Take-off for hydraulics power take-off
Dramatic shifts away from renewables in government policy at the start of the 80s, the perception that hydraulics was a sunset industry, plus economic recession at the start of the 90s, does not sound like a formula for business success for engineers who want to develop hydraulics for “alternative energy” systems. But the founders of Artemis Intelligent Power appear to have weathered the storm, and the company may soon become one of Scotland's leading developers of high-tech hydraulics solutions for the ren…
Article by Peter Barr
“Conventional hydraulics have some real limitations,” says the managing director and co-founder of Artemis Intelligent Power, Dr Win Rampen. But the company's approach to business and hydraulics could never be described as “conventional” – in fact, that seems to be the secret of its recent success. Not only has it brought hydraulics into the digital age, but it's also followed its own path in business and grown at its own pace, owing nothing to banks or external investors.
Artemis has developed an “intelligent” hydraulics solution called “Digital Displacement” that promises to have a major impact on power and transport – used in everything from sports cars to diggers and tractors.
For wind turbines, the hydraulics solution transfers the power from the blades to the generator which converts the power into electricity, replacing the gearbox with a more robust, more compact and more lightweight solution which also offers very high efficiency – up to roughly 94 per cent. For motor vehicles, the hydraulic system transfers power from the engine to the wheels, and allows the storage of power recovered during braking which would otherwise be wasted. And Artemis has proved the efficiency of its solution by building a prototype car which has been independently tested at Millbrook by the Energy Saving Trust, who confirmed that it reduced fuel consumption by 50 per cent, in urban driving conditions.
Many people are surprised that hydraulics is attracting any scientific interest in the 21st century – as if it belongs to a previous era. “Conventional hydraulics were largely invented by the Victorians,” Rampen continues. “They are fairly efficient at full output, but the losses remain constant as you use less and less of the transmission.” And that is where Artemis has the edge, he explains, because the Digital Displacement system remains extremely efficient even at very low outputs, as a result of both the basic design of the valves, which permit free breathing, and the control technique, which allows a portion of the machine to be temporarily put into an idle mode – with very low parasitic loss.
According to Rampen, Digital Displacement also offers greater robustness and controllability than gearboxes and conventional hydraulics solutions. In addition, the intelligent hydraulics can operate efficiently in very different conditions – i.e. they operate quite happily at low or high speeds, and when the wind is low, they capture more power than a conventional turbine because they allow the rotor to spin more slowly, when it is more aerodynamically efficient. The Artemis system also allows you to generate power with a synchronous generator at medium voltage (11kV), saving the three per cent loss associated with low-voltage, full-power electronic conversion.
What makes the new hydraulics solution so different is the use of high-speed, electronically controlled poppet valves, connected to each pumping cylinder, which can be independently controlled by special software “to smoothly match the commanded output.” When every valve is needed at maximum power, operation is simple – the software shares the load among all the pumping cylinders. When only a few valves are needed, the software very quickly allocates the work to individual valves and spreads the load so that no single cylinder does more work than another. This means the intelligent hydraulics can cope with large and very sudden changes in power transmission – e.g. gusts of wind, frequent braking and accelerating or moving big piles of earth – and have a longer operational lifetime.
“We have cracked the efficiency problem that usually dogs hydraulics,” Rampen declares, “at the same time as improving the reliability and robustness, plus other knock-on benefits such as not needing the power semi-conductors usually needed to match grid frequency.”
Rampen also explains that with some applications, such as wind turbines, there can be a “big fight” in the gearbox due to spikes of power – or torque – that are imposed across it. This causes failures which necessitate replacement and typically costs the equivalent of one year's production – plus a “logistical nightmare” when it comes to repairs, particularly for off-shore machines. The hydraulic transmission can spread the load caused by these sudden shocks across 20 times as many lines of rolling contact than a typical gearbox. In addition, hydraulics can limit the shock by capping the maximum pressure. Repairs are also easier because you only need to service or replace relatively small parts and can dismantle the system on-site, rather than have to remove and replace a very large and very heavy gearbox.
In terms of cost, the basic saving comes from lower weight and the need for less steel in the turbine – with hydraulic machines weighing 20 tons compared to more than 50 tons for an equivalent gearbox at the 5MW power level.
The Artemis solution is not only different but also ahead of its time – but according to Rampen, its time may have come, because the company is talking with some very big players in the energy and transportation industries to licence its technology, adding to its current agreements with companies such as Bosch Rexroth and Sauer-Danfoss. This recent surge of interest from the renewables sector is not just because Artemis recently won the Innovator of the Year Award (2009) from the Carbon Trust, or because there's been a step-change in technology, but because the industry's perceptions are gradually changing. Rampen says hydraulics have often been ruled out for wind turbine transmissions, for instance, because of a perception that conventional hydraulic systems currently used in other areas of the machine are not efficient enough.
How it all started
The origins of Digital Displacement hydraulics can be traced back to Rampen's arrival in Edinburgh in 1978, soon after he graduated in mechanical engineering from Ryerson University in Toronto. Inspired by what he'd read about Professor Stephen Salter and his invention of the Duck, a revolutionary device designed to convert wave power into electricity, Rampen travelled to Scotland. Arriving at the King's Buildings campus where Salter was based, Rampen knocked on the first door he came to and met researcher Jamie Taylor, working in the wave tank built by Salter to test new “alternative energy” systems. Taylor phoned Salter to explain why Rampen was there, and relayed the following message from Salter: “Tell him to go away – unless he wants a job.”
A few minutes later, Salter arrived to “interview” Rampen while walking across the car park, and when he discovered that Rampen knew how to operate a lathe and could actually make things, offered him a job straight away – beginning a relationship which carries on today, with Salter a co-founder and director of Artemis.
One of the biggest challenges with Salter's Duck was how to cope with variable power input, coming from waves. Salter had realised that developing a power transmission system capable of transforming the slow, high-force, irregular motion of waves to a high-speed rotation needed to power a generator was as difficult as all the other problems involved in designing the Duck. To solve this problem, he put together a small team of engineers to explore the use of direct oil hydraulics.
Rampen spent two years with Salter and the late Robert Clerk in Edinburgh, assisting with the design of a very large hydraulic drive system. This incorporated precessing gyros to serve as an inertial reference which the “Ducks” could react against.
Rampen returned to Canada in 1981 shortly after which work on the Duck and many other alternative energy systems was closed down by the government. Then, in the late 1980s, Rampen came back to Scotland to work with Salter on a new project funded by SERC (the Science and Engineering Research Council), focusing on new hydraulics solutions for power take-off, using multiple valves and intelligent software – a new approach called Digital Displacement. Salter was still keen on developing hydraulics for large-scale renewable energy systems, but Rampen saw the need for a change in direction – and enormous potential in developing mobile hydraulic systems for use in agricultural and construction machines.
Rampen spent the next few years developing the new hydraulics concept at the University of Edinburgh, with financial support from JH Fenner, a specialist in power transmision and supplier of rubber-belting solutions for the coal mining industry. Fenner wanted a variable-flow water pump, and Rampen and his colleagues were able to use this project as the catalyst for developing the core technology for Digital Displacement. When Fenner was hit hard by the economic downturn of the early 1990s, the funding evaporated, and Rampen and Salter founded Artemis, setting up their headquarters in a Portakabin, sharing space with several other spin-outs from the University of Edinburgh, including Pelamis – now well established as a leading developer of wave-powered energy systems.
“Funding was a problem,” says Rampen, “partly because hydraulics was considered then to be a sunset industry and partly because most hydraulics companies had long ago disbanded their R&D departments.” For the first few years, the company funded its activities through consultancy, including work developing components for racing car suspension and steering.
Artemis also made an important strategic decision after being joined by Waverley Cameron, the company's chairman, who realised its future lay in becoming an R&D licensing company, rather than a small-scale manufacturer which would have to cope with every end-user of the company's products. This led to a partnership in 1998 with what was then Danfoss Hydraulics – a company which also saw the value of reducing energy loss at a time when the industry generally was not so committed to environmental and energy issues. Danfoss signed a licensing agreement with Artemis and also took a long-term view of its relationship with the young business. Since then, Artemis has managed to demonstrate 30 per cent savings in fuel for mobile hydraulics applications. Because environmental issues have also become more important in the intervening period, both partners have been proved right in their approach. “We hoped to bring something revolutionary to a conventional industry,” Rampen continues.
Artemis later signed a similar agreement with Bosch Rexroth, another major manufacturer of hydraulic machines, and continued to develop its technology in automotive applications.
Artemis continues to focus on two key areas of research – the core technology (hydraulic components – valves, cylinders and software) and applications such as agriculture, construction and materials handling. And, as Salter hoped when he invented the Duck, the research has returned again to large-scale solutions for wind and marine current turbines, with growing interest in these sectors promising to lead to further licensing agreements, as Artemis proves its new solution works with 1.5MW turbines.
Innovative technology is obviously critical to the success of Artemis, but its business philosophy also appears to have steered it along an “alternative” path. Rampen says the company has never wanted to depend on external investors and has focused on carefully building its team, which now numbers 26 people, including representatives from 10 different countries with a total of 5 PhDs between them. Since it was founded, Artemis has added just two or three people each year rather than pursuing expansion for its own sake, unlike many other new companies in the technology sector “who are always under pressure to grow too rapidly and deliver immediate returns with immature technology,” Rampen explains.
Rampen also thinks that some conventional attitudes to business growth are too formulaic when it comes to analysing the individual needs of different companies in different sectors. In his experience, external events which are outwith control can easily turn any company's plans upside down, although not always in a negative way – for example, the recent focus on carbon emissions has actually given Artemis a boost. Different business climates and different cultures can also be critical factors. What matters most to Rampen, however, is the team and providing solutions to the company's licencees, at the same time as developing the core technology so that it goes beyond current requirements, “constantly looking for synergies between applications and requirements.”
After making the first Artemis machines with one or two assistants, Rampen realised his most important task was to build “a competent and motivated team of people” to move the technology forward. “It is their combined dedication and skill that has enabled the technology to blossom,” says Rampen.
Artemis may have gone down “a path not recognised,” but Rampen also believes that, despite a certain serendipity along the way, the company has always been agile enough and able to change course when needed, “seize opportunities and adapt to change.” The company has also challenged the status quo in business and technology. “No-one else has gone so far towards creating efficient hydraulic drives,” he explains. “Hydraulics was a shrinking industry, resistant to change, but we have proved it has a future.”