Page | 1 1. Background 1.1 Project description: Pumped storage hydroelectricity is a type of power generation used by some other power plants for load balancing. It is only method of large scale electrical energy storage in widespread use today. The basic concept is simple. Energy is stored as hydraulic potential energy by pumping water from a low-level into a high-level reservoir. When recovery of energy is required, the water is returned to the lower reservoir through turbines which drive electrical generators. It helps on load balancing only. No extra energy is added, it only stores electrical energy and provides it according to need. However we don‟t have any extra or off -peak energy in our system during dry period but during wet period we would have enough amount of energy to pump water. So seasonal Pumped storage hydropower can be integrated in our system to cover the peak demand. The energy used in pumping a volume „V‟ of water of density „ρ‟ and through a height „h ‟ with a pumping efficiency „ηp‟ E1= (ρgh/3600* ηp) MWH……………………... (1) The energy recoverable with a regeneration efficiency „ηg ‟ E2= (ρgh * ηg /3600) MWH……………………. (2) Where „g „is the acceleration due to gravity Typically, the overall efficiency (E2/E1) = ηg * ηp; which is in the range 70-80 % 1.2 Description of problem: Currently we are facing daily load shedding of 12 hours. To overcome this, we are using inverters and other devices to store electrical energy for our household works. We are also using petroleum products to run diesel plant and thermal plant. During the era of energy crisis we are using non-renewable energy recklessly. But then this stored energy cannot be used to run an industry or do other works which consumes huge amount of electrical energy. These energy storing devices have become one of the major consumers of grid energy which is actually hindering NEA in solving electrical load crisis. However this problem can be solved by integrating Pumped Storage Hydropower in electrical system. Pumped storage acts as large battery for storing electrical energy from grid during off-peak periods. And we can use this energy during peak demand for our daily activities and also use it in industrial sector.
Transcript
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1. Background
1.1 Project description:
Pumped storage hydroelectricity is a type of power generation used by some other power
plants for load balancing. It is only method of large scale electrical energy storage in
widespread use today. The basic concept is simple. Energy is stored as hydraulic potential
energy by pumping water from a low-level into a high-level reservoir. When recovery of
energy is required, the water is returned to the lower reservoir through turbines which drive
electrical generators. It helps on load balancing only. No extra energy is added, it only stores
electrical energy and provides it according to need.
However we don‟t have any extra or off-peak energy in our system during dry period but
during wet period we would have enough amount of energy to pump water. So seasonal
Pumped storage hydropower can be integrated in our system to cover the peak demand.
The energy used in pumping a volume „V‟ of water of density „ρ‟ and through a height „h‟
with a pumping efficiency „ηp‟
E1= (ρgh/3600* ηp) MWH……………………... (1)
The energy recoverable with a regeneration efficiency „ηg‟
E2= (ρgh * ηg /3600) MWH……………………. (2)
Where „g „is the acceleration due to gravity
Typically, the overall efficiency (E2/E1) = ηg * ηp; which is in the range 70-80 %
1.2 Description of problem:
Currently we are facing daily load shedding of 12 hours. To overcome this, we are using
inverters and other devices to store electrical energy for our household works. We are also
using petroleum products to run diesel plant and thermal plant. During the era of energy crisis
we are using non-renewable energy recklessly. But then this stored energy cannot be used to
run an industry or do other works which consumes huge amount of electrical energy. These
energy storing devices have become one of the major consumers of grid energy which is
actually hindering NEA in solving electrical load crisis. However this problem can be solved
by integrating Pumped Storage Hydropower in electrical system. Pumped storage acts as
large battery for storing electrical energy from grid during off-peak periods. And we can use
this energy during peak demand for our daily activities and also use it in industrial sector.
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Hence, this scheme will help in peaking capacity and also load balancing. Pumped storage
hydropower is environmental friendly as it is pollution free and is renewable source of
electricity.
1.3 Review of work already done:
Few works have already been done in this field. Students of Geomatics engineering have
done the bathymetry of Begnas and Rupa Lake. They have also prepared hypsography of
both the lake. A renowned organisation in the field of hydropower has also done study on the
feasibility of Pumped storage in Rupa and Begnas Lake.
1.4 Rationale for taking up the project
The enormous potential of Nepal in field of electrical power production is not hidden from
anyone. But it is our incompetency that we have not become able to extract the energy
according to our demand. The annual peak demand during the driest period i.e. on Jan 13 th
2012 is 1026.65 MW at 6:25 pm. And the current installed capacity of Nepal is 718.621 MW
but Nepal is supplying only 380 MW to 500 MW during dry period. Hence we are facing a
daily load-shedding of 12 hours.
But during wet season when we are producing 718.621 MW, we are still facing a daily load
shedding of 4 hours mainly during 7 a.m.-10 a.m. in morning and 5 p.m.-9 p.m. during
evening. According to load curve of Nepal we have enough off-peak energy which can be
used to overcome load shedding by installing Pumped storage hydropower in current
electrical system.
NEA is also commencing a 400 kV Dhalkebar- Muzzaffarpur double circuit cross border
transmission line to import 150 MW of electricity. Also there are number of hydropower
projects presently under construction both in the public sector as well as in the private sector.
Some are planned for implementation. With the commissioning of all those hydropower
projects, substantial surplus energy is expected to be available especially during the night
hours in the summer months. Then the pumped storage hydropower plant we are proposing
can run throughout the year.
The alluring topography and presence of two natural reservoirs in form of Begnas Lake and
Rupa Lake with net head of 50 m in 500 m horizontal stretch describes the need of project.
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2. Description of proposal
2.1 Objective of the project
The objectives of the project are as follows:
To calculate the inundation area in Rupa lake
To predict necessary methods for slope stabilization of Rupa lake shore
To determine the capacity of pumped storage hydropower in Rupa and Begnas lake
To design intake, dam and powerhouse for pumped storage hydropower
To perform the structural analysis of purposed dam
To find the transmission distance from powerhouse to nearest grid
To estimate the cost of different components of hydropower
To study the geology of site using geotechnical investigations
To design the cross-section of the tunnel
To conduct socio-economic survey at site
To predict environmental impact due to project implementation
2.2 International status and National status
Pump storage was first installed by manufacturing industries in Italy and Switzerland in the
1890s to enable them to store surplus night-time output from run-of-river hydro stations for
use in meeting their peak power requirements the following day. Japan, USA, Italy,
Germany, France and Spain are the world‟s leading countries in terms of installed capacity of
pumped storage projects, including those under construction.
For countries with topography and geological conditions suitable for pumped storage projects
sites, one measure of the extent of utilization of pumped storage capacity is the percentage of
the total electric capacity that is provided by the pumped storage.
Austria stands out as the country having the highest percentage of pumped storage capacity
on its electric system. Pumped storage provides approximately 17 percent of Austria‟s total
generation capacity. Austria is followed by Switzerland, Spain, Italy and Japan. Japan is far
ahead of all other countries in the advancement of pumped storage technology and its
utilization.
In context of Nepal we don‟t have any pumped storage hydropower in our electrical system.
But we have storage type of project which is used during peak demand i.e. Kulekhani-I & II
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2.3 Relevance of the project in Nepalese context
The peak power demand this year has increased by 8.5 % from previous year. The electricity
demand is increasing day-by-day and proportionally the peak is also increasing. But we know
that Nepal is not in a state of implementing large capacity hydropower for another 6 – 8
years. So we must choose another means to overcome the peaking problem. Until we have
enough off-peak energy during dry period; seasonal (i.e. during wet season) Pumped storage
hydropower seems to be feasible and cost effective in following ways:
We have naturally located reservoirs with a net head of 50 m
The distance between two lake/reservoirs is only 500 m
The geology of the area is suitable for construction of tunnel and powerhouse
There is constant inflow into Begnas lake
Begnas Lake will itself function as a surge tank so no need to construct a surge tank
The cost of the project will be reduced due to naturally available reservoirs
Peaking problem will be solved
The project will certainly boost the tourism of the area
2.4 Preliminary investigation done by institution
We presented on “PUMPED STORAGE AND ITS PROSPECTS IN NEPAL: A Case Study
of Rupa and Begnas lake” in project competition organised by Civil Engineering Students‟
Society Nepal (CESS-NEPAL), Institute of Engineering, Pulchowk Campus, Lalitpur.
Also students from Geomatics engineering have done bathymetric survey of both lake and
have produced hypsographic graph of both the lakes. This graph gives the relation between
depth and volume of water at that particular depth.
2.5 Review of the available expertise within the institution and host
organisation
S.N. Name Expertise Organisation
1. Prof. Dr. Ramesh Kumar Maskey Hydropower Kathmandu University
2. Dr. Chandra Prakash Poudel Geology Kathmandu University
