Wave energy potential along the southern coast of the Caspian Sea

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Highlights

  • The southern coast of the Caspian Sea is studied in order to find a suitable location for installing wave energy conversion systems.

  • 17 sites in Caspian Sea with proper dispersion are selected within Iran's territorial waters for investigation of wave extraction capabilities.

  • Various parameters including wave height, wave period, and wave energy are compared for the mentioned sites.

  • The comparisons lead to two selected sites for wave energy extraction.

  • Wave roses and combined scatter and energy diagrams are extracted for the selected sites.

Abstract

We have investigated wave energy potential near the coast of northern Iran. Our main goal, in this study, was to find a suitable location for installing wave energy conversion systems along the southern coast of the Caspian Sea, within Iran's territorial waters, based on the data obtained from ECMWF (European Centre for Medium-Range Weather Forecasts) between 1999 and 2013. We plotted annual and seasonal diagrams of wave height, period, and energy at 17 different locations. We observed that, despite some minor fluctuations, wave energy generally reaches its peak value in autumn. Based on the analyzed data, we suggest that cities of Noshahr and Babolsar are suitable locations for installation of wave energy conversion systems. We further studied wave roses nearby the aforementioned cities. We found that strongest waves occur in South-southeast (SSE) direction with the maximum magnitude of 8.37 and 9.67 Mwh (per unit length of the wave front) at Babolsar and Noshahr, respectively. Finally based on our study, we suggest an optimal range of significant wave height and period for designing an efficient wave energy converter in these areas.

Introduction

In recent years, alternative energy sources have become more attractive as they are becoming more economical. The growing need for energy, limited fossil resources, environmental pollution risks, arising from fossil fuels, and its impact on the life, such as climate change and the greenhouse effect is dragging a lot of attention to natural renewable energies. Examples of renewable energies include solar, ocean, wind and biofuel energies. Sea wave energy is one of the cleanest renewable energies and there are many ongoing researches aimed to find more efficient ways to capture this energy in human usable forms. The Total amount of the sea wave energy in the world is estimated in the order of 1–10 TW, which is equivalent to a large fraction of the world's current total energy consumption [1]. Typically, the amount of extractable energy per square meters exists in the sea and ocean waves, is 15–20 times that of wind or solar energy [2]. For this reason, many efforts have been made so far to extract this type of energy. Wave energy is subject to severe seasonal variations [3] therefore it is necessary to study wave characteristics of a region to find a suitable location and optimized WEC to avoid unnecessary expenses and reducing electricity cost of this type of renewable energy In this regard, different shores around the world have been analyzed by researchers.

Iglesias and Carballo in 2009, using data and information obtained from SIMAR-441 and two wave buoys, analyzed surface waves along the Death Coast of Spain [4]. They concluded that waves in shallower areas have less energy than in areas with more depth. Based on their study, waves have larger average amplitude in winter and dominant waves are in the North West direction. Folley and Whittaker in 2009, studied amount of energy carried by waves at various depths of the North Atlantic Ocean in the coast of Scotland [5]. They also stated that amount of energy deep ocean waves contain is significantly larger than the energy waves contain in shallower areas. However considering wave direction, they noted that the near shore wave energy can be harvested more efficiently and on some coasts it is even more economical to install WECs near the shore. Saket and Etemad-Shahidi in 2012, using 23 years data obtained from numerical modeling, studied the waves on the northern coast of the Gulf of Oman [6]. They suggested the port of Chabahar as the best area to install WECs in their article. They concluded that most energy can be harvested in July and August. Akpinar and Kömürcü in 2012, studied sea wave in deep waters near the south-east coast of the Black Sea [7]. They estimated wave energy by the means of wave height and wave period, obtained from a numerical model. They mentioned that the potential energy of the sea wave, in that area, is highest in winter and is approximately equal to 1.8 kW/m. Mota and Pinto in 2014 investigated the waves of the coast of Portugal with 15 years wave-wind numerical simulation and compared the amount of energy that can be extracted in three different sites in the near and offshore areas [8]. They introduced the suitable points for mounting WECs and also claimed that about 200 MWh of annual energy is available in these areas. Lavidas and Venugopal in 2017 used numerical modeling to examine the wave resource and potential wave power at Libyan coast [9]. They mentioned that although, waves in this area are not as energetic as open ocean waves, but lower variation improves predictability and lower rate of extreme events leads to lower installation and maintenance costs.

Wave energy has been studied in many different locations around the globe. However the Caspian Sea, despite its suitable characteristics which makes it an ideal location to extract sea wave energy, has not been subject of any comprehensive study, to the authors’ best knowledge. In this study, the wave energy potential near big cities in northern Iran has been investigated widely. The reason is hidden in the touristic attractions of these cities because of their coastal situations. Accessing electricity in offshore can further develop the tourism industries in these regions. Thus, in this article we investigated the sea wave energy in the southern Caspian Sea. The rest of this article is organized as follows. In section two we explain characteristics of the Caspian Sea. In section three we describe the 17 locations chosen for analysis, in order to identify a suitable location for WEC installation. In section four we summarize the results of our study on the selected locations and determine the optimal locations for extracting wave energy. Finally, in section five, we explain our conclusions based on the study done on the southern coast of the Caspian Sea.

Section snippets

The Caspian Sea

The Caspian Sea is the largest lake on the Earth, a closed basin in the northern hemisphere of the Earth. It is situated where the South-Eastern Europe meets the Asia continent, between latitudes 47.13′N and 36.34′N and longitudes 46.43′E and 54.51′E [10]. The Caspian Sea is bounded on the south by Iran, on the east and north-east by Turkmenistan and Kazakhstan, on the north-west and west by Russia, and on the west by Azerbaijan. Its coastline length is about 7000 km long which about 1000 km of

Wave data

Buoy data is often discrete and entire months may be unavailable at many sites [13]. Thus this study is based on modeling data. The data used in this study, includes wave period, significant wave height and wave energy from 1999 to 2013 in the southern part of the Caspian Sea in the maritime border of Iran which is obtained from the European Center for Medium-range Weather Forecasts (ECMWF) model at six-hour intervals. The ECMWF is assimilation meteorological data project for predicting the

Results and discussions

As noted in Section 3, in order to select the suitable place for the installation of WECs, comparing wave characteristics in selected areas is of great importance. In addition to this parameter, easy access to WECs and considering economic costs will be considered as well. All results that will be shown in this section are based on the 15 years average data. We first investigated the variations of wave period in these locations. Averaged wave period at these locations are shown in Fig. 3.

Table 2

Conclusions

In this study, we investigated wave energy along the southern coast of the Caspian Sea, neighboring Iran. The purpose of this study was to find a suitable location for installation of a WEC in the Caspian Sea and maritime border of Iran. We performed wave analysis of the Caspian Sea for 15 years, from 1999 to 2013. Using this data, we plotted annual and seasonal diagrams of wave height, wave period, and wave energy for 17 locations. Our studies have shown that South East of the Caspian Sea is

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