Importance of drivetrain optimisation to maximise electrical power from wave energy converters

When analytically optimising the control strategy in wave energy converters which use a point absorber, the efficiency aspect is generally neglected. The results presented in this paper provide an analytical expression for the mean harvested electrical power in non-ideal efficiency situations. These have been derived under the assumptions of monochromatic incoming waves and linear system behaviour. This allows to establish the power factor of a system with non-ideal efficiency. The locus of the optimal reactive control parameters is then studied and an alternative method of representation is developed to model the optimal control parameters. Ultimately we present a simple method of choosing optimal control parameters for any combination of efficiency and wave frequency.

Download Full-text

Electrical Power Generation from the Oceanic Wave for Sustainable Advancement in Renewable Energy Technologies

Sustainability ◽

10.3390/su12062178 ◽

2020 ◽

Vol 12 (6) ◽

pp. 2178 ◽

Cited By ~ 7

Author(s):

Omar Farrok ◽

Koushik Ahmed ◽

Abdirazak Dahir Tahlil ◽

Mohamud Mohamed Farah ◽

Mahbubur Rahman Kiran ◽

...

Keyword(s):

Power Generation ◽

Renewable Energy ◽

Electrical Power Generation ◽

Wave Energy ◽

Electrical Power ◽

Extensive Literature ◽

Energy Devices ◽

Wave Energy Converters ◽

Oceanic Wave ◽

Energy Converters

Recently, electrical power generation from oceanic waves is becoming very popular, as it is prospective, predictable, and highly available compared to other conventional renewable energy resources. In this paper, various types of nearshore, onshore, and offshore wave energy devices, including their construction and working principle, are explained explicitly. They include point absorber, overtopping devices, oscillating water column, attenuators, oscillating wave surge converters, submerged pressure differential, rotating mass, and bulge wave converter devices. The encounters and obstacles of electrical power generation from the oceanic wave are discussed in detail. The electrical power generation methods of the generators involved in wave energy devices are depicted. In addition, the vital control technologies in wave energy converters and devices are described for different cases. At present, piezoelectric materials are also being implemented in the design of wave energy converters as they convert mechanical motion directly into electrical power. For this reason, various models of piezoelectric material-based wave energy devices are illustrated. The statistical reports and extensive literature survey presented in this review show that there is huge potential for oceanic wave energy. Therefore, it is a highly prospective branch of renewable energy, which would play a significant role in the near future.

Download Full-text

Grid Impact of a Wave Farm on its Local Network: Analysis of Voltage and Flicker Levels

Volume 7: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2012-83616 ◽

2012 ◽

Author(s):

Anne Blavette ◽

Dara L. O’Sullivan ◽

Ray Alcorn ◽

Anthony W. Lewis ◽

Michael G. Egan

Keyword(s):

Time Series ◽

Wave Energy ◽

Large Scale ◽

Negative Impact ◽

Electrical Power ◽

Local Network ◽

Wave Energy Converters ◽

Wave Farm ◽

The Impact ◽

Energy Converters

Most oscillating wave energy converters without significant amounts of energy storage capacity generate significant electrical power fluctuations in the range of seconds. Because of these fluctuations, a wave farm may have a negative impact on the power quality of the local grid to which it is connected. Hence, the impact of these devices on both distribution and transmission networks needs to be well understood, before large scale wave farms can be allowed to connect to the grid. This paper details a case study on the impact of a wave farm on the distribution grid around the national wave test site of Ireland. The electrical power output of the oscillating water column (OWC) wave energy converters was derived from experimental time series produced in the context of the FP7 project “CORES”. The results presented in this paper consider voltage fluctuation levels and flicker levels for a typical time series. Simulations were performed using DIgSILENT simulation tool “PowerFactory”.

Download Full-text

A Study on Electrical Power for Multiple Linear Wave Energy Converter Considering the Interaction Effect

Energies ◽

10.3390/en11112964 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2964 ◽

Cited By ~ 1

Author(s):

Qiao Li ◽

Motohiko Murai ◽

Syu Kuwada

Keyword(s):

Wave Energy ◽

Interference Effect ◽

Electrical Power ◽

Wave Energy Converter ◽

Energy Converter ◽

Multiple Wave ◽

Floating Structures ◽

Wave Energy Converters ◽

Electrical Generator ◽

Energy Converters

A linear electrical generator can be used on wave energy converter for converting the kinetic energy of a floating structure to the electricity. A wave farm consists of multiple wave energy converters which equipped in a sea area. In the present paper, a numerical model is proposed considering not only the interference effect in the multiple floating structures, but also the controlling force of each linear electrical generator. In particular, the copper losses in the electrical generator is taken into account, when the electrical power is computed. In a case study, the heaving motions and electrical powers of the multiple wave energy converters are estimated in the straight arrangement and triangle arrangement. In addition, the average electrical power is analyzed in different distances of the floating structures. The aim of this paper is to clear the relationship between the interference effect and electric powers from wave energy converters. This will be useful for deciding the arrangement of multiple wave energy converters.

Download Full-text

Spectral Control of Wave Energy Converters with Non-Ideal Power Take-off Systems

Journal of Marine Science and Engineering ◽

10.3390/jmse8110851 ◽

2020 ◽

Vol 8 (11) ◽

pp. 851

Author(s):

Alexis Mérigaud ◽

Paolino Tona

Keyword(s):

Wave Energy ◽

Electrical Power ◽

Efficiency Factor ◽

Scale Model ◽

Control Force ◽

Efficiency Function ◽

Control Approach ◽

Wave Energy Converters ◽

Spectral Control ◽

Energy Converters

Spectral control is an accurate and computationally efficient approach to power-maximising control of wave energy converters (WECs). This work investigates spectral control calculations with explicit derivative computation, applied to WECs with non-ideal power take-off (PTO) systems characterised by an efficiency factor smaller than unity. To ensure the computational efficiency of the spectral control approach, it is proposed in this work to approximate the discontinuous efficiency function by means of a smooth function. A non-ideal efficiency function implies that the cost function is non-quadratic, which requires a slight generalisation of the derivative-based spectral control approach, initially introduced for quadratic cost functions. This generalisation is derived here in some detail given its practical interest. Two application case studies are considered: the Wavestar scale model, employed for the WEC control competition (WECCCOMP), and the 3rd reference model (RM3) two-body heaving point absorber. In both cases, with the approximate efficiency function, the spectral approach calculates WEC trajectory and control force solutions, for which the mean electrical power is shown to lie within a few percent of the true optimal electrical power. Regarding the effect of a non-ideal PTO efficiency upon achievable power production, and concerning heaving point-absorbers, the results obtained are significantly less pessimistic than those of previous studies: the power achieved lies within 80–95% of that obtained by simply applying the efficiency factor to the optimal power with ideal PTO.

Download Full-text