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Abstract
As the current necessity for renewable energy continues to increase due to global awareness, ocean renewable energy presents itself as a viable means of alternative energy production. Despite its potential for supplying terawatts of power to the global community various ocean renewable energy technologies are not without their drawbacks. This supposedly clean method of producing electricity does have a distinct environmental impact depending on the type of energy producing technology utilized and as such needs to be fully understood before being utilized as an alternative energy sources on a mass scale.
Introduction
Renewable energy technologies are methods of energy production that utilize naturally replenishable resources such as solar, wind, geothermal heat and tides. Unlike fossil fuel based methods of energy production renewable energy technologies are nonpolluting and are a source of potentially limitless energy since they are not dependent on a finite source of power. Unfortunately, the adaptation of such technologies for widespread use and as a method of primary energy production are limited and are not commercially prevalent in even the most economically advanced states. There are three reasons behind this: renewable energy resources from a commercial energy standpoint are as of yet an unproven method of reliable energy production, the means by which renewable energy is produced requires a high initial startup cost and finally in terms of overall reliability only geothermal plants or hydroelectric power sources such as ocean renewable energy are the only proven reliable sources of renewable energy both of which are limited to select areas and cannot be implemented in all cases due to geographic limitations. Nicholas Carr in his article, IT doesnt matter , which examines the use of technologies and their implications on society states that technologies and their widespread use only become cheaper once they reach their build out completion. The term build out completion refers to a point in technological development wherein a type of technology has already reached commercial viability and can be effectively replicated and mass produced. Carr explains that so long as certain forms of technology have not reached a point of build out completion they will most likely never be adopted due to their prohibitive costs and the uncertainty attached to the technology itself. This is reflected in the fact that when examining the case of economically well off countries such as Australia (90% of its energy production is reliant on fossil fuels) they still prefer to use fossil fuel energy resources as a means of energy production due to that fact that this form of technology has already reached its build out completion and is thus economically viable. Various types of renewable energy technologies, which as of yet have to even reach the half way point indicated by Carr, are unlikely to be adopted on a global scale until such a time that they reach a state of build out completion.
Ocean Renewable Energy Resources
As mentioned earlier, one of the currently commercially viable methods of renewable energy production besides that of geothermal energy is the use of ocean renewable energy technology [5]. This form of renewable energy production uses a variety of different methods such as temperature differences in the water, kinetic energy produced by waves, tidal forces and wind generated by offshore prevailing winds. In fact various scientists have stated that in terms of sheer energy potential the ocean possesses the capacity to sufficiently power human civilization if its renewable energy resources are properly extracted. It must be noted that similar to other forms of renewable energy production ocean renewable energy is similarly non-carbon emission producing and in effect helps to reduce the carbon emissions in countries that utilize such systems as a means of secondary energy production.
Problems with Using Renewable Energy Resources
The reason why the term secondary energy production is utilized is due to the fact that while such methods of energy production are viable and dont produce carbon emissions the level of energy produced does not currently match the needs of a growing population base. Commercially speaking when comparing fossil fuel burning power plants to either solar powered arrays or ocean renewable energy technologies most energy producers would choose to construct a fossil fuel burning plant rather than a renewable energy production site. The reasoning behind this is simple, fossil fuel power plants simply require less space and produce more power compared to solar or wind generated energy sources. In order to prove this point the example of Egypt and its attempt at utilizing renewable energy resources should prove to be an adequate example. In its attempt to expand into the renewable energy industry in order to supply an energy starved populace with more electricity Egypt introduced both solar and wind energy into its electricity producing infrastructure. The result was the wind turbine installations in the Red Sea produced only 230 MW while the solar energy array only produced 30 MW. When taking into consideration the fact that Egypt requires 36GW within the next 10 years in order to keep up with demand this indicates that renewable energy technologies at the present currently do not have the needed capacity to keep up with an ever increasing demand for electricity.
The Need for Renewable Energy
With energy consumption expected to increase within the coming decades this would require countries to supplement their current energy infrastructure. The inherent problem with this is that the fuel source of the most widely used type of power plant is oil and coal which are finite resources. As energy demands grow so too will the demand for such resources, the inherent problem with this is that the price of finite resources continues to increase over time as demand grows. There will eventually come a time where the world will have to deal with the dwindling supply of fossil fuels and the aftereffects they cause on the environment. Based on this it can be expected that a shift will start wherein global governments will start to pour resources into renewable energy technologies in order to supplement their energy infrastructure. What this means for the global economy is the start of a trend leaning towards recycling and environmental stewardship creating new product markets that specialize solely in environmentally sustainable goods and practices.
Utilizing Ocean Renewable Energy
Currently there are 4 main types of ocean renewable energy namely: Ocean Thermal Energy Conversion (OTEC), Wave Energy, Tidal Energy and Offshore Wind energy [5]. Ocean Thermal Energy Conversion is a form of renewable energy technology that utilizes the differences in temperature between cold deep water and warm shallow water in order to run a heat engine that uses the divergent temperatures to create electricity. Wave energy technologies on the other hand uses the kinetic energy produced by waves through the use of turbines and transforms the kinetic energy into mechanical energy which through the use of a converter becomes electrical energy. Tidal energy technologies utilizes a similar method of energy production to wave energy however utilizes tidal forces in order to turn turbines instead of waves. The last form of ocean renewable energy is offshore wind energy, this particular method of energy production utilizes the kinetic energy of prevailing winds often found on coastlines in order to produce electricity.
Environmental Impact and Effect
While the use of ocean renewable energy does not release extensive amounts of carbon emissions into the atmosphere it cannot be said that this form of renewable energy production does not impact the environment in any way [3]. Since the technologies utilized in producing ocean renewable energy are artificial, their placement into a natural environment would of course bring with it distinct environmental impacts inherent to that particular form of technology [3]. For example the conversion of temperature differences in OTEC energy production actually results in the release of heat into various environments that are normally free from high temperatures. Not only that OTEC methods of energy production actually have the potential to cause the release of various toxic chemicals which further disrupts the natural environment of numerous underwater species [5]. Wave energy turbines have been known to impact various species that live near the surface of the ocean due to the sudden impacts on the water surface. While offshore wind farms on the other hand have been known to create significant amounts of noise and vibration within ocean environments which have been shown to impact various ocean species that are sensitive to vibration and sound [3]. It is based on the facts presented that this paper will examine the environmental effect of various forms of ocean renewable energy and investigate the degree of their effects on the surrounding environment.
Ocean Thermal Energy Conversion (OTEC)
Background
OTEC or Ocean thermal energy conversion is a method of energy production that utilizes the natural temperature differences in ocean layers [5]. The process utilizes heat stored in warm surface water in order to create steam that drives a turbine to produce electricity. At the same time cold water from deeper ocean layers is pumped to the surface to enable the steam to recondense. It must be noted though that this particular method of ocean renewable energy production is not without its limits. Due to the need for significant changes in temperature between ocean layers in order to properly and efficiently operate the system an OTEC energy platform cannot be utilized in areas where the surface water temperature is lower than the 20 to 25 degrees Celsius [5]. While it is possible to operate a plant at lower temperatures the energy expended needed to evaporate the necessary fluids into steam to turn the turbines would be greater and would thus create an inefficient system. Various studies examining the idea placement of OTEC energy platforms indicate that areas with high ambient surface water temperatures such as those present in the tropics (the Philippines, Maldives, Bora- Bora etc.) or Middle Eastern Countries (U.A.E and Saudi Arabia) should prove to be ideal areas where such systems would operate at peak capacity. The largest known operational OTEC system was created in 1999 within the U.S. and produced an estimated 250 KW of electricity during a standard operational period. It must be noted that with current energy expenditures continuously increasing with gigawatts of power needed in the coming years this indicates that OTEC energy technologies are currently insufficient in their ability to properly generate electricity to meet demand. While various supporters of the technology indicate that it is currently an emerging technology and far from its build out completion state the fact remains that the cost of generating electricity using a standard OTEC system today ranged from 8 to 24 cents per kilowatt hour which is still significantly higher than costs related to energy production utilizing traditional fossil fuel technologies. Though this technology is reported as clean and non-polluting this description is only utilized in the sense that it doesnt pollute the environment in the same way that a fossil fuel burning plant does. While the OTEC system doesnt produce significant amounts of carbon emissions it does have an impact on the natural environment by the very nature of its process of energy production. Extracting water from different depths as well as the release of heated water back into the surrounding environment destabilizes eco-systems that are used to a fairly constant level of temperature [5]. Not only that, extracting water from different depths has the result of robbing the natural environment of micro-organisms which further disrupts the food cycle in the surrounding area. Finally the use of an OTEC closed system or an OTEC hybridized system has the potential for releasing toxic chemicals into the water resulting in a vast kill off of the surrounding marine life as a result of chemical poisoning.
Methods of Implementation
Closed Cycle
The OTEC closed cycle utilizes warm sea water as a mechanism for heating a fluid that that has a low boiling point, such as ammonia, in order to turn it into steam [5]. The resulting steam that is produced is then utilized in a traditional turbine cycle that transforms the mechanical energy produced by the steam turning the turbine into electrical energy through the use of a generator. In order to resume the process the ammonia vapor that is produced is rapidly cooled down and condensed utilizing cold water and is reconstituted back into its liquid form and is cycled through the system once more. When examining the OTEC closed cycle system it roughly resembles a similar cycle to that of a nuclear power plant wherein water is rapidly heated and cooled in order to continue the turbine cycle.
Open Cycle
The OTEC open cycle method of energy production utilizes a different method of energy production wherein warm seawater from the surface of the ocean is extracted and pumped into a vacuum chamber after which it is flash evaporated and the steam created used to power turbines [5]. It is at this point that it follows the same procedure utilized in the OTEC closed cycle wherein the cold seawater is introduced in order to condense the steam back into water. After the steam is turned back into water it is reintroduced back into the environment and the cycle is started all over again. It must be noted that both the open and closed cycle methods of energy production can in fact be hybridized into a single system wherein both energy and water desalinization processes can be created. Such systems do have a certain degree of commercial viability in countries within the Middle East such as the U.A.E and Saudi Arabia wherein their proximity to various coastlines and the ambient temperature in the water can be effectively utilizes as a means of clean energy production.
Environmental Impacts
As mentioned earlier, while the technology itself does not release pollutants into the atmosphere in what has become the widely accepted view regarding energy production and pollution the fact remains that an OTEC energy platform does in fact possess the potential to negatively impact the surrounding marine environment [5]. One of the integral processes in OTEC energy generation is the use of divergent water temperatures in order to properly complete the cycle, unfortunately this results in large discharges of mixed warm and cold water which is released near the surface of the ocean resulting in the creation of a plume of sinking cold water. While this may not appear to be polluting in the standard sense of environmental deterioration the fact remains that over a significant period of time this particular action results in temperature changes of 3 to 4 degrees Celsius within the immediate area [5]. Various studies have shown that changes in the ambient temperature in local marine environments have the effect of directly changing the hatching success of fish eggs, the development of larvae as well as lowering the reproductive success of various species in the area. Not only that the release of nutrient rich waters in normally low nutrient eco-systems changes the natural dynamic present in the area which could permanently and negatively alter the way in which marine life in the surrounding areas co-exist. It has been noted that sudden blooms of nutrient rich waters attract a variety of species such as jellyfish and pelagic invertebrates which can and will affect the mortality rate of juvenile fish, larvae and fish eggs within that particular ecosystem. As a result the entire habitat may become permanently inundated with new species that will effectively drive out the native species in the area resulting in a destabilization of the local ecosystem. While the danger of toxic chemicals entering into the local environment is low due to stringent measures regarding pressure and seepage the fact remains that there is still a possibility of it happening either through human error, accidental discharges or natural disasters. The recent oil spill in the U.S. off the Gulf of Mexico shows what could possibly happen should an accident happen on an OTEC platform and as such this poses a significant possible threat to the local marine life.
Wave Energy
Background
Wave Energy is the conversion of kinetic energy from ocean surface waves into mechanical energy by turbines and finally into electrical energy by a generator. While it is a promising renewable energy resource due to the prevalence of ocean surface waves and such presents itself as a potentially vast energy resource it is not a widely used method of extracting renewable energy from the sea. The reason behind this lies with the fact that several disappointing experiments have relegated it to the status of an emerging technology and as such despite wave energy sites having up to 90% of power generation capability at any given time compared to solar energys 20 to 30 percent it is still an under utilized technology [5]. The concept behind wave power is actually pretty straight forward, as waves are generated by passing winds over a particular area on the surface of the sea this transfers the kinetic energy of the wind into the water which creates movement which translates into a forward motion for the water which is widely known as a wave. An examination of the current status of wave energy reveals that surprisingly the development of the technology has reached a point wherein it has become commercially viable and is being offered by various companies as a means of renewable energy production. While the technology itself is still far from its build out completion stage due to the cost of production, estimated at 10 cents per kilowatt hour, the fact remains that with continuous improvements to technology wave power may in fact become a viable energy alternative in the future [5]. This is supported by the fact that various estimates show that if properly utilized wave power could provide 2 terawatts of electricity on a global scale which is equivalent to 1/5th of the current global energy demand.
Implementation
As mentioned earlier, wave power generates electricity by transforming the kinetic energy from waves into mechanical energy by a turbine and thus into electrical energy by a generator. While there are various designs that can be utilized in order to absorb the kinetic energy such as a hydraulic ram or a hydroelectric turbine most follow the same core design in that a semi submerged structure is located at an area with a high propensity for waves with a point absorber (area where the kinetic energy is to absorbed) being placed in the area generally perceived to be the most ideal in absorbing the kinetic force of the wave. Energy transmission is usually done through undersea electrical cables connecting the wave generator to an offshore transmission facility where the produced electricity is then sent to the main power grid.
Environmental Impact
While it has been shown that small scale wave energy plants have a potentially low impact on the surrounding environment it is only when large scale projects are created, meant to actually provide enough power for communities, that the potential for harm to the local ecosystem becomes a issue [5]. The reason behind this is quite simple, placing large objects barely above the surface of the water in areas propagated by marine life that similarly live near the crest of the waters surface has the potential to change the dynamic of the interaction between the local marine life and their natural environment [3]. Wave power plants in effect act as wave breakers for surrounding coastlines, while such a development would be advantageous for various harbors the fact remains that the continuous motion of waves acts as method of mixing the various upper layers of the sea which is essential to the spread of nutrients and various food sources to the different sea layers which is essential for local fish populations. While the technology itself is considered to be environmentally benign and in fact beneficial since it reduces the use of environmentally damaging fossil fuels the fact remains that the introduction of any artificial structure into a localized area still has the potential for disrupting natural habitats and should be a cause for concern.
Tidal Power
Background
Compared to other forms of ocean renewable energy production, tidal power has a distinct advantage in that it is the most predictable. This is due to the fact that tides have a regular cycle that can be easily predicted and as such due to their immense energy potential show promise as an effective alternative energy source [5]. The utilization of tidal power is actually quite simple, the built up kinetic energy in the tides, similar to wave power, is collected by turbines and used as a method of energy production [1]. Unfortunately the use of this particular type of technology is limited by the need for areas with sufficient level of flow velocities or high tidal ranges which are only in a few select areas around the world. Not only that tidal power stations entail an initial significant cost in construction and as such due to both environmental and economic problems tidal power stations are not as widely used as other forms of ocean renewable energy [2]. On the other hand it must be noted that with recent improvements to tidal power technologies they have begun to become more cost effective. This is not to say that they are anywhere near their build up completion compared to offshore wind power technologies however estimates of the ability of Tidal Power stations to produce electricity have been shown to reach levels of 2200 megawatts at peak operational capacity and such shows great potential as an alternative energy source should the technology become sufficiently developed.
Implementation
There are currently 3 methods of utilizing tidal power: tidal barrages, tidal fences and tidal turbines [5]. Tidal barrages work by building constructs near the mouths of tidal estuaries in order to capture the energy of tidal forces going in and out of the mouth of the naturally occurring structure. Unfortunately tidal barrages resemble dams and as such pose the same environmental implications that dams have on local environments. Tidal fences on the other hand are far more ecologically friendly since they consist of a series of turbines stretched across a channel wherein the tidal flow creates naturally fast currents. The advantage of tidal fences is the fact that they allow fish and other marine animals to go in and out of the tidal zone thus preserving the surrounding ecosystem. Tidal turbines on the other hand are utilized in channels with tidal currents enabling energy generation through the absorption of kinetic energy. It must be noted that the use of tidal turbines requires that the tidal currents have speeds of approximately 2 to 3 meters a second. Any lower and the energy produced is too low to be economical however any higher and the potential for the currents to damage the turbines increases.
Environmental Impact
The inherent problem with utilizing tidal plants is the fact that they have to be used at the mouths of estuaries in order to be effective in actually drawing power [2]. Unfortunately, by altering the flow of saltwater going in and out of estuaries tidal plants actually cause an imbalance in the local ecology such as the salinity of the water which can affect environments sensitive to these changes. Various studies show that estuaries are in fact valuable marine habitats which are in fact irreplaceable sources for marine life [1]. Constructing tidal plants at the mouths of estuaries usually involves closing off the area to direct interaction with the during the period of construction which usually proves to be devastating for the local marine life. Not only that, building tidal barrages also has the added effect of changing water depths and salinities creating a whole new environment within estuaries which may cause problems for various plant and animal species that cannot adapt fast enough to the sudden changes [2]. An examination of tidal power technologies reveal that the most environmentally benign methods of tidal power generation come in the form of tidal fences and turbines which allow water to easily go in and out of the channel without disrupting the entrance of various marine organisms. It is due to this that they are usually a recommended alternative for projects seeking to harness tidal power yet wish to preserve the local environment.
Offshore Wind Energy
Background
Wind energy is a form of energy generation wherein electricity is generated through the kinetic motion of prevailing winds against turbines set into the sea which produces mechanical motion which is turned into electrical energy by generators. It must be noted that wind energy is actually one of the oldest forms of renewable energy technology still utilized by human society. Its first inception was the windmill wherein wind that was blowing from a certain direction was utilized by a giant set of arms within a raised structure that used to move various gears contained within in order to process grain. The core design has roughly stayed the same in its current incarnation as a source of energy through the use of a wind turbine. Since it is one of the oldest forms of renewable energy it has reached its build out completion far faster than other forms of ocean renewable energy. This can be seen in its widespread use in Northern Europe wherein offshore wind energy has reached a capacity of 3.16 gigawatts with an additional 16 gigawatts expected through various wind farms that will be installed by 2014 in countries such as the U.K. and Germany. Further evidence that this particular technology has reached its build out completion can be seen in the fact that numerous commercial wind turbine suppliers, such as Siemens and Vestas, have appeared in order to supply the growing demand for wind energy especially in regions such as Western and Northern Europe. The fact is compared to other methods of ocean renewable energy, offshore wind generation, is the most economically feasible since it is nearly ( nearly being loosely used since it is still more expensive but prices are expected to dropped within the next 10 years) cost competitive compared to fossil fuel generation. Unfortunately, the use of this particular method of energy production is limited to areas with high prevailing winds [5]. While there are number of such areas located around numerous countries with shorelines the fact remains that their accessibility, initial costs and the feasibility behind their proper installation remains one of the current inhibitors behind further acceptance and use.
Implementation
An offshore wind turbine farm consists of a stable foundation for each turbine structure with a hollow metal framework for the main body and the turbine itself attached to the very top of the structure. The turbine itself is the main method of energy generation with mechanical energy produced by the spinning motion being directly translated into electrical energy through the use of a generator right behind the turbine mechanism. The electricity generated is collected via electrical cables located directly within the hollow structure of the main body and is sent via underwater cables to an onshore collection facility where the power is then connected to the main power grid. In order to facilitate better wind collection new innovations in offshore wind turbines come equipped with a sensor that adjusts the turbine depending on the direction of the wind in order to ensure that the operational capacity of the turbine is at its peak.
Environmental Impact
Due to the technology reaching its build out completion the utilization of offshore wind power as a method of energy generation is actually environmentally benign when examining the effects of wind farm construction in the long term. Gero Vella in his examination of the environmental impact of offshore wind generations states that while there is a distinct low level sound produced by wind farms which permeates the waters surrounding their operational sites such structures do not pose an environmental risk to the various marine species within the immediate area [4]. While there is an initial state of avoidance brought about by their construction and start of operation Vella states that various marine species eventually congregate around such structures due to the protection they provide against natural dangers within the immediate environment [4]. In fact wind farm structures create viable locations for habitats of various species of crustacean which in turn attracts fish and other marine organisms. The only negative impact such structures have on a species is that of the avian variety due to collisions with the structures during hours of operation [4]. Such a problem though is easily mitigated by placing wind farms in areas away from the migratory areas of avian species.
Conclusion
As it can be seen from the various facts and views presented in this paper the various technologies associated with ocean renewable energy are still far from their build out completion and as such pose both economic and environmental problems in their installation. OTEC facilities pose problems for various environments sensitive to temperature changes, wave power stations can affect the ability of ocean surface dwelling marine animals to sufficiently survive, and the installation and use of tidal power constructs poses a danger for various marine environments within estuaries. On the other hand as it can be seen in technologies such as offshore wind power stations as well as tidal turbines and tidal nets technologies can be adopted to become more environmentally benign through innovation in design and utilization. The case of offshore wind power stations is a clear example of what can be achieved should a method of renewable energy reach its build out completion and as such all the technologies mentioned could be innovated to an extent that their environmental impact can be minimized. In fact it can be said that all methods of ocean renewable energy development have the ability to impact their environment yet such impacts are usually site specific and scale dependent. It is due to this that is recommended that careful consideration be done when choosing sites for implementation as well as emphasizing the need for continued research in order to help such technologies reach their build out completion that much faster to enable cleaner energy production for the global community.
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