A topical issue is whether diesel power will still be relevant in the future. Climate trends are now demanding that all users of power employ tactics to reduce harmful emissions that impact the environment, and renewable energy solutions are advancing beyond the infancy stage of the technology lifecycle in Southern Africa.
Nalen Alwar, Projects Sales Manager for Cummins Power Generation Southern Africa, points out that diesel fuel is still by far the most widely-used fuel source, especially in developing nations and emerging markets.
“Diesel power is still the mainstay solution for operational resilience and industrialisation in remote areas. Significant technology improvements have been made towards reduction in capital, operating costs and environmental stewardship,” states Alwar.
Efficiency of diesel
The efficiency of a diesel engine is most directly tied to combustion rate – the degree to which the fuel is completely burned during ignition. This is typically a function of how finely and evenly dispersed the fuel is during injection into the combustion chamber.
Turbocharging, which forces excess air into the chamber, also improves the combustion rate, which is why two-stage turbocharging, with intercooling between the stages, is now common for diesel gensets.
Alwar explains that a Modular Common Rail System (MCRS) enables diesel engines to achieve exceptionally low fuel consumption for their power output. The MCRS injectors are capable of extremely high-pressure injection, which leads to a reduction in particulate matter emissions. This method replaces traditional mechanical injection with electronically-controlled multiple high-pressure injections during each combustion cycle.
Rather than rely on separate injectors controlled by a camshaft, it uses a single system that supplies all the injectors in the engine with a common source of fuel. This allows much higher fuel pressures than a mechanical injection system, which maximises vaporisation of the fuel, and thus combustion rate. Modern high-pressure common-rail diesel fuel systems allow for much higher fuel pressures, and much more precise and flexible injection of fuel into the combustion chamber.
Meeting international environmental standards
To meet Tier 4 low-emission standards as set out by the US government’s Environmental Protection Agency (EPA), Selective Catalytic Reduction (SCR) technology has been used successfully on new Cummins diesel gensets to reduce NOx emissions by as much as 95%. Another method often used with SCR is exhaust-gas recirculation, which sends part of the exhaust gases back to the combustion chamber. This lowers the adiabatic flame temperature, allowing for lower temperature combustion and reduced NOx production. SCR also results in 5% more fuel efficiency.
With diesel gensets typically representing either emergency generation or generation where there may be no grid power to fall back on, these are critical considerations. Oil-management systems that replenish oil automatically, based on engine-load factors, fuel filtrations systems with enhanced durability, high-pressure fuel systems and prognostic capabilities, are other improvements that reduce operating costs.
A typical scheme could comprise renewable power generation sources such as wind and solar. However, Alwar believes that these pose challenges to system reliability and performance, given their inherent intermittent contribution and associated disturbances.
Manufacturers of diesel gensets are making steady technological gains that reduce capital intensity and emission levels, and enhance power output and efficiency. Diesel-generated power is still likely to feature on its own or incorporated into hybrid solutions for many more years.