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Hydraulic hybrids tap into alternative energy

Stand-alone technology shows a 30% reduction in CO2 emissions and improved gas mileage.

Research company Artemis Intelligent Power, Edinburgh, Scotland, revealed a new type of hybrid car and truck transmission based on hydraulic technology. Artemis has been developing a hydraulic hybrid car transmission for the past two years, deploying its Digital Displacement technology.

The Energy Saving Trust, one of the UK’s leading organizations set up to mitigate the damaging effects of climate change, confirmed that independent tests on a prototype car, based on a BMW 530i, had doubled the fuel efficiency in city driving compared to the same car with a manual transmission.

Overall, including highway driving, the prototype had 30% lower CO2 emissions than it had before the company fitted its energy saving transmission. The tests were conducted at Millbrook Proving Ground, one of only two locations in the UK officially approved for emissions testing by manufacturers.

Project background

Artemis’ goal is to make hybrid cars an economical — not just a lifestyle — choice. Rather than using electric motors and batteries, the Artemis car uses its Digital Displacement hydraulic motors to drive the wheels and compressed gas to store energy. This makes the company’s hydraulic transmission potentially much more durable, lighter, and cheaper than electric hybrids. In most vehicles, the company expects substantially better fuel savings than electric hybrids.

Artemis developed new transmission components and technology, then switched them with the standard manual transmission. The new transmission is automatic, but apart from this the new components fit in the same space as before, so the car looks and feels the same as it did before.

Visitors are shown the two Digital Displacement motors which drive the rear wheels on this BMW, which is fitted with a hydraulic hybrid drive transmission, pictured in the drawing above.

Artemis replaced the standard transmission of a BMW 530i with a hydraulic one built around its efficient computer-controlled Digital Displacement hydraulic pumps and motors. As well as saving fuel by optimizing the engine speed, energy that would otherwise be lost when applying the brakes is captured and stored in a hydraulic accumulator about the size of a scuba diver’s air tank. The engine can actually be switched off and the car driven just from the stored energy, further decreasing its emissions.

Artemis’ Digital Displacement hydraulic hybrid is about one-third the size and weight of a similar electric hybrid transmission. And by being a series rather than parallel architecture, and by storing captured braking energy in a hydraulic accumulator instead of a battery, full power is available instantly, even with the engine off.

To power the vehicle, Artemis has fitted a Digital Displacement hydraulic pump and two Digital Displacement motors, one driving each rear wheel. The three machines are coordinated by a central transmission controller unit that also reads the driver’s pedal and controls the engine, taking information from a variety of sensors located around the car.

Each Digital Displacement unit has a controller located behind panels in the car’s trunk. The units peak at 97% efficiency, and Artemis claims that “the Digital Displacement technology ensures that they maintain higher efficiencies than any other hydraulic machine around.”

The car demonstrated in Edinburgh had a gasoline engine, and the Artemis technology can be used equally well with diesel and biofuel engines.

Commercial vehicles, rather than passenger cars, will most likely be the first on-highway vehicles to be fitted with the new transmissions. The Artemis Digital Displacement technology is built on hydraulic components for vehicles such as trucks and vans. Commercial vehicles make up almost 20% of road traffic in the UK, but contribute disproportionately to the country’s emissions because of their higher weight and high annual mileage. Artemis chose to work with a BMW because its engine is of similar power to medium size commercial vehicles.

Bosch Rexroth Corp. has purchased the worldwide rights to use the company’s Digital Displacement technology in on-highway vehicles. Another international manufacturer of hydraulic systems to the construction, agricultural and handling machinery industry has also signed up to use Artemis’ technology off-road.

As the project grows, Artemis plans to expand into the rapidly growing renewable energy sector. It has plans to replace wind turbine mechanical gearboxes with its hydraulic technology. Independent studies show that 30% of wind turbine downtime is due to mechanical gearbox failures. The increasing demand for wind turbines to be sited offshore is encouraging wind farm developers to look ever harder at gearbox reliability because maintenance costs are much higher offshore. Artemis has already begun developing the components for full size wind

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