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Abstract The hybrid pneumatic power system (HPPS) proposed in this research replaces the battery’s electric-chemical energy with flow work and optimizes the management and utilization of the energy. This power system is able to keep the internal-combustion engine working at its optimal condition and turn its waste energy into effective mechanical energy and so enhance the thermal efficiency of the whole system. Using computer simulation software ITI-SIM, this study simulates the overall dynamic characteristics of the system in accordance with the regulated running-vehicle test-mode ECE47, and, with experimental verification and analysis, proves that this system can meet the requirements of the standard running-car mode. As for recycling the waste energy, the experimental results show that this design could offset the shortcomings of the low-density of pneumatic power and so effectively enhance the efficiency of the whole system.

Abstract Regarding energy storage in concentrated solar power plants, thermocline technology is considered to be a cost effective but less efficient solution than conventional two-tank. However, thermocline storage charge and discharge are usually stopped when the varying outlet temperature reaches an arbitrarily chosen value. It is shown here that the stop of the thermocline charge depends on the overheating risk in the solar collectors, while the stop of the discharge is defined by the steam generator requirements. As a consequence, the temperature thresholds that must be defined by the experimental constraints are dynamic. Using these dynamic thresholds on an experimental setup comprising a 230 kWh thermocline tank and a 150 kWth parabolic trough solar field led to a charge efficiency of 95.7% and a 93.5% discharge efficiency. Thus, the varying outlet temperature of a thermocline storage system is not an issue when integrated in a concentrated solar power plant.

In this paper, per capita CO2 convergence among the EU-25 countries between 1920 and 2007 is analysed using the distribution dynamics approach. Furthermore, the analysis is complemented by investigating the asymptotic half-life of convergence, mobility indices and the continuous version of the ergodic distributions. The novel aspect of this work consists in the fact that it examines whether patterns could differ if weighted by either the population of each country or their economic sizes. The unweighted analysis indicates that the convergence patterns differ strongly before and after World War II, with more convergence being displayed after the seventies. Results of weighting both by population and by economic size show that convergence is much faster when these features are introduced into the model. Conclusions from this analysis are important for the environment policy adopted across the EU-25 countries.

Abstract This paper examines manufacturing energy use due in 10 IEA countries between 1973 and 1998. Changes in energy use are described through using Laspeyres indexes to enable the decomposition of energy use into changes in the overall output of manufacturing (i.e. value added), the structure of output (industrial mix), and the energy intensity of each sub-sector, and to consistently compare the results across countries. The results show that structural changes have reduced manufacturing energy-use in most countries, particularly the US and Japan. In a few countries, however, the manufacturing structure became more energy-intensive and thus drove up energy use over the study period. For the group of 10 IEA nations, the net effect of structural changes accounted for more than a third of the reduction in total manufacturing energy use per unit of output between 1973 and 1998. The rest of the reductions in this period can be explained by falling energy-intensities in individual manufacturing branches. Contrasting post-1986 with earlier years shows that the rate of energy-intensity decline in manufacturing has slowed in most countries. Between 1994 and 1998 most countries experienced a strong growth in manufacturing output and a reduction in aggregated manufacturing energy use per unit output. However, the results of the decomposition analysis presented in this paper point to this reduction being mostly due to a structural shift towards less energy-intensive branches, such as electronics and electronic equipment, and that the impact from reduced energy-intensities was close to nil for the group of 10 IEA countries studied here.

Abstract A dynamic numerical thermal model has been developed for rooftop building integrated photovoltaic systems, considering a fully or partially integrated configuration, their integration structure and an insulated air gap at the underside. The two-dimensional mathematical model was validated using a test bench representing a residential partially integrated photovoltaic system. The accuracy of the model was studied by deriving the equivalent thermal resistance (or Ross coefficient). Values obtained with the developed model were compared to a nominal operating cell temperature thermal model based on manufacturer datasheet, and the measured data. The results were indicative of a well ventilated air gap and an appropriate choice of Nusselt number. The model was additionally tested for a fully integrated photovoltaic system to demonstrate its utility for different integration architectures. The mean absolute error of the model was evaluated to 2.71 °C for module temperature. It could, therefore, be useful for design studies requiring the prediction of thermal behaviour, as may become important for future regulations and business models such as self-consumption. Future work will consider facade photovoltaic systems, shading elements and coupling to an electrical model. Preliminary results indicate an accuracy of 4.7% in electrical energy production using a simplified electrical model.

Abstract A high-energy-efficient process for empty fruit bunch drying with integration to gasification and combined cycle processes is proposed. The enhancement is due to greater exergy recovery and more efficient process integration. Basically, the energy/heat involved in a single process is recovered as much as possible, leading to minimization of exergy destruction. In addition, the unrecoverable energy/heat is utilized for other processes through process integration. During drying, a fluidized bed dryer with superheated steam is used as the main evaporator. Exergy recovery is performed through exergy elevation via compression and effective heat coupling in a dryer and heat exchangers. The dried empty fruit bunches are gasified in a fluidized bed gasifier using air as the fluidizing gas. Furthermore, the produced syngas is utilized as fuel in the combined cycle module. From process analysis, the proposed integrated processes can achieve a relatively high energy efficiency. Compared to a standalone drying process employing exergy recovery, the proposed integrated drying can reduce consumed energy by about 1/3. In addition, the overall integrated processes can reach a total power generation efficiency of about 44%.

The compressor is an important auxiliary for fuel-cell (FC) operation. Growing fuel-cell system efficiency involves an optimal fuel cell energy management and the air management is a key issue. Thus, a good modelling for static and dynamic operation of all components of the FC system, and in particular of the compressor, is required. The difficulties, due to a lack of information about the performance of compressors, demand predictive and modern approximation methods to be used for compressor modelling. To overcome these issues, the paper proposes and presents a moving least squares (MLS) algorithm for obtaining a surrogate model of the centrifugal compressor. The experimental data provided by manufacturers are used for this task. The results can be used for the development of an off-design model or the overall dynamic simulation of the behaviour of a FC system.

Abstract Numerous shortcomings such as higher manufacturing cost, inadequate refueling facilities, and durability issues are impeding the competitiveness of fuel cell hybrid vehicles (FCHVs). Effectively coordinating the design and operational aspects with a fair trade-off among ownership price, energy consumption, and health degradation is the key to address these shortcomings. Against this background, the paper devises a novel dual-layer approach to synergize the sizing aspect with the online energy management system (OEMS) of FCHV. Within the proposed approach, the first layer utilizes the specific driving parameters to offer a global configuration of the FCHV propulsion system. Despite guaranteeing consistent vehicular performance under diverse driving conditions, the global configuration generally favors oversized sources. To address this problem, flexible design coefficients are introduced to allocate a practical sizing range to the sources of FCHV. From this range, a feasible combination is selected in the second layer by coordinating the sizing procedure with the OEMS. An effective coupling method is exploited to design the OEMS, where two distinct supervisors with instantaneously adjustable rules are formulated. The primary supervisor comprises a search-horizon based online optimizer to tune the frequency-driven power splitting rules, subject to fuel economy, health degradation, and storage violation. Subsequently, a droop-adjustment procedure is integrated as secondary supervisor to realize the storage limitations. An in-depth qualitative analysis yields a global propulsion configuration with a suitable compromise among ownership price, fuel economy, and health degradation, highlighting the efficacy of the proposed approach. At the OEMS level, compared to competing variants of frequency-driven power splitting methods, the expected improvements in fuel consumption and health degradation costs can approximately reach 14% and 29% in the studied driving environments.