Monthly Archives: March 2013

Consistent ocean wave energy harvesting using electroactive polymer (dielectric elastomer) artificial muscle generators


S. Chiba, M. Waki, T. Wada, Y. Hirakawa, K. Masuda, and T. Ikoma – Applied Energy, April, 2013

Abstract

An energy transduction technology that operates efficiently over a range of frequencies is important for practical energy harvesting devices such as ocean wave power generators. Dielectric elastomer is based on the change in capacitive energy of a deformable dielectric and is a candidate for such applications. A simple scale model of EPAM-based wave energy harvesting system was tested in a wave tank over a range of wave periods from 0.7 to 3 s and wave heights from 2 cm to 6 cm. The energy output was found to be largely independent of wave period.

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Filed under Component Development, Experiments, Materials and coatings

Experimental investigation in a Wells turbine under bi-directional flow


M. Paderi and P. Puddu – Renewable Energy, September, 2013

Abstract

In this work an experimental study of flow through a Wells turbine with NACA0015 profiles submitted to an unsteady and bi-directional flow is presented.

The experimental set-up of the Department of Mechanical, Chemical and Materials Engineering of the University of Cagliari (DIMCM), can simulate the real operation of a wave energy conversion device based on the principle of an oscillating water column (OWC) equipped with a Wells turbine. The set-up consists of a piston, controlled by a hydraulic system, that moves inside a cylindrical chamber open at the top where the Wells turbine is placed. The piston movement generates the airflow driving the turbine.

Experimental investigations were carried out in proximity of the rotor blade using three-dimensional aerodynamic probes to perform a careful characterization of the flow field upstream and downstream of the turbine. The dynamic characteristic of the turbine in terms of dimensionless flow parameters was also determined. The real entity of the hysteresis phenomenon was highlighted for the phases of acceleration and deceleration of the unsteady flow through the turbine. Moreover, the existence of an appropriate correlation between the conventional dimensionless coefficients and a measurable and reliable physical variable was investigated.

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Filed under Component Development, Experiments, Testing Infrastructure

Hydro-Kinetic Energy Conversion: Resource and Technology


M. Grabbe – PhD Dissertation, Uppsala University, April, 2013

Abstract

The kinetic energy present in tidal currents and other water courses has long been appreciated as a vast resource of renewable energy. The work presented in this doctoral thesis is devoted to both the characteristics of the hydro-kinetic resource and the technology for energy conversion. An assessment of the tidal energy resource in Norwegian waters has been carried out based on available data in pilot books. More than 100 sites have been identified as interesting with a total estimated theoretical resource—i.e. the kinetic energy in the undisturbed flow—in the range of 17 TWh. A second study was performed to analyse the velocity distributions presented by tidal currents, regulated rivers and unregulated rivers. The focus is on the possible degree of utilization (or capacity factor), the fraction of converted energy and the ratio of maximum to rated velocity, all of which are believed to be important characteristics of the resource affecting the economic viability of a hydro-kinetic energy converter.

The concept for hydro-kinetic energy conversion studied in this thesis comprises a vertical axis turbine coupled to a directly driven permanent magnet generator. One such cable wound laboratory generator has been constructed and an experimental setup for deployment in the river Dalälven has been finalized as part of this thesis work. It has been shown, through simulations and experiments, that the generator design at hand can meet the system requirements in the expected range of operation. Experience from winding the prototype generators suggests that improvements of the stator slot geometry can be implemented and, according to simulations, decrease the stator weight by 11% and decrease the load angle by 17%. The decrease in load angle opens the possibility to reduce the amount of permanent magnetic material in the design.

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Filed under Resource Characterization, System Development

Network Security Assessments for Integrating Large-Scale Tidal Current and Ocean Wave Resources Into Future Electrical Grids


J. Khan, D. Leon, A. Moshref, S. Arabi, and G. Bhuyan – Proceedings of the IEEE, April, 2013
Abstract
Marine energy, especially tidal current and ocean wave resources, bear immense potential for generating renewable power toward meeting global electricity needs. A number of conversion technologies have been successfully demonstrated worldwide and precommercial/commercial deployments are expected to appear in the near future. While electric power utilities foresee renewable technologies as a viable alternative to fossil fuels, marine energy technologies are generally excluded in their energy planning processes. Lack of technological preparedness and unavailability of device information are two major obstacles in that regard. This article provides an insight on how such novel schemes of power generation can be analyzed under conventional network planning exercises using generic information. Continue reading

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Filed under Grid, Modeling

The current status of wind and tidal in-stream electric energy resources


H.H.H. Aly and M.E. El-Hawary – American Journal of Electrical Power and Energy Systems, March, 2013

Abstract

Renewable energy is an effective and clean source of supplying electrical loads especially in remote and rural areas. In this paper we discuss offshore wind and tidal in-stream energy as they rely on similar technologies for generating electricity at offshore sites. In particular, we survey the impacts of offshore wind and tidal current integration into the grid, various types of generators and their dynamic modeling, fault ride-through techniques used to improve generator and grid integration performance, the aggregated wind turbines modeling and finally put the light on the stability and control problems.

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Evaluation of Various Technologies for Wave Energy Conversion in the Portuguese Nearshore


D. Silva, E. Rusu and C.G. Soares – Energies, March, 2013

Abstract

The objective of the present work is to perform an evaluation of the performance provided by various technologies for wave energy conversion in the Portuguese continental coastal environment. The wave climate in the target area is first analyzed using the results from three years of simulations with a wave prediction system based on numerical models. Based on the above data, diagrams for the bivariate distributions of the sea states occurrences, defined by the significant wave height and the energy period, are designed for both winters and whole years. On this basis, the output of five different technologies for the conversion of wave energy is assessed in some relevant locations from the Portuguese nearshore. According to the results obtained, the Portuguese continental coastal environment appears to be appropriate for the wave energy extraction. At the same time, the present work shows that the output of the wave energy conversion devices does not depend only on the average wave energy but is also dependent on the distribution of the wave energy among the sea states of different periods. For this reason, a good agreement between the characteristics of the power matrices of the wave energy converters operating in a certain place and the diagrams for the bivariate distributions of the sea states occurrences corresponding to the considered location represents a key issue in selecting the most appropriate technology for wave energy conversion.

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Filed under Field Measurements, Resource Characterization

Ocean’s Renewable Power and Review of Technologies: Case Study Waves


E. Enferad and D. Nazarpour – New Developments in Renewable Energy

This is a chapter in a book describing characteristics of wave resources, global resource availability, and different concepts for converting wave motion into electricity.

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Examining the feasibility of converting New York State’s all-purpose energy infrastructure to one using wind, water, and sunlight


M.Z. Jacobson, R.W. Howarth, M.A. Delucchi, S.R. Scobie, J.M. Barth, M.J. Dvorak, M. Klevze, H. Katkhuda, B. Miranda, N.A. Chowdhury, R. Jones, L. Plano, and A.R. Ingraffea – Energy Policy, March, 2013

Abstract

This study analyzes a plan to convert New York State’s (NYS’s) all-purpose (for electricity, transportation, heating/cooling, and industry) energy infrastructure to one derived entirely from wind, water, and sunlight (WWS) generating electricity and electrolytic hydrogen. Under the plan, NYS’s 2030 all-purpose end-use power would be provided by 10% onshore wind (4020 5-MW turbines), 40% offshore wind (12,700 5-MW turbines), 10% concentrated solar (387 100-MW plants), 10% solar-PV plants (828 50-MW plants), 6% residential rooftop PV (∼5 million 5-kW systems), 12% commercial/government rooftop PV (∼500,000 100-kW systems), 5% geothermal (36 100-MW plants), 0.5% wave (1910 0.75-MW devices), 1% tidal (2600 1-MW turbines), and 5.5% hydroelectric (6.6 1300-MW plants, of which 89% exist). The conversion would reduce NYS’s end-use power demand ∼37% and stabilize energy prices since fuel costs would be zero. It would create more jobs than lost because nearly all NYS energy would now be produced in-state. NYS air pollution mortality and its costs would decline by ∼4000 (1200–7600) deaths/yr, and $33 (10–76) billion/yr (3% of 2010 NYS GDP), respectively, alone repaying the 271 GW installed power needed within ∼17 years, before accounting for electricity sales. NYS’s own emission decreases would reduce 2050 U.S. climate costs by ∼$3.2 billion/yr.

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Black Sea wave energy atlas from 13 years hindcasted wave data


B. Aydoğan, B. Ayat, and Y. Yüksel – Renewable Energy, September, 2013

Abstract

The present study aims to evaluate the wave energy potential of the Black Sea. Wave properties were calculated using 3rd generation Spectral Wave Model for years 1996–2009 by using wind data from European Center for Medium-Range Weather Forecasts (ECMWF). The wave model was calibrated using the wave measurements conducted at five different stations. Wave power atlas displaying time – averaged wave power for entire Black Sea was generated. Also wave power roses and wave power distribution tables in means of periods and heights for different regions were presented. Wave energy found to be decreasing along the coast from west to east. It was found that the most energetic region is the South Western part of the sea. The eastern part of the Black Sea is the least energetic in means of wave power. It was concluded that the most promising location is the Thracian shores of Turkey, especially west side of Istanbul. Beside this, other promising locations in the Black Sea Basin were also evaluated. Annual wave energies (kWh/m) for different regions were presented in this study.

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Filed under Resource Assessment, Resource Characterization

Effects of mooring systems on the performance of a wave activated body energy converter


B. Zanuttigh, E. Angelelli, J.P. Kofoed – Renewable Energy, September, 2013

Abstract

Aim of this paper is to analyse the power and hydraulic performance of a floating Wave Energy Converter with the purpose at optimising its design for installation in arrays. The paper presents new experiments carried out in 1:30 scale on a single device of the Wave Activated Body type in the deep-water wave tank at Aalborg University. Power production and wave transmission were examined by changing the mooring system, the wave attack and the device orientation with respect to the incoming waves. To assure the best performance the device size may be “tuned” based on the local peak wave length and the mooring system should be selected to allow the device for large movements.

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