Load Management: Solutions for efficient handling of variable demand

Solutions for efficient handling of variable demand

Distribution utilities today need to meet power demand with efficiency and reliability. They need to address changing consumer demand at low cost and without losses, while maintaining power quality and availability. However, there are challenges in meeting this objective as demand is variable and depends on the user. It varies every moment while generation, except for renewable energy, is mostly fixed in nature. Therefore, distribution utilities have to meet variable demand with fixed and unpredictable generation.

Peak loads result in major expenditure for power utilities in the form of purchase of expensive short-term power and increase in distribution infrastructure requirements. This can be reduced or eliminated by transferring non-emergency power demand from peak hours to off-peak hours, or by using the energy stored at off-peak times during peak times. This can be achieved by means of real-time pricing of electricity, which encourages end-users to shift their consumption from peak hours to off-peak hours. This not only helps the utility to manage load, but also helps consumers to reduce their power bills. On the supply side, accurate power demand forecasts, load limiting based on consumer category and credit profile, selective load shedding, brownouts, etc. are a few critical techniques that can be applied to ensure optimal power supply.

BSES Rajdhani Power Limited (BRPL), which distributes power in south and west Delhi, has undertaken some novel initiatives for load management. Load management aids a utility in matching the power supply and demand requirements in a cost-efficient manner. The discom has also undertaken operational performance improvement initiatives, which aided in the reduction of aggregate technical and commercial losses from 53 per cent in 2002 to 12.7 per cent in 2015-16. BRPL is internationally recognised for its unique process of monthly consumer meter data electronic download and analytics. It is continuously working on ways to better manage its load in an efficient and reliable manner.  The subsequent sections discuss BRPL’s initiatives for load management.

Load research

Load research is the first and foremost step of load management. In order to meet power demand, either generation can be made variable as per the demand, which is a costly proposition, or utilities can engage with consumers to shift their demand. The latter approach is called demand-side management (DSM).

Load research helps determine the change in demand and consumption patterns over time to find out different patterns in energy use by consumers and ascertain the consumer segment/ appliance that contributes most to peak demand. In addition, load studies help in the identification of DSM programmes that need to be implemented by the utility.

BRPL load research methodology

BRPL conducts distribution transformer (DT) loading studies and consumer field surveys as part of its load research. DT loading studies are done using meter data that is generated at half-hourly intervals. It involves DT identification, category-wise segregation of DTs, data extraction, load curve analysis, peak load point evaluation, and segregation of peak on the basis of summer and winter.

Meanwhile, for consumer field surveys, an agency is roped in. Thereafter, 15 identified consumer categories are surveyed through a questionnaire on a sample size of 265 consumers per category. The sample size was suggested by the California-based Berkley Lab. It focuses on peak and off-peak load point evaluation, and analysis of peak load contributors for summer and winter.

Load research findings

BRPL’s load research findings were compiled by Energy Efficiency Services Limited’s (EESL) engineers. This was the first detailed research done by an Indian utility. Some of the key findings are as follows.

There are discrete peak time slots among different consumer categories. While air conditioners (ACs), lights, fans and refrigerators contribute to peak load in summer, geysers, lights, refrigerators and heaters contribute to the peak load in winter. There has been a high penetration of non-star-rated ACs and refrigerators on consumer premises. Also, consumers typically are unaware of the selection criteria for an AC. Often corrosion in the form of scaling develops on geysers, which reduces their efficiency.

Besides, old fluorescent tube lights with magnetic ballast are most common in the industrial category. Also, a large number of consumers uses the inefficient rewound motors. There is less awareness among consumers regarding star-rated and super-efficient fans, solar subsidy, power factor penalty, cost reduction of LEDs, etc.

DSM action plan

BRPL initiated schemes to promote the installation of LED bulbs, energy efficient ACs and fans, as well as introduced a demand response (DR) programme. These schemes had the potential to reduce load by up to 87 MW. The schemes for installation of energy efficient appliances entailed a total investment of about Rs 330 million, while the DR programme requires an investment of about Rs 12.5 million per year.

Besides, solar power helps the utility to meet peak demand, particularly rooftop solar that helps to reduce daytime peak demand. In this context, BRPL has worked with the Delhi government to install rooftop photovoltaic (PV) systems on office buildings where DTs are overloaded during the daytime. The total installed capacity of such systems is about 3.8 MW with over 200 installations. Also, BRPL is the first discom to have started net metering in Delhi for consumers with rooftop solar systems.

In addition, BRPL had planned to implement a DR programme with the objective of creating “negawatts” (a theoretical unit of power that represents the amount of power saved) at peak hours by curtailing energy usage. However, the programme is currently on hold as it directly affects high-end consumers, thereby impacting the discom’s revenue. It also does not encourage low-end consumers, who form the majority in the consumer mix.

The way forward

Going forward, BRPL is planning to implement the Behavioural Energy Efficiency Program with the objective of optimising the demand curve by engaging consumers. This is a unique programme that will be implemented for the first time in the country. The discom is currently working on a project on behavioural energy efficiency with US-based OPOWER and ORACLE. This programme will provide select residential consumers with personalised home energy reports (HERs) and an integrated web portal. The programme is targeted towards 200,000 domestic consumers including lower-end consumers. HERs will encourage consumers to save 2-3 per cent of their electricity consumption with more savings during peak hours. This 18-month pilot project will demonstrate reductions in energy wastage and peak-hourly consumption, and improve customer engagement. The project is being funded through a $700,000-$1 million grant from the US Trade and Development Agency.

Besides, BRPL is exploring the possibility of using battery storage systems to manage peak demand. In this context, it plans to deploy a megawatt-hour battery on a trolley that would be charged during the night and can be parked near a critical load centre, say, a hospital. The battery can help meet the peak requirements of the hospital during the daytime.

With inputs from a presentation by Rajesh Bansal, Senior Vice-President, BSES, at a recent Power Line conference