Distributed pumped hydro storage – a case study.

Abstract

With large penetration of solar power, the intermittency of solar irradiance affects the stability of the power system. This can only be tackled through energy storage. India has identified PHP as major option (India Smart Grid Forum, Energy Storage System - Roadmap for India: 2019-2032) for storage of excess solar/ wind generation. However, centralised PHP, has got inherent disadvantage of geographical distance from distributed solar energy hubs and load centres. Distributed pumped water storage systems can be a dependable option considering the endowment of India with numerous perennial streams geographically distributed. This paper presents a pilot case of an integrated small solar – pump hydro project, consistently providing power to 350 people in a remote village at the northern part of the country. This paper has also discussed a cooperative approach for promoting such small storage infrastructure. The purpose of this paper is to showcase opportunity in a niche area like distributed storage and advocacy for developing enabling legislations in this direction.

Key words: Distributed storage, policy on energy storage, integrated solar pump hydro storage.

1. Introduction

As of February 2023, Solar power installed capacity has reached to a figure of 64.4 GW. During the peak generation of these solar utilities, the vulnerability of the power system stability is observed with reduction/short shutdown of conventional electromechanical generators to manage the net demand of the system. The net ramp rate requirement exceeds 25 GW/hour (Mohit Joshi, Saif Rehman etal(2020)). During evening peak, the system ramp rate can be to the tune of 32 GW/hour (Mohit Joshi, Saif Rehman etal(2020)). With enhance solar penetration it is estimated that local ramp rate can be worse to the tune of 37 GW (David Palchak, etal (2017)). Over and above, inadvertent curtailment of solar energy is taking place for managing the system stability. As reported in Greening the Grid (David Palchak, etal (2017))the estimated curtailment with 100 GW solar and 60 GW wind is around 1.4%. To combat the situation India needs storage to the tune of 27 GW/ 108 GWH (Report on optimal generation capacity mix for 2029-30, CEA, 2020). Presently the operating storage capacity in India is 4.74 GW in PHS (working in storage mode is 3.3 GW) and 20 MW in BES. Around 40 MW of BSS under procurement and 2.7 GW of PHS under construction. The target of 27 GW is far away from the reality. One of the reasons is high cost of BSS and long gestation period of PHS. Centralise large storage requires substantial funding as well as land and space for accommodating the storage units.

Distributed energy storage of small capacity spread all over the country, interconnected at distribution voltage level with multiple types of energy storage may be a better solution for the country to address the huge energy storage requirement. The distributed storage is more flexible, and compared to centralized storage, it reduces the financial pressure and maintenance costs required to build large storage systems. Reasonable planning of distributed energy storage in power network and its coordinated operation with distributed power sources and loads, improves power network security and economic operation.

Cooperative-driven energy transition

Creation of such distributed storage may not attract big industry houses for investment because of its small size and very low profit associated with it. It requires involvement of local people with small business opportunity and financial support. Surveys show that the acceptance of energy projects in people’s front yards/neighbourhood increases when they are considered part of one’s own local living environment. Financial advantages through alternative livelihood resulting from the energy infrastructure led to an increase in acceptance. A cooperative in which members come together to implement energy projects that could not be managed by single entity, makes this possible. They are democratic model organisations promote the economic development of all members equally.

The structure of this paper is as follows: In section two, the case of pumped hydro storage is described. Data is collected from the NGOs involved in this endeavour. In section three the impacts on lifestyle of the people through this energy adoption are discussed. Section four has developed a levelized cost of energy storage model for this Hengbung storage initiatives. Proposal for cooperative structure for energy storage and its advantage is discussed in section five. In section six concluding statements are made while providing the directions for further research.

2. Integrated solar-pumped hydro project at Hengbung

Hengbung village is in Sadar Hills West subdivision of Senapati district in Manipur, India. It is situated 16km away from sub-district headquarter Kangpokpi (tehsildar office) and 35km away from district headquarter Senapati. Hengbung has a total population of 1,226 peoples.

Foundation for Environment and Economic Development Services (FEEDS) in collaboration with NB Institute of Rural Technology (NBRIT) and Visva-Bharati University initiated the pilot project on integrated solar-pumped hydro system at Hengbung during 2019. A small stream Sasan is flowing near the village. Two manmade reservoirs having a head difference of 4.5 meters with a collective capacity of 19 lakh litters were constructed with local resource to act as a giant water battery. The upper reservoir draws water from the stream directly.  A 12 KW propeller turbine alternator was installed to generate hydropower through this 4.5-meter water head for supplying electricity during night times.

A system of 40 KW solar PV is installed in the village, which provides lighting to 50 households (around 350 people) during daytime and the excess solar power generated is used for pumping back water from the lower reservoir to the upper reservoir making it ready for supplying of household light as well as lighting of 84 numbers of streetlights during night times. Pumping back is done through 4 numbers of 10 HP pumps installed at lower reservoir. The solar PV system can generate around 53 KWh/ day. The household and streetlight consume around 10 KWh (presently each household has been provided with a 9 W LED and streetlights with 12 W LED each). There is excess energy available from the PV system which can be sold back to local discoms. Discussion is going on with Manipur State Power Distribution Company for finalising the buying back rate of excess solar generation during the daytime. This will give a revenue generation for this integrated solar-pumped storage system.

Construction of the reservoir, installations of Pumps, PV system were completed by FEEDS with the unskilled support from the local villager and skilled support from Amogha group, Bangalore. Funding for the micro hydel part is provided by Government of India through Science for Equity Empowerment and Development (SEED) division. Solar PV system is funded by NBRIT. A brief detail of the integrated plant is given in Table below.

Table : Details of the Micro hydel installation

3. Impact on lifestyle and livelihood

The Hengnbung project has piloted a sustainable energy transition at a remote location in the country. Residents feel that the system has provided light in their residence and the streets during night-time. The project also fetches daily wage work to the villagers during construction and repairing the installations. Regarding improvement in lifestyle, quote of a resident village is captured as follows:

“The system is in our hands now; we can run and maintain it ourselves,” said Romi Rai, a 32-year-old who makes a living farming poultry. Rai and his wife Jeena said the system had improved their family life by giving her light to do stitching and household chores more hours of the day and helping their 6-year-old son do his homework without worrying about the lights going out. It will take more time to assess the long-term impact.

Street lights through the solar-driven pumped storage hydropower project in the Hengbung village of Manipur. Courtesy: FEED

4. Levelized cost modelling of the storage at Hingbung.

A storage cost modelling has been developed to understand the levelized cost of such storage facility. The levelized cost for the system over a period of 40 years is estimated around Rs. 2632/MW (Approximately USD 31/MW). The cost is much cheaper compared to Battery storage cost. Numbers of such types of energy storage at local village level (wherever perennial water streams are available nearby) can significantly augment the energy storage requirement of the country at low cost.        

5. Cooperative driven approach for Indian renewable development.

Cooperatives formed locally to augment rural electricity access is not new. In many regions of the world, Electricity cooperatives are leading the way in the use of new and renewable energies and contribute to the sustainable management of natural resources in several ways. In India though successful cooperative models are operating in Diary products, banking etc., but till now electric cooperative are at the nascent stage. Few community driven energy initiatives like Solar Pump Irrigators’ Cooperative Enterprise (SPICE) at Dhundi village, Gujrat and solar power community project at Baripatha, Odisha, are showing that community owned renewable project can be sustainable over a long time. India needs enabling legislations and handholding organisations at the state level to promote Electric cooperative at rural level. The cooperative movement can uplift the renewable energy scenario of the country.

6. Conclusion

Customer awareness and citizen involvement are minimal in India and India’s solar revolution not yet included its citizens in India’s energy transition. Unless more citizens are involved in India’s renewable energy revolution, wholistic development in renewable energy may not be sustainable. There can be many businesses model for sustainability of community driven storage models. Cooperative approach may help in arranging necessary funds and create employment opportunity at local level.

Further study should be conducted for estimation of potentials for such distributed pumped storage system and system stabilities on distributed storage.

References

1. India Smart Grid Forum, Energy Storage System - Roadmap for India: 2019-2032, August, 2019
2. Mohit Joshi, Saif Rehman etal, RAMPING UP THE RAMPING CAPABILITY India’s Power System Transition -, Greening the Grid (GTG) USAID/India, NREL report, September 2020.
3. David Palchak, Jaquelin Cochran, etal, GREENING THE GRID: Pathways to Integrate 175 Gigawatts of Renewable Energy into India’s Electric Grid, Vol. I—National Study, NREL report, Jun 2017.
4. Report on optimal generation capacity mix for 2029-30, CEA, 2020.
5. Olivier Pacot, Shadya Martignoni, Laurent Smati, Vincent Denis & Cécile Münch-Alligné (2022): Case studies of small, pumped storage, LHB, https://doi.org/10.1080/27678490.2022.2101392
6. Tri-Annual Report, 2015-18, Dhundi solar energy producers’ cooperative society, Dec, 2018
7. Annabel Yadoo n, Heather Cruickshank, The value of cooperatives in rural electrification, Energy Policy (2010), doi:10.1016/j.enpol.2010.01.031
8. Duvall, Whitney Prather, "The Evolving Role of Electric Cooperatives in Economic Development: A Case
9. Study of Owen Electric Cooperative and Jackson Energy Cooperative" (2016). Theses and Dissertations-- Community & Leadership Development. https://uknowledge.uky.edu/cld_etds/20
10. Peng Ye 1, Siqi Liu, Feng Sun , Mingli Zhang and Na Zhang, Overview and Prospect of distributed energy storage technology, E3S Web of Conferences 257, 01011 (2021), AESEE 2021. https://doi.org/10.1051/e3sconf/202125701011