The standard combustion engine uses a lot of fuel to beat a standing car’s inertia and put it up to speed and doing this repeatedly over a short period of time results in wear as well as increased emissions. Among other vehicles, garbage trucks have the bad habit to stop and go several times on a block.
Making them hybrid is the next logical step since we’re starting to embrace this technology, but how? Fitting them the standard diesel engine plus electric motors and a huge battery pack to sustain the amount of work won’t cut it as it will decrease the truck’s payload capacity.
Parker Hannifin’s RunWise project found that the best way is to fit them with hydraulic hybrid refuse vehicle tech. It’s still a hybrid, but instead the classic electric way, this method implies hydraulic fluid stored under pressure which can be used to move the wheels. Similar to Citroen/Peugeot Hybrid Air technology.
The standard truck transmission gets ditched to adopt high-pressure and low-pressure hydraulic accumulators as well as pumps. The engine remains in its place and uses a short three-speed gearbox.
The principle is quite simple from here - on start-up, the diesel engine charges the high-pressure accumulator which then drives the hydraulic motors for the wheels to turn. It features regenerative braking too, with the hydraulic fluid from the low-pressure chamber being sent back in the high-pressure one during braking. This makes the truck recover up to 71 percent of the energy used to brake.
Of course, the system works for low and medium speeds. Skip over the 45 mph (72 km/h) mark on the dial and the diesel engine alone will handle the wheel turning, but that rarely happens during a normal day of a garbage truck.
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