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Is there any resources regarding wind turbines as electricity generators for propulsion? I imagine this could work pretty well, maybe even with headwind (?), o

Is there any resources regarding wind turbines as electricity generators for propulsion? I imagine this could work pretty well, maybe even with headwind (?), owning to the different densities (and inertia) of water and air, as well as their relative velocities. Yet everyone I've told this to called me nuts, likening this to perpetual motion, etc. I'd likely go with hydrogen storage for boats, especially if the system is reversible (though I've read it can be quite difficult to filter input water).

Gwypaas 7y ago
I think the problem is the efficiency, a wind turbine is limited to about 60% by Betz law[0] and most today seem to have 35-45% efficiency. Which means with all losses included I think it's hard to see a headwind helping, same with how the apparent wind shifts forward, which would make a weak stern wind not help anything and the turbine just be drag. They are making trials with wind "turbines" using the magnus effect[1], they seem to save about 300 tons of fuel per year, but since the article doesn't include the ships yearly total amount it is hard to put it into a relation to anything. https://safety4sea.com/tests-from-rotor-sail-technology-on-viking-grace-indicate-savings/ https://safety4sea.com/tests-from-rotor-sail-technology-on-v... I think ships is one of the applications where hydrogren could be feasable. Batteries are hard when you have to have the range from China to Europe or NA without stops and the density of hydrogen could maybe solve that. Especially since compared to cars the distribution network is more easily centered around large harbours and routes which is already used to handling dangerous goods. Though the competition is going to be synthetic hydrocarbons and all they need are producers, the entire world is already devoted to transporting them. [0] https://en.wikipedia.org/wiki/Wind_turbine https://en.wikipedia.org/wiki/Wind_turbine [1] https://en.wikipedia.org/wiki/Magnus_effect https://en.wikipedia.org/wiki/Magnus_effect
mojomark 7y ago
The idea is not perpetual motion as long as you're not trying to extract energy for propulsion directly from a head wind. You could, however, certainly use a wind turbine to store energy while not underway (e.g. while in port trabsferring cargo or at anchor) and then use that energy to propel against a headwind later. (I'm a marine engineer and work on ship propulsion system design, specifically WRT energy efficiency of propulsion systems.) The challenge with a hybrid wind turbine-electric propulsion would be the energy efficiency losses from turbine generator through a power conversion (and probably storage) device and ultimately the propulsion motor. By the time you're finished, it probably would have been more practical to use some type of sail to harvest wind energy for propulsion directly with no losses. For a head wind, your wind turbine would be harvesting energy, but it would also be creating significant air drag which would be added to the total resistance of the vessel, so the sum total of propulsive power would be negative in a direct head wind scenario. Interstingly, the opposite is true for a tail wind - that is you'll be gaining thrust (like a sail) in addition to harvesting some of that energy. Again, though, because of the energy conversion losses, I think you'd probably get better propulsive efficiency if you just used a sail, which has no energy transmission losses. I think the best case for wind turbines on ships is to use them for energy harvesting in port and in tail winds. I'm sure someone is doing this, but you need to balance the initial hardware investment and operational maintenance costs against the potential fuel savings in order to justify the installation. There are a large quantity of energy harvesting/conserving technologies out there that are trying to take profit the IMO restrictions (which is a very good thing I think). The interesting thing is that global shipping is only a few percent (used to be 2%) of the worlds transportation carbon emissions, but it transports the most tonnage of any mode of transport. My point is that, while all of this focus on the shipping industry is necessary and very interesting to me personally, things like converting automobiles or airliner emission is much more of an environmental impact.

Gwypaas 7y ago

I think the problem is the efficiency, a wind turbine is limited to about 60% by Betz law[0] and most today seem to have 35-45% efficiency. Which means with all losses included I think it's hard to see a headwind helping, same with how the apparent wind shifts forward, which would make a weak stern wind not help anything and the turbine just be drag. They are making trials with wind "turbines" using the magnus effect[1], they seem to save about 300 tons of fuel per year, but since the article doesn't include the ships yearly total amount it is hard to put it into a relation to anything. https://safety4sea.com/tests-from-rotor-sail-technology-on-viking-grace-indicate-savings/ https://safety4sea.com/tests-from-rotor-sail-technology-on-v... I think ships is one of the applications where hydrogren could be feasable. Batteries are hard when you have to have the range from China to Europe or NA without stops and the density of hydrogen could maybe solve that. Especially since compared to cars the distribution network is more easily centered around large harbours and routes which is already used to handling dangerous goods. Though the competition is going to be synthetic hydrocarbons and all they need are producers, the entire world is already devoted to transporting them. [0] https://en.wikipedia.org/wiki/Wind_turbine https://en.wikipedia.org/wiki/Wind_turbine [1] https://en.wikipedia.org/wiki/Magnus_effect https://en.wikipedia.org/wiki/Magnus_effect

mojomark 7y ago

The idea is not perpetual motion as long as you're not trying to extract energy for propulsion directly from a head wind. You could, however, certainly use a wind turbine to store energy while not underway (e.g. while in port trabsferring cargo or at anchor) and then use that energy to propel against a headwind later. (I'm a marine engineer and work on ship propulsion system design, specifically WRT energy efficiency of propulsion systems.) The challenge with a hybrid wind turbine-electric propulsion would be the energy efficiency losses from turbine generator through a power conversion (and probably storage) device and ultimately the propulsion motor. By the time you're finished, it probably would have been more practical to use some type of sail to harvest wind energy for propulsion directly with no losses. For a head wind, your wind turbine would be harvesting energy, but it would also be creating significant air drag which would be added to the total resistance of the vessel, so the sum total of propulsive power would be negative in a direct head wind scenario. Interstingly, the opposite is true for a tail wind - that is you'll be gaining thrust (like a sail) in addition to harvesting some of that energy. Again, though, because of the energy conversion losses, I think you'd probably get better propulsive efficiency if you just used a sail, which has no energy transmission losses. I think the best case for wind turbines on ships is to use them for energy harvesting in port and in tail winds. I'm sure someone is doing this, but you need to balance the initial hardware investment and operational maintenance costs against the potential fuel savings in order to justify the installation. There are a large quantity of energy harvesting/conserving technologies out there that are trying to take profit the IMO restrictions (which is a very good thing I think). The interesting thing is that global shipping is only a few percent (used to be 2%) of the worlds transportation carbon emissions, but it transports the most tonnage of any mode of transport. My point is that, while all of this focus on the shipping industry is necessary and very interesting to me personally, things like converting automobiles or airliner emission is much more of an environmental impact.