4 ms·

Just adding a few small details here: 1. When the canal was built, it was deemed to hard and expensive to dig at the level of the two oceans so they imagined th

Just adding a few small details here: 1. When the canal was built, it was deemed to hard and expensive to dig at the level of the two oceans so they imagined the locks system as a solution for that. Back then, the canal was built with US money in a time of conflict between Panama(which was part of Colombia) and Colombia. Today Panama is an independent country, but they don't have the finances to upgrade the canal. 2. They don't want to bring water from the ocean up the canal is because the canal gets its water from a series of fresh water lakes. Bringing salty water would kill the life in the lakes are around the lakes and cause a lot more problems long term.

myself248 3y ago
Agreed, pumping sea water seems terrible, but it also seems like there'd be no reason to do that. First, at either end of the system there's a chunk of river at sea-level-ish but flowing towards the sea, so the water up at the upstream end where the lower locks are is probably not salty at all. Second, if each lock had its own pumps, doing it in 3 short lifts rather than 1 big lift to the top, then even if the one or two closest to sea-level ended up somewhat brackish, there'd be a dilution effect going up hill, and there would still be fresh water entering the system from the lakes which would tend to flush it downward. I don't think Gatun is at risk. But what would it cost? Okay, bullshit math time. In mixed units just to annoy metric purists: A quick search says each lock cycle is around 50 million gallons, or 153-acre-feet. It takes 3 steps to raise them 85 feet above sea level, in energy terms let's just model it as one big step. It takes almost exactly 1kWh of energy to raise one acre-foot of water by 1 foot, so 153 acre-feet raised by 85 feet is about 13MWh per cycle. Apparently the canal manages about 40 transits per day, which I'm interpreting as each lock cycles once, so that's 521MWh of energy being provided by the rain delivering the water to the upper lakes. Let's say we want to double that to 80 cycles a day. Oh, also, pumps are only about 70% efficient, so we actually need to provide 745MWh of power. Divide that by 24 hours and we end up with a 31MW power plant. That's..... tiny. Nah. Let's do it with solar. Roughly 6 hours peak sun equivalent per day (data for bocas del toro), we need 124MW of panels. The lakes have plenty of storage so there's no need for batteries, just run the pumps only when the sun is shining. Utility-scale solar runs around $1/watt installed. Labor is cheaper in Panama but conditions may be more challenging, I don't have good estimates for either of those so I'll assume they cancel out. Hey, it's napkin math! $124M for the panels, figure the pumps and plumbing aren't cheap either but even if that's 10x the cost, we're probably still in the single-digit billions. If they've been charging ships to use the canal like Egypt charges for the Suez, they should have quite the rainy-day, er, not-rainy-enough-day, fund for such projects. Especially if they raise prices auction-style during times of high demand, and let the high bidder through. That seems like a no-brainer. What am I missing?
- jodrellblank 3y ago
  I did my own estimate ( https://news.ycombinator.com/item?id=38997124 https://news.ycombinator.com/item?id=38997124 ) via a different method, before reading down to yours, and got ~450MWh of energy needed - which is close enough to your 521MWh that I'm pretty happy. > "Nah. Let's do it with solar." Why not with hydroelectric? Store power by pumping water up to Gatun Lake, generate power while filling the locks as the water falls down...
  - myself248 3y ago
    > which is close enough to your 521MWh that I'm pretty happy. Nice! And Dinorwig runs around 72% round-trip efficiency, which is higher than I expect to see here simply on account of scale, but also in the ballpark. > generate power while filling the locks as the water falls down... Now that's an interesting one. There are already lock systems where there's two parallel chains, and the ascending and descending locks operate in lock-step, with the two locks first equalizing water with each other, before the ascending takes water from above and the descending releases water to below. So that doubles the amount of traffic that can be handled by the same amount of water. Presumably building twice the infrastructure would be cost-prohibitive or they would've done it over the preceding decade, but storing the water's energy could be quite a bit cheaper and smaller. Edit: Much simpler, takes more space, saves almost as much water: https://en.wikipedia.org/wiki/Panama_Canal_expansion_project#Water_saving_basins https://en.wikipedia.org/wiki/Panama_Canal_expansion_project... It ends up being a lot like linking the shafts of all the pumps, with extra steps for control, eh? Edit: Oh. Yeah. Okay, at each lock, you've got three pumps on a common shaft, with clutches: (fill turbine)--[clutch]--(lift pump)--[clutch]--(drain turbine) Whether you're filling or draining, you clutch that turbine to the lift pump, and lift some water upward as the working water flows downward. No electricity needed. Hmm. Alright, who wants to go pitch a project?

myself248 3y ago

Agreed, pumping sea water seems terrible, but it also seems like there'd be no reason to do that. First, at either end of the system there's a chunk of river at sea-level-ish but flowing towards the sea, so the water up at the upstream end where the lower locks are is probably not salty at all. Second, if each lock had its own pumps, doing it in 3 short lifts rather than 1 big lift to the top, then even if the one or two closest to sea-level ended up somewhat brackish, there'd be a dilution effect going up hill, and there would still be fresh water entering the system from the lakes which would tend to flush it downward. I don't think Gatun is at risk. But what would it cost? Okay, bullshit math time. In mixed units just to annoy metric purists: A quick search says each lock cycle is around 50 million gallons, or 153-acre-feet. It takes 3 steps to raise them 85 feet above sea level, in energy terms let's just model it as one big step. It takes almost exactly 1kWh of energy to raise one acre-foot of water by 1 foot, so 153 acre-feet raised by 85 feet is about 13MWh per cycle. Apparently the canal manages about 40 transits per day, which I'm interpreting as each lock cycles once, so that's 521MWh of energy being provided by the rain delivering the water to the upper lakes. Let's say we want to double that to 80 cycles a day. Oh, also, pumps are only about 70% efficient, so we actually need to provide 745MWh of power. Divide that by 24 hours and we end up with a 31MW power plant. That's..... tiny. Nah. Let's do it with solar. Roughly 6 hours peak sun equivalent per day (data for bocas del toro), we need 124MW of panels. The lakes have plenty of storage so there's no need for batteries, just run the pumps only when the sun is shining. Utility-scale solar runs around $1/watt installed. Labor is cheaper in Panama but conditions may be more challenging, I don't have good estimates for either of those so I'll assume they cancel out. Hey, it's napkin math! $124M for the panels, figure the pumps and plumbing aren't cheap either but even if that's 10x the cost, we're probably still in the single-digit billions. If they've been charging ships to use the canal like Egypt charges for the Suez, they should have quite the rainy-day, er, not-rainy-enough-day, fund for such projects. Especially if they raise prices auction-style during times of high demand, and let the high bidder through. That seems like a no-brainer. What am I missing?

jodrellblank 3y ago
I did my own estimate ( https://news.ycombinator.com/item?id=38997124 https://news.ycombinator.com/item?id=38997124 ) via a different method, before reading down to yours, and got ~450MWh of energy needed - which is close enough to your 521MWh that I'm pretty happy. > "Nah. Let's do it with solar." Why not with hydroelectric? Store power by pumping water up to Gatun Lake, generate power while filling the locks as the water falls down...
- myself248 3y ago
  > which is close enough to your 521MWh that I'm pretty happy. Nice! And Dinorwig runs around 72% round-trip efficiency, which is higher than I expect to see here simply on account of scale, but also in the ballpark. > generate power while filling the locks as the water falls down... Now that's an interesting one. There are already lock systems where there's two parallel chains, and the ascending and descending locks operate in lock-step, with the two locks first equalizing water with each other, before the ascending takes water from above and the descending releases water to below. So that doubles the amount of traffic that can be handled by the same amount of water. Presumably building twice the infrastructure would be cost-prohibitive or they would've done it over the preceding decade, but storing the water's energy could be quite a bit cheaper and smaller. Edit: Much simpler, takes more space, saves almost as much water: https://en.wikipedia.org/wiki/Panama_Canal_expansion_project#Water_saving_basins https://en.wikipedia.org/wiki/Panama_Canal_expansion_project... It ends up being a lot like linking the shafts of all the pumps, with extra steps for control, eh? Edit: Oh. Yeah. Okay, at each lock, you've got three pumps on a common shaft, with clutches: (fill turbine)--[clutch]--(lift pump)--[clutch]--(drain turbine) Whether you're filling or draining, you clutch that turbine to the lift pump, and lift some water upward as the working water flows downward. No electricity needed. Hmm. Alright, who wants to go pitch a project?