A Life Cycle Assessment of Biofuel Produced From Waste Cooking Oil

Biofuels have received considerable attention as a more sustainable solution for heating applications. Used vegetable oil, normally considered a waste product, has been suggested as a possible candidate. Herein we perform a life cycle assessment to determine the environmental impact of using waste vegetable oil as a fuel. We present a cradle to fuel model that includes the following unit processes: soybean farming, soy oil refining, the cooking process, cleaning/drying waste oil, preheating the oil in a centralized heating facility and transportation when required. For soybean farming, national historical data for yields, energy required for machinery, fertilizers (nitrogen, phosphorous and potassium), herbicides, pesticides and nitrous oxide production are considered. In soy oil refining, steam production using natural gas and electricity for machinery are considered inputs. Preprocessing, extraction using hexane and post processing are considered. In order to determine a mass balance for the cooking operation, oil carryout and waste oil removal are estimated. During waste oil processing, oil is filtered and water removed. Data from GREET is used to compute global warming potential (GWP) and energy consumption in terms of cumulative energy demand (CED). Mass allocation is applied to the soy meal produced in refining and oil utilized for cooking. Results are discussed with emphasis on improving sustainability. A comparison is made to traditional fuels, e.g., commercial fuel oil and natural gas. The production of WVO as fuel has significantly less global warming potential but higher cumulative energy consumption than traditional fuels. The study should provide useful information on the sustainability of using waste cooking oil as a fuel for heating.

A Hybrid Thermal Management System With Negative Parasitic Losses for Electric Vehicle Battery Packs

Parasitic power requirement is a key criterion in selection of suitable battery thermal management system (TMS) for EV applications. This paper presents a hybrid TMS with negative parasitic requirements, designed by integrating phase change material (PCM) with thermoelectric devices. The proposed system does not require any power consumption to maintain tight control over battery cell temperature during aggressive use and repetitive cycling. In addition, it can recover a portion of waste heat produced during the typical operation of EV battery packs. Commercially available LiFeP04 20 Ah pouch cell has been chosen as a test battery sample for validating the conceptual design presented herein. The commercial battery cells, submerged in a PCM-filled polycarbonate casing, are subjected to a cyclic discharge process to elucidate their heat generation characteristics at 27 °C. Charging and discharging is conducted at 0.5C and 1C, respectively. A thermoelectric circuit is used to recover the heat energy absorbed by the PCM and to convert it to electrical energy. The manuscript further details some of the major findings of this experiment.

Effect of Geometric Configuration and Back Plate Addition in Minichannel Solar Collectors

Minichannel tubes have been successfully integrated into automotive, aerospace and HVAC due to their performance superiority and cost effectiveness. Recently, they have also been introduced in the solar thermal industry for similar reasons. Considering the indirect and limited contact area for heat exchange between absorber and fluid in a conventional solar collector, a minichannel tube has the advantage of providing an absorber surface with large heat transfer area and has less thermal resistance. Due to the method of construction, in many cases, minichannel tubes are separated by a few millimeters from each other, leaving a gap in between tubes that wastes collector area. The addition of a back plate to these minichannel-tube collectors will enhance the thermal output as they together provide a larger surface area for absorption. This effectively increases the thermal output. However, the balance between heat transfer and pumping power needs to be analyzed, thereby the need arises to optimize these geometric parameters. This paper attempts to determine these performance values while optimizing the minichannel-tube geometry and back plate width. From energy analysis, it is deduced that a back plate of 40mm width with the corresponding hydraulic diameter for a constant heat exchange width of 100mm maximizes the thermal performance. The exergy analysis further shows that when the back plate width was between 40mm–45mm, maximum of 73% exergy efficiency can be achieved.

Vibration Energy Harvesting to Power Ultrasonic Sensors in Heavy Haul Railway Cars

Long heavy-haul trains are now a reality, especially for ore transportation. In some railways, compositions of up to 330 wagons are in service, requiring several locomotives. Trains like that travel long distances, sometimes through cities or in uninhabited regions. They are driven by just one driver which must keep the whole train working safely on the track. The wagons don’t have any source of electrical energy to power sensors and to transmit their signals to the locomotive; nor wireless communication. In fact, in some of these railways, there is no internet along with the track out of the cities. One important indicator of the safety of the train is the force between the wagons during the trip, through the shunting. Using strain gauges to measure these forces is a possible solution and ultrasonic stress sensors (UST) is a suitable alternative. UST with Lcr waves requires a low amount of energy and can be employed in rusty and dirty places. However, they also need an energy source. Wind and solar solutions are not always adequate because, unfortunately, there are places where these components have economic value and they can be stolen. A possible source of energy to power the USTs could be the Vibration Energy Harvester (VEH). These simple and not expensive systems can be built in small packs, giving the energy to measure the forces and transmit the data to the locomotive or designated sites along the track. This work aims to evaluate the possibility of using VEH to power USTs to measure the forces between the wagons during the journey. Knowing that the oscillation in the shunting has a very low frequency, the work intent to optimize a multi-beam VEH to be able to capture the highest amount of energy possible, in a very small arrangement, using genetic algorithm. The result shows that VEH is an adequate alternative to power autonomous UST sensors.

Lean-Burn Characteristics of a Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOx, CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

Influence of Façade Area on Thermal Performance of Building for Cooling Purposes

Buildings account for significant energy consumption worldwide particularly in regions where energy patterns influenced primarily by weather. Air conditioning system became an essential evaluation factor during building design and construction. The level of curiosity about air conditioning system efficiency in terms of energy usage is increasing quickly. In Kuwait; which is a hot climate country; air conditioners account for 70% of total electrical power. Electricity in Kuwait is produced entirely by the non-renewable energy resources. This work aims to assess the potential electrical savings that could be acquired by reducing building’s façade area towards East-West directional orientation in Kuwait. For this purpose, a detached building model with uniform geometry; was simulated by Energy Plus Thermal Simulation Engine through its interface with DesignBuilder software. Two cases were developed for the analysis; both have the same simulation inputs. The only difference was the orientation of the facades. The results show a reduction of about 900 kWh cooling annually if the largest facades were positioned towards north and south. The obtained saving in annual basis is attributed to about 420 kWh electrical power. Equivalent CO2 emissions associated with the saved electrical energy from power plants in Kuwait were estimated. The resulted savings are promising for early decision making for prospective buildings to be built in future.

Gaseous Fuel Leakage From Natural Gas Infrastructure

Hydrogen has often been studied as a possible fuel of the future due to its capabilities to support zero emissions and sustainable energy conversion. Hydrogen can be used in a fuel cell to generate electricity at high efficiencies and with zero emissions. In addition, hydrogen can be renewably produced via electrolysis reactions that are powered from otherwise curtailed renewable energy. One possible means of storing and delivering renewable hydrogen is to inject it into the existing natural gas (NG) system and thus decarbonize gas end-uses. The NG system has potential to serve as a storage, transmission and distribution system for renewably produced hydrogen. Despite the potential of hydrogen to reduce the carbon intensity of the NG system, the unique characteristics of hydrogen (low molecular weight, high diffusivity, lower volumetric heating value, propensity to embrittle pipeline materials) has led to justified concerns over the safety of introducing hydrogen blends into the NG system. While many studies have attempted to quantitatively predict leakage rates of hydrogen using classical fluid mechanics theories, such as Hagen-Poiseuille flow, there have been limited studies which quantitatively assess gaseous fuel leakage to support the predictions made from theoretical analyses and computations. In this paper we present a summary of the literature related to gaseous fuel leakage and results from preliminary experiments which support the idea that entrance effects may significantly affect gaseous fuel leakage from practical leak scenarios such as NG fittings, resulting in similar leakage rates between hydrogen and NG.

Towards Net-Zero Energy Buildings: A Case Study in Humid Subtropical Climate

The growing world-wide energy demand and environmental considerations have attracted immense attention in building energy efficiency. Climate zone plays a major role in the process of decision making for energy efficiency projects. In the present paper, an office building located in Melbourne, FL is considered. The building is built in 1961 and the goal is to identify and prioritize the potential energy saving opportunities and retrofit the existing building into a Net-Zero Energy Building (NZEB). An energy assessment is performed and a baseline model is developed using eQUEST to simulate the energy performance of the building. Several possible energy efficiency improvement scenarios are considered and assessed through simulation including improving insulation on the walls and roof, replacing HVAC units and upgrade their control strategies, use of high efficiency lighting, and more. Selected energy efficiency improvement recommendations are implemented on the building model to achieve the lowest energy consumption. It is considered that photovoltaic (PV) panels will be used to supply the energy demand of the building. Simulations are also performed to determine the number of required PV panels and associated cost of the system is estimated. The results from this paper can help with the decision making regarding retrofit projects for NZEB in humid subtropical climate.

Evaluation of Optimal Designs for Hybrid Renewable Energy Systems Specific to Residential Communities in Saudi Arabia

To meet the increasing energy demand and to shave the peak, the Kingdom of Saudi Arabia (KSA) is currently planning to invest more on renewable energy (RE) seeking diversity of energy resources. Through the integration of demand side management measures and renewable energy distributed generation (DG) systems, the study outlined in this paper aims at investigating the potential of hybrid renewable energy systems in supplying energy demands for residential communities in an oil-rich country. The residential community considered in this study, located in the eastern region of KSA, has an annual electrical usage of 1,174 GWh and an electrical peak load of 335 MW that are met solely by the grid. The results of the analyses indicated that the implementation of cost-effective energy efficiency measures (EEMs) reduced electricity usage by 38% and peak demand by 51% as well as CO2 emissions by 38%. While, the analysis of the hybrid systems showed that purchasing electricity from the grid is the best option with a levelized cost of energy (LCOE) of $0.1/kWh based on the current renewable energy market and economic conditions of KSA, RE systems can be cost-effective to meet the loads of the residential communities under specific electricity prices and capital cost levels. This study can assist KSA decision makers establish effective and targeted policies that can facilitate and promote renewable technologies.

Retrofitting Gas Turbine Units Parabolic Trough Concentrated Solar Power for Sustainable Electricity Generation

Shamsl is hybrid solar/natural-gas concentrated solar power (CSP) plants. The plant is also integrated with a booster gas-fired-heaters for steam superheating. In addition to direct fire-heaters to the heat transfer fluid (HTF) for supplying thermal energy during the night or whenever the solar irradiance level is dimmed. However, there is a more sustainable way to avoid power-generation-outages caused by transient weather conditions without a significant plant reconstruction, i.e. integration with gas turbines. In this study, a thermodynamic model of Shamsl integration with gas turbines is developed to investigate the gas turbine capacity and the exergitic efficiency of the supplied gas with and without the gas turbine involvement. The HTF heaters will receive the needed thermal energy from the gas turbines exhaust gases instead of the direct fire-heater (case1). Another potential is replacing the booster fire heaters with the gas turbine system as well. (case2). A parametric study is conducted to determine the size and the requirements of a gas turbine system for the specified power target demand in addition to a feasibility study for the proposed system. The results showed that using two gas turbines for the HTF heater significantly improved the overall efficiency and reduces the CO2 emission. Replacing the booster heater with two gas turbines improves the efficiency up to excess air factor of 2.5.