Hydraulic Energy Recovery System Utilizing a Thermally Regenerative Hydraulic Accumulator Implemented to a Reach Truck

The implementation of an energy recovery system for retreiving otherways wasted energy is an effective method for reducing the overall energy consumption of a mobile machine. In a fork lift, there are two subsystems that can be effectively modified for recovering energy. These are the driveline and the lift/lower function of the mast. This study focuses on the latter by studying a recovery system whose main component is a hydraulic transformer consisting of a hydraulic motor, a variable displacement pump and an induction motor. Since the flow rate/pressure - ratio can be modified, the utilization of the hydraulic transformer enables downsizing of the accumulator volume. However, the decrease of the gas volume leads to an increase in the compression ratio of the accumulator, which in terms leads to higher gas temperatures after charging and consequently to higher thermal losses during holding phase. In order to reduce these losses, a thermally regenerative unit was implemented to the gas volume of an accumulator to reduce the temperature build up during charging. In this study, the effect of improving the thermal characteristics of the accumulator to the efficiency of the whole energy recovery system is investigated by means of measurements

Hydraulic Energy Recovery System Utilizing a Thermally Regenerative Hydraulic Accumulator Implemented to a Reach Truck

The implementation of an energy recovery system for retreiving otherways wasted energy is an effective method for reducing the overall energy consumption of a mobile machine. In a fork lift, there are two subsystems that can be effectively modified for recovering energy. These are the driveline and the lift/lower function of the mast. This study focuses on the latter by studying a recovery system whose main component is a hydraulic transformer consisting of a hydraulic motor, a variable displacement pump and an induction motor. Since the flow rate/pressure - ratio can be modified, the utilization of the hydraulic transformer enables downsizing of the accumulator volume. However, the decrease of the gas volume leads to an increase in the compression ratio of the accumulator, which in terms leads to higher gas temperatures after charging and consequently to higher thermal losses during holding phase. In order to reduce these losses, a thermally regenerative unit was implemented to the gas volume of an accumulator to reduce the temperature build up during charging. In this study, the effect of improving the thermal characteristics of the accumulator to the efficiency of the whole energy recovery system is investigated by means of measurements

Hydraulic Energy Recovery System Utilizing a Thermally Regenerative Hydraulic Accumulator Implemented to a Reach Truck

The implementation of an energy recovery system for retreiving otherways wasted energy is an effective method for reducing the overall energy consumption of a mobile machine. In a fork lift, there are two subsystems that can be effectively modified for recovering energy. These are the driveline and the lift/lower function of the mast. This study focuses on the latter by studying a recovery system whose main component is a hydraulic transformer consisting of a hydraulic motor, a variable displacement pump and an induction motor. Since the flow rate/pressure - ratio can be modified, the utilization of the hydraulic transformer enables downsizing of the accumulator volume. However, the decrease of the gas volume leads to an increase in the compression ratio of the accumulator, which in terms leads to higher gas temperatures after charging and consequently to higher thermal losses during holding phase. In order to reduce these losses, a thermally regenerative unit was implemented to the gas volume of an accumulator to reduce the temperature build up during charging. In this study, the effect of improving the thermal characteristics of the accumulator to the efficiency of the whole energy recovery system is investigated by means of measurements

The effects of control methods on energy efficiency and position tracking of an electro-hydraulic excavator equipped with zonal hydraulics

Compared to conventional central hydraulic systems still typically used in most off-road machinery, the main advantages of zonal hydraulics are lower pressure losses, lower power demand, and thus, lower energy consumption on a system level and easy automatisation. In this case study, zonal hydraulics is realised with Direct Driven Hydraulics (DDH), and it is implemented as a replacement for the conventional centralised hydraulic system of a micro excavator. A simulation model for the front attachment of the excavator with three individual DDH units is presented. The proposed model of a single DDH unit was partially validated with a standalone test setup. Various common working cycles, such as digging and dumping with differing payloads and levelling, were adopted for this simulation study. Two controllers—a conventional proportional-integral-derivative (PID) controller and a flow-rate-matching feedforward plus PID controller—were designed for each DDH unit. Thereafter, detailed comparisons were provided, consisting of energy consumption, energy efficiency and position tracking performance between the two controllers. The results showed that the proposed feedforward plus PID controller had better performance than a conventional PID in the studied case. By adopting this controller, higher system energy efficiency (improved by 11–24% without regeneration and by 8–28% when considering regeneration) and better position tracking performance (root mean square tracking error and max errors lowered by 20–87% and 35–83%, respectively) were achieved simultaneously. Therefore, this work can be applied to zonal hydraulics to facilitate the electrification and automatisation of construction machinery.Peer reviewe

Energy efficient hydraulic system topologies for load-haul-dump machine

Diesel engine powered non-road mobile machines have been noted to be a considerable source of pollutant emissions. It is one reason for a growing trend where the powertrains of heavy mobile machinery including diesel engines are being replaced with hybrid or fully electric powertrains. Battery-powered non-road mobile machines require that more energy efficient hydraulic topologies are developed for the machines. Therefore, in this research novel hydraulic topologies were compared to evaluate efficiency characteristics of them in a load-haul-dump machine application. A system level simulation model of a load-haul-dump machine was developed, and its energy efficiency was compared with a model of a diesel-powered machine by driving a test cycle in a virtual mine with both models. Energy efficiencies of three different hydraulic bucket system topologies - load-sensing, direct driven hydraulics, and tandem pump system - were compared. The results of the test cycle emphasized the advantages of an electric powertrain. Especially, the energy recovery in the downhill, where over 50 percent of the total energy used for other sections of the driving cycle were regenerated to the battery. The direct driven hydraulics in the steering system reduced the energy consumption. In the analysis of the bucket systems, the direct driven hydraulic system had about 60 percent and the tandem pump system had about 50 percent smaller energy consumption than the load-sensing systemPeer reviewe

Additively manufactured high-performance counterflow heat exchanger

The purpose of this article is to demonstrate that additive manufacturing is a viable method for producing counterflow heat exchangers that have a very high power to volume ratio. For this study, a heat exchanger with 144 flow channels in a checkerboard pattern was designed and additively manufactured from AlSi10Mg. The heat exchanger was tested by measuring the heat transfer between two liquids in a counterflow set-up, where it reached exceptionally high performance when considering its volume and weight. The heat transfer properties of the heat exchanger were verified analytically through calculations, which identified that the high surface roughness of the channels provides a significant improvement in heat transfer properties. The heat transfer capabilities were measured on two separate occasions to investigate the possible change of properties of additively manufactured heat exchangers over time when used with tap water. A moderate decrease in heat flow and increase in pressure drop were noted between the measurements. The deterioration of heat transfer capabilities could present a significant challenge for additively manufactured heat transfer applications and will be closely examined in future research.Peer reviewe

Energy Balance of Electro-Hydraulic Powertrain in a Micro Excavator

This paper presents the experimental results of the study performed with an electrified small sized excavator, a 1.1- tonne JCB Micro, equipped with conventional hydraulics. The highlighted points in this study are the overall energy balance of the electro-hydraulic powertrain of this excavator and the power losses in individual components. The measured energy balance of the electric motor powered system is compared with the simulation data obtained from a preliminary simulation model of the system. The empirical evidence and the results of the preliminary simulation model will be in future research utilized to discover and compare new alternatives for powertrain architectures.Peer reviewe