Energy Efficiency Comparison of Hydraulic Accumulators and Ultracapacitors

Jorge Leon-Quiroga,Andres Gonzalez-Mancera,Brittany Newell,Jose Garcia-Bravo,Mahesh Krishnamurthy

doi:10.3390/en13071632

Jorge Leon-Quiroga, Andres Gonzalez-Mancera + Show 3 more

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https://doi.org/10.3390/en13071632

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Abstract

Energy regeneration systems are a key factor for improving energy efficiency in electrohydraulic machinery. This paper is focused on the study of electric energy storage systems (EESS) and hydraulic energy storage systems (HESS) for energy regeneration applications. Two test benches were designed and implemented to compare the performance of the systems under similar operating conditions. The electrical system was configured with a set of ultracapacitors, and the hydraulic system used a hydraulic accumulator. Both systems were designed to have the same energy storage capacity. Charge and discharge cycle experiments were performed for the two systems in order to compare their power density, energy density, cost, and efficiency. According to the experimentally obtained results, the power density in the hydraulic accumulator was 21.7% higher when compared with the ultracapacitors. Moreover, the cost/power ($/Watt) ratio in the hydraulic accumulator was 2.9 times smaller than a set of ultracapacitors of the same energy storage capacity. On the other hand, the energy density in the set of ultracapacitors was 9.4 times higher, and the cost/energy ($/kWh) ratio was 2.9 times smaller when compared with the hydraulic accumulator. Under the tested conditions, the estimated overall energy efficiency for the hydraulic accumulator was 87.7%, and the overall energy efficiency for the ultracapacitor was 78.7%.

Highlights

Energy consumption in the transportation and the industrial sector represented 72% of the total energy consumption during 2018 in the United States
The energy cycle efficiency is the ratio between the total energy released while discharging and the total energy stored while charging
The kinetic energy of the wheels would move the shaft of a hydraulic pump, which would move the fluid to the hydraulic accumulator in order to absorb the kinetic energy of the vehicle

Summary

Introduction

Energy consumption in the transportation and the industrial sector represented 72% of the total energy consumption during 2018 in the United States. Most of this energy (around 87%) comes from petroleum-based sources and natural gas [1]. Around 24% of the energy is spent by the agriculture, construction, and mining sectors. Many applications within these sectors use hydraulic equipment and hydraulic machinery, so improving the energy efficiency of the hydraulic systems that are already in use could have a large impact on the reduction of energy consumption and emissions.

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