Shimiao Cheng

Hydroelectric Energy in Ireland

Abstract

Hydropower is renewable energy that comes from the moving water or water fall, it could be transformed into electric power, mechanic power and etc. The following water cycle (Fig.1) shows that how Hydropower is renewable, long lasting and a clean power resource. when sun heats the water in rivers, oceans and lakes, turning some of them into water vapor. The water vapor rises and turns into clouds and eventually release the water as rain or snow back to earth again. In this paper I am going to present the history of human using Hydro energy and the way of generating Hydroelectricity, after that I will talk about different types of Hydropower station and the impacts from them, and then will be a case study from a Hydroelectric power station in Ireland, at last is the comparison between different types of green energy and point out why Hydro power has unique benefit from the others.

Figure 1. Water cycle [3]

Introduction and Background Technology

The history of humans using water power were back to 250 BC, as a clock. Egypt, China and India are one of the earliest countries started using falling water to provide power for water wheels, Turpan water system and saw mills, as well as a host of other applications. "In the earlier of 1980s, first electricity power was generated from a waterwheel on the Fox River in Wisconsin, two years after Thomas Edison unveiled the incandescent light bulb" [2]. In now days, Hydroelectric is widely used in the worldwide, the percentage of electricity generated worldwide that comes from hydropower has reached to 20% by 2006 and has installed capacity of 777 GW with supplied 2998 TWh [1]. In figure 2 shows some top Hydroelectric generating countries at 2006 and 2010 [21]. From figures we can see that as time goes along, Hydroelectric power becomes more and more popular in the worldwide.

Figure 2. top Hydroelectric generating countries [4]

The way of generating Hydroelectric power is capture the energy released by water falling. In general, the mechanical power from falling water went through penstock channel, which rotate the water turbines (Figure 3) and transferred mechanical power into a generator that produces electricity. The amount of electricity which can be generated at a hydroelectric plant is dependent upon the vertical distance through the water falls (measured in meters) and the flow rate (measured in cubic meters per second). By calculating those two factors we can roughly know the power generate capacity of a river or lake, then we can decided if it worth to build a Hydroelectric power station. According to capacity of a Hydroelectric power station, we can separate them as Large Hydropower and Small Hydropower station.

Figure 3. Hydroelectric power generation [5]

Sizes of Hydropower Plants

Large Scale Hydropower

Although definitions vary, the large hydropower as facilities that have a capacity of more than 50 MW [9] and normally produce electricity for government or electric utility projects. Most large-scale hydropower stations used a dam to store water from a river or lake. When the stored water is released, it passes through and rotates turbines, which spin generators to produce electricity, just like the mechanism that I mentioned above.

"The Three Gorges Dam is the world’s largest capacity hydroelectric power station with twenty-nine 700 MW turbines and a total capacity of 20,300 MW. Eventually, it will have 32 generators: 30 main generators, each with a capacity of 700 MW, and two plant power generators, each with capacity of 50 MW, making a total capacity of 22,500 MW [6]. Among those 32 generators, 14 are installed in the north side of the dam, 12 in the south side, and the remaining six in the underground power plant in the mountain south of the dam. The expected annual electricity generation will be over 100 TWh" [7].

Figure 4. China's Three Gorges Dam [8]

Small Scale Hydropower Station

Normally a small hydropower station can generate up to 500 kilowatts [9] of electric power for homes, hospitals, schools, workshops and etc. It does not require an expensive dam or storage facility to be constructed, but rather to diverts some of the water from the river which is channeled along the side of a valley before being ‘dropped’ into the turbine via a penstock. In figure 5 [10], the turbine drives a generator that provides electricity in the power house. The amount of electric power can be calculated as:

Gravity* vertical distance between forebay tank and the power house*water flow rate

The transmission line also can be extended to a local village to supply domestic power for lighting and other uses. This scale of hydropower station is particularly suitable for suburban or mountain village area.

Figure 5. Small Scale Hydropower Station

Usage in Ireland

Ireland has a long history of using hydro power, The water flows from the mill pond shown in T0122 : Watermill, Irish National Heritage Park onto this wheel, figure 6, has designed utilized the power of water that struck the blades of the wheel to rotate the shaft and millstone, which used to grind corn (Neumann, 2009, online). Reproduction of the type introduced in the 7th Century A.D. still made to the 10th Century and some in use up to the 20th Century [11]. By the beginning of the 20th century, approximately 1800

mills were in operation [14].

Figure 6. Horizontal Waterwheel in Irish National Heritage Park, Co. Wexford

(Hawgood, 2009, online)

Ireland’s largest hydroelectric scheme was the vision of a Drogheda born Engineer, Dr. Thomas McLoughlin who was in the employ of German company Siemens-Schuckertwerke in the 1920’s. The scheme was developed and in 1923 McLoughlin presented his proposal to a number of Government Ministers. In 1924 the completed proposal was handed over to the Government for discussion and in 1925 construction began in Ardnacrusha with first generation in October 1929 [12]. When it started in operation, the installation had sufficient capacity to satisfy total national demand [13].

There is a list of Hydroelectric stations in Ireland today, shows in figure 7 [15].

Figure 7. List of Hydroelectric stations in Ireland

Case studies -- Micro-scale hydro power project, Kilkenny, Co. Kilkenny

Due to the time limitation, this case study from reference [23]. "This micro-scale hydro power plant, set up in 1994, is a joint venture between an energy consultant and the owner of a sawmill located at the site of an existing water mill (Figure 13). Their objective was to refurbish the water mill in order to meet the electricity needs of the sawmill and generate revenue from the sale of surplus electricity. The mill is listed as being of industrial heritage value and so retention of the existing wheel was necessary. Planning restrictions meant that only renovation of the existing site was possible. The refurbishment project involved the installation of 3 key pieces of equipment namely an open flume propeller turbine, an undershot waterwheel turbine and a tube turbine. All three machines were manufactured on-site. Average flow of water and head are 30m3/s and 1.5m respectively. The plant operates for 7,700 hours per year producing an annual energy output of 400 MWh to 600MWh (i.e. 65kW).The total investments, paid solely by the two partners with no loans or grants, were estimated to be €47,300. The estimated life time of the installation is about 50 years owing to the simplicity of the installation. By displacing the need to burn fossil fuels, the installation reduces carbon dioxide emissions by approximately 5,000 tonnes per year. In addition, emissions of gases that contribute to acid rain and air pollution are avoided. Aquatic life is protected through the installation of electric fish barriers on the tailrace. Furthermore, the mill wheel has a beneficial aerator effect".

Figure 13. Hydropower installation in Kilkenny

Social and Environmental impact

Hydroelectric power plants do not produce any of the standard atmospheric pollutants such as CO2 or SO2 given off by fossil-fuel-fired power plants. In this respect, hydropower is better than burning coal, oil, or natural gas to produce electricity, as it does not contribute to global warming or acid rain. Similarly, hydroelectric power plants do not result in the risks of radioactive contamination associated with nuclear power plants [16]. However, Hydropower stations does contain some other environmental impacts.

The most obvious impact of hydroelectric dams is the flooding of large areas of land, much of it previously forested or used for agriculture. The size of reservoirs created can be extremely large. The La Grande project in the James Bay region of Quebec has already submerged over 10,000 square kilometers of land; and if future plans are carried out, the eventual area of flooding in northern Quebec will be larger than the country of Switzerland. The flood has not only destroyed land but also flooded the homelands of native

peoples, whose way of life has then been destroyed [20]. Because of Three Gorges Dam, China has relocated 1.24 million residents [17], about 1.5% of the province's 60.3 million and Chongqing City's 31.44 million population [18]. About 140,000 residents were relocated to other provinces [19].

Hydropower projects have impacted fish and fisheries in a number of ways. They have significantly changed fish habitat quality and availability, also changed flow regime (maintenance flows and ramping), and fish passage. Although, many of dams has provided fish passes but it still not comparable with nature path. Fish are very often dead or injured when passage through turbines, in figure 8 (http://www.fws.gov/midwest/Eco_Serv/ferc/index.html), shows fish crowd together under down stream of a dam and they can not pass through to up stream of the river.

Figure 8.

Hydropower plants can impact water quality, flow and often experienced both upstream and downstream of a dam. It also caused low dissolved oxygen levels in the water, the problem that is harmful to riverbank habitats and is addressed using various aeration techniques, which oxygenate the water [9].

In figure 9 [21], shows a comparison table of positive and negative points of building a Hydroelectric power station. Even Hydroelectric is a clean, long lasting and renewable energy, it still combined with social and ecological environment impact. Because of flooding, some species may disappeared before scientist can found them.

Figure 9.

Compare With Other Renewable Energies

By now, the most popular renewable energies in the world including Hydro power, Wind power and Solar power. In figure 10 shows comparison of power technologies that are utilized in the United States today [22]. From the figure we can see that Hydro energy has the most capacity with the lowest price compare to the other renewable energies.

Figure 10.

In figure 11[21], shows that renewable energy usage in Ireland from 1% at 1973 increased to 5% at 2009, and the Hydro power takes 60% out of the whole renewable energy usage. The second largest part is wind power, it is also a very rich renewable resources in Ireland. By combine hydro and wind power together, Ireland could become a totally "green" country.

Figure 11.

Conclusions

All in all, Hydroelectric power is a clean, long lasting and renewable energy. Depend on size of a hydroelectric power station, cost can be vary. For those countries who own big dam stations, the total cost could be over 30 billion dollars, such as China and United States. Although large hydropower stations could generate larger electricity power, the impacts combined with it could not be ignored, especially the environment impact. Based on Ireland river map, small scale hydropower stations could be the best choice, they can generate enough electricity power for people living in villages around river bank. Also with limited environment impacts and lower spending rate for government.

Figure 12 [21].

Appendix

References

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