Tag Archives: Energy Storage

Analytical and experimental evaluation of energy storage using work of buoyancy force


Abdul Hai Alami – Journal of Renewable and Sustainable Energy, 2014

Abstract

This paper presents theoretical formulation of, and experiments on a method of energy storage using the work of buoyancy force. The experiments proved that the energy storage using buoyancy force is an effective approach, as the experimental efficiency was found to exceed the theoretical estimation due to material properties of the buoys. The storage of mechanical energy without subsequent conversion into electrical energy has many advantages, including more compact storage setups, higher energy density retrieval, and higher efficiencies. For the current system, the efficiency of energy storage exceeds 37%. This value corresponds to earlier work by the author conducted for a single buoy, extending the prospects and applications of this approach to a better position in non-conventional energy storage applications.

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Filed under Component Development, Experiments


Elisabetta Tedeschi, Jonas Sjolte, Marta Molinas, and Maider Santos – Energies, May 2013

Abstract

The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal framework for wave energy exploitation, due both to resource availability and to the current high cost of electricity that mostly relies on diesel generation. Energy storage can be the enabling technology to match the intermittent power generation from waves to the energy needs of the local community. In this paper real data from La Palma, in the Canary Islands, are used as a basis for the considered test case. As a first step the study quantifies the expected power production from Wave Energy Converter (WEC) arrays, based on data from the Lifesaver point absorber developed by Fred Olsen. Then, a stochastic optimization approach is applied to evaluate the convenience of energy storage introduction for reducing the final cost of energy and to define the corresponding optimal rating of the storage devices.

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Filed under Economics, Grid

Assessing the China Sea wind energy and wave energy resources from 1988 to 2009


C-W Zheng, J. Pan, J-X Li – Ocean Engineering, June, 2013

Abstract

In this study, the wave field in the China Sea was simulated over the period from 1988 to 2009 using the third-generation wave model WAVEWATCH-III (WW3), with Cross-Calibrated, Multi-Platform (CCMP) wind field as the driving field. The China Sea wind energy density and wave energy density were calculated using the CCMP wind and WW3 model simulation results. The China Sea wind energy and wave energy resource were analyzed, synthetically considering the value of energy density, probability of exceedance of energy density level, exploitable wind speed and exploitable significant wave height (SWH), the stability of energy density, total storage and exploitable storage of energy resources, thus providing the guidance for the location of wind and wave power plants. Our results show that most of the China Sea contains abundant wave energy and offshore wind energy resources, with wind energy density above 150 W/m2, wave energy density above 2 kW/m, high occurrence of exploitable wind and wave energy in large scale waters, wind energy storage above 2×103 kW h m−2, wave energy storage above 4×104 kW h m−1. The richest area is in the northern South China Sea (wind energy density 350–600 W/m2, wave energy density 10–16 kW/m, wind energy storage 3×103–5×103 kW h m−2, wave energy storage 8×104–16×104 kW h m−1), followed by southern South China Sea and the East China Sea (wind energy density 150–450 W/m2, wave energy density 4–12 kW/m, wind energy storage 2×103–4×103 kW h m−2, wave energy storage 4×104–12×104 kW h m−1). The Yellow Sea and Bohai Sea resources are relatively poorer (wind energy density below 300 W/m2, wave energy density below 4 kW/m, wind energy storage below 2.5×103 kW h m−2, wave energy storage below 6×104 kW h m−1).

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Filed under Resource Assessment, Resource Characterization, Wind

SMES-Battery Energy Storage System for Conditioning Outputs From Direct Drive Linear Wave Energy Converters


X. Xiao, Q. Kang, R. Aggarwal, H. Zhang, and W. Yuan – IEEE Transactions on Applied Superconductivity, June, 2013

Abstract

The power from direct drive linear wave energy converter (DDLWEC) consists of frequent power fluctuations and long-term power fluctuations due to oceanic conditions. A 60 kJ superconducting magnetic energy storage is designed to work in conjunction with batteries as a hybrid energy storage system for conditioning the outputs from DDLWECs. The issues of the intrinsic power fluctuations of DDLWECs and the intermittent power generation are both addressed by the hybrid energy storage system.

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A review of energy storage technologies for marine current energy systems


Z. Zhou, M. Benbouzid, J.F. Charpentier, F. Scuiller, and T. Tang – Renewable and Sustainable Energy Reviews, February, 2013

Abstract

Increasing concerns about the depletion of fossil resources and the issue of environment lead to a global need for producing more clean energy from renewable sources. Ocean is appreciated as a vast source of renewable energies. Considering marine renewable energies, it can be noticed that significant electrical power can be extracted from marine tidal currents. However, the power harnessed from marine tidal currents is highly fluctuant due to the swell effect and the periodicity of the tidal phenomenon. To improve the power quality and make the marine generation system more reliable, energy storage systems can play a crucial role. In this paper, an overview and the state of art of energy storage technologies are presented. Characteristics of various energy storage technologies are analyzed and compared for this particular application. The comparison shows that high-energy batteries like sodium–sulphur battery and flow battery are favorable for smoothing the long-period power fluctuation due to the tide phenomenon while supercapacitor and flywheel are more suitable for eliminating short-period power disturbances due to swell or turbulence phenomena. This means that hybrid storage technologies are needed for achieving optimal results in tidal marine current energy applications.

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A Novel Design of Wave Energy Harvest Device with Flywheel Energy Storage System


K Lin, YH Joo, S Helkin C Ham

Abstract
This paper describes a novel design of a wave energy harvest device that utilizes a flywheel energy storage (FES) system to yield increased power generation.  The buoy design is moored to the ocean floor via a cable; as the buoy is heaved vertically by ocean waves, the cable rotates a pulley which in turn drives the rotor of an onboard generator.  A ratchet within the pulley allows the rotor to only be turned in one direction.  To prevent large tensions from begin imposed on the cable by the back torque from the generator, a flywheel energy storage system is used. As the buoy is heaved vertically by incident waves, the electric load on the generator is removed, resulting in all of the energy extracted by the buoy to be stored in the flywheel system.  Consequently the buoy is less restricted by high tensions and able to closely follow the motion of the waves, even while using a large generator with a high back torque coefficient.  As the buoy moves downward after being heaved, the load is re-coupled to the generator, transferring the energy stored by the flywheel to the generator.  Essentially the FES system trades power generation time for improved buoy motion.  The focus of the paper is not to optimize the design of the buoy, but rather demonstrate the effectiveness of the FES system for the buoy design with arbitrary parameters.  Simple simulations for a small buoy confirm the effectiveness of the proposed flywheel energy storage system—without it the wave energy harvest device produced only 90.0watts of power, but with it the device produced 180.3watts—an improvement of 100%. This improvement is based on a small generator with low back torque coefficient; for a large-scale design and stronger generator, the benefits are expected to be even greater.

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Filed under Component Development, Modeling

Assessing loading regimes and failure modes of marine power cables in marine energy applications


Abstract
The paper describes the parameters and results of a dynamic computational model that investigates the umbilical load conditions for a generic wave energy converter. Two geometric configurations of a double armoured power cable are considered, a catenary and a Lazy Wave shape. The model is set up using the dynamic analysis package OrcaFlex and uses top-end motions measured in 1:20 wave tank tests. While the simple catenary shape experiences high tensional forces at the attachment point and considerable compression, the maximum tensional forces can be significantly reduced and compression is avoided with a Lazy Wave shape.

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