Price escalation of energy, in any of its form, as has been a regular feature in recent years, exerts unfavourable impact on techno-socio scenario of our country.

The very rise in cost of energy, the basic ingredient of industrial production, disturbs the economics in users’ establishment in a significant way and calls for corrective measures to mitigate its adverse impact.

In a situation such as this, relevance of efficient energy management is obvious to plug in energy waste. Accordingly, identification of the poor operating areas responsible for unreasonable rise in energy index in a set-up deserves priority to make out a right strategy for energy conservation.

On top of that, the performance of Supply Utility operating under watchful cover of State Electricity Regulatory Commission obviously comes in because of its direct bearing on the success of any conservation measure in consumers’ set-up. Again, the scale of charges of tariff and associated regulations also hold relevance on cost saving on electricity account.

In this article, an attempt has been made to bring out the desired corrective measures to look up to a favourable electricity consumption index in an environment of rising electricity cost and unpredictable supply source, especially in cold storages.

Load Management

Load management in consumer’s establishment, connected to supply system of Distribution Licensee, involves reduction of load demand and consumption of electrical energy for the task under specific operational parameters. Here, the matter of availability of quality supply source is important. The issue holds pertinence since success of end-use conservation measures is directly linked thereto.

Accordingly, fluctuation of supply voltage and frequency beyond the permissible limits, for obvious reasons, is not a pleasing state of affairs for consumers since it affects directly the operating performance of facilities. The outcome makes the consumer unhappy for holding back the benefit of his energy conservation measures.

Further, unplanned interruption of supply is equally embarrassing for consumers since it upsets the operational continuity of electricity driven facilities and requiring support of stand-by captive source to re-commence operation.

Load Survey

For implementation of an energy conservation scheme, the accepted practice relies on information about usages of electrical energy for a considered analysis thereof. Such data over a period of one month, so also over a year, would demonstrate the profile of two tariff components of electrical energy usage. The study also reveals the weak areas of energy use and helps planning out an effective energy conservation scheme for the set-up. The measure would, as management consultants feel, lead to reduction of maximum demand and electricity consumption index as well.

Load Management in Cold Storages       

In West Bengal there are about 390 cold storages for potato storage. They consume a considerable quantum of electrical energy primarily from supply source of the West Bengal State Electricity Distribution Company Limited (WBSEDCL). All these units receive the supply at 11 kV. Thereafter, it is transformed down to utility voltage of 415 V with the aid of a distribution transformer rated 11 / 0.415 kV.

Energy conservation in a cold storage, an electricity dependent rural industrial set-up, alike other industrial counterparts, recognises efficient end-use of load as the key factor to accomplish saving of electrical energy. Thus, an electrical conservation scheme is, in practice, drawn up by considering availability of constant supply of power at rated voltage and frequency. In reality, it is very seldom occurs in well spread out rural network of WBSEDCL operating under regularity control of a statutorily constituted the West Bengal Electricity Regulatory Commission.

Understandably, poor quality of prime supply cannot guarantee anticipated success of electrical energy saving schemes by users of electrical energy. Sadly, in West Bengal, such problem prevails and consumers suffer thereby since decrease in illumination output from lamps, drop off speed of fans and reduction in operating efficiency of electricity driven equipment occur at a voltage lower than the rated one.

The West Bengal Electricity Regulatory Commission

The West Bengal Electricity Regulatory Commission, constituted in accordance with section 82 of the Electricity Act, 2003, takes care matters relating to quality supply in its (Electricity Supply Code) Regulations, 2013 (Ref. Notification No. 55/WBERC dated 07.08.13). The provision lays down fluctuation limits for supply voltage and frequency. In respect of HT supply, it is set at 6% on higher side and 9% on lower side of the rated supply voltage. However, for medium voltage supply it is 6%. However, a variation of supply frequency between 50.5 Hz and 49.5 Hz is permissible.

In fact, at far flank rural areas, where most of cold storages are located, as of now, availability of constant supply of electricity at rated voltage from WBSEDCL, particularly during loading period, does not appear to be encouraging (Table 1). Occasionally, abnormally low supply voltage, particularly during evening hours, affects performance of electricity driven facilities. The graphs below show the profile of supply voltage recorded over the day in a cold storage located in the district of Hooghly, West Bengal. Graphs 1 and 2 not only endorse the above observation but also demonstrate its persistence.

Table 1

Ref.: Tunu Cold Storage, West Bengal.

Importantly, fluctuation of supply voltage beyond permissible limit is regarded as a situation not in keeping with clause 10 (1) of WBERC (Standards of Performance of Distribution Licensees Relating to Consumer Services) Regulations, 2010. The provision speaks of corrective action by the Supply Utilities within a set time-limit. Any default thereof has also been taken care of under compensation clause of the said Regulations.

* Graph 1

Again, unplanned short-time interruptions of supply, too, create similar situations of abnormality in cold storages, even worse than utility voltage fluctuation, since for every supply-outage the operation of refrigeration plant would remain on hold for nearly half an hour for switching over to standby supply mode and switching back again on restoration of power supply. The situation, particularly during potato loading months in March and April, tends to disturb the set environment in cold rooms requiring immediate support of stand-by supply to commence operation of the plant and, in turn, adds to the cost of electrical energy.

Accordingly, such recurrent short-time black out of supply is not a welcome situation for service users of electrical energy.

* Courtesy of Gautam Nayek of Tunu Cold Storage

* Graph 2

The WBERC, in clause 9(1) under Notification No. 46/ WBERC dated 31.05.10, also takes care of the issue relating to unplanned interruptions of supply. The above provision does not uphold such lapse except under circumstances of unforeseen contingencies, such as natural calamities, grid failure etc. Despite that, in reality, supply outage occurs, even more frequently in loading months in remotely located cold storage establishments in West Bengal, while onus of maintenance of power supply at rated voltage free from unplanned interruption vests in the supply utility as per agreement.

Tariff vis-à-vis Electricity Cost Index

Cost-analysis of energy conservation scheme in an establishment, be it industrial or commercial, has been the practice to quantify the probable economic success thereof.

Accordingly, economics in energy conservation measures, with short-time pay- back period, in rural electricity intensive cold storage establishments has been the subject of the study. Importantly, the scales of charges of the applicable electricity tariff and quality supply source too come under ambit of scrutiny.

However, to gauge financial impact of applicable tariff structure of the Supplier on an energy conservation scheme at the premises of cold storage consumers, mostly located far flank rural areas, an insight into the unique operating features of cold storages, as mentioned below, would be supportive.

Depending upon usage of electrical energy the operating period of the cold storages, inter alia storing potatoes is markedly divided into four parts. They are loading, holding, unloading and lean periods. The operating characteristics of cold storages having been different over different time-slots, the load demand to run the plant varies accordingly. It is highest during loading period, but it comes down appreciably in subsequent holding and unloading periods. However, the requirement of power during the lean period, generally extending over three months from December, when the refrigeration plant remains non-operational, becomes negligible.

The WBERC, in exercise of its authority under Section 86 and Section 62(1) of the Electricity Act 2003, annually takes up revision of electricity tariff for Distribution Licensees operating in West Bengal. The one for the year 2017-18, as has been reported by the news media, would come about shortly. Because of rise in overall operating cost of Distribution Licensees, the tariff hike is a certainty, and electricity would be more expensive for consumers, be it industrial, commercial or domestic, in the coming year. In such a situation, economies in respect of electrical energy conservation measures would expectedly differ according to change in the electricity tariff structure of the Supply Utility.

Graph 3

For cold storage consumers, adopting refrigerated storing of potatoes, the prevailing electricity tariff of WBSEDCL prescribes a season-related two-part scale of charges with TOD (time-of day) option. One part of two-part tariff is linked to kWh consumed and the other on amount of maximum demand in kVA recorded during the billing period. However, in respect of maximum kVA demand charge, contract demand-based levy, with a minimum of 85% of the contract demand, would be applicable in terms of Tariff Regulations of WBERC (clause 4.3.5 of WBERC Notification No. 48 dated 25.04.11 refers). Besides that, power drawl in excess of contract demand too would attract penal levy. It is felt that the method of levy of contract-demand-linked demand charge is a worrying situation for cold storage consumers financially because of seasonal nature of working of the establishments. The profile of monthly electricity cost index over the year, as reflected from the Graph 3, supports the above contention. Notably, the electricity cost index in lean months, when the refrigeration plant remains out of operation, is the highest owing to contributory impact of minimum demand charge factor of the tariff on kWh consumed. Abnormal rise in effective per unit cost of electricity in December, January and February, as demonstrated also in Graph 3, was all due to contributory impact of demand charge on lesser number of units (kWh) consumed.

In the circumstances, there is every reasonableness in exempting cold storage consumers from the purview of the minimum demand charge clause of the Tariff Rules of WBERC because of seasonable nature of electrical energy usage. Hence, the matter, as one feels, bears the merit for consideration afresh by the Commission to safeguard the interest of seasonal cold storage consumers {Section 61(d) of the Electricity Act, 2003 refers}.

Again, in TOD scale of charges, cost of per unit of electricity usage differs at different time-slots of day. It is minimum in off-peak slot, whereas highest in peak period. Therefore, to achieve a favourable electricity cost index with regard to usage of electricity, the off- peak period should receive preference over other two time-slots. Accordingly, operating practices of refrigeration plant, prime electricity consuming facility in a cold storage, need evaluation in reference to the Tariff structure for cost benefit.

Besides that, the Tarff includes levy, as rebate/surcharge depending on value of power factor, and other miscellaneous charges. Two different modes of charges, as given in Table 2 and 3, provide scopes for analysing the favourable features thereof.

Short-term electrical conservation scheme

For a short-term energy saving scheme in cold storages the following measures are usually considered:

Corrective measures involving little or no capital expenditure to minimize cooling load, namely heat given off by heat producing equipment located inside the refrigerated space, and warm air venting into the refrigerated space through open doors, particularly during potato loading and unloading period.

Modification in operating practices of the plant with reference to the supplier’s tariff structure.

Energy Audit

Since energy audit is regarded as a logical step to identify the weak areas of energy-use requiring corrective action to translate energy conservation ideas into realities, the mechanism is being practiced for comprehensive energy saving scheme for the establishment. On top of that it also quantifies energy usage by the facilities according to their discrete functions. Accordingly, energy audit even those remotely located units holds relevance to get their energy performance index improved. Primarily there are two main operating expenses in cold storages, namely electricity and labour.

Presently, in most of cold storages in West Bengal, mechanised lift-loading system is resorted to minimise labour-dependence on loading and unloading of potatoes. Such modification has since become popular because of its cost saving feature.

It is also believed that availability of constant quality supply source and favourable electricity Tariff structure are prerequisite for economic success of an electrical energy conservation scheme in cold storages having unique operational features.

Unfortunately, in practice, such vital factors are usually left out in weighing up the success of an energy conservation scheme. As a result, misleading findings are immerged out. Therefore, acceptance of findings of Energy Audit report as a “benchmark” (reference point) in managing energy in any organisation, be it industrial or commercial would be a deceptive conjecture and adoption of the same to translate electrical energy conservation ideas into realities would not be rewarding. Unfortunately, more often than not, the adverse impact of unpredictable supply source and unfavourable tariff structure on electrical energy conservation schemes is usually not being looked into in the right perspective and as a result the projected cost-saving from electrical energy conservation scheme may not come about.


Conservation of electrical energy, alike it’s other forms, is a campaign intended to achieve savings towards cost of energy. Generally, as a perquisite, economic appraisal of the data relating electrical energy usage in an establishment is undertaken to quantify economic advantage of energy conservation scheme. But, in reality, such study is seen to be leaving out such factors as unreliable supply source and unfavourable tariff structure of the supply utility, despite relevance, in predicting the probable cost saving in conservation schemes.

An attempt has been made in this article to highlight the adverse impacts on operation of the cold storage plant, and on conservation scheme on account of unpredictable supply source and a tariff structure not consistent with mode of usage of electricity.

The issues arising out of non-availability of constant quality supply from Distribution License and superintending role of the Electricity Regulatory Authority in that regard have also been analysed in reference to electrical energy saving scheme in seasonal cold storage industries.


The WBERC may consider exempting seasonal cold storage consumers from the purview of the clause 4.3.5 of its Tariff Regulations to ease out the effect of abnormally high electricity cost index on electricity account during their lean operating period. The WBERC may consider extending load factor rebate to seasonal cold storage consumers alike other industrial consumers in West Bengal.