CAPTURING AND STORING THE ENERGY RECOVERED FROM …

ISSN 1454 - 8003 Proceedings of 2016 International Conference on Hydraulics and Pneumatics - HERVEX November 9-11, Baile Govora, Romania

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CAPTURING AND STORING THE ENERGY RECOVERED FROM HYDRAULIC DRIVE SYSTEMS

OF MOBILE MACHINERY AND EQUIPMENT

Corneliu CRISTESCU1, Catalin DUMITRESCU1, Radu RĂDOI1, Genoveva VRÂNCEANU1, Constantin CHIRITA2

1 INOE 2000-IHP, Bucharest, [email protected]

2 “Gheorghe Asachi” Technical University of Iassy, [email protected]

Abstract: The paper presents some considerations regarding the new technologies, used increasingly more, namely energy recovery technologies, used in hydraulic drive systems in order to increase their energy efficiency. This technology represents a new trend in the development of thydraulic drive systems and it aims to develop and implement devices and systems for kinetic or potential energy capture, storage and reuse in order to save energy and, where appropriate, reduce adverse environmental impact and where the main problem is storing the energy recovered. In the second part, there are presented some experimental models, which confirm the possibilities and the technical solutions adopted for capturing, storing and reusing kinetic and potential energy. There are presented some graphical results, which clearly show the phases of energy capture, storage and reuse, specific for energy recovery concept, and also some conclusions.

Keywords: Energy recovery, energy conversion, energy capture, energy storage, hydraulic drive system, energy efficiency

1. Introduction

Generally, for the driving of machinery, equipment and technological systems, most part of installed power is used in the phase of starting/accelerating, in order to accumulate a kinetic energy or a potential energy, useful in their operation. After consuming the active phase of the work cycle and after achieving useful mechanical work, in these systems there remains unused amount of energy available, which, before resuming the next work cycle, is removed from the system by conventional methods, dissipative, i.e. by braking, in which the energy is lost irretrievably in atmosphere, sometimes with negative impact on the environment [1]. For engineers, the technical problem that needs to be solved is to recover this available energy, and then reuse it in active phases of the next work cycle, in order to improve the energy efficiency of driving systems of machines, equipment and technological systems. That is why in the last decade engineers have started a number of actions to identify these situations, design and elaborate technical solutions for the newly developed equipment, but also for the existing one, by which a part of this energy available can be captured, stored and then reused in the next work cycle, in order to greatly increase energy efficiency of the systems [2]. For the mobile machinery and equipment, the main problem is capturing and storing the available energy, but this is relieved that the stored energy is reused in the next operating cycle. In case of recovering kinetic energy from motor vehicle braking [3], by adding an energy recovery hydraulic system, the vehicle becomes a Hybrid vehicle, which works using the mechatronics technology [4]. In the following, the paper presents some experimental results obtained by the Hydraulics and Pneumatics Research Institute INOE 2000-IHP from Bucharest, regarding the development and implementation of some hydraulic systems for energy recovery, in order to demonstrate the possibility and viability of technical solutions chosen, and also to show the increase of energy efficiency, in mobile and industrial hydraulic drive systems.


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2. Lifting and lowering equipment with energy recovery system

To demonstrate the possibility of potential energy recovery, in INOE 2000-IHP there has been developed a model of equipment for lifting masses / weights at various heights, hydraulically driven and provided with energy recovery system, based on a rotary hydraulic motor. The concept of demonstration model for the recovery of potential energy is based on a hydro-mechanical assembly, simulating lifting and lowering equipment, Figure 1, with a system which actuates the cable drum from a hydrostatic unit / machine. The equipment may be used in mechanical workshops, in stages of assembly processes. As we know, potential energy is calculated using the equation:

𝐸𝑝 = 𝑚𝑔ℎ = 𝐺ℎ , (1)

where: 𝐸𝑝 - is potential energy; m - mass of the object that descends under gravity; g - gravitational

acceleration; h - height at which the object is at a time; G - high weight, which lowers the gravitational field. Constructive lifting equipment with energy recovery consists of the following main parts: 1- lifting and lowering device, Figure 1; 2- module of capturing, storing and reusing, Figure 2; 3- mobile hydraulic station, Figure 3.

a)

b)

Fig. 1. Lifting and lowering device, layout (a) and physical model (b)

The lifting device, Figure 1, a) and b), consists of a welded metal structure set on a movable frame on wheels, with a driving drum from a hydraulic axial piston machine. It also has a system of pulleys, one of which is mobile, leading to duplication of effort for weight lifting by cable. When lowering loads, at a controlled rate in the gravitational field, potential energy, transformed by using the system of cables and reels into kinetic energy of rotation of the cable drum / drum, is converted into hydrostatic energy by machine / hydrostatic rotary unit, which is stored and then reused in the lifting phases. First, it must be noted that energy recovery is not limited to use of the hydraulic pump in some inactive phases of a technological system, but it is also intended for storage and reuse. The module of capture, storage and reuse of energy is presented in Figure 2 and the mobile hydraulic station -in Figure 3. At the controlled descent of the load / weight, the torque generated by the drum Cable and the tangential force drives a hydrostatic machine, which now works as a pump. Thus, potential energy


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is converted into hydrostatic energy, which is then stored in a battery of hydro-pneumatic accumulators, then reused in the next work cycle. These complex functions are performed by a module, which is made with a recovery and reuse energy system. This system is now under the phase of patenting by OSIM Bucharest.

Fig. 2. Module of capturing, storing and reusing Fig. 3. Mobile hydraulic station

An important part of the hoisting equipment with potential energy recovery is the mobile hydraulic unit. It moves and connects with the hydraulic motor which drives the rotary drum with cable, through some hydraulic hoses with quick couplers. The hydraulic station has been constructed from a standard station, composed of tank, electro-pump, hydrostatic valve, adapted by mounting the components of recovery module, such as hydraulic distribution block, hydraulic accumulator for storage of recovered energy and the directional valve for connecting pumps in the recovery mode phase. Figure 4 presents the simplified hydraulic diagram of the hoisting / lowering equipment with energy recovery system, and Figure 5 presents the general view over hoisting / lowering equipment, inside of the Laboratory of Hydraulic Transmissions with Energy Recovery Systems from INOE 2000-IHP. The technical solution is patent pending.

Fig. 4. Hydraulic diagram of the hoisting / lowering equipment with energy recovery system


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a) Left view

b) Right view

Fig. 5. General view over the hoisting / lowering equipment

The presented model allows conducting experiments necessary to obtain plots of dynamic parameters developed: hoist force, stroke, drive pressures, amount of energy storage and reuse. Tests carried out will validate the proposed constructive solutions. Lifting equipment with potential energy recovery system, by converting it into hydraulic energy, stored and reused, are of a high innovative level, applicable to machines.

3. Lifting work platform with hydraulic energy recovery system An important category of hoisting equipment are the hydraulically driven lifting platforms, used in mechanical workshops or for people with walking disabilities, to access various public buildings, see Figure 6. In all these devices or platforms, most with hydraulic drive, in each upward stroke is generated the energy required to carry out the work necessary to lift the load, and then the potential energy gained is dissipated into the environment, usually by liquid restriction; thus, the liquid is heated and additional energy for cooling the fluid is required. In these circumstances, return in such equipment is low, and this requires measures to improve it. The technical problem is whether we can recover at least some of this potential energy to reuse the energy recovered during active hoisting phases of the next work cycle, which leads to substantial increase in energy efficiency or lower energy consumption. To this end, an energy recovery and storage system has been designed and developed, see Figure 7. The technical solution is patent pending.

Fig. 6. The initial lifting platform

Fig. 7. The system for potential energy recovery and storage


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In the following lines, Figure 8 shows an experimental model of hydraulic lifting platform, actuated with a linear hydraulic motor (hydraulic cylinder) and equipped with a hydro-pneumatic system for recovery and reuse of potential energy to the end of lifting phase; the model is developed in INOE 2000-IHP. The hydraulic module for energy recovery complements the classic hydraulic drive in order to recover the potential energy at lowering the load (weight), by capturing and storing it in hydraulic accumulators, followed by reuse in the phase of lifting the load. The hydraulic module for recovery of potential energy, which is implemented on the classic hydraulic system of the platform, is shown in Figure 9 and consists of the following parts: Pos. 15 = stroke transducer; pos. 16 = ф 63 glycerin manometer, 0-250 bar; pos. 17 = accumulator safety block Dn 10 Pn = 400 bar; pos. 18 = Hydraulic accumulator with V0 = 2.5 dm3 and Pn = 400 bar. The system also has a hydraulic block (19) where necessary hydraulic elements (distribution, flow transducer, check valves, etc.) are mounted. The hydraulic system for recovery of potential energy in the hoisting platform is now in patent pending at OSIM Bucharest.

Fig. 8. Lifting platform with energy recovery system

Fig. 9. Hydraulic diagram of platform with energy recovery system

4. Experimental model for rotating kinetic energy recovery

In this section we present an experimental model which was conceived as a new technical solution for an energy recovery system, from an electro-mechanical-hydraulic drive system, belonging to a technological equipment, having a mechanical structure with rotational mechanism hydraulically actuated. The main part of the experimental model consists of a Mechanical System, which contains a mechano-hydraulic giroinertial device with horizontal axis, as shown in Figure 10, which is a mechanical ensemble (3) that ensures hydrostatic power transmission, by conversion into mechanical energy by using a reversible hydraulic machine (1), with the horizontal axis coupled to the axis of the rotational mass, and also a measuring box, which gives the possibility to measure the torque and rotational speed, by using a special torque and rotational speed transducer (2). The


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other three elements, 4, 5 and 6, depict the strengthened bearing (4), the axis of the rotating mass (5), and respectively the flange (6) of the rotating mass (M) [5]. The second ensemble of the experimental model, shown in Figure 11, consists of a Hydraulic System, composed of a conventional hydraulic station (1), with electric control panel (2), and also ERHS-the Energy Recovery Hydraulic System (3).

Fig. 10. Giroinertial device

Fig. 11. Hydraulic station with ERHS

As we know, rotational kinetic energy is calculated using the equation:

𝐸𝑘 =1

2 𝐽𝜔2 (2)

where: Ek - is the rotational kinetic energy; J - inertial mass moment of the object being in rotational movement; ω – angular velocity of the rotational mass. In order to develop the experimental research regarding the recovery of rotational kinetic energy, there has been simulated a potential technological equipment, having a mechanical structure with a rotational mechanism (MROT) with hydraulic actuation (SHP). The new technical solution for an energy recovery system (ERHS) has been implemented on this experimental model. There followed getting a small experimental model that does not require much large masses in rotational movement (MR), Figure 12 and Figure 13, [6]. The technical solution is patent pending.

Fig. 12. Experimental model concept

Fig. 13. The experimental model

In order to monitor and record the evolution of the main functional parameters of the experimental model, for recovery of rotational kinetic energy, it was necessary to design and develop a special data acquisition system, which allows computerized processing of signals collected from all the existing transducers. To demonstrate the possibility for recovery of rotational kinetic energy it was necessary to conceive a special test stand, Figure 14, [6].


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Fig. 14. General diagram of the test stand

The test stand, presented in Figure 15 and Figure 16, consists of three main systems: a mechanical system, a hydraulic system and an electro-informatics system.

Fig. 15. Overview of the test stand

Fig. 16. The electro-informatics system

The demonstrative model for recovery of rotational kinetic energy, which was subjected to tests regarding the demonstration of the possibility to recover rotational kinetic energy, has many sensors and transducers implemented on the mechanical system and on the hydraulic system, mounted in order to monitor and record the evolution of the main functional parameters during the experimental tests. There are: torque and rotational speed transducer, Figure 17, pressure transducers, Figure 18, gear wheel flow meter, Figure 19, and turbine flow meter, Figure 20.

Fig. 17. Torque and rotational speed transducer

Fig. 18. Pressure transducers


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Fig. 19. The gear wheel flow meter

Fig. 20. The turbine flow meter

Some experimental results

To demonstrate the possibility to recover the rotational kinetic energy, and also to verify the technical solution adopted, the demonstrative model was subjected to a set of testing samples. In the following we present only an example for graphical variation of the main parameters of the system, for a certain value of pressure limit, for a certain value of rotating mass and a certain value of nitrogen initial pressure in the hydro-pneumatic accumulator. Figure 21 and Figure 22 present the mechanical parameters: rotational speed [rpm], torque [Nm] and number of rotational cycles [-].

Fig. 21. Rotational speed and torque variation

Fig. 22. Rotational speed and number of cycles

Using the monitoring and data acquisition system a lot of graphical results have been obtained. Figure 23 presents, up to down, the variations of the main hydraulic parameters of the system: p1- inlet pressure in hydraulic motor [bar], p2- outlet pressure from hydraulic motor [bar], p3-storing subsystem pressure [bar] and oil flow variation [lpm]. Figure 24 presents the energy parameters:


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acceleration power [W], acceleration energy [J], recovered power [W], recovered energy [J], and also recovery energy coefficient [-].

Fig. 23. Variation of hydraulic parameters

Fig. 24. Variation of energy parameters

5. Conclusions

The paper presents few of the experimental hydraulic models conceived by INOE 2000-IHP, which aim to demonstration the possibility for recovery of energy remaining after useful mechanical work is achieved, in mechanisms with hydraulic drive, and also the possibility for reuse of the recovered energy, in the active phases of the next work cycle, in order to increase energy efficiency of hydraulic systems. Both the experimental models for potential energy recovery and a model for rotational kinetic energy recovery are described. The experimental results, already obtained in recovery of rotational kinetic energy, have validated the technical solutions addressed, and by experimental measuring they confirmed the real possibility to recover about 55-60% of energy, which confirms theoretical results regarding energy recovery in braking phase, which is over 65% [7].


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The adopted technical solutions can be promoted in the new technological equipment, in the design stage, as well as in the existing equipment, where they can be implemented in the phase of rehabilitation. The users of the research results are the manufacturers of automotive and industrial technological equipment with hydraulic drive, which can adopt this innovative technology to achieve important and great benefits.

Acknowledgments

Research presented in this paper has been conducted with financial support of Romanian National Authority for Scientific Research and Innovation (ANCSI), under the national research programme NUCLEU-2016, research project titled “Physics of processes for reducing energy losses and developing renewable energy resources by use of high performance equipment”, project code 16-40-03-01, Financial Agreement no. 5N/2016.

References

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