Potential of Tidal Energy in Pakistan

Tidal power

Tidal energy, is a form of hydropower that converts the energy of tides into electricity or other useful forms of power. Although not yet widely used, tidal power has potential for future electricity generation. Tides are more predictable than wind energy and solar power. Among sources of renewable energy, tidal power has traditionally suffered from relatively high cost and limited availability of sites with sufficiently high tidal ranges or flow velocities, thus constricting its total availability

TURBINES USE IN TIDAL PPOWER GENRATION

TU

Rim Turbine (Copyright Boyle, 1996) Bulb Turbine (Copyright Boyle, 1996)

Ebb generating system with a bulb turbine

Tubular Turbine (Copyright Boyle, 1996)

OCEAN WAVE AND TIDE ENERGY POTENTIAL IN PAKISTAN

Two distinct types of ocean resource are commonly mentioned as possible energy sources: waves and tides. In both cases, the oscillating motion of an incoming and outgoing wave is used to drive turbines that generate electricity. It has been estimated that if less than 0.1% of the renewable energy available within the oceans could be converted into electricity, it would satisfy present world demand for energy more than five times over.

Wave Energy

Power generation using wave energy is at a much earlier stage of development, which offers more

predictable outputs than wind. Wave energy generation devices fall

into two general classifications, fixed and floating. Wave motion can be used to compress air to drive a turbine or hydraulic pumps.

In November 2000, the world's first commercial wave power station began to feed electricity into the UK's National Grid (www.dti.gov.uk). Situated on the Scottish island of Islay, the LIMPET (Land-Installed Marine-Powered Energy Transformer) has been installedto harness the action of waves to generate Figure 13: The worl electricity. Rated at 500kW, the system can provide enough electricity for about 400 homes (Fig. 13).

Pakistan has about 1000 km long coastline of with complex network of creeks in the Indus deltaic area (Fig.14). The erosional features along the Makran coastal areas show the relevance of strong wave energy, which could be harness for the generation of electric power for rapidly developing coastal cities, Gawader, Pasni, Ormara, Gadani etc (Fig. 15)

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Figure 14: Coastline of Pakistan

power station, on the Scottish island of Islay

Tide Energy

Tidal stream devices extract energy from the diurnal flow of tidal currents caused by the gravitational pull of the moon. That is why the tide goes in and out at the seaside. Large structures called "barrages" can be built to use the tides to generate electricity. Tidal energy schemes capture water at high tide and release it at low tide. Tide energy systems traps high tides in a reservoir. When the tide drops, the water behind the reservoir flows through a power turbine, generating electricity. Unlike wind and wave power, tidal streams offer entirely predictable output.

Typically, tidal turbines, similar in appearance to wind turbines, are mounted on the seabed. They are designed to exploit the higher energy density. Tidal stream differs from established technology for exploiting tidal energy [eg estuarine tidal barrages, such as and controlled by means of a large dam-like structure (www.dti.gov.ku). Rather, the tidal turbines operate in the free flow of the tides, meaning that large construction costs and disruption of estuarine ecosystems associated with barrages may be avoided. However, as tidal streams are a diffuse form of energy and the purpose of the barrage is to concentrate tidal flow, this also means that large numbersof turbines, spread over relatively large areas falling tides are used to produce power of seabed, are required if significant amountsof energy are to be extracted.

Figure 15: Gadani coastal area in foreground and Gadani beach area in the background.

The creek system of Indus delta extends over an area of 170 Km. Tidal water flows in these creeks with high velocity during flood and ebb tides, which is very favorable requirement for the extraction of energy from tidal currents.

The power resource potential of the Indus Deltaic Creek System is a great asset for future energy supply in Sindh, Pakistan. On the basis of limited surveys carried out by the National Institute of Oceanography (NIO), the Indus deltaic region where seawater inundates up to 80 km inland at some places due to the tidal fluctuation. These surveys and investigations show encouraging results. These creeks extend from Korangi Creek near Karachi to Kajhar Creek near the Pak India border. The current velocity in these creeks generally ranged from 4-5 knots but values as high as 8 knots were also recorded. The difference between tidal heights along the Pakistan coast varies between 2 to 5 meters. The tidal heights along the Sindh coast vary between 2-5 meters (Karachi) to over 5.0 meters (Sir Creek) in the Indus delta (Amjad, 2003, personal communication).

It is estimated that about 1100 KW power can be produced from these creeks altogether. Development of indigenous capabilities for harnessing tidal energy from Pakistan coast, could bring uplift of socio-economic conditions of coastal population of Pakistan and consequently would also promote minimize environmental pollution. However, detailed information is needed on the distribution function of waves at the selected site(s). In addition, the Sonmiani Hor and the Kalmat Khor are also good prospects for the development of Tidal Power in the Balochistan coastal belt (Fig.14).

Water Power in Pakistan

With the realities of climate change and the depletion of fossil fuels, renewable energy is now in the spotlight. Currently, wind and solar power have been in the news, but there are also many other sources of energy that would benefit the environment and the developing world. These sources include wave and tidal power in addition to small hydro. In China and India, small hydro is quite popular and there are also a few projects in Pakistan; however, the government could do much more to promote water power.

This article will first examine wave and tidal power with reference to its applicability in Pakistan. This will include an analysis of the history of these technologies, the conditions needed for successful projects and the benefits and drawbacks. The second part of the article will look at small hydro and why it is the best option for Pakistan at this time. Wave and tidal power are good technologies; however, the benefits of small hydro are much greater, especially for Pakistan’s developing economy.

An Explanation and History of Wave Power

Many companies have developed different ways of using wave power, but the two basic principles behind the designs remain the same. The first design involves the waves moving into a chamber where the water rises and falls. At the top of the chamber, there is a hole out of which air is forced, which drives a generator. The other type of design involves a long tube with hinges, which moves up and down due to the motion of waves. This motion moves hydraulic fluid, which drives a generator. A power cable then moves this electricity to where it is needed. The first design was used for the very first commercial wave power station, which is situated on Islay island in Scotland. This project began producing power in November 2000 and provides enough power for 400 homes, according to Nayyer Alam Zaigham, Professor & Director, Institute of Environmental Studies, University of Karachi

Tidal Power

Tidal power is potentially very useful because tides are very reliable. However, only 40 sites in the world have been found that are suitable because there must be a five meter difference between high and low tides.

There are two types of tidal power stations: the first is built across an estuary and looks similar to a dam. Inside the dam, there are tunnels that the water passes through. The water then turns a turbine. The other type of tidal power station looks like underwater wind turbines, but the size is usually limited to 25 to 50 megawatts (MW), according to the Pembina Institute which works to advance sustainable energy solutions in Canada. The largest tidal power station was built in northern France in 1966 and it produces 240 MW of electricity.

Benefits of Wave and Tidal

Power Wave and tidal power have many benefits. A 40 MW wave power station, which is being proposed off the coast of Cornwall, England, will save 300,000 tons of carbon dioxide over 25 years. In addition, the net potential for both wave and tidal power is greater than wind and solar because water is 850 times denser than wind, which pushes the turbines faster, according to the Ocean Energy Council (OEC).

Also, because many cities are situated in port areas, the power can be used right where it is needed. This is important because, as electricity moves through transmission systems, some of the power is lost and cannot be recovered. Both tidal and wave power are fairly inexpensive to maintain and tidal power is very predictable. Tidal power cannot harm any marine life because underwater animals can often sense turbine movement and their sound. In addition, because tidal power requires a high current, there will never be any animals feeding in those areas because plants cannot grow.

Challenges of Wave and Tidal

Power Wave and tidal power also have many challenges that need to be resolved in order for these types of powers to be successful.

Generally, the best waves are situated in temperate zones, which means that Pakistan is not suitable for wave power. This is because west winds are often found in the temperate zones, which are the best for wave power. Also, strong winds over large areas as well as a location near the continental shelf are much more favourable for wave power because it ensures a disparity between wave height and wave length.

Sites such as these are very rare, as mentioned above. Wave power is also much younger than wind or solar power and the cancellation of the UK wave power programme did not aid that. The fact that wave power is young also means that the power generated costs more than other sources of power. Currently, wave power costs approximately 7.5 cents per kilowatt hour (kWh) compared to 3 cents for natural gas, according to the OEC. Tidal power also faces many challenges. One of the main problems is that shore birds depend on the tide to uncover mud flats in order for them to feed; tidal power changes this quite drastically. The cost of tidal power per kWh is 12 cents, which is quite high. This cost would take many years to recover, which is not attractive for the developing world. Thus, although nuclear power is a more questionable energy source, capacity factor is very important because if the capacity factor is higher, it ensures that power will be produced more frequently. The reason why tidal power has such a low capacity factor is that tides are only predictable for part of the day and thus, there is no constant supply of energy.

Small vs. Large Hydro

Due to the challenges just mentioned, Pakistan is not suitable for wave and tidal power. However, Pakistan has had some experience with small hydro and there is a continuing interest in the technology. Currently, Pakistan has 108 MW of small hydro, which consists of nine projects. There are also 10 MW under construction and 180 MW planned, according to the International Energy Agency. However, Pakistan has the potential for 46,000 MW of hydroelectricity, which includes large and small installations; at present, only 6459 MW are installed, states engineer Abdul Waheed Bhutto. Furthermore, he states that many people now realize that large dams are not suitable for the environment, economy and people because dams cause the flooding of villages and towns, which means that the overnment must spend money to resettle people; the Kalabagh dam, for example, will cost the government Rs. 2 billion in resettlement costs.

How Small Hydro Works

Most small hydro systems work on the same principle known as run of river. One of the main benefits of this is the absence of areservoir, which means no towns are flooded. The water at the high point of the river is fed through a pipe, which turns a smallgenerator. After this, the water re-enters the river, which means that there are no environmental consequences and the system needed is fairly small.

These systems last for about 25 years and very little maintenance is needed. Small hydro has three different categories: pico, mini and micro, which are below 5 kilowatts (kW), 1 MW and 100 kW respectively, explain Taylor, Dr. Upadhyay and Laguna (Project Manager, European

Small Hydro Association) in a review on small hydro in developing countries published on Renewable Energy World.Vietnam is one of Asia’s leaders in pico hydro where a 300 watt unit costs $20 and produces enough power for one family.

Benefits of Small Hydro

Small hydro has many benefits, both for the environment and for Pakistani society. Small hydro produces no greenhouse gas emissions after it is built. In addition, unlike tidal power, the ecosystem is not adversely affected. Pico hydro only requires a 1-metre rop in height, which means the technology is guaranteed to work more of the time than wave power, which depends on very large waves.

With regards to society, mall hydro guarantees that there will be electricity available more of the time, which means that children can study at night and women can also make handicrafts ormarkets, which gives them more economic power in society. In addition, women are given even more free time because they do not have to collect firewood anymore.

Pakistan can also benefit from the experience and knowledge of its neighbour India, which has 1694 MW of small hydro installed. Lastly, it is very mportant to note that many people in rural Pakistan do not have electricity and small hydro is very well suited to many of these areas because it does not have to be connected to the grid. Another option is to build grids that only cover one village or town, which is a very popular option in China, India and Vietnam because smallhydro can easily be connected to this type of grid, state Taylor, Upadhyay and Laguna.

Thus, small hydro is by far the best option available for Pakistan due o the presence of many rivers, the environmental and societal benefits as well as the drawbacks of wave and tidal power. It is now up to the government to put in lace policies that would allow people to purchase these systems cheaply. If Pakistan is able to independently produce power, this would greatly increase the umber of jobs and the benefit to society.

HOW WE IMPLEMENT TIDAL ENERGY IN PAKISTAN

Tidal energy is a form of hydropower that exploits the movement of water caused by tidal currents

or the rise and fall in sea levels due to tides. Tidal energy is a relatively unexplored area in

Pakistan.

As a first step, we need a thorough survery of the coastal areas of Pakistan to identify the best

locations for setting up power plants for tidal power generation. We also need to encourage

research and development activities in this area to exploit tidal energy.From available data, the

known natural advantages that Pakistan has for tidal energydevelopment include a 170km creek

system of the Indus delta, 2-5 meter high tides at Korangi creek and over 5 meters at Sir Creek.

The infrastructure setup for tidal power plants is expensive and improvements are still needed in

the system for a cost effective solution to cater to Pakistan's requirements.