Environmental Sciences Commons^™

Enhancing Public Engagement On Offshore Wind Energy Using Genius Loci: A Case Study From A Lake Michigan Coastal Community, Erik Edward Nordman, Daniel O'Keefe, Erika Arndt

Erik Edward Nordman

Oil Contamination In Ogoniland, Niger Delta, Olof Lindén, Jonas Pålsson

Jonas Pålsson

The study shows extensive oil contamination of rivers, creeks, and ground waters in Ogoniland, Nigeria. The levels found in the more contaminated sites are high enough to cause severe impacts on the ecosystem and human health: extractable petroleum hydrocarbons (EPHs) (>10-C40) in surface waters up to 7420 μg L−1, drinking water wells show up to 42 200 μg L−1, and benzene up to 9000 μg L−1, more than 900 times the WHO guidelines. EPH concentrations in sediments were up to 17 900 mg kg−1. Polycyclic aromatic hydrocarbons concentrations reached 8.0 mg kg−1, in the most contaminated sites. The contamination …

Oil Contamination In The Niger Delta, Jonas Pålsson, Olof Lindén

Jonas Pålsson

Oil spills in the Niger Delta region of Nigeria has occurred frequently since oil extraction started in the 1950's. The oil spills originates from facilities and pipelines, leaks from ageing and abandoned infrastructure and from spills during transport and artisanal refining of stolen oil under primitive conditions. It is estimated that spills in Nigeria amount to 100 000 to 200 000 tons per year and have been doing so for almost 60 years. While a number of reports have been written about the Niger Delta and the civil unrest in this area during the last decades, very few scientific reports …

Performance Analysis Of A Rankine Cycle Integrated With The Goswami Combined Power And Cooling Cycle, Ricardo Vasquez Padilla, Antonio Ramos Archibold, Gokmen Demirkaya, Saeb Besarati, D Yogi Goswami, Muhammad M. Rahman, Elias L. Stefanakos

Dr Ricardo Vasquez Padilla

Improving the efficiency of thermodynamic cycles plays a fundamental role in reducing the cost of solar power plants. These plants work normally with Rankine cycles which present some disadvantages due to the thermodynamic behavior of steam at low pressures. These disadvantages can be reduced by introducing alternatives such as combined cycles which combine the best features of each cycle. In this paper, a combined Rankine–Goswami cycle (RGC) is proposed and a thermodynamic analysis is conducted. The Goswami cycle, used as a bottoming cycle, uses ammonia–water mixture as the working fluid and produces power and refrigeration while power is the primary …

Thermodynamic Feasibility Of Alternative Supercritical Co2 Brayton Cycles Integrated With An Ejector, Ricardo Vasquez Padilla, Yen Chean Soo Too, Regano Benito, Robbie Mcnaughton, Wes Stein

Dr Ricardo Vasquez Padilla

Supercritical CO₂ Brayton cycle has emerged as an alternative power block for Concentrated Solar Thermal (CST) systems and nuclear plants. In order to optimise the thermal performance of the Supercritical CO₂ Brayton cycles, a combination of high pressure and temperature are required. The high pressure of the S-CO₂ Brayton cycles has a remarkable effect on not only the thermal performance of the cycle but also the thermodynamic and mechanical performance of the solar receiver. In this paper, three S-CO₂ Brayton cycle configurations without reheat are proposed by introducing an ejector prior the heater, which reduces the …

Exergetic Analysis Of Supercritical Co2 Brayton Cycles Integrated With Solar Central Receivers, Ricardo Vasquez Padilla, Yen Chean Soo Too, Regano Benito, Wes Stein

Dr Ricardo Vasquez Padilla

Concentrated Solar Power (CSP) is a promising alternative for generating renewable energy. One of the most prominent CSP technologies is the central receiver tower with heliostat field, which has received attention in the last decade due to its high achievable temperatures and potential cost reduction. In order to make this technology economically viable, research has been focused on the solar field, solar receiver, energy storage and power block. The power block is one of the important components since improving system efficiency leads to reductions in the storage, solar field and receiver sizes and costs. Recently, supercritical CO₂ Brayton cycles …

An Exergy Analysis Of Recompression Supercritical Co2 Cycles With And Without Reheating, Ricardo Vasquez Padilla, R G. Benito, Wes Stein

Dr Ricardo Vasquez Padilla

Concentrated Solar Power using supercritical CO₂ (S-CO₂) recompression Brayton cycles offer advantages of similar and even higher overall thermal efficiencies compared to power cycles using superheated or supercritical steam. The high efficiency and compactness of S-CO₂, as compared with steam Rankine cycle at the same high temperature, make this cycle attractive for central receiver applications, since both attributes lead to decrease in levelized cost of energy and therefore make this technology economically feasible. The current research in S-CO₂ is focused on thermodynamic analysis and system components. In this paper energy and exergy analyses of …

Experimental Characterization Of Thermal Hydraulic Performance Of Louvered Brazed Plate Fin Heat Exchangers, John Turizo-Santos, Oscar Barros-Ballesteros, Armando Fontalvo-Lascano, Ricardo Vasquez Padilla, Antonio Bula-Silvera

Dr Ricardo Vasquez Padilla

Louvered fins are commonly used in compact heat exchangers to increase the surface area, turbulence, and initiate new boundary layer growth required to improve the heat transfer performance without a significant increase in pressure drop compared with other fins. An experimental study on the air side heat transfer and pressure drop characteristics for a louvered fin with symmetrical patterns in brazed plate heat exchangers had been performed. Reynolds numbers ranged from 350 - 1270, based on the louver pitch while a constant 1.82 m3/h water flow was held. The heat transfer and pressure drop for the geometry tested was reported …

Effect Of Pressure Drop And Reheating On Thermal And Exergetic Performance Of Supercritical Carbon Dioxide Brayton Cycles Integrated With A Solar Central Receiver, Ricardo Vasquez Padilla, Yen Chean Soo Too, Andrew Beath, Robbie Mcnaughton, Wes Stein

Dr Ricardo Vasquez Padilla

Concentrated solar power using supercritical carbon dioxide (S-CO2) Brayton cycles offers advantages of similar or higher overall thermal efficiencies than conventional Rankine cycles using superheated or supercritical steam. The high efficiency and compactness of S-CO2, as compared with steam Rankine cycles operating at the same temperature, make this cycle attractive for solar central receiver applications. In this paper, S-CO2 Brayton cycle is integrated with a solar central receiver that provides heat input to the power cycle. Three configurations were analyzed: simple, recompression (RC), and recompression with main intercooling (MC). The effect of pressure drop in heat exchangers and solar receiver …

Heat Transfer Analysis Of Parabolic Trough Solar Receiver, Ricardo Vasquez Padilla, Gokmen Demirkaya, D Yogi Goswami, Elias Stefanakos, Muhammad M. Rahman

Dr Ricardo Vasquez Padilla

Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer …

Multi-Objective Thermodynamic Optimisation Of Supercritical Co2 Brayton Cycles Integrated With Solar Central Receivers, Ricardo Vasquez Padilla, Yen Chean Soo Too, Regano Benito, Robbie Mcnaughton, Wes Stein

Dr Ricardo Vasquez Padilla

In this paper, optimisation of the supercritical CO Brayton cycles integrated with a solar receiver, which provides heat input to the cycle, was performed. Four S-CO Brayton cycle configurations were analysed and optimum operating conditions were obtained by using a multi-objective thermodynamic optimisation. Four different sets, each including two objective parameters, were considered individually. The individual multi-objective optimisation was performed by using Non-dominated Sorting Genetic Algorithm. The effect of reheating, solar receiver pressure drop and cycle parameters on the overall exergy and cycle thermal efficiency was analysed. The results showed that, for all configurations, the overall exergy efficiency of the …

Exergy Analysis Of A Combined Power And Cooling Cycle, Armando Fontalvo, Horacio Pinzon, Jorge Duarte, Antonio Bula, Arturo Gonzalez Quiroga, Ricardo Vasquez Padilla

Dr Ricardo Vasquez Padilla

This paper presents a comprehensive exergy analysis of a combined power and cooling cycle which combines a Rankine and absorption refrigeration cycle by using ammonia–water mixture as working fluid. A thermodynamic model was developed in Matlab^® to find out the effect of pressure ratio, ammonia mass fraction at the absorber and turbine efficiency on the total exergy destruction of the cycle. The contribution of each cycle component on the total exergy destruction was also determined. The results showed that total exergy destruction decreases when pressure ratio increases, and reaches a maximum at x ≈ 0.5, when ammonia mass fraction …

Analysis Of Power And Cooling Cogeneration Using Ammonia-Water Mixture, Ricardo Vasquez Padilla, Gokmen Demirkaya, D Yogi Goswami, Elias Stefanakos, Muhammad M. Rahman

Dr Ricardo Vasquez Padilla

Development of innovative thermodynamic cycles is important for the efficient utilization of low-temperature heat sources such as solar, geothermal and waste heat sources. This paper presents a parametric analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as the working fluid and produces power and cooling simultaneously. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using solar or geothermal energy. A thermodynamic study of power and cooling cogeneration is presented. The performance …

Analysis Of A Combined Power And Cooling Cycle For Low-Grade Heat Sources, Gokmen Demirkaya, Ricardo Vasquez Padilla, D Yogi Goswami, Elias Stefanakos, Muhammad M. Rahman

Dr Ricardo Vasquez Padilla

This paper presents a parametric analysis of a combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia–water mixture as the working fluid and produces power and refrigeration, while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low-temperature sources such as geothermal and solar energy. Optimum operating conditions were found for a range of ammonia concentration in the basic solution, isentropic turbine efficiency and boiler pressure. It is shown that the …

Automatic Control Strategies For Hybrid Solar-Fossil Fuel Power Plants, Armando Fontalvo, Jesus Garcia, Marco Sanjuan, Ricardo Vasquez Padilla

Dr Ricardo Vasquez Padilla

Solar electrical generating systems are a class of solar energy systems which use parabolic trough collectors (PTC) to produce electricity from sunlight. In order to provide power production, one of the major challenges is to held the collector outlet temperature or steam temperature around of a specified set point by adjusting the flow rate of the heat transfer fluid (HTF) within upper and lower bounds. In some cases, an auxiliary heater can be used to provide heat in absence of solar radiation or during cloudy days. This paper presents a comprehensive study of three control schemes proposed to keep the …

A Biomimetic Approach For Modeling Cloud Shading With Dynamic Behavior, Jesus M. Garcia, Ricardo Vasquez Padilla, Marco E. Sanjuan

Dr Ricardo Vasquez Padilla

Clouds are a complex phenomenon which is the result of a strong interaction between multiple variables. Modeling its behavior through physical principles is a task that requires time and is computationally demanding. One of the main effects caused by clouds are the shadows produced over the earth's surface, a phenomenon inherently complex due its origin. This paper proposes a computationally low-demanding model for imitating (not predicting) the behavior of cloud shading by applying a biomimetic approach. This analogy relays on using a bacterial colony growth behavior. The aim of this paper is to establish a methodology to develop a cloud-shading …

Continuous And Semicontinuous Reaction Systems For High-Solids Enzymatic Hydrolysis Of Lignocellulosics, A González Quiroga, A Bula Silvera, Ricardo Vasquez Padilla, A C. De Costa, R Maciel Filho

Dr Ricardo Vasquez Padilla

An attractive operation strategy for the enzymatic hydrolysis of lignocellulosics results from dividing the process into three stages with complementary goals: continuous enzyme adsorption at low-solids loading (5% w/w) with recycling of the liquid phase; continuous liquefaction at high-solids content (up to 20% w/w); and, finally, continuous or semicontinuous hydrolysis with supplementation of fresh enzymes. This paper presents a detailed modeling and simulation framework for the aforementioned operation strategies. The limiting micromixing situations of macrofluid and microfluid are used to predict conversions. The adsorption and liquefaction stages are modeled as a continuous stirred tank and a plug flow reactor, respectively. …