The previous articles in this series dealt with the level of electrification in Sri Lanka, the importance of lighting energy and best possible options of reducing light energy wastage. Falling in line with its precursors, today’s article deals with yet another important aspect of electricity that of being, the electricity demand in Sri Lanka.

Although many of us have the privilege of enjoying the benefits of electricity, little are we aware of the tremendous effort taken to produce this electricity. The Vesak season of 2008 gave rise to many daunting revelations that mostly remained unknown to the public. During this season, the demand for electricity in Sri Lanka reached an all-time peak amounting to 1922 mega watts (MW). This peak demand, which also happens to be the highest ever recorded in the country, was observed on the 22nd of May around 7.30 pm.

Perhaps you would be surprised at this all time high value of 1922 MW, but you would be even more surprised to know that it was none other than you and I who brought about this value. For, this extraordinary demand resulted from all the lamps that are lit at home that particular evening, the rice cookers, fans, TVs, A/Cs and many other day to day electric appliances that operated at that moment, plus the vast number of decorative vesak lights which illuminated our homes, towns and cities.

Sri Lanka’s electricity demand shows a characteristic profile, which is usually depicted through a graph known as the ‘demand profile’. The demand profile denotes time along the X axis and the instantaneous demand of electricity along the Y axis. The demand profile of Sri Lanka is characteristic to many developing countries, marking a low day load and a high evening peak load.

The low day load alludes at the low level of industrialisation in Sri Lanka. This load is warranted by the few energy intensity industries in the country. This portion of the daily demand profile is known as the ‘shoulder’ and occurs during the working hours of the country. Before the occurrence of this, there is another phase known as the ‘off-peak’ or the ‘valley’ demand starting at just before midnight and ends before early mornings at around 5.00 am. The valley corresponds to the period of time wherein the majority of the population is asleep and the rest is not engaged in any electricity consuming activity. Apart from these two dominant phases, there are two more phases depicting peaks. Sri Lanka’s demand profile has twin peaks – a less significant morning peak and a very significant evening peak. The morning peak occurs around the time when we get up to attend to household chores, before leaving home. The evening peak occurs because of the strong necessity to illuminate our homes, cook our rice and also entertain ourselves after a hard day’s work through the unenviable method of sitting in front of a television and digesting whatever is dished out at the click of a button on the remote controller. Another contributory factor to this evening peak is the tea industry, which usually consumes substantial amount of electricity in withering tea, as the process uses around 4 to 10 electric motors in every one of the 650 odd tea factories. The withering cycle begins almost at the same time as the evening peak, as green tea leaves is delivered to factories in the evening. Added to this, security lamps, water pumping motors and even hoarding lights come on during this time, further increasing the evening peak.

From the above graph, it is evident that this country requires approximately 700MW of electrical power during any hour on a working day. However, this profile changes a lot during a non-working day, having a lower than usual shoulder demand and lower peaks and even a lower valley.

This profile is closely monitored by the CEB engineers, who manipulate the electricity supply to meet the demand of electricity at any given point in time, with exact precision. Not even your morning tea break or the busy load in tea factories are allowed to go unattended.

The least amount of power that the country requires during any time of any day of the year is known as the base load. The base load is usually supplied by using the lowest cost generation equipment such as a coal power plant or a nuclear power plant in most other countries. These power plants are expensive to build, but far cheaper to operate than other types of power plants. It does not favour frequent switching on and off type of operations as well as partially loaded operating conditions in meeting the varying demand during the day. In comparison with the transport system of this country, the base load plants can be equated to long haul trains such as Mahawa and Ruhunu Kumari, which carries the bulk of the office workers from those areas, offering very little flexibility to commuters as it usually leaves on time and does not stop frequently at in-between stations unlike a ‘power set’ or a CTB bus. Inasmuch, the variations of the electricity demand will have to be taken by either hydropower stations or oil burning power stations comparable with the road transport elements such as buses and vans.

CEB engineers meet the evening peak with many difficulties. They are at their toughest during the dry periods of the country wherein most reservoirs get depleted. Hence they are compelled to supplement the electricity demand by operating all power plants at their disposal. Supplementing this peak demand requires the operation of gas turbines, which can be easily started and stopped to meet the short periods of high demand. However, these plants are quite expensive to operate, compared even to other types of oil burning power plants such as combined cycle power plants and engine driven power plants. Hence, the gas turbines can be equated to luxury limousine taxes, which we resort to only during a special occasion or if all else fail.

The mini-hydro power plants and wind power plants are termed ‘non-dispatchable’ as their operation is not centrally controlled. Simply put in, their existence is not ‘felt’ by the large power supply system. In our transport analogy, these small power producers are none other than a fleet of three wheelers which supplement the main mode of transportation in the country. Even though the central command does not feel the existence of the fleet of small power producers, they help to off-load a fraction of the demand felt by the central power plants, providing several comforts to the operators – just like the three wheelers forming a valuable safety net in the rural and urban sector, assisting the mainstream transport sector in no small measure. However, just like the fleet of taxes, the small power plants too can opt to keep off the system if they wished to do so, leaving many a consumer stranded at the most critical period. This is due to the unreliable nature of many renewable energy sources such as wind, which are notorious for their diurnal and seasonal variations.

Then comes the argument, why the entire demand cannot be met with cheaper power plants and why not aim at providing all our generation with renewable energy resources. If we are to use the same transport analogy, this can be pictured as attempting to replace an entire public transport mechanism with a fleet of private cars, at great expense to the country during implementation as well as in operation. Hence we have to be very careful in choosing the right mix of generation in meeting our electricity demand as it can have consequences which can last a few decades. A clear long term vision and unwavering determination of many generations of planners at CEB have all contributed to keep Sri Lanka out of the dark quite exceptionally, compared to our other South Asian counterparts wherein some countries experience bewildering power cuts as long as 10 hours! The dire truth – the high cost of electricity we experience today could have been well avoided if the precursors of planning and implementation processes were joined with the missing link of ‘political will’. The situation today however, is somewhat different and that is exactly why the country is progressing with the coal power plants, instead of giving into baseless, yet vehement arguments which hitherto prevented these from coming into force.