Diesel generator sets are widely used as the most preferred ‘power back-up’ by all major sectors in India – households, manufacturing, agriculture, commercial applications, construction, and buildings. This is primarily because India’s power sector is still struggling to find ways to overcome the problems of unreliable, inadequate and interrupted power grid supply. In light of growing dependence over diesel sets and the fact that diesel consumption is one of the reasons behind harmful emissions, it is important to shift our focus towards diesel generator efficiency and emission norms.
The Bureau of Indian Standards (BIS) has set mandatory maximum energy consumption limits, the SFC (Specific Fuel Consumption), for diesel generators up to 19 KW capacities. The SFC limit is also prescribed for sets above 19 KW to 500 KW capacities, but these are not mandatory. Since 1999, there has been no revision in the limits although there is enough scope, given the fact that technology has rapidly evolved since then. The Bureau of Energy Efficiency set up in 2002 is now trying to aid customers in making an informed choice, by allocating energy performance standards to equipment and appliances.
Diesel generator energy efficiency for industries and other sectors is the combined efficiency of the two sub-components that make a diesel generator set – the engine and the alternator. Some key findings of the study and research that can shape the efficiency norms for diesel generator sets in India are listed below:
Engine efficiency improves with increase in the size of the generator sets. A bigger size allows for more room for technological improvements within the engine design, geometry, fuel control mechanism, and so on. Larger sets above 500 KVA have higher have better Specific Fuel Consumption (SFC) rate.
There are significant efficiency gaps between Indian and global brands of diesel generators. There is much scope of improvement for indigenously manufactured diesel generator sets.
Indian diesel market comprising primarily agriculture, small offices and establishments and households give more importance to pricing than efficiency and hence go for smaller sized sets up to 50 KW.
SFC is optimum at 75-80% loading of the rated capacity and worsens at 25% load or below.
When in use, diesel generator sets emit a number of harmful gases including Carbon monoxide (CO), oxides of nitrogen (NOx), unburned hydrocarbons, and soot particles. All these pollutants are covered under the emission norms in India set by the Central Pollution Control Board. The emission norms or limits are specified in number of grams of these pollutants present in diesel exhaust when 1 Kilowatt/hour of electricity is generated. The revised norms have been put to action from April 2014.
Under the new norms, there is a combined cap on CO and NOx, and the limit has been tightened for all size categories of diesel generator sets; both steps being in line with the global emission standards. In fact, the revised emission norms now are equivalent to Euro Stage IIIA. In case of CO, India has the lowest emission limit globally. Some factors which largely impact the emission levels in diesel generator sets include availability of diesel with lower sulphur content and the operations and maintenance practices.
As the global standards for diesel generator efficiency and emissions improve continuously, India must also make every effort to bring in more technological options, awareness programs and practices that could help improve the overall efficiency and emissions leading to stricter norms for future.