61–70 of 70 posts
Maybe nuclear power for commercial ships? Global navies have proved and refined nuclear power technology for their ships. Why not apply this technology to the commercial sector, instead of carrying gallons of diesel?
As someone that has designed (military) ships, here are my thoughts. - LNG is definitely happening, and that alone will make a massive difference in emissions. - No shit smoother bottoms and bulbous bows are better for efficiency, that's been standard practice for decades and large cargo ships are generally not that old. - Counter rotating props are interesting, I could see that being a big win but the mechanical com…
1) ridiculously low $ per kWh electricity from multi hundred megawatt scale photovoltaic plants may may cracking hydrogen from seawater economical. It takes a ton of power, but if your power is almost free, it can work.
2) store the hydrogen. This has its own technical problems but in terms of energy density can replace heavy fuel oil
3) power ships from massively parallel arrays of hydrogen fuel cells, driving electric thrusters such as current generation large azipods.
Or, if there is some amazing advancement in Wh stored per kilogram/cubic meter of battery, in battery technology generally, skip the hydrogen step and have short to medium range small cargo ships the size of "geared" containerships which recharge in a fashion similarly to the upcoming Tesla semi tractor.
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I would expect counter rotating props to be more reliable. Instead of one big engine/prop you have two smaller ones. While it is more likely that something will break, it isn't a catastrophic failure: you continue to your destination using just the other engine/prop.
Note that they're not talking about two separate props on separate shafts, they're talking about 2 props rotating in opposite directions on the same shaft. Many ships don't have a 1:1 ratio between propellors and engines anyway, if 2 separate shafts & props were faster they could do that easily. But counterrotating on the same shaft adds more critical moving parts in an already sensitive area.
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What about solar? I know it does not scale down very well or work for the military, but solar seems useful for the largest ships. MV Barzan is a container ships that's 400 m x 58.6 m. If you take say 400m x 50m * 24% solar panels that's ~6500 HP in full sun. I know the engines are significantly larger than that but not sure how much they use at cruising speed.
Solar can produce a great many kWh per month if you cover the roof of a whole Costco sized warehouse with it, but for instantaneous power is nowhere near sufficient for large ship propulsion. The energy density in joules per kg or liter of fuel in compressed gas or heavy fuel oil or diesel is significantly higher than what is now possible with batteries. Where pv might have a role is shore bases charging stations to…
I am more curious about the scale of savings and the costs of trying to have a solar on top of the ship.
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> LNG is definitely happening, and that alone will make a massive difference in emissions An important, if often repeated point: Natural gas reduces emissions at the point of consumption; that may be balanced out by higher climate change impact when it's mined. If someone has good, conclusive information on that issue, it would be appreciated.
People mean different things whey they talk about emissions. Shipping is particularly dirty because of the low-grade fuel that they've been using. Its very high in sulphur content, and typically contains a higher fraction of heavier compounds that don't burn as well. So the ships produce more unburned hydrocarbons (smog precursors) and sulphur oxides (acid rain precursors). So even if the total CO2 emissions are simi…
Surely the most effective way of improving shipping efficiency is to stop shipping as much? The principal of locality can be applied to far more than memory architectures.
For example, China is extremely good at manufacturing, Japan and South Korea are great at electronics manufacturing, Germany engineering disciplines, etc, etc. North America could do this but everything would be very expensive or impossible to source locally.
Also, what about food? Do you enjoy coffee? Well it got to North America on a ship. How about bananas? Same thing, that tropical fruit's year round availability is due to shipping logistics. The same thing applies to most "everyday" goods like chocolate, transistors, cotton, etc, etc.
Also, going back to China, they don't only manufacture cheap goods to be shipped to Wal-Mart. They are also a major farming and agriculture producer.
no one, even from the military posters, mentioned the new salt water engines that are in development? https://www.huffingtonpost.com/2014/04/09/seawater-to-fuel-n...
As someone that has designed (military) ships, here are my thoughts. - LNG is definitely happening, and that alone will make a massive difference in emissions. - No shit smoother bottoms and bulbous bows are better for efficiency, that's been standard practice for decades and large cargo ships are generally not that old. - Counter rotating props are interesting, I could see that being a big win but the mechanical com…
> LNG is definitely happening, and that alone will make a massive difference in emissions An important, if often repeated point: Natural gas reduces emissions at the point of consumption; that may be balanced out by higher climate change impact when it's mined. If someone has good, conclusive information on that issue, it would be appreciated.
1. When methane is burned, the carbon dioxide emissions are about 30% lower per unit energy than when liquid fuels are burned (50 g/MJ for methane, vs abt 74 g/MJ for liquid fuels) 2. When LNG is produced, an additional ~10% CO2 is generated, via energy consumption in the gas liquefaction plant 3. Methane leakage from production plant and pipelines is estimated at about 3% of total. This adds a greenhouse gas effect of about 63% (since methane is ~21 times more potent than CO2, greenhouse-effect-wise). 4. Pollutants such as sulfur oxides and soot from natural gas combustion are essentially nil. Heavy fuel oil for ships can have a very high sulfur content.
Sooo... it is quite possible that natural gas use has a higher climate change impact, due to leakages. For other pollutants, natural gas produces less.
Earlier quoted context omitted.
People mean different things whey they talk about emissions. Shipping is particularly dirty because of the low-grade fuel that they've been using. Its very high in sulphur content, and typically contains a higher fraction of heavier compounds that don't burn as well. So the ships produce more unburned hydrocarbons (smog precursors) and sulphur oxides (acid rain precursors). So even if the total CO2 emissions are simi…
So... can we produce LNG without producing Diesel? I thought crude oil mandated the proportion, and it was a “good thing” that we found some opportunities to consume the Diesel part? We can’t convert the whole world to LNG because we’ll have way too much Diesel left.
Earlier quoted context omitted.
> LNG is definitely happening, and that alone will make a massive difference in emissions An important, if often repeated point: Natural gas reduces emissions at the point of consumption; that may be balanced out by higher climate change impact when it's mined. If someone has good, conclusive information on that issue, it would be appreciated.
I have some information... 1. When methane is burned, the carbon dioxide emissions are about 30% lower per unit energy than when liquid fuels are burned (50 g/MJ for methane, vs abt 74 g/MJ for liquid fuels) 2. When LNG is produced, an additional ~10% CO2 is generated, via energy consumption in the gas liquefaction plant 3. Methane leakage from production plant and pipelines is estimated at about 3% of total. This ad…