Calculating Potential Power Using a Barrage

Climate change, increasing energy demand and fluctuating fuel prices are some of the factors that have prompted exploration and development of renewable energy. Australian Government has committed immense resources towards renewable energy projects as a way of promoting clean energy production and increasing energy supply in the country. This report presents information about the possibility of harnessing ocean power along the stretch between Cape Jervis and Kangaroo Island. The information includes determining the amount of ocean power that can be generated along this stretch. The report has been prepared for the State Government of South Australia.

Barrage is the suggested method to be used for generating ocean power between Cape Jervis and Kangaroo Island. According to Manurkar (2009), Australia is one of the suitable locations for ocean power harnessing using barrages. The formula for calculating potential power using this method is as follows:

Where W = tidal power (watts); g = gravitational acceleration (9.81 m/s²); ρ = seawater density (1025 kg/m³), A = barrage basin’s horizontal area; h = wave height (m); and T = tidal period between peak and trough of the water wave (seconds).

The following are the values or assumptions used to calculate ocean power capacity between Cape Jervis and Kangaroo Island:

Wave height, h = 0.99 m – 0.45 m = 0.54 m (Australian Government 2017)

Tidal period, T = 12 hours 25 minutes = 4.47 x 10⁴ s (the system is designed for two way flow hence T = 2.1 x 10⁴ s).

The distance between Cape Jervis and Kangaroo Island is 25 km and let the breadth of the barrage be 5 km

Area, A = 25 x 10³ m x 5000 m = 1.25 x 10⁸ m²

Conversion efficiency = 33%

Therefore W =  = 8,726,520.5W = 8.73MW  

Based on the assumptions made above, the potential power that can be generated by the barrage is 8.73MW. However, the power conversion cannot be 100%. Hence since the assumed power conversion efficiency is 33%, it means that the average power that can be generated by the barrage on daily basis is  = 2.88MW.

A barrage is a special type of dam that is used for generating power from large quantities of moving water. The water is directed into and out of a river or bay as a result of tidal forces. When the tide is high, the barrage allows flow of water into the river or bay and then releases this water when the tide is low. To achieve this, tidal flow is measured continuously then sluice gates are controlled at crucial times of tidal cycle. There are turbines that are installed at the sluice gates to capture energy when the water is flowing in and out (Tousif and Taslim 2011).

Advantages and Disadvantages of Barrages

When the government decides to adopt this method of power generation, there are several potential benefits. One of these benefits is that power generated by a barrage is renewable and does not produce emissions. This is a major boost to the federal and state governments’ efforts of ensuring steady supply of energy and reducing greenhouse gas emissions. Another advantage is that the barrage does not need fuel to operate and it has very low operating and maintenance costs. Tidal energy is also very predictable because occurrence of tides can be easily projected after analyzing them for a certain period of time. This will help the government in ensuring reliable supply of energy in the region. Another advantage of a barrage is its durability. The typical lifespan of a barrage is about 100 years. This translates into very low lifecycle costs of tidal power generation. Last but not least is the high load factor for tidal energy (Maehlum 2013; Shah 2011).

However, there are several disadvantages that are associated with barrages. Some of these include: high initial capital, disruption of marine life cycles, disruption of spawning of wildlife such as fish in rivers or bays, possibility of turbines killing wildlife trying to dive through them, preventing movement of ships or boats, increased sediments, and limited locations (Tidalpower.co.uk 2015; Shah 2011).

Based on the calculations above, the assumed size of barrage can produce about 2.88 MW of tidal power. This amount of power can be augmented mainly by increasing the size of the barrage especially its width since the distance between Cape Jervis and Kangaroo Island may not be increased. The reason for increasing the size of barrage is because the amount of tidal energy generated is directly proportional to the volume of water directed into and out of the bay, which depends on the size of barrage. The bigger the size of barrage the more the amount of water collected and tidal energy produced, and vice versa.

Before installing the barrage, the government should establish strategies of maximizing tidal energy production. There is great need to conduct comprehensive feasibility study so as to determine the best location where to install the barrage. This location should be where the tides go up and down by the highest values i.e. where the wave height is maximum. This will significantly increase the amount of tidal power generated because power generated is directly proportional to the square of wave height.

Recommendations for Installation of a Barrage

The government should also analyze the underground conditions of the area so as to establish the most suitable type of foundation and construction methods to adopt. Additionally, there is need to determine the easiest way of diverting the water into the bay. Most importantly is to investigate the social, environmental and economic impacts of the barrage on the local area and its surrounding areas. In general, a lot of data and information should be collected and analyzed before installing the barrage (Wu, Xu and Xu 2016).

The following are some of the recommendations concerning installation of a barrage along the strength between Cape Jervis and Kangaroo Island:

The state government should find a way of determining alternative routes for boats and ships that were previously crossing through the section where the barrage is to be constructed. This will prevent the barrage from affecting shipping and navigation services in the area. 

The government has to find ways of capitalizing potential economic and social benefits during and after construction of the barrage. One of these is boosting local economy by improving hospitality services and tourism in general (Energy Systems Research Unit (n.d.)). This should aim at people that are likely to visit the barrage to witness its construction or operation. Another social impact the government has to develop is use of the barrage as a rail or road link between Cape Jervis and Kangaroo Island.

Reversible turbine should be used so as to enable two way power generation (Kempener and Neumann 2014).

The government should conduct comprehensive site investigation so as to establish the most appropriate type of foundation for the barrage and construction method to use.

The government should carry out comprehensive analysis on social, economic and environmental impacts of the barrage before its construction.

Last but not least, the government has to plan properly on how the barrage will be constructed, operated and maintained so as to prevent costly changes at later stages of the project lifecycle.

Conclusion

Construction of a barrage along the strength between Cape Jervis and Kangaroo Island is a feasible project for the state government of South Australia. Just like the 254MW tidal barrage (Sihwa Dam) in South Korea (shown in Figure 1 in the Appendix), which is the newest and biggest tidal barrage worldwide (Kempener and Neumann 2014), the planned barrage can be built quickly and revolutionize energy production in South Australia region. From the assumptions made, the barrage can generate about 2.88MW of tidal power. The turbines installed in the barrage are reversible. Before installing the barrage, the government should carry out comprehensive site investigation so as to identify the best foundation type and construction method. A study should also be conducted so as to identify social, economic and environmental impacts of the barrage in the region. Most importantly is for the government to develop strategies of capitalizing the benefits of the barrage and minimizing or mitigating any potential drawbacks, before, during and after its construction.

References

Australian Government (2017) Tide predictions for Australia, South Pacific and Antarctica [Online]. Available: https://www.bom.gov.au/australia/tides/#!/sa-cape-jervis [Accessed June 16, 2017].

Energy Systems Research Unit (n.d.) Tidal Power [Online] University of Strathclyde. Available: https://www.esru.strath.ac.uk/EandE/Web_sites/01-02/RE_info/Tidal%20Power.htm [Accessed June 16, 2017].

Kempener, R. and Neumann, F. (2014). Tidal energy technology brief. Abu Dhabi, UAE: International Renewable Energy Agency.

Kim, Y.H. (2016) Technology case study: Sihwa Lake tidal power [Online]. Available: https://www.hydropower.org/blog/technology-case-study-sihwa-lake-tidal-power-station [Accessed June 16, 2017].

Maehlum, M.A. (2013) Tidal energy pros and cons [Online]. Available: https://energyinformative.org/tidal-energy-pros-and-cons/ [Accessed June 16, 2017].

Manurkar, N. (2009) Tidal Power [Online]. Available: https://hydropower-tidalpower.blogspot.co.ke/2009/07/energy-calculations_07.html [Accessed June 16, 2017].

Shah, A. (2011) Advantages and disadvantages of tidal energy [Online]. Available: https://www.greenworldinvestor.com/2011/03/15/advantages-and-disadvantages-of-tidal-energy/ [Accessed June 16, 2017].

Tidalpower.co.uk (2015) The disadvantages of tidal power [Online]. Available: https://tidalpower.co.uk/disadvantages-of-tidal-power [Accessed June 16, 2017].

Tousif, S.M.R. and Taslim, S.M.B. (2011) Tidal power: an effective method of generating power. International Journal of Scientific & Engineering Research, Vol. 2, Issue 5.

Wu, Y., Xu, X. and Xu, H. (2016) Optimal site selection of tidal power plants using a novel method: a case in China. Energies, Vol. 9, No. 832, pp. 1-26.