With the acceleration of automobile electrification, the function of hydraulic system is being paid more attention. In the electrified structure, the battery life is the most important, and the hydraulic system is traditionally an energy consuming technology. Therefore, the improvement of the hydraulic system is the key to make the battery life of the electrified vehicle longer. In this case, one can say that the revival of hydraulic technology is in progress, said Brianna Jackson, industrial research analyst at interact analysis.
So far, automakers have explored various solutions aimed at improving the efficiency of their vehicles. In the hydraulic system, these changes are from the adoption of new technology to the redesign of the whole system. Through the test of these new components and systems, it is very clear that improving the vehicle efficiency through the hydraulic system will not be a solution suitable for all situations. Factors such as vehicle size, operating conditions, work cycle and the degree of control required by the application determine the feasibility of the relevant solutions. As automakers strive to achieve their electrification goals, these factors must be kept in mind when striking a balance between efficiency and practicality.
In this insight, we outline the challenges faced by the traditional hydraulic architecture after the electrification of off-road vehicles, and the advantages and disadvantages of emerging hydraulic technologies in this context.
Why must we change the status quo?
The advantage of traditional hydraulic systems has always been the ability to achieve unparalleled power density at extremely low cost. From the perspective of automotive OEM, this advantage is so great that the efficiency of the hydraulic system becomes an afterthought. Although automotive OEMs have not quickly eliminated or even changed this proven technology in their designs, it is becoming clear that hydraulic systems will need to significantly improve energy efficiency to adapt to electrification.
Some automakers have begun to electrify certain parts of their product portfolios and have made significant progress in evaluating the redesign of hydraulic systems. An example of the beginning of electrification is the electric small excavator. We estimate that in 2021, the market for hydraulic systems sold to this type of vehicles will be approximately $1.6 billion. Given their size, these vehicles will become a fertile testing ground for new hydraulic technologies. The electrification speed of the mini excavator is as follows.
Hydraulic technology -- electrified electromechanical actuator of small excavator
Earlier this year, bobcats launched their electric small crawler loader - t7x. The electric crawler loader is the result of cooperation with muger construction company. In addition to its electric power system, one of the most interesting design features of the car is the replacement of the hydraulic cylinder with a ball screw mechanical actuator. As mentioned above, electromechanical actuators have advantages in maintenance compared with hydraulic actuators. However, the most pressing constraint to replace the hydraulic cylinder is the loss of power density. Although in applications requiring less power density, electromechanical actuators provide benefits such as tighter control and less noise. In addition, in electrified vehicles, the removal of the hydraulic system can simplify the overall design.
In our recent insight, we outlined the best use cases for replacing hydraulic cylinders with electromechanical actuators. These use cases include vehicles of the material handling department, such as aerial work platforms and long-distance transport vehicles. However, the construction industry may also see more use of electromechanical pushers. In the right application, replacing hydraulic drive with electromechanical drive can reduce the total cost of ownership (TCO), because it saves fuel, reduces maintenance costs, and tax subsidies brought by the implementation of green technology.
One step change in efficiency
For many years, digital hydraulic technology has been a hot topic. The name of digital hydraulic technology comes from the quick on-off valve used in this technology. This technology can often bring obvious high efficiency when replacing traditional hydraulic components. In the past few years, we have seen various digital hydraulic solutions released on the market.
At the end of 2020, Volvo announced to cooperate with norrhedro to produce electric excavators. Norrhedro's patented technology, norrdigi system, has a multi chamber digital hydraulic actuator. This modular system greatly reduces the bill of materials by eliminating the main control valve and reducing the required hose length. The higher efficiency brought by the digital hydraulic system also supports the longer battery life, which is the key for the electric excavator to become a practical solution.
Another example in the field of digital hydraulics is Danfoss' widely discussed digital displacement pump (DDP). Such pumps have been shown to improve the fuel efficiency of internal combustion engine driven vehicles by 30%. Although the market's view on DDP is still developing, as the successor of traditional hydraulic technology, this technology has great prospects. Danfoss has consolidated its early position in the field of digital hydraulic.
Digital hydraulic technology provides higher efficiency while maintaining the traditional hydraulic structure to a large extent. For this reason, we believe that this technology has lasting power in the field of mobile hydraulics. By maintaining the traditional architecture, many of the disadvantages faced by other solutions, such as electromechanical actuators, can be avoided. We expect that with the development of off-road vehicle market towards electrification, more digital hydraulic technologies will be introduced.
Electro hydraulic drive
Electro hydraulic drive involves that each actuator is driven by its own special pump and motor. This reduces the throttling loss of the valve, and the modular nature of the technology simplifies the maintenance of the machine in many cases. In addition, the separation of power system and working function simplifies the design of electric machine. An example of an electro-hydraulic actuator is Bucher's helaxsystem. According to Bucher, the efficiency of this system is significantly higher than that of traditional drive systems. One of the ways to achieve this high efficiency is through the energy recycling process. In the traditional hydraulic system, an accumulator is required, and the herax can regenerate the energy into the battery through the electric motor of the drive system.
The main disadvantage of the electro-hydraulic solution is the increase of the initial cost, which is several orders of magnitude higher than the traditional hydraulic drive system. However, in terms of long-term total cost of ownership, higher efficiency can significantly reduce total operating costs. For this reason, electro-hydraulic structures, as a means of electrification, continue to gain the interest of many automobile manufacturers.
Last thought
Electrification has undoubtedly shaken the mature mobile hydraulic system market. Although there is no clear direction forward, it is clear that a one size fits all solution to optimize vehicle efficiency does not exist. Various vehicles, applications and requirements in the off-road market will continue to challenge mobile hydraulic suppliers. However, this will also provide opportunities for suppliers to innovate as automotive OEMs compete to electrify their fleets.
