Results 1 - 10 of 144
Results 1 - 10 of 144. Search took: 0.023 seconds
|Sort by: date | relevance|
[en] The use of ocean thermal energy conversion (OTEC) to generate electricity is one of the methods proposed to utilize renewable energy and to protect the environment. In this study, simulations were performed to investigate the effect of weather conditions in the Ulsan region, Korea, on the efficiency of a solar heating OTEC (SH OTEC) system. This system utilizes solar thermal energy as the secondary heat source. Various working fluids were also simulated to select one that is suitable for this system. The results showed that R152A, R600, and R600A, in that order, were the most suitable working fluids. The effective area of the solar collector for a 20 .deg. C increase in the collector outlet temperature fluctuated from 50 to 97m'2' owing to the change in the monthly average solar gain. The annual average efficiency of the SH OTEC increases to 6.23%, compared to that of a typical conventional OTEC, which is 2-4%
[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] Within this publication a detailed overview about the national and international solal't1lel1nai standards is made. The various tests are described and a cross reference list for comparing the different standards is given. Moreover a certification model is presented and the advantage of third party assessment is carried out. The requirement for a solar thermal test laboratory to conduct independent third party assessment by means of an ISO/IEC17065 accreditation is given. Finally the concept of a quality system for solar thermal markets is explained and major advantages are outlined. Solar thermal systems and their components are described in various national and international standards. In Europe the standard EN12975 defines the regulations and requirements for solar thermal collectors. The standard EN12976 is established for the evaluation of factory made solar thermal systems. The EN12977 is the state of the art standard for the evaluation of custom build systems. Nowadays in Libya the standard ISO9806 for solar collectors and the standard ISO9459 for domestic water heating systems define the regulations and requirements for solar thermal collectors and systems. In the meanwhile, empowered Center for Renewable Energy and Energy Efficiency Certification Body is under construction. This body is working now to set the minimum requirements of the testing facilities of solar thermal systems. The international standard for collector testing is the ISO9806 and the standard ISO9459 Part 2, 4, 5 for domestic water heating systems. Within the year 2013 a revision of the ISO9806 will be published and, for the first time, a consistent harmonized standard for the main solar thermal markets will be set in force. Besides the various standards for solar thermal products a meaningful element for the quality assurance and the customer protection is third party certification. Third party certification involves an independent assessment, declaring that specified requirements regarding a product are fulfilled. In a certification process based on specified certification rules an authorized certification body is confirming that a solar thermal product has passed performance tests, reliability tests and further requirements according to the standards. In Europe a certification body holds an accreditation according to EN45011. At international level the standard ISO/IEC17065 is in force. Test results as a basis for product certification are determined by solar thermal test laboratories. The implementation and the business operation of such a solar thermal test laboratory is an important element within the national/regional solar thermal market. To ensure the quality of the products and to attend the role of an observer on the market, the test facility has to fulfill a number of requirements. Besides the necessary technical equipment and the implementation of tests in accordance with the various national and international standards, the laboratory shall realize a quality management system to guarantee the quality of tests and services. Based on the technical equipment, the testing scope and an implemented Quality Management System (QMS), the test laboratory can achieve an accreditation according to ISO/IEC17025 as basis for independent third party testing. Independent testing and evaluation of solar thermal collectors and components like hot water stores and controllers offers an important medium for quality assurance. To guarantee a high degree of product quality and consumer protection a quality system for the solar thermal market is necessary. Core of the quality assurance of a functioning solar thermal market are the national standards body, which is developing standards and regulations as a working basis ill technical committees, the national metrology institute that guarantees the traceability of measurements on fundamental and natural constants, and finally the national accreditation body which ensures the conformity of the various actors to a specific standard. Laboratories work closely with the certification authorities and apply the developed specific norms and standards. The certification bodies must ensure the conformance of their test laboratories with the standard ISO/IEC17025, which include the quality standard ISO 9001:2008 and also include additional requirements. The traceability of the metrics of solar thermal testing laboratories is usually made with the help of calibration laboratories that are specialized on certain measurements. Those are also accredited and ensure the traceability of their measurements to the national meteorology institute. Other stake holders are the group of importers and exporters and foreign investors who are on the national market in entrepreneurial activities, as well as the group of consumer organizations that represent the interests of customers. By means of good networking of stake holders and focusing 011 the quality process, a high-quality and flourishing solar thermal market can be created.(author)
[en] Under the current macro-economic trends, the so far abundant support system for renewables (mainly in the form of feed-in tariffs and quota systems) has been drastically modified. In many EU countries, companies are trying to find alternative ways to secure financing for their renewable energy projects. Therefore, new ways of attracting private capital for the realisation of green energy goals have to replace the old schemes. Some new forms of financing are coming together with the EU Cohesion Policy 2014-2020 (project guarantees, packaging of small project for micro-financing schemes at the regional level, preferential loan instead of subsidies etc.). Advanced financial structures are likely to play an increasingly important role in the allocation of risk and reward among different investor classes. The finance and investment gap needs to be filled by the private sector. The challenge is to identify the appropriate policy options and financial tools to attract and scale-up private investments. There are, however, already innovative and promising business and financial models to promote the deployment of RES in the EU. The aim of the EurObserv'ER case studies is to find such examples and describe them so as to put forward the best practices and the replicability of the future promising financing mechanisms. EurObserv'ER will aim at choosing only the most promising ones and try to describe them in order to promote replicability in other geographical areas. The selection criteria for the choice of case studies should ensure (i) diversity across regions and RES, (ii) diversity across finance instruments/mechanisms, (iii) success of approach and its potential to be replicated, (iv) and a wide range of the 'size' of actors/ investors and the resulting RES investments (capacity). The current selection also takes into account the fact that there were already some case studies published in the 2014 and 2015 barometers. These are also available for download on the project website: www. eurobserv-er.org
[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] The French Environment and Energy Management Agency (ADEME) manages a fund dedicated to new energy technologies. Since 2008 this fund has funded 'research demonstrators' to implement testing of technologies that are in an experimental stage, between research and industrial deployment. ADEME coordinates a group of experts who are charged with drawing up a strategic road-map prior to each Call for Expressions of Interest. The aims of the solar thermal road-map are: - to highlight the industrial, technological, environmental and societal issues at stake; - to elaborate coherent, consistent and shared visions of the technologies and/or socio-technical systems outlined in the road-map; - to underscore the technological, organisational and socioeconomic barriers and bottlenecks to be overcome in order to achieve these visions; - to link priority research topics to a timetable of goals for technology availability and deployment that is consistent with the stated objectives; - to give priority to research needs and research demonstrators that will serve as the basis for: 1 - calls for expression of interest issued by the Research Demonstrators Fund, 2 - the research programming process at ADEME and more broadly at the Agence nationale de la recherche (ANR) and the Comite strategique national sur la recherche sur l'energie. Research priorities and needs for demonstrators are determined by the intersection of visions and bottlenecks. They also take into account industrial and research capacity in France. The road-maps may also refer to exemplary research demonstrators abroad that are in the forefront of technological progress, and make recommendations regarding industrial policy. These road-maps are the result of collective work by a group of experts appointed by the Steering Committee (Comite de pilotage, COPIL) of the Research Demonstrators Fund for new energy technologies. The members of this group are actors in research, drawn from industry, research bodies and research funding and programming agencies
[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] In any solar thermal application, such as solar space heating, solar hot water for domestic or industrial use, concentrating solar power, or solar air conditioning, a solar receiver converts incident sunlight into heat. In order to be efficient, the receiver must ideally absorb the entire solar spectrum while losing relatively little heat. Currently, state-of-the-art receivers utilize a vacuum gap above an absorbing surface to minimize the convection losses, and selective surfaces to reduce radiative losses. Here we investigate a receiver design that utilizes aerogels to suppress radiation losses, boosting the efficiency of solar thermal conversion. We predict that receivers using aerogels could be more efficient than vacuum-gap receivers over a wide range of operating temperatures and optical concentrations. Aerogel-based receivers also make possible new geometries that cannot be achieved with vacuum-gap receivers.
[en] 638,4 MWe The CSP plant electrical generating capacity in the EU at the end of 2010 As could be expected, the recession cast long shadows over the European solar thermal market throughout 2010. For the second year running, new installations for hot water production and space heating (collectors) decreased. According to the EurObserv'ER survey the newly-assigned surface area was 3.8 million m2 in 2010, down from 4.2 million m2 in 2009 and 4.6 million m2 in 2008. At the same time, the European high-temperature solar sector related to electricity production has been taking shape alongside the heat-producing applications, with 638.4 MW already installed. Spain accounts for almost all of this capacity, and a further five EU countries, mostly Mediterranean, intend to develop the sector