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Ferreira V.J.,Research Center for Energy Resources and Consumption | Lopez-Sabiron A.M.,Research Center for Energy Resources and Consumption | Royo P.,Research Center for Energy Resources and Consumption | Aranda-Uson A.,University of Zaragoza | Ferreira G.,Research Center for Energy Resources and Consumption
Energy Conversion and Management | Year: 2015

This work addresses the potential environmental effects of thermal energy storage using the life cycle assessment to perform an optimal system framework. The study assesses the recovery of waste thermal energy at medium temperatures through the application of phase change materials and the recovered heat use in other industrial processes avoiding the heat production from fossil fuel. To this end, twenty different situations were analysed in terms of energy and environmentally combining four thermal energy storage systems varying the type of phase change material incorporated (potassium nitrate, potassium hydroxide, potassium carbonate/sodium carbonate/lithium carbonate and lithium hydroxide/potassium hydroxide) which were defined as cases and five scenarios were the heat can be released based on the type of fossil fuel consumed (coal, heavy fuel, light fuel, lignite and natural gas). Moreover, a net zero environmental metric time parameter was calculated to assess the time period in which the environmental impacts associated to the thermal energy system were equal to the avoided impacts by the use of the heat recovered. Values that were lower than the thermal energy system lifetime were obtained in more than 40% of the total study situations. Finally, an additional analysis was performed to identify the most significant parameters for the further development of a mathematical model to predict the net zero environmental metric time. © 2015.


Maraver D.,Research Center for Energy Resources and Consumption | Quoilin S.,University of Liège | Royo J.,University of Zaragoza
Entropy | Year: 2014

This work is focused on the thermodynamic optimization of Organic Rankine Cycles (ORCs), coupled with absorption or adsorption cooling units, for combined cooling heating and power (CCHP) generation from biomass combustion. Results were obtained by modelling with the main aim of providing optimization guidelines for the operating conditions of these types of systems, specifically the subcritical or transcritical ORC, when integrated in a CCHP system to supply typical heating and cooling demands in the tertiary sector. The thermodynamic approach was complemented, to avoid its possible limitations, by the technological constraints of the expander, the heat exchangers and the pump of the ORC. The working fluids considered are: n-pentane, n-heptane, octamethyltrisiloxane, toluene and dodecamethylcyclohexasiloxane. In addition, the energy and environmental performance of the different optimal CCHP plants was investigated. The optimal plant from the energy and environmental point of view is the one integrated by a toluene recuperative ORC, although it is limited to a development with a turbine type expander. Also, the trigeneration plant could be developed in an energy and environmental efficient way with an n-pentane recuperative ORC and a volumetric type expander. © 2014 by the authors; licensee MDPI, Basel, Switzerland.


Maraver D.,Research Center for Energy Resources and Consumption | Royo J.,University of Zaragoza | Lemort V.,University of Liège | Quoilin S.,University of Liège
Applied Energy | Year: 2014

The present work is focused on the thermodynamic optimization of organic Rankine cycles (ORCs) for power generation and CHP from different average heat source profiles (waste heat recovery, thermal oil for cogeneration and geothermal). The general goal is to provide optimization guidelines for a wide range of operating conditions, for subcritical and transcritical, regenerative and non-regenerative cycles. A parameter assessment of the main equipment in the cycle (expander, heat exchangers and feed pump) was also carried out. An optimization model of the ORC (available as an electronic annex) is proposed to predict the best cycle performance (subcritical or transcritical), in terms of its exergy efficiency, with different working fluids. The working fluids considered are those most commonly used in commercial ORC units (R134a, R245fa, Solkatherm, n-Pentane, Octamethyltrisiloxane and Toluene). The optimal working fluid and operating conditions from a purely thermodynamic approach are limited by the technological constraints of the expander, the heat exchangers and the feed pump. Hence, a complementary assessment of both approaches is more adequate to obtain some preliminary design guidelines for ORC units. © 2013 Elsevier Ltd.


Maraver D.,Research Center for Energy Resources and Consumption | Sin A.,Research Center for Energy Resources and Consumption | Sebastian F.,Research Center for Energy Resources and Consumption | Royo J.,University of Zaragoza
Energy | Year: 2013

Biomass CCHP (combined cooling heating and power) systems based on biomass combustion have already demonstrated their benefits in some operating conditions. However, their environmental and energy performance might not always be better than that of conventional stand-alone generation systems. In order to assess the possible benefits, these plants are evaluated by means of Life Cycle Assessment (LCA) methodology to provide some guidelines regarding their environmental feasibility. A thermodynamic model, which considers the integration of different sizes of cogeneration and cooling units, was developed to contribute to properly defining the life cycle inventory stage. Moreover, the model outputs were used to develop a primary energy savings ratio (PESR) analysis and compare its results with those of the LCA.The LCA results show that, whereas small plant cooling-to-heating ratios cause CCHP plants based on biomass combustion to be environmentally feasible (they imply environmental benefits compared to conventional average stand-alone generation), high plant cooling-to-heating ratios in fact cause them to be environmentally unfeasible. Results also allow us to state that the use of the PESR by itself might not be adequate to assess the steady-state performance of this type of plant because, in some circumstances, it might limit the plant's feasibility when environmental benefits could still be achieved. © 2013 Elsevier Ltd.


Zambrana-Vasquez D.,Research Center for Energy Resources and Consumption | Zabalza-Bribian I.,University of Zaragoza | Janez A.,Research Center for Energy Resources and Consumption | Aranda-Uson A.,University of Zaragoza
Journal of Cleaner Production | Year: 2016

At urban level, the generation Municipal Solid Waste and Construction and Demolition Waste is mostly related to the life-cycle of buildings. An evaluation method based on Life Cycle Assessment methodology is presented in this paper to make an analysis of the environmental performance of different life-cycle building waste management strategies in tertiary buildings. As a case study, several waste management strategies considering a tertiary building located in the city of Zaragoza in Spain, are studied. The aim of the case study is to compare the environmental impacts, in terms of Global Warming Potential, of the scenarios proposed focussing on the waste minimisation and avoidance of landfilling of at least 10% for the Municipal Solid Waste generation during a building's use stage, and Construction and Demolition Waste generated during its construction and end-of-life. In case of Municipal Solid Waste, the results show that when a recovery scenario includes energy recovery from the residual fraction of the mechanical-biological treatment plant in the form of Refuse Derived Fuel, greater benefits in terms of the Global Warming Potential are obtained than with current scenarios of landfill deposition of the residual fraction. On the other hand, in case of Construction and Demolition Waste, a similar situation can be observed in case of an increase of the recovery rates of metals. © 2016 Elsevier Ltd.


Maraver D.,Research Center for Energy Resources and Consumption | Sin A.,Research Center for Energy Resources and Consumption | Royo J.,University of Zaragoza | Sebastian F.,Research Center for Energy Resources and Consumption
Applied Energy | Year: 2013

An alternative way of increasing and improving the use of biomass resources and distributed generation is by using combined cooling, heating, and power (CCHP) small-scale plants. The first step in designing a CCHP plant is to determine the best configuration in terms of the thermodynamic integration of all the subsystems and the optimization of the overall energy efficiency. In this work, small-scale biomass CCHP systems are evaluated to provide a basis for studies on their thermodynamic feasibility and energy efficiency in two main sections. First of all, a state of the art review is presented regarding the technologies involved in CCHP systems based on biomass combustion. The conclusion drawn might initially be considered obvious: the best prime mover (PM) technology to develop this type of plant is the Stirling engine (SE) due to its higher electric efficiency, but its low market availability and operational problems currently limit its use in commercial plants. The organic Rankine cycle (ORC) is a very widespread technology but its use in CCHP systems in the power range between 1 and 200kWe is limited due to their low sink temperatures, which prevent its direct cascade integration with thermally activated cooling (TAC) for refrigeration. However, it is possible to integrate these technologies in an energy efficient way (achieving primary energy savings) if the plant is designed according to some guidelines regarding the heating and cooling production. The second section of this work demonstrates this idea by analyzing different possible integrations of the prime movers and TAC units currently available on the market. The overall performance and the energy feasibility, in terms of the relation between the heating and cooling loads, are evaluated through a parameter analysis, using the Artificial Thermal Efficiency (ATE) and the Primary Energy Saving Ratio (PESR). The evaluation of the configurations proposed shows that direct coupling of the PM and TAC units is highly important, more so than high efficiency and coefficient of performance (COP) of the technologies, for achieving primary energy savings in almost every possible relation between the cooling and heating loads generated by the CCHP plant. As a result, some guidelines are proposed to develop small-scale CCHP plants based on biomass combustion in an energy efficient way. © 2012 Elsevier Ltd.


Vicente S.,Lao Institute for Renewable Energy | Bludszuweit H.,Research Center for Energy Resources and Consumption
Renewable Energy | Year: 2012

Lao People's Democratic Republic (Laos) possesses large hydrologic resources, converting hydropower into the most important renewable energy resource in the country. Recently the Lao government, multilateral organizations and NGOs have developed large hydropower projects in tributaries of the Mekong River. These projects usually do not benefit poor people in remote areas where the prevailing source of electricity consists of private pico-hydropower units (<5 kW). These systems face several challenges such as coping with low quality hardware, risk of electrocution and damage to electronic devices and light bulbs. Non-governmental institutions like Lao Institute of Renewable Energy (LIRE) in collaboration with donor funding organizations are seeking to alleviate this situation. These institutions pursue the upscaling and improvement of quality, safety, efficiency and reliability of pico-hydro technology through projects based on the design and implementation of demonstration sites and training programs in rural areas. During the project presented in this work, a feasibility study is carried out to identify a suitable village for the implementation of a demonstration site. Possible locations are analyzed according to social, environmental and technical aspects. For each option, an electric system is designed. For the final selection of the best option, the following design constraints were considered: flexibility, cost effectiveness (to be affordable to poor communities) and easiness of reproduction by people without deep technical knowledge. © 2012 Elsevier Ltd.


Khodr H.M.,Qassim University | Khodr H.M.,Polytechnic Institute of Porto | El Halabi N.,Centro Universitario Of La Defensa | El Halabi N.,Research Center for Energy Resources and Consumption | Garcia-Gracia M.,Research Center for Energy Resources and Consumption
Renewable Energy | Year: 2012

In this paper the optimal operation scheduling of a microgrid laboratory system consisting of a wind turbine, a solar unit, a fuel cell and two storage battery banks is formulated as an optimization problem. The proposed optimization algorithm considers the minimization of active power losses. Due to this type of variable, the problem is formulated as a Mixed-Integer Quadratic Programming model (MIQP) and solved by a deterministic optimization technique implemented in General Algebraic Modeling System (GAMS). This algorithm has been used as Virtual Power Producer (VPP) software to operate the generation units and storage system, assuring a global functioning of all equipment efficiently, taking into account the maintenance, operation and the generation measurement and control considering all involved costs. The VPP software has been implemented in a mini Supervisory Control and Data Acquisition (SCADA) system and controls the microgrid laboratory via Programmable Logic Controllers (PLC) devices. The application of this methodology to a real case study of the laboratory equipment demonstrates the effectiveness of this method for solving the optimal dispatch and online control of a microgrid, encouraging the application of this methodology for larger power systems. © 2012 Elsevier Ltd.


Royo P.,Research Center for Energy Resources and Consumption | Ferreira V.J.,Research Center for Energy Resources and Consumption | Lopez-Sabiron A.M.,Research Center for Energy Resources and Consumption | Ferreira G.,Research Center for Energy Resources and Consumption
Energy | Year: 2016

Growing demands for energy, gradual depletion of fossil resources and high environmental impacts require that current energy production models be replaced by more sustainable technology. Thus, research efforts focused on improving energy efficiency and material efficiency are considered extremely relevant. In the following work, the influence of incorporating PCMs (phase change materials) on electricity conversion efficiency discussed along with hot spot prevention and lifetime increases in BIPV (building-integrated photovoltaics). The main goal is to evaluate the operational temperature control in a BIPV with or without PCMs considering different climatic severities. A design parameter analysis was conducted, and the importance of suitable PCMs and proper system designs are revealed. Also, this study indicates that areas with different climatic severities must be considered for widespread evaluations of this technology application to impact diverse regions. Additionally, an environmental analysis based on the LCA (life cycle assessment) methodology was performed using the SimaPro software. The results show that a positive environmental impact is generated by PCM applications because of the decreased amount of consumed resources in BIPV manufacturing, which is related to the lifetime extension resulting from the ability of PCMs to store latent heat and prevent premature physical damage to the BIPV. © 2016 Elsevier Ltd. All rights reserved.


Carmona M.,Research Center for Energy Resources and Consumption | Cortes C.,Research Center for Energy Resources and Consumption
Journal of Materials Processing Technology | Year: 2014

Tests carried out in an experimental prototype of crucible melting furnace heated by a plasma torch are numerically simulated with a commercial CFD code, in order to calculate melting time, heat losses and temperature distributions in the aluminum load and refractory parts. The objective is to develop a calculating tool to assist in the design and scaling-up of industrial furnaces. Models used are 2D axisymmetric and take into account heat conduction in solid parts, convection in air and molten aluminum, interactions between gas-liquid-solid zones and radiation heat transfer. Fusion of solid aluminum is modeled with the enthalpy method. The simulation is able to predict temperatures and melting times at a reasonable computational expense. Several calculation strategies are tested concerning their computational economy and their accuracy in computing different key parameters. Results show that interactions gas-liquid-solid have an important effect. Firstly, a proper account of heat transfer and losses requires solving the conjugated problem comprising refractory walls and heated load. Secondly, thermal interaction with air cavities seems to determine the convective movement of the molten load and therefore inner-load temperature patterns and their time evolution. Nevertheless, this comprehensive simulation consumes 3.6 times the computational resources of a simplified model, where the momentum equations are not solved for the air cavity and overall furnace parameters are still reasonably predicted (e.g., with an error in fusion time less than 7.3%). © 2013 Elsevier B.V. All rights reserved.

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