neutral pH, 215±10°C liquid reservoir (inferred from the analysis of primary liquid fluid inclusions: mean Th of 213°C; 0.2-0.4 wt.% NaCleq.). Relict quartz-adularia-illite alteration occurs at the surface, in the vicinity of the quartz crystals, and in drilleores from the nearby TK-1 exploration well. Repeated movement on the Paeroa Fault uplifted pyroclastic rocks hosting the quartz crystals, but also provided pathways for 'pulses' of hot fluids to move through the system. Quartz precipitation occurred at the edge of the crystals as the reservoir fluids cooled, as indicated by micron-scale alternating CL-dark/CL-bright quartz growth bands, which contain fluid inclusions with Th values of 210-4-40°C. Pressure fluctuations were the likely cause of dissolution, marked by corroded crystal edges, with subsequent precipitation of quartz into open space. SEM-CL imaging shows that the quartz crystals contain healed fractures, which trapped low salinity fluids with Th values of 201:t:6°C. Low-pH fluids in the near-surface setting also rounded the quartz crystals, and coated them with kaolinite and CL- grey amorphous 'silica residue'.

05/01082 Geochemical study of fluids on Lesbos island, Greece Bencini, A. et al. Geothermics, 2004, 33, (5), 637 654. Sixty-five water samples and seven associated gas samples have been collected on Lesbos island. The lithology and structural setting have resulted in two main types of hydrological circulation: a shallow circulation hosting low-salinity cold waters and a deeper one, hosting high-salinity hot waters that often emerge in thermal springs near the coast. The cold waters are characterized by Ca(Mg)-HCO3(SO3) composition, while the thermal waters generally have an Na-C1 composition. The chemical features of the former can be explained by their circulation in the ophiolite-bearing phyllitic basement and volcanic rocks. Waters circulating in the ultramafic layers of the basement are richer in Mg than the waters whose circulation is mainly within marble levels or volcanic rocks. The Na-C1 thermal waters are characterized by salinities ranging from 1910 to 35,700 mg/kg. As indicated by previous hydrogeochemical and isotopic studies, the Na-C1 composition of the thermal waters on Lesbos is the result of mixing between shallow meteoric waters and marine waters. While interacting with the minerals of the geothermal reservoir, the saline waters retain the Na/CI sea water ratio but become enriched in Ca 2+ and depleted in Mg 2+ with respect to sea water. Processes of hydrothermal alteration at depth are activated by a gas phase enriched in COz, which reaches the geothermal reservoir by rising along the deep fractures of the basement. Thermodynamic calculations based on hydrothermal altera- tion processes occurring at the estimated temperatures of the geothermal reservoir (about 120°C) indicate that the thermal waters of Lesbos are in equilibrium with talc and dolomite.

05•01083 Monitoring of geothermal steam moisture separator efficiency Machemer, L. and Jonas, O. Geothermics, 2004, 33, (5), 587-597. A new low emission atmospheric metering separator (LEAMS) was developed by Two-Phase Engineering and Research, Inc. and tested by Sandia National Laboratories in parallel with a cyclone separator at the Coso, California geothermal field. In order to determine the efficiency of the separator, a Jonas, Inc. Particle Monitor was installed in the exhaust from each separator to measure the mass flow rate and size distribution of water droplets exiting the separators. These tests provided semi-quantitative data on the improved separation provided by the LEAMS, as well as verification of the Jonas, Inc. Particle Monitor on geothermal steam systems.

05101084 Producing satellite-derived irradiances in complex arid terrain Perez, R. et al. Solar Energy, 2004, 77, (4), 367 371. This paper describes a methodology to correct satellite-derived irradiances over complex terrain for models that use the visible satellite channel as main input for cloud index determination. Complex terrain is characterized by high reflectance surface and or the juxtaposition of high and low reflectance surfaces (e.g., desert plains and forested ridges). The correction consists of (1) climate dependent post-model clear sky calibration and (2) singularity identification and removal.

05/01085 Research on the generation of electricity from the geothermal resources in Simav region, Turkey K6se, R. Renewable Energy, 2005, 30, (1), 67-79. One of the greatest problems in using renewable energy sources is the great variability of energy level, both in the short and long term. Geothermal energy, by nature, has high availability because the source is not dependent on weather conditions, so it is among the most stable renewable energy sources. Geothermal energy has the potential to play an important role in the future energy supply of Turkey. Although Turkey has the second-highest geothermal energy potential in Europe, electricity generation from geothermal energy is rather low. This study examines the use of geothermal energy in electricity generation and

07 Altemative energy sources (solar energy)

investigates the applicability of the existent geothermal energy resources to electricity generation in the KiJtahya-Simav region, Turkey. The binary cycle is used in the designed power plant for electricity generation from geothermal fluid in which the percentage of liquid is high and which is at lower temperature. In this power plant, R134a is chosen as the secondary fluid, whose boiling point temperature is lower than that of water, and is used instead of geothermal fluid in a second cycle. The thermal efficiency of the designed power plant is measured to be 12.93%.

05101086 Second law assessment of binary plants generating power from low-temperature geothermal fluids DiPippo, R. Geothermics, 2004, 33, (5), 565-586. Binary-type energy conversion systems are typically used to exploit low- temperature geothermal resources. There are many different technical variations of binary plants, including those known as Organic Rankine Cycles (ORC) and proprietary systems known as Kalina cycles. Recent articles in the technical literature claim dramatic efficiency advantages for Kalina cycles over ORCs, thereby providing the motivation for this study. Claims of remarkable superiority for one type of technology relative to another ought to be verifiable by recourse to actual performance data. Since there is now an actual Kalina cycle in operation, it ought to be possible to make a comparison between it and ORC plants that have been in operation for some time. Comparisons between power plants must use an appropriate and consistent thermodynamic basis. It has been shown that the second law of thermodynamics is the best basis for such comparisons. This principle, employing the concept of exergy, is used here to shed light on these claims. A methodology was introduced to render the comparison of plant efficiencies on common input and environmental conditions, even though the plants being compared operate with somewhat different fluid inlet and ambient temperatures.

05/01087 Thermodynamic evaluation of Denizli Kizildere geothermal power plant and its performance improvement Dagdas, A. et al. Energy Conversion and Management, 2005, 46, (2), 245-256. A thermodynamic optimization of the Denizli Kizildere power plant is performed using real data, and some important results are obtained. The optimum flashing pressure is found to be 200 kPa. According to the existing geothermal power plant, 18% power augmentation is provided when the plant operates at this state. In addition, a new flash- binary model is proposed, and the optimum operating pressure is found that makes the power output maximum. In this model, the maximum power is found to be 18,238 kWe. This means that 93.2% more power is obtained than that of the existing plant. Apart from that, the most suitable working fluid is investigated for the binary cycle.

Solar energy

05•01088 A novel hybrid heat pipe solar collector/CliP system-Part 1: System design and construction Riffat, S. B. and Zhao, X. Renewable Energy, 2004, 29, (15), 2217-2233. The process of selecting and designing the major components for a hybrid solar collector/CHP system is described. Particular attention was given to the design of the solar collector and a number of options, including thin membrane heat pipe solar collectors (both 'normal ' and 'artery' types) and hybrid heat pipe solar collectors (both wicked and wickless types), were considered. Performance comparisons were made using theoretical and experimental data and a hybrid solar collector was selected as the best option for the system. Micro impulse-reaction turbine using n-pentane as its working fluid was selected for the system although further work is being carried out on a compressed-gas driven turbo alternator. A prototype hybrid solar collector/CHP system has been constructed and the results of its theoretical and experimental testing are presented in Part II of this paper.

05/01089 A study on luminous efficacy of global radiation under clear sky conditions in Athens, Greece Tsikaloudaki, K. Renewable Energy, 2005, 30, (4), 551-563. The current interest in energy efficient design has led to a demand for methods of predicting daylight availability in buildings. However, basic daylight data, which are the basis of these prediction methods, are not available for most regions of Greece, as well as for many areas worldwide. For that purpose luminous efficacy can be used in order to generate daylight illuminance from solar radiation data, which are much more widely recorded. This paper concentrates on the analysis of global luminous efficacy in Greece under clear sky conditions. The study involves the evaluation of existing models with respect to daylight data recorded in Athens, Greece, as well as the development of new

Fuel and Energy Abstracts May 2005 165

07 Altemative energy sources (solar energy)

luminous efficacy models for global radiation. The study was based on climatic data provided by the National Observatory of Athens during the years 1996-2000 and tested according to CIE. recommendations. The proposed luminous efficacy models were derived by the analysis, correlation and linear regression of the accepted values of measured data. Statistical analysis techniques were used for the assessment of their performance, as well as for the evaluation of the accuracy in predicting global illumination provided by the proposed and the existing models. The new proposed models can offer engineers and researchers a more reliable and accurate approach for estimating the global illumination levels under clear skies. Nowadays, the knowledge of daylight levels is considered highly important in local architecture, the energy conservation and environmental policies in general, particularly in the case of Mediterranean regions, where clear sky conditions dominate.

05101090 A user-friendly procedure to visualize the hourly quantitative performance of daylighting systems Mansy, K. et al. Solar Energy, 2004, 77, (4), 373-380. The paper reports on the academic experience of teaching daylighting to undergraduate architectural students. The case of teaching day- lighting in the architectural professional program at Oklahoma State University is used as a case study. The paper provides a brief survey of the existing design-assisting tools and methods often used, in architectural education, to design and evaluate daylighting systems. These tools are the ones normally found in textbooks that are used to teach regular and/or advanced environmental control courses. As a result of the experimentation with the use of such handy methods in the architectural design studio, a limited benefit was observed. Although these tools can provide a good understanding of the issues and variables that may affect the performance of daylighting systems, students seldom use them in a design studio setting. In contrast, the suggested simplified procedure proved to be user-friendly. It was also found to be capable of visualizing the hourly performance of daylighting systems, and consequently building a comprehensive understanding of the performance of daylighting systems. This hands- on procedure provides quick and meaningful evaluation that can help students to further develop their daylighting designs to meet the predefined goals. The paper does not intend to present a new method of daylighting systems design and/or evaluation. However, it will present a procedure that helped architectural students to visualize, further develop, and comprehensively understand the performance of their daylighting designs.

05101091 CdO/Cu20 solar cells by chemical deposition Hame, Y. and San, S. E. Solar Energy, 2004, 77, (3), 291-294. CdO and CuzO thin films have been grown on glass substrates by chemical deposition method. Optical transmittances of the CdO and Cu20 thin films have been measured as 60-70% and 3-8%, respectively in 400-900 nm range at room temperature. Bandgaps of the CdO and Cu20 thin films were calculated as 2.3 and 2.1 eV respectively from the optical transmission curves. The X-ray diffraction spectra showed that films are polycrystalline. Their resistivity, as measured by Van der Pauw method yielded 10 2-10-3 f~ cm for CdO and approximately 103 f~ cm for Cu20. CdO/Cu20 solar cells were made by using CdO and Cu20 thin films. Open circuit voltages and short circuit currents of these solar cells were measured by silver paste contacts and were found to be between 1-8 mV and 1-4 ~tA.

05•01092 Clear sky and all sky direct luminous efficacies for Florianbpolis, Brazil de Souza, R. G. et al. Energy Conversion and Management, 2005, 46, (3), 361-371. This work presents a characterization of the luminous efficacy of the direct radiation for Florian6polis, Brazil, for which several direct luminous efficacy models available in the scientific literature were evaluated. In the first part of the work, the evaluation was restricted to clear sky conditions. The models evaluated were used with the original coefficients given by their authors and also with local coefficients obtained for Florian6polis, showing their dependence on the local characteristics. None of the models presented significantly better statistics than the others, although one of them, developed by Robledo and Soler, seems to justify better the physical behaviour of the direct luminous efficacy. In the second part of the paper, three models of direct luminous efficacy for all sky types have been evaluated, the first two having been specifically developed for the direct luminous efficacy, whereas and the third was developed for the global luminous efficacy and has been adapted in this paper to characterize the direct luminous efficacy. The statistical evaluation of the three models showed that the last general model has accuracy similar to the two other ones.

05/01093 Daylight and energy performances of a new type of light pipe Canziani, R. et al. Energy and Buildings, 2004, 36, ( l l ) , 1163-1176.

Daylight represents a free source of illumination of building's internal spaces. For the right and optimal use of this resource, in addition to the resort to some simple designing expedients that can be brought back to the practice of 'building in a workmanlike manner ' , it is possible to adopt specific devices able to improve the sunlight captation. Among these devices a class that presents a very interesting compromise between simplicity of realization, costs and daylighting performances is represented by the so-called 'light pipes'. Light pipes usually work by means of a device placed on an external closing element which attends to collect, redirect and in some cases, concentrate or collimate the incident luminous flux, and a device situated inside the environments able to transport the daylight inwards the building and distribute it into the deep zone of the rooms so as to obtain a better illuminance distribution. In this work, a light pipe was proposed equipped with a flat captation system suitable to be integrated in a building's facade, without any protrusion as to the architectural envelope. This system includes: a planar closing element, a sunlight's collecting and deflecting device that optimizes the direction of the incoming solar rays as tile solar position varies, a rectilinear duct with optical properties suitable for the transport of the sunlight and for its introduction into the room that has to be illuminated. The daylighting performances are simulated in different conditions of external illuminance and it is done an assessment of the lighting energy savings in a test room simulating a class room. At the end, some considerations and applying indications useful for the designer are presented.

05/01094 Daylight calculations using constant luminance curves Betman, E. Renewable Energy, 2005, 30, (2), 241-257. This paper presents a simple method to manually estimate daylight availability and to make daylight calculations using constant luminance curves calculated with local illuminance and irradiance data and the all-weather model for sky luminance distribution developed in the Atmospheric Science Research Centre of the University of New York (ARSC). Work with constant luminance curves has the advantage that daylight calculations include the problem's directionality and preserve the information of the luminous climate of the place. This permits accurate knowledge of the resource and a strong basis to establish conclusions concerning topics related to the energy efficiency and comfort in buildings. The characteristics of the proposed method are compared with the method that uses the coefficient:daylight factor.

05/01095 Derivation of efficiency factors for uneven irradiation on a fin absorber Hellstr6m, B. Solar Energy, 2004, 77, (3), 261-267. In the equation for thermal energy output from a flat-plate solar collector (written as a function of the collector mean heat carrier temperature), both the gain and the loss terms are multiplied by the collector efficiency factor, F ' . For a concentrating collector with an uneven (non-uniform) irradiation on the absorber, the efficiency factor for the gain term, here called the optical efficiency factor, Uc, is different from F ' and is a function of the irradiation distribution on the absorber. If the heat loss coefficient is assumed to be constant across the fin, the optical efficiency factor for absorbed irradiation at a certain distance from the edge of the absorber is independent of absorbed irradiation at other locations and can therefore be expressed F'c(x), where x is the distance from the edge of the absorber. Close to the edge, Fc(x) < F' and close to the pipe, F'c(x) > F'. In this paper formulas are derived for calculating F'o(x) for a fin absorber with constant fin thickness. By weighting Flc(x) with the absorbed irradiance, So(x), and integrating across the absorber, an absorber average optical efficiency factor, F'c,a, is obtained. This value replaces F ' in the gain term of the equation for thermal energy output. If, instead, the energy output equation is expressed as a function of the inlet temperature, Uc,a can be used for calculating a corresponding heat removal factor for uneven irradiation, FR.c. Formulas for calculating the temperature distribution across the absorber for the case of uneven irradiation are also derived.

05/01096 Design of a novel passive solar tracker Clifford, M. J. and Eastwood, D. Solar Energy, 2004, 77, (3), 269-280. A novel, low cost solar tracker suitable for use in equatorial regions around the world is presented. The solar tracker is passively activated by aluminium/steel bimetallic strips and controlled by a viscous damper. Computer modelling predicts an increase in efficiency of up to 23% over fixed solar panels. Experimental testing shows excellent agreement with the computer model. In addition, further developments to the design are critically evaluated in terms of complexity and benefit.

05/01097 Efficiency improvements of photo-voltaic panels using a Sun-tracking system AI-Mohamad, A. Applied Energy, 2004, 79, (3), 345-354. This paper presents a sun-tracking design, whereby the movement of a photovoltaic module was controlled to follow the Sun's radiation using a programmable logic-controller (PLC) unit. All electronic circuits and the necessary software have been designed and developed to perform

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