Hydraulic Energy Harvesting Research Articles

In Situ Conversion of Universal Hydraulic Energy to Electricity to Address Common Challenges in Water Treatment

Diverse water treatment technologies are widely applied to manage water quality, with ubiquitous hydraulic energy remaining. Emerging hydraulic pressure–electricity conversion, along with its in situ utilization, provides a promising strategy for addressing common challenges in water treatment, which is convenient, efficient, and practical. This innovative concept has garnered extensive interest and has achieved exciting progress over the past decade. Piezoelectricity, which induces charges via mechanical deformation, serves as a direct hydraulic energy harvesting mechanism to achieve force–electricity conversion, opening new avenues for innovating traditional water treatment technology while compensating for its shortcomings. However, such in situ hydraulic–electricity coupling is still in its early evolutionary stage and requires thorough investigation to determine future development directions. With this in mind, we discuss hydraulic piezoelectricity as a means of addressing common challenges in water treatment technologies, with a focus on representative membrane fouling, catalytic reactions, and sludge dewatering. Then, we further explore other emerging hydraulic-based technologies, such as hydrovoltaics, solid–liquid triboelectricity, and other energy methods, such as thermal energy, to expand the paradigm and scenarios of in situ electricity advancements in the water treatment process.

A review of hydraulic energy harvester designs – current practice and future improvements

AbstractThis paper addresses the underexplored domain of hydraulic energy harvesters (HEH). Through a literature review, existing designs are identified, aiding in the categorisation of energy conversion technologies and fluid-mechanical interfaces. Recognizing a lack of standardized approaches to testing HEH, the paper proposes a re-configurable test platform. The platform, accommodating diverse configurations, operates at high pressures, aligns with existing hydraulic setups, and functions in static or dynamic modes. This tool aims to assist researchers further explore the implementation of HEHs.

Optimal hydraulic energy harvesting strategy for PaT installation in Water Distribution Networks

Water Distribution Networks (WDNs) represent a noteworthy field for possible implementation of Small Hydropower (SHP), by replacing Pressure Reduction Valves (PRV) with turbomachines, in particular Pump as Turbines (PaTs), to control and regulate the pressure, while harvesting energy otherwise wasted. Different models were developed to predict the performance and select the positioning of the PaTs for the maximum energy recovery but most of them neglect practical aspect such as: power grid limitations and optimal harvesting strategy. In this framework, we intend to propose a new method to select a PaT, defining its optimal working point, by introducing an energy exploitation coefficient. The proposed methodology is based on the experimental results of a real PaT tested in the high capacity hydraulic laboratory at Polytechnic University of Bari. Firstly, the selected commercial centrifugal pump was tested in both pump and turbine modes. Then, three different approaches, for the Best Efficiency Point (BEP) selection, are described and compared in terms of energy exploitation and capacity factor for a WDN. The first consists of selecting the BEP at the average flow rate, the second one considers the probability distribution of the flow rate and the corresponding available hydraulic energy, whereas the latter is based on the highest energy harvesting. By applying energy production, economic and environmental analyses, the new proposed methodology, based on the third approach, shows a remarkable advantage in terms of exploited energy. Indeed a remarkable 60% energy recovery is achieved with 334 ton CO2/year avoided. Furthermore, the impact of the electrical motor on the maximum power generation (cut-off) is considered. Eventually, useful insights for the future PaT selection and installation are discussed.

Modelling of the circular edge-clamped interface of a hydraulic pressure energy harvester to determine power, efficiency and bandwidth

There is an increasing desire to monitor and control hydraulic systems in an autonomous and battery-free manner. One solution to this challenge is to harvest hydraulic pressure ripples and noise by exploiting the piezoelectric effect. This paper develops a new generalized model of a hydraulic piezoelectric harvester based on a circular edge-clamped flat plate interface with a central piezoelectric stack. Such a model allows the relationships between harvesting performance and structure to be assessed in detail. It is demonstrated that the force-deflection relationship of a circular edge-clamped plate with a central lumped mass follows a cubic hardening Duffing equation. A single degree of freedom (SDOF) lumped-parameter model of the system is established where the nonlinear frequency response resulting from hardening nonlinearities are explored. The input mechanical energy and the output electrical energy both exhibit a quadratic nonlinear relationship with vibration amplitude. The maximum output occurs at the jump-down frequency and the overall energy conversion efficiency of the system is determined. The optimum resistance load for maximum output energy and energy efficiency are obtained as non-dimensional excitation frequency. Experimental validation is performed and good agreement is observed between model results and experimental measurements. The developed model provides important insights into the optimization of power output and response of future hydraulic energy harvesting devices.

Resonance wave pumping with surface waves

In this paper, we present a novel extension of impedance (Liebau) wave pumping to a free-surface condition where resonance pumping could be used for hydraulic energy harvesting. Similar pumping behaviours are reported. Surface envelopes of the free surface are shown and outline two different dynamics: U-tube oscillator and wave/resonance pumping. The latter is particularly interesting, since, from an oscillatory motion, a unidirectional flow with small to moderate oscillations is generated. A linear theory is developed to evaluate pseudo-analytically the resonance frequencies of the pump using eigenfunction expansions, and a simplified model is proposed to understand the main pumping mechanism in this type of pump. It is found that the Stokes mass transport is driving the pump. The conversion of energy from paddle oscillation to mean flow is evaluated. Efficiency up to 22 % is reported.