5 ms·

As an industrial EE dealing with hydraulics of much larger scales than those on a garbage truck, those other functions do not require significant power to opera

As an industrial EE dealing with hydraulics of much larger scales than those on a garbage truck, those other functions do not require significant power to operate when compared to actually accelerating the vehicle and cargo up to speed (and then slamming on the brakes/regen again for the next stop). The engines in diesel garbage trucks often run at idle when those hydraulics are working, lifting a 100 kg residential can or a 1-ton dumpster through a few meters of motion is not noticeable to a 350 HP diesel, accelerating 30 tons of truck and trash in the same amount of time is why they're equipped with so much more engine power.

postalrat 4y ago
How about compacting the trash in the truck?
- LeifCarrotson 4y ago
  Assuming a 100mm bore cylinder with a 1.5m stroke (~10L volume), operating at 150 bar, with a stroke time of 1 minute, the power required is: Power in kW = Pressure in bar * Flow in liters per minute / 600 2.5 kW = 150 bar * 10 l/min / 600 or a little more than 3 horsepower. That gives you about 15 tons of force. Maybe the trucks use two cylinders, one on each side, so double it? Plus 10% for pump inefficiencies, and 5% for electric motor inefficiencies (200% for diesel-to-kinetic losses)? Still negligible compared to accelerating a huge steel box plus dozens of tons of trash to roadway speeds 1000 times a day. Looking up some existing PTOs and pumps on munciepower.com, it looks like typical refuse systems are provisioned with PTOs and pumps rated for on the order of 10-50 kW, and diesel "prime movers" of 200-400 kW.
dredmorbius 4y ago
Nit: Hydraulics do require a great deal of power, but often delivered over a short time or distance, meaning the total energy demand is low. Which is what NYC's concerned with. EV's are great at delivering high power on demand, for short periods. A selling point of Tesla since the Roadster days was the astounding acceleration. Peak torque at a dead start is a key characteristic of electric motors. What's far more challenging is range, a problem Tesla has addressed quite capably for passenger vehicles, though which remains largely unmet for cargo and heavy-transport equipment (including snow ploughs). Interestingly, there was a period where a non-electrical power network was fairly frequently encountered at neighbourhood or city scale: hydraulic power networks. These often operated high-power loads, though typically for short periods or efforts as my first paragraph describes. Hydraulic accumulators lifted weights or water and provided on-demand power for moving lock gates, cargo hoists, and other typically industrial tasks. These were developed in the early 19th century and many remained operational well into the 20th, with the Wikipedia article below listing several operating into the 1970s. Smaller such networks exist in dentist's offices, auto repair shops, and in many Amish workshops, based on compressed air, and utilising similar principles. <https://en.wikipedia.org/wiki/Hydraulic_power_network https://en.wikipedia.org/wiki/Hydraulic_power_network> (I'm presuming LeifCarrotson knows much of this, others may not. I didn't myself until a few years ago.)

postalrat 4y ago

How about compacting the trash in the truck?

LeifCarrotson 4y ago
Assuming a 100mm bore cylinder with a 1.5m stroke (~10L volume), operating at 150 bar, with a stroke time of 1 minute, the power required is: Power in kW = Pressure in bar * Flow in liters per minute / 600 2.5 kW = 150 bar * 10 l/min / 600 or a little more than 3 horsepower. That gives you about 15 tons of force. Maybe the trucks use two cylinders, one on each side, so double it? Plus 10% for pump inefficiencies, and 5% for electric motor inefficiencies (200% for diesel-to-kinetic losses)? Still negligible compared to accelerating a huge steel box plus dozens of tons of trash to roadway speeds 1000 times a day. Looking up some existing PTOs and pumps on munciepower.com, it looks like typical refuse systems are provisioned with PTOs and pumps rated for on the order of 10-50 kW, and diesel "prime movers" of 200-400 kW.

dredmorbius 4y ago

Nit: Hydraulics do require a great deal of power, but often delivered over a short time or distance, meaning the total energy demand is low. Which is what NYC's concerned with. EV's are great at delivering high power on demand, for short periods. A selling point of Tesla since the Roadster days was the astounding acceleration. Peak torque at a dead start is a key characteristic of electric motors. What's far more challenging is range, a problem Tesla has addressed quite capably for passenger vehicles, though which remains largely unmet for cargo and heavy-transport equipment (including snow ploughs). Interestingly, there was a period where a non-electrical power network was fairly frequently encountered at neighbourhood or city scale: hydraulic power networks. These often operated high-power loads, though typically for short periods or efforts as my first paragraph describes. Hydraulic accumulators lifted weights or water and provided on-demand power for moving lock gates, cargo hoists, and other typically industrial tasks. These were developed in the early 19th century and many remained operational well into the 20th, with the Wikipedia article below listing several operating into the 1970s. Smaller such networks exist in dentist's offices, auto repair shops, and in many Amish workshops, based on compressed air, and utilising similar principles. <https://en.wikipedia.org/wiki/Hydraulic_power_network https://en.wikipedia.org/wiki/Hydraulic_power_network> (I'm presuming LeifCarrotson knows much of this, others may not. I didn't myself until a few years ago.)