Low Load Diesel Research Articles

An Energy Management Approach for Isolated Power System using Low Load Diesel

Renewable energy sources (RES) are well known sources for providing energy in distant regions. This is the reason that hybrid isolated power system (HIPS) is utilized which integrates solar energy and wind energy. Renewable energy (RE) relies on environmental conditions. The technologies such as batteries or diesel generator (DG) need to be employed to meet the load demand. Battery energy storage system (BESS) can diminish the limitation but this can add expense and intricacy to the system. DG is an excellent choice to meet load demand but it has certain limitations. Due to diesel load set point, excess RE generation is consumed via regulating devices such as dump load or BESS. As a result, systems designed for high RE penetration are now more complex, expensive, and wasteful. This study analyses low load diesel (LLD). It is a method for minimizing surplus generation hence decreasing system intricacy. It also reduces fuel utilization without causing the control architecture to become overly complicated hence reducing the need for BESS. It provides an alternate method for redefining diesel generation's low load capacity. This work provides an economic analysis of LLD including comparisons to traditional BESS applications. This analysis shows low operational cost of the system including LLD than BESS. Hence demonstrating that BESS can be replaced with LLD. The use of LLD also lowers fuel usage. A power system model of HIPS is simulated using MATLAB/Simulink.

Numerical assessment of fuel physical properties on high-dilution diesel advanced compression ignition combustion

Using traditional lean air-fuel mixture aftertreatment technologies to reduce NOx at low exhaust temperatures is limited below 175°C. Recent low engine load NOx emission regulations encouraged researchers to explore the potential of fuel physical properties to enable low-temperature, low-NOx combustion under challenging conditions in which the selective catalytic reduction device might be unable to treat engine-out NOx. Three diesel range fuels were developed to explore how the distillation profile affects and may enable low-load diesel advanced-compression ignition. The least volatile fuel is a conventional, commercially available diesel #2 fuel with a cetane number of 45.3. The second-most volatile fuel is diesel #1 fuel, which can also be found commercially. The last fuel, which is the most volatile, is a new formulation designed to target a final boiling point approximately 50 K below diesel #1 fuel and was termed diesel #0 fuel. A computational fluid dynamics model was developed and validated against experimental data to investigate the underlying effects of each of the developed fuels in the combustion process. Finally, each fuel physical property (e.g., density, viscosity, etc.) was changed independently to assess its effect under the same operating conditions and identify potential directions for fuel formulation that may enable improved NOx emissions and reduce the reliance on aftertreatment systems for NOx control. The results showed that although changes in the fuel distillation curve and other physical properties affect the air-fuel mixtures substantially, changes were not sufficient to result in a large impact to low-load NOx formation. The maximum predicted NOx reduction was 11% uncorrected by combustion phasing. The results suggest that further research efforts should focus on changing the chemical properties of the fuel, like the cetane number, to allow higher EGR dilution and stable combustion.

Thermodynamic analysis of diesel engine ignition delay under low load conditions

In recent decades, renewable energies (e.g., wind and solar) were introduced to reduce the dependency of diesel generation in remote areas and islands power systems. However, diesel generation cannot be eliminated entirely because of the uncertainty and intermittent of renewable sources. In this regards, low load diesel operation (below 30% of maximum rated power) is considered to achieve highest possible penetration of renewable energy in the hybrid (e.g., renewable diesel) power system for isolated locations. Ignition delay (ID) is one of the key parameters to affect engine response and performance in the power generation sectors. This study investigated the diesel engine ignition delay for different load operations from 15% to 100% under different engine speed ranging from 1500 rpm to 2100 rpm. From this analysis, it was found that ignition delay time increased with a decrease in engine load and decreased with an increase in engine speed. The results showed that at 15% and 25% loading conditions ignition delay times are 1.16 and 0.98 ms for 1500 rpm, 0.98 and 1.07 ms for 1800 rpm, and 1.10 and 0.92 ms for 2100 rpm engine speed operation. These results indicate that the change of engine load and speed did not significantly affect ignition delay.

Theoretical Investigation of Combustion and Performance Analysis of Diesel Engine under Low Load Conditions

Diesel engine is using prominently in islands and remote areas due to its reliability and stability for power generation. In recent years, most of the isolated power systems (e.g., islands and remote areas) have integrated renewable energies to reduce both the cost and pollution in diesel power generating system. However, due to intermittent and stochastic behaviour of renewable sources (e.g., solar and wind), it is unable to eliminate diesel generation entirely. In that case, low-load diesel operation (operation < 30% of maximum rated load) is particularly relevant for its ability to support higher levels of renewable penetration. In this paper, a thermodynamic model was developed using MATLAB for diesel engine combustion and performance. This model includes sub models such as heat release rate, heat transfer, double-Wiebe function, and ignition delay correlation. Engine thermal efficiency (TE), brake power (BP), indicated mean effective pressure (IMEP) and brake specific fuel consumption (BSFC) has been taken into consideration for performance analysis. The simulation results show that at 25% load, in-cylinder pressure and temperature are 168 bar and 2300 K which are the cause of lower heat release rate (74 J/deg) and longer ignition delay (0.25 ∼0.5 ms higher than that of conventional mode) and significantly responsible for lower efficiency (18%), brake power (4kW) and higher brake specific fuel consumption (1.2 g/kWh).

Cost-Efficient Strategy for High Renewable Energy Penetration in Isolated Power Systems

Remote areas and islands isolated from the main electric power system ensure reliability and stability of power supply using diesel generation. Due to the high purchase and transportation costs of diesel fuel, isolated communities are exploring other options for efficient and reliable power supply. Renewable energy sources can reduce operating costs, although are unable to achieve high penetration without expensive and complex enabling technologies such as energy storage. Furthermore, the stochastic and intermittent nature of renewable sources (i.e., wind and solar) makes the control system complex, decreasing power system reliability and requiring highly qualified personnel in local control centres. The problem becomes particularly acute when diesel engines are forced to operate at partial load, resulting in poor combustion efficiency and potential engine damage. This paper suggests a fuel-efficient control strategy, adopting low load diesel application to reduce fuel consumption and improve renewable energy penetration without overcomplicating the control architecture. A mathematical model is initially developed, then validated against real data, to facilitate comparative assessment of various control approaches. Optimised control methodologies are shown to deliver fuel savings of 16.7%, with a 14% increase in renewable energy penetration, in comparison to conventional management.

The Role of Low-Load Diesel in Improved Renewable Hosting Capacity within Isolated Power Systems

Isolated communities are progressively integrating renewable generation to reduce the societal, economic and ecological cost of diesel generation. Unfortunately, as renewable penetration and load variability increase, systems require greater diesel generation reserves, constraining renewable utilisation. Improved diesel generator flexibility can reduce the requirement for diesel reserves, allowing increased renewable hosting. Regrettably, it is uncommon for utilities to modify diesel generator control during the integration of renewable source generation. Identifying diesel generator flexibility and co-ordination as an essential component to optimising system hosting capacity, this paper investigates improved diesel generator flexibility and coordination via low-load diesel application. Case study comparisons for both high- and low-penetration hybrid diesel power systems are presented in King Island, Australia, and Moloka`i, Hawai`i, respectively. For King Island, the approach details a 50% reduction in storage requirement, while for Moloka`i the application supports a 27% increase in renewable hosting capacity.

Frequency control within high renewable penetration hybrid systems adopting low load diesel methodologies

In the isolated power system, consumers are traditionally supplied with electricity produced by diesel generators. Conventional diesel generators demonstrate robust and efficient operation when connected to electrical grids with slowly varying loads. With the introduction of intermittent and stochastic renewable energy sources, such generators may not be responsive enough to retain the stability and reliability of the system. The problem becomes especially acute in cases when diesel generators are required to operate at a low load. Regulating devices (e.g. energy storage systems and/or dump load) used to improve the system reliability, increase system complexity and incur additional expenses or energy losses. This paper investigates low load diesel technology as a potential solution to high level renewable energy penetration. The focus is made on the engine time delay and the generator inertia constant that should be considered during the design of the isolated hybrid power system.

High penetration renewable generation within Australian isolated and remote power systems

Remote communities increasingly integrate renewable source generation to reduce the environmental and economic impact of diesel generation. Despite benefits scaling proportionally with the level of renewable penetration, most systems restrict renewable utilisation to below 30% of annual production. Identifying system complexity as a key barrier to renewable uptake, this paper investigates methodologies to simplify integration of high renewable penetrations. Three approaches are considered, via three Australian case studies; King Island, Tasmania (approach one), Flinders Island, Tasmania (approach two), and Rottnest Island, Western Australia (approach three). Approach one details a methodology for wind plus storage integration. Approach two details a methodology for wind, solar PV, plus storage integration. Approach three details a methodology for wind and solar PV integration, without storage. All approaches facilitate high renewable penetrations, with each island majority renewable supplied. Approach one benchmarks system performance, with King Island one of the worlds’ earliest high penetration renewable islands. Approach two explores benefit via renewable diversification. Approach three investigates rationalisation of energy storage via low load diesel and demand management technology substitution. For approach three a 32% reduction in capital cost was observed, identifying commercial justification for the approach via deferral of energy storage integration.

Economics of Renewable Energy Integration and Energy Storage via Low Load Diesel Application

One-quarter of the world’s population lives without access to electricity. Unfortunately, the generation technology most commonly employed to advance rural electrification, diesel generation, carries considerable commercial and ecological risks. One approach used to address both the cost and pollution of diesel generation is renewable energy (RE) integration. However, to successfully integrate RE, both the stochastic nature of the RE resource and the operating characteristics of diesel generation require careful consideration. Typically, diesel generation is configured to run heavily loaded, achieving peak efficiencies within 70–80% of rated capacity. Diesel generation is also commonly sized to peak demand. These characteristics serve to constrain the possible RE penetration. While energy storage can relieve the constraint, this adds cost and complexity to the system. This paper identifies an alternative approach, redefining the low load capability of diesel generation. Low load diesel (LLD) allows a diesel engine to operate across its full capacity in support of improved RE utilization. LLD uses existing diesel assets, resulting in a reduced-cost, low-complexity substitute. This paper presents an economic analysis of LLD, with results compared to conventional energy storage applications. The results identify a novel pathway for consumers to transition from low to medium levels of RE penetration, without additional cost or system complexity.

Influence of exhaust gas recirculation on low-load diesel engine performance

In the condition of constant speed and light load, an experimental study of a turbocharged and intercooled diesel engine with exhaust gas recirculation (EGR) system focuses on the influence of different EGR rates on combustion process, dynamic performance, economic performance and emission performance of a diesel engine. With the increase of EGR rate, the oxygen concentration of the intake-side decreases, the fuel air equivalence ratio increases, and the maximum explosion pressure in the cylinder decreases. Meanwhile, the average temperature in the cylinder drops, the ignition delay is prolonged, the ignition timing delays, and the maximum heat release rate decreases. The increase of EGR rate makes NOx emissions decrease obviously and continue to decline. When EGR is low, the smoke rate enlarges slowly with the increase of EGR rate, and enlarges greatly at the rate higher than 43% and reaches the maximum at the rate of 57%. When EGR rate is higher than 61%, the smoke rate drops rapidly, and the content of CO and hydrocarbon (HC) increases rapidly with high EGR rate.

Economic Rationalization of Energy Storage under Low Load Diesel Application

Globally diesel generator sets account for the majority of generation into remote and off-grid power systems. While diesel generation has proven to be a reliable and accessible technology, its downside involves the expense and environmentally emissions linked to diesel fuel consumption. In response diesel generation alternatives are becoming available and cost competitive, via the integration of renewable energy technology (RET). Hybrid power systems (HPS), those adopting both diesel and RET are increasingly employed to reduce cost and environmental emissions. As RET penetration increases within HPS a potential conflict arises, with diesel generation unable to lower output below minimum load set points. These load set points are predetermined to ensure engine efficiency and reliability. Under medium to high renewable penetration, diesel load set points compete with renewable generation to produce surplus energy. This surplus energy must be absorbed by the system. Various ancillary technologies, such as demand management, energy storage and dump loads can perform this role; however such technologies are expensive and complex. This paper introduces low load diesel (LLD) as one solution to minimising surplus generation within HPS. Economic and power modelling is used to explore removal of energy storage (ES) under LLD application. Model validation, undertaken against both kW and MW scale operational diesel generator data sets is referenced to support the conclusion, that LLD is cable of reducing both system establishment and operational costs for medium to high RET penetration HPS.

Combined Effects of Late IVC and EGR on Low-load Diesel Combustion

The increasing demand for improved efficiency of diesel engines requires more advanced combustion solutions. These solutions include the use of variable valve timings in combination with more traditional methods such as EGR, turbocharging and advanced injection systems. By modifying the characteristics of the charge air, further hardware optimization becomes possible. In the current investigation, the effect of late intake valve closing (LIVC) was investigated together with the effect of (external) exhaust gas recirculation (EGR) in a single cylinder heavy duty diesel engine. Different injection timings and injection pressures were investigated. The mass flow of oxygen was kept constant in order to show how the density and temperature of the reactant mixture affect the combustion and emission characteristics. The combustion results showed that if the oxygen mass flow is kept constant, an EGR approach is more efficient than LIVC in lowering fuel consumption due to the effects of increased cylinder gas flow which improves fuel conversion efficiency. It was shown that the ignition delay for a fixed combustion phasing was independent of EGR but could be increased by LIVC. The peak pressure was more strongly affected by EGR due to the larger gas flow but this response can be reduced by means of LIVC. After compensating for combustion timing effects, the reduced peak pressure was mainly attributed to reduced effective compression ratio resulting from the LIVC. The results show how variable valve timing can be used as one important tool to obtain better combustion characteristics and thus enable more efficient powertrains.

Heavy-duty, off-road diesel engine low-load particle number emissions and particle control

Exhaust gas particle and ion size distributions were measured from an off-road diesel engine complying with the European Stage IIIB emission standard. The measurements were performed at idling and low load conditions on an engine dynamometer. Nucleation-mode particles dominated the diesel exhaust particle number emissions at idle load. The nonvolatile nucleation-mode geometric mean diameter was detected at 10 nm or below. The nonvolatile nucleation-mode charge state implied that it has evolved through a highly ionizing environment before emission from the engine. The determined charging probabilities were 10.0 ± 2.2% for negative and 8.0 ± 2.0% for positive polarity particles. The nonvolatile nucleation particle concentration and size was also shown to be dependent on the lubricant oil composition. The particle emissions were efficiently controlled with a partial filter or with partial filter + selective catalytic reduction (SCR) combination. The particle number removal efficiencies of the aftertreatment systems were over 95% for wet total particle number (>3nm) and over 85% for dry particle total number. Nevertheless, the aftertreatment systems’ efficiencies were around 50% for the soot-mode particles. The low-load nonvolatile nucleation particle emissions were also dependent on the engine load, speed, and fuel injection pressure. The low load particle number emissions followed the soot-core trade-off, similar to medium or high operating loads.Implications:Idling and low-load diesel engine exhaust emissions affect harmfully the ambient air quality. The low-load particle number emissions are here shown to peak in the 10-nm size range for a modern off-road engine. The particles are electrically charged and nonvolatile and they originate from the combustion process. Tailpipe particle control by open channel filter can remove more than 85% of the nonvolatile 10-nm particles and about 50% of the soot-mode particles, while the fuel injection pressure increase can lead to particle number increase. The study provides a new viewpoint for low-load particle emissions and control.