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991.
992.
Joe‐Air Jiang Jen‐Cheng Wang Kun‐Chang Kuo Yu‐Li Su Jyh‐Cherng Shieh 《国际能源研究杂志》2014,38(10):1304-1317
The incident angle is a critical factor impacting the performance of fixed photovoltaic (PV) modules. Off‐normal incidence leads to significant changes in the current–voltage (I–V) characteristics and serious deterioration in the performance of fixed PV modules, resulting in difficulties in achieving optimal use of the available solar energy and retaining the maximum power output. To investigate this problem in depth, we develop a theoretical method based on the material properties and recombination mechanisms of the semiconductor, which can be used to directly evaluate the incident angle dependence of the energy harvesting performance and the maximum power point (MPP) estimation of PV modules composed of different materials from their I–V characteristic curves under irradiation. The proposed method is a simple approach with a low calculation burden. The performance of the proposed method is evaluated by examining the characteristics of the open‐circuit voltage, short‐circuit current, MPP, and the maximum output power of PV modules constructed of different semiconductor materials with respect to the various incident angles. The results are discussed in detail. The experimental results demonstrate that the proposed method could be used to optimize the performance of fixed PV modules and realize MPP control of PV systems during practical operation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
993.
A closed wet cooling tower, adapted for use with chilled ceilings in buildings, was tested experimentally. The thermal efficiency of the cooling tower was measured for different air flow rates, water flow rates, spray flow rates and wet bulb air temperatures. CFD was also used to predict the thermal performance of the cooling tower. Good agreement was obtained between CFD prediction and experimental measurement. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
994.
This paper describes existing numerical techniques used for simulating heat pipe operation, and the development of a simplified numerical model for normal wicked/wickless heat pipes based on the analysis of current modelling methods. Vapour flow was treated as a two‐dimensional flow. Heat transfers through the liquid–wick region and wall region were computed by solving a one‐dimensional heat conduction equation. Flow in the liquid–wick region was treated as a one‐dimensional problem. The liquid and vapour flows were coupled using a set of governing equations, incorporating thermal compressibility, hydro‐dynamical and capillary relationship, as well as geometrical correlation. The finite‐difference method was employed to carry out the numerical analysis, and FORTRAN language was used to develop a computer program. The model was used to investigate the operating characteristics of a long ‘wicked’ heat pipe, including variation of cross‐sectional area, axial/radial velocity, pressure and temperature of liquid/vapour flows with height position above the liquid level. To validate the modelling predictions, a test rig was constructed to carry out experimental testing. This included measurement of surface temperatures and heat flow associated with heat‐pipe heat transfer. The results from tests were found to be in general agreement with the numerical predictions when the test conditions were close to the simulation assumptions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
995.
The paper presents a stochastic and economic analysis for petroleum development under uncertain market and technical environments. Mean-reversion with jumps for price forecasting is used to consider market uncertainty, while various scenarios for the reservoir properties and cost are employed to consider technical uncertainty. Monte Carlo simulation is carried out to obtain the feasible range of net present values and internal rates of return. The influence of stochastic parameters is examined through correlation coefficients. The stochastic approach yields more reliable evaluation and effectively investigates the characteristics of development. The integration of uncertainties and contractual terms results in an irregular tendency in the future cash flow and reveals that a larger reserve does not guarantee a greater profit. The reserve and the well rate affect the economic values whereas the parameters for price prediction don＇t. The research confirms the necessity of qualifying uncertainties for realistic decision-making at the initial stage of development. 相似文献
996.
Gottberg A Morris J Pollard S Mark-Herbert C Cook M 《The Science of the total environment》2006,359(1-3):38-56
The EU Directive on Waste Electrical and Electrical Equipment (WEEE) (2002/96/EC), to be implemented in stages from August 2004, attempts to tackle the growing quantity WEEE by making producers responsible for the costs of the collection and recycling of their products at the end of usable life. This is considered to give producers a financial incentive to reduce waste at source through eco-design. This link is, however, under-researched and little is known generally about the effectiveness of extended producer responsibility (EPR) and policies to promote it. This paper presents the findings of an exploratory study to address these important gaps in knowledge. Literature review was used to develop an analytical framework to explain the relationships between the drivers for eco-design and the role of policies to promote EPR. This was applied to eight case studies of firms from the European lighting sector. While quantitative data to confirm the link between EPR and eco-design were difficult to obtain, the case studies showed that EPR has had little effect on product development so far. Within the sector studied, most producers have been able to pass on incremental costs associated with EPR to customers with negligible effects on sales. This reflects perceptions in the lighting sector that, because demand for products is relatively price inelastic and the regulation affects all producers equally, EPR is unlikely to drive eco-design at least in the short run. The cases also showed that choice between individual and centrally provided waste recovery schemes rested on perceptions of relative costs and practicability. It was evident that other drivers, such as bans on hazardous substances, product declarations and supply chain pressures, were often more effective promoters of eco-design. Thus it seems a mix of policy measures is required rather than reliance on economic instruments alone. 相似文献
997.
An econometric model of the U.S. economy with random coefficients is solved as a stochastic control problem by augmenting the state vector with random coefficients, linearizing the resulting problem, and obtaining a feedback rule for the augmented problem. The performance of this augment closed loop rule is then compared to regular closed rule with Monte Carlo methods on one-random parameter and three-random parameter examples. 相似文献
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