sign in sign up
<<
Home , Electrical grid, Electric power, Energy technology, Hydraulic head, Hydroelectricity

Alternative Solutions: Hydro-Electric and Tidal Energy

American University Professor Stephen Macavoy University Honors Capstone Neslihan Yildirim Fall 2012

1 Neslihan Yildirim University Honors in Environmental Studies Capstone Advisor: Professor Stephen MacAvoy and Albert Cheh CAS: Environmental Studies

Alternative Energy Solutions In Order To Address the Energy Demands of the World: Hydro-Electric and Tidal Energy

Over the last two centuries, industrial activities, deforestation and the burning of fossil have released high concentrations of -trapping agents called greenhouse gases (GHGs) into the atmosphere. While a certain amount of is important to keep our climate warm and livable, these higher concentrations are warming the Earth’s surface to temperatures that threaten life on our planet. (CO2) and are two GHGs that have increased dramatically due to human activity. With the challenges faced by global warming, the world is faced with the threat of energy demand. The purpose of this capstone is to encourage the use of in order to best meet those challenges by providing detailed information on the scientific, economic and political backgrounds of two types of renewable energy resources: hydro-electric and tidal energy. The paper addresses several key topics including: How does the renewable energy function? Advantages/Disadvantages, Environmental Effects, Economic Feasibility, Current Electric Output/Capacity and Future Projections. Various mediums of research tools were used including energy reports published by the US Department of Energy (latest Annual Energy Outlook Reports) National Renewable Energy Laboratory, US Department of the Interior, and the Department of Energy and . The research has indicated that tidal and hydroelectric energy have their advantages and disadvantages in terms of economic feasibility. Although both can provide enough energy to sustain societies, they cannot address the energy demands of the world alone. A multifaceted approach needs to be taken to combine these energy resources with other renewables in order to sustain human lives on a global scale. Hydro-electric and energy should be used accordingly to best suit a country’s geographical location since each nation has its own unique natural resources to offer for total output.

2 Introduction The amount of electricity a hydro-electric system can produce depends on the quantity of passing through a (the of water flow) and the height from which the water ‘falls’ (head). The greater the flow and the head, the more electricity produced (Castaldi, 2003). In order to harness the energy from flowing water, the water must first be controlled. Thus, a large is created, usually by damming a to create an artificial or a reservoir. Water is then channelled through in the . The power of the water that flows through the dam’s tunnels causes the to turn and the turbines in turn make the generators move. The generators are that produce the actual electricity. The inside the actual powerhouse takes the AC and converts it to higher current. The engineers control the water intake system. When there is a lot of energy that is needed, most of the tunnels to the turbines are open and millions of gallons of water flow through them. When there is less energy needed, then the engineers can slow down the intake system by closing some of the tunnels. There are also outflow pipelines which carry the used water to re-enter the downstream river for a time use. Environmentally this is a great way of controlling how much energy is produced since water, essentially does not get wasted. Only the actual amount that is needed is used (US Department of the Interior). During , the intake system is helped by a . A spillway is basically a structure that allows water to flow directly into the river or other body of water below the dam, bypassing all tunnels, turbines and generators. Spillways prevent the dam and the community that surrounds the from being damaged. The spillways look like long ramps and are generally empty and dry most of the time unless it is needed in case the system is flooded (Water Encyclopedia). The water in the reservoir is considered potential (stored) energy. When the gates open, the of water flowing through the penstock becomes because it's in motion. The amount of electricity that is generated is determined by several factors. Two of those factors are the volume of water flow and the amount of . The head refers to the distance between the water surface and the turbines. As the head and flow increase, so does the electricity generated. (Tribal Energy and Environmental Energy).

3 Hydro- plants essentially capture the energy released by water falling through a vertical distance, and transform this energy into useful electricity. In general, falling water is channelled through a turbine which converts the water's energy into mechanical power. The rotation of the water turbines is transferred to a generator which produces electricity. An important calculation to consider when constructing and figuring out how much water flow is needed to achieve a certain kW of electric power per hydroelectric power plant is in the following equation/calculation:

Power Equation: P = eHQg whereby P stands for the electric power output in KW, e stands for efficiency, H stands for head in meters (how far the water drop is), Q stands for design flow (m^3/s) and g stands for the gravitational constant, 9.81 m/s^2 (Castaldi, 2003).

Types of Hydroelectric Plants As mentioned, Hydro-electric power plants can generally be divided into two categories. "High head" and “Low head” power plants. The “High head” are the most common and generally utilize a dam to store water at an increased elevation. The use of a dam also provides the capability of storing water during rainy periods and releasing it during dry periods. This results in a consistent and thus reliable production of electricity, able to meet larger demands. Heads for this type of power plant may be greater than 1000 meters. High head plants with storage are very valuable to electric utilities because they can be quickly adjusted to meet the electrical demand on a distribution system. (RETScreen International)

"Low head" hydro-electric plants are power plants which generally utilize heads of only a few meters or less. Power plants of this type may utilize a low dam to channel water, or no dam and simply use the ‘run of the river.’ Run of the river generating stations cannot store water, thus their electric output varies with seasonal flows of water in a river. A large volume of water must pass through a low head hydro plant's turbines in order to produce a useful amount of power.

4 Hydro-electric facilities with a capacity of less than about 25 Mega- (1 MW = 1,000,000 Watts) are generally referred to as "," although hydro-electric is basically the same regardless of generating capacity (RETScreen International).

An equation that best describes the “high head” versus “low head” relationship is Darcy’s Law. Darcy’s law allows an estimate of the average time of travel from the head of the to a point located downstream. It provides an accurate description of the flow of in almost all hydro-geologic environments. Henry Darcy was a French engineer who studied the movement of water through sand in 1856 (Division of ). He found that the rate of water flow through a tube is proportional to the difference in the height of the water between the two ends of the tube, and inversely proportional to the length of the tube. He also discovered that flow was proportional to a coefficient, K, which is called . Although Darcy's Law was based only on slowly moving groundwater in confined , most of the laws helped develop equations for other aquifer conditions we use today such as hydroelectric energy. The equation for Darcy's Law is

Q = - KA[(hA - hB) / L] OR Q = - KA(dh/ dl) where: Q=volume of water flow in ft3/day K=hydraulic conductivity in ft/day A=cross-sectional area in ft2 dh/dl=hydraulic gradient (change in head, dh with distance, dl)

The negative sign deals with the direction of flow that is toward the lower hydraulic head. The idea is that groundwater flows or moves from areas of higher hydraulic head to areas of lower hydraulic head as mentioned before (Pinder, 2006). It is based on Darcy’s that we can estimate the velocity of water or how fast the water is moving between points (as in the case with hydroelectric turbines). Velocity is calculated by using hydraulic conductivity, and hydraulic gradient. The equation used for calculating the velocity of water is as follows:

5 V= (K/n) (dh/dl) where N = porosity, K is a constant of proportionality (a way to relate the reduced flow rate to head loss and length of column) and dh/dl being the hydraulic gradient (Pinder, 2006)

"Pumped Storage" is another form of hydroelectric power. Pumped storage facilities use excess electrical system capacity, generally available at night, to pump water from one reservoir to another reservoir at a higher elevation. During periods of peak electrical demand, water from the higher reservoir is released through turbines to the lower reservoir, and electricity is produced. Although pumped storage sites are not net producers of electricity (it actually takes more electricity to pump the water up than is recovered when it is released) they are a valuable addition to electricity supply systems. Their value is in their ability to store electricity for use at a later time when peak demands are occurring. Storage is even more valuable if irregular sources of electricity such as solar or wind are hooked into the same system or (RETScreen International).

When designing a hydroelectric power plant, a number of elements and equipment need to be taken into consideration. Dam size, basin size and depth, control gates, turbines, generators, ect. have to all be examined. A strategic location for hydro-electric power plants is near waterfalls since water that crashes over the fall line is full of energy and can provide electricity for millions of homes. A famous example of this is the hydroelectric plant at which spans the border between the US and . The largest hydroelectric plant however in the world is the which spans the River in . It is 185 meters tall and 115 meters thick at its base (Division of Water Resources). It has a total of 26 turbines and a total generating capacity of 18,000 megawatts, which supplies energy to millions of homes, businesses and schools across China. Although the Three Gorges Dam is operating, engineers are still working to improve its efficiency. They are currently adding even more turbines and generators to the project (National Geographic).

6 Below is a picture of what the inside of a plant looks like:

Ontario Power Association Hydroelectric power provides almost all the energy for some nations. , , and the Democratic Republic of Congo all get more than 90% of their electricity from hydroelectric power plants. The largest U.S. hydropower plant is the 6,800-megawatt Grand Coulee on the in State. Completed in 1942, the Grand Coulee today is one of the world's largest hydropower plants, behind the 13,320-megawatt Itaipu hydroelectric plant on the Paraná River between and Brazil. It generated almost 58 million megawatts of in 2009. Furthermore, the , which is one of the biggest dams was built during the Great Depression. The Hoover Dam is still in use, providing power to 1.7 million people in Arizona, , and Nevada. It is often considered a great construction and is named after Herbert Hoover, the U.S. president who helped make the project happen. In terms of how much energy the system can produce hydroelectric power plants generally range in size from several hundred kilowatts to several hundred megawatts, but a few enormous plants have capacities near 10,000 megawatts in order to supply electricity to millions of people. According to the National Renewable Energy Laboratory, world hydroelectric power plants have a combined capacity of 675,000 megawatts that produces over 2.3 trillion kilowatt-hours of electricity each year; supplying 24% of the world's electricity (National Renewable Energy Laboratory).

7 Advantages There are many advantages as to why we should use and invest in hydro-electric power. The first advantage is that once a dam is constructed, electricity can be produced at a constant rate. If the electricity is not needed, then the ‘sluice’ gates can be shut in order to stop . This is also an advantage since the water can be saved for use another time when electricity demand is high. The lake that forms behind the dam can be used for water sports and other leisurely activities. Often large dams have become tourist attraction sites. Another advantage is that when in use, electricity that is produced by dam systems do not produce greenhouse gases nor do they pollute the atmosphere in any way as gas, or oil power plants do. Today hydroelectricity prevents the emission of GHG corresponding to the burning of 4.4 million barrels of per day worldwide, which is a very significant amount. Hydroelectricity also contributes to the storage of drinking water since the power plant collect rainwater which can then be used for consumption or for . In storing water, they protect the water tables against depletion and reduce our vulnerability to floods and . Hydro-electricity also promotes guaranteed energy and price stability. River water is a domestic which, contrary to or , is not subject to market fluctuations. Furthermore, with an average lifetime of 50 to 100 years, hydroelectric developments are long-term investments that can benefit various generations. They can be easily upgraded to incorporate more recent technologies and have very low operating and maintenance costs (US Department of the Interior)

Disadvantages As with any renewable , there are also various disadvantages to hydro- electric power. The first disadvantage is that it disrupts the aquatic . The dams developed across the can disturb aquatic life and lead to their large scale destruction. There is a chance that fish and other water animals may enter the penstock and ultimately the power generation turbines where they will be killed. Dams can also disturb the mating seasons and mating areas of the water animals. In some cases water animals have to swim against the water stream during breeding seasons. If a dam is built in the path of migrating fish they could be stuck

8 there and killed, never reaching their destination. This could devastate a population of fish. Another disadvantage of hydroelectric dams are the disruption that it causes in the surrounding areas. Plant and animal life around rivers thrive due to continuous fresh flowing water in the river. Due to the construction of dams, lots of areas have to be cleared that disrupt the plant and animal life. In many cases, trees have to be cut, which destroys not only the plant life but also the animals dependent on them. Even changing the course of the flow of water in the river due to the construction of the dam disrupts the plants and animal life. The third disadvantage is that it requires large land areas since power generation unit and transformers are needed to connect them to the . This requires forests to be cleared disrupting many local, natural ecosystems. Finally, because the dams are built on such a large scale, it is often necessary for humans to relocate. This becomes fairly inconvenient for a lot of people and thus causes large scale oppositions and revolts against the construction of dams. In for example, there has been a large opposition to the one of the biggest hydroelectric power projects named “Sardar Sarovar.” Though millions of people are to benefit from the project, the government didn’t manage the important issue of the resettlement of people who were displaced from the adjoining areas of project. This led to one of biggest protests in Indian history, which saw a number of hunger strikes, protest marches and even police attacks on the protesters (National Renewable Energy Laboratory).

Environmental Effects In terms of environmental effects/ waste, hydro-electric has its fair share of drawbacks. Although hydropower makes it possible to produce electricity without using or emitting fossil fuels, there are various environmental consequences that come with this technology. The first environmental impact is that since large reservoirs are required for the operation of hydroelectric power stations, this can create flooding of river banks which can destroy biologically rich areas such as wetland habitats. Another environmental impact is in the tropical regions, the reservoirs of power plants may produce substantial amounts of methane due to plant material decay in flooded areas (anaerobic environments), which is a GHG. Reservoirs can collect sediments which concentrates nutrients as as pollutants. When these sediments build up, then this

9 causes the reservoirs to become shallower. According to the World Commission on Dams report, “where the reservoir is large compared to the generating capacity (less than 100 watts per square of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, from the reservoir may be higher than those of a conventional oil-fired thermal generation plant.” Thus, this would cause much more damage and release of methane than it occurring through the natural forest decay. Some key factors that influence reservoir emissions are degassing (removal of gases from water for example), methane bubbles, plankton growth and decay, decomposition of flooded and soils, carbon inputs from watershed, growth and decay of aquatic plants, length of annual ice cover, CO2 diffusion, water level fluctuation and drawdown of vegetation (Window On State Government Energy Report).

Operating the power plant may also raise the temperatures of the water in the reservoir which can lead the plants and animals near the dam to migrate elsewhere, thus changing the local natural habitats of the region. Another impact is that hydroelectric projects can disrupt the aquatic ecosystems both upstream and downstream of the plant site. For example, some studies have shown that dams that are along the Atlantic and Pacific coasts of have reduced salmon populations since it prevents them from moving upstream. Some dams however such as the have installed ‘fish ladders’ to help fish migrate (especially those that try to swim upstream). Fish ladders are a series of wide steps built on the side of the river and dam and it allows the fish to slowly swim upstream instead of being completely blocked by the dam. Another drawback is that hydropower often entails changes to the natural variations in the water in a given natural watercourse (Renewableenery.no). The changes in the water level throughout the year can cause erosion and other problems in the surrounding land areas (such as the loss of riverbanks). Lastly, power lines that are built for the hydroelectric dams can affect bird populations through collision or by due to contact of the birds with these man made structures (National Geographic).

10 Economic Feasibility Hydroelectric electricity has various factors that contribute to its overall cost structure and economics. These costs include investment expenses (buying the land, building the dam, purchasing turbines, AC generators and other electrical equipment, ect.) and operating expenses throughout the facility’s lifetime (e.g. maintenance and salary costs). Approximately 75% of the hydroelectric kWh costs are made up of investment costs (initial capital and interest) which makes the overall costs stable during the electrical production stages (as compared to gas turbines, coal thermal, or pressurized water nuclear reactors). Today, the world’s hydroelectric plants have a total capacity of 675,000 megawatts that produce over 2.3 trillion kilowatt-hours of energy per year. This is providing roughly one quarter of the world’s electricity. Many countries outside of North America have the majority of their electricity coming from hydroelectric power plants. For instance, nearly a decade ago, 99% of Norway’s electricity was provided via hydroelectric power plants. The produced about 159.74 gigawatts in 2010 according to the Energy Information Agency, and that is approximately 6.67% of total U.S. production.

In terms of its cost structure, hydro-electric power has high initial costs. The average initial cost to set up a dam or a hydroelectric power plant is around $1.2 million while the annual costs for maintenance are around $12,368. However the initial costs are all dependent on the size and power generation capacity of the dam. For example, the Hoover Dam has a power generating capacity of 2.8 million kW and cost around $49 million to build which is almost the cost of a nuclear energy power plant (US Department of Energy). The Three Gorges Dam on the other hand, according to BBC News, cost around estimated $25-75 billion with power output of around 49 million kW hours (BBC News). Although a hydropower plant has a high capital cost, maintenance costs are minimal when looking at some other sources of energy production. The plant life can be extended economically by relatively cheap maintenance and the periodic replacement of equipment (replacement of turbine runners, rewinding generators, etc). Typically a hydro-power plant in service for 40 - 50 years can have its operating life doubled.

11 Comparing the cost of electricity with the initial investment of a hydropower system, the pay back period is short. Theoretically, a hydro plant should be able to produce electricity for a fixed amount during the life span of the unit. The operating costs should not change because there is no associated price to the water. Unlike in plants, the price of natural gas, coal, etc. fluctuates depending on what the market is doing. In terms of its fuel, hydro-energy does not require any fuel like most other sources of energy. This is a huge advantage over other fossil fuels whose costs are increasing at a drastic rate every year (US Department of the Interior). In terms of transportation, countries without big rivers are unable to get hydroelectric power. However, in countries that have big rivers, the of hydroelectric power is not an issue. Electricity is generated at the dam itself, and then transported to cities through electric cables. Therefore, as long as a country has rivers suitable for building dams, the electricity generated will be accessible to everyone connected to the energy grid. Essentially, the main costs of hydroelectric plants are largely the construction of the plant, with no further costs for fuel and its transportation. Hydropower is one of the cheapest ways to generate electricity. On average it costs about seven cents per kilowatt-hour to produce electricity from a hydroelectric plant. By refurbishing the equipment on the hydro equipment, you can increase its efficiency. An improvement of only 1% would supply electricity to an additional 300,000 households (Energy Information Agency). It is also important to note that the government subsidizes the costs and the power that is associated with hydroelectric power. The ownership and distribution of electricity is owned by various power marketing administrations. The role of these administrations is to market hydroelectric power at the lowest possible rates to consumers while adhering to business principles. These administrations, which are all a part of the US Department of Energy are the Bonneville Power Administration, Southeastern Power Administration, Southwestern Power Administration and the Western Area Power Administration.

When compared to other renewable energy methods, hydroelectricity remains quite competitive since it does not release GHG emissions from fossil fuel such as , , and . It also avoids the hazards and environmental and human health impacts of coal . Compared to , it generates no nuclear waste (so there is no drawback of finding solutions to store waste) and has

12 no dangers that are associated with uranium mining. Compared to wind and solar farms for example, hydroelectricity power plants are more predictable since it has a storage reservoir and can be generated to create power when it is needed. They can also be easily regulated to follow the demands and variations of power. Furthermore, in terms of meeting the energy demands of the world, hydroelectric power plants have the capacity to do so. For example, in 1998, the hydroelectric plants of Norway and the Democratic Republic of the Congo provided 99% of each country's power and hydroelectric plants in Brazil provided 91% of total used electricity. In the US, more than 2,000 hydropower plants make hydro-electric power the country's largest renewable energy source (at 49%) (US Department of Energy). The US has overall increased its hydroelectric power generation from about 16 billion kilowatt-hours in 1920 to nearly 306 billion kilowatt-hours in 1999. Canada however is by far the world's largest hydroelectric power producer. In 1999, it generated more than 340 billion kilowatt-hours of power, or 60% of its electric power, far outdistancing the U.S. hydropower percentage. The former , Brazil, China, and Norway are among the other top hydroelectric-generating countries (National Renewable Energy Laboratory).

Current Electric Power Output and Capacity Policies related to development of hydropower facilities vary by country and, in some cases, have a significant effect on these plants contributions in meeting needs for electricity. Each year, the U.S. Energy Information Administration (EIA) develops an outlook for the international energy markets, including electricity. The International Energy Outlook 2012 (IEO2012) projects markets through 2035. According to the IEO2012 renewable energy is the fastest growing source of electricity. Total generation from renewable resources will increase by 3% annually, and the renewable share of world electricity generation will grow from 18% in 2007 to 23% in 2035. According to their predictions, Hydroelectricity leads the field accounting for 35% of the total renewable energy in the US. Of the 4.5 million GWh of new renewables added over the projection period, 2.4 million GWh are attributed to hydroelectric power. However the types of renewable fuels used differ between the OECD and non- OECD regions. In non-OECD countries, hydropower is expected to be the predominant source of renewable

13 electricity growth. Strong growth in hydro is expected in China, India, Brazil, and many nations in Southeast Asia, including and . The United States currently has more than 2,000 hydroelectric power plants which account for more than half of the country’s renewable energy sources. China, Canada and Brazil are the only countries producing more hydroelectric power than the United States. However there is still unused capacity in hydroelectric power plants and a lot of power potential yet to be developed. According to a research done by the National Laboratory (INL), only 10% of the natural stream energy resources have been developed in the US and there are still 60% of the power available that is yet to be developed. The West is home to many of this undeveloped or untapped energy and there is a lot of potential there. The good news is that the majority of these potential can be harnessed without constructing new dams. They can be harnessed with existing technologies (United States Energy Information Administration Report).

When looking at hydroelectricity globally, the use of hydroelectricity and other grid- connected renewable energy sources is expected to grow slowly over the next couple of decades, increasing at a rate of 2.9% per year until 2035, according to the Energy Information Administration (EIA). Most of that growth will come from the construction of new hydropower and wind generating facilities and increased production. In 2010 for example, hydropower accounted for 2.51 quadrillion BTu of energy and the EIA projects that to rise to 3.06 quadrillion BTu by 2035. Therefore, the future of hydropower looks promising and is projected to increase in the non-OECD countries (Institute for Energy Research).

Future Projections Despite its ‘expected growth,’ the future of hydroelectric power in the US, as well as worldwide, is complicated. As we know, the capabilities of hydroelectric power have been maxed out here in the United States, however this is not the case in most other countries. There are a range of large scale hydro electric construction projects in the works in the developing industrial nations. The true future of hydroelectric power worldwide depends on the abilities of scientists to make technological breakthroughs. Although the IEO2012 projects a growth in

14 hydroelectricity, there also some contradictory evidence that in fact argue that figuring out how much hydropower will be available in the future is becoming more and more difficult. The reason is because the old way of predicting stream flow by taking records of past flow and designing dams based on those amounts is becoming complicated due to climate change. Already we can see water flow flowing less and even drying in many tropical regions. Shrinking rivers have already reduced or even shut down power generation in existing dams. For example, Kenya is developing geothermal and to compensate for unreliable hydropower since they have been hit hard by . According to the report “Projected Changes in Hydropower Generation 2050” completed by scientists at the Norwegian University of and Technology have found that while mid-latitude areas will experience reductions in river flow (thus hydropower reductions) some areas such as Northern Europe, East Africa and Southeast Asia will probably see a boost. Therefore, the predictions made by IEO2012 are accurate but considerations of where there will be future water shortages in various geographical regions will need to be taken into account when discussing hydropower as a renewable source in meeting the energy demands of the world.

Tidal Energy Besides the construction of dams, there are also other types of Hydroelectric plants where energy can be captured such as . Tidal Energy uses the natural ebb and the flow of coastal tidal (which are created mainly by the relative motion of the Earth, moon, sun and the gravitational interactions between them) in order to instigate tidal power plants to produce electricity. The coastal water levels change twice on a daily basis, which fills and empties natural basins along the shorelines. It is these currents that flow in and out of the basins that interacts with the mechanical devices. Since there are about two high and two low tides each day, the electrical generation from tidal power plants goes through periods of maximum electricity generation every six hours or so (Department of Energy and Climate Change). Essentially, the tides contain the energy that can be harnessed for this electricity production through tidal energy generators (underwater turbines). The two types of energy that can be harnessed are kinetic and

15 potential energy. Kinetic energy can be harnessed from the ebbing and surging tides while the potential energy can be harnessed from differences in the high and low tides (EWTEC).

Tidal energy can be harnessed and generated through various methods. Traditional tidal electricity generation involves the construction of a barrage across an estuary to block the incoming and outgoing tides. Tidal fences for example block a channel, which forces water to go through it and turn its turbines to generate electricity. One way to harness tidal energy is through tidal streams. Tidal stream generators make use of the kinetic energy of moving water to power turbines in a similar way that wind turbines use wind to power turbines. With barrage tidal plants, they make use of the potential energy in the difference in height between high and low tides. Basically, a dam or barrage is installed, usually where there is a narrow water channel with gates and turbines at certain points. As water flows through the turbines, they turn a generator that produces electricity. Tidal turbines work like an underwater wind turbines. They use the tides to turn blades and to essentially create electricity. The barrage tidal plants, which are the most commonly used today have three main parts to them. These include the barrage, sluice gates and a turbine. The barrage acts much like a dam by holding back water to be later released. The sluice gates allow water to flow through the turbine. The turbine in turn spins as the water flows through it which rotates an electricity producing generator. The turbines in the barrage can be used to pump extra water into the basin at periods of low demand. This usually coincides with cheap electricity prices, generally at night when demand is low. A company will therefore buy the electricity to pump the extra water in, and then generate power at times of high demand when prices are high so as to make a profit. In order for tidal energy to be economical, a tidal range of at least 7 meters is required and the overall magnitude of these effects is essentially dependent upon the gravitational pull from the sun and moon and the local coastal habitat interactions (Energy World).

16 Here is a picture of the daily distribution of tidal phases that occur:

Source: Energy World

When looking at the power available from these kinetic systems in a turbine at any particular time mathematically, engineers use the following formula:

where: Cp = the turbine power coefficient P = the power generated (in watts) p = the density of the water (seawater is 1027 kg/m³) A = the sweep area of the turbine (in m²) V = the velocity of the flow

17 Advantages There are various advantages of tidal energy. One big advantage is its predictability. The size and the time of tides can be predicted very efficiently. In order to harness tidal waves, we just need to follow tidal cycles. Strong tidal waves are very much capable of generating a high amount of electricity with 80% more efficiency than coal or oil and 30% more than according to the US Department of Energy. Furthermore, another advantage is that once the tidal power plant structures are built, the energy is free, clean (does not generate emissions or wastes) and renewable. This is a huge benefit especially when considering this type of energy in the long run and running its cost- benefit analysis. Another advantage is that its maintenance is cheap and the efficiency of the technology increases with better and stronger waves, thus the energy does not fluctuate much if its at this level. Furthermore, tidal energy can also be effective at low (unlike wind energy for example). Water has 1000 times higher density than air which makes it possible to generate electricity at low speeds. Calculations show that power can be generated even at 1 m/s (equivalent to a little over 3 ft/s). Tidal plants also use a source that is abundant in (ocean water) which is another advantage since there is no threat of ocean water depletion (at least anytime soon). Lastly, tidal power plants have long lifespans. This ultimately reduces the cost these power plants can sell their electricity, making tidal energy more cost- competitive with other renewable as well as fossil fuel sources (Ocean Energy Council).

Disadvantages Tidal energy also has some disadvantages. One of the major drawbacks that are holding investors and dealers back from moving towards tidal energy is the cost incurred to develop powerful plants and devices. Most people are looking at the short term costs and neglecting the long term maintenance costs of tidal energy. Another disadvantage is its availability for everyone across the globe. The only cities or countries that can benefit from this technology are the ones that are surrounded by strong tidal waves. Places that don't have strong tidal waves or are far from tidal energy do not have facilities to generate this power (which in that case we would need to develop ways to transfer these energies from one country or city to another, leading to more costs). Even when the electricity is generated, it would average to around 10 hours a day

18 (depending on how strong and how high the tides are) which tidal energy alone would not be enough to cover a full 24 hour day energy demands without another complimentary renewable energy such as wind or solar power. Another disadvantage is that the barrages may also affect tidal levels. The change in tidal levels may cause flooding of the shoreline and thus affect the coastal beach areas which are used by people for swimming and recreation. Another disadvantage is that salt water causes corrosion in metal parts of the tidal power plant. It can be difficult to maintain tidal stream generators due to their size and depth in the water. Finally, another disadvantage is that tidal power plants need to be constructed close to land (as opposed to wind energy which can be located far out in the sea). This is an area where various technological solutions are being worked on. If engineers can come up with a technology that can exploit weaker tidal currents at locations further out in the sea, then this would be very beneficial (Ocean Energy Council).

Environmental Effects In terms of environmental effects, tidal power plants can affect the of marine life. Turbine barrages disturb the migration routes of fishes, movement of marine animals and thus reduce fish populations, which would be a huge controversy amongst environmentalists. In terms of waste, mechanical fluids such as lubricants can leak out, which may be harmful to the marine life nearby. In order to make sure that this doesn't happen, proper maintenance can minimize the amount of harmful chemicals that may enter the environment. The quality of the water in the basin/estuary and a change in sediment levels can also occur due to tidal turbines which would affect the turbidity of the water and animals that live and depend upon it (such as fish and birds) (Department of Energy and Climate Change).

Economic Feasibility When looking at tidal energy from an economics perspective, the cost of setting up a tidal power station can be very high, although once in place the operating costs are low. The cost of building a Tidal Power Plant can have a high capital cost. In the United States, the estimated total cost of installing a tidal energy turbine is $4,715,000. The estimated commercial plant capital

19 cost of a tidal energy farm is $23,630,000 (assuming there are on average 12 turbines). Essentially, the cost of tidal energy is very site specific, and influenced by , distance to grid, and and volume of the current. As an example of the cost of setting up, a proposed 8000 MW tidal power plant and barrage system on the in the UK has been estimated to cost $15 billion, while another in the San Bernadino strait which would produce 2,200 MW as a tidal fence in the Philippines will cost an estimated $3 billion (Australian Institute of Energy). There are currently two large commercial scale tidal power sites in operation around the world. The first is a 240 MW bulb turbine at the mouth of La Rance estuary in . That site powers a city of 300,000 people. The second is the Bay of Fundy plant in Canada which generates 16 MW powering around 4,500 houses in the area. In terms of its operation and maintenance, since tidal power plants do not require any fuel, its operation and maintenance costs are very low. The only maintenance it would really need is to make sure that its metal parts are in tact and that there are no harmful chemicals that are being released into the water during its operation. In general, this technology is still not cost effective and more technological advancements are required to make it commercially viable (Department of Energy and Climate Change). Furthermore, the transportation of tidal energy as well as setting up the actual plants within the oceans can be quite cumbersome and expensive. Moving and placing these big physical structures in the water can require the use of heavy machinery to lift and place it in the water, thus leading to high initial transportation costs (Denny, 2009)

Future Projections Wave, tidal and ocean energy technologies are just beginning to reach viability as potential commercial power sources. While just a few small projects currently exist, the technology is advancing rapidly and has huge potential for generating power. The Northwest could become a world leader in this new arena if we invest now. Thus, in terms of meeting the global energy demands, tidal stream technology alone cannot currently play a big role in meeting the global energy demands. However, tidal energy along with other marine technologies can help meet government targets for CO2 and other fossil fuel reductions. Although no commercial wave or tidal projects have yet been developed in the United States, several projects are planned for

20 the near future, including projects in the Northwest. AquaEnergy Group, Ltd is currently designing and permitting a one-megawatt demonstration plant at Makah Bay, Washington. Furthermore, Ocean Power Technologies has received a “preliminary permit” to explore construction of North America’s first utility-scale wave energy facility off the coast of Reedsport, . With the support of the Oregon Department of Energy, Oregon State University is also seeking funding to build a national wave and tidal energy research facility near Newport, Oregon. Several tidal power projects are also being explored in the region. Tacoma Power has secured a “preliminary permit” to explore a tidal power project at the Tacoma Narrows, one of the best locations for tidal power in the country, and Snohomish County Public Utility District has received “preliminary permits” for seven other potential tidal power sites in the Puget Sound. Therefore, in order to have a strong grasp on future projections on this technology, we need to start with these projects and see how much electricity they generate. Once we can get several data and compare the different regions with one another, then we can begin to determine how feasible tidal energy will be (Renewable Northwest Project). The United States receives a lot of wave energy along its coastlines each year, and tapping just one quarter of this potential could produce as much energy as the entire U.S. hydropower system. Oregon and Washington have some of the strongest wave energy resources and could eventually generate several thousand megawatts of electricity using wave or tidal resources.

Although the US has not yet developed in tidal energy, according to the Carbon Trust, tidal energy is ready to become a significant provider of clean energy for the UK and the globe. For example, in the UK alone some 15-20% of the its electricity demand could come from marine renewables such as wave and tidal technologies. This is very significant considering how many types of renewable energy technologies that are out there (The Guardian). Furthermore, if we combine tidal energy with solar and wind technologies, then this could further lead us to meet greater energy demands of the world.

21 Conclusion Hydro-electric energy is a great renewable energy source with new constructions and technological advancements rapidly on the rise. There are currently 14 large scale projects that are being developed and scheduled to completed between 2012 and 2022 in China, India, and Berma (with most being in China). Some hydropower stations such as the Hoover Dam in the US are considering changing their turbines with new ones that will work more efficiently at lower water levels (IEEE). Although hydroelectric will be a big part of our future electricity generation, a country cannot rely on hydroelectricity alone for its electricity supply. Therefore it is of interest to countries to combine this technology with other forms of technologies.

Furthermore, although tidal power is not yet widely used, it has a great potential for future electricity generation since they are more predictable than most other renewable technologies such as wind energy and solar power. Since oceans cover almost two thirds of earth's surface, they truly present renewable energy source with extreme potential and one worth of further exploration. Some ocean techniques that are being developed are wave energy (kinetic energy that exists in the moving waves of the ocean caused by ) and ocean conversion (OTEC) which is a method for generating electricity that uses the temperature difference between deep and shallow waters (since the water gets colder the deeper you go further). However current technologies aren't at the right level to capture this potential. Problems such as ecological, size and cost of the power plants remain to be an issue that needs addressing (UNICEF). All that ocean or tidal energy needs now is the technology that will be capable of exploiting its high potential of energy. If we can manage to do that then these renewable energies can have a huge impact on how we address moving sustainably into the future.

22 Bibliography

"Basic ." North Carolina Department of Environment and Natural Resources. Division of Water Resources, Web. 14 Nov. 2012. .

Castaldi, Duane, Eric Chastain, Morgan Windram, and Lauren Zytinck. A Study of Hydroelectric Power: From Global to Local Application. Rep. 2003. Center for Advanced Studies and Experience, Pennsylvania State University, Print.

Combs, Susan. "Hydropower." Window on State Government Energy Report. Rep. Web. 21 June 2012. .

Denny, Eleanor. : The Economics Of Tidal Energy. Rep. no. 5. Vol. 37. Dublin, Ireland: Department of Economics, University of Dublin, 2009. Print.

"Environmental Impact of Hydropower." RenewableEnergy.no. Web. 21 June 2012. .

"E.ON UK: Tidal Energy." Energy World. E.On UK, Web. 11 June 2012. .

"EWTEC Tidal Energy Conference." EWTEC. European Wave and Tidal Energy Conference, 2009 Web. 11 June 2012. .

“Hydro Power Topics.” US Department of Energy. Energy Efficiency and Renewable Energy. Web. 21 June 2012.

"HydroPower Resources." The Future of Energy. Web. 28 Nov. 2012. .

Griffiths, Dan. "Three Gorges Dam Reaches for the Sky." BBC News. BBC, 19 May 2006. Web. 21 June 2012. .

Goodall, Chris. "Tidal Energy- UK's Best Kept Secret." Guardian Environment Network. The Guardian News and Media, 18 May 2011. Web. 11 June 2012. .

"Hydroelectric Energy." National Geographic Education. National Geographic Education, n.d. Web. 21 June 2012. .

"Hydroelectric Power." Water Encyclopedia.Web. 21 June 2012. .

23 "Hydropower." Tribal Energy and Environmental Energy. Web. 14 Nov. 2012. .

"Ocean Energy." Our Energy. UNICEF, Web. 11 June 2012. .

"Outlook on the Future of Hydro Development Worldwide." Renewable Energy World. Web. 27 Nov. 2012. .

Pinder, George Francis, and Michael Anthony. Celia. Subsurface . Hoboken, NJ: Wiley-Interscience, 2006. Print.

Reclamation, Managing Water in the West: HydroElectric Power. Rep. US Department of the Interior, Print.

"Renewable Energy: Hydroelectric Energy." National Renewable Energy Laboratory. Web. 21 June 2012.

"Renewable Energy." Institute for Energy Research. Web. 27 Nov. 2012. .

"Renewable Northwest Project." Wave & Tidal Energy Technology: Renewable Northwest Project. Web. 28 Nov. 2012. .

RETScreen International: Clean Energy Support Centre. Small Hydro Project Analysis. Rep. Minister of Natural Resources Canada, 2001-2004. Print.

"Tidal Energy." Australian Institute of Energy. Australian Institute of Energy, Web. 11 June 2012. .

"Tidal Energy and Power." Tidal Energy. Ocean Energy Council, Web. 11 June 2012. .

"Tidal Power Technology." Department of Energy and Climate Change. Department of Energy and Climate Change, Web. 11 June 2012. .

"The Future of Hydropower." IEEE Spectrum. N.p., n.d. Web. 27 Nov. 2012. .

United States Energy Information Administration. Annual Energy Outlook 2012 With Projections to 2035. Rep. Washington, D.C.: U.S Department of Energy, 2012. Print.

24