Article

Andhi Khola Pumped storage Scheme in the context of Nepal 2021

May 8, 2021

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(A financially feasible proposal “Andhi Khola Dam with Separate Pump & Generation Stations Scheme together with existing Kali Gandaki ‘A’ Hydro power plant” in the context of Stabilizing the National Grid on a daily and annual basis.)

Introduction

It is imperative to think of implementation of Pumped Storage Schemes in Nepal to stabilize the National Electricity Grid. The justification for such a need being:

To stabilize National Grid in response to:
- Variation in demand both on a daily and annual basis.
- Variation in supply both on a daily and annual basis due to hydrology. (as most schemes are run of river in the country.)
- Increasing availability of power in the grid, especially when there is spike in demand.
To reduce import of electricity at peak hours.
To reduce operation of storage schemes at peak hours.
To accommodate other renewable resources like solar and wind.

To address the above, we propose Andhi Khola Pumped storage Dam with separate pumping station and generating station scheme. In this case, existing Kali Gandaki ‘A’ Hydro power plant (3 units), proposed pumping station (4 units – subject to finalize later) and proposed generating station (4units – subject to finalize later) can be run in different modes of operation as per requirement to stabilize the grid as shown on schematic diagram below:

These sequential modes of operations when there is excess of energy in the grid can be as follows:

Shut down of 1^st unit of existing Kali Gandaki ‘A’ Hydro power plant.
Shut down of 2^nd unit of existing Kali Gandaki ‘A’ Hydro power plant.
Shut down of 3^rd unit of existing Kali Gandaki ‘A’ Hydro power plant.
Operation of 1^st unit of proposed pumping station.
Operation of 2^nd unit of proposed pumping station.
Operation of 3^rd unit of proposed pumping station.
Operation of 4^th unit of proposed pumping station.

Similarly, in case of power demand in the grid, the following sequential modes of operation can be performed:

Operation of 1^st unit of proposed generating station.
Operation of 2^nd unit of proposed generating station.
Operation of 3^rd unit of proposed generating station.
Operation of 4^th unit of proposed generating station.
Operation of 1st unit of existing Kali Gandaki ‘A’ Hydro power plant.
Operation of 2nd unit of existing Kali Gandaki ‘A’ Hydro power plant.
Operation of 3rd unit of existing Kali Gandaki ‘A’ Hydro power plant.

Description of Existing hydro power plants nearby

There are two existing hydro power plants nearby this scheme.

The first one is Kali Gandaki ‘A’ hydro power plant, which is described in operation modes as stated above. The installed capacity of the plant is 144 MW with daily peaking scheme with the two sources of Kali Gandaki river and Andhi Khola river. The dam is located around 40m downstream at the confluence of the rivers with coordinates 27.979144° N and 83.58041° E. The powerhouse is located downstream of the dam with coordinates 27.930970° N and 83.615046° E. Reference 1.

The second one is Andhi Khola Hydro power plant with installed capacity 9.4 MW. Dam of the Andhi Khola Hydro power plant is located around 13 km upstream of proposed dam with coordinates 27.949602° N and 83.679156° E. The proposed scheme does not interfere the Andhi Khola Hydro power Plant in its operation by any means.

The two existing plants, proposed Dam with Pumping station and proposed Generation Station all are located at Syangja District, Gandaki State, Nepal. Reference 3.

Nature of Existing Electricity Demand and Supply

As per “System Load Curve for a day September 09, 2019 – wet period” as shown below, there was peak (maximum) load 1407.94 MW around 19:00 Hours and minimum load was around 1050 MW around 06:00 Hours. Statistics & Schematics, System Load Curve, A Year in Review – Fiscal Year 2019/20, Nepal Electricity Authority. Reference 4.

(Abbreviation : NEA – Nepal Electricity Authority; ROR – Run of River; PROR – Peak ROR; DM Import – Dhalkebar-Mujaffarpur international transmission link Import (between Nepal and India); Tanakpur Import – international transmission link Import (between Nepal and India); Total IPP – Total Independent Power Producer.)

Similarly, as per “System Load Curve for a day January 12, 2020 – dry period” as shown below, there was a peak (maximum) load 1374.90 MW around 18:00 Hours and minimum load was nearly 700 MW around 06:00 Hours. System Load Curve, A Year in Review – Fiscal Year 2019/20, Nepal Electricity Authority. Reference 4.

In both the above cases, sources of electricity are Nepal Electricity Authority Run of River HPP (NEA ROR), Independent Power Producer HPP (IPP), Imports from India (Tanakpur import, DM import and other import) and Storage HPP (NEA). Peak to off peak ratio is around 2 in dry season, which shows many NEA ROR HPP were running in low power or shut down due to less demand. We can thus infer that there is a huge amount of spill energy in dry season compared to wet season by shutting down NEA ROR Plants during 23:00 to 5:30 hours. This spill energy could be utilized to pump the water in purposed scheme to increase the Plant factor of NEA ROR Plants.

To address the deficit in power at peak usage, the country is planning to go solar by adding solar panels and connecting them to the grid. This further makes the case of Pumped storage Scheme all the more relevant and required. As per Reference 5, “GRID SOLAR AND ENERGY EFFICIENCY PROJECT (GSEEP), Environmental and Social Management Framework, June 2014”, Average solar radiation varies from 3.6 to 6.2 kWh/m2 per day in Nepal; while the total sun shines days is about 300 per year. The GSEEP development objectives are to:

increase generation capacity to supply the NEA grid through grid-connected solar farms; and
reduce NEA’s distribution losses in pilot distribution centers. The implementing agency for the GSEEP will be NEA.

Recently in June 05, 2020; NEA has added 1.25 megawatts, solar project in Nuwakot to the national grid system. With this latest development, the 25 MW project has formally come into operation from today. The electricity generated by the solar project has been connected to the substation at Devighat HPP in Trishuli of Nuwakot district. The generated solar electricity is directly connected to the national grid. As there is no battery in the solar project, generated electricity during the day time will run the risk of not being used while in the evenings, the problem of peak electricity demand would still not be addressed. The Pumped storage project is the best option that solves solar power demand issue as well.

Rationale of the Proposed Scheme

Considering all situations as described above, a dam around 100 m high with Pumping Station at upstream of existing Kali Gandaki ‘A’ Hydro power plant Reservoir and a generation station near existing Kali Gandaki ‘A” HPP can be proposed in Andhi Khola as shown in figure below:

The existing systems are shown on the figure above with yellow pin as described below:

Left up – Existing Kali Gandaki ‘A’ HPP Dam and Reservoir
Right middle – Existing Andhi Khola HPP Dam (ROR Scheme of IPP)
Left below – Existing Kali Gandaki ‘A’ HPP Powerhouse with 3 units

Similarly, for the proposed structure are as described below:

Left up near Existing Kali Gandaki ‘A’ HPP Dam and Reservoir – 100 m High Dam
Toe of the proposed 100 m High Dam – 200 MW Pumping Station with 4 units
Left below near Existing Kali Gandaki ‘A’ HPP Powerhouse – 200 MW Generating Station with 4 units
Left up to Right middle – Reservoir with 120 million cubic meter Live storage Capacity (20 m) and around 13 km long

The specifications of the proposed stations and structures as described above are subject to confirmation upon detailed feasibility reports.

One of the key benefits of this scheme is that there will be any or little environmental and social impact. Relocation will be very nominal. The scheme does not hamper any existing plants. Existing Andhi Khola Hydro power plant will not be affected by this scheme. Whereas Kali Gandaki ‘A’ Hydropower Plant (HPP) will be a part of the scheme to stabilize the grid. As per the proposed scheme the live storage will be around 120 Million Cubic meter considering top 20 m height as live storage and 13 km back water along the river at maximum.

This scheme along with existing Kali Gandaki ‘A’ Hydro power plant, Maximum 344 MW can be drawn from the grid during the surplus power in the grid. 144 MW by shutting down the existing Kali Gandaki ‘A’ HPP and 200 MW drawing the power from the grid by Proposed Pumping Station. Similarly, whereas maximum 344 MW can be harnessed and supply to the grid in peak demand. 144 MW by generating the existing Kali Gandaki ‘A’ HPP and generating 200 MW by Proposed Generating Station. In this way, Maximum 688 MW (-344 to +344 MW) can be managed to make the grid stable. Further, these days Grid Tied Solar Power Projects are being welcomed by the Government is encouraging. The power harnessed by Solar can be utilized to pump the water in case of surplus in the grid. More and more Grid Tied Solar Power Projects can be encouraged without burden to the concerned authority ranging few Watts to Megawatts.

Furthermore, Pumped Storage is financially viable because of the following engineering reasons:

Pumping Head Maximum by proposed pumping station is around 100 m only.
Generation Head Maximum by proposed generating station is around 250 m.
Generation to Pumping in terms of energy is almost Double considering all losses and efficiencies. This is one of the key features of the proposed scheme.

Conclusion:

The proposed Pumped Storage Scheme of Andhi Khola Dam with Separate Pump & Generation Stations Scheme together with existing Kali Gandaki ‘A’ Hydro power plant is feasible financially and in foundational engineering terms. The storage scheme is predicted to double the power generation with this scheme.

Electricity from alternative energy sources like Solar and even wind can be used in the Pumped Storage scheme to eliminate the requirement of battery and to address peak energy demand in the country.

Reference:

Kaligandaki A Hydroelectric Power Station. (February 08, 2020). Retrieved January 26, 2021, from https://en.wikipedia.org/wiki/Kaligandaki_A_Hydroelectric_Power_Station
Andhikhola Hydropower Plant. Retrieved July 10, 2020, from https://bpc.com.np/electricity-generation/128-andhikhola-hydropower-plant
Syangja District. (January 19, 2021). Retrieved January 26, 2021, from https://en.wikipedia.org/wiki/Syangja_District
“A Year in Review – Fiscal Year 2019/2020, Nepal Electricity Authority. Retrieved January 26, 2021, from https://nea.org.np/admin/assets/uploads/annual_publications/Annual_book_2077.pdf
Grid Solar and Energy Efficiency Project – June 2014. Retrieved July 10, 2020, from https://www.nea.org.np/admin/assets/uploads/supportive_docs/Environmental%20and%20Social%20%20Management%20Framework_Final%20June%2018_complete%20with%20annex.pdf
NEA adds 1.5MW solar power to national grid. (June 5, 2020). Retrieved 10 July, 2020, from http://www.nepalenergyforum.com/nea-adds-1-5mw-solar-power-to-national-grid/

Article by :

Raju Shrestha

Mechanical engineer – Hydropower, in the field academic, industry and project management representing institute, client, contractor and consultant. Involved in various projects and plants related to hydropower, water supply, water treatment, flood control and waste water treatment for study, component / system design & drawing, project development, rehabilitation and research in Nepal, Norway, Namibia, Kuwait, China, Afghanistan, Tanzania, Egypt, India and Sri Lanka after my bachelor in mechanical engineering in 1998. Latest qualification is Master of Science by research on hydraulic turbine performance – Mechanical engineering.