Review Of Ocean Energy Technologies In Malaysia Perspective
A developing country like Malaysia is heavily dependent on fossil fuel for electricity generation. With the increasing of urbanization and speedy industrialization, the demand of electricity is expected to accelerate. The reducing of the fuel each day, along with it side effects which bring negativity towards the environment, the government has been utilizing the bio-fuel and solar radiation for a change. However, the exploitation ocean energy, which is environmental friendly and fastest growing renewable energy source that can be obtained easily in Malaysia, had yet been taken into account for electricity generation. Malaysia had a total of 4,675 kilometers coastline along the coast and the islands across the country which indicate a good sign that Malaysia had a great potential for wave energy. Therefore, studies were carried out in purpose of identifying the usage of ocean energy technologies for a long usage of electricity in future in Malaysia.
Introduction
A developing country such as Malaysia does not just depend on a sustainable development of energy resource, but also it hygienist, safety along with the ability of renewable energy itself. In total, the electrical energy demand from all renewable resources in Malaysia was 20,087 MW and the total capacity installed was 25,258 MW in 2010 and the number is expected to double up by 2020. Hence, causing the extensively growth of greenhouse gas emission from 43 million tons in 2005 to 110 million in 2010 that can lead to a suffering number of adverse effects due to climate change. The growth rate of electricity demand in Malaysia per annum is now at 3. 2%. Malaysia mostly depends on the use of renewable energy from fossil fuels, coal and natural gas for electricity generation. However, the usage of fossil fuels and burning coal had led to air pollution, polluted soil, water shortage, widespread human illness and ecosystem degradation. As a result, Malaysia will face a higher range of social and economic issues. Fast action had been taken out by the government by exploiting the energy of solar radiation bio-fuel for electricity generation. But Malaysia is surrounded by tremendous of water and possibly the 29th longest coastline in the world. Not using the renewable energy that is easily obtained throughout the country is such a loss for Malaysia since it has a massive potential of ocean energy that may be a vital source of electrical energy generation.
There are broadly three categories of ocean energy (a) Tidal Energy (b) Wave Energy and (c) Thermal Energy. According to a report, the wave power density should be more than 50 kW/m so that the wave energy conversion technologies can generate enough power and also to justify the commercial viability [6]. However, exploiting the wave power in Malaysia may be very little as the Malaysian’s ocean generally less than 50 kW/m. Next, for thermal energy, generating thermal energy by using ocean thermal energy conversion (OTEC) to generate sufficient power energy and justifying it commercial viability however turning into a disappointing result. The temperature gradient is usually less than 20℃ if the depth of the ocean is less than 1000m and it turn out that the depth of Malaysian’s ocean is less than 1000m. Therefore, it is far from the value of its commercial viability which it should be greater than 20℃.
Hence, OTEC is out of the question. As for tidal, it has highly predictable cycle that can lead to be a potential renewable energy. In order to exploit the usage of tidal energy, two approaches are used: (a) Tidal Stream approach and (b) Barrage approach. Malaysia had at least 4 sites that are potentially have high tidal stream energy: (a) Pangkor Island, (b) Sandakan, (c) Malacca and also (d) Kelang. Among this four sites using the tidal stream approach, Sandakan has the most power availability, 80% of the time and lowest at 79%. The lowest occurred only during January and February. During March, August, September, October and December, the highest power availability it can get is at 81%. The assessment were taken from a database known as OSU TOPEX/POSEIDON Crossover database (TPXO). However, the data could not been a reliable much since the measurement collected from 20 tidal stations installed across the country were much difference from each other. As for barrage approach, a physical barrier is created within the sea with Sluice Gates to control the seawater. Sluice Gates is placed at the highest tide to hold the water level inside the barrage and the difference in water level between the barrage and the water sea is created. The difference of the water level can drive the turbines and generate electricity. However, the construction of the barrage is much expensive and not economically viable compared to installing the tidal stream turbines. This paper aims to assess the critical potential of tidal energy in Malaysia for decision making. A brief introduction in generating tidal energy data along with the its characteristic in Malaysia and amount of potential electricity energy will finally be discussed in this paper that can bring and economical and environmental benefits of using marine current turbines.
Data collection
Tidal phenomenon around Malaysia is studied by observing the sets of data on the tidal height and also the tidal velocity. Three sources were used to gather the data: (a) Tidal observation records of 2005, (b) TPXO software output and (c) Princeton Ocean Model (POM) with adjoint Data Assimilation Method.
Tidal observation records of 2005 are published by the Department of Survey and mapping, Malaysia. This organization observed and measured the tidal elevation information from 20 tidal stations along the East and West of Malaysia coast. All these 20 stations are provided with float type tide gauges, completed with an IC-Memory cassette digital recording system. The function of the system is to record the data every 10 s, with the average value written in every 50s to the IC-Memory cassette and performed by the built-in microprocessor.
However, by using this method, it is restricted to collect the tidal information from 20 sites in Malaysia and is not suitable to be used to serve the aim of this paper. Therefore, the TPXO software were used to simulate the tidal information from the sites that have no station. The data recorded from the Tidal observation record is used to verify the result from the TPXO software and POM model.
TPXO Software
OSU TOPEX/POSEIDON Crossover database (TPXO) is a global tides properties. The tidal data is provides by using a global model that has a resolution of 1/4 degrees spacing and has a magnitude and latitude of 1440 by 721 grid points across the model.
The TPXO database served the purpose of investigating the potential of exploiting the tidal energy around Malaysia coast. Several sites were observed to be having a high potential of tidal velocities. Further observation have shown that the TPXO data is not accurate when compared to the Tidal observation records and therefore the POM is used to model the oceanography and study about the tidal phenomena around Malaysia coast.
Princeton ocean model (POM)
Princeton Ocean Model is an ocean model and had been developing at the Princeton University to stimulate or in other mean, to be model a high-resolution coastal ocean phenomenon. Apart from having various advanced numerical schemes, POM also can be used to simulate a flooding area of land with its inundation features; and coupling ocean currents with surfaces waves.
An adjoint data assimilation techniques was included into the POM software to calibrate the oceanography of Malaysia against the measurement values from the Tidal record. Values of the tidal elevations of the 20 sites in Malaysia are integrated over 1 year in order to verify the outputs of the TPXO Software output and Princeton Ocean Model (POM). The RMS value is obtained and compared with the Tidal observation records of 2005 as tabulated in Table 1. It can be seen that the POM has a slightly 9% less consistently errors at 20 sites which mean that the POM are more accurate and thus, lead to the used of POM to investigate the potential of ocean energy around Malaysia coast.
Type of tides in Malaysia
Tides are very long period waves that move through the oceans in response to the forces exerted by the moon and the sun. Thus, creating a periodical rise and fall of sea level at a location of the earth with highly predictable cycles.
The observable rise and fall of the sea level effect strongly by the shoreline topography, ocean currents and the distribution of the continents on earth. As a result, different tidal cycles can be observed in a different regions of the Malaysia coastline. They are describes as semi-diurnal, diurnal or mixed tidal cycles. The average time of the semi-diurnal tide to occur is about 12 hours and 24 minutes while the average time for the diurnal is about 24 hours and 48 minutes. The tides are usually combined together, between semi-diurnal and diurnal and formed another type of waves which is a mixed tide. Mixed tides are sometime dominating inside the semi-diurnal tides and sometime dominating inside the diurnal. The highest tidal current occurs at spring tides and the lowest at the neap tides when the semi-diurnal tides is in dominant. But when the diurnal tides is in dominant, the highest tidal currents can occur at an extreme declination of the moon and the lowest currents to zero declination. It can be concluded that the types of tides shows the availability of the minimum and maximum of the tidal energy. Thus, it is important in identifying the type of tides that are available in Malaysia coastline.
The values of the ratio, F as given in Equation (1) is the classification of the tides. K1 and O1 are the two main diurnal tides components while the M2 and S2 are the two main semi-diurnal components. If the value of F is less than 0. 25 and 1. 5, it means that it is a mixed tides with a dominant of diurnal and if it is greater than 3. 0, it is a diurnal tides.
All of these components for the ocean are generated by the POM ocean model. The F value is then calculated and the type of tides throughout Malaysia coast can finally be concluded that along the east coastline at Peninsular Malaysia, mixed tide with dominant semi-diurnal occurred here except at Terengganu which the mixed tide is dominant in diurnal while along the west coastline, semi-diurnal and mixed tides with dominant semi-diurnal occurred here. For the tides in East Malaysia, it is a mixed tide either dominant semi-diurnal or diurnal. No diurnal tides are available in Malaysia. The power supply characteristics from the MCTs at that location can be observed by knowing what type of tides are at the particular sites. If MCT is established at Terengganu coastline, two rises in the power output of MCT is likely to happen within a day. The highest output of power will happened during the extreme declination of the moon. However, if the MCT is to be established at another sites in Peninsular Malaysia, four rises should be anticipated to happen within a day as the power output will be the highest during the spring tides.
Energy exploitation by Marine Current Turbines (MCT)
The following Equation (2) can be used to calculate the energy density of tidal current where E is equal to yearly energy density (kWh/m2), ρ equal to density of the seawater (1024 kg/m3) and V equal to the component of the tidal velocity perpendicular to the cross section of tidal turbine (m/s). The tidal data produced by the POM ocean model is used together with the Equation (2) in order to study the energy density profile. Such places as Kapar, Pontian and Semporna have a great potential of tidal wave extraction. But even with such shoreline topographies, exactly how much amount of tidal energy can actually be exploited pretty much depends on the tidal technologies advancement.
Numerous of innovative MCT are developed over the past couple of years and is tested on several sites. The hydrofoil is attached to an oscillating arm that drives the hydraulic system. The hydrofoil is oscillated due to the current flow on the side of the hydrofoil. This process then will lead the system to generate the electricity.
Unique in features and the conversion mechanism are taken into account as the tidal technologies is created. The design are depends on the nature of the tidal current, the topography and the environmental constraints at the site of the exploitation energy. The developing site of the MCTs depend on two things which are the depth of the ocean and total number of turbines. Depth is essentially the important thing because it will ensured the blades of each MCT in an array position. This action is taken not just because of harnessing the high energy flow but also to avoid a large force that can damage the turbines. The minimum point swept by the blades for the MCTs is 0. 25*h where the h is equal to the depth. Great energy is available although the upper part of the water column is unstable. Wave can distort the upper flow and can cause significant loading. Therefore, the blades should not be infringed up to 7 m of the depth.
To sum up everything, the MCT can only be installed on a site that has the depth that are greater than 20 m which in this case, only Pulau Jambongan, Kota Belud and Sibu are the perfect location to install the MCT.
In order to determine the total number of MCTs that can be installed a certain site, three things are needed to be taken into account which are (a) longitudinal spacing, (b) latitudinal spacing and (c) area under high tidal speed.
Economic and environmental benefits
Amount of fossil fuels that can be replaced by MCT
In Malaysia, the main electricity were supplies by the big three utilities which are Tenaga Nasional Berhad (TNB) which mostly in Peninsular Malaysia, Sabah Electricity Supply Berhad (SESB) and also Sarawak Energy Berhad. Total energy produced over the year of 2003 is nearing 83,300 G Wh. Open-cycle gas turbines are always the final resolution to be used in order to meet the peak demand from the consumer. This shows that an open-cycle gas turbines that usually that performed even during the peak hours can now be possibly replaced by the the marine current turbines that are available on the network. Thus, it can reduced the used of the fossil fuel as a result of the penetration of MCTs that could be a natural gas.
The data collected can be used by the government and utility companies as they can figured out the way on how to solve the problem of how to save the natural gas. About RM 1. 1 billion worth of natural gas per year can be saved if the power output of 8604 G Wh per year and which in this case the average cost of the natural gas is estimated to be RM13. 15/mmBtu or by other mean RM0. 62/kg.
Greenhouse gases effect that can be avoided by the MCT
As reported before, the natural gas is the most likely to be replaced by any distributed generation. The emission factor for CO2 is observed to be 0. 53 kg/k Wh for a gas-fired power plant and so the amount of CO2 that can be avoided is about 4,552,512. 70 tons per year. Somehow, the data is not very useful to the government and the utility companies but it can be registered into their green projects such as Clean Development Mechanism (CDM) project.
Net present value (NPV)
NPV is a standard way to evaluate the finance advantages of a certain long-term projects. As the value of the NPV increase, the financial benefits will be increasing too. The calculation of the NPV is as in Equation(3). [image: image10. png](3)S is equal to the capital cost of the project, I is for the income of the project, E for the yearly maintenance and operation expenses, g equal to inflation rate, i for the nominal interest rate and N is for the lifespan of the project.
Various electrical components costing are also include in the cost associated such as power conversion system, structural element, subsea cable installation, turbine generator and oneshore electric grid interconnection. All of these components are imported directly from the US. The costing for all of these which is estimated to be USD 1683 per kW which equal to RM5722. 20 per kW and the total cost of these are taken into account for the capital cost of the MCTs.
Estimated maintenance and operation cost per year is nearly RM300 per kW. The cost of the shipping for the electrical components is not included.
