Abstract
This paper presents the optimum energy conversion conditions of stationary photovoltaic panels used for electrical power generation. The results are arrived at after performing calculations for 180 days in a given year at the latitude of St. John’s, Newfoundland. The latitude of this city is close to other Canadian major population centers. Various angular orientations of sun’s rays on the earth are considered. On a given day, the incident energy flux of sun is resolved into three components, and the conversion efficiency is based on the flux normal to the panels. The efficiency of conversion of the incident energy is measured with respect to a solar tracking process. The numbers of days in a given year are divided into two groups – one between the winter solstice and the spring equinox, and another between the spring equinox and the summer solstice.
The results show the existence of two maxima, one for each of the two periods. By setting the panels at each of these maxima, very significant improvement in energy conversion can be achieved.
Article Outline
Nomenclature
1. Introduction
2. Theoretical considerations
3. Results and discussions
4. Conclusions
References
Monday, May 11, 2009
Solar-powered cooling systems: Technical and economic analysis on industrial refrigeration and air-conditioning applications
Abstract
In the last years, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the technologies which allows to obtain, by using the renewable solar source, an important energy saving compared to traditional air conditioning plants. The paper describes different technical installations for solar cooling, their way of operation, advantages and limits. The objective of the present study has been to analyze the technical and economic feasibility of solar absorption cooling systems, designed for two different application fields: industrial refrigeration and air conditioning. The possibility to replace or integrate the existing plants is studied, by considering the refrigeration requirements of a company, which works in meat manufacturing, and the heating and cooling demands of a hotel located in a tourist town in Italy. In the first case, the system comprises an absorption chiller coupled to solar flat plate collectors, whereas the second application is about a hybrid trigeneration plant, known as thermo-solar trigeneration; this option allows having greater operational flexibility at sites with demand for energy in the form of heating as well as cooling, for example in a hotel. In this way the authors could compare different results obtained by a technical and economic experimental analysis based on existing users and evaluate the advantages and disadvantages in order to suggest the best solution for the two studied cases.
Article Outline
Nomenclature
1. Introduction
2. Technologies
2.1. Solar cooling
2.2. Thermo-solar trigeneration
2.3. State of the art
2.4. Financial aspects
3. First case study: industrial refrigeration
3.1. Installations
3.2. Plant design solutions
3.3. Technical and economic feasibility
4. Second case study: hotel users
4.1. Installed plants and recorded consumptions
4.2. Plant solution, technical and economic feasibility
5. Conclusions
Acknowledgements
References
In the last years, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Solar-powered cooling is one of the technologies which allows to obtain, by using the renewable solar source, an important energy saving compared to traditional air conditioning plants. The paper describes different technical installations for solar cooling, their way of operation, advantages and limits. The objective of the present study has been to analyze the technical and economic feasibility of solar absorption cooling systems, designed for two different application fields: industrial refrigeration and air conditioning. The possibility to replace or integrate the existing plants is studied, by considering the refrigeration requirements of a company, which works in meat manufacturing, and the heating and cooling demands of a hotel located in a tourist town in Italy. In the first case, the system comprises an absorption chiller coupled to solar flat plate collectors, whereas the second application is about a hybrid trigeneration plant, known as thermo-solar trigeneration; this option allows having greater operational flexibility at sites with demand for energy in the form of heating as well as cooling, for example in a hotel. In this way the authors could compare different results obtained by a technical and economic experimental analysis based on existing users and evaluate the advantages and disadvantages in order to suggest the best solution for the two studied cases.
Article Outline
Nomenclature
1. Introduction
2. Technologies
2.1. Solar cooling
2.2. Thermo-solar trigeneration
2.3. State of the art
2.4. Financial aspects
3. First case study: industrial refrigeration
3.1. Installations
3.2. Plant design solutions
3.3. Technical and economic feasibility
4. Second case study: hotel users
4.1. Installed plants and recorded consumptions
4.2. Plant solution, technical and economic feasibility
5. Conclusions
Acknowledgements
References
Applications of porous media combustion technology – A review
Abstract
The rapid advances in technology and improved living standard of the society necessitate abundant use of fossil fuels which poses two major challenges to any nation. One is fast depletion of fossil fuel resources; the other is environmental pollution. The porous medium combustion (PMC) has proved to be one of the feasible options to tackle the aforesaid problems to a remarkable extent. PMC has interesting advantages compared with free flame combustion due to the higher burning rates, the increased power dynamic range, the extension of the lean flammability limits, and the low emissions of pollutants. This article provides a comprehensive picture of the global scenario of applications of PMC so as to enable the researchers to decide the direction of further investigation. The works published so far in this area are reviewed, classified according to their objectives and presented in an organized manner with general conclusions.
Article Outline
1. Introduction
2. Conceptual background
2.1. Filtration combustion and excess enthalpy
2.2. Premixed and non-premixed combustion
3. Development of PM burners
3.1. Infrared heating
3.2. Patented burners
3.3. Attempts for innovative burners
4. Applications of PMC technology
4.1. IC engines
4.2. Gas turbines and propulsion
4.3. Heat exchangers
4.4. Oil and gas recovery
4.5. Lighting
4.6. Hydrogen production
4.7. Thermoelectric conversion and CHP
4.8. Combustion of low CV fuels
4.9. Solid fuel or powder combustion
4.10. HCl synthesis
4.11. VOC oxidation
4.12. Micro and meso-scale applications
4.13. Liquid fuel combustion (LFC)
4.14. Miscellaneous applications
5. Conclusions
Acknowledgements
References
The rapid advances in technology and improved living standard of the society necessitate abundant use of fossil fuels which poses two major challenges to any nation. One is fast depletion of fossil fuel resources; the other is environmental pollution. The porous medium combustion (PMC) has proved to be one of the feasible options to tackle the aforesaid problems to a remarkable extent. PMC has interesting advantages compared with free flame combustion due to the higher burning rates, the increased power dynamic range, the extension of the lean flammability limits, and the low emissions of pollutants. This article provides a comprehensive picture of the global scenario of applications of PMC so as to enable the researchers to decide the direction of further investigation. The works published so far in this area are reviewed, classified according to their objectives and presented in an organized manner with general conclusions.
Article Outline
1. Introduction
2. Conceptual background
2.1. Filtration combustion and excess enthalpy
2.2. Premixed and non-premixed combustion
3. Development of PM burners
3.1. Infrared heating
3.2. Patented burners
3.3. Attempts for innovative burners
4. Applications of PMC technology
4.1. IC engines
4.2. Gas turbines and propulsion
4.3. Heat exchangers
4.4. Oil and gas recovery
4.5. Lighting
4.6. Hydrogen production
4.7. Thermoelectric conversion and CHP
4.8. Combustion of low CV fuels
4.9. Solid fuel or powder combustion
4.10. HCl synthesis
4.11. VOC oxidation
4.12. Micro and meso-scale applications
4.13. Liquid fuel combustion (LFC)
4.14. Miscellaneous applications
5. Conclusions
Acknowledgements
References
Characterization of trace metals in vegetables by graphite furnace atomic absorption spectrometry after closed vessel microwave digestion
Abstract
A simple and expeditious method for the determination of trace metals (cadmium, chromium, copper, manganese and lead) is proposed. The metals are extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel microwave digestion system for their subsequent detection by graphite furnace atomic absorption spectrometry (GFAAS). The sample preparation procedure facilitates the overall analytical process and enables the construction of calibration curves from inorganic standards. The ensuing method provides good linearity and sensitivity for the five metals, with limits of detection and quantization spanning the ranges 0.05–2.20 and 0.15–7.34 μg/kg, respectively. This sensitivity level is quite appropriate for the intended application. Accuracy was assessed by using a certified reference material (NCS ZC85006 Tomato), for which the proposed method provided amounts of metals consistent with their certified values. The proposed method was applied to tomato, pepper and onion, which are widely consumed in Mediterranean countries.
Article Outline
1. Introduction
2. Experimental
2.1. Instrumentation
2.2. Reagents and chemical standard
2.3. Sample treatment
2.4. Determination procedure
3. Results and discussion
3.1. Effect of experimental variables
3.2. Analytical performance
3.3. Analysis of vegetable samples
4. Conclusions
Acknowledgements
References
A simple and expeditious method for the determination of trace metals (cadmium, chromium, copper, manganese and lead) is proposed. The metals are extracted from their matrix by using nitric acid and hydrogen peroxide in a closed-vessel microwave digestion system for their subsequent detection by graphite furnace atomic absorption spectrometry (GFAAS). The sample preparation procedure facilitates the overall analytical process and enables the construction of calibration curves from inorganic standards. The ensuing method provides good linearity and sensitivity for the five metals, with limits of detection and quantization spanning the ranges 0.05–2.20 and 0.15–7.34 μg/kg, respectively. This sensitivity level is quite appropriate for the intended application. Accuracy was assessed by using a certified reference material (NCS ZC85006 Tomato), for which the proposed method provided amounts of metals consistent with their certified values. The proposed method was applied to tomato, pepper and onion, which are widely consumed in Mediterranean countries.
Article Outline
1. Introduction
2. Experimental
2.1. Instrumentation
2.2. Reagents and chemical standard
2.3. Sample treatment
2.4. Determination procedure
3. Results and discussion
3.1. Effect of experimental variables
3.2. Analytical performance
3.3. Analysis of vegetable samples
4. Conclusions
Acknowledgements
References
Assessing the performance of biogas plants with multi-criteria and data envelopment analysis
Abstract
This paper performs an assessment of 41 agricultural biogas plants located in Austria to determine their relative performance in terms of economic, environmental, and social criteria and corresponding indicators. The comparison of these renewable energy conversion plants is based on two complementary analyses. Data envelopment analysis (DEA) was conducted to provide measures of radial efficiency relative to the observed frontier of production possibilities. Multi-criteria decision analysis (MCDA), using the IRIS/ELECTRE TRI methodology, was conducted to obtain a different perspective on the results, and as a tool that would enable to incorporate managerial preferences easily. To be able to use IRIS while keeping the spirit behind DEA, the evaluation criteria were defined as different output/input efficiency ratios, and no information about criteria weights was introduced at the outset. The results suggest that MCDA, and the use of IRIS in particular, constitutes a useful approach that can be applied in a complementary way to DEA.
Article Outline
1. Introduction
2. Comparison of analytical frameworks
2.1. DEA
2.2. MCDA
3. Case study
4. Results
4.1. Description of the data and parameters used
4.2. DEA
4.3. MCDA
4.4. Comparing the results
4.5. Further analyses with IRIS
5. Discussion and conclusions
Acknowledgements
References
This paper performs an assessment of 41 agricultural biogas plants located in Austria to determine their relative performance in terms of economic, environmental, and social criteria and corresponding indicators. The comparison of these renewable energy conversion plants is based on two complementary analyses. Data envelopment analysis (DEA) was conducted to provide measures of radial efficiency relative to the observed frontier of production possibilities. Multi-criteria decision analysis (MCDA), using the IRIS/ELECTRE TRI methodology, was conducted to obtain a different perspective on the results, and as a tool that would enable to incorporate managerial preferences easily. To be able to use IRIS while keeping the spirit behind DEA, the evaluation criteria were defined as different output/input efficiency ratios, and no information about criteria weights was introduced at the outset. The results suggest that MCDA, and the use of IRIS in particular, constitutes a useful approach that can be applied in a complementary way to DEA.
Article Outline
1. Introduction
2. Comparison of analytical frameworks
2.1. DEA
2.2. MCDA
3. Case study
4. Results
4.1. Description of the data and parameters used
4.2. DEA
4.3. MCDA
4.4. Comparing the results
4.5. Further analyses with IRIS
5. Discussion and conclusions
Acknowledgements
References
Periodic solutions in a delayed predator–prey model with nonmonotonic functional response
Abstract
By using the continuation theorem of coincidence degree theory and some functional analysis techniques, several existence criteria are established for positive periodic solutions of a delayed predator–prey model with nonmonotonic functional response of the form where a(t),b(t),μ(t) and d(t) are all positive periodic continuous functions with period ω>0, τ is a nonnegative constant and g is a nonmonotonic functional response function. And an example is given to illustrate our main result.
Article Outline
1. Introduction
2. Main result
3. An Example
References
By using the continuation theorem of coincidence degree theory and some functional analysis techniques, several existence criteria are established for positive periodic solutions of a delayed predator–prey model with nonmonotonic functional response of the form where a(t),b(t),μ(t) and d(t) are all positive periodic continuous functions with period ω>0, τ is a nonnegative constant and g is a nonmonotonic functional response function. And an example is given to illustrate our main result.
Article Outline
1. Introduction
2. Main result
3. An Example
References
A single stage-structured population model with mature individuals in a polluted environment and pulse input of environmental toxin
Abstract
In this paper, we concentrates on the study of a single stage-structured population model with mature individuals in a polluted environment and pulse input of environmental toxin. A globally attractive condition for the population-extinction boundary periodic solution of the investigated system is obtained. Sufficient criteria on the permanence of the population are derived.
Article Outline
1. Introduction
2. Some important lemmas
3. Global attractivity and permanence
4. Discussion
References
In this paper, we concentrates on the study of a single stage-structured population model with mature individuals in a polluted environment and pulse input of environmental toxin. A globally attractive condition for the population-extinction boundary periodic solution of the investigated system is obtained. Sufficient criteria on the permanence of the population are derived.
Article Outline
1. Introduction
2. Some important lemmas
3. Global attractivity and permanence
4. Discussion
References
Subscribe to:
Posts (Atom)
