Advanced Materials Research Vol. 827

Abstract: With the constraint of maximum light-concentrating efficiency, we designed a condenser for a 70 kW high-flux solar simulator. The mathematical models of the optical condenser unit and system were established to determine the condenser shape parameters.The Monte Carlo ray-tracing method was applied to compute the the light-concentrating efficiency for the condenser. It is shown that the truncation angle is the major parameter to influence the light-concentrating efficiency.When the truncation angle is 60 degrees, the condenser aberration is balanced by the truncation loss to reach the maximum light-concentrating efficiency.

Abstract: This work has developed a predictive control solution based on specific models for the process of ethanol distillation. The advantages of such control are relative to the prediction of the consequences of the disturbances by the model, thus enabling the control action to be done in a previous manner, resulting in the minimization of the variables fluctuation controlled by the process. This results in, among other advantages, energy economy, in the improvement of the ethanol produced and in the increasing production capacity. Another desirable characteristic in this control mode is its capacity to act in non-linear systems as is the case of the distillation columns. Finally, it must be noted that with the application of an advanced control solution, as proposed in this study, it becomes viable, in a second moment, for the ethanol plants to operate in multiple operational conditions, such as: 1) maximum energy economy (scarcity of raw material, for example) and: 2) maximum production condition (for situations with excess of materials to be distilled). The models developed in this project will consist of purely empirical models. Several tests will be done in the different types of models to measure the precision and robustness. The proposed control strategy demonstrated be able to control selected control loops adequately. Steam savings and reduction of product losses were observed.

Abstract: Concentrated solar thermal power generation is becoming a very attractive renewable energy production system among all the different renewable options, as it has have a better potential for dispatchability. Thus, of all components, thermal storage is a key one. However, it is also one of the less developed. The appropriate heat transfer fluid and storage medium is a key technological issue for the future success of solar thermal technologies. Molten salt as the most promising thermal energy storage medium in large-scale industrial application, the method which can improve the thermal storage ability should be proposed. But studies on this area are rare.This study will lay a foundation for the application of gold nanoparticles in molten salt which can remarkably improve the thermodynamic property. Thermal analysis methods and scanning electron microscope (SEM) are utilized to provide a review of the gold-salt composite materials microstructure.

Abstract: In this study, commercially available a diesel fuels were blended with the biodiesel produces from two different vegetable oils (sunflower, soybean). The blends (B5, B10, B20, B40, B60, B80) were prepared on a volume. The key fuel properties such as density and viscosities of the blends were measured by following ASTM test methods. Least-squares statistical regression on densities and viscosities data from each of the biodiesel/diesel blend sets revealed highly linear relationships (R2 > 0.99). For all blends, it was found that there is an excellent agreement between the measured and estimated values of the density. The results indicated that accurate prediction of density and viscosities of the blends was most effective when applied to blends prepared from the same fuel-types as the model systems used to develop the predictive equations.

Abstract: This paper proposes a mathematical programming based approach for optimal estimation of photovoltaic cell model parameters. In this study, solar cell models are used to represent the current-voltage characteristics of the solar cell. The model is represented as a non-linear function that relates the cell current and voltage with some parameters to be estimated. No direct general analytical solution exists for such function. Given the input-output characteristic data of the solar cell, a mathematical programming technique is used to solve a set of transcendental equations to optimally estimate the solar cell parameters.

Abstract: To study the distribution of remaining oil inside meandering channel sand body, the size of sand body architecture was calculated by the use of sedimentary facies, dense well, river parameters, cores, well logs and other data. The architecture of meandering channel that was crescent-shaped in plane and diagonal type in section was identifiable. On the base of study of architecture, the shielding of interlayer was classified into four types by the observation of oiliness interlayer. Framework of seepage flow was identified in meandering channel sand body. Several lateral accretion bodies between the completely choked interlayer constituted the flow unit. Combined with core analysis, the remaining oil in meandering channel sand body distributed in the upper and the middle of flow unit which did not connect with production well. The oil displacement efficiency in the flow unit was a positive rhythm in the flow unit. The oil displacement efficiency was a high-contrast positive rhythm in the lateral accretion body shielded by completely choked interlayer. That was a low-contrast positive rhythm in the lateral accretion body shielded by partly choked or restricted interlayer. All of these would provide guidance for developing the remaining oil.

Abstract: Ocean thermal energy conversion (OTEC) is a form of solar energy that can produce electricity on a non-intermittent basis. In this paper, a regionally disaggregated global energy system model with a detailed treatment of the electricity supply sector is used to examine the competitiveness of OTEC technologies for each of 48 world regions over the period to 2050 under a constraint of halving global energy-related CO₂ emissions in 2050 compared to the 2000 level. It is first shown that an over 20% reduction in the reference OTEC electricity generation costs would enable OTEC technologies to account for a noticeable share of the global electricity generation by 2050 under the CO₂ constraint. It is then shown that by-products from OTEC technologies could significantly enhance their cost competitiveness in the global electricity generation sector. It is finally shown that southeastern Asia (mainly Indonesia and Timor-Leste), Latin America (mainly Central America), and Oceania are the regions attractive for the deployment of OTEC technologies.

Abstract: Based on transient heat transfer theory and finite element method, a 3D finite element model was created to simulate the heat transfer of the vertical U type berried pipe of the ground source heat pump system. At the same time, the pipe algorithm applied successfully in the numerical simulation of concrete temperature field was introduced. The corresponding program was written. Taking the true experiment conditions as the input data and boundary condition of the computation model, the 3D dynamic simulation of the heat transfer between the berried pipe and sandy soil was carried out. The calculated temperatures of the output water of the pipe and the measure points in soil at different times met the experiment results very well, which verified the effectiveness and the reliability of the algorithm and the model. Beneficial exploration is made for providing more detailed and accurate data for the designer.

Abstract: We studied moisture determination in bituminous coal and lignitic coal samples using near-infrared (NIR) spectra. This research was developed by applying partial least squares regression (PLS) and discrete wavelet transform (DWT). Firstly, the NIR spectra were pre-processed by DWT for fitting and compression. Then, the compressed data were used to build regression model with PLS for moisture determination in coal samples. Compression performance at different resolution scales was investigated. Using the compressed data, PLS can obtain more accurate result than using raw spectra. The number of principal component in PLS model was investigated too. The results show DWT-PLS can obtain satisfactory determination performance for moisture analysis in bituminous coal and lignitic coal.

Abstract: In search of alternatives for replacing fossil sources with renewable ones, intensive construction of biogas cogeneration power plants started in Latvia in 2008. Maize silage and manure are the most popular substrates used, yet, other alternatives are searched for and tested. It has to be assessed how the energy sector sustainability strategy can impact resource management in the agriculture sector. The aim of this paper is to determine how the introduction of the biogas station in typical agricultural complex consisting of farm and arable land has affected its material productivity. In this paper the biogas production impact on material flows and productivity were evaluated by applying material flow analysis to the case study object which is a traditional intensive farm in Latvia but now reoriented towards the production of electrical and thermal energy. The case study showed that introduction of the biogas station into the traditional farm caused materialization of this economic system, because eco-efficiency (economic output divided by material input) decreased by 41%. The main conclusion is that the biogas production from the biomass is favourable from energetic point of view but current renewable-energy policy in some cases can cause inefficient use of materials putting pressure on surrounding environmental systems and resource depletion.