Vengikkal, the second-largest panchayat in Tamil Nadu by land area, hosts a significant number of government offices and is a hub for devotees visiting Annamalaiyar Hill. Home to 26,713 residents across 8,341 households, Vengikkal faces significant challenges in managing the energy-intensive public water supply system. Operating 19 electricity service connections for water pumps, the panchayat consumes 5 lakh units of electricity annually, costing ₹42 lakhs in electricity bills. Vengikkal panchayat has an outstanding debt of ₹1.4 crore to TANGEDCO. This mirrors a statewide issue, with local bodies collectively owing ₹5,069 crore for public utilities as of August 2024. Addressing energy inefficiencies is critical for financial sustainability. This article outlines findings from an energy audit conducted by the Citizen Consumer and Civic Action Group (CAG) under the project "Accelerating Clean Energy Transition by Improving Stakeholder Participation for Electricity Governance in India." The study evaluates water supply operations, consumption patterns, energy use, and solutions for efficiency improvements in Vengikkal panchayat.
Public Water Supply System Overview
Vengikkal’s water supply infrastructure includes 20 multi-stage submersible pumps, each equipped with 7.5 HP motors, delivering water to 20 overhead tanks (OHTs) located at different habitations of Vengikkal. Most pumps draw water from borewells or open wells near Vengikkal and Iyyapa Nagar Lakes. While the pumps are located close to lakes, the OHTs are situated in the residential areas. Thus the pumps are required to transport water to distances as long as 4 to 5 kms. Each OHT is overseen by a dedicated pump operator, who is responsible for switching on/off the pumps, its maintenance, and ensuring proper, efficient and uninterrupted functioning of the entire water distribution system. Currently, only 16 pumps are operational, and these are supplying all 20 OHTs. It was understood that the majority of the pumps have outlived their lifetime and are due for replacement. The performance of these pumps is therefore not optimal.
Figure 1 : Components in public water supply system : Open well with submersible water pump, OHT, Pump operating room, EB meter
Figure 2 : Location of pumps and OHTs in Vengikkal Panchayat | CAG
Fig 2 : Water Supply Layout : O H T | CAG
Water Consumption Patterns
There are 20 OHTs supplying water to various habitations in Vengikkal. The OHTs are filled and emptied twice per day. The OHT capacity varies from 30,000 litres to 1 lakh litres. The size of the OHT tank is determined based on the area it is serving water. It takes around 4 to 5 hours to fill the OHT tank. Thus the pumps supplying water to OHT run 10 to 12 hours per day ( tanks are filled twice daily ). Water distribution is close to 1.9 to 2.0 million litres per day for 8,341 households for a population of 26,713. The per capita water consumption is estimated as 70 litres per day which is quite reasonable.
Energy Consumption and Costs
The 20 pumps collectively consume 4.81 lakh kWh annually, incurring costs of ₹42 lakhs. Each pump consumes an average of 30,000 units annually, and the corresponding energy bill is approximately ₹3 lakhs per pump. The connections fall under the LM2A tariff category, with an energy rate of ₹8.55 / kWh and fixed charges of ₹214 / kW bi-monthly. Variations in energy consumption stem from differences in pump age, rewinding frequency, and water table depth.
Proposed Strategies for Energy Efficiency
- Surrender Inactive Connections:
Four non-functional service connections incur fixed charges despite being unused. Surrendering these connections would save ₹43,656 annually. - Optimize Contract Demand:
Three connections have contracted demands significantly exceeding usage. Adjusting these would save ₹23,112 annually in fixed charges. - Upgrade Inefficient Pumps:
Nine pumps consume more energy than their rated capacity due to age and poor maintenance. Replacing the most inefficient pumps with energy-efficient models could save 69,550 kWh annually, translating to ₹5.94 lakhs in savings. - Implement IoT-Based Water Management:
IoT systems can automate pump operations and monitor water levels, preventing overflows and dry runs. Implementing this technology could save 2 lakh units of electricity annually, reducing costs by ₹17 lakhs.
Fig 7 : Layout of IoT based Water Management System for the OHTs | CAG
Conclusion
In Vengikkal 1.8 to 2 million litres of water per day is distributed through OHTs to a population of 26 713 serving 8341 households. The total energy consumption for pumping is around 4.8 lakhs kWh / y and corresponding energy bill paid is ₹ 42 lakhs / y. Per capita water consumption is 70 litres per day and per capita energy consumption for water supply is 18 kWh / y and corresponding per capita energy bill for water pumping is ₹ 156 / y. The overall average energy cost is estimated as ₹ 500 / y / HH which is notably higher than the water tax of ₹ 360 / y / HH collected. 4 energy and cost saving proposals have been identified with an objective of optimizing / minimizing the energy consumption and energy bill. Implementation of these energy saving proposals is expected to result in
(i) reduction in contract demand of about 50 kW
(ii) savings of about 2.5 lakh kWh / y in present energy consumption
(iii) monetary benefits of ₹ 23 lakhs / y on energy bills
(iv) reduction in CO2 emission by 180 tons / y
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