Introduction to Hydro Power Generation
Hydro
power generation is the transformation of kinetic energy of flowing water into electric energy. Hydro power is the largest contributor and the most
efficient way of generating as a renewable energy and accounts for 16.3%
world’s total electricity and 66% of total renewable energy capacity [1].
According
to CEB Annual reports which were released in year 2015 and 2016, the total
hydro power contributes 46% to the total generation. From that, around 8% of the generation is satisfied by
Small Hydro power stations [2] [3].
Hydro power is fueled by flowing water and a
domestic source of energy which allows to produce energy without rely on international
fuel sources. It is more reliable and affordable compared to fossil fuels
because of it relies on water cycles which is driven by sun while fossil fuels
are rapidly being depleted. Another important advantage of hydroelectricity
is flood control.
Moreover, the water which is used in the power plant
can be utilized for another purposes such as agricultural purposes or
industrial purposes etc. It is also a flexible source of electricity which
could be able to response for frequency fluctuations. Once a hydroelectric
complex is constructed, the project produces no direct waste,
and in many cases, it has a considerably lower output level of greenhouse
gases rather than fossil fuel powered energy plants.
Hydro power plants can be categorized
under three types by the basis of generation method,
·
Conventional
(Dams)
·
Pumped
Storage
·
Run
of the river
When
we consider the small hydro power plants, both conventional and run of the
river method are being used mostly. Conventional and Pumped storage methods are
used in the power plants where large amount of power is generated with large
reservoirs.
Small hydro Power Plant
The definition of a small
hydro project varies but a generating capacity of up to
10 megawatts (MW) is generally recognized as small hydro power plant.
Small
hydro is the development of hydroelectric power on a scale suitable for local community
and industry, or to contribute to distributed generation in a regional
electricity grid. Mini hydro projects may be built in isolated areas that would
be uneconomic to serve from a national electricity grid, or in areas where a
national grid does not exist.
According
to Department of Meteorology Sri Lanka is rich with water resources with the
annual rainfall varies from 900 mm in dry zones and 5,000 mm in wet zones [9], which
may be used for electricity generation around the country, concept of mini
hydro power generation will be more applicable in Sri Lanka.
On
April 30, 1996,
the first modern mini hydro power project was commissioned at Dick Oya by Hydro
Tech Lanka (Private) Limited. Presently, over 15 private sector companies are
engaged in small hydro power projects and supply 293 MW of power generated in more
than 150 power plants to the national grid, which amounts to 17.5% of
hydro power generation in the country [8]. According
to the 2015 report on “Sri
Lanka Energy Sector Development Plan for a Knowledge-based Economy, 2015 – 2025, envisages the utilization of all
possible locations contributing of 873 MW of power by the year 2025”. [5]
Small hydro power plants
can be categorized into three types based on their capacity.
Small hydro type
|
Capacity
|
Pico hydro power
plant
|
Up to 10 kW
|
Micro hydro
power plant
|
10 kW to 250 kW
|
Mini hydro power
plant
|
250 kW to 10 MW
|
Structure of a Small Hydro power plant
A
hydro power plant includes the following components; A source of water,
pen-stock, turbine house, generator, transformer. First there must be a source
of water which have an energy as kinetic energy or potential energy. The major
difference of the small power plants is the way of distributing method of water
from the source. In this case there is a weir or small dam is created across
the water stream.
 |
| Small hydro power plant |
Using
pen-stock, the energized water flow is brought to the turbine house and it is allowed
to flow through the turbine and water outlet is directed to another water
stream or to the same water source. Kinetic energy of water is converted in to
rotational kinetic energy of the turbine and then it is converted in to
electrical energy by generator. Now it is ready to connect to the national grid
using a transformer. This is the simple process of a small hydro power plant.
Social, Economic and Environmental Arguments of Small Hydro Power Plants
Implementing
a small hydro power plant is not a complicated process. Developer should get
the approval from the relevant authorities as well as developer must concern about
social, economic and environmental issues while developing.
Environmental Concern
The
acquisition of lands for the project and accessing the roads and modifications
to the existing water stream and neighboring lands may disturb the
bio-diversity of the area and to some extent may be a damage to the
environment.
The
highest land requirement would be for the channel carrying water from the weir
to power plant, requires around 5 m width and could be over a kilometre long.
The total land requirement for a mini-hydro project would be around 5 acres. Environmentalists
claim that, “Fresh water living species with unique habitat and the indigenous
fish would be endangered or dead by the proposed project. Bio-diversity rich region hosting
aquatic orchids found in spray zones of waterfall, would be destroyed when the
flow in the waterfall gets reduced, they
claimed the power generation would change pH value (acidity) of water” [5].
But
in reality some of the issues which mentioned above do not occur practically. As
an example the pH value
of water does not change significantly because of flowing through the turbine..
In a small power plant, the water taken to the power generation is added back
to the water stream therefore it may not be a reason for the reduction of water
stream, as it is only affected to the area between weir and power house.
But
small hydro power plant releases less amount of greenhouse gases while large
hydro produces in large amounts; no emission of gases including carbon dioxide,
carbon monoxides, oxides of nitrogen, oxides of Sulphur, CFCs where thermal power plants emit.
Economical Concerns
Small
hydro power plants and other renewable energy sources affect positively to the economy when we
compare with cost of fuels and invest more money to extend national grid to
areas where implementation of grid is more costly as well as community with low
electricity consumption. As small hydro power produces renewable
energy, it may be the most economical way to produce electricity, when comparing
with the coal power plants. Because at present, the power generation sector is
dominated by liquid petroleum fuels. According to Sri Lanka sustainable energy
authority as at 2017, Sri Lanka expended 29.5% of its
export earnings on fuel imports[4]. The country’s financial resources are
heavily drained out from the country due to high import costs. Therefore, by
increasing the number of small hydro power plants may be able to reduce the weight
on fossil fuel based power plants.
Further,
small hydro power plants contribute to create job opportunities for both
skilled and unskilled people, will indirectly help to reduce the poverty. The
economic growth of the country occur due to the expansion of the consumer
purchasing of power. [5] & [6]
Social Concerns
Small
hydro plants are normally implemented in rural and hilly areas, as the main
target is to facilitate electricity to the areas where national grid is not
capable of supplying electricity. Primarily, these types of projects improve
the quality of the living of the people. Villages which are concerned directly and indirectly developed, as
the construction of a power plant renders villages with paved roads, culverts
and other infrastructure, while the provision of electricity uplifts the living
standards of communities.
Creation
of job opportunities will reduce so many social issues occurred due to
unemployment such as addiction to drugs, robberies and other socially
unauthorized actions. This depicts that the creation of small hydro power
plants positively affect to the society in different ways. [5] & [6]
Conclusion
and Future of the Small Hydro Power Industry
However,
there are many concerns with hydropower generation, particularly in large
dam facilities. Damming a river has a significant impact on the
regional ecosystem, by flooding upstream landscapes, disrupting
habitats for wildlife, blocking fish passages, and often
displacing local communities. In addition, dam failures can be
catastrophic, further disrupting landscapes and claiming the lives of those
living downstream.
Hydro
power plants are not completely free of greenhouse gas emissions. As with most
forms of energy, carbon dioxide emissions occur during construction,
particularly as a result of the large quantities of cement used, and loss of
vegetation in flooded areas creates methane which is another greenhouse
gas, as it matters to decay underwater.
But
hydropower is an abundant, low cost source of power in Sri Lanka despite
high upfront building costs. It is also a flexible and reliable source
of electricity compared to other renewable options, as it
may be stored for use later. Dammed reservoirs can also help with flood
control, be a reliable water supply, and may be used for recreational
purposes. Developing of small hydro power plants positively contribute to the
economy and society.
Sri
Lankan government is targeting to increase the power generation capacity from
the existing 4,043 MW to 6,900 MW by year 2025 with a significant increase in
renewable energy. In addition, it is planned to introduce 215 MW of small hydro
power to the national grid. [7]
Themal Manjuka Ekanayake
Department of Electrical Engineering
University of Moratuwa
References
[1]
“Electricity.” [Online]. Available: https://www.iea.org/statistics/electricity/.[Accessed:01-Dec-2019].
[2]
CEB, “ANNUAL REPORT 2016.” Ceylon Electricity Board, 2016.
[3]
CEB, “ANNUAL REPORT 2015.” Ceylon Electricity Board, 2015.
[4] “Economic Benefits.” http://www.energy.gov.lk/en/renewable-energy/economic-benefits(accessed Apr. 23, 2020).
[5]
T. Wijenayake, “Mini hydro-power projects and human issues,” Daily News.
[Online]. Available: http://www.dailynews.lk/2016/05/25/features/82707.
[Accessed: 01-Dec-2019].
[6]
colorlib, “Economic Benefits.” [Online]. Available: http://www.energy.gov.lk/en/renewable-energy/economic-benefits.
[Accessed: 01-Dec-2019].
[7]
“Sri Lanka - Energy | export.gov.” [Online]. Available: https://www.export.gov/article?id=Sri-Lanka-Energy.
[Accessed: 01-Dec-2019].
[8]
A. Wijayapala, “Development of
small hydro power plants”. Colombo 10 S. Godage, 2017.
[9] S.
User, “Climate of Sri Lanka.” http://www.meteo.gov.lk/index.php?option=com_content&view=article&id=94&Itemid=310&lang=en
(accessed Apr. 23, 2020).
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