J. Renewable Sustainable Energy - Journal of Renewable and Sustainable Energy

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Optimal sizing of reliable hybrid renewable energy system considered various load types

S. M. Hakimi, S. M. Moghaddas-Tafreshi, and H. HassanzadehFard

J. Renewable Sustainable Energy 3, 062701 (2011); http://dx.doi.org/10.1063/1.3655372 (18 pages) | Cited 1 time

Online Publication Date: 7 November 2011

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In this paper, a novel intelligent method is applied to the problem of sizing in a hybrid power system such that the demand of residential area is met. This study is performed for Kahnouj area in south-east Iran. It is to mention that there are many similar regions around the world with this typical situation that can be expanded. The system consist of fuel cells, some wind units, some electrolyzers, a reformer, an anaerobic reactor, and some hydrogen tanks. The system is assumed to be stand-alone and uses the biomass as an available energy resource. System costs involve investments, replacement, and operation and maintenance as well as loss of load costs. Prices are all empirical and components are commercially available. In this study, we consider load growth and different types of load profile for their system. In this village, four types of loads exist such as residential, agricultural, industrial, and official loads. Also we consider load growth for the loads. Particle swarm optimization algorithm is used for optimal sizing of system’s components.

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88.50.G-	Wind turbines
02.60.Pn	Numerical optimization
88.30.G-	Fuel cell systems

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Assessment of the effectiveness of policy implementation for sustainable energy development in Southeast Europe

Mirjana Golušin, Olja Munitlak Ivanović, Siniša Domazet, Siniša Dodić, and Damjan Vučurović

J. Renewable Sustainable Energy 3, 062702 (2011); http://dx.doi.org/10.1063/1.3663953 (12 pages)

Online Publication Date: 7 December 2011

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Using solely economic indicators as a measure of development as a whole is no longer justified and acceptable. The survey covered 11 countries in the region of Southeast Europe—in the region for which indicators of sustainable energetic development were defined. The authors propose a specific way of expressing their needs for treatment using the method of weight coefficients. The results indicate that the efficiency of energetic policy in the region varies widely. Countries at higher level of economic development record a high dependence on energy imports. Countries in the region at a similar stage of development show different energy consumption per capita and the different intensity of energy production from renewable resources. Research shows that energetic efficiency policies in the region, apart from the available energy resources, largely depends on the degree of economic development that a country wants to achieve. Countries at lower level of development show higher degree of sustainability in terms of energy management and vice versa. The most favorable situation was observed in Bulgaria. Negative trends were observed in Greece and Hungary, while in Slovenia the indicators were on the border of sustainability. Data used for research refer to the year 2010.

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88.05.Lg	Economic issues; sustainability; cost trends
88.05.Jk	Policy issues; resource assessment

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Solid dye-sensitized solar cells prepared through a counter strategy for filling of solid hole transporter

Zhenzhen Yang, Katherine C. Powers, Di-Jia Liu, Yang Ren, and Tao Xu

J. Renewable Sustainable Energy 3, 063101 (2011); http://dx.doi.org/10.1063/1.3658435 (9 pages)

Online Publication Date: 3 November 2011

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Efficient solid-state dye sensitized solar cells (DSSCs) require a tight filling of solid p-type semiconductors into the dye-sensitized nanoporous n-type semiconductor in order to form a good interfacial electrical contact. We report here a facile and unique counter-methodology that achieves compact contact between the sensitized TiO₂ network and the solid p-type semiconductor for the assembling of solid DSSCs. The separated n-type TiO₂ nanoparticles (NPs) are firstly dye sensitized before formation of the film, which is opposite to the conventional procedure of sintering the TiO₂ NPs into a nanoparticulate film prior to dye sensitization. Next, a solution of p-type CuSCN is mixed with the sensitized TiO₂ NPs, followed by the evaporation of the solvent to obtain the solid nanocomposition of sensitized TiO₂ NPs wrapped with p-type CuSCN. The solid DSSCs are assembled by a series of film compressing and film transferring processes. The structures of the cells are characterized and the photovoltaic behaviors of the cells are also investigated and compared with cells prepared by conventional methods.

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88.40.jp

Multijunction solar cells

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Potential for ethanol production from conservation reserve program lands in Oregon

Ankita Juneja, Deepak Kumar, John D. Williams, Donald J. Wysocki, and Ganti S. Murthy

J. Renewable Sustainable Energy 3, 063102 (2011); http://dx.doi.org/10.1063/1.3658399 (8 pages)

Online Publication Date: 8 November 2011

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Increase in energy demand has led towards considering lignocellulosic feedstocks as potential for ethanol production. Aim of this study was to estimate the potential of grass straws from conservation reserve program (CRP) lands as feedstocks for ethanol production. The CRP was initiated to ensure reduction in soil erosion with a concomitant improvement in water quality and aquatic habitats. Species and abundance of various grasses in CRP sites can vary substantially. Ethanol yield from biomass is directly correlated to sugar content among other factors. It therefore becomes important to study the variability in the biomass composition from different CRP sites to reliably estimate biofuel production potential. Grass samples were collected from five fields contracted to CRP in Umatilla County in Northeastern Oregon. Composition of these samples was experimentally determined and was statistically verified to be similar for most of the sites. Sugar content was highest (60.70%) and statistically different for only one site (CRA 8.2). Our results suggest that biomass harvested from different sites did not significantly vary in terms of their chemical composition and therefore could be used in a single integrated process to produce bioethanol. Total potential ethanol yield from various CRP lands in Oregon, assuming a 10 yr harvesting frequency, was estimated to be 40 × 10⁶ l of ethanol (28.5–53.7 × 10⁶ l/yr) with current management practices subject to other constraints.

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87.85.M-	Biotechnology
88.20.F-	Renewable alternative fuels from biomass energy
89.60.-k	Environmental studies

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A floating platform of concrete for offshore wind turbine

Jianbo Hua

J. Renewable Sustainable Energy 3, 063103 (2011); http://dx.doi.org/10.1063/1.3658434 (13 pages)

Online Publication Date: 8 November 2011

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A floating platform concept is introduced in this paper for offshore wind turbine. A vertical cylinder on the top of an elliptical sphere forms the principal configuration of the platform. The analysis of the dynamic performance of an example platform with 5 MW wind turbine by means of the well-established linear theory for the dynamics of marine constructions in waves shows that the platform is able to secure the normal function of the wind turbine in waves up to rough sea state and has the required dynamic performance for survival in extreme waves by adopting a survival ballast condition. An important feature of this concept is that reinforced concrete can be used as cost-efficient construction material so that the service life, several times longer than similar steel constructions can be obtained despite of the marine corrosive and erosive environment. Thus, this kind of platform can become competitive in the economical, sustainable, and environment-friendly aspect.

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88.50.jp	Off-shore wind farms
88.50.G-	Wind turbines

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H₂ generation from two-step thermochemical water-splitting reaction using sol-gel derived Sn_xFe_yO_z

Rahul Bhosale, Rajesh Khadka, Jan Puszynski, and Rajesh Shende

J. Renewable Sustainable Energy 3, 063104 (2011); http://dx.doi.org/10.1063/1.3659684 (12 pages)

Online Publication Date: 15 November 2011

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H₂ has a great potential to replace fossil fuels and contribute to clean energy by reducing the environmental carbon foot-print. This study reports H₂ generation from a thermochemical water-splitting reaction using sol-gel derived Sn_xFe_yO_z powders. The sol-gel synthesis involved the addition of SnCl₂ · 2H₂O and FeCl₂ · 4H₂O in ethanol followed by gelation using propylene oxide. As-synthesized gels were aged, dried, and heated rapidly upto different temperatures and quenched in air or N₂ environment. The calcined powders were characterized using powder x-ray diffraction, BET surface area analyzer, and scanning electron microscopy (SEM). Calcination temperature and environment were found to have a significant effect on phase composition and specific surface area (SSA). The calcined Sn_xFe_yO_z powders were placed in a tubular Inconel reactor and four consecutive thermochemical cycles were performed. Water-splitting and regeneration steps were carried out at 900 °C and 1100 °C, respectively. The powder calcined in N₂ environment showed a mixed phase composition containing Sn_0.4Fe_2.6O₄ and SnO₂ and it generated an average of 1.88 ml of H₂ g⁻¹ cycle⁻¹.

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84.60.-h	Direct energy conversion and storage
68.49.Uv	X-ray standing waves
81.10.Dn	Growth from solutions
81.10.Fq	Growth from melts; zone melting and refining
81.15.Lm	Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

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Numerical investigation and evaluation of optimum hydrodynamic performance of a horizontal axis hydrokinetic turbine

Suchi Subhra Mukherji, Nitin Kolekar, Arindam Banerjee, and Rajiv Mishra

J. Renewable Sustainable Energy 3, 063105 (2011); http://dx.doi.org/10.1063/1.3662100 (18 pages)

Online Publication Date: 21 November 2011

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The hydrodynamic performance of horizontal axis hydrokinetic turbines (HAHkTs) under different turbine geometries and flow conditions is discussed. Hydrokinetic turbines are a class of zero-head hydropower systems which utilize kinetic energy of flowing water to drive a generator. However, such turbines very often suffer from low-efficiency which is primarily due to its operation in a low tip-speed ratio (≤4) regime. This makes the design of a HAHkT a challenging task. A detailed computational fluid dynamics study was performed using the k-ω shear stress transport turbulence model to examine the effect of various parameters like tip-speed ratio, solidity, angle of attack, and number of blades on the performance HAHkTs having power capacities of ∼12 kW. For this purpose, a three-dimensional numerical model was developed and validated with experimental data. The numerical studies estimate optimum turbine solidity and blade numbers that produce maximum power coefficient at a given tip speed ratio. Simulations were also performed to observe the axial velocity ratios at the turbine rotor downstream for different tip speed ratios which provide quantitative details of energy loss suffered by each turbine at an ambient flow condition. The velocity distribution provides confirmation of the stall-delay phenomenon due to the effect of rotation of the turbine and a further verification of optimum tip speed ratio corresponding to maximum power coefficient obtained from the solidity analysis.

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47.85.Kn	Hydraulic and pneumatic machinery
47.85.Np	Fluidics
88.60.K-	Hydroturbines
02.60.-x	Numerical approximation and analysis
47.11.-j	Computational methods in fluid dynamics
47.27.-i	Turbulent flows
47.32.Ef	Rotating and swirling flows

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Electrical energy from foods

S. Abdalla and A. A. Al-Ghamdi

J. Renewable Sustainable Energy 3, 063106 (2011); http://dx.doi.org/10.1063/1.3659289 (16 pages)

Online Publication Date: 28 November 2011

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Presenting new sources of safe energy sources is not only an urgent need but also a vital input for social and economic development. In this work, we present a novel technology to produce electric energy from food; in particular from commercial potatoes. The food has been sandwiched between two metals; for example, Zn/potatoes/Cu and the open circuit electric potentials V_oc have been measured. It has been found that V_oc lay in the range V_oc 0.32 V < V_oc < 1.39 V and decays exponentially by time. The open circuit potential varies from food to another and depends also on the metallic contacts and food thickness. It has been found that V_oc is a function of the potatoes thickness, which has a maximum at 1.05 V and the corresponding maximum short circuit current is about 1.7 mA. The internal resistivity for the potatoes battery is about 1.4 × 10⁴ Ω cm and the metallic electrodes resistance is about 57.4 Ω × area for Zn/Cu electrodes. The short circuit current depends on the nature of the metallic electrodes and the food itself. This current is very sensitive to the food thickness. At a critical thickness when the potato slice is about 0.18 cm, the maximum short circuit current density of the potatoes battery is about 15.7 μA/cm². The maximum electric power, generated at 0.18 cm, equals155 μW/cm². The Zn/potatoes/Cu battery has electric capacity 2.57 times more efficient than an AA/LR6 1.5 V alkaline Energizer^® battery. Also, cost analysis has showed that potatoes-cells generate electric energy 26 fold cheaper than commercially available Energizer^® battery. This work presents a new energy source: Safe, economic, durable, and renewable; also it can fit most applications.

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88.80.ff	Batteries
82.45.Fk	Electrodes
82.47.-a	Applied electrochemistry
84.37.+q	Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

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Hafnium and tantalum carbides for high temperature solar receivers

Elisa Sani, Luca Mercatelli, Daniela Fontani, Jean-Louis Sans, and Diletta Sciti

J. Renewable Sustainable Energy 3, 063107 (2011); http://dx.doi.org/10.1063/1.3662099 (6 pages)

Online Publication Date: 28 November 2011

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Solar thermal technology is a safe, sustainable, and cost-effective energy supply. The present paper reports on the comparative high-temperature emissivity characterization of hafnium and tantalum carbide ultra-high temperature ceramics to evaluate their potential as novel absorbing materials for concentrating solar power plants. For a more meaningful property assessment, ultra-high temperature ceramic samples have been compared also with silicon carbide, a material already used in volumetric solar receivers.

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88.40.F-	Solar concentrators
42.79.Ek	Solar collectors and concentrators

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Efficiency of a parabolic trough collector as a water heater system in Yucatán, Mexico

N. Rosado Hau and M. A. Escalante Soberanis

J. Renewable Sustainable Energy 3, 063108 (2011); http://dx.doi.org/10.1063/1.3663954 (6 pages)

Online Publication Date: 8 December 2011

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The performance of a parabolic trough collector (PTC) manufactured in Merida, Yucatán, was evaluated under the ANSI/ASHRAE 93-1986 standard. The water heating system for testing with a constant flow limited to a maximum temperature of 55 °C was built; thus the tests were at low temperatures. Using water as working fluid, it was found that the maximum efficiency of the collector was 5.43%, with a flow rate of 0.022 kg/s at a direct solar irradiance with incidence angle 0°. The evaluation methodology and design of the system for testing the collector is reported in this paper.

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42.79.Ek	Solar collectors and concentrators
88.40.-j	Solar energy

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Short-term electricity dispatch optimization of Ertan hydropower plant based on data by field tests

Chao Ma, Haijun Wang, and Jijian Lian

J. Renewable Sustainable Energy 3, 063109 (2011); http://dx.doi.org/10.1063/1.3668287 (15 pages)

Online Publication Date: 15 December 2011

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A short-term electricity dispatch optimization program required by the Ertan hydropower plant is developed to maximize hydropower production. Three field tests in various operating heads were carried out in the period of May 2009 to March 2010. Based on data of five test conditions, three operating zones for units in various operating heads were proposed. A short-term electricity dispatch optimization model was developed with physical and operational constraints. Unit commitment strategy was put forward for model solution, in which unit statuses and output statuses were classified. The strategy aimed at formulating better unit commitment plan according to forecasted load demand, ancillary service requirements, and initial operating status. The model and the strategy were verified by real cases. The results show that the optimal load distribution among units at every interval can be easily solved by the genetic algorithm based on a fixed unit commitment plan. Schedules are developed with higher average generation efficiency. Units can also be scheduled to operate for a less time within the rough zone and the second feasible zone. The proposed method is already operational for dispatch engineers of the Ertan hydropower plant to determine half-hourly schedules in one day.

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88.60.-m	Hydroelectric power
88.05.Gh	Energy conservation; electricity demand reduction
02.60.Pn	Numerical optimization
84.70.+p	High-current and high-voltage technology: power systems; power transmission lines and cables

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Mechanical and thermal properties of methane clathrate hydrates as an alternative energy resource

Hu Huo, Yuan Liu, Zhaoyang Zheng, Jijun Zhao, Changqing Jin, and Tianquan Lv

J. Renewable Sustainable Energy 3, 063110 (2011); http://dx.doi.org/10.1063/1.3670410 (8 pages)

Online Publication Date: 16 December 2011

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Mechanical, acoustic and thermal properties for three common hydrates structures sI, sII, and sH were investigated using first-principles methods. Elastic constants were estimated by fitting strain energy versus Lagrangian strain. Bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio deduced from elastic constants are in reasonable agreement to experimental values. The longitude and transverse velocity compare reasonably with the experimental results with systematical overestimation. Using the quasi-harmonic approximation and Debye model, some thermal properties including heat capacity, linear thermal expansion, Grüneisen parameter, and Debye temperature for structure sI and sII were estimated and compared with available experiments.

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88.20.fn	Hydrogen
81.40.Jj	Elasticity and anelasticity, stress-strain relations
62.20.de	Elastic moduli
62.20.dj	Poisson's ratio
02.30.Mv	Approximations and expansions
61.66.Hq	Organic compounds

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Effects of aging on the mobility and lifetime of carriers in organic bulk heterojunction solar cells

Vinamrita Singh, Swati Arora, P. K. Bhatnagar, Manoj Arora, and R. P. Tandon

J. Renewable Sustainable Energy 3, 063111 (2011); http://dx.doi.org/10.1063/1.3670411 (8 pages)

Online Publication Date: 16 December 2011

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Mobility and lifetime of the carriers are two very crucial parameters, which can account for the aging of a photovoltaic device, because changes in morphology, electrode/polymer interfaces, etc., will finally result in decrease of mobility and lifetime of carriers. In the present work, we have tried to explain our experimental data with the help of theoretical analysis based on our earlier model in which we have incorporated the activity at electrode interfaces in terms of density of surface states, thickness of interface layer, and tunneling probability. Calculations show that decrease in mobility for a cell under illumination is much faster than in a dark cell. Photoinduced oxidation plays a dominant role in fast degradation of the mobility. The lifetime is also seen to decrease because of modification of parameters such as interface thickness, density of interface states, and roughness.

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88.40.H-	Solar cells (photovoltaics)
02.50.Cw	Probability theory

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Evaluating daylighting potential and energy efficiency in a classroom building

E. L. Krüger and S. D. Fonseca

J. Renewable Sustainable Energy 3, 063112 (2011); http://dx.doi.org/10.1063/1.3670407 (19 pages)

Online Publication Date: 16 December 2011

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In this paper, we analyze the possibility of using daylight as the main source of light for learning and teaching activities in a classroom building of the Universidade Tecnológica Federal do Paraná, in Curitiba, Brazil. Beginning with a survey on light bulb and luminaire types used in the building and on the potential of daylighting in such environments, six different classroom types with different solar orientations were selected for analysis. The research methods included the estimation of daylighting potential from obtained daylight coefficients (DCs) for periods of the year and sky conditions, other than those of the onsite measurements; the evaluation of conformity of the lighting system to the Brazilian RTQ Code (Regulamento Técnico de Qualidade), an energy consumption rating system, aimed at reducing electric energy consumption in office buildings; the estimation of electric energy demand for a combined use of daylighting and lighting system; the proposal of an efficient lighting system; and cost assessment using payback analysis. Results suggest energy savings of up to 94% when integrating daylight with the artificial lighting system, a payback within the range of 22–60 months for a complete substitution of the existing lighting system for a more efficient one.

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88.40.mx

Day lighting/natural lighting of buildings

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Climate zones and the influence on industrial nonprocess energy consumption

Khaled Bawaneh, Michael Overcash, and Janet Twomey

J. Renewable Sustainable Energy 3, 063113 (2011); http://dx.doi.org/10.1063/1.3670513 (8 pages)

Online Publication Date: 20 December 2011

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This paper begins with the recognition that climate zones influence nonprocess energy use in industrial buildings. Nonprocess energies are heating, cooling, lighting, and ventilation. Nonprocess energy data have been collected from the literature (about 68 buildings) across a wide range of climate zones. The hypothesis tested in this research is: if an industrial building has a characteristic nonprocess energy related to physical dimensions and desired comfort level, then using cooling degrees day (CDD) and heating degrees day (HDD) factors can normalize the measured nonprocess temperature control data for the climate zone differences. That is, do measured nonprocess energy intensities (W/m²), if corrected for climate zone differences, within each building category become more similar and hence reflecting the basic building temperature control energy use? The five U.S. climate zones and the location for each facility in this study were identified. To investigate how the location influences the amount of heating and cooling at each facility, a baseline analysis of five representative cities in each zone was done to obtain the 5-year average CDD and HDD. The reported values of heating and cooling for each facility were then adjusted using this baseline and the climate zones of that facility, so that each facility was then referenced to zone 3; that is, as if all manufacturing facilities were in the same zone 3. The mean, median, standard deviation, and total nonprocess energies for current and zone-adjusted nonprocess energy for each facility in this study were calculated. The mean values of current and adjusted heating and cooling remained close to each other and the standard deviation was not reduced by these adjustments. Thus, the hypothesis of using CDD/HDD to quantitatively account for and hence to adjust for different climate zones appears to not be valid. The absence of improvement (reducing the standard deviation) by normalizing heating and cooling energy using adjustment for climate factors using the concept of CDD/HDD implies that some other correction principles are needed for evaluating fundamental needs for industrial building heating and cooling. The inability to reduce the geographic (that is, climate zone) effects of industrial plant nonprocess energy intensities supports the de-emphasis of this tool in the ASHRAE Handbook.

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88.10.cn	Heating and cooling of buildings; space heating
88.40.M-	Residential and commercial buildings
88.05.Sv	Energy use in heating and cooling of residential and commercial buildings

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Approach to designing a solar concentrator for small-scale remote power application

Khaled Metwally, Ahmed Makhlouf, and Lamyaa El-Gabry

J. Renewable Sustainable Energy 3, 063114 (2011); http://dx.doi.org/10.1063/1.3671649 (11 pages)

Online Publication Date: 23 December 2011

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A small-scale concentrated solar power (CSP) unit was designed to provide electricity and hot water using an organic Rankine cycle (ORC) for Egypt as part of an undergraduate capstone project. The system was designed for a target power output of 3 kW. It uses parabolic troughs to heat ethylene glycol used as the heat transfer fluid, which absorbs heat in the trough collector and transfers it to the working fluid through a heat exchanger. The system consists of 9 parabolic troughs and a total aperture area of 67 m², providing the required 3 kW of energy to the ORC. One parabolic trough was manufactured to test its thermal efficiency according to ASHRAE standard 93-2003 [Methods of Testing to Determine the Thermal Performance of Solar Collectors (ASHRAE, Inc., 1791 Tullie Circle, NE, Atlanta, GA 30329, 2003)] and compared it to its calculated value. A simple microcontroller-based system was used to track the sun.

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