PEDAL TO THE METTLE: In a hydraulic system, the diesel pump [left] pushes hydraulic fluid into the accumulator [red] to reach pressures of up to 385 kilograms per square centimeter. By pressing down on the accelerator, the driver releases that pressurized fluid from the accumulator to then drive the hydraulic motor [right].
Image: Image courtesy of the U.S. Environmental Protection Agency
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Thanks to hybrid hydraulics, there is something especially awesome in the power of the next generation of garbage and delivery trucks that will soon be rolling through your neighborhood. Although they may still look like big, bulky trucks, inside they boast hydraulic power-train systems that are significantly more energy and fuel efficient than similar conventional or gasoline-electric hybrid vehicles. If hybrid hydraulics prove their mettle for more industrial uses, cars may not be far behind.
A hydraulic system replaces all of the electronic components of an gas-electric hybrid (starter motor, generators, controllers, batteries, etcetera) with three parts: a small diesel motor–powered pump, a hydraulic motor and an accumulator. (Hydraulic-powered vehicles also contain an electric battery to power secondary equipment such as lights or a radio.)
The diesel pump pushes hydraulic fluid into the accumulator to reach pressures of up to 385 kilograms per square centimeter. By pressing down on the accelerator, the driver releases that pressurized fluid from the accumulator to then drive the hydraulic motor.
The best analogy might be a person operating a handheld air pump to pressurize a balloon, says Joe Kovach, group vice president of technology and innovation for Cleveland-based Parker Hannifin Corp.'s Hydraulics Group. In this comparison the person equals the pump, which drives air (technically a fluid) into the balloon, and the balloon represents the accumulator. The energy that can be harnessed comes from the force of the air released from the balloon.
"We think it's quite possibly the most cost-effective technology to achieve high fuel efficiency with low carbon emissions," says John Kargul, director of technology transfer with the U.S. Environmental Protection Agency's (EPA) Office of Transportation and Air Quality in Ann Arbor, Mich. Since the early 1990s Kargul and his research team have been testing hybrid hydraulic systems as a core drive-train technology for roughly 20 different sizes of vehicles—from 1,500-kilogram passenger cars to 18,000-kilogram commercial trucks. They also partner with automotive manufacturers including Ford Motor Co., Parker Hannifin and Eaton Corp. as well as delivery companies UPS and FedEx to design, build and field-test prototype vehicles.
They have found several compelling reasons to employ hybrid hydraulic systems for a range of larger, heavier vehicles—trucks and buses as well as military, construction and dock-loading equipment. For starters, these systems can store and discharge energy much faster than electric batteries. They provide 10 times the power in the same size and space as a hybrid electrical system.
Perhaps most vital of all, these vehicles have demonstrated up to 50 percent fuel reduction compared with the latest, most fuel-efficient conventional garbage trucks, Kovach says, adding that recent field trials of trucks equipped with Parker Hannifin's new RunWise hydraulic system in Detroit, Las Vegas and Miami even "freaked out" the garbage truck drivers. "They kept saying, 'There's something wrong with the gas pump,'" says Kovach, whose company will roll out a dozen new hybrid hydraulic refuse trucks in Miami in September. "They were used to putting 44 gallons of gas or diesel fuel in every day, and now they were putting in an average of 22 gallons of fuel."
Hydraulic systems also have the ability to recover up to 75 percent of the energy the vehicle expends in braking and pump it back into the accumulator, whereas gas-electric hybrids only recoup about 15 to 20 percent. (This is significant, given that the energy lost from the brakes on a garbage truck traveling a standard route over three days equals the amount of energy needed to power a typical U.S. household for one month, according to Kovach.)
Additionally, because they draw power from the pressure stored in the accumulator when fully charged, hybrid hydraulic vehicles can shut off their engines and drive for up to 0.2 kilometer before turning them back on. This is especially handy for start-and-stop delivery truck routes. Moreover, rather than have a fleet of trucks fire up their engines simultaneously in the morning, the trucks can drive off for 0.2 kilometer first, eliminating that concentration of noise and exhaust, much to the relief of their neighbors and the EPA.
Hybrid hydraulic systems in trucks actually date back to the 1960s, long before hybrid gas-electric systems were available. Several key deficiencies, however, relegated the technology to the sidelines in favor of gas-electrics for a couple of decades. Primarily, hydraulic accumulators were made of steel, making them extremely heavy. Early hydraulic systems were also more complicated and harder to control, especially because the viscosity, or resistance, of the hydraulic fluid changes depending on its temperature.
During the past decade, though, improvements in several areas have eliminated those challenges. Accumulators are now made of the same lightweight, carbon-composite materials used to fabricate jet fighter planes, and advanced computerized systems have simplified the control issues. More efficient pump systems, leak-proof components, and ecofriendly hydraulic fluid formulas have reduced leakage concerns as well, Kovach says.
Now that these vehicles are beginning to appear on the market—Eaton Corp. has several models of trucks, and Parker plans to roll out their delivery trucks and dock-handling equipment in 2011—smaller applications for hybrid hydraulics are likewise being developed for wind and wave energy equipment as well as bicycles and rickshaws. Carmaker BMW already has several hybrid models that incorporate hydraulic components in development and close to the preproduction stage.
Peter Achten, owner and CEO of Innovation Associates, an engineering company in the Netherlands, sees the trend continuing in the U.S. and Europe, with growth in several emerging markets like South America, China and India where the average customer cannot afford to pay for a vehicle that requires a battery that costs $5,000 or more.
"The hybrid hydraulic will come to the automobile," Achten says. "It is the only way to have a strong reduction in fuel consumption and CO2 emissions without the cost and weight increase of electric batteries, power converters, motors and generators."
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27 Comments
Add Commentsounds good, any complaints?
Reply | Report Abuse | Link to thisYes I have a big complaint, They Lie!!
Reply | Report Abuse | Link to thisNothing one can do can make these as eff as EV hybrids which are 50% or better eff in energy recovery and more so, hold far more energy so they can use a much smaller engine, always running at peak eff, both making hybrid drive more eff.
As one pumps air or other gas, it heats up, losing energy as it cools down. This plus massive fluid friction means big losses no amount of self interest hype can cover up. Same with the Air powered car, little range and worse eff. This is basic physics 101. Just another scam on the gov or any other fool that buys into this.
Better some loses than none at all by not using any technology,
Reply | Report Abuse | Link to this@jerryd, so you've got some scientific results to backup your statements? Or is it just opinion?
Reply | Report Abuse | Link to thisjerryd: The EV starts with mechanical energy from engine, transforms to electric, then to chemical storage. It makes the round trip back to mechanical energy to drive the vehicle. The energy round trip wastes a lot of the efficiency, too.
Reply | Report Abuse | Link to thisSo the best way is not to generate it when not needed. There are engine technology that can do that, such as the D-cycle.
Sounds like a great technology for something which has to make stops every few meters, like a garbage truck. The efficiency of the energy recovery system of the brakes is of prime importance here. But the less one has to brake, the more the efficiency comes down to the efficiency of the engine. For most car drivers, I doubt this will be a very efficient system. We have already seen that gas-electric hybrids are not that great for freeway driving. I suspect the same will be true here.
Reply | Report Abuse | Link to thisFluid power is the one of the most dense method of energy storage. This technology is destined for use in short haul, heavy load transportation. Perfect for buses or trash and delivery trucks in cities. Utilizing electric or hybrid technology for these size vehicles is simply not practical. Look at hybrid SUVs, they get just slightly better mileage that their internal combustion counterparts.
Reply | Report Abuse | Link to thisThis 'new' power source is simply a diesel powered vehicle with a hydraulic transmission and transient power storage system. Its low efficiency as a power source may be offset by providing for intermittent peak requirements without consuming additional fuel. The aforementioned garbage collection trucks would be good candidates (somewhat like bulldozers), not so much for long haul trucking... That's my opinion, anyway.
Reply | Report Abuse | Link to thisMy only concern is the safety of such a vehicle in an accident. Sitting over a tank that is pressurized to such a degree when a truck rear ends me would be a nerve wracking experience to say the least. Again for the larger vehicles it is probably not a major problem, but for smaller cars, I am not so sure.
Reply | Report Abuse | Link to thisHaving another alternative is always good. Considering the immense amount of wasteful engine idling there is in this world, the more approaches devised to eliminate it the better. Ideally no engine would run without its power being used or stored.
Reply | Report Abuse | Link to thisCompressing a gas for direct motive purposes, results in energy lost as heat, but pumping liquid, incompressible for practical purposes, does not. What's missing from the article is the internal working of the accumulator. The fluid is probably moving a piston or diaphragm against a gas pocket, and the energy is stored in the compressed gas --- hot while compressed. Then as the fluid is used to drive the vehicle, the gas expands and cools down. So the heat/cool in that scenario is not an energy loss provided there's insulation to prevent loss.
Reply | Report Abuse | Link to thisThe energy losses are in the efficiency of the hydraulic pump and motor, probably 10% each, and fluid friction in the plumbing. Whatever the loss is, it will have to be dealt with in a fluid cooler. This stuff is highly developed in the aviation industry; commercial jets use hydraulic drives to move control surfaces (maybe not in the latest designs).
Overall, a good candidate. Let's hope the government just sponsors development of various plausible ideas but lets the users pick the winners.
Conrad is right -- have you ever seen what happens when a heavy pressurized scuba tank full of gas falls over and cracks the cap? Boom. Its worse than a stick of dynamite. Its like a big shaped charge, metal fragments can decapitate with such force they are embedded into reinforced concrete. Give me a gas tank fire any day over that explosion.
Reply | Report Abuse | Link to thisEvery form of transportation involves storing energy --- except electrical systems with a third rail or overhead lines that have their own hazards. Present-day car batteries can explode and splatter sulfuric acid, gas tanks can leak in your garage and burn your house down, laptop batteries explode and so will the ones in hybrid cars, and hydrogen: wow!. The more compactly energy is stored, the more violent the release when something goes haywire.
Reply | Report Abuse | Link to thisThe new carbon fiber composite tanks are no doubt being tested to learn the failure mode in a crash, but it may be a graceful one --- ever try to break an elm branch? In fact that might be a better way to make a scuba tank --- lighter anyway.
What would be nice is if the article explained more about the technology. The analogy is very misleading the storage system is nothing like pumping a balloon with air. Gasses are compressive, hydraulic fluids are not. Pressurising a container (accumulator) with fluid dose not store energy. If this was a compressed gas system I could see how it works but its, not its meant to be hydraulic HOW? Please someone who really knows how this works explain.
Reply | Report Abuse | Link to thisWhat would be nice is if the article explained more about the technology. The analogy is very misleading the storage system is nothing like pumping a balloon with air. Gasses are compressive, hydraulic fluids are not. Pressurising a container (accumulator) with fluid dose not store energy. If this was a compressed gas system I could see how it works but its, not it’s meant to be hydraulic HOW? Please someone who really knows how this works explain.
Reply | Report Abuse | Link to this"We have already seen that gas-electric hybrids are not that great for freeway driving." Is that REALLY universally known? As an owner of an Honda Accord Hybrid, I do MUCH better on the freeway, than town driving.
Reply | Report Abuse | Link to thisI would prefer to use a small diesel engine that uses conventional mechanical gear amplification to wind up a big mechanical spring, basically a big version of the wind-up toy cars that I played with a very long time ago.
Reply | Report Abuse | Link to thisThe advantage of storing energy in a spring made of advanced compositive materials (much like modern archery equipment) is that the spring can be light weight and will not generate a lot of waste heat when compressing and decompressing, like liquids and gases tend to do.
Liquid and gas very high pressure containment systems tend to develop leaks. Springs usually do not fail gradually and corrosion isn't much of a problem. The triggers and clutches that govern a spring system will be what wear out.
Not surprisingly, I believe Switzerland has done the most work in this regard and may have had a streetcar that was wound up at stations along its route.
I have a lot of experience with hydraulic hybrids with agricultural tractors, light trucks and even heavy fighting tanks.
Reply | Report Abuse | Link to thisI am ready to cooperate with the manufacturer with several of my inventions.
Something like the Mealer Automobile... But GM crushed that one so far!
Reply | Report Abuse | Link to thisHi.Accept the information:
Reply | Report Abuse | Link to thisEffect of impellent mechanics. The process having the closed cycle of a working material.
The working material, under the influence of offered effect, in the closed volume, creates working pressure. Under the influence of working pressure there is a hydraulic blow. After hydraulic blow, the working material accepts an initial condition and readiness for manufacture of new hydraulic blow.
Offered working process occurs without noise and gas emission. In the given effect there is no process of burning and there is no allocation of the big temperature. Use of offered effect assumes essentially new impellent installations
Opening of offered effect opens new possibilities in mechanical engineering - essentially new impellent installations. Under the influence of offered hydraulic effect known impellent units are excluded: pumps, mechanical connections and pistons.
Ability of a working liquid to raise and lower hydraulic pressure in the closed volume, can be used in a wide range of services.
Sensitivity of an accelerator of difference of working pressure makes: s/10(kg/m2).
The used working density in the course of researches - 40-50 kg/m2. The received maximum density - 250 kg/m2. And it not a limit.
The most simple and accessible use of offered effect – a drive of the generator of an electric current. The given drive excludes presence of gasoline, kerosene, diesel fuel. Generation process passes in one working volume.
This achievement of technology of modulation of electric charges. The offered technology concerns to alternative sciences. At the heart of offered technologies there is a theory and practice of independent researches of the author.
It is absolutely new technology. Willingly I will answer your questions for cooperation.
Hi.
Reply | Report Abuse | Link to thisAccept the information:
Effect of impellent mechanics. The process having the closed cycle of a working material.
The working material, under the influence of offered effect, in the closed volume, creates working pressure. Under the influence of working pressure there is a hydraulic blow. After hydraulic blow, the working material accepts an initial condition and readiness for manufacture of new hydraulic blow.
Offered working process occurs without noise and gas emission. In the given effect there is no process of burning and there is no allocation of the big temperature. Use of offered effect assumes essentially new impellent installations
Opening of offered effect opens new possibilities in mechanical engineering - essentially new impellent installations. Under the influence of offered hydraulic effect known impellent units are excluded: pumps, mechanical connections and pistons.
Ability of a working liquid to raise and lower hydraulic pressure in the closed volume, can be used in a wide range of services.
Sensitivity of an accelerator of difference of working pressure makes: s/10(kg/m^2).
The used working density in the course of researches - 40-50 kg/m^2. The received maximum density - 250 kg/m^2. And it not a limit.
The most simple and accessible use of offered effect – a drive of the generator of an electric current. The given drive excludes presence of gasoline, kerosene, diesel fuel. Generation process passes in one working volume.
This achievement of technology of modulation of electric charges. The offered technology concerns to alternative sciences. At the heart of offered technologies there is a theory and practice of independent researches of the author.
It is absolutely new technology. Willingly I will answer your questions for cooperation.
A simple Google search reveals that the bladder-type hydraulic accumulator was patented in 1943 and first used in WWII combat aircraft to be able to feather the propeller in case of engine failure. It is a mature technology that is used extensively in industry. The hydraulic fluid is not compressed; nitrogen behind the bladder is actually storing the energy. You armchair physicists should leave the thinking to the people actually doing the work. They have a handle on the situation.
Reply | Report Abuse | Link to thisElectric hybrids are not nearly as efficient as they could be because they're pulling around several hundred pounds of batteries. The hydraulic accumulator improves the hybrid system because the ratio of the energy it stores to its weight is much higher than batteries. Also, diesel engines are much more efficient than gasoline engines of similar output. It's a great system for stop-and-go driving.
No hybrid is suited for continuous driving because you reap no benefit from the hybrid system. The efficiency of the hybrid is realized in capturing and storing the kinetic energy of the vehicle during braking. No braking = nothing for the hybrid system to do = waste of energy hauling around batteries or hydraulic accumulators.
You should be interested more not only the handle, but also other areas of impellent mechanics. In offered effect there is no communication with your comment. It absolutely other theme. It is a pity to me that you have wasted time and haven't understood a material. I can present a photo «the stand – the engine». I not the room physicist. I am a researcher and the experimenter. Here you too have made a mistake.
Reply | Report Abuse | Link to thisTo Spider, the technology behind is actually very simple. The storing of energy is not in gas, but the energy is stored in fluid under high pressure. The accumulator provides the high pressure storage. The accumulator can't store a lot of energy, only enough for a few hundred meter running, but it is enough to store the energy recovered from braking. This recovered energy is immediately used to pull the truck from stop after braking, that 's why this hybrid system is chosen for garbage truck, or vehicle that does frequent stop and go. Hydraulic hybrid has higher recovery than E-hybrid, also , all battery has limited life time , example, from a few hundred to 1~2thousand times, hydraulic storage system has almost unlimited life time, provided with proper servicing.
Reply | Report Abuse | Link to thisGood alternatives ! People who drive <a title="Hybrid automobiles waste a lot of money for most people" href="http://www.cardealexpert.com/news-information/saving-money/hybrid-cars-waste-money/"> hybrid vehicles</a> supposedly save a lot of money, along with the earth and so forth, by doing this. Hybrids do use less gas, and it would seem a fair claim on the surface. However, a study has just been released which rakes hybrid vehicles over the coals for wasting lots of money.
Reply | Report Abuse | Link to thisIt is indeed unfortunate that the writers of this article used an inflated balloon to explain the concept of an accumulator. It doesn't work that way at all. As to likening a filled scuba tank to a pressurized accumulator there is no comparison, and here's why. First, the gas/air in a scuba tank is "free", that is, not in a bladder, like in an accumulator. So even if the accumulator shell should be compromised, there would be no explosion. Not so with a scuba tank. If it is compromised, all the air escapes at once causing further damage. Second, the end of the accumulator where the bladder is filled is not exposed as it is in a scuba tank so not as easily damaged or broken off. Third, the accumulator is held rigid within a frame, protected from damage and not unsecured free to fall over, be struck or ram into something that would break it, like with a scuba tank. (Also, there are different kinds of accumulators. Some are mechanical in that energy is stored by spring compression.) Last, the idea that filled scuba tanks explode violently when pierced by something like a bullet is Hollywood fiction. Good entertainment, but disproven by The Myth Busters some years ago. As has been stated elsewhere in these comments, accumulators are a highly developed technology used successfully in the aeronautics industry for years.
Reply | Report Abuse | Link to thisHi, I love this discussion and all of the opinions about hydraulics vs. electric. I believe that low hp deisel combined with hydraulic with mechanical will out perform electric efficiency all day. Early I read that "hydraulics create fluid heat which is wasted energy". Well thats right, if you waste it. This whole concept is about harnessing energy in whatever created form. It's just alot cheaper heat/energy than electric. Beside that I thought the electric car people don't like where electricity comes from. (coal) When it comes to this design it might work for a trash truck but the accumulator is an antiquated idea for the application to a car. I have been working on a similar concept for years and got away from the accumulator years ago for it's limitations and single use. If there was a King of hydraulics he would never allow fluid in motion to start and stop, because he controls the flow with electronics. Fluid should flow. There is a much better way to capture kinetic energy.
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