4 ms·
I mostly hear about flywheels used in datacenters, to bridge the time from a utility outage to diesel generator startup. That doesn't happen very often at the t
by greglindahl 8y ago
I mostly hear about flywheels used in datacenters, to bridge the time from a utility outage to diesel generator startup. That doesn't happen very often at the typical datacenter -- monthly testing and maybe a real outage or two per year.
- jacquesm 8y agoHospitals as well. That's called 'ride through'.
- robotresearcher 8y agoAnother cool use is in railway stations to store the energy of a train as it slows into the station, then return it when it accelerates away.
- andrei_says_ 8y agoHow does this work? If the flywheel is in the station, how does it “catch” the train’s energy?
- robotresearcher 8y agoThey are on a common electrical system. The train uses regenerative braking to put power into the 'grid'. The flywheel senses this and draws power to spin up. When the train tries to draw a huge current to speed up, the flywheel senses this and dumps power to meet the demand.
- andrei_says_ 8y agoMakes sense. I was imagining some kind of steampunkish mechanical contraption.
- taneq 8y agoThere was something a bit like that for trucks a few years ago, that captured pressurised exhaust while the truck was engine braking and then used it (not sure exactly how) to help the truck accelerate again. Apparently it saved significant amounts of fuel in stop-start situations (rubbish trucks etc.), not sure what happened to it though.
- db48x 8y agoGiant gears that mesh with the sides of the train would be pretty awesome.
- deleted 8y ago[deleted]
- taneq 8y agoWell there's rack railways[1] which are pretty close. I've been on one in India[2] and it was amazing, although a bit scary when (halfway up) one of our fellow passengers told us that one of the trains on that route had derailed and fallen into a ravine a few months prior, killing everyone on board... [1] https://en.wikipedia.org/wiki/Rack_railway https://en.wikipedia.org/wiki/Rack_railway [2] https://en.wikipedia.org/wiki/Nilgiri_Mountain_Railway https://en.wikipedia.org/wiki/Nilgiri_Mountain_Railway
- eric-hu 8y agoI've heard of such systems using pressurized hydraulic fluid in delivery vehicles. Feeding the energy back into the car's kinetic energy worked like an automatic transmission's torque converter, I believe.
- taneq 8y agoYeah, thinking about it I'd guess that the exhaust-gas system didn't take off because of noise. Exhaust brakes are noisy and all the applications that made sense were suburban or inner city. Hydraulic would be much quieter.
- eigenvector 8y agoOne of the reasons this was needed for a long time is that DC traction power systems used rectifiers that only worked one-way, so you couldn't just spit the regenerated braking energy back out on the main AC grid. So without somewhere to store it, regenerative braking would cause temporary overvoltages on your traction power system. With modern power electronic converters, it's probably cheaper and easier to just use the main AC grid as the sink for the regen braking power.
- greglindahl 8y agoI'd read about European high speed trains using regenerative braking and the grid, thanks for explaining why that wasn't what was being talked about! I had no idea about this earlier system.