• Energy Research
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Abstract A new model of the optimum tilt angle of a soiled photovoltaic (PV) panel is proposed in this paper. The tilt angle is a key factor that influences the output power of PV panel, while dust deposition is an inevitable external element to be considered. In this paper, the solar radiation model is studied by analysing the Hay, Davies, Klucher, Reindl (HDKR) model. The cell temperature of a PV panel is also investigated to evaluate the power output. A fitting formula is derived to express the relationship between the dust deposition density and the tilt angle, and it is integrated in the output model of a fixed-type PV panel. Besides, the effect of dust deposition on the transmittance is analysed. An inverse correlation between the dust deposition density and tilt angle can be obtained, and the optimum tilt angle is calculated to maximize the power output of a soiled PV panel. Simulation is conducted by Matlab to demonstrate the validity of the proposed model of the optimum tilt angle with the shielding effect by dust. Furthermore, the relationship between dust deposition and the working temperature of PV panel is investigated by indoor experiments.

In this paper, an Advanced Dynamic Model Predictive Control (AMPC) based on a Nonlinear Model Predictive Control (NMPC) framework with a multi-objective cost function driven by dynamic weights is proposed to improve the energy performance of fuel cell hybrid electric vehicles whilst prolonging their component lifetime. By the use of dynamic weights, the cost function is effectively formulated as the combination of fuel consumption, rate of change of fuel cell power, battery power, the fuel cell efficiency, state of charge of the battery, and their temperatures. In order to enhance the adaptability of the AMPC, a Fuzzy Cognitive Map (FCM) is then newly designed to regulate online the dynamic weights to adjust the importance of each cost component according to the conditions prevailing during driving. A comparative study between the proposed AMPC, a constant weight based NMPC and a conventional NMPC having cost function with fewer objectives has been carried out by means of simulation using a FCHEV model from the simulation tool ADVISOR to illustrate the efficacy of the proposed AMPC.

To explore the mechanism of the influence of Ni-Fe bimetallic catalyst for the producing high-value carbon nanotubes (CNTs) with clean hydrogen from waste plastic pyrolysis, the pyrolysis-catalysis of plastics were performed using a two stage fixed bed reaction system with Ni and Fe loading at variant molar ratios. The catalysts and produced carbon were analysed with various characterization method, including temperature-programed reduction/oxidation, X-ray diffraction, scanning electron microscopy or/and Raman spectroscopy. Both the H2 concentration and H2 yield reached maximum values of 73.93 vol.% and 84.72 mg g−1 plastic, respectively, as the ratio of Ni:Fe at 1:3. The amount and quality of CNTs were greatly influenced by the catalyst composition, and Ni and Fe display different roles to the overall reactivity of Ni-Fe catalyst for the pyrolysis-catalysis of waste plastics. Catalyst with more Fe loading produced more hydrogen and deposited carbon, due to higher cracking ability and the relatively lower interaction between active sites and support. The presence of Ni in Ni-Fe bimetallic catalyst enhanced the thermal stability and graphitization degree of produced carbons. The thermal quality of filamentous carbons might be associated with carbon defects.

Abstract A new cooling technique for low concentrated photovoltaic–thermal (LCPV/T) systems is developed using a microchannel heat sink with nanofluids. In this study, Aluminum Oxide (Al 2 O 3 )–water and Silicon Carbide (SiC)–water nanofluids with different volume fractions are used as cooling mediums. The influence of cooling mass flow rate and nanoparticles volume fractions on the performance of LCPV/T system is investigated at different values of concentration ratio. A comprehensive model is developed which includes a thermal model for the photovoltaic layers, coupled with thermo-fluid dynamics of two-phase flow model of the microchannel heat sink. The model is numerically simulated to estimate the performance parameters such as the solar cell temperature and the electrical and thermal efficiency. Results indicate that a significant reduction in solar cell temperature is attained particularly at the high concentration ratio by using nanofluids compared to using water. Using SiC–water nanofluid achieves a relatively higher reduction in cell temperature than Al 2 O 3 –water nanofluid. By increasing the volume fraction of nanoparticles, both SiC–water and Al 2 O 3 –water nanofluids accomplish a major reduction of cell temperature. As a result, the use of nanofluids achieves higher solar cell electrical efficiency, particularly at lower Reynolds number (Re) and higher concentration ratio, than the use of water. The influence of nanofluids on thermal efficiency varies according to the concentration ratio. Furthermore, friction power increases with the increase in both Reynolds number and nanoparticle volume fraction. By increasing the volume fraction of the nanoparticle, the net electrical power increases at high concentration ratio while the thermal power decreases. The results of this study indicate that the use of nanofluids is effective cooling technique, particularly at high solar concentration ratios where the solar cell temperature reduces to 38 °C, and electrical efficiency improves up to 19%.

This study was supported by the Research Councils UK Energy programme, Grant No: EP/K011820/1 and GEA Searle, now Kevlion. The authors wish to acknowledge the cash and in-kind contributions of these organisations as well as the support received from Brunel University London and the RCUK National Centre for Sustainable Energy use in Food Chains (CSEF).

Abstract Combined heat and power (CHP) systems offer high energy efficiencies as they utilise both the electricity generated and any excess heat by co-suppling to local consumers. This work presents the potential of a combined heat and hydrogen (CHH) system, a solution where Proton exchange membrane (PEM) electrolysis systems producing hydrogen at 60–70% efficiency also co-supply the excess heat to local heat networks. This work investigates the method of capture and utilisation of the excess heat from electrolysis. The analysed system was able to capture 312 kW of thermal energy per MW of electricity and can deliver it as heated water at either 75 °C or 45 °C this appropriate for existing district heat networks and lower temperature heat networks respectively. This yields an overall CHH system efficiency of 94.6%. An economic analysis was conducted based on income generated through revenue sales of both hydrogen and heat, which resulted in a significant reduction in the Levelized Cost of Hydrogen.

Abstract Biodiesel produced from non-edible feedstocks is increasingly attractive alternative to both fossil diesels and renewable fuels derived from food crops. Date pits are one such lipid containing feedstock, and are widely available in Oman as a waste stream. This study analyses the effects of soxhlet process parameters (temperature, solvent to seed ratio and time) on the extraction of oils from waste Date pits and the subsequent production of biodiesel from it. The highest yield of oil extracted from the Date pits was 16.5 wt% obtained at a temperature of 70 °C, solvent to seed ratio of 4:1 and extraction duration of 7 h. Gas Chromatography analysis showed that Date pits oil consisted of 54.85% unsaturated fatty acids (UFA). Transesterification of the oil extracted was undertaken at 65 °C, a methanol to oil ratio of 6:1 and a reaction time of 1 h for biodiesel production. Biodiesel produced from the Date pits oil was found to have a cetane number of 58.23, density 870 of kg m−3, cloud point of 4 °C, pour point of −1 °C, CFPP of −0.5 °C and kinematic viscosity of 3.97 mm2 s−1 (40 °C). In general, Date pit oil appears to be a potential alternative feedstock for biodiesel production.

Progress of efficient thermal energy storage (TES) has become a key technology for the development of energy conversion system. Among TES technologies, sorption thermal energy storage (STES) has drawn burgeoning attentions due to its advantages of high energy density, little heat loss and flexible working modes. Based on STES, this paper presents an innovative resorption sorption energy storage (RTES), and the experimental system is established and investigated for energy storage and upgrade. 4.8 kg and 3.9 kg MnCl2 and CaCl2 composite sorbents are separately filled in the sorption reactor, and expanded natural graphite treated with sulfuric acid (ENG-TSA) is integrated as the matrix for heat transfer intensification. It is indicated that the highest energy storage density are 662 kJ/kg and 596 kJ/kg when heat input temperature is 125 °C and heat release temperature are 130 °C and 135 °C, respectively. For different heat input and release temperature, the energy efficiency and exergy efficiency range from 27.5% to 40.6% and from 32.5% to 47%, respectively. The novel RTES system verifies the feasibility for energy storage and upgrade, which shows the great potential for low grade heat utilization especially for industrial process.