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[en] A procedure for assessing the techno-economic viability of solar thermal systems in a dynamic economic environment is developed. It is shown analytically that the period for replacement of these systems depends upon the nature of their use. While determining investment viability, it is necessary to ascertain the exact life of the system. The life of a solar thermal system for non-commercial use is determined by optimum life for replacement, which is not influenced by energy inflation and energy saved. It is a function of maintenance cost and decreases with increases with increase in maintenance cost. For commercial purposes, the lifetime of the system is governed by optimum return on investment mode (Ζ), which is a strong function of energy inflation and energy saved per unit capital cost. (author)
[en] Highlights: • An irreversible solar-driven heat engine is optimized. • Developed multi objective evolutionary approaches is used. • Power output, ecological function and thermal efficiency are optimized. - Abstract: The present paper illustrates a new thermo-economic performance analysis of an irreversible solar-driven heat engine. Moreover, aforementioned irreversible solar-driven heat engine is optimized by employing thermo-economic functions. With the help of the first and second laws of thermodynamics, an equivalent system is initially specified. To assess this goal, three objective functions that the normalized objective function associated to the power output (F_P) and Normalized ecological function (F_E) and thermal efficiency (η_t_h) are involved in optimization process simultaneously. Three objective functions are maximized at the same time. A multi objective evolutionary approaches (MOEAs) on the basis of NSGA-II method is employed in this work
[en] Hourly DNI data from the Australian Bureau of Meteorology over 8 years have enabled analysis of implications for solar thermal power generation systems. Six sites were selected, mostly in central Australia and the occurrence and duration of gaps in the availability of energy inputs to solar thermal generation were tallied. In a three month period late in 2010 12 periods of three or more days with an overall average DNI of 2.3 kWh/m2/day occurred. The relationship between DNI and solar thermal generation efficiency was examined and this indicated that on many more days power output would have been very low or zero. The relation between daily total DNI and hourly average DNI was also found to be important, as a high total might be made up of many hours in which DNI was too low for significant generation. These two factors show that there is a significant problem of intermittency for solar thermal systems. Although the annual output of each plant may be commercially viable a solar thermal system might not be capable of meeting demand reliably. - Highlights: • Australian Bureau of Meteorology data were examined regarding DNI patterns. • Gaps in availability of solar energy were identified. • The occurrence of low hourly DNI was examined. • Implications for the reliability of solar energy were drawn
[en] This communication introduces the basic concepts for techno-economic feasibility assessment of various solar thermal systems in a dynamic and market oriented economic environment. An analytical expression for calculating the payback period is derived by assuming a non-linear increase in maintenance cost and incorporating subsidy and salvage values. Further, a method is evolved to ascertain the lifetime of the system for an optimal return on investment mode, incorporating capital inflation during the lifetime and a non-linear increase in maintenance cost. The results for the payback period have been used, along with the lifetime, to optimize the cost of the system. (author)
[en] This paper discusses the present state and the future potential of solar thermal and photovoltaic (PV) technologies, and examines both the environmental implications of these technologies and the economics which determine their viability in the energy market. Although some significant cost reductions have been achieved, particularly in PV technology, solar conversion technologies are still not generally competitive against conventional fuels, and future cost reductions may be limited. It is argued that fiscal measures will be necessary if solar conversion technologies are to make a significant global impact. (Author)
[en] Highlights: • Thermal engine with a double-tube structure is developed for underwater glider. • Isostatic pressing technology is effective to increase volumetric change rate. • Actual volumetric change rate reaches 89.2% of the theoretical value. • Long term sailing of 677 km and 27 days is achieved by thermal underwater glider. - Graphical Abstract: - Abstract: Underwater glider is one of the most popular platforms for long term ocean observation. Underwater glider driven by ocean thermal energy extends the duration and range of underwater glider powered by battery. Thermal engine is the core device of underwater glider to harvest ocean thermal energy. In this paper, (1) model of thermal engine was raised by thermodynamics method and the performance of thermal engine was investigated, (2) thermal engine with a double-tube structure was developed and isostatic pressing technology was applied to improve the performance for buoyancy driven, referencing powder pressing theory, (3) wall thickness of thermal engine was optimized to reduce the overall weight of thermal engine, (4) material selection and dimension determination were discussed for a faster heat transfer design, by thermal resistance analysis, (5) laboratory test and long term sea trail were carried out to test the performance of thermal engine. The study shows that volumetric change rate is the most important indicator to evaluating buoyancy-driven performance of a thermal engine, isostatic pressing technology is effective to improve volumetric change rate, actual volumetric change rate can reach 89.2% of the theoretical value and the average power is about 124 W in a typical diving profile. Thermal engine developed by Tianjin University is a superior thermal energy conversion device for underwater glider. Additionally, application of thermal engine provides a new solution for miniaturization of ocean thermal energy conversion.
[en] The global attention has always been focused on the adverse environmental impacts of conventional energy sources. In contrast nonconventional energy sources, particularly the renewable ones, have enjoyed a 'clean' image vis a vis environmental impacts. The only major exception to this general trend has been large hydropower projects; experience has taught us that they can be disastrous for the environment. The belief now is that minihydel and microhydel projects are harmless alternatives. But are renewable energy sources really as benign as is widely believed? The present essay addresses this question in the background of Lovin's classical paradigm, which had postulated the hard (malignant) and soft (benign) energy concepts in the first place. It critically evaluates the environmental impacts of major renewable energy sources. It then comes up with the broad conclusion that renewable energy sources are not the panacea they are popularly perceived to be; indeed in some cases their adverse environmental impacts can be as strongly negative as the impacts of conventional energy sources. The paper also dwells on the steps we need to take so that we can utilise renewable energy sources without facing environmental backlashes of the type we got from hydropower projects. (Author)
[en] Highlights: • A novel solar driven multi-stage bubble column humidifier is developed and tested. • Single stage, two stage, and three stage configuration were tested. • Average day round absolute humidity is increased by 9% for 2 stage configuration. • Average day round absolute humidity is increased by 23% for 3 stage configuration. • Air absolute humidity increases up to 26% with the integration of Fresnel lens. - Abstract: In this study, a novel solar heated multi-stage bubble column humidifier is designed and tested. The overall objective of this work is to investigate the main operating parameters of the new humidifier. The study addresses the significance of the perforated plate geometric features, optimum balance of air superficial velocity and water column height, and the influence of inlet water temperature and inlet air relative humidity on the performance of the humidifier. The day round performance of the humidifier is investigated in single stage, two stage, and three stage configuration, in which each configuration was tested with and without the integration of the Fresnel lens. Findings show that the average day round absolute humidity, without Fresnel lens, increased up to 9% for the two stage configuration and 23% for the three stage configuration as compared to the single stage configuration of the humidifier. The integration of the Fresnel lens further increased the absolute humidity up to 25% as compared to the results obtained without the integration of the Fresnel lens under the same prevailing conditions, which is significant. Moreover, the current humidifier shows a higher humidification efficiency in the climatic conditions that have a lower inlet air relative humidity. Furthermore, the finding demonstrates that the newly developed multi-stage bubble column humidifier has better performance as compared to the conventional single stage bubble column humidifier. The findings from this study are of pivotal importance to understand the optimum operating conditions of the humidifier for its possible integration with the dehumidifier. Consequently, an improved humidification-dehumidification desalination system attained.
[en] Solar Thermal water heating has made little market penetration in some European countries. The main barriers to market development are: Long payback periods for the technology; Difficulties for the end-user in meeting the initial capital costs of the installation; Lack of confidence in the delivered energy that can be expected from the technology. The third barrier has been addressed using the concept of Guaranteed Solar Results (GSR). This project has addressed the other two main barriers using the concept of Solar Results Purchasing, (SRP) which combines GSR with Third Party Financing. The work was carried out in the UK, France, and Spain. The project used a uniform approach across the three countries. Each team calculated solar performance using an English version of the SOLO programme developed by TECSOL in France to encode the methodology for GSR model contracts. (author)
[en] This paper presents the results of a case study of applying a systematic and proven process of technology portfolio planning with the use of scenario analysis to renewable energy developments in Taiwan. The planning process starts with decision values of technology development based on a survey of society leaders. It then generates, based on expert opinions and literature search, a set of major technology alternatives, which in this study include: wind energy, photovoltaic, bio-energy, solar thermal power, ocean energy, and geothermal energy. Through a committee of technical experts with diversified professional backgrounds, the process in this study next constructs three scenarios ('Season in the Sun', 'More Desire than Energy', and 'Castle in the Air') to encompass future uncertainties in the relationships between the technology alternatives and the decision values. Finally, through a second committee of professionals, the process assesses the importance and risks of these alternative technologies and develops a general strategic plan for the renewable energy technology portfolio that is responsive and robust for the future scenarios. The most important contributions of this paper are the clear description of the systematic process of technology portfolio planning and scenario analysis, the detailed demonstration of their application through a case study on the renewable energy development in Taiwan, and the valuable results and insights gained from the application.