In 1974 in the wake of the first global energy crisis the UK began to look at large scale renewable energy sources. Professor Stephen Salter invented a wave energy device now remembered as the Salter Duck at the University of Edinburgh. Digital Displacement® hydraulics came about as a response to the exceptionally difficult problem of converting the slow, irregular, high force motion of ocean waves, to a constant speed rotation to drive a synchronous generator. The rethink of hydraulic power transmission, based on conventional pumping mechanisms and integrated active valves with microprocessor control, has resulted in very controllable fluid-power drivetrains with efficiencies matching, or even exceeding, those of electrical machines. The presentation will cover the early development of the technology and continue to the present where Artemis, now as a subsidiary of Mitsubishi, is assisting in the development of the 7MW SeaAngel offshore wind turbine with a Digital Displacement® driveline at its heart.

The fuel-saving Cat® 336E H Hybrid was launched in 2013 as the industry\'s first hydraulic hybrid excavator. With over 300 patents filed, the innovative hydraulic hybrid technology is a significant departure from the typical hybrid approach. To accomplish such a feat required an acute, intense focus on the customer and a diverse, global team empowered to drive an innovative solution. Learn the story behind the development of this game-changing product from Caterpillar.

The current trend of improving the efficiency of mobile machines indicates that hydraulic hybrids are playing an important role in order to realize a proper system solution. First machines like excavators, material handlers, harbour cranes and so on are already presenting very competitive solutions based on robust hydraulic accumulator technology. Beside the well known robust design which is very easy to handle, maintain and service the low investment costs for the additional components lead to a very attractive solution with ROIs between one and two years.
For some applications (depending on the load cycle) the efficiency and the energy capacity of the hydraulic accumulator itself becomes very important. In this case small improvements concerning the accumulators are determining whether the hybrid approach is successful or not.
Due to this fact Hydac concentrates on the development on a new generation of accumulators in order to operate the gas side nearly isothermal independent from the applied load cycle. This was realised by developing special foam materials which are integrated in the gas side of the accumulator. Several tests were applied within the last years demonstrating improvements on efficiency as well as an increased energy capacity with the same robustness, reliability and shelf life compared to the standard design.