Growing world population and socio-economic development are at the root of an ever-increasing energy demand throughout the world. Total world energy use rises from 308 Quadrillion Btu in 1985 to 472 Quadrillion Btu in 2007, and then rises to 506.2–510.5 Quadrillion Btu in 2010. Much of this demand is met by means of fossil fuels, leading to greenhouse gas emissions and climate change so, the efforts are taken to increase the share of renewable energy sources in the global energy mix where, Marine energy is a reliable, high-density source of energy with limited environmental impacts.
Wave and tidal energy is a visible expression of power of nature where ambition to convert the natural source of energy bound up in marine systems to something useable by mankind goes back to 1940’s. In the 21st century strong efforts are made to dig out the clean source of energy with an objective to reduce greenhouse gas emissions to counter environment degradation and climate change. All renewable energy exploration can not only provide a sustainable energy supply for economic growth, but also reduce greenhouse gas emissions. Tides, a non-polluting, renewable, and clean energy, are characterized by oscillating currents in the ocean caused by the rise and fall of the ocean surface due to the gravitational attraction among the Earth, Moon, and Sun. it is estimated that tidal energy reserves all over the world are 2.7 billion kW. If all of these reserves are converted into electrical energy, the electricity generating capacity per year will be about 1,200 billion kWh. Generating electricity from tidal energy is developing and reliable. The largest operating tidal barrage power plant is the La Rance power facility (built in 1967) in France, with the generating capacity of 240 MW and the annual electricity generating capacity of 600 million kWh. The Jangxia Creek power facility in China has a generating capacity of 3,900 kW achieving remarkable economic and social benefits.
Pakistan, with its long coastline, growing population, increasing energy demands and extreme air pollution, has a great potential for the development of marine energy. However, this potential has not received sufficient legislative or entrepreneurial attention so far. Despite of enormous potential of its energy resources, Pakistan remains energy- deficient and rely heavily on imports to satisfy its needs. Moreover, a very large part of the rural areas does not have the electrification facilities, because they are either too remote and/or too expensive to connect to the national grid. Pakistan obtains its energy requirements from a variety of traditional and commercial sources where there is no prospect for Pakistan to reach self-sufficiency in hydrocarbons, a good option is the exploitation and utilization of the huge coal-reserves of Thar and the other renewable energy sources.
Pakistan has wide spectrum of high potential renewable energy sources, conventional as well as non-conventional, which have not been adequately explored, exploited and developed. Thus, the primary energy supplies today are not enough to meet even the present demand. So, Pakistan, like other developing countries of the region, is facing a serious challenge of energy deficit. Pakistan is a blessed nation with abundant resources but scarce energy to utilize these resources so, we must work hard to find the alternate solutions where our blue sea have the capacity to support the nation not only through tidal energy but also through wave energy.
Potential of Oceanic Energy (Wave & Tidal) 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. 3 3 Potential of Oceanic Energy (Wave & Tidal).
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 installed to harness the action of waves to generate electricity. Rated at 500kW, the system can provide enough electricity for about 400 homes. Pakistan has about 1000 km long coastline, with complex network of creeks in the Indus deltaic area. The erosional features along the Makran coastal areas show the relevance of strong wave-energy, which could be harnessed for the generation of electric power for rapidly developing coastal cities, Gwadar, Pasni, Ormara, Gadani etc.
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 [e.g. estuarine tidal barrages, such as the 240 MW barrage operating in France (Figure-16) in that tidal flows are not captured 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 numbers of turbines, spread over relatively large areas of seabed, are required if significant amounts of energy are to be extracted. 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 a 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, 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 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.
Hence, Blue energy is the most promising source of energy which is not only environment friendly but also a good source for all the nations blessed with the sea as:-
- Blue energy, like wind and solar, is renewable and will never run out.
- It is also a constant energy, that is to say, usable 24 hours a day, we can always obtain it regardless of weather conditions. For example, to obtain solar or wind energy, we depend on whether it is windy or the day is sunny, for blue energy we must not take into account the weather.
- With this type of energy, the entire planet could be supplied, since it occurs throughout the world, the only thing that is needed is for the river water to come into contact with the sea water.
- CO2 emissions are a real problem for climate change. The plants to obtain this type of energy do not have CO2 emissions. Their ecological impact is very low thanks to how they are designed.
Blue Energy is a promising renewable energy source for the future. Over 80% of the current global electricity demand can be met through Blue-Energy. This translates into reduction of approximately 40% of global energy-related greenhouse gas emissions; however, significant efforts are still required to make salinity gradient energy competitive as compared to other renewable energy sources. Further it is important to evaluate the effect of such a system on the ecology, shipping traffic and recreational activities in the neighborhood.