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One way to achieve this is to prevent trains from wasting energy. In a 2010 study, Edinburgh-based Artemis Intelligent Power demonstrated that between 64% and 73% of a train’s energy is lost through braking and transmission.

“There is a lot of energy that gets wasted in these areas,” says Alasdair Robertson, commercial director at Artemis. “Obviously you still have to stop the train but ideally you would find a way to recover that energy.”

To meet this challenge, Artemis is leading a number of initiatives to prove the benefits that digital displacement hydraulics can bring to diesel-powered rail vehicles. The company’s core technology, which it has been developing for 20 years, is a new type of digital hydraulic pump that uses computer-controlled valves to switch the pump’s cylinders off when not needed.

In its current project, in conjunction with train operator ScotRail, Artemis has replaced the auxiliary drives used for power cooling fans and electricity generation with the company’s own digital displacement pump. Together the auxiliary drives use up around 10%-15% of the engine’s fuel.

According to Artemis, this technology has already demonstrated fuel savings of 9,900 litres of diesel per carriage, per year. If adopted across ScotRail’s fleet of class 170 trains, the company says it could cut CO₂ emissions by more than 4,000t.

“That is fuel that doesn't have to be burnt and CO₂ that is not released,” says Robertson.

Over the long term, digital displacement technology could be used throughout a train’s entire transmission system. The energy used in braking could then be stored in accumulators to be released to supplement engine power during acceleration, reducing passenger journey times. Overall this ‘hybrid drive train’ could cut fuel use by up to 30%, which is, says Robertson, “quite frankly massive.”

There are other benefits, too. Robertson says the company’s technology could, for example, be used to switch off a train’s engines when it is pulling into and out of stations, reducing noise pollution in surrounding areas.

“There are now quite a lot of questions over noise,” Robertson explains. “The trains that run on the TransPennine Express, for example, quite often pull out of stations on limited engine power to reduce noise, smoke and emissions in the station area. If you had a transmission that recovered energy and stored it in the hydraulic accumulators, you could run out of the station without having to turn the engine on.”

Robertson also predicts that the company’s technology could be used to increase a train’s acceleration. 

“We are led to believe that electric trains are slower when they are in mixed operation with diesel trains, because the diesel train acceleration can't quite match the acceleration of the electric,” he says. “We think that with our hydraulic transmission technology we can run the diesel trains at the same frequency as the electric trains.”

Artemis was founded in 1994 with a view to commercialising advanced hydraulic machines first used in the wave power industry for different commercial applications. It was acquired by Mitsubishi in 2010 and today describes itself primarily as a “technology development” company.

“As things stand the hydraulic pump was invented in something like 1893 and well over 100 years later you almost can't tell the difference internally,” he says. “Artemis has fundamentally rethought how hydraulic machines should operate and created the most efficient and controllable hydraulic pumps and motors available.”

For a company in the business of inventing technology, Robertson is, however, keen to emphasise that Artemis “does not just produce ideas and intellectual property”. 

“We have always got an idea of what markets we are working on and who is going to buy the product at the end of the day,” he says. “We develop technology to a very high state of technological readiness, with supply chains that are already fairly well developed.”

This approach is evident in the company’s current collaboration with ScotRail, where it has installed a digital hydraulic pump in a standard diesel commuter train. Robertson says it is “the first installation of a digital displacement pump on an in-service train”. After six months and 100,000 miles of operation, the technology has firmly demonstrated its value, he adds.
    
“It has been very successful and very reliable and it is paving the way for the next stage: installing three pumps on the train and after that looking at full fleet roll out,” he says. “Ultimately we are dealing with a very old industry that is not used to change. Our job is to shake that up and introduce new technology.”