Students at Purdue University in the US have created what is thought to be the first vehicle that uses water in all of its hydraulic systems, including power steering, power brakes and transmission.
Recent advances in water hydraulic systems have allowed them to perform as well as petroleum hydraulic systems. Because water is said to offer several environmental and economic advantages over petroleum hydraulic fluid, the students teamed up to demonstrate that such a vehicle is now possible. Although the mower was redesigned to prove a point, it does have a practical purpose.
Gary Krutz, professor of agricultural and biological engineering and the students’ advisor, said water hydraulic systems only would be practical in vehicles that use high-pressure systems, such as heavy equipment used in construction, agriculture, forestry and mining.
Using water in hydraulic systems currently costs twice as much as using petroleum products, but that could change as more applications are found for water hydraulics.
The boost in energy efficiency is reportedly due to water’s lower viscosity. Water flows up to 1,000 times faster than hydraulic fluid at normal air temperatures and once the machine is warmed up, water is still 10 times as viscous.
Improved viscosity means less energy is required to push the hydraulic fluid through the system, making it more efficient. An engine that uses direct gearing is 95 percent efficient; one that uses hydraulic systems is 60 percent efficient.
By using water instead of heavier petroleum fluid, Krutz estimates the efficiency could be boosted at least 10 percent.
‘That doesn’t sound like much, but that would mean a savings of 500 million gallons of gasoline in the United States each year,’ he said. ‘I’m also willing to predict that the lower friction will result in less wear for the equipment.’
Replacing hydraulic fluids with water won’t be without problems, however. Because tighter fittings and higher quality parts are needed to prevent leaks and corrosion, water systems are more costly. Also, the increased viscosity of water means that turbulence within the system could reduce efficiency if the parts aren’t engineered properly.
Krutz predicts that costs could drop quickly if even one manufacturer decided to focus on water hydraulic systems. ‘All we need is for one major lawn mower company to decide to use this technology in a premium machine, and the cost would drop significantly,’ he says.
Stainless steel and ceramics are among the expensive materials most needed for water hydraulic systems, and as the cost of these materials drop, replacing petroleum hydraulic fluid comes closer to becoming cost effective.
‘Do you remember how you used to have to replace the muffler on your car every three years?’ Krutz asks. ‘Steel producers figured out how to make stainless steel cheaper, and the auto manufacturers began using it to make mufflers. Now mufflers last as long as most people own a car.
‘This price reduction in stainless steel is also making water hydraulic systems affordable, but steel materials still require a lot of engineering work to eliminate turbulence in the system,’ he added.