WAVE ENERGY ASSESSMENT IN INDONESIA SEAS BASED ON ERA-INTERIM REANALYSIS

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 6, June 2017, pp , Article ID: IJCIET_08_06_042 Available online at aeme.com/ijciet/issues.asp?jtype=ijciet&vtyp pe=8&itype=6 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed WAVE ENERGY ASSESSMENT IN INDONESIA SEAS BASED ON ERA-INTERIM REANALYSIS M. Zikra Ocean Engineering Department, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia H. Ikhwani Ocean Engineering Department, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia Institut Silvianita Ocean Engineering Department, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia ABSTRACT The objective of this paper is to perform a preliminary assessment of the available wave energy for green energy source around Indonesia seas. The computations have been conducted by using the wave data collected during 35 years period from 1980 to 2014 from European Centre for Medium-Range Weather Forecasts. The result indicated that location situated in the south of Java Sea has the most promising location for wave power potential, with the highest energy resource available in the month of January to December. The yearly mean wave power is maximum at the Java sea can reach 22 kw/m. The result indicated that the wave energy have the potentiality to contribute in the Indonesian energy demand. Keywords: wave height; wind speed; energy; Indonesia Seas. Cite this Article: M. Zikra, H. Ikhwani, N. Syahroni and Silvianita. Wave Energy Assessment in Indonesia Seas Based on Era-Interim Reanalysis. International Journal of Civil Engineering and Technology, 8(6), 2017, pp IET/issues.asp?JType=IJCIET&VType=8&ITy ype=6 1. INTRODUCTION N. Syahroni Marine Research Center, Teknologi Sepuluh Nopember, Indonesia Population growth has significant impact on the demand for energy resources. At present, most of energy supply is fossil-based resources which the consumption of fossil fuels caused to serious environmental problems especially CO2 emission. According to International editor@iaeme.com

2 M. Zikra, H. Ikhwani, N. Syahroni and Silvianita Energy Agency (IEA), nearly 68% of the worldwide electricity was generated from the fossil fuels, nuclear (13.4%), hydro (15.3%) and others (3.3%) (Analyses and Projection, 2011). Therefore, the renewable and cleaner sources of energy are essential to safe the future electricity supply for the developing countries such as Indonesia. Until the year of 2012, most of the electricity demand in Indonesia is still supplied from fossil-fueled power plants. Coal is still the highest rank at 51.08%. Natural gas is occupying in the second level with 22.60%. The rest of the energy is supplied oil by 15.02% and 11.31% by renewable energy including geothermal and water (Ministry of Energy and Mineral Resources, 2013). Currently, the supply and demand of electricity increased owing to the population growth. By 2030, the predicted power demand of Indonesia may be more than 168 GW (5 times of the demand in 2012 with 33 GW installed capacity) (Ministry of Energy and Mineral Resources, 2013). But, the use of fossil fuel for power generation release greenhouse gasses to cause the environmental effects. As a result, the search for clean energy source is essential to protect the environment and to address the energy crisis (Capps and Zender, 2009) (Capps and Zender, 2010). Indonesia is known as an archipelago country consisting largely of sea water. The potential of these waters is very large. Until now the potential of the sea water as a source of renewable energy are still not well developed and not fully utilized. When the water potential is used, it will be a renewable energy that can be a major alternative energy for Indonesia. With global attention now being drawn to climate change and the rising level of CO, the focus on generating electricity from renewable sources is once again an important area of research. Information regarding to wave power can obtained since already used by many countries. There are three kinds of energy in the sea, i.e. wave energy, tidal energy and ocean thermal energy. One of the energy in the ocean that can be utilized is the wave energy. Wave energy is environmentally friendly or pollution-free energy source and hence it is currently one of the sources most sought after by developed countries (Rashid and Hasanzade, 2011)(Wilson and Beyene, 2007). Also, wave energy is a renewable energy source that could have the potentiality to contribute in the Indonesian electricity market. The objective of this study is to analyze the variability of the wind and wave climate at Indonesia Sea as basis data source for possible wave energy evaluation projects in Indonesia. Knowledge of wave climate is required for engineering purpose. Especially, knowledge about wave information in a certain area is important for all activities related to the marine sector. For example offshore industry, ship design for safety and seakeeping, marine transportation management, renewable wave energy etc. Therefore, understanding the long-term variations in the wave parameter is key element for a preliminary evaluation of wave energy potential at different sites in order to suggest possible locations for wave energy converters. 2. DATA USED In Indonesia, long-term wave records based on in situ measurements are still limited. Due to that reason, in this study, temporal variation in wind speed and significant wave height are studied using hind casting model from ERA-Interim reanalysis data for 35 years period from ERA-Interim is the latest global atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) (Dee et.al, 2011). The ERA-Interim reanalysis data provides wind speed and significant wave height (SWH) data with 1 x 1 degree resolution. For this study, 10 observation locations were chosen on the nearest of Indonesia sea. Those observation points are shown in the Figure 1 and names of each location is presented in Table editor@iaeme.com

3 Wave Energy Assessment in Indonesia Seas Based on Era-Interim Reanalysis Figure 1 Indonesia map Table 1 Observation points Point Coordinate Location A N and E Malacca Strait B N and E Natuna sea, Riau Island C N and E Pacific Ocean D S and E Indian Ocean, Mentawai Island E S and E Sunda Strait F S and E Java Sea G S and E Flores Sea H S and E Banda Sea I S and 2.25 E South of Java Sea, Indian Ocean 3. METHODOLOGY Conventionally, wave power is rated in terms of energy flux in deep water for unit of wave crest and expressed in kw/m. For a general sea state, the total energy density Et per unit area is the sum of kinetic and potential energy and it is given by: E i = ρ g 2 H 8 (1) where ρ is the sea water density (equal to 1025 Kg/m3), g is the gravity acceleration and H is the wave height. The energy flux P across a vertical section of unit width in the direction perpendicular to wave propagation is equal to: P = E C i g in which Cg is the wave group celerity equal to g/2ω in deep water, where ω is the wave frequency. For real sea state, wave height and period of Eq. (1) and (2) can be expressed as the following: H = 4 m m0 0 m1 Te = m0 (4) in which mn represent the spectral moment of order n. Hence, after substituting Hm0 and Te into Eq. (1) and (2), the wave power density for a real sea state can be expressed as (Geogre and Roger, 2003): (2) (3) editor@iaeme.com

4 M. Zikra, H. Ikhwani, N. Syahroni and Silvianita 2 2 ( ρ m0 e ) / ( 64π ) P = g H T or 2 0 P = 0.42 x Hm x Te where P is the wave power density, Hm0 is the significant wave height, Te is the peak wave period. 3. RESULTS AND DISCUSSION In Indonesia, wave condition is influenced by the east monsoon and the west monsoon wind seasons [9]. Monsoon period that occurred in Indonesia is divided into four periods; there are the period of the Asian Monsoon (December-January-February), Transition Monsoon Australia (March- April-May), Monsoon Australia (June- July-August) and Transition Monsoon Asia (September- October-November). The condition of wave climate for Indonesia seas is shown in Fig. 2. Figure 2 showed the averaged of significant wave height (SWH) from January until Desember. In general, the averaged of wind speed over the sea surface around Indonesia Sea is between 0.3 to 6 m/s. From Table 2, it is shown that highest averaged wind speed is in the south of Java (in the point I). Averaged wind speed at this location can reach above 6 m/s during west monsoon season or monsoon Australia. The maximum wind speed of 12 m/s is likely to occur in the January and February period in this location. The smallest averaged of wind speed is observed during October to December or in the transition monsoon Asia period as shown in Table 2 for all locations. The averaged of wind speeds at those months are between 0.3 to 2.35 m/s. For wave characteristics, in all year, the averaged of SWH over the Indonesian sea is between 0.3 to 2.4 m. The highest averaged of SWH is 2.4 m in the South of Java as shown in Table 2. In the Asian monsoon period (December to February), the averaged of SWH is between 0.5 to 2.4 m in height with corresponding period around 4.0 to 8.5 s. The highest averaged of SWH during this period is 2.4 m. In the month March, April and May, the heights of SWH are around 0.3 to 2.0 m in height with corresponding period around 4.0 to 9.0 s. In the Australian monsoon (June, July and August), the averaged of SWH is between 0.4 to 2.2 m in height with corresponding period around 3.9 to 9.1 s. The highest averaged of SWH during this period is 2.21 m. In the month September, October and November, the heights of SWH are around 0.3 to 2.3 m in height with corresponding period around 4.1 to 9.2 s. Table 3 shows the averaged of wave power calculated from averaged SWH for each month from year 1980 to The available wave power changes with month and season. The averaged of wave power over the Indonesian sea is between 0.2 to 22.0 kw/m. In the south of Java, the available of wave power is higher when compared to other regions in Indonesia Sea, which have a potential 15 to 22 kw/m. The averaged of wave power in the south of Java is available throughout the year (January to December). The highest averaged of wave power in this location is kw/m as shown in Table 3. Additionally, Indian Ocean have increasing trend of monthly mean significant wave height during all year as shown in Figure 3. The trends of monthly mean significant wave height are statically significant from January to December as presented in Zikra et. al. (2016) (2015). (5) editor@iaeme.com

5 Wave Energy Assessment in Indonesia Seas Based on Era-Interim Reanalysis Figure 2 Results of monthly variations of mean significant wave height (SWH) editor@iaeme.com

6 M. Zikra, H. Ikhwani, N. Syahroni and Silvianita Month Figure 3 Variations of monthly mean significant wave height (SWH) in Indian Ocean near south of Java (Point I) Table 2 Monthly averaged significant wave height in Indonesian Sea Month H avg T Havg T Havg T Havg T Havg T Havg T Havg T Havg T Havg T 1 1,27 5,01 0,86 4,98 0,82 4,99 1,26 8,06 0,67 7,52 1,32 4,49 0,44 4,19 1,24 4,96 2,40 8,52 2 1,25 4,84 0,65 4,67 0,67 4,67 1,24 8,03 0,68 7,60 1,29 4,33 0,44 4,25 1,21 4,91 2,24 8,48 3 1,22 4,67 0,51 4,49 0,62 4,49 1,21 8,54 0,53 7,82 1,18 4,26 0,40 4,27 1,17 4,82 1,91 8,95 4 1,21 4,53 0,40 4,23 0,35 4,23 1,20 8,62 0,51 8,06 1,03 4,32 0,45 4,44 1,19 4,86 1,96 9,04 5 1,35 4,46 0,39 4,00 0,34 4,00 1,34 8,76 0,72 8,24 0,86 4,47 0,57 4,74 1,38 5,11 2,03 9,00 6 1,57 4,54 0,45 3,96 0,41 3,97 1,57 8,88 0,92 8,37 0,80 4,57 0,65 4,81 1,53 5,18 2,14 9,11 7 1,62 4,60 0,51 4,05 0,48 4,06 1,62 8,81 0,97 8,31 0,82 4,58 0,64 4,72 1,64 5,08 2,17 9,13 8 1,69 4,70 0,54 4,18 0,51 4,19 1,68 8,66 0,89 8,24 0,84 4,49 0,60 4,60 1,70 4,91 2,21 9,19 9 1,61 4,63 0,47 4,15 0,45 4,16 1,61 8,56 0,69 8,08 0,80 4,33 0,46 4,42 1,61 4,79 2,17 9, ,44 4,98 0,54 4,64 0,51 4,65 1,44 8,43 0,51 7,81 0,94 4,32 0,38 4,27 1,41 4,88 2,28 8, ,29 5,13 0,58 5,00 0,56 5,00 1,29 8,24 0,39 7,58 1,06 4,42 0,33 4,24 1,20 5,01 2,32 8, ,24 5,25 0,84 5,19 0,81 5,20 1,23 8,10 0,51 7,57 1,28 4,57 0,39 4,22 1,18 5,06 2,35 8,58 Table 3 Monthly wind speed in Indonesian Sea Uavg Umax Havg Umax Uavg Umax Uavg Umax Uavg Umax Uavg Umax Uavg Umax Uavg Umax Uavg Umax 1 3,34 10,84 3,72 11,09 3,47 9,76 2,97 11,99 3,69 11,37 4,07 12,47 3,66 10,90 3,89 11,28 4,33 12,37 2 2,97 10,05 3,24 10,13 3,58 9,83 3,16 11,51 3,53 11,22 3,72 11,22 3,56 10,84 4,02 11,65 4,37 12,26 3 2,42 9,29 2,49 9,27 3,42 9,60 2,73 10,35 3,00 10,15 3,70 9,98 3,32 9,66 3,28 10,40 3,48 10,63 4 1,87 7,65 1,98 7,09 3,05 9,21 2,49 9,18 2,86 10,12 4,15 9,70 3,52 9,36 2,99 9,75 3,86 9,69 5 2,06 7,63 2,27 7,62 3,14 9,24 2,81 9,34 3,50 10,48 4,73 10,01 4,16 10,00 3,99 10,52 5,05 10,59 6 2,49 8,72 2,78 8,92 3,43 10,12 3,42 10,17 3,94 10,95 5,04 10,19 4,67 10,22 5,05 11,57 5,36 10,89 7 2,71 8,77 3,11 8,90 3,96 10,52 3,58 11,01 4,41 11,27 5,03 10,34 4,65 10,31 5,57 11,29 5,87 10,99 8 2,77 9,40 3,23 9,49 4,18 10,55 4,21 11,10 4,93 11,42 4,71 10,39 4,50 9,83 5,46 10,94 6,13 10,83 9 2,39 8,62 2,77 8,70 3,61 9,20 4,03 10,92 4,76 11,08 4,03 10,43 3,80 9,23 4,44 10,05 5,44 10, ,44 4,98 0,54 4,64 0,51 4,65 1,44 8,43 0,51 7,81 0,94 4,32 0,38 4,27 1,41 4,88 2,28 8, ,29 5,13 0,58 5,00 0,56 5,00 1,29 8,24 0,39 7,58 1,06 4,42 0,33 4,24 1,20 5,01 2,32 8, ,24 5,25 0,84 5,19 0,81 5,20 1,23 8,10 0,51 7,57 1,28 4,57 0,39 4,22 1,18 5,06 2,35 8, editor@iaeme.com

7 Wave Energy Assessment in Indonesia Seas Based on Era-Interim Reanalysis Table 4 Monthly mean wave power in kw/m Month (Jan) 3,72 1,69 1,55 5,90 1,55 3,63 0,38 3,51 22,61 2 (Feb) 3,46 0,90 0,96 5,69 1,63 3,30 0,38 3,33 19,70 3 (Mar) 3,20 0,54 0,80 5,76 1,02 2,72 0,32 3,05 15,06 4 (Apr) 3,04 0,30 0,24 5,72 0,95 2,12 0,41 3,15 16,00 5 (May) 3,74 0,27 0,21 7,25 1,99 1,54 0,71 4,51 17,16 6 (Jun) 5,17 0,38 0,31 10,09 3,24 1,36 0,93 5,60 19,16 7 (Jul) 5,59 0,49 0,43 10,66 3,59 1,42 0,89 6,26 19,79 8 (Aug) 6,16 0,56 0,51 11,27 3,04 1,47 0,76 6,52 20,72 9 (Sep) 5,54 0,43 0,38 10,23 1,75 1,29 0,44 5,73 20,14 10 (Oct) 4,77 0,63 0,55 8,06 0,94 1,74 0,28 4,48 21,41 11 (Nov) 3,95 0,78 0,72 6,32 0,53 2,30 0,22 3,30 21,46 12 (Dec) 3,69 1,69 1,57 5,65 0,91 3,43 0,30 3,23 21,78 4. CONCLUSION In this paper, the present work constitutes a preliminary step in estimating the wave energy potential around Indonesia Sea. The available wave power around Indonesia Sea has been calculated from hindcasting model obtained from ECMWF data from 1980 to It can be concluded that the available annual wave power in Java Sea is around 22.0 kw/m. Indian Ocean near south of Java Sea is the potential places to develop wave energy project in Indonesia. The result indicated that the wave energy resource available from January to December. ACKNOWLEDGEMENTS This research was funded by Lembaga Penelitian dan Pengabdian kepada Masyarakat, Institut Teknologi Sepuluh Nopember (ITS) dan Kementerian Riset, Teknologi dan Pendidikan Tinggi (under contract number 694/PKS/ITS/2017). REFERENCES [1] Analyses and Projections, "U.S. Energy Information Administration", information on http :// [2] Ministry of Energy and Mineral Resources "Draft General Plan of Electricity (RUPKN) 2012/2013". [3] S. B. Capps and C. S. Zender, Global ocean wind power sensitivity to surface layer stability, Geophysical Research Letters, vol. 36, no. 9, Article ID L09801 [4] S. B. Capps and C. S. Zender, Estimated global ocean wind power potential from QuikSCAT observations, accounting for turbine characteristics and siting, Journal of Geophysical Research Atmospheres, vol. 115, no. 9. [5] A. Rashid and S. Hasanzadeh, Status and potentials of offshore wave energy resources in Chahbahar area (NW Omman Sea), Renewable and Sustainable Energy Reviews, vol. 15, no. 9, pp [6] J. H. Wilson and A. Beyene, California wave energy resource evaluation, Journal of Coastal Research, vol. 23, no. 3, pp [7] Dee, D. P., Uppala, S. M., Simmons, A. J., Berrisford, P., Poli, P., Kobayashi, S., Andrae, U., Balmaseda, M. A., Balsamo, G., Bauer, P., Bechtold, P., Beljaars, A. C. M., van de Berg, L., Bidlot, J., Bormann, N., Delsol, C., Dragani, R., Fuentes, M., Geer, A. J., Haimberger, L., Healy, S. B., Hersbach, H., Hólm, E. V., Isaksen, L., Kållberg, P., Köhler, M., Matricardi, M., McNally, A. P., Monge-Sanz, B. M., Morcrette, J.-J., Park, B.-K., Peubey, C., de Rosnay, P., Tavolato, C., Thépaut, J.-N. and Vitart, F., " The ERA editor@iaeme.com

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