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  • Open access
  • 54 Reads
Small-Scale ORC Energy Recovery System for Wasted Heat: Thermodynamic Feasibility Analysis and Preliminary Expander Design
The paper analyses the thermodynamic feasibility of an innovative Organic Rankine Cycle (ORC) recovery system. Among the many applications of this device, particular interest covers the application as bottoming systems for the exploitation of wasted heat from the exhaust gases of an ordinary ICE.The vehicle thermal source can be either a typical diesel engine (1400 cc) or a small gas turbine set (15-30 kW). The sensible heat recovered from the exhaust gases feeds the energy recovery system that can produce sufficient extra power to sustain the conditioning system and other auxiliaries. The concept is suitable for all types of thermally propelled vehicles, but it is studied here for automotive applications.The characteristics of the organic cycle-based recovery system are discussed, and a preliminary design of the main component, such as expander is presented. The main challenge are the imposed size and weight limitations that require a particular design. A possible system layout is analysed and the requirements for a prototypal application are investigated.
  • Open access
  • 65 Reads
Strategic Analysis Adaptation Assessment: An Alternativeto the Economic Storyline Scenario
Scenarios of future trends are widely used by government and international agencies to inform decision-making. While story line scenarios may be useful for business or government thinking, they are not effective at informing engineering research, innovation and design, and add very little to the understanding of sustainability. This paper presents a strategic analysis approach to complex systems, which relies on identification of risks to important activities and wellbeing. This method mimics the actual processes of anthropogenic continuity, where people explore, experiment, learn from success and mistakes, and adapt and evolve. The method is applied to the case study of transportation fuel supply in New Zealand. Directions for immediate strategic engineering research and innovation are clear outcomes of the analysis.
  • Open access
  • 129 Reads
Negative Triangularity Tokamak as Fusion Energy System
Fusion energy development is quite successful in both getting equivalent energy breakevencondition in large tokamak and clarifying many important physics in the magnetically confinedplasma to proceed to a fusion experimental reactor, ITER. Now, fusion research has to solvethe power handling toward fusion demonstration power reactor (DEMO). A tokamak plasma withstrongly negative triangularity may o er such an opportunity as an innovative concept. Experimentaland theoretical works at CRPP-EPFL shows promising results for negative triangularity tokamak. In this paper, we review the current understanding of such configuration in both physicaland technological aspects.
  • Open access
  • 45 Reads
Demand Response on Pumping Systems of Tall Buildings with Real-time Pricing
Under market environments, electric customers are offered choices to manage and pay for their electricity usage corresponding to the wholesale market price; this can be referred to as demand response. This paper presents a framework for demand response of commercial buildings, particularly applies to the pumping systems of tall (high) buildings. The problem is to control the pumping systems in response to the market price to minimize the electricity charge. The idea is to utilize the water reservoirs on the top as energy storage devices to manage the electricity consumed by the pumping system from on-peak to off-peak hours, at the same time, maintains water level enough for the demand. The problem is formulated and solved by dynamic programming method. Then, it is tested in a case study assuming markets for real-time pricing.
  • Open access
  • 62 Reads
Voila! A New Measure of Oil Vulnerability for Cities
Peak oil, and the ensuing global decline in oil supplies, will adversely affect automobile-dependent personal transport systems. This places users at risk if they are unable to access their activities without oil consumption.This research develops a quantitative spatial measure of oil vulnerability, combining spatial data of vehicle travel with a novel transport energy-accessibility metric, the Minimum Energy Transport Activity Access characterisation (METAA). The measure identifies vulnerable areas as those where greater amounts of oil are consumed for transport, and there is limited potential for adaptation to reduce oil dependence. Areas of lower vulnerability are those in which little oil is currently used or there is significant potential for transport adaptation.This new spatial tool allows planners to analyse where, how and why residents are vulnerable, and identify effective mitigation schemes to reduce the impacts of declining oil supply. The measure also enables categorisation of mitigation schemes, from areas where education programs will be sufficient to reduce vulnerability through to areas where long-term transport and land-use planning present the only viable solutions.The results for Christchurch, New Zealand, indicate that the majority of households are adaptable, although satellite communities and areas on the city fringe are increasingly vulnerable. The research has important implications for urban and transport planning.
  • Open access
  • 49 Reads
Energy Efficiency Through an On-Line Learning Approach for Forecasting of Indoor Temperature
University CEU Cardenal Herrera (CEU-UCH) has constructed a Solar house, known as SMLSystem, to participate in the Solar Decathlon Europe 2012 competition. Such construction becomes a research facility that University employs in order to test innovative solutions around the area of energy efficiency. A lot of technologies have been integrated to help to reduce the overall power consumption of the house. Among them, a predictive system, based on Artificial Neural Networks (ANNs), has been developed using the data acquired in Valencia, where the house is placed. Such system produces short-term forecast of indoor temperature, using as input the data captured by a complex monitoring system. The system expects to reduce the power consumption mainly related to Heating, Ventilation and Air Conditioning (HVAC) systems because of the following assumptions: the high power consumption for which HVAC is responsible (53,9% of the overall consumption); and the energy needed to keep the temperature is less tan the energy required to lower/increase it.This paper studies the viability of the development of such kind of predictive systems but for totally unknown environments, that is, without historical data. To do that it is possible to apply on-line learning approaches, where the model parameters are estimated following Bayesian methods or Gradient Descent (GD) methods, starting from an unbiased a-priori knowledge, or from a totally random model. These forecasting measures could allow the house to adapt itself to future temperature conditions by using home automation in an energy-efficient manner. Preliminary experimental results show a high forecasting accuracy with simple models and with a short training time of 4-5 days. The final idea is to develop intelligent agents, with the minimum resources, to be implemented in very cheap computer architectures.
  • Open access
  • 49 Reads
Monolithic Solar Water-Splitting Systems: Towards a Sustainable Hydrogen-Energy Future
On of challenging routes to convert solar energy in storable fuels is the light-induced water-splitting in hydrogen and oxygen on integrated tandem-systems based on the assembly of stable and efficient semiconducting photoelectrodes. The working of such a system requires a convenient band-alignment of the n- and p-type semiconducting absorbers, which constitute the base for the photoanode and –cathode, respectively, to fulfill the thermodynamic and kinetic reaction requirements. The water-splitting efficiency depends on the individual performance of photoanodes and photocathodes, which in turn depend on (i) efficient light harvesting including the excess photonic energy, (ii) low recombination losses and (iii) high electron transfer rates of photo-generated minority charge carriers at the different generated materials interfaces. These preconditions are pursued in a system consisting essentially of electro-catalytic centers embedded in a passivated semiconductor substrate having an extremely low concentration of surface reaction sites. Condition (i) requires high absorptivity of the semiconducting material, whereas condition (ii) requires control of the electronic properties of the various interfaces and (iii) implies a better understanding and steering of the electro-catalytic process occurring at the surface of reactive centers that convert sunlight directly to fuels. After an introductory part in the main electronic und energetic aspects of the conversion process in these type of systems, preliminary and model experiments concerning the use of silicon and technologically advanced IV and III-V semiconductors for halfcell configurations are presented. The future implementation of surface modified materials into tandem structures is discussed and future directions concerning the exploitation of photonic effects at metal arrangements of plasmonic materials and the implementation of bio-electrocatalysts in advanced devices is outlined.
  • Open access
  • 61 Reads
The Potential of Tandem Photovoltaic Solar Cells for Indoor Applications
Several studies have already determined the power potential of different types of solar cells for indoor applications. However, a detailed study whether or not the use of tandem solar cell (i.e. using two solar cells with different bandgaps in a row) is beneficial for indoor use is lacking. This paper attempts to fill this lacuna by comparing the power output of different tandem solar cells with single-junctions as reference. The comparisons are done by efficiency simulations based on the quantum efficiencies of the solar cells and the light spectra of typical artificial light sources, i.e. different types of fluorescent tubes, a high pressure sodium and metal halide lamp, a cool and warm LED lamp and a common incandescent and halogen lamp, which are compared to the outdoor AM1.5 spectrum as reference. More specifically, we study the influence of the energy levels of the bandgaps, as well as different absorption windows of the subcells. We not only study the light harvesting potential of the usual monolithic configuration, but also consider a stacked set-up. By determining the relative efficiency gain compared to single-junctions, we prove the limited usefulness of tandem solar cells for indoor applications and determine the acceptable range of bandgaps and absorption windows of the subcells for the different indoor environments.
  • Open access
  • 34 Reads
Production of a Biofuel that Keeps the Glycerin as Monoglycerides by Using Supported KF as Heterogeneous Catalyst
This study describes results obtained in the synthesis of a biofuel that integrates glycerol by applying a heterogeneous process where supported KF is employed as alkaline catalyst. Thus, the catalytic performance of KF supported at 10 wt %, on three different solid supports, Al2O3, ZnO and MgO, was investigated in the transesterification process of sunflower oil with methanol. In this respect, the standard experimental conditions employed in the heterogeneous methanolysis reactions were 12 mL of sunflower oil, 2.7 mL of methanol, 0.8 g of catalyst, at 65 ° C temperature during 1 hour. In all cases were obtained 100% conversion, with high selectivity values greater than 90%, as well as quite suitable viscosity values, 4.5 - 8.5 cSt. However, the best catalytic behavior was obtained by using Al2O3 as support. It has been also evaluated the influence of the catalyst weight by using variable amounts of KF/Al2O3 (0.2, 0.4, 0.6, 0.8, 1 g), as well the influence of the oil / methanol molar ratio (1/3, 1/4, 1/5, 1/6 and 1/7) with a fixed quantity of catalyst KF/Al2O3 (0.8 g) and operating at 65 °C of temperature during 1 hour. These three heterogeneous supported catalysts have resulted to be quite suitable to stop the transesterification of triglycerides (TG) with methanol in the second step, so that one molecule of TG generates two moles of fatty acid methyl esters (FAME) and one of MG, working under heterogeneous conditions, at atmospheric pressure, with oil / methanol molar ratio (1/5) and temperatures in the range of 50-65 °C. Thus, a new biofuel similar to conventional biodiesel applicable to diesel engines is obtained under sustainable experimental conditions, which avoiding glycerol production, not only minimizes waste generation but also maximizes efficiency of the process.
  • Open access
  • 62 Reads
Preparation and Characterization of Biodiesel from Karanja Oil by Using Silica Gel Reactor
The oil extraction and biodiesel preparation from Karanja oil have different available methods namely acid catalyzed trans-esterification, acid catalyzed two-step and three-step method etc. The available methods were studied for biodiesel preparation from Karanja oil. The biodiesel prepared by esterification reaction may contain some moisture which may causes to slowdown the reaction rate and affects on the quality of biodiesel by making emulsion.  The adsorption technique by using powder form of silica gal has been used in the reactor to improve the reaction rate. The data has been collected at the time of silica gal dosing and the amount of silica gel dosed for every reaction to optimize it. The optimum dosing condition were recorded by selecting the best dosing properties of biodiesel like specific gravity, free fatty acid (FFA) and viscosity etc. The properties of biodiesel namely specific gravity, viscosity, lower calorific value, cetane number, FFA, flash point, pour point, cloud point, iodine value and saponification value etc. have been carried out at optimum reaction condition by maintaining different ASTM standards and compared with the conventional diesel fuel and standard biodiesel.
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