Invited Speakers

Abstract: Thermoelectric refrigeration units based on the Peltier effect are gaining relevance in some applications where these units are operating in specific conditions, such as moving units, needs for low emissions, and needs for silent operation. These conditions restrict the application of traditional vapour compression refrigerators, which are relatively more efficient technologies in normal conditions.
The assessment of the thermoelectric refrigerator unit is carried out in various ways by using analytical or computational models. This presentation addresses an analytical example of a thermoelectric refrigerator model constructed by using the electro-thermal analogy, as well as the equivalent electric circuit of the thermoelectric unit. Then, the energy indicators (cooling capacity, input electrical power, the figure of merit, and coefficient of performance) are highlighted to represent the design and performance of the thermoelectric cooler located inside the refrigeration unit. Furthermore, the main methods to improve the thermoelectric cooling performance considering high-performance materials, specific design aspects, and appropriate temperature control systems, are addressed.

Abstract: Vibration Energy Harvesters are emerging devices that are able to scavenge otherwise wasted energy from ambient vibrations. In the last years, vibration harvesters have been proposed for a large number of applications, such as industrial applications, medical implants, embedded sensors in buildings and bridges and regenerative shock absorbers. In particular, in the future, vibration harvesters could be fundamental for the development of Internet of Things applications and for Industry 4.0 revolution. The performances of Vibration Energy Harvesters are strongly affected by the variability of the applied mechanical excitation source from which energy is harvested. When the vibration characteristics change with time, also the optimal operating point of the system changes with time. Such an optimal operating point is characterized by the highest value of the extracted electrical power and it is called Maximum Power Point (MPP). Hence, due to the time varying nature of the vibrations characteristics taking place in nearly all practical cases, MPP Tracking (MPPT) is mandatory in order to avoid the waste of precious available energy. In order to connect Vibration Energy Harvesters to DC electronic loads the rectification of their AC output voltages is needed. AC/DC power electronic interfaces can be passive or active. In this presentation, MPPT techniques for both passive and active AC/DC architectures will be presented and discussed.

Abstract: The 3D microstructure of porous electrodes plays an important role in the performance of electrochemical energy devices including fuel cells, batteries and electrolysers. Computational models are useful as they can provide a direct link between microstructure properties and the complex transport phenomenon and electrochemical performance [1]. A three-dimensional (3D) pore-scale lattice Boltzmann modelling (LBM) framework has been developed at University of Surrey to simulate the transport mechanisms of gases, liquid electrolyte flow, species and charge in the porous electrodes [2-4], coupled with electrochemical reactions at the interface of electrode materials and electrolyte. In this talk we will demonstrate the applications of this modelling framework in proton exchange membrane fuel cells (PEMFCs), redox flow batteries (RFBs), and lithium ion batteries (LIBs).

The LBM model was firstly developed to simulate the gas-liquid two phase flow in the gas diffusion layer (GDL) of PEMFCs, with electrochemical reactions at the catalyst layer included [2]. The model can capture the flow pathways of water and predict the local concentration of oxygen and water within the GDL. The benefit of having a microporous layer is clearly shown, to facilitate the flow of water generated at the CL away, making more reaction sites available and improving the electrochemical performance [2].

The LBM model is also developed to simulate a vanadium based RFB. It is found that the electrochemical performance is reduced with air bubbles trapped inside the electrode [3]. To validate the model, the simulated pressure drop and electrochemical performance are compared against the experimental measurement based on the same electrode structures [4]. Three electrode structures (SGL paper, Freudenberg paper, Carbon Cloth) are reconstructed from X-ray computed tomography (CT). These electrodes are used in an organic aqueous RFB based on TEMPO. Excellent agreement is achieved between the simulated and experimentally measured electrochemical performance, indicating the validity of our model [4]. The effects of different porous structures on the performance are also investigated and discussed.

The 3D pore-scale LBM framework has been further modified and adapted to simulate LIB electrodes. The model is able to simulate the complex transport processes within real electrode geometries and predict electrochemical performance. Li distribution profiles within active materials and the liquid electrolyte are derived [5]. Furthermore, we demonstrate that the model can capture how Li distribution changes with charging/discharging time, and how different microstructures affects this process [5]. The model can be used to understand the impact of electrode microstructure on electrode performance, and lead to design principles for creating electrodes with optimal microstructure for LIBs applications.

Keywords: Porous electrodes, proton exchange membrane fuel cells, redox flow batteries, lithium ion batteries, 3D pore-scale lattice Boltzmann model

References:
[1] D. Zhang, A.Bertei, F.Tariq, N. P. Brandon, and Q. Cai Progress in 3D electrode microstructure modelling for fuel cells and batteries: Transport and electrochemical performance, Progress in Energy 1 (2019) 1-35. doi: 10.1088/2516-1083/ab38c7
[2] D.Zhang, Q.Cai, and S. Gu, Three-dimensional lattice-Boltzmann model for liquid water transport and oxygen diffusion in cathode of polymer electrolyte membrane fuel cell with electrochemical reaction, Electrochimica Acta 262 (2018) 282-296. doi: 10.1016/j.electacta.2017.12.189
[3] D. Zhang, Q. Cai, O. O. Taiwo, V. Yufit, N.P. Brandon, and S.Gu, The effect of wetting area in carbon paper electrode on the performance of vanadium redox flow batteries: A three-dimensional lattice Boltzmann study, Electrochimica Acta 283 (2018) 1806-1819. doi: 10.1016/j.electacta.2018.07.027
[4] D.Zhang, A. Forner-Cuenca, O.O. Taiwo, V.Yufit, F. R. Brushett, N. P. Brandon, S. Gu, and Q. Cai Understanding the role of porous electrodes in redox flow batteries by an experimentally validated 3D pore-scale lattice Boltzmann model, Journal of Power Sources 447 (2019) 227249. doi:10.1016/j.jpowsour.2019.227249
[5] D. Zhang, W. Liu, C. Wu, and Q. Cai, Three-dimensional lattice Boltzmann modelling of the electrode performance of lithium-ion batteries, under review.

Abstract: The ability of the regulation and control of phase change materials (PCMs) to the environment temperature is directly related with its phase transition behaviors. This work presents a smart PCMs composite by the preparation of graphene oxide-modified hydrate salt/poly(acrylamide-co-acrylic acid) copolymer hydrogel (GO-EHS/PAAAM) form-stable phase change composite, in which the smart thermal properties are achieved by tailoring the phase transition behaviors of the hydrate salt PCM based on the physical and chemical interaction of GO and PAAAM with the hydrate salt. The DSC results show that the single endothermic peak of a pure hydrate salt has been changed into two interconnected peaks of the GO-EHS/PAAAM composite. The corresponding mechanistic analysis was validated by SEM, FT-IR and Raman spectra measurements. Moreover, the thermal conductivity of GO-EHS/PAAAM is increased by 54% with 2 wt% GO incorporated. In addition, the chemical and thermal stability of GO-EHS/PAAAM has been highlighted when subjected to 300 freeze-thaw cycles.

Abstract: Through passively emitting excess heat to the outer space, radiative cooling has been demonstrated as an efficient way for energy saving applications. Instead of well-designed photonic structures, we rediscovered the potential of bulk materials as inrafred emitter for sub-ambient daytime radiative cooling. Two kinds of infrared emitters are proposed in this presentation: one with broadband infrared emission and another with selective infrared emission. The broadband one is composed of bulk polyvinyl fluoride (PVF) layer and Ag coating, and a solar absorptance below 10% and infrared emittance over 90% is achieved. On the other hand, the selective emitter is composed of a 1-mm-thick lithium fluoride crystal coated with Ag backing, and a solar absorptance below 5% and nearly ideal infrared selectivity with high emission exactly within the atmospheric transmission band (i.e., 8–13 μm) could be obtained. Potentially, the proposed selective emitter could reach a very low equilibrium temperature with 57 K below the ambient one. Both theoretical calculations based on energy balance and outdoor tests demonstrated the ability of these two infrared emitters to achieve sub-ambient daytime radiative cooling, which were mainly caused by the intrinsic optical properties of these two bulk materials. More details about the calculation process, experimental setup and cooling performance will be introduced in this presentation. We hope these scalable radiative coolers with low fabrication cost could find broad applications in energy saving areas.

Abstract: Oily sludge refers to the sludge mixed with crude oil, various refined oil residue and other heavy oil, which is widely produced in the process of crude oil exploitation and transportation with output of 5 million tons every year in China. The harmless and recycling utilization of oily sludge has become a significant issue in oil field development. Pyrolysis is a promising technology to treat oily sludge. However, the conventional pyrolysis technology has the problems of high energy consumption, low efficiency and low quality of pyrolysis products, which restrict its further utilization. Co-pyrolysis of biomass and oily sludge for high quality products was proposed to realize the polygeneration utilization of biomass and oily sludge by the complementary of material properties. The mechanism of the co-pyrolysis was investigated based on the effects of biomass components and blending ratio. The quality of oil, char and gas products were significantly improved. The oil has the potential to be used as fuel because of the higher contents of gasoline, kerosene and diesel components. The gas can be used as fuel gas, and the char with better pore structure can be further developed as catalysts or electrode materials. Polygeneration application of co-pyrolysis is a promising technology that can facilitate the development of bioenergy and the clean production of petroleum industry. Currently, how to realize the amplification of the co-pyrolysis technology for industrial application is an urgent problem to be solved.

Keywords: oily sludge; biomass; co-pyrolysis; high quality product; polygeneration application

Abstract: Research shows that low efficiency and high cost have become the biggest obstacles for solar sea water desalination technology. A novel multi-effect vertical concentric tubular solar seawater distillation device is introduced and constructed in present work. The device consists of several closely spaced concentric stainless-steel pipes, in which the feed sea water gets preheated by hot brine water to guarantee the evaporation efficiency. Apart from this, the latent heat of vapor condensation in the multi-effect mode is re-utilized successful, and result in an increasing total yield. The total fresh water production and the GOR for the four-effect mode can reach 1.04 kg/h and 3.36 at the heat input of 200 W. The fresh water price and the payback period of the device are the most important economic factors for application of any particular desalination technology. The cost of water production is about 8.6 $/ton, thus, the payback period of the device is 5 just years, which implies an excellent application prospects for single family use to rural, arid and remote communities.

Abstract: Utilization of concentrator photovoltaic (CPV) can reduce market investment cost and shorten payback time because that CPV have high photoelectric conversion efficiency and the expensive solar cells are replaced by cheap solar concentrators. As the result of the solar cells’ fixed band-gap, solar cells can only convert photon energy close to the semiconductor band-gap to electricity. Photon energy both higher and lower than the semiconductor band-gap is converted to heat and lead to severe heat load, which greatly reduces photoelectric conversion efficiency and solar cells life. The spectral splitting technology directs the photon energy close to the semiconductor band-gap to solar cells and directs photon energy both higher and lower than the semiconductor band-gap to thermal absorbers, which offers a possibility for reducing solar cells temperature, increasing photoelectric conversion efficiency and solar cells life. Herein, starting from the wavelength band and energy grade of solar energy, taking the principle of customer demands for electricity and heat cogeneration, the spectral splitting technology based on nanofluids, interference nano-thin film and semitransparent PV cell were theoretically and experimentally analysed, respectively.

Abstract: Triboelectric nanogenerators (TENGs) are promising innovative energy conversion devices that convert mechanical energy to electricity based on triboelectric friction. We developed a series of TENGs based on sponge-like porous polymer thin films such as polydimethylsiloxane (PDMS) and polytetrafluoroethylene (PTFE). The porosity effect on the output performance of the porous TENG was investigated under mechanical impacts. The output voltage of the porous TENG is obvious higher than that of the solid polymer thin film based TENG under the same condition. The porous TENG can also generate considerable electricity by harvesting mechanical energy from human motions. The generated electric energy could instantaneously power some light emitting diodes (LEDs) and other small electronics without any energy storage process. The development of the porous TENGs could open a new avenue toward developing self-powered personal electronics, owing to their flexibility, simple structure, and the ability to harvest mechanical energy from human motions.

Abstract: The Phase Change Materials (PCM) take advantage of the latent heat of the solid/liquid transition to store large amounts of thermal energy during melting or release it to the environment during solidification, barely changing their temperature. This thermal stability and storage capability makes these materials more compact and efficient than materials that use sensible heat for energy storage and thermoregulation [1,2].

A significant issue in thermal regulation and energy storage with PCM is their low conductivity. This leads to very long times during the heat storage and discharge phases, reducing their usability and performance. We present three mechanisms to enhance the heat transfer rate suitable for engineering applications. First, we show how the thermocapillary effects are a very efficient mechanism to develop convective heat transfer in microgravity and strongly enhance the performance of PCM based systems, without increasing their mass and volume [3,4]. Second, we use dispersed metallic nanoparticles in PCM to enhance the heat transfer rate, and present an empirical model able to predict the performance of nano-enhanced PCM realistically in a wide range of nanoparticle concentrations, sizes, and types [5]. Third, we show how metallic open foams are can be used in addition to convective heat transport to enhance the heat transfer rate robustly.

Finally, we present how to leverage those enhancing heat transfer mechanisms to improve current PCM designs of micro-energy harvesters. The motivation comes from the need to power low consume electronics; such as wireless sensors to monitor environmental variables, industrial processes, health parameters, etc., in places where conventional batteries are impractical. Among the different technologies aimed at power low consume sensors - as solar cells, piezoelectric devices, electrostatic methods, etc.- thermoelectric energy harvesting is one of the best solutions to create autonomous monitoring sensors. Efficient TEGs require a substantial temperature difference across the device structure. This has restricted their use to applications where a hot metal surface is available [6]. We show how coupling thermoelectric generators with PCMs in micro-energy harvesters can increase the electric energy output an order of magnitude with respect to conventional designs. In particular, we pay special attention to designs of autonomous micro-harvesters to power sensors for structural health monitoring systems in aircraft, monitoring in spacecraft, as well as humidity and temperature in soils.

Keywords: Phase Change Materials, nanoparticles, thermoelectric generators, micro-energy harvesting

Abstract: The renewable energy sources such as wind power and solar energy are widely connected to the current power grid. The proportion of the renewable energy to the entire energy sources in the power system is increasing. Since wind power and solar energy are intermittent, which have more uncertain factors, power grid operation is being impacted by installation and generation of the renewable energy sources. Energy balance or power balance is of great importance to power system operation. However, the uncertainties of renewable energy bring issues to power system power balance and dispatch. Severe power imbalance, which causes the huge frequency deviation, will lead to the stability of power system. Therefore, it is very important to deal with the uncertainties of renewable energy. The existing deterministic approaches are not sufficient to deal with the uncertain factors. This paper analyzes the effect of renewable energy uncertainties in power grid operation based on the fuzzy theory and probabilistic methods. The proper approaches to handle renewable energy uncertainty in power grid operation are recommended.

Abstract: Implementation of renewable energy resources (RES) with the use of knowledge-based approach requires systems which enable to combine data from different databases in order to multidimensional character of analysed factors. Therefore, this study provides the decision support system for the planning of hybrid renewable energy technologies designed for regional authorities. The system in this research integrates two RES: solar and wind. Moreover, it combines energy potential data with administrative division and data on land cover. Presented functionality shows the ability of single-element filtering as well as multi-element filtering which gives the opportunity visual data discovery. The novel decision support system designed in this research can constitute an effective instrument, which can help regional decision-makers to locate single-source as well as hybrid RES installations to meet the requirements of renewable energy production. The systems were designed for the case of Lubuskie Voivodeship (Poland). However, besides the fact of customized system for one region, the use of universal databases allows to prepare similar tool for any other region in European Union.

Abstract: Artificial light sources play an indispensable role in daily life. Around 1/6 to 1/5 of the worldwide electricity is consumed by lighting. [1] These lighting sources do not only need to be efficient and reliable, but high light quality is also demanded. Quantum-dot based light emitting diodes (QLED) have higher efficiency, stability, longer lifetime and wider color gamut, compared to organic light emitting diodes. Metal halide perovskite quantum dots have gained great attention for LED research, due to their high photoluminescence quantum yield, low-cost solution processability and high tunability of emission across the entire visible spectrum. [2-3] However, the toxicity and instability of lead-containing halide perovskites against moisture and air prevent further practical applications. Highly efficient lead-free halide perovskite quantum dots are still very limited, especially for single white-emitting perovskites. The efficiency and color stability of LED devices can be improved by using a single-phase white-light emitter, as it can avoid the self-absorption and color instability problems in mixed and multiple emitters.
Here we report a highly efficient lead-free warm-white emitting quantum dot Cs2Ag0.4Na0.6InCl6, crystallizing in a lead-free double perovskite Cs2AgInCl6 structure, doped with rare earth and transition metal ions. We will talk about the synthesis and luminescence properties of the perovskite quantum dots. The influence of quantum dot structure on the luminescence properties will be discussed, and the emission mechanism will be clarified by DFT calculations. Finally, the application of the white light quantum dots in QLED devices is evaluated.

Abstract: Fuel cells attract a lot of attention recently as the promising next generation electric vehicle technology. However, one of the major obstacles for commercialization of fuel cell vehicles in China is the difficulty regarding with hydrogen refuelling and storage due to lack of infrastructures. On-site hydrogen production by methanol steam reforming (MSR) is one of the possible methods to solve this problem due to the ease of liquid methanol refueling and storage, as well as high yield of hydrogen and low generation of CO (<1 vol%) in the reformate. The high temperature proton exchange membrane fuel cell (HT-PEMFC) can directly use the reformate as fuel gas since it can tolerate CO concentration up to 3 vol.% at operating temperature around 160 oC. In this study, a novel multichannel micro packed bed reactor with bifurcation inlet manifold and rectangular outlet manifold was developed to improve the MSR performance. The commercial CuO/ZnO/Al2O3 catalyst particles were directly packed in the reactor. The flow distribution uniformity in the reactor was optimized numerically. Experiments were conducted to study the influences of steam to carbon molar ratio (S/C), weight hourly space velocity (WHSV), reactor operating temperature (T) and catalyst particle size on the methanol conversion rate, H2 production rate, CO concentration in the reformate, and CO2 selectivity. A three-dimensional numerical model was established to study the heat and mass transfer characteristics as well as the chemical reaction rates. The model adopted a triple rate kinetic model which can accurately calculate the consumption and generation of each species during methanol steam reforming process in the reactor, which was validated by experimental data. The distributions of temperature, velocity, species concentration, and reaction rates in the reactor were obtained and analyzed to explain the mechanisms of different effects. The results show that increase of the S/C and T, as well as decrease of the WHSV and catalyst particle size, both enhance the methanol conversion. The CO concentration decreases as the S/C and WHSV increase as well as the T and catalyst particle size decrease. Moreover, T plays a more important role on the methanol steam reforming performance than WHSV and S/C. The impacts on CO concentration become insignificant when the S/C is higher than 1.3, WHSV is larger than 1.34 h-1 and T is lower than 275 °C. A long term stability test of this reactor was also performed for 36 h and achieved high methanol conversion rate above 94.04% and low CO concentration less than 1.05% under specific operating conditions

Abstract: In this presentation we are going to introduce the main topics of our research activities in New Energy and Future Energy Systems for cooling and air conditioning. Specifically the could be englobed into four macro-areas:
• The development of solid-state technologies for cooling and air conditioning based on the caloric effects.
• The employment of nanofluids for enhancing the heat transfer in energy systems .
• The energy and environmental impact of new ecofriendly refrigerants for cooling and HVAC vapor compression systems.
• The employment, in the HVAC systems, of renewable energy sources, specifically geothermal energy.

Abstract: Though the mining industry contributes significantly to the world economy through providing raw materials for many industries, mining operations inevitably produce a large amount of solid waste. It has been estimated that the solid waste in the mining industry accounts for ~80% of solid waste in the whole industry. The disposal of solid waste is possibly the most daunting challenge faced by the mining industry. In this presentation, different recycling methods will be introduced. The presentation starts with the utilization of ultrasonic pre-treated coal fly ash for soil amelioration. Then, the manufacturing of geopolymer using refuse mudstone, GGBS, and red mud is presented. The utilization of various solid waste as supplementary cementitious materials is explained and the recycling of solid waste as backfill materials is introduced. With the application of above-mentioned methods, the solid waste minimization and cleaner production in the mining industry will be promoted.

Abstract: As significant as the electrolyte selection is for dual-ion battery applications, the characteristics of the graphitic cathode can also be decisive for the resultant cell operation. During this work, in order to find a promising electrode-electrolyte combination for Na-based dual-ion batteries, CCCV cycling tests were applied to different positive electrode compositions to optimize the effects of carbon black and binder as well as to mitigate the irreversible charge losses, by utilizing 0.5 M NaPF6/EC:EMC electrolyte which was found to be the most promising mixture in our preceding study. Electrodes consisting of 90 wt% KS6 graphite, 2 wt% carbon black and 8 wt% binder was found to be the most promising combination, and proved its superiority over SLP 30 type graphite, delivering 86.2 mAh/g discharge capacity by means of its lower particle size and larger surface area. Moreover, structural characterization tests of Raman spectroscopy and X-ray diffraction were implemented by providing qualitative and quantitative insights so as to elucidate and characterize the PF6
intercalation/de-intercalation characteristics for our Nabased dual-ion battery. The results of the tests acknowledged that the surface and the bulk of the electrode behave differently.