Design Improvements

Modifications in diesel gensets aim for greater efficiency

Over time, diesel engines have undergone several modifications to make them more efficient with respect to fuel economy, power output and exhaust fumes. Recent advances in diesel engine technology include a modification of the pre-chamber and the combustion chamber designs for maximum combustion and acoustical attenuation. With the imposition of stricter environmental norms, diesel gensets are equipped with exhaust gas recirculation (EGR) and selective catalytic reduction (SCR) solutions to minimise emissions. A recent technology trend has been the use of hybrid systems, which combine diesel engines with at least one renewable energy source. Another technology trend that has gained traction is the use of smart diesel engines, which deploy digital solutions for operation control, load distribution and efficient combustion. Power Line explores key technological developments in diesel engines and gensets….

Hybrid generators

Hybrid/Multifuel generators are new-age generators that combine conventional diesel generator sets with a renewable source of power such as wind, biomass or solar. These systems may have a storage facility. Such a system is cost efficient as it reduces the dependence on expensive diesel fuel, offers clean energy generation in compliance with the environmental norms, and provides uninterrupted power supply. The most common hybrid technology combines diesel gensets with solar photovoltaic systems. One of the emerging technologies in the hybrid genset space is storage batteries. The batteries in hybrid gensets are charged by renewable power sources along with the fuel generators during operation. Although adding battery storage to diesel-solar hybrid systems involves high capex costs initially, it improves operational efficiency during the lifecycle of the system; hence, it is cost effective in the long run. Hybrid generators find application in places where access to fuels is difficult. Hybrid generator sets run for a long duration with less fuel. Besides, in areas with size and weight constraints, hybrid generators are a good choice as they are compact and can be transported easily.

Waste heat recovery systems

One way of improving combustion process efficiency is the deployment of waste heat recovery (WHR) systems along with diesel generator systems. A WHR system recovers heat from steam and transforms it into electrical energy for utilisation by energy conversion devices like regenerators, recuperators and economisers. A WHR system stops heat from entering the atmosphere, reducing environmental pollution. WHR systems reduce fuel consumption, leading to smaller equipment sizes.

Exhaust gas recirculation

The exhaust gas recirculation process is used to reduce the levels of NOx emitted by the engine. By recirculating exhaust gases into the engine’s cylinder, a percentage of the air is replaced with CO2. This process lowers the combustion temperature due to the reduced amount of oxygen which, in turn, reduces the amount of NOx formed. However, the EGR system has lower combustion efficiency and higher heat rejection. Exhaust recirculated back into the cylinder can increase engine wear as carbon particulates blow by the piston rings and into the oil, impacting its reliability and durability.

Selective catalytic reduction

This method utilises a reducing catalyst such as anhydrous or aqueous ammonia or urea to convert NOx into diatomic nitrogen and water. It is known to reduce NOx emissions in a range of 75-95 per cent. The SCR system offers better power and higher fuel economy due to higher combustion efficiency. Clean combustion ensures higher reliability of engines.

Smart diesel gensets

Smart diesel gensets consist of digital controls instead of analogue controls installed in conventional systems. Digital controls are integrated and report the real-time status of all aspects of a diesel engine – fuel, engine oil, coolant, engine temperature, battery status and transfer switch status. These systems can be connected to a computer to enable remote monitoring of operations. Digital controls also increase fuel efficiency and reduce emissions by making automatic adjustments to the fuel input rate. A digital diesel genset enables auto-synchronisation and fast synchronisation. Besides, an internet of things-enabled diesel genset offers real-time insights into fuel consumption and theft detection.

Silent diesel gensets

The noise in a diesel genset occurs mainly when the engine is started as the fuel is injected into the pre-chamber and is forced to vapourise at a high temperature. Recent advances have reduced the noise levels to a significant extent. This is done by fitting the pre-chamber with sound attenuation pockets. These pockets are spaced and designed such that they nullify the detonation waves caused during combustion. Alternatively, these pockets are filled with porous or metallic ceramic pellets, which are coated with platinum or rhodium and act as catalysts to achieve complete combustion and the pellets attenuate the noise levels.

Outlook

With stricter requirements for engines and generators, the segment is expected to see substantial improvements in engine modifications, fuel system efficiency, enhanced digital controls, emission treatments and more in the coming years. This will help make diesel gensets an even stronger source of power. For best results, it is essential to identify the most suitable technology, depending on the needs and requirements of the end-consumers.

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