Abstract

Microalgae biomass is composed of various bio‐ compounds which can be converted to biofuels. One type of solid fuel which can be derived from microalgae is biochar through torrefaction. However, the production of torrefied microalgae biochar may include environmental impact as it consumes raw materials and energy. A life cycle assessment of the production of torrefied microalgae biochar is proposed in the study using the torrefaction severity index. The results show the electricity requirement of the torrefaction largely contributes to the environmental impact and energy consumption. While the resulting global warming potential of the production of torrefied microalgae biochar using the torrefaction severity index yielded a non‐linear relation.

Abstract

Deciding the location of bio refinery is an important task for management in biofuel supply and demand. This work presents a single-period deterministic model for the optimal location of butanol refinery. The developed model considers a whole system approach for butyric acid supply, butanol refinery and delivery systems. The proposed model determines where and how many refineries to be constructed and components (butyric acid and butanol) to be transported for minimizing the expected total network cost and satisfying regional demand of biofuel. The real scenario of the biofuel demand by region in South Korea is applied to validate the mathematical model. The optimization results will help to determine investment strategies for butanol production.

Abstract

After a major event affecting the world economy, oil prices tend to fluctuate due to the event in the next few months or even years. It can be seen that oil prices may have long-term correlation. In the processing of time series, the traditional ARMA model cannot accurately describe long memory, which leads to the deviation of parameter estimation during the modeling process. In order to better describe the long memory in the time series, this paper establishes the ARFIMA model to perform fractional difference on the series, and obtains the series satisfying the zero-mean ARMA process, then estimates the parameters. Further research shows that the Caputo fractional difference process is a specialized Grunwald-Letnikov (G-L) fractional differential process. Therefore, this paper introduces the Caputo fractional L1 formula into the time series model, and constructs a new fractional difference method to deal with Brent futures price return rate and perform ARFIMA modeling. This method works better in predicting than the traditional ARMA model and the G-L differential ARFIMA model. It can provide more effective assessments in economic markets such as oil price risk measurement and control, helping investors to better avoid market risks and obtain greater returns.

Abstract

In the existing SOFC system, because of the high temperature isolation of the hot box, it is difficult to obtain the situation of the SOFC stack accurately. Therefore, the key problem of real-time judgment of the SOFC system operation state is to develop a state diagnosis method. Therefore, this paper intends to use strong classifier to evaluate the state of SOFC system, which is consist of multi weak classifiers and called AdaBoost algorithms. The algorithms can achieves efficient classification, which provides a powerful guidance for the overall performance evaluation of the system.

Abstract

Molten blast furnace (BF) slag is discharged at high temperature during the iron-making process, and contains a high content of thermal energy. Traditional water quenching methods fail to recover this thermal energy. Hence, a number of dry granulation heat recovery techniques were proposed, and reducing the particle size is regarded as the key route to improving heat recovery efficiency. Among all the proposed techniques, the centrifugal granulation method is recognized as the most promising. In this paper, the centrifugal granulation characteristics for molten BF slag in film formation mode were experimentally studied. The effect of the rotating speed, the molten slag mass flow rate and the slag initial temperature on the particle size are discussed. The results show that an unusual histioid type of film disintegration phenomenon occurs during the granulation process, which is beneficial to the fragmentation of the film. Furthermore, a higher rotating speed and a smaller slag flow rate contribute to the reduction of particle size. The present study provides guidance for improving granulation heat recovery performance for molten BF slags in industrial applications.

Abstract

The aim of this study is to perform autothermal reforming (ATR) of methanol by sprays via the h-BN Pt catalyst with cold start for the hydrogen production. The present works mainly focus on the effects of operating conditions on hydrogen production and methanol conversion. Meanwhile, the comparison between ATR and partial oxidation of methanol (POM) are also carried out. The results of POM indicate that the highest H2 and CO concentrations are obtained at O2/C (molar ratio of air and methanol) = 0.7, and the CH3OH conversion can reach 100%. In the ATR process, the methanol conversion reaches 60% under O2/C ratio =0.7 with S/C (molar ratio of steam and methanol) = 1.5. At S/C =0.5, the CH3OH conversion increases with increasing the O2/C ratio and is up to 100%, and the H2 yield is higher than that of POM. The highest H2 yield from ATR is 1.697 mol (mol CH3OH)-1 occurs at S/C =0.5 and O2/C=0.7.

Abstract

This paper proposes an improved multi-objective optimization model for building energy retrofitting. Apart from the extensively investigated objectives: minimizing the overall energy consumption and reducing the life cycle cost, another objective is involved: the overall user satisfaction during operation. The newly introduced objective reflects the fact that upon the deterioration of appliances, the user satisfaction decreases accordingly, and this must be reversed via facility maintenance. A multi-objective optimization model with all three objectives is established to support the building energy retrofitting decision making. A recently proposed many-objective optimization algorithm, NSGA-III, is employed as the numerical solver. A simulation test is conducted and the relationship between objectives are investigated.

Abstract

In the resent years, microgrid has been widely used in the world and become a good solution to the urgent energy and environment issues. However, the high cost of microgrid limits the development of microgrid. In this paper, a novel design is presented to be compared with traditional design using a contrastive framework with renewable energy considering battery lifetime and renewable energy penetration. Numerical results show that the LCOE of the novel design can be reduced by 6.23% compared with traditional design.

Abstract

This study presents the experimental and numerical simulation based characterization of a new modular solid-liquid sensible heat storage system. The field-scale storage prototype was constructed in the shallow subsurface and consists of 25 coupled 1.5 m³ storage units, each equipped with a helical heat exchanger in a cement based water saturated matrix. A charging and passive cooling experiment was performed over a period of 3 months, with a maximum storage temperature of 60°C and distributed temperature monitoring of the system. A detailed 3D finite element model of the storage system was developed and parameterized in order to analyze the governing heat transfer processes and quantitatively characterize the storage behavior. Experimentally observed and simulated storage temperatures show a good agreement, with differences of less than 2.7 K, which proves the appropriateness of the model approach. Average loading rates of 14.6 kW during the first 2 days and 4.3 kW during the following 10 days of heat charging correspond to a used storage capacity of 660 kWh and 1310 kWh after 2 and 12 days, respectively. During passive cooling the storage temperature was reduced to approximately 30°C within 30 days, which corresponds to a heat loss rate of 1.4 kW during that time and demonstrates the necessity for proper thermal insulation of subsurface heat storages.

Abstract

This study aims to examine available avenues to improve thermo-economic performance of a hybrid solar-biomass organic Rankine cycle (ORC) cogeneration plant. The ORC unit is rated at about 630 kWe, and it is related to a real solar-ORC plant which currently runs in Ottana (Italy). The implemented hybrid configuration had been conceived as an efficient way to improve dispatchability and operating hours in the aforementioned existing concentrated solar power (CSP) plant and other similar ones, through biomass retrofit. Beyond what is available in literature on hybrid solar-biomass systems, enhanced exergoeconomic analysis is performed in this study, by considering intrinsic irreversibilities and cost rates in the respective components, which are imposed by the assumptions of systemic and economic constraints, and can thus not be eliminated. Results show that relative cost rates of between 2% and 73% of total cost rates could be theoretically avoided. Also, it was obtained that investment cost rates of solar field, thermal energy storage tanks, furnace heater, recuperator and ORC preheater need be reduced, for acceptable economic performance of the hybrid plant. This type of information is highly essential for improved design and quicker market penetration of fully-renewable energy systems.