Ocean Wave Energy in Indonesia: Potential, Technology, and Economic

Introduction

Indonesia’s electricity sector has many problems to solve in years to come. Started from chasing electricity demand in 2050 which has been predicted up to 2562 TWh in 2050 (900% increasing from today), until pursuing the renewable energy ratio of 27% at 2050 [Indonesia Energy Outlook, 2019, BaU Prediction]. Indonesia’s government has been trying to pursue the target by making a program called 35000 MW of power plant in 2028 and 23% of renewable energy ratio in 2025. However, the program is seemingly difficult to achieve since report from National Energy Council concludes that electricity production just increases 3%, while the demand increases 5% (in 2018), and the renewable energy ratio just reached 12,4% in 2018. Thus, the government, researchers, and stakeholders need to take action, starting with an acceleration program on pursuing the closest targets and thinking about how Indonesia could achieve long-term targets in 2050.

One of many solutions to achieve long-term targets is exploring potential energy from natural wealth, such as ocean wave energy. Indonesia has huge ocean wave energy potential since the open shoreline on south Indonesia reaches 4000 kilometres, approximately. Ocean wave energy (OWE) is predicted to be the promising ocean energy due to its high energy and power density, high utilization factor, and predictable resource [B. Triasdian, et al, 2019]. As a comparison, Ocean wave energy has a power density 4 times higher than wind energy [S. Doyle, et al, 2019]. Moreover, Ocean wave energy is estimated to release 6gCO2 /KWh, much lower than the other non-renewable power plant which released 250 gCO2 /KWh [S. Astariz, et al, 2015]. To find out more about ocean wave energy, especially in Indonesia, this article will discuss the general principle of wave energy, wave energy potential on shoreline and nearshore Indonesia, wave energy converter device and its application in other countries, and finally, this article will investigate the economic of oscillating water column device as the most advance and most simple converter device.

General Principle of Wave Energy

Ocean wave energy is basically natural energy transfer from the wind to waves which happens when the wind blows above the seawater. The power transported is called wave energy flux, which follows on the equation below [A. Des Andres, et al, 2017]:

𝑃𝑤 = 𝜌𝑔/(64phi) * Hmo² * Te

Where Pw is wave energy flux (KW/m), Hmo is significant wave height (meter), Te is wave period (second), 𝜌 is fluid mass density (1,025 kg/m3), 𝑔 is gravity acceleration (9,81 m/s2).

From the equation, a place with a high significant wave height and wave period are better. Based on the previous research, 2-meters of significant wave height and 10-seconds of wave period is classified into medium wave energy flux. Based on sea classification, intermediate and shallow water is recommended site because of economic consideration and breaking wave theory, which conclude that the wave height is bigger when approaching the shore [B. Triasdian, et al, 2018].

Wave Energy Potential in Indonesia

Based on world wave energy generalization approach from Cornett (2008), the wave energy flux in south Indonesia is around 10–20 kW/m. Even the wave energy flux in south Indonesia is lower than other countries with greater wind and waves, the installation of wave energy converter in Indonesia is supposed to be easier and more economic because of lower maintenance and failure issues.

The 21-years study report from National Oceanic and Atmospheric Administration (NOAA-America) gives a numerical model using WAVEWATCH-III to know significant wave height and wave period insouth Indonesia, which concludes that south Indonesia is mainly 2-meters of average significant wave height and 12-seconds of average wave period.

Rizal, et al (2019) investigates a few potential wave energy areas in Java, Bali, and Nusa Tenggara using observation data on intermediate sea in that area and numerical model using WAVEWATCH-III. Those study concluded that Cilacap, Yogjakarta, Jember, and Bali have wave energy potential above 40 kW/m. Other regions such as Cianjur, Trenggalek, Lombok, dan Sumba have medium wave energy potential around 20–30 kW/m.

Overall wave energy potential in Indonesia could reach 1.49 TW with the consideration of 10 kW/m as minimum wave energy flux that existed in 40% of Indonesia coastal line [B. Triasdian, et al, 2018]. For another example, if 10% of south java coast is installed with wave energy converter, the wave energy might produce 5.9 GW of electricity which is 10% of Indonesia electricity production.

Wave Energy Converter

Wave energy converter is a device with a purpose to create electricity by using wave propagation. The principle of the devices may be different from each other, but the similarity is that almost all the devices using wave, or something resulted from wave, to drive the turbine. This article will discuss the wave energy converter recommended for shoreline and nearshore area [De Andres, et al, 2017).

(1) Oscillating Water Column (OWC) is utilizing energy from water oscillation within the chamber caused by incoming waves. Most OWCs are open below the sea surface where the air is trapped within the chamber which opened to the atmosphere through the duct with a turbine inside. The advantage of this technology is its simple principle and application, very low impact on marine environment, and the turbine is above the water. The average efficiency of this technology is 29%.

(2) Overtopping Device generates the electricity by using water elevation into the device reservoir. The water will be going up, then the water passes back to the sea via low head hydro turbine. The turbine of overtopping device always exposes with the water. The average efficiency of this technology is 17%.

(3) Heaving Device is using horizontal movement of waves. The principle of heaving device is seemingly simpler than Oscillating Water Column, but this technology is ineffective in harder wave condition. The average efficiency of this technology is 16%

Many Countries have started to use ocean wave energy, especially Australia, Portugal, and Italy. Astariz, et al (2015) made a result database of wave energy converter along the world, from small model scale up to large model scale. That wave energy device is not just for research, but also has been used for small community on coastal area. Other countries have very high interest on wave energy by accommodating research fund, increasing the electricity tariffs from wave energy, and giving subsidy to the costumers.

Economic Analysis of Wave Energy in Indonesia

Wave energy converter is mainly under modelling and prototype scale. The researchers still need to find the convergency of the converter with the environment parameter including significant wave height, wavelength, sea contour, and others. Thus, the cost of applying this technology is still very high, especially in Indonesia. For now, Indonesia has to start the development of wave energy converter and apply the technology on a prototype scale to increase the confidence of investors, so the cost will be lower in the future. The way to minimize the cost burden is by applying the device on a region that has potential wave energy and high electricity cost. That way will reduce the burden of research funding because the installation and operation will be paid by the customers, so the government just needs to subsidy or give the amount of money to make the business still profitable for the investors.

Athallah, et al (2020) has studied the Levelized cost of energy in Southwest Sumba, Indonesia with oscillating water column device. Southwest Sumba is selected to be analysed because of its 24 kW/m wave energy flux and Rp2.964/kWh electricity price. The study integrates the technology efficiency and economic calculation to calculate the Levelized cost of energy (LCOE). The study concluded that 10–20–30-meters characteristics dimensions resulting Rp4.204, Rp2.719, Rp2.153 per kWh electricity. However, if the lowest price also calculates the investment rate, the price will almost reach Rp4.500/kWh. The role of government to support the development of wave energy converter is about subsidy the price differential between Levelized cost of energy and cost after investment rate. In the future, if the researchers have found the convergency of the wave energy device, the cost will be much lower because the development cost will not be needed anymore resulting 50% reduction of capital cost.

As conclusion, electricity demand and renewable energy have to be solved. One of the solutions is developing potential energy from natural wealth. Hopefully, in 2050, the Indonesia energy target can be achieved, so Indonesia’s energy would not be deficit and still getting better environment.

Writted by: Adiv Gayu Athallah, Department of Ocean Engineering — Institut Teknologi Sepuluh Nopember

References

B. Triasdian, Y.S. Indartono, N.S. Ningsih, et al., “Device Selection of the Potential Wave Energy Site in Indonesian Seas”, IOP Conference Series: Earth and Environmental Science, vol. 291, no. 1, 2019.

S. Astariz, G. Iglesias, “The economics of wave energy: A review”, Renewable and Sustainable Energy Reviews, vol. 45, pp. 397–408, 2015.

B. Triasdian, Y.S. Indartono, N.S. Ningsih, “Energy capture potential of existing wave energy converters for Indonesian sea”, AIP Conference Proceedings, vol. 1984, 2018.

A. De Andres, E. Medina-Lopez, D. Crooks, et al., “On the reversed LCOE calculation: Design constraints for wave energy commercialization”, International Journal of Marine Energy, vol. 18, pp. 88–108, 2017.

A. Babarit, “A database of capture width ratio of wave energy converters”, Renewable Energy, vol. 80, pp. 610–628, 2015.

A.M. Rizal, N.S. Ningsih, et al. “Preliminary Study of Wave Energy Resource assessment and its Seasonal Variation Along the Southern Coasts of Java, Bali, and Nusa Tenggara”, 2019.

A. G. Athallah, M.A Albasyir. “Economy Analysis of Wave Power Plant in Southwest Sumba — Indonesia with Oscillating Water Column Wave Energy Converter”, 2020.

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