Cash flow prediction using artificial neural network and GA-EDA optimization

Cash flow models are one of the spotlights for evaluating a project. The actual data should be modeled then it could be used for the prediction process. In this paper, 996 airplane maintenance basis data are used as a database, and 119 similar data are chosen after clustering. The project is divided into 20 equal periods and first three periods are used for simulating the next point. The predicted data for each point is achieved by using of previous points from the beginning. The model is based on artificial neural network, and it is trained by three algorithms which are Genet-ic Algorithm (GA), Estimation of Distribution Algorithm (EDA), and hybrid GA-EDA method. Two dynamic ratios are used which are dividing the population into two halves, and the other is a ratio without dividing. The ratio would give a proportion to GA and EDA models in the hybrid algorithm, and then the hybrid algorithm could model the system more accurately. For each algorithm, three main errors are calculated which are mean absolute percentage error (MAPE), mean square error (MSE), and root means square error (RMSE). The best result is achieved for hybrid GA-EDA model without dividing the population and the MAPE, RMSE, and MSE values are %0.022, 28944.59 Dollars, and 837789503.79 Dollars, respectively

Concentrating photovoltaic thermal (CPVT) collectors and systems: Theory, performance assessment and applications

Concentrating photovoltaic thermal (CPVT) collectors and systems are very popular in both domestic and industrial solar energy applications. CPVT collectors provides incomparably greater thermal and electrical outputs compared to stand alone PV or hybrid PVT systems as incoming solar energy is maximised inside the unit via energy-efficient concentrators. Within the scope of this paper, a comprehensive review on CPVT collectors and systems is proposed. For an easier assessment of the findings through state-of-the-art analyses on CPVT collectors, the review is presented in a thematic way. Historical overview of the technology is followed by the detailed description of a CPVT collector with main system elements and thermodynamic performance definitions. The review also covers thermal and electrical performance analysis of CPVT collectors using water or air as working fluid, analytical, numerical, simulation and experimental works for performance evaluation of different design configurations of CPVT systems and qualitative analysis of electrical and thermal energy generation. The impacts of concentrator type and concentration ratio on system efficiency, operating temperature and coefficient of performance (COP) are analysed in detail. It is observed from the findings that CPVT collectors are promising devices in market, and they have a good potential to be competitive with conventional power generation systems in the near future. © 2017 Elsevier Lt

Performance Assessment of Nano-enhanced Phase Change Material for Thermal Storage

The use of nano phase change material in thermal energy storage applications appears promising, but the often-poor performance and the lack of understanding of the heat transfer mechanisms interconnectedness remains a challenge and hinders their widespread integration. The existing numerical work has unveiled numerous impediments in predicting the actual melting behaviour. They rarely combine the effects of conduction enhancement, convection degradation, and latent heat reduction, due to inaccurate characterization of the thermophysical properties and the limitations of their model assumptions. In the present study, an enhanced numerical approach was developed to investigate the melting performance of xGnP-octadecane filled in a vertical cylindrical enclosure at different weight concentrations. The model results for the pure phase change material were compared and validated against the experimental data. The progression of the melting front, temperature probes, energy storage capacity and heat transfer rate of the nano phase change material were thoroughly evaluated. The current numerical observations demonstrate that the addition of nanoparticles improves, up to a critical concentration of 0.5wt%, the melting rate. The results showed that by adding 0.5wt% of xGnP in the base phase change material (octadecane), the melting rate decreases by 9.7% and the heat storage rate increases by 12.6%. However, at higher loadings, the heat transfer rate is deteriorated due to worsening of other thermophysical properties provoking the prevalence of viscous forces over natural convection and latent capacity. The system overall efficacy was found to be dependent on the net effects of relative changes of all thermophysical properties with nanoparticle concentration and temperature in the solid, so called mushy, and liquid zones. Finally, when characterizing nano phase change material, the thermal conductivity cannot be considered alone as a criterion for nano phase change material selection. A high thermal conductivity is needed for maximum heat absorption in thermal transport applications. Nevertheless, low viscosity, high latent heat and specific heat capacities are also essential to ensure a better thermal energy storage efficiency in terms of capacity and heat extraction/release rate.</p

NanoPCM Based Thermal Energy Storage System for a Residential Building

Implementation of thermal energy storage (TES) systems into a building and facilities improves the performance of the heating/cooling system by reducing energy waste. Thermal performance of a TES relies on the thermophysical properties of the thermal storage medium (TSM). In the present study, a novel two-step selection model has been implemented to choose the best TSM to improve TES system performance. Various types of thermal storage media are investigated considering phase change materials combined with nanoparticles. Thermal storage capacity, heat storage rate, and thermal storage efficiency have been considered as the main selection parameters in a hierarchy method. A significant contribution of this work is the development of a modelling methodology which can be used as a material selection process or tool. It enables the selection of the most efficient TES on a case-by-case basis. This TSM selection technique adds new understanding of selection tools, and new modelling capabilities to this field. It works with a variety of building cooling/heating loads, and helps minimize the environmental impact of extracting/releasing heat to the ground in geothermal applications. The TSM includes PCM and various PCMs have been considered with a melting range of 5–11℃. A material database of 90 different nano phase change materials (nanoPCMs) has been generated by considering ten types of TSMs and nine types of nanoparticles. First, a 2D numerical model has been used to investigate the heat transfer characteristics of the TSM filled in a cylindrical enclosure with a height of 5 cm and a diameter of 1.2 cm. Fourteen different nanoPCMs were selected to further study based on their thermal storage capacity, heat storage rate, and improvement coefficient and implemented into a second numerical model (3D) to calculate the thermal storage efficiency of the designed underground TES system with a height of 20 m and a diameter of 1.5 m. Finally, a building heating/cooling load has been implemented in the numerical model to evaluate the performance of the final designed system on the ground temperature throughout five years of operation. The ground temperature and its variation have an effect on the performance of the ground source heat pump. After five years of operation simulation of the no-PCM system, the ground temperature has increased by 1.78℃ to 9.78℃. However, by adding PCM and nanoPCM, the average temperature reduced to 8.95℃ and 8.72℃, respectively.</p

Solar Chimney Power Plants: A Review of the Concepts, Designs and Performances

This research presents a comprehensive review of solar chimney power plants (SCPP) as a reliable source of renewable electricity generation. Solar chimney power plants differ from other renewable energy technologies because thermal and momentum effects result in 24-h electricity generation. However, they are influenced by a wide range of design, geometrical and operational parameters, and environmental conditions. This review evaluates the design aspects and the theoretical, numerical, experimental, and performance findings in previous works holistically and concisely. The study also extensively discusses the various optimization strategies, advantages, disadvantages, and limitations of solar chimney power plants. Energy storage aspects and hybrid system designs are also addressed in the present review in order to overcome the known handicaps and limitations of solar chimney power plants. The performance figures of the technology are clearly demonstrated as a function of the design and operational conditions, and future prospects are discussed in detail. It is hoped that designers and policymakers will gain valuable insight into the technological features and advancements of solar chimney power plants, assisting them in making a better-informed decision

Solar chimney power plants: A review of the concepts, designs and performances

This research presents a comprehensive review of solar chimney power plants (SCPP) as a reliable source of renewable electricity generation. Solar chimney power plants differ from other renewable energy technologies because thermal and momentum effects result in 24-h electricity generation. However, they are influenced by a wide range of design, geometrical and operational parameters, and environmental conditions. This review evaluates the design aspects and the theoretical, numerical, experimental, and performance findings in previous works holistically and concisely. The study also extensively discusses the various optimization strategies, advantages, disadvantages, and limitations of solar chimney power plants. Energy storage aspects and hybrid system designs are also addressed in the present review in order to overcome the known handicaps and limitations of solar chimney power plants. The performance figures of the technology are clearly demonstrated as a function of the design and operational conditions, and future prospects are discussed in detail. It is hoped that designers and policymakers will gain valuable insight into the technological features and advancements of solar chimney power plants, assisting them in making a better-informed decision