Efficient Engine Operation Research Articles

Comparative study of real-time A-ECMS and rule-based energy management strategies in long haul heavy-duty PHEVs

Road transport is a significant contributor to Green House Gas (GHG) emissions in the European Union (EU) and is responsible for approximately 25% of total GHG emissions in the EU13. The European Commission has proposed stricter CO2 emissions targets for heavy-duty vehicles that require manufacturers to achieve a reduction of 90% in average fleet emissions from new vehicles by 2040 compared to a 2019 baseline. To meet these ambitious targets, there is an urgent need to explore alternative pathways away from conventional fossil fuel-based powertrain systems like electrified powertrains and carbon–neutral fuels. One promising option is the plug-in hybrid electric powertrain concept, which combines the advantages of both power sources, enabling improved fuel efficiency and reduced CO2 emissions. However, the potential of such a plug-in hybrid powertrain needs to be evaluated for heavy-duty trucks.This study focuses on the development of control strategies for the Energy Management System (EMS) of the above powertrain concept. First, a control strategy for the non-predictive EMS’s start/stop functionality and optimization of the torque split between the combustion engine and electric machine is developed and calibrated for efficient engine operation depending on the battery state of charge. In addition, a predictive EMS’s control strategy is developed that uses horizon information of the driving route for optimal utilization of electrical energy within the prediction horizon, thereby further enhancing fuel consumption reduction. The predictive EMS uses Adaptive Equivalent Consumption Minimization Strategy (A-ECMS) with Pontryagin’s Minimization Principle (PMP) for online equivalence factor adaptation, providing local optimal solutions in real-time. The study concludes with the energy savings achieved through the implementation of these strategies using real-world driving cycles in the heavy-duty transport sector.

Parameter fine tuning on CRDI engine operated with blends of grape biodiesel and diesel

This study investigates the feasibility of using grape biodiesel from the wine industry as a sustainable and cost-effective alternative to traditional fuels. The research focuses on optimizing key parameters like blend ratio, injection timing, injection pressure, engine load, and exhaust gas recirculation in a Common Rail Direct Injection engine to achieve low emissions without compromising performance. Due to grape biodiesel's higher viscosity, different energy content, and varying ignition delays compared to diesel, precise adjustments are essential for complete combustion and reduced emissions. This study uses response surface methodology and a Central Composite Design matrix to find the best values for a number of parameters in modern CRDI engines that use advanced electronic control units. Through fifty input combinations, the study aims to minimize specific fuel consumption, hydrocarbons, nitrogen oxides, and carbon monoxide while maximising brake thermal efficiency, brake mean effective pressure, and mechanical efficiency. The optimal configuration includes a fuel injection timing of 6° bTDC, an engine load of 82 %, 6.7 % EGR, 1000 bar injection pressure, and a 33 % grape biodiesel blend. These optimum input conditions yielded outputs of 3.55 bar BMEP, 31.85 % BTE, 64 % mechanical efficiency, 0.278 kg/kWh SFC, 0.127 % CO, 357 ppm NOx, and 8 ppm of HC. These adjustments ensure low emissions and efficient engine operation, highlighting grape biodiesel's potential as a viable alternative fuel.

Influence of injection strategies on ignition patterns of RCCI combustion engine fuelled with hydrogen enriched natural gas

The depletion of fossil fuel and the concerns for harmful emissions and global warming has instigated researchers to use alternative fuels. Hydrogen (H2) and natural gas (NG) are attractive fuels for internal combustion engines. The dual-fuel combustion strategy is promising to reduce emissions with efficient engine operation. The concern for using NG in this strategy is the lower efficiency at low load conditions and the emission of exhaust gases like carbon monoxide and unburnt hydrocarbon. Mixing fuel with a wide flammability limit and a faster burning rate with NG is an effective method to compensate for the limitations of using NG alone. Hydrogen (H2) is the best fuel added with NG to cover NG limitations. This study investigates the in-cylinder combustion phenomenon of reactivity-controlled compression ignition (RCCI) engines using hydrogen-added NG as a low-reactive fuel (H2 addition to NG on a 5% energy basis) and diesel as a highly reactive fuel. The numerical study was done on a 2.44 L heavy-duty engine using CONVERGE CFD code. Three low, mid, and high load conditions were analyzed in six stages by varying the diesel injection timing from −11 to −21 O after top dead centre (ATDC). The H2 addition to NG had shown deficient harmful emissions generation like carbon monoxide (CO) and unburnt hydrocarbon with marginal NOx generation. At low load conditions, the maximum imep was achieved at the advanced injection timing of −21OATDC, but with the increase in load, the optimum timing was retarded. The diesel injection timing varied the optimum performance of the engine for these three load conditions.

Control Design of a Hydraulic Cooling Fan Drive for Off-Road Vehicle Diesel Engine With a Power Split Hydraulic Transmission

The engine cooling fan drive is crucial for an engine as it ensures safe and efficient engine operation. In heavy-duty mobile machine, the engine cooling fan consumes a considerable amount of engine power. To meet high cooling demand a hydraulic fan drive is usually employed. A simple and cost-effective way is to use two fixed displacement hydrostatic units and a pressure relief valve where it has severe valve throttling losses. A more efficient way is to use a variable displacement pump to drive a fixed displacement motor. It eliminates valve throttling however the drive efficiency is still relatively low due to variable pump displacement control. Therefore, an engine cooling fan drive system with a power split hydraulic transmission was proposed in the previous study. The hydraulic transmission is a compact unit with both pumping and motoring functions. The fan speed is controlled by adjusting the transmission outlet pressure. Although previous results showed the system has relatively higher drive efficiency than conventional hydraulic fan drive at different fan speeds, the control design, and system dynamic performance have not yet been studied. Therefore, in this article, the control design of the cooling fan drive system with power split hydraulic transmission is studied. A feedforward controller based on transmission characteristics is designed to achieve better system performance. A hydraulic fan drive test bench is developed to evaluate system control design. The system dynamic performance with feedforward and feedback controls are compared through both simulation and experimental studies.

Effects of high octane additivated gasoline fuel on Three Way Catalysts performance under an accelerated catalyst ageing procedure

The adoption of high octane rating fuels in Gasoline Direct Injection (GDI) engines helps to improve fuel economy and thus reduce CO2 emission. However, there is scarce literature regarding the impact of additives used in high octane rating fuels on the performance and durability of the exhaust after treatment components. This work investigates the effects of using an aniline (aromatic amine) octane enhancer added to a commercial gasoline fuel on the activity of a commercial Three Way Catalytic Converter (TWC) coupled to a GDI engine. TWC’s capability in abating gaseous and particle emissions is studied for both the additivated and the baseline fuel during and after a fuel-induced accelerated catalyst ageing procedure. The accelerated catalyst ageing procedure is developed aiming to identify the impact of the engine fuel on the catalyst poisoning, while limiting catalyst thermal deactivation.CO and NO conversion efficiencies in the TWC were close to 100% under the steady-state and transient stoichiometric engine operation for both fuels during and after the catalyst ageing procedure. There was a minor decrease (generally < 10%) in the catalytic conversion efficiency of total HC for the additivated fuel, but not being significant to reflect any TWC chemical deactivation. The aniline type octane enhancer additive did not produce any detrimental effect on the TWC efficiency/performance. This investigation demonstrates that fuels being designed to promote a more efficient GDI engine operation can also enable the reduction of vehicle tailpipe CO2 and pollutant emissions through synergies with the TWC for cleaner road vehicles.

An Energy Efficient Power-Split Hybrid Transmission System to Drive Hydraulic Implements in Construction Machines

Abstract This paper proposes a novel hybrid power-split transmission to drive hydraulic implements in construction machinery. The highly efficient power-split hybrid transmission is combined with displacement-controlled (DC) actuators to eliminate throttling losses within the hydraulic system and achieve higher fuel savings. The architecture design, sizing, and power-management are addressed. Simulation results considering a realistic truck-loading cycle on a mini-excavator demonstrate the feasibility of the idea. A systematic comparison between the proposed system and the previously developed series–parallel hybrid is also carried out. The paper compares engine operation and fuel consumption of the previously mentioned hybrid system with the original nonhybrid load-sensing (LS) machine. It is shown that by implementing an efficient engine operation control, the proposed system can achieve up to 60.2% improvement in fuel consumption when compared to the original machine and consume 11.8% less than the previously developed series–parallel hybrid with DC actuation. Other advantages of the proposed solution include a much steadier engine operation, which open to the possibility of designing an engine for optimal consumption and emissions at a single operating point as well as greatly reduce pollutant emissions. A steadier prime mover operation should also benefit fully electric machines, as the battery would not be stressed with heavy transients.

Automated calibration of gearshift controllers using iterative learning control for hybrid systems

Newer-generation automatic transmissions are typically characterized by large ratio spreads and small ratio steps, which enable efficient engine operation and good gearshift comfort that is essential for vehicle drivability. However, the increased number of gear ratios results in an exponential increase in the number of gearshift control parameters to be calibrated. Existing automated calibration approaches using dynamometers for testing are Design-of-Experiments (DoE) based and, consequently, require a large number of gearshifts for the calibration of gearshift controllers. The full potential of automation of the calibration process is still to be realized. With this underlying motivation, a model-based automated calibration algorithm that uses at its core Iterative Learning Control (ILC) for hybrid systems is presented in this study. A recently developed theory of ILC for hybrid systems is adapted for the application of gearshift control. Three design methods for the computation of learning controllers for automated calibration of gearshift controllers are presented, and validated numerically using realistic computer simulations of 1–2 power-on upshifts and experimentally via dynamometer testing of 2–3 power-on upshifts. The results demonstrate the ability of the developed ILC procedures to perform automated calibration of gearshift controllers with far fewer gearshifts than state-of-the-art automated calibration approaches.

Experimental research and energy consumption analysis on the economic performance of a hybrid-power gas engine heat pump with LiFePO4 battery

Hybrid power gas engine heat pump (HPGHP) is a novel air conditioning system that uses a power battery as an auxiliary power source to achieve efficient engine operation. Considering that frequent changes in external load can cause frequent charge/discharge of the battery and adversely affect energy conversion efficiency, lithium iron phosphate (LiFePO4) battery was used as the auxiliary power source to analyze its economic performance. A dynamic energy control strategy based on engine economic zone and battery status was proposed to realize power distribution between gas engine and electric motor. By analyzing the fuel consumption rate, energy conversion efficiency and energy consumption, the superior performance of the LiFePO4 battery HPGHP was confirmed. Test results show that the minimum gas consumption rate of LiFePO4 battery HPGHP under low-load, medium-load and high-load conditions was 12.2%, 1.07%, and 6.54% lower than that of lead-acid battery HPGHP. Equivalent energy conversion efficiency was about 7.03%, 0.98%, and 10.42% higher than lead-acid battery HPGHP, 18.56%, 1.98%, and 27.2% higher than conventional GEHP. In addition, energy consumption analysis indicates that the annual primary energy rate (PER) of LiFePO4 battery HPGHP was about 39.85%, 28.35%, and 8.4% higher than electrical heat pump (EHP), GEHP and lead-acid battery HPGHP.

The potential of heat release rate and cylinder pressure feedback control for conventional and premixed charge compression ignition combustion

Cylinder pressure or heat release rate tracking algorithms for direct-injected compression ignition engines allow to account for various disturbances, such as changes in the fuel characteristics or the effects of engine wear. They are suited for flex-fuel engines and allow the use of multi-injection strategies; hence, they show potential for mobile applications. However, they are based on the assumption that the heat release rate or cylinder pressure correlates well with engine efficiency and emissions and therefore allows a clean and efficient engine operation. With the objective to evaluate the potential of such tracking algorithms, this assumption is investigated for conventional as well as for low-temperature combustion strategies with diesel as fuel of choice. Based on experimental data, exploratory data analysis methods are applied to evaluate how sensitive engine efficiency and emissions are to changes of the heat release rate or cylinder pressure. Furthermore, an extended tracking algorithm is proposed, which can be applied for premixed charge compression ignition combustion concepts.

Experimental and Kinetic Modeling Study of Laminar Burning Velocities of Cyclopentanone and Its Binary Mixtures with Ethanol and n-Propanol

Cyclopentanone is a promising biofuel that can enable more efficient engine operation and increase the fuel economy of the light duty fleet over current and planned technology developments. While the ignition of cyclopentanone has been investigated in detail, more studies on the laminar burning velocities of cyclopentanone are called for. In this work, the laminar burning velocities of cyclopentanone (C5H8O) have been measured using the heat flux and spherical flame methods at 1 atm, equivalence ratios from 0.7 to 1.6, and initial temperatures of 328, 353, and 428 K. To further investigate the relationship between the molecular structure and laminar burning velocity, identical experiments were also performed for binary mixtures of cyclopentanone with ethanol and n-propanol at 1:1 (mol). The consistency between the experimental data sets obtained in this work and literature data sets has been evaluated. A recently published mechanism of cyclopentanone was used for simulation after adopting the submechanism of n-propanol. Good agreement has been seen between experimental and simulated results for all flames. To qualitatively explain the characteristics of the laminar burning velocity of cyclopentanone and the differences with those of ethanol and n-propanol, sensitivity analysis and reaction pathway analysis have been performed to compare the chemistry of the fuels under flame conditions, which revealed how the molecular structure of cyclopentanone could affect its laminar burning velocity. Compared to ethanol and n-propanol, cyclopentanone does not have primary carbon atoms in its molecule, leading to lower production of methyl radicals. Meanwhile, the carbonyl group in the cyclopentanone molecule is mostly released as CO in the decomposition of multiple intermediates accompanied by the production of unsaturated C2 and C4 species, especially C2H4 and C2H3. Both features contribute to the high laminar burning velocity of cyclopentanone. (Less)

Application of a Model-Based Controller for Improving Internal Combustion Engines Fuel Economy

Improvements in internal combustion engine efficiency can be achieved with proper thermal management. In this work, a simulation tool for the preliminary analysis of the engine cooling control is developed and a model-based controller, which enforces the coolant flow rate by means of an electrically driven pump is presented. The controller optimizes the coolant flow rate under each engine operating condition to guarantee that the engine temperatures and the coolant boiling levels are kept inside prescribed constraints, which guarantees efficient and safe engine operation. The methodology is validated at the experimental test rig. Several control strategies are analyzed during a standard homologation cycle and a comparison of the proposed methodology and the adoption of the standard belt-driven pump is provided. The results show that, according to the control strategy requirements, a fuel consumption reduction of up to about 8% with respect to the traditional cooling system can be achieved over a whole driving cycle. This proves that the proposed methodology is a useful tool for appropriately cooling the engine under the whole range of possible operating conditions.

Evaluation of regulated, particulate, and BTEX emissions inventories from a gasoline direct injection passenger car with various ethanol blended fuels under urban and rural driving cycles in Korea

In this study, the regulated, particulate, and unregulated emissions, and the fuel economy (FE) from a direct injection spark ignition (DISI) vehicle were investigated on a chassis dynamometer. Two vehicle test cycles, the congested urban (NIER03) and rural modes (NIER09), which reflect vehicle driving patterns in Korea, were tested with varying ethanol contents of gasoline (E0), and low- (E10), medium- (E30 and E50), and high-ethanol blended fuels (E85). The particle number (PN) concentration from E0 was substantially reduced by one or two orders of magnitude with medium- or high-ethanol blended fuels, respectively. The E10 fuel showed the highest PN concentration because of the physicochemical mixture properties of the azeotropic characteristics. As the ethanol fraction increased, the particle sizes shifted to smaller sizes that were dependent on the vehicle test modes and oxygen proportions in the fuels. The regulated and unregulated emissions showed close relationships with the vehicle test modes and ethanol blends. Vehicle running with frequent idle-stops at an extremely low speed and dynamic transient driving under NIER03 showed higher BTEX emissions than the NIER09 mode, and produced lower emission levels due to the higher oxygen and lower aromatic proportions of the ethanol blends. Compared to the NIER03 mode, the CO2 emissions and FEs under the NIER09 mode were substantially improved, with a higher vehicle speed and more energy efficient engine operation points. The low energy contents of the E85 fuel resulted in slight increases in the CO2 emissions and reductions in the FEs of the NIER modes.

Thermodynamic analysis of the influential mechanism of fuel properties on the performance of an indirect precooled hypersonic airbreathing engine and vehicle

Fuel indirect precooled engines are promising power to realize the vision of greener and faster air transportation. Efficient operation of the engines relies critically on sophisticated energy management schemes, within which the fuel plays a decisive role. Research here intends to make clear the mechanism of how the energy conversion process of this innovative cycle is driven by properties of the fuel. A unified engine model was developed for analysis, through which it indicates that besides the properties commonly known, the triple point temperature and stoichiometric heat capacity (SHC) of the fuel are also crucial to efficient engine operation. Numerical engine method and the Concorde airplane were proposed to evaluate the synthetic influence of the multiple properties on engine and vehicle performance, with four seemingly promising fuels, i.e., the methane, n-decane, methanol and hydrogen were selected for further assessment. Experiments were performed to evaluate the contribution of chemical endothermic effect (CEE) to SHC. On account of the results, the impacts of the CEE and the quantitative significance of fuel properties on engine and vehicle performance are revealed. Also, it indicates that the system fueled with hydrogen shows superior performances in engine specific impulse and specific thrust, in spite that the corresponding flight range of the vehicle is extremely poor. On the contrary, the systems using hydrocarbon fuels (i.e., methane, n-decane or methanol) exhibit better performance in vehicle flight range, but their related engine-level performances such as the specific impulse/thrust are usually lower than that using hydrogen. Considering this complementary feature, it implies that combined use of several fuels (for instance, hydrogen + kerosene) may provide more balanced and better overall performance than that of the single fuel scheme.

Component-Specific Preliminary Engine Design Taking into Account Holistic Design Aspects

Efficient aero engine operation requires not only optimized components like compressor, combustor, and turbine, but also an optimal balance between these components. Therefore, a holistic coupled optimization of the whole engine involving all relevant components would be advisable. Due to its high complexity and wide variety of design parameters, however, such an approach is not feasible, which is why today’s aero engine design process is typically split into different component-specific optimization sub-processes. To guarantee the final functionality, components are coupled by fixed aerodynamic and thermodynamic interface parameters predefined by simplified performance calculations early in the design process and held constant for all further design steps. In order not to miss the optimization potential of variable interface parameters and the unlimited design space on higher-fidelity design levels, different coupling and optimization strategies are investigated and demonstrated for a reduced compressor-combustor test case problem by use of 1D and 2D aero design tools. The new holistic design approach enables an exchange of information between components on a higher-fidelity design level than just simple thermodynamic equations, as well as the persecution of global engine design objectives like efficiency or emissions, and provides better results than separated component design with fixed interfaces.

Experimental investigation of performance and emission characteristics of diesel engine using Jatropha biodiesel with alumina nanoparticles

ABSTRACTBiodiesels have come up as a very strong alternative for diesel fuel. Biodiesels such as Jatropha Oil Methyl Ester (JOME) are comparable in performance with that of the diesel engine. The thermal efficiency of engines fuelled with biodiesels was found lower than conventional diesel fuel but due to the bio-origin, the emission characteristics are much better. However, biodiesel increases the NOx emissions as these are rich in oxygen, hence nanoparticles are used in this experiment to curb the high temperatures and reduce the NOx formation. The experiment on naturally aspired diesel engine was conducted with four prepared test fuels other than neat diesel and neat biodiesel. The 50 and 150 of alumina nanoparticles were added separately to the pure diesel and pure Jatropha biodiesel to form the nano emulsions using ultrasonicator. The properties of nanoemulsion were evaluated using dynamic light scattering technique using zetasizer. The performance and emission characteristics of multi-cylinder diesel engine with these nanoemulsions were compared with that of neat fuels. The results showed that using nanoparticles with diesel and biodiesel can contribute in a more efficient, economical, and eco-friendly engine operation.

Experimental investigations of LASER ignition use at spark ignition engine

In the current global context, due to the impact of pollutant emissions produced by internal combustion engines on the environment, researchers in the automotive industry are designing and implementing new technologies. LASER ignition as a potentially superior ignition source for technical appliances can also be suitable for internal combustion engines. The objective of the paper is the experimental research of LASER ignition use in the spark ignition engine. The experimental results present the influence of LASER ignition on different engine parameters compared to electric spark ignition. The paper also analyses the influence on in-cylinder pressure, heat release rate, heat release law and engine efficiency. The LASER ignition system assures efficient engine operation at lean dosages.

Exergy Analysis of Dual-Fuel Operation with Diesel and Moderate Amounts of Compressed Natural Gas in a Single-Cylinder Engine

ABSTRACTAn energy-exergy heat release model is used with in-cylinder pressure measurements to analyze dual-fuel combustion in a high compression ratio diesel engine. Compressed natural gas (CNG) addition does not exceed 40% of total fuel energy, in order to avoid significant changes to liquid fuel injection timing needed to maintain efficient engine operation. Increasing CNG usage is observed to enhance exergetic efficiency, as premixed combustion is promoted over diffusion burn. In addition, CNG usage is associated with higher exergy retention by the exhaust gases. However, this comes with decreased combustion efficiency as CNG survives combustion and is lost to the exhaust. Overall, the analysis shows that CNG usage may result in lower absolute exergy consumption by the engine, even alongside the lost exergy from unburned fuel, as the wasted CNG is simultaneously less exergetically useful, and thermal efficiency rises due to increased premixed combustion.

Achieving clean and efficient engine operation up to full load by combining optimized RCCI and dual-fuel diesel-gasoline combustion strategies

This experimental work investigates the capabilities of the reactivity controlled compression ignition combustion concept to be operated in the whole engine map and discusses its benefits when compared to conventional diesel combustion. The experiments were conducted using a single-cylinder medium-duty diesel engine fueled with regular gasoline and diesel fuels. The main modification on the stock engine architecture was the addition of a port fuel injector in the intake manifold. In addition, with the aim of extending the reactivity controlled compression ignition operating range towards higher loads, the piston bowl volume was increased to reduce the compression ratio of the engine from 17.5:1 (stock) down to 15.3:1.To allow the dual-fuel operation over the whole engine map without exceeding the mechanical limitations of the engine, an optimized dual-fuel combustion strategy is proposed in this research. The combustion strategy changes as the engine load increases, starting from a fully premixed reactivity controlled compression ignition combustion up to around 8bar IMEP, then switching to a highly premixed reactivity controlled compression ignition combustion up to 15bar IMEP, and finally moving to a mainly diffusive dual-fuel combustion to reach the full load operation. The engine mapping results obtained using this combustion strategy show that reactivity controlled compression ignition combustion allows fulfilling the EURO VI NOx limit up to 14bar IMEP. Ultra-low soot emissions are also achieved when the fully premixed combustion is promoted, however, the soot levels rise notably as the combustion strategy moves to a less premixed pattern. Finally, the direct comparison of reactivity controlled compression ignition versus conventional diesel combustion using the nominal engine settings, reveals that reactivity controlled compression ignition can be a potential solution to reduce the selective catalyst reduction and diesel particulate filter aftertreatment necessities with a simultaneous improving of the thermal efficiency.

Aspects of experimental investigations of laser plug ignition use at spark ignition engine

Nowadays, the necessity of pollutant emissions reduction brings to the fore new technologies developed for a better control of the combustion process. Ignition is the process of starting radical reactions until a selfsustaining flame has developed and strongly affects the formation of pollutants. Among the new technologies used for ignition and combustion control, the Laser Plug Ignition system is defined as an innovative technology which overcomes several limitations of conventional spark ignition. Laser ignition technology presents many advantages for engine operating control, engine performance improvement and pollutant emissions reduction. The objective of the paper is the experimental research of the laser ignition used in the spark ignition engine. The laser plug ignition system was mounted on an experimental spark ignition engine and tested at the regime of 90% load and 2800 rpm and dosage, λ = 1. The experimental results present the influence of laser ignition on different engine parameters compared to electric spark ignition. The influence on in-cylinder pressure, heat release rate, engine efficiency and pollutant emissions level is analyzed. Compared to a conventional spark plug, a laser ignition system assures efficient engine operation at lean dosages.

Usage of glycerin-derived, hydrogen-rich syngas augmented by soybean biodiesel to power a biodiesel production facility

A single-cylinder compression ignition engine undergoing dual-fuel operation with soybean biodiesel and an artificial hydrogen-rich syngas (postulated from glycerin reformation) was tested at varying engine loads and gaseous/liquid fuel flowrates. Overall, increasing syngas usage promotes premixed combustion, with only relatively small deviations in injection timing required to maintain efficient engine operation. Fuel consumption increased while emissions of particulates fell with greater syngas usage due largely to a shift to flame propagation-controlled combustion. Increases in nitrogen dioxide emissions are tied closely to syngas usage, and composed an unusually large portion of all nitrogen oxide emissions via greater levels of flame quenching. The experimental results are combined with an energy analysis of a biodiesel production process in order to determine the amount of glycerin (subsequently converted to a syngas) and biodiesel required for a small-scale plant to be self-sufficient. Calculations indicate that only 10.88% of the glycerin by-product generated and 3.65% of the biodiesel produced by the facility is needed to provide all of the plant's energy requirements.