Elisangela D’Oliveira – Investigation of heat transfer enhancement in thermal storage systems with phase change materials
Supervisor: Dr Carolina Costa
The global concerns towards the energy crisis has become major flashpoint in recent years, thus, one of the major challenges to be tackled between the engineering community is to reduce the gap between the global demand and the supply of energy. The renewable technologies play a bigger role in the future of energy, however, due to the stochastic nature of the renewable resources have led the need of developing reliable and effective energy storage systems.
The aim of this research is to conduct a comprehensive investigation and seek the most cost-effective materials and methods to enhance the thermal conductivity of the low and medium temperature phase change materials (PCM), focusing on developing a small-scale thermal energy storage (TES) for commercial and industrial applications. The success of this research will promote a wider utilisation of the renewable technologies.
TES are systems that can store heat or cold to be used at a later time. The type of TES that is going to be analysed in this study is the ‘latent heat’, which uses PCM due to their property of releasing and absorbing energy with a change in physical state.
PCM are known to have a low thermal conductivity, thus, initially the focus will be to investigate the enhancement of heat transfer by integrating ‘nanoparticles’ to the PCM. The nanoparticles being investigated include metals, metals oxides, nanoplatelets and so on. The characterization techniques that will be used to analyse the thermo-physical properties of the PCM include:
-SEM to investigate the microstructure of the sample.
-DSC to to analyse the phase-change temperatures and latent heat of the PCM and the PCM integrated with nanoparticles, allowing an analysis to be made on how the properties of the PCM were changed by the integration of the nanoparticles.
Jayne English – Green solar cells
Supervisor: Dr Elizabeth Gibson and Dr Pablo Docampo
Due to the energy crisis we are currently facing, alternative energy sources are being explored for a more renewable source, one area being explored is solar power. The harvesting of light for power conversion in solar cells requires sunlight which is a natural source, making this a type of renewable power. However, the production of solar cells requires intense conditions and highly toxic, nonabundant materials. An example of this is the lead element which is present in perovskite, due to the toxic nature of this material. Also some solar cells use materials such as indium and gallium which are rare and expensive. In this project, I will try to develop solar cells which are truly green, by replacing current materials with earth abundant and environmentally benign alternatives. This will be completed by looking for similar materials which would offer the same advantages of current elements used, without the health or environmental risks. While looking for these alternative materials, the possibility of using recycled sources will be considered. This could include looking into wastewater streams or battery recycling, with different modes of extraction for the relevant materials. This consideration will help aid the development of a circular economy. The extraction techniques will be chosen based on high yielding processes while also considering the environmental costs.
Ella Fidment – Optimisation of electrocatalytic reduction of CO2 to multi-carbon products
Supervisor: Dr Eileen Yu and Dr Elizabeth Gibson
My research project is the optimisation of the electrocatalytic reduction of CO2 to multi-carbon molecules. The opportunity with this technology is to generate chemical feedstocks from CO2 using excess renewable energy, enabling the conversion of electrical to chemical energy and offering a method of energy storage. Current barriers to the realisation of electrochemical reduction of CO2 are high energy inefficiency, low selectivity and competition with H2 evolution. With regards to selectivity, desirable multi-carbon products, such as ethylene and ethanol, are harder to evolve due to the high energy requirement of the C-C coupling reaction in comparison to C1 products. Initially, my research will investigate the use of sequential catalysis in the form of binary/ternary metal/ metal oxide based catalyst to promote individual reaction intermediates to enable the overall reaction of C2 products to run at lower potentials and to favour specific mechanisms to improve selectivity. Further research will be conducted to examine areas of optimisation for the design of the cell as the energy efficiency and selectivity of the products are due to the influence of all the cells’ parameters.
Miriam Fsadni – Intermolecular charge transport: A novel design paradigm
Supervisor: Dr Tom Penfold and Dr Pablo Docampo
Hybrid perovskite solar cells are a rapidly advancing photovoltaic technology with power conversion efficiencies of 25.2%, and 28% within silicon-based tandem cells, already achieved. Their high efficiencies, use of naturally abundant low-cost starting materials and scalable printing techniques make them attractive as potential alternatives to conventional Si-based solar cells
The organic hole transporter material (HTM) used, plays a major role in controlling the overall performance and cost of these devices. One challenge is charge recombination, due to charge build-up at the HTM/perovskite interface, which limits efficiency of the solar cell. In addition, state-of-the-art HTMs, such as Spiro-OMeTAD and PTAA, are expensive and difficult to synthesise reducing commercially viability.
As a result, inexpensive aromatic amide, azomenthine and hydrazone-based HTMs have been developed, employing simple Schiff-base condensation chemistry, the structures of which can be tuned (e.g. changing the core) in order to optimise performance. The organic hole transporter material (HTM) used, plays a major role in controlling the overall performance and cost of these devices. One challenge is charge recombination, due to charge build-up at the HTM/perovskite interface, which limits efficiency of the solar cell. In addition, state-of-the-art HTMs, such as Spiro-OMeTAD and PTAA, are expensive and difficult to synthesise reducing commercially viability. As a result, inexpensive aromatic amide, azomenthine and hydrazone-based HTMs have been developed, employing simple Schiff-base condensation chemistry, the structures of which can be tuned (e.g. changing the core) in order to optimise performance.
My PhD studentship, ‘Intermolecular charge transport: A novel design paradigm’, combines experimental work, together with computational and theoretical chemistry to investigate the properties of organic HTMs that relate to performance and rationally design improved organic HTMs for use in hybrid perovskite solar cells.
Matthew Naylor – Tailoring interfaces in Earth abundant thin film solar cells
Supervisor: Dr Guillaume Zoppi
Crystalline silicon is by far the dominant photovoltaic (PV) technology with a clear stronghold on the market for the foreseeable future. Thin-film technology, although already less energy intensive to fabricate, must appeal to alternative applications such as low-cost roll-to-roll manufacturing and flexible solar cells if it is to significantly penetrate the market. Currently, the light absorbing layer in both commercial thin-film PV technologies contains at least one element which is either toxic, expensive or limited in supply.
Copper zinc tin sulphide (CZTS) is an alternative semiconducting compound which has gained an increasing amount of interest in recent years due to the non-toxic and earth abundant nature of its constituent elements. CZTS is well suited as an thin-film absorber material by virtue of a high absorption coefficient as well as a direct energy band gap close to the optimum energy value – an apt combination to harness a good proportion of the solar spectrum we receive from the sun. CZTS can be a challenging material to work with as during high fabrication temperatures the compound can decompose into secondary phases as well defects forming in the crystalline material. Boundaries between crystal grains as well as interfaces between layers can promote recombination of the charge carriers – a detrimental event effecting device performance.
This project aims to study the interactions at different interfaces about and within the absorber material and tailor neighbouring layers to advert detrimental processes from occurring. Some strategies employed in literature currently are: thin intermediate layers acting as diffusion barriers, alternative buffer layer materials to improve energy band gap alignment and alkali doping to passivate grain boundaries – plus many more strategies as advances in technology makes them accessible!
Ewan Matheson – Atomically thin layers for energy harvesting and storage
Supervisor: Dr Neil Beattie
Hydrogen has the highest energy per mass of any fuel, however with low volumetric density, it poses challenges for storing sufficient quantities for practical application. In order to advance hydrogen as a fuel and fuel cell technology, it is crucial to investigate efficient storage methods. For this project, ZnO nanostructures will be explored as an enabler for H2 storage. This will work by forming a nano porous medium of ZnO nanowires whereby H2 will be physiosorbed into the pores by weak Van Der Waals interactions, allowing for efficient charging and discharging of the H2 storage device.
To synthesise this device, two methods will be explored; firstly, self-assembly of the nanorods using CBD process grown on an ALD seed layer and secondly, direct evaporation of Zn using an Argon carrier gas within a quartz tube furnace. Potential challenges to consider for this project are the possibility of high energy chemisorption bonds forming at the oxygen sites, which will be detrimental to the discharging efficiency, and the growth optimisation for the pore size, such that pores may act as a potential well, trapping or refusing H2. Computational methods, such as Grand Canonical Monte Carlo simulation may help with the growth optimisation and pore sizing.
To monitor the uptake of H2, this project will explore the implementation of a 2D electron gas sensor using a TiO2-Al2O3 quantum well. This will be explored in two ways; firstly, depositing the ZnO seed layer on the Al2O3 using ALD and growing the nanorods using CBD, or depositing the TiO2 layer on the ZnO nanorods by using ALD. The uptake of hydrogen will be monitored by applying a bias across the electron gas and monitoring changes in the current density between the two electrodes.
Ian Brewis – Designing the materials for production of tailored and sustainable aviation fuels from waste CO2 and water
Supervisor: Dr Shahid Rasul
The project, titled “Designing the materials for production of tailored and sustainable aviation fuels from waste CO2 and water”, aims to use both experimental and computational methods in order to improve electrocatalyst selectivity of reaction products produced during the electrolysis of CO2 saturated water and the design of novel electrocatalysts able to produce sustainable kerosene from waste CO2.
Ryan Voyce – Low cost nanostructured antimony selenide for embedded energy systems
Supervisor: Dr Vincent Barrioz
My research is focussed on the fabrication of antimony selenide solar cells with the aim to eventually decouple the absorber material from planar substrates. In order to achieve this, a few different devices structures and fabrication methods have been proposed. The first device will be fabricated using a thermal evaporation method for the thin film and crafting the overall cell into a superstrate configuration.
The second device will be looking at depositing Sb2Se3 around ZnO nanorods in a superstrate configuration using a hydrothermal deposition method. This is one of the devices for which a decoupling is proposed. ZnO nanorods will be grown on optical fibres in order to increase light collection surface area and reduce the dependence on electron diffusion length.
The third device will be structured as Sb2Se3 nanorods, with a thin TiO2 layer and a CdS layers acting as a double buffer layer, in a substrate configuration. Currently, the most effective deposition method for Sb2Se3 nanorods is close spaced sublimation (CSS) but a solution-based method will be investigated.
In addition, models with be created in order to compare the theoretical characteristics of the devices against the experimental fabrication. This should reveal areas in which device fabrication can be improved. Further optimisation for device efficiency can also be considered, the buffer layer materials may be changed i.e. removing the toxic CdS layer and replacing it with another suitable material, such as SnO2.
Rhys Williams – Low-Dimensional Hybrid Materials for Energy Storage Technologies
Supervisor: Dr Michael Hunt
My research is on the development of nanostructured electrodes for energy storage devices such as supercapacitors. Supercapacitors possess high cycling lifetime and power density, but poor energy density compared with batteries. The initial focus of the project will be to develop routes to improve supercapacitor energy density using materials and fabrication techniques that are as green and sustainable as possible. The first route to be explored will be hybridising the electric double layer capacitance of graphene electrodes with electrochemical pseudocapacitance from metal oxides (e.g. manganese oxide). Supercapacitors have applications in stabilising the power grid (for example in response to the variable outputs of wind and photovoltaics) or in regenerative braking systems in electric vehicles – improved performance has potential to further widen their use.
My work includes the production of nanomaterials, their characterisation via techniques including Raman spectroscopy and electron microscopy, and their incorporation into cells for electrochemical testing via cyclic voltammetry and chronopotentiometry.
Cai Williams – Modelling of high performance OPVs with integrated storage
Supervisor: Dr Chris Groves
Organic photovoltaics have long been touted as a possible replacement for traditional silicon photovoltaics, due to their possibility of achieving high efficiencies whilst having low production costs, and therefore much work has been dedicated to the development of organic photovoltaics. An avenue that might achieve this promised high efficiency is tandem organic photovoltaics. Tandem organic photovoltaics are essentially comprised of two organic photovoltaics stacked on top of each other. Thus, allowing for a greater proportion of the solar spectrum to be captured, achieving a higher overall efficiency for the device as a whole. Unfortunately, much of the development of tandem organic photovoltaics has been left to empirical methods, due to a lack of device modelling tools. Therefore, this project aims to develop modelling tools for researchers. Allowing for a better understanding of the performance of their devices, leading to a less empirical approach to their development and increased efficiencies.
Oliver Rigby – Ferroelectric solar cells for Terra Watt electricity generation
Supervisor: Dr Budhika Mendis
Thin film solar cells have found a new way into the photovoltaics market owing to their low manufacturing costs and flexible designs. In order to reach terawatt scales of electricity generation, solar cells are needed that are made of abundant, non-toxic and cheap materials. This project turns to the naturally occurring ferroelectric materials bournonite (CuPbSbS3) and enargite (Cu3AsS4) for inspiration. Ferroelectrics show macroscopic electric fields which can be used to drive charge separation. This phenomenon shows potential to produce open circuit voltages which are larger than the band gap of the materials. Excitingly, this could lead to efficiencies which exceed the Schockley-Quessier limit.
During this project, bournonite and enargite will be fabricated using hot injection, a technique which Northumbria has expertise in. Thin film solar cells will be developed using bournonite or enargite as a p-type layer, with cell design motivated by CZTSSe. These minerals have been researched very little and so there is a lot of new ground to cover with them. To add to the literature they will be fully characterised for their optical, structural and electronic properties. In order to appeal to industry as much as possible, replacements for the toxic elements (Pb and As) will be doped into the samples.
Dominic Shiels – Polyoxometalate mediators for flow anodes in electrolytic water splitting
Supervisor: Dr John Errington and Dr Mohamed Mamlouk
This project will develop robust catalysts for electrocatalytic water splitting to produce hydrogen for sustainable energy solutions, using polyoxometalates (POMs) of vanadium, molybdenum and tungsten as alternatives to expensive precious metal catalysts.
Several POMs have shown high activity in water oxidation. These POMs generally contain one or more redox active first row transition metal atom(s) (e.g. cobalt or manganese) incorporated into the molecular metal oxide framework. In this project a synthetic pathway to both existing and novel first-row transition metal substituted POMs will be refined and the resultant POM-based electrocatalysts will be used for the oxygen evolution reaction in a new type of reactor.
Combining POM synthesis, reactivity and electrochemical studies with cell testing, the project will build upon recent results in POM chemistry (Errington) and electrolyser engineering (Mamlouk), in collaboration with Dr K. Johnson (solid state NMR, Durham University) and Professor J. R. Galan-Mascaros (ICIQ, Tarragona) to establish optimum electrolysis conditions and anode configuration.