Three Paths for Mobile Hydraulics Amidst Electrified Powertrains

Future mobile hydraulic system architectures amidst powertrain electrification will have a major impact on efficiency and sustainability efforts within the OEM off-highway industry.

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Powertrain electrification is viewed as an inevitability by most of those involved in the off-highway vehicle space. However, opinions regarding the extent of electrification reach, the timing and the means to electrify vary depending on who's being asked. Opinions become even more convoluted when discussing the impact that powertrain electrification is likely to have on the working functions of a vehicle.

Hydraulic system changes (often the least efficient system on an off-highway vehicle) are viewed by many vehicle original equipment manufacturers (OEMs) as necessary to achieve electrification ambitions. These changes range from the installation of more efficient hydraulic components to full hydraulic replacement, and the suitability of each potential solution is determined by factors such as the size of the vehicle and the number of working functions.

Future hydraulic system architectures amidst powertrain electrification can be grouped into three categories:

  • Electrified powertrain coupled with a centralized hydraulic system
  • Electrified powertrain coupled with a decentralized hydraulic system
  • Electrified powertrain with complete hydraulic replacement.

We’ve spent several months hosting interviews with hydraulic suppliers and vehicle OEMs alike to gather opinions on the suitability of each of these as vehicles become increasingly electrified. This insight will weigh the pros and cons of each, and offer an opinion on the suitability of each of these systems within future off-highway vehicles.

How quickly is powertrain electrification approaching off-highway?

It became clear after interviews with hydraulic vendors and vehicle OEMs that the trend toward electrification would hover and influence nearly every discussion point. Many hydraulics suppliers are fearful of electrification as they view it as an existential threat to the market, while others are embracing it as an opportunity to innovate and differentiate. In this context, we want to first express our perspective on how quickly the electrification trend is approaching in the off-highway space.

The forecast below is derived based on conversations with vehicle OEMS, the timing of public announcements from vehicle suppliers, and proposed legislation expected to drive electrification. This forecast is part of a broader annual study on the off-highway vehicle market. Penetration of battery electric powertrains in off-highway applications. Forklifts and aerial work platforms are excluded from these numbers.

Penetration of battery electric powertrains in off-highway applications is expected to grow rapidly over the next several years.Penetration of battery electric powertrains in off-highway applications is expected to grow rapidly over the next several years.Courtesy: Interact Analysis

The vehicle types included in this calculation are shown below:

  • Tractors
  • Combine harvesters
  • Full tree forestry system
  • Cut-to-length forestry system
  • Telehandlers
  • Forklifts
  • Boom lifts
  • Scissor lifts
  • Cranes
  • Crawler loaders
  • Crawler dozers
  • Excavators
  • Wheeled loaders
  • Backhoe loaders
  • CTL/Skid-steer loaders
  • Asphalt finishers
  • Motor graders
  • Rollers
  • Cement mixer trucks
  • Commercial dump trucks
  • Haul/dump truck
  • Underground LHDs
  • Mining shovels.

The first thing that becomes clear is the limited adoption of electrified off-highway vehicles through 2030. It’s true that while there has been a lot of discussion surrounding electrification for the last decade, the actual adoption of electrified off-highway vehicles remains limited. A combination of factors has led to slow adoption including battery limitations (both in terms of performance and cost), as well as a generally conservative approach by off-highway OEMs towards implementing significant changes within their vehicles.

By 2030, it's expected 150,000 battery-powered vehicles will be sold in the off-highway space (excluding forklifts, boom lifts and scissor lifts). 2030 could represent an inflection point for electrification in off-highway as it is the date many off-highway OEMs have set for achieving various emissions-related sustainability goals. From 2030 onwards, the market for these vehicles will expand.

Three paths mobile hydraulic architectures will take to support electrification 

As electrification approaches, there’s a large question looming over mobile hydraulic vendors regarding which direction to take their portfolios to support these changes. The market for mobile hydraulics is expected to move in three separate directions:

1. An electrified powertrain with a centralized hydraulic architecture

The largest gains vehicle OEMs will see from a sustainability perspective come when the vehicle becomes electrified. In certain cases, when this shift is made, it is unlikely that the hydraulic architecture within the vehicle system will change dramatically. Under a centralized architecture, there will be one or a few centralized pumps driving fluid throughout the system to the working functions. Within certain vehicles, this design just makes practical sense. It is the most cost-effective from a production standpoint, and represents the least amount of risk associated with system redesign.

This system requires the least amount of redesign from a vehicle OEM perspective, but it does not address the efficiency issues that arise when utilizing a traditional hydraulic architecture. Under this architecture, the losses resulting from the hydraulic system remain large. As a result, it becomes difficult to electrify large vehicles or those with a high number of working functions due to limitations on the battery side of the equation.

Pros of an electrified powertrain w/ centralized hydraulic system:

  1. Most cost-effective (from production standpoint)
  2. Legacy system i.e. thoroughly vetted/tested. Represents the current status quo which is perceived largely to be less risky from a design perspective.
  3. Well-suited for tractor applications which need to support non-standard implement systems. Maintaining a legacy hydraulic system in this case can make integrating with 3rd party implement systems more feasible.

Cons of an electrified powertrain with a centralized hydraulic system:

  1. The least efficient system of the three being considered.
  2. Still requires a trained fluid power engineer for maintenance.
  3. Becomes less efficient as the number of axes in a system increases.

2. An electrified powertrain coupled with a decentralized hydraulic system

In this architecture, the working functions of a machine are independently controlled. Take an excavator for example, the three main working functions include a boom, arm, and a bucket. Each will require different pressures to operate optimally. Under a decentralized hydraulic system, each working function would have its own electric motor, pump, and cylinder controlling the movements.

Pros of an electrified powertrain with a decentralized hydraulic system:

  1. More efficient than a centralized system. The higher efficiency of the hydraulic system means an extension of the battery life on a vehicle which is a key barrier to electrification.
  2. Is a middle ground between electromechanical actuation and a centralized hydraulic system.
  3. Retains the benefits of fluid power physics i.e. power density & shock absorption.

Cons of an electrified powertrain with decentralized hydraulic system:

  1. Adds weight to the overall system in most cases due to the number of electric motors required.
  2. Represents a fairly significant design change which goes against the conservative instincts of vehicle OEMs.

3. Hydraulic replacement with electromechanical actuators

Likely the most worrying for hydraulics suppliers, is a hydraulic replacement. Vehicle OEMs have already been trialling vehicles with complete hydraulic replacement. These tend to be machines on the smaller-end of the spectrum which are used more heavily in urban atmospheres. For example, loaders have been observed as some of the first vehicle types on the market with complete hydraulic replacements.

In 2022, Doosan Bobcat partnered with Moog Construction to produce an all-electric compact tracked loader. The result, the Bobcat T7X, represents one of the first vehicles to come to market that is completely electric i.e., no hydraulics at all. Adoption of the vehicle is still low given the price point has come in substantially above its non-electric alternative. Despite the low adoption, this development gives the market a window into which vehicles can reasonably handle hydraulic replacement.

Pros of a hydraulic replacement with electromechanical actuators:

  1. Hydraulic replacement eliminates a messy hydraulic system in favor of one that is more harmonious with an electric powertrain. This can serve to simplify overall system design.
  2. Future proofing the machine to allow for more sophisticated feature sets. Under a fully electric system, a vehicle OEM has a much greater ability to make incremental changes to its machine without completely redesigning the system.

Cons of a hydraulic replacement with electromechanical actuators: 

  1. Limited ceiling of applicability due to battery technology constraints. Currently, only low-power applications are suitable, and practical limitations to electromechanical actuators may limit the prospects for hydraulic replacement in machines of higher power. The size of electromechanical actuators is prohibitively large when you get above ~15-ton machines.
  2. Hydraulic cylinders can act as shock absorbers thanks to the physics of fluid power. This is not the case with electromechanical actuators. Although engineers have found ways of compensating for this in the design of these actuators, there are still questions regarding performance in the field as a result.
  3. The economics of hydraulic replacement are still difficult to justify. Electromechanical actuators can be more than twice the cost of their fluid power counterparts.

Sustainability rapidly approaching for the OEM off-highway market

There is room for each of these architectures within the off-highway landscape. Over time, a mix of these approaches will emerge and the choice to go with one over another will ultimately be a function of the unique requirements of the vehicle. In any case, the hydraulics market seems to be at an inflection point.

With vehicle design changes often taking 3 to 5 years or more to test and bring to market, the 2030 timeline for sustainability goals that many off-highway OEMs have communicated is rapidly approaching. These design changes will begin occurring at an increasing rate, and when the hydraulic system remains intact, it will be looked upon as a "low hanging fruit" to reduce losses in the overall vehicle. This inflection point will be an opportunity for mobile hydraulic vendors to differentiate themselves from each other on the basis of efficiency which is increasingly valued at a premium.

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