clean-sheet design. Oil or gas, shipping the fuel onshore would be cheaper. For combustion power, this only comes close to economic sense if you're depending on imported coal or want to simplify siting for nuclear power plants.
I had the large size in mind, an adaptation of the basic hull form, rather than a refit of an already-completed ship. Unless we're talking about using oil or natgas, in which case a "wellhead" power station makes more sense.
RLBH said:
Wind is a slightly different animal, of course, and the case for building turbines offshore is as good as the case for building them at all.
Slightly better IMO: less chance of NIMBY impact, better prospects for steady wind (which is better for power purposes).
RLBH said:
Not really - risers for cables and fluids are proven technology. Requires a bit of attention in the design, but anyone operating offshore oil and gas platforms knows how to do it.
Fair enough.
RLBH said:
So far as oceanography goes, ROVs operating in certain North Sea/West of Shetland oilfields spend their time between maintenance jobs exploring the seabed and studying marine life. One of the Scottish universities came up with the scheme, it costs the oil companies next to nothing, and the ROV operators apparently find it a pleasant change from their usual work.
I wasn't thinking only of repurposed ROVs. I had in mind dedicated oceanographic research teams, including divers & minisubs of their own. I also anticipate dive tourists, & the prospect for kelp farming (among other things).
 

Delta Force

Banned
Could the concept be used for a sea launch rocket concept, with the power station producing fuel for the rocket through electrolysis? What about building a small LNG plant to fuel the rocket from a natural gas field?
 
What about building a small LNG plant to fuel the rocket from a natural gas field?
That's what FPSOs do. The first LNG FPSO is currently being built, and it's huge - 488 metres long, 74 metres wide, and displacing 600,000 tonnes. Miniaturising it any further would be extremly difficult. You'd need a pretty high flight rate to justify one purely off the back of rocket launches.
 
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