bluuebunny/crossref_metadata_2025 huggingface dataset:
A Two-Step Thermochemical Water Splitting by Iron-Oxide on Stabilized Zirconia
Authors: Kodama Tatsuya , Nakamuro Yumiko , Mizuno Takayuki , Yamamoto Ryuji
Published: December 2008

The thermochemical two-step water splitting cycle was examined by using an iron oxide supported on yttrium-stabilized, cubic zirconia (YSZ) as the working material, for the purpose of directly converting solar high-temperature heat to clean hydrogen energy. In the first step of the cycle, the YSZ-supported Fe3O4 was thermally decomposed to the reduced phase at 1400 °C under an inert atmosphere. The reduced solid phase was oxidized back to the original phase (the YSZ-supported Fe3O4) with steam to generate hydrogen below 1000 °C. A new redox pair examined by others was found to serve as the working solid material on this YSZ-supported Fe3O4, as follows. The Fe3O4 reacted with YSZ to produce an Fe2+-containing ZrO2 phase by releasing oxygen molecules in the first step: the Fe2+ ions entered into cubic YSZ lattice. In the second step, the Fe2+-containing YSZ generated hydrogen via steam splitting to reproduce Fe3O4 on the cubic YSZ support. This cyclic reaction could be repeated with a good repeatability of the reaction below 1400 °C.
Hydrogen Production by Solar Reforming of Natural Gas: A Cost Study
Authors: Mo¨ller Stephan , Kaucic Dario , Sattler Christian
Published: December 2008

Today’s production of renewable hydrogen using energy sources such as solar and wind is too expensive compared with conventional production, normally by an order of magnitude. The high costs are a major bottleneck for the launch of the hydrogen economy. This paper will present a bypass of this bottleneck, which is a compromise between the use of fossil and solar energy: the solar steam reforming of natural gas (NG). It comprises the production of hydrogen from NG and the use of solar energy as the renewable source at low cost. Using the solar reformer technology for generation of hydrogen, we expect fuel savings of up to 40% compared to a conventional plant. Therefore, the CO2 emissions can be reduced accordingly. Based on the experiences in DLR solar reformers, which were successfully demonstrated at a level of few hundred kW in previous EC co-funded projects (e.g. SOLASYS), industrial plant layouts were developed. For a 50 MWth solar reforming plant a cost study was prepared. Two process layouts were investigated and the hydrogen costs were calculated. Sensitivity analyses of different parameters such as the natural gas prize were conducted. The conceptual layout of a solar driven hydrogen production plant comprises the innovative solar reformer followed by a water gas shift reactor and gas separation units. For the separation of hydrogen and carbon dioxide a PSA unit and gas washing unit using methyldiethanolamine (MDEA) are considered. The remaining methane rich gas is recycled to the process. The results of this cost study show that hydrogen produced by solar reforming costs between 4.5 and 4.7ct€ / kWh (LHV of H2). Therefore it is only about 20% more expensive than conventionally produced hydrogen. Increasing the cost of methane (NG) will result in favorable conditions for the solar hydrogen.
Dye-Sensitized Photocatalyst System for Water Splitting Into H2 and O2 Under Visible Light Irradiation
Authors: Abe Ryu , Sayama Kazuhiro , Arakawa Hironori
Published: December 2008

H2 production from a water-acetonitrile mixed solution containing iodide electron donor was investigated over dye-sensitized Pt/TiO2 photocatalysts under visible light irradiation, as a part of water splitting system using iodide redox mediator. The rates of H2 evolution were decreased with the increase of the water ratio in the mixed solutions, because of the decrease in energy gap between the redox potential of I3−/I− and the HOMO levels of the dyes, which lowing the efficiency of electron transfer from I− to dye.
Experimental Research on Thermal Performance of Shape-Stabilized Phase Change Material Floor
Authors: Xu Xu , Di Hongfa , Lin Kunping , Zhang Yinping , Yang Rui
Published: December 2008

Experimental study was conducted on the thermal performance and energy saving effect of a room with shape-stabilized phase change material (PCM). The results showed that the mean indoor temperature of the room with PCM floor was about 2°C higher than that of the room with normal floor and the indoor temperature swing range narrowed greatly. The results also manifested that by applying shape-stabilized PCM in room suitably, the thermal comfort level could be raised and space heating energy in winter could be saved. Finally, the experimental results enriched the database for the further modeling and simulation research.
Emission Allowances for Renewable Energy and Energy Efficiency Projects
Authors: Schiller Steven R. , Franconi Ellen , Kumar Satish , Mercado Edgar
Published: December 2008

Allowance trading programs represent an opportunity for the renewable and energy-efficiency industry to capitalize on the environmental benefits associated with their projects. By reducing or preventing emissions, renewable and energy-efficiency projects may qualify for emission allowances that can help sponsors justify their projects. Several federal, state, and international programs are venues for emissions documentation and trading. One program, an energy efficiency/renewable energy set-aside program, is described in this paper. A crucial element of an allowance trading program is the documentation and verification, or evaluation, of actual emission reductions. Thus, this paper also reviews the evaluation process that has been developed for an energy-efficiency and renewable-energy set-aside program and puts the process in context with methods outlined in the International Performance Measurement and Verification Protocol (IPMVP).
Analysis, Design and Testing of an Earth Contact Cooling Tube for Fresh Air Conditioning
Authors: Henkel Joerg , Chen Bing , Liu Mingsheng , Wang Gang
Published: December 2008

Based on a theoretical analysis of small-scale experiments, a 57 m earth contact cooling tube was designed, constructed, and tested to provide cooling for residential buildings and related applications. Warm outside air is drawn through the tube and its heat is absorbed through the tube walls into the surrounding soil. The cooled air then enters the building. Our study investigated cooling performances at different air velocities and soil saturation in test run durations up to 30 days. Experiment results demonstrated that this system could provide up to 1.5 tons of cooling at a flow rate of 1600 cubic meter/hour during hot summer days. This study concluded that earth-cooling tubes are a feasible air-conditioning option for cooling demands in the Midwest, U.S.A. This system requires very little energy. Thus its use is especially interesting in areas where energy generation or supply is problematic. This paper presents the earth contact tube system, structure details of the system, and experiments.
Analysis, Design, and Preliminary Testing of Solar Chimney for Residential Air-Conditioning Applications
Authors: Wang Gang , Chen Bing , Liu Mingsheng , Henkel Joerg , Raulin Stephan
Published: December 2008

A solar chimney is designed and tested to pump outside air through an underground cooling tube during summer for building cooling. Both theoretical analysis and experimental results show that the solar chimney can be used to power the underground cooling system during daytime without use of electricity. This paper presents the theoretical design principals of the solar chimney, detailed experimental facilities, and the experiments results. The impacts of other related parameters, such as building tightness and tube design on the system airflow are also discussed in the paper.
Impacts of Balance Valves on Pump Energy and Control Performance in Variable Water Flow Systems
Authors: Zheng B. , Liu M.
Published: December 2008

There is no common agreement on the use of balance valves in the most popular variable water flow systems. A comprehensive theoretical analysis has been conducted to investigate the impacts of balance valves on initial cost, pump operation power, and system control performance. The investigation finds that eliminating balance valves can (1) reduce 20% to 40% pump energy consumption in a typical variable flow water system; (2) reduce the maximum pressure drop across control valves; and (3) improve pump efficiency at most partial load conditions. The reduced pressure drop across control valves improve system control performance and may allow selecting some of the control valves at lower close-off pressure. Consequently, eliminating balancing valves can also potential reduce system initial costs.
Humidity Control in Confined Building Spaces Using Liquid Desiccant Dehumidifier-Conceptual Investigation
Authors: Dong D. , Liu M.
Published: December 2008

Moisture and moisture-related problems often originate from the confined spaces such as bathrooms and kitchens, where large amounts of moisture are released within a short time period. These problems are identified by signs including condensation on windows and walls as well as mold and fungi growth in corners of interior surfaces of walls and ceiling. To prevent condensation and formations of mold and fungi in the confined spaces, a special desiccant dehumidification system may be used. This system uses ambient space air to regenerate when the spaces produce no moisture. To investigate the feasibility of the desiccant dehumidification system for confined space humidity control, a conceptual system and physical models were developed. Numerical simulations were conducted to calculate simultaneous heat and mass transfer involved among moisture source, space air and liquid desiccant. This paper presents the methods and simulated results. The results show that use of the desiccant dehumidification system can substantially reduce the room humidity level.
Design and Construction of a Compact Air-Cooled Absorption Machine for Solar Energy Applications
Authors: Perez Reisler Rafael A. , Gonza´lez Jorge E. , Sanchez Hector M. , Alva Luis H.
Published: December 2008

This paper presents a methodical procedure for the design and sizing of a compact, water fired, air-cooled absorption chiller. The proposed compact machine uses Lithium-Bromide/Water as absorbent/refrigerant fluid pair. The machine was designed using a detailed heat transfer analysis for each individual component (i.e. desorber, condenser, absorber and evaporator). The condenser uses conventional fin-tube heat transfer surfaces while the evaporator uses an inner corrugated surface to increase the heat transfer area. The generator has a concentric tube arrangement in which the dilute solution is in the inner section and the heating water flows in the outside section. This arrangement results in a regeneration effect at temperatures close to 75°C which can be easily provided with solar collectors. The absorber and evaporator work together as a single unit. The vapor exiting the evaporator comes into thermal contact with the concentrated LiBr solution that enters the absorber from the top and falls inside the vertical tubes, creating the absorption effect. Moreover, air is cooling the outside surface of the tubes removing the heat released during the absorption process. The evaporator was designed to be a falling film evaporator such that when applying the cooling load, condensed water falling on the evaporator tubes evaporates and rises through the vertical tubes of the absorber. A set of highly efficient fans are used to bring outside air to remove the necessary heat in both the absorber and condenser, respectively. Furthermore, all system components have been constructed and assembled into a working prototype of variable cooling capacity between 10.5 to 17.5 kW having final dimensions equivalent to a volume of 5 m3. The preliminary characterization of the thermal performance of this prototype is presented in the paper with the objective of validating the design methodology.
Breaker Chicken With Solar Thermal Storage
Authors: Gordon Manuel , Terres Hilario
Published: December 2008

The design, construction of a chicken incubator with solar thermal storage, and results of the thermal performance are presented. The heating of the indoor air is by thermal storage with paraffin wax situated inside the incubator. Previously the wax is exposed to solar radiation in order to melt it and then it is inserted into the incubator. The solidification of the wax delivers heat to the air inside the incubator at an average temperature that is approximately constant. The biological and thermal processes of incubation in bird raising require relatively little energy of low temperature. The process needs to maintain the eggs at temperatures around 38°C, during almost 21 days. To achieve a chicken born only requires between 250 to 300 W.h. In an incubator insulated adequately, the thermal energy demand increase during the nights, clouded and cold days, and must not be interrupt during at least the first 19 days. Then it is necessary to have some form of energy storage if we do not want or cannot aid the system with a conventional heat source. Paraffinic wax with a melted point of 57°C at normal atmospheric pressure has been cycled in fusion and solidification to store heat in 6 cm diameter cylinders. The surfaces were blackened in order to absorb solar energy, within a solar insulate cabinet and a glass cover. The disadvantage of wax is poor thermal conductivity. Fins embedded into the wax was used in order to eliminate this inconvenience. The fins are aluminum shaving within the cylinders. The quantitative results shown these characteristics: complete change of phase, delivery of latent heat, repeatable behavior over the melting-solidification cycles, good rates of internal heat transfer, and uniform solidification. The analysis of the stored energy, discharged energy, melting time and solidifying time are included.
Optical Durability of Candidate Solar Reflectors
Authors: Kennedy C. E. , Terwilliger K.
Published: December 2008

Concentrating solar power (CSP) technologies use large mirrors to collect sunlight to convert thermal energy to electricity. The viability of CSP systems requires the development of advanced reflector materials that are low in cost and maintain high specular reflectance for extended lifetimes under severe outdoor environments. The long-standing goals for a solar reflector are specular reflectance above 90% into a 4-mrad half-cone angle for at least 10 years outdoors with a cost of less than $13.8/m2 (the 1992 $10.8/m2 goal corrected for inflation to 2002 dollars) when manufactured in large volumes. Durability testing of a variety of candidate solar reflector materials at outdoor test sites and in laboratory accelerated weathering chambers is the main activity within the Advanced Materials task of the CSP Program at the National Renewable Energy Laboratory (NREL) in Golden, Colorado. Test results to date for several candidate solar reflector materials will be presented. These include the optical durability of thin glass, thick glass, aluminized reflectors, frontsurface mirrors, and silvered polymer mirrors. The development, performance, and durability of these materials will be discussed. Based on accelerated exposure testing the glass, silvered polymer, and front-surface mirrors may meet the 10-year lifetime goals, but at this time because of significant process changes none of the commercially available solar reflectors and advanced solar reflectors have demonstrated the 10-year or more aggressive 20-year lifetime goal.
Cost Analysis of Solar Reflective Hard-Coat Materials Deposited by Ion-Beam-Assisted Deposition
Authors: Kennedy C. E. , Swisher R. L.
Published: December 2008

Commercialization of concentrating solar power (CSP) technologies require the development of advanced reflector materials that are low cost and maintain high specular reflectance for extended lifetimes under severe outdoor environments. During the past 9 years, the National Renewable Energy Laboratory (NREL) has funded Science Applications International Corporation (SAIC) in McLean, Virginia, to develop a promising low-cost advanced solar reflective material (ASRM) combining the best of both thin-glass and silvered-polymer reflectors. The alumina (Al2O3) coating is deposited by ion-beam-assisted physical vapor deposition (IBAD). Materials undergoing testing demonstrate excellent durability under accelerated and outdoor weathering. To help commercialize the technology, NREL had a cost analysis performed incorporating realistic web coating assumptions and the technical improvements made in the ASRM. The biggest process cost items are the alumina and machine burden (which collects the cost of the building and office staff). The switch from a polyethylene terethaphalate (PET) to a steel substrate for the ASRM is a significant contributor to the cost. The cost of high-purity alumina should drop from $400/kg to $200/kg when purchased in 20-kg quantities. Alumina deposition rate then becomes the critical cost driver. In a previous study, deposition rates above 100 nm/s were not examined, but deposition rates greater than 100 nm/s are being used routinely for thin alumina coatings deposited on commercial web-coaters as barrier coatings. In addition, multiple (2–3) Al2O3 IBAD zones can be used in one roll-coating machine to deposit thicker alumina at a lower web speed. This means that with increasing deposition rate and/or multiple zones, the total production cost of the SAIC ASRM with 1-μm thick Al2O3 on PET will meet both the 1992 cost goal of $10.76/m2 ($1/ft2) and the equivalent cost goal of $13.79/m2 ($1.31/ft2) when the 1992 cost goal is corrected for inflation. There is a minimum deposition rate needed to reach the cost goal and a maximum deposition rate related to the number of zones after which no significant cost gains are observed. These asymptotic total production costs are $8.06/m2 ($7.39/m2 excluding substrate) for a large commercial web-coating company and $7.62/m2 ($6.94/m2 excluding substrate) for a smaller company. As can be seen by these numbers, the $10.76/m2 cost goal can be reached, but the cost of the substrate is still a major consideration. In addition, the width of the web was increased from 600 to 1200 mm, which decreased the asymptotic total production costs. The results of the cost analysis will be described.
Performance Evaluation of an IC Engine (SI) Using Biogas as Fuel With Petrol Blends: A Case Study
Authors: Masood Md. , Mehdi S. N. , Yousufuddin Syed
Published: December 2008

Biogas is the term used for the gas made from the natural decomposition of Organic (plant or animal) materials. It is Produced when the materials are digested by bacteria in a situation where little or no air is present (anaerobic digestion). Biogas consisting of approximately two-thirds methane (CH4) and one-third carbon dioxide (CO2) burns well and can be used to provide energy in the form of heat or electricity. The main practical sources of biogas are sewage, animal manure and the organic materials in household refuse or industrial waste. Like other renewable energy sources, biogas is a stored form of solar energy (since it originates from plants which used the sun’s energy to grow). An experimental evaluation was carried out to compare the performance of an IC engine (SI) Using Biogas as fuel blended with petrol in different proportions to that of only petrol as fuel. The performance study carried out in a four cylinder SI engine shows that this can better be used as an automotive fuel with a comparatively much lesser cost than the conventional fuels. The results show that because of the low calorific value of biogas the thermal efficiency is lesser than that of petrol and remains same at low and high out puts. Same is the case for volumetric efficiency. Biogas is an excellent and economical fuel for both petrol and diesel engines. However the power obtained is less than that of liquid fuel. Biogas is a cheaper and better fuel for cooking, lighting and running engines.
Natural Climatization of a House Located in a Mild-Rain Climate to Obtain Thermal Comfort
Authors: Morales Jose´ D.
Published: December 2008

Pollution in Mexico City, during almost year round, it is the highest of Mexico, due mainly to the emanations of traffic and industry in addition to the use of gas or firewood heater to condition the interior of the housings and buildings during the winter [1]. The present article shows, that it is possible to use natural ventilation to weathering the interior of a house in a mild-rain climate during the winter, through the use of massive walls, insulation roofs and use the solar radiation through double glass both in windows and in domes of the housing.
Monitoring and Charge-Control of Lead-Acid Batteries in Photovoltaic Applications
Authors: Ortega-Sanchez Cesar , Orozco-Valera Jaime , Pacheco-Arteaga Jojutla , Rivera-Garci´a Alejandro
Published: December 2008

Accurate charge-control and state-of-charge monitoring of lead-acid batteries is an ever-increasing necessity in an industry that demands low-maintenance costs and highly available systems. If the batteries are charged by photovoltaic panels and are installed in remote sites (e.g. Oil sea-platforms, highway emergency bays, autonomous communications systems) and exposed to aggressive environmental conditions (e.g. Extreme temperature, high humidity), the problem of extending the batteries’ useful life becomes a challenge. Most charging algorithms do not perform well when photovoltaic panels are the sole source of energy because energy availability is not guaranteed. A charge algorithm that maximizes the use of energy generated by the panel during daylight hours is needed. This paper presents a microcontroller-based charge-controller suitable for photovoltaic applications. The controller performs temperature compensation on the charge algorithm. It also stores those parameters that provide an indication on batteries’ state-of-charge and state-of-health: Panel voltage, battery’s voltage and current, current demanded by a load and room temperature. The controller has serial communication capabilities that make possible the connection to a personal computer or central station. By using a local industrial network or radio links, multiple controllers can be monitored by a central station running a battery management program. The information collected by all the controllers in the system is analyzed to determine the state-of-charge of individual batteries and, if required, command the appropriate controller to perform special procedures like, for example, thorough diagnostics or equalization. Preliminary field-test results of a controller installed in a high-way emergency bay are presented in this paper. It is shown that protection against deep discharges is achieved, which contributes to extend the battery useful life.
Displacement Natural Ventilation in an Enclosure With a Convective/Radiative Heat Source and Non-Adiabatic Envelope
Authors: Gao Jun , Zhao Jia-Ning , Gao Fu-Sheng
Published: December 2008

This paper studies the real case of natural ventilated space with a convective/radiative heat source and non-adiabatic envelope. The real envelope and heat source are introduced into the ‘Emptying Filling Box’ model and then contribute to achieve a new developed one, Thermal and air Flow Natural Ventilation model. TFNV model combines the thermal and fluid mechanical characteristics of displacement natural ventilation. Two vertical zones of different temperature are divided as that in EFB model. But temperature in the lower zone is higher than outdoor. With TFNV model, natural ventilation parameters can be reasonably predicted — interface height, ventilation airflow rate, occupied zone temperature, etc. By comparison of the results of the two models, it is shown that EFB model underestimates the interface height as well as air temperature in the lower zone and overestimates the temperature difference between the upper and lower zone of the space. It is also observed that EFB model may improperly predict the ventilation airflow rate and ventilation load.
Prediction of the Vertical Temperature Distribution in a Large Enclosure Under Combined Air Conditioning and Natural Ventilation
Authors: Gao Jun , Li Xiao-Dong , Zhao Jia-Ning , Gao Fu-Sheng
Published: December 2008

This paper describes a combined system of air conditioning and natural ventilation for large enclosures. A multi-zonal model to simulate the vertical temperature distribution is established. This model describes airflow and heat transfer on a ‘macro’ scale compared to CFD model, but it appears very efficient for engineering application. In this model, air density is considered to change with air temperature. Multiple air jets, buoyancy driven natural ventilation and coupled heat transfer are taken into consideration. It is governed by non-linear equations and is resolved by an iterative solution. A program is compiled to calculate the mass flow and temperature distributions. It shows that the combined system of air conditioning and natural ventilation cut considerably down heat gain in occupied zone. By comparison, the combined system can be expected to give lower temperature both in the enclosure and on interior surfaces. Some cases are calculated, and the results suggest that it depends on many factors such as the height of ventilating opening, the effective opening area, and outdoor air temperature to effectively make use of natural ventilation in the combined system. To sum up, this paper presents an energy efficient system for large spaces and also a theoretical model to design the system and predict the vertical temperature distribution.
Optical Evaluation of Composite-Based Reflector Facets for Parabolic Trough Concentrators
Authors: Wendelin Tim , Gee Randy
Published: December 2008

As a possible alternative to glass mirrors, the use of composite-based reflector facets has been investigated for use on parabolic trough concentrators. The approach evaluated here is a composite-based parabolic facet (steel and fiberglass) with a separately attached reflector. This paper describes the basic design of these structural facets and reports on the optical tests that have been used to determine the optical accuracy of the facets.
Performance Evaluation of an Advanced Roof Integrated Solar Hot Water Heating System and Roof-Mounted Solar Photovoltaic Power System in New Home Construction
Authors: Moss T. A. , Mahoney A. R. , Palomino G. E. , Houser R. M. , Newman M. , Peebles G.
Published: December 2008

The performance of a building integrated solar domestic water heating system and roof mounted PV system in a residential dwelling located in the Phoenix area was evaluated for a 12 month period. The solar domestic hot water heating system installed was a preproduction prototype RITH (Roof Integrated THermosiphon) system. The RITH is a thermosiphon system that fully integrates into the roof to achieve the same profile as a skylight when seen from the street. The PV system consisted of two SAE 300 DG/50 modules, each having a 300 watt dc rating, and a GC-1000 1 kW inverter to produce 0.5 kW AC power at STC (standard temperature conditions). Both systems were installed on a Calex Homes model home in the Phoenix area on a south facing part of the roof. Both systems were mounted directly to a 5/12 pitch roof and, therefore, tilted at a 22.6° angle. Since both units were mounted on an unoccupied model home the domestic hot water (DHW) load was modeled to simulate a typical family of four living in the Phoenix area. The solar domestic water heating system was sized to meet ∼70% of the annual hot water needs for a typical Phoenix family of four using 80 gallons of hot water per day. The PV system was connected directly to the grid without any battery storage and was intended to offset household electrical demand. Data are presented for both the actual and predicted performance of the solar domestic water heating and PV systems for the 12 month monitoring period.
Measured Performance of Building Integrated Photovoltaic Panels: Round 2
Authors: Dougherty Brian P. , Fanney A. Hunter , Davis Mark W.
Published: December 2008

Architects, building designers, and building owners presently lack sufficient resources for thoroughly evaluating the economic impact of building integrated photovoltaics (BIPV). The National Institute of Standards and Technology (NIST) is addressing this deficiency by evaluating computer models used to predict the electrical performance of BIPV components. To facilitate this evaluation, NIST is collecting long-term BIPV performance data that can be compared against predicted values. The long-term data, in addition, provides insight into the relative merits of different building integrated applications, helps to identify performance differences between cell technologies, and reveals seasonal variations. This paper adds to the slowly growing database of longterm performance data on BIPV components. Results from monitoring eight different building-integrated panels over a twelve-month period are summarized. The panels are installed vertically, face true-south, and are an integral part of the building’s shell. The eight panels comprise the second set of panels evaluated at the NIST test facility. Cell technologies evaluated as part of this second round of testing include single crystalline silicon, polycrystalline silicon, and two thin film materials: tandem-junction amorphous silicon (2-a-Si) and copper-indium-diselenide (CIS). Two 2-a-Si panels and two CIS panels were monitored. For each pair of BIPV panels, one was insulated on its backside while the backside of the second panel was open to the indoor conditioned space. The panel with the backside thermal insulation experienced higher midday operating temperatures. The higher operating temperatures caused a greater dip in maximum power voltage. The maximum power current increased slightly for the 2-a-Si panel but remained virtually unchanged for the CIS panel. Three of the remaining four test specimens were custom-made panels having the same polycrystalline solar cells but different glazings. Two different polymer materials, Tefzel and Kynar, were tested along with 6 mm-thick, low-iron float glass. The two panels having the much thinner polymer front covers consistently outperformed the panel having the glass front. When compared on an annual basis, the energy production of each polymer-front panel was 8.5% higher than the glass-front panel. Comparison of panels of the same cell technology and comparisons between panels of different cell technologies are made on daily, monthly, and annual bases. Efficiency based on coverage area, which excludes the panel’s inactive border, is used for most “between” panel comparisons. Annual coverage-area conversion efficiencies for the vertically-installed BIPV panels range from a low of 4.6% for the 2-a-Si panels to a high of 12.2% for the two polycrystalline panels having the polymer front covers. The insulated single crystalline panel only slightly outperformed the insulated CIS panel, 10.1% versus 9.7%.
Comparative Flux Measurement and Raytracing for the Characterization of the Focal Region of Solar Parabolic Trough Collectors
Authors: Lu¨pfert Eckhard , Neumann Andreas , Riffelmann Klaus-J. , Ulmer Steffen
Published: December 2008

The focal region of parabolic trough collectors is extended over the whole length of the concentrator. This complicates the measurement of the flux distribution on the absorber of such solar collectors. However, in order to optimize the solar field output it is essential to study the effects of absorber geometry and concentrator precision on the optical performance of parabolic trough collectors. The intercept factor of radiation with the absorber is a significant measure for this. In this paper we present and compare three methods, a ray-tracing simulation model and two measurement systems, to assess the flux distribution in the focal region, from which the intercept factor can be calculated. Using real reflector surface data from photogrammetry, the ray-tracing results show very detailed flux maps that are in agreement with measured flux distribution in the focal area. Thus, collector optimization with ray tracing tools becomes an attractive option.
Ultraviolet Solar Radiation Over the Caribbean Island of Puerto Rico
Authors: Altaii Karim , Rivera Ramiro L.
Published: December 2008

Ultraviolet solar radiation was measured and recorded on a 5-minute, hourly and daily basis at four sites on the Caribbean island of Puerto Rico (located from 18° to 18° 30’N latitude and from 65° 30’ to 67° 15’W longitude) over a 24 calendar month time frame. Data were measured by an Eppley Total Ultraviolet Radiometer (TUVR) mounted on a horizontal surface (0.285 ≤ λ ≤ 0.385 μm wavelengths). This data presents the first published data on ultraviolet radiation over Puerto Rico. The data sheds new light on the ultraviolet radiation characteristics of this tropical island. Characteristics such as the daily average, monthly average hourly, monthly average daily, and annual average daily ultraviolet radiation are presented. The ratio of the monthly average daily ultraviolet radiation to the monthly average daily global radiation varied between 0.0476 and 0.0498, with a mean value of 0.0487 ± 0.0009. A regression correlation between ultraviolet and global radiation on an hourly basis is also developed.
Reducing the Thermal Inertia in a Conventional Solar Still to Increase Productivity
Authors: Jaguaribe E. F. , Lobo P. C. , Andrade M. A. R. , Ferraz F. B.
Published: December 2008

In many arid and semi-arid zones, such as in the Brazilian Northeast, potable water is scarce and people and animals suffer water scarcity year after year. On the other hand, insolation is usually high in these areas, favoring the use of solar stills. However, these stills demand substantial investments, not affordable by most users. One way to reduce costs is to increase the evaporation rate to raise the yield of solar stills. One method of enhancing the evaporation rate is to increase water temperature instantaneously during periods of high insolation by the reduction of the water thermal inertia [8–10]. This work discusses the increase water evaporation rate in a conventional solar still, by reducing the thermal inertia, and the increase in productivity of a Conventional Solar Still, CSS, by wicking. Results from experiments in two different days show that wicking increased the productivity of a CSS, from 17.1 to 19.5%. Knowledge of the mechanism that improves the yield of a CSS, should encourage the use of solar stills to minimize the scarcity of potable water in semi-arid zones.
A Hybrid Method for Estimating Natural Lighting Potential in Buildings
Authors: Kissock Kelly
Published: December 2008

This paper describes data and algorithms to estimate typical average interior illuminance from daylighting using a hybrid of Hay, Davies, Klucher, Reindl (HDKR) method for calculating total solar radiation on a tilted surface and the Illuminating Engineering Society (IES) Lumen Method for estimating interior illuminance from daylighting. This hybrid algorithm, in conjunction with typical meteorological data, directly accounts for shading and typical local cloud cover effects on an hour-by-hour basis, which is difficult to do using the IES sky-cover or sky-ratio methods. Several experiments show reasonable agreement between measured and calculated results. Case study examples demonstrate of use of the method, when incorporated into software, to quickly analyze daylighting potential in industrial facilities, and the use of this information to develop specific recommendations for cost-effectively reducing lighting energy use in industrial facilities by improving the utilization of natural lighting.
Assessment of Thermal Energy Storage for Parabolic Trough Solar Power Plants
Authors: Kearney David , Price Henry
Published: December 2008

Parabolic trough power plant technology is one of the most demonstrated solar power options commercially available. While trough power plants are the least expensive solar option, cost of electricity still exceeds that needed to directly compete with conventional fossil-fired large-scale central power technologies. Several evaluations have been done that identify a series of mechanisms for significant cost reduction over the next decade. One of the opportunities for improving the economics of parabolic trough plants is the development of lower cost and more efficient thermal energy storage (TES) technologies. This paper focuses on several of the TES technologies currently under development, namely: the use of an indirect molten-salt storage system, the use of molten-salt as a heat transfer fluid in the solar field and thermal energy storage system, and the development of new types of storage fluids. The assessment compares the cost and performance of these candidate thermal energy storage technologies by evaluating their impact on the levelized cost of electricity from the plant. This analysis is updated based on work conducted on these technologies during the last year.
Experiment and Analytical Studies Jujube Drying by the Solar Assisted Convection Drying
Authors: Cui Minghu
Published: December 2008

An experimental setup, a mini-cabinet with reflector at its top, has been designed to study the drying process of jujube fruit by the convection and the solar radiation with hot air convection. The research experimentally investigated the drying characteristics and behavior of heat and mass transfer. Also, drying curves were analyzed. It demonstrated that solar energy could play an important role in promoting heat and mass transfers and saves energy consumed. The optimum conditions of appropriated temperature and humidity were obtained to save energy in solar energy convection drying process.
Developments in High Temperature Parabolic Trough Receiver Technology
Authors: Price Henry , Hale Mary Jane , Mahoney Rod , Gummo Carin , Fimbres Robert , Cipriani Robert
Published: December 2008

The parabolic trough linear receiver is one of the primary reasons for the high efficiency of the Luz parabolic trough collector design used at the Solar Energy Generating Systems (SEGS) plants. Experience from the SEGS plants has shown that the reliability and lifetime of the parabolic trough receiver tube is the most significant issue for existing and future parabolic trough plants. Although highly efficient, the original Luz receiver tubes experienced high failure rates (approximately 4% to 5% per year). Failures included vacuum loss, glass envelope breakage, and degradation of the selective coating. This paper reviews receiver failure rates, the primary failure causes at two of the SEGS plants, and discusses receiver technology developments during the last several years that focus on improving the reliability of parabolic trough receivers. Data are provided on the performance and reliability of a new commercially available trough receiver.
Optimization of Photovoltaic/Thermal Collectors
Authors: McCabe Joseph
Published: December 2008

Recent designs in the Solar Decathlon have incorporated solar electric modules with heat capture. Zero Energy Buildings (ZEB) solicitations through the National Renewable Energy Laboratory (NREL) have recently awarded photovoltaic / thermal (PV/T) projects incorporating air and fluid based heat transfer mediums. This paper introduces the PV/T collector with a quick history of four different research and development projects starting with the Massachusetts Institute of Technology (MIT) in 1978. Suggestions for engineering design and performance guidelines are provided. A demonstration of a zero glazed thin film amorphous silicon photovoltaic module with air as the fluid transfer medium, captured off the backside, is presented. The paper provides suggestions on applications and appropriate environments for various PV/T collector types.
Modeling and Experimental Evaluation of Passive Heat Sinks for Miniature High-Flux Photovoltaic Concentrators
Authors: Sun Jian , Israeli Tomer , Reddy T. Agami , Scoles Kevin , Gordon Jeffrey M. , Feuermann Daniel
Published: December 2008

An important consideration in the practical realization of high-concentration photovoltaic devices is the heat rejection at high power densities to the environment. Recently, optical designs for generating solar flux in excess of 1000 suns on advanced solar cells — while respecting flux homogeneity and system compactness — were suggested with the introduction of solar fiber-optic mini-dish concentrators, tailored specifically to high-flux photovoltaic devices [1]. At the core of the design is the miniaturization of the smallest building block in the system — the concentrator and the cell — permitting low-cost mass production and reliance on passive heat rejection of solar energy that is not converted to electricity. First, this paper proposes a relatively simple 1-D axi-symmetric model for predicting the thermal and electrical performance of such mini-dish high-flux concentrators. Experimental measurements were performed with a real-sun solar simulator, indoors under controllable conditions, a flux levels up to 5,000 suns. A CFD (Computational Fluid Dynamics) model was also developed for model-validation. Both the modeling approaches predict heat sink temperatures within experimental uncertainty of a couple of degrees. Next, the 1-D axi-symmetric model is used to evaluate the sensitivity of different solar cell model assumptions, environmental effects (such as outdoor temperature, and the wind speed), heat sink size and geometry, thermal contact resistance, etc. It was confirmed that the miniaturization of the solar cell module permits passive heat rejection, such that solar cell temperatures should not reach more than 80°C at peak insolation and stagnation conditions. Though the cell rated efficiency degrades by only 1–2% in absolute terms, higher cell temperatures may compromise the integrity of the cell circuitry and of the encapsulation. The 1-D axi-symmetric model also allows optimization of the heat sink geometric dimensions for a given volume. Hour-by-hour performance simulation results for such an optimized design configuration were performed for one month in summer and one month in winter for two locations namely Philadelphia, PA and Phoenix, AZ. The insight gained from this study is important for the proper design of the various components and materials to be used in PV mini-dishes. Equally important is that it allows similar types of analyses to be performed and well-informed design choices to be made for mini-dishes that have to operate under different climatic conditions with cells of different performance and concentration ratios.
Cogeneration Using Bagasse and Fuelwood in the Jamaican Sugar Cane Industry
Authors: Barrett David S. O.
Published: December 2008

The efficient application of biomass cogeneration, to produce heat and electrical energy for internal processing and non-process demands for 85% of the year, and the production of surplus electricity for exportation to the grid, is the natural trajectory for the Jamaican sugar cane industry. The case study, Frome Sugar Company Ltd., (59,430 tonnes sugar/yr.), has among other environmental benefits, potential avoided fuel costs of US $1.15 billion, sequestering 480,617 tons of carbon with a potential for US$2.4 million in revenue from joint partnering in a Clean Development Mechanism over a 15 year period. Through a US$22.26 million capital investment at 14% interest, and concomitant upgrade of process equipment, overall factory efficiencies can be greatly improved and these benefits obtained. The production of fuelwood from company plantations at US$8.90/ton can facilitate a unit cost of energy (UCE) of US$0.04/kWh, annual income of US$11.37 million and internal rate of return (IRR) of 11.3%. An equal generation capacity using fuel oil to meet surplus generation requirements would cost US$7.95 million in capital costs, UCE of US$0.04/kWh and IRR of 23%. However, legal, market and policy barriers must be removed as an incentive to activate sustainable national environmental, social and economic benefits.
The Emergence of Conversion Technologies in California as a Viable Alternative to Landfilling
Authors: Moulton-Patterson Linda
Published: December 2008

In the 1980’s, California faced landfill siting problems and a projected shortage of landfill capacity that could impact the health and safety in California. To address this issue, the California Integrated Waste Management Act was passed in 1990 and established a framework to limit reliance on landfills. This framework gives greater emphasis to recycling, waste prevention, source reduction, and composting. The Integrated Waste Management Act required each city and county to implement plans to divert 25% of solid waste by 1995 and 50% by 2000 from landfills. Although we have achieved a 47% diversion rate and have 170 composting facilities, we still have approximately 30 millions tons of material being landfilled. This may be an untapped resource for energy and alternative fuels production.
2003 Upgrades at the GVRD Waste-to-Energy Facility
Authors: Richter Ron
Published: December 2008

Montenay Inc. has operated the Greater Vancouver Regional District’s (GVRD) Waste-to-Energy Facility since it began commercial operation in 1988. The facility has a throughput of 720 tonnes (800 tons) per day in three lines. It utilizes Martin grate technology and dry lime injection with a reverse pulse jet fabric filter. The original facility design did not include a steam turbogenerator for energy recovery. The facility produced process steam at near saturation temperature to supply a recycle paper mill. The aging mill has reduced the fraction of steam used in recent years. This caused the GVRD and Montenay Inc. to cooperate in a major facility upgrade that began in 2001 and was completed in August of 2003. The complete project includes a turbogenerator, major boiler improvements and modernization of the boiler controls, while continuing to service the recycle paper mill.
How to Successfully Increase the Revenue of Waste-to-Energy for the Long Term
Authors: Caillard Fred , Screve Francois , Deltour Delphine
Published: December 2008

The objective of the paper is to outline a new business-oriented methodology based on the principle of diagnosing before improving and with the aim to produce long-term results that mutually benefit the owner and the operator of a Waste-to-Energy or biomass plant. The scope covers (1) the determination of correction curves and coefficients for various operating conditions to compare actual equipment performance with design one (with illustration for a steam turbine); (2) the mapping of the yearly plant operation schedule into different operating modes, for a better evaluation of dollar benefits of improvement solutions; (3) the use of a computerized plant simulator model that performs heat and mass balances and translates available monitoring data into dollar value. When benchmarking the illustrated plant case study with industry standards, we found out that reducing the Deaerator pressure by 40 psi (by 2.7 bar) would translate into an expected additional $850k of total benefits a year.
Experience With Weld Overlay and Solid Alloy Tubing Materials in Waste to Energy Plants
Authors: Paul Larry , Eckhardt Michael , Ossenberg-Engels Andreas , Clark Gregg , Hoberg Bern
Published: December 2008

Corrosive conditions in waste to energy boilers produce rapid wastage rates of traditional boiler tube materials. It is not unusual to see corrosion rates in the range of 1 to 3 mm/y (40–120 mpy) on carbon steel boiler tubes and occasionally corrosion occurs at even higher rates. In the mid1980’s there were several boilers that experienced corrosion failures of carbon steel waterwall tubes in less than 6 months of service (1,2). Because of this experience, it has become accepted that some type of corrosion protection is required for boiler tubes in refuse-to-energy boilers. Over the years, many different alloys have been evaluated to improve tube life in waste-to-energy boilers. The most successful materials used for corrosion protection are nickel alloys.