• Comparative Performance Modelling of Heat Pump based Heating Systems using Dynamic Carbon Intensity

      Counsell, John; Khalid, Yousaf; Stewart, Matt; University of Chester (IET, 2018-11)
      Modern buildings and homes utilise multiple systems for energy generation, supply and storage in order to maintain occupant comfort, reduce operating costs and CO2 emissions. In recent times electricity generation and supply network (UK National Grid) have had to manage variable supply from renewable sources such as wind turbines and photovoltaics. This resulting supply mixture has a dynamic profile at intermittent times. To manage excess supply, the options are either to reduce the generation by power stations/renewables or reinforce the power infrastructure with storage capability. This has given rise to calls for electrification of services in streamlining the supply profile through intelligent demand response such as electric heating and vehicles. Furthermore, due to zero carbon energy sources with dynamic supply profile, the carbon intensity is no longer constant. This impacts the seasonal CO2 emissions calculations and also the design and performance of electrical powered heat pump based heating systems. The RISE (Renewable Integrated Sustainable Electric) heating system was developed (funded by the UK Research and Innovation), where an electrical powered Heat pump is combined with electric thermal storage allowing low cost and low carbon electricity to be utilised. For such a system more realistic performance analysis requires dynamic carbon intensity calculations to assess impact on its ability to maintain comfort, low operating costs and low carbon emissions. The paper builds upon previously published research on the RISE system comparing with domestic Gas Condensing Boiler (GCB) using static carbon calculations. This paper presents a comparison between the RISE system and standard domestic electrical powered Air Source Heat Pump (ASHP) when using static and dynamic carbon intensity profiles. The Inverse Dynamics based Energy Assessment and Simulation (IDEAS) framework is utilised for modelling and dynamic simulation of building and heating system, operating cost and estimation of annual emissions based on half hourly (HH) dynamic CO2 intensity figures rather than annual average. The results show that with dynamic carbon intensity calculations, both electric heat pump based heating systems, RISE and ASHP show a significant increase (>15%) in carbon emissions for space heating. The results also show that whilst the RISE system’s thermal storage helps to reduce running costs using a time of use tariff (TOU), it only provides a small benefit in carbon emissions.
    • Programmable logic controllers and Direct digital controls in Buildings

      Khalid, Yousaf; University of Chester (2018-09)
      The concept of programmable logic controller (PLC) originated over the last century that has revolutionised the industrial sector. In the last few decades PLC in the form of DDC has been commonly used in Building Energy Management Systems (BEMS). The contribution of this work is to analyse PLC/DDC role in the ongoing BEMS advancements in the building sector. Currently DDC are not understood by building design and simulation engineers who assess the controllability of the building in practice. This paper would enhance the understanding of integrating DDC in buildings and influence creation of better modelling and simulation tools for assessing their impact on energy performance in practice.
    • Perovskite Srx(Bi1-xNa0.97-xLi0.03)0.5TiO3 ceramics with polar nano regions for high power energy storage

      Wu, Jiyue; Mahajan, Amit; Riekehr, Lars; Zhang, Hangfeng; Yang, Bin; Meng, Nan; Zhang, Zhen; Yan, Haixue; Queen Mary University of London; Uppsala University; University of Chester (Elsevier, 2018-06-06)
      Dielectric capacitors are very attractive for high power energy storage. However, the low energy density of these capacitors, which is mainly limited by the dielectric materials, is still the bottleneck for their applications. In this work, lead-free single-phase perovskite Srx(Bi1-xNa0.97-xLi0.03)0.5TiO3 (x=0.30 and 0.38) bulk ceramics, prepared using solid-state reaction method, were carefully studied for the dielectric capacitor application. Polar nano regions (PNRs) were created in this material using co-substitution at A-site to enable relaxor behaviour with low remnant polarization (Pr) and high maximum polarization (Pmax). Moreover, Pmax was further increased due to reversible electric field induced phase transitions. Comprehensive structural and electrical studies were performed to confirm the PNRs and the reversible phase transitions. And finally a high energy density (1.70 J/cm3) with an excellent efficiency (87.2%) was achieved using the contribution of PNRs and field-induced transitions in this material, making it among the best performing lead-free dielectric ceramic bulk material for high energy storage.
    • Controllability of buildings: computing and managing energy in practice

      Khalid, Yousaf; University of Chester (Journal of Computing and Management Studies (JCMS), 2018-05)
      Modern buildings utilise multiple systems for energy generation, supply and storage in order to maintain occupant comfort. Consequently, complex computer based energy management systems are utilised for design and operation of such buildings. Often these buildings perform poor in practice in terms of energy consumption, cost and carbon emissions due to lack of thorough analysis of their controllability during the design process. This paper highlights the deficiencies in the current building design practice and the need for appropriate framework to assess controllability of buildings during design stages so that complex building energy systems are easier to manage in practice.
    • SrFe12O19 based ceramics with ultra-low dielectric loss in the millimetre-wave band

      Yu, Chuying; Zeng, Yang; Yang, Bin; Wylde, Richard; Donnan, Robert; Wu, Jiyue; Xu, Jie; Gao, Feng; Abrahams, Isaac; Reece, Mike J.; Yan, Haixue; Queen Mary University of London; Hunan University; National University of Defence Technology; University of Chester; Thomas Keating Ltd; Northwestern Polytechnical University (AIP Publishing, 2018-04-02)
      Non-reciprocal devices such as isolators and circulators, based mainly on ferromagnetic materials, require extremely low dielectric loss in order for strict power-link budgets to be met for millimetre (mm)-wave and terahertz (THz) systems. The dielectric loss of commercial SrFe12O19 hexaferrite was significantly reduced to below 0.002 in the 75 - 170 GHz band by thermal annealing. While the overall concentration of Fe2+ and oxygen vacancy defects is relatively low in the solid, their concentration at the surface is significantly higher, allowing for a surface sensitive technique such as XPS to monitor the Fe3+/Fe2+ redox reaction. Oxidation of Fe2+ and a decrease in oxygen vacancies is found at the surface on annealing, which is reflected in the bulk sample by a small change in unit cell volume. The significant decrease in dielectric loss property can be attributed to the decreased concentration of charged defects such as Fe2+ and oxygen vacancies through annealing process, which demonstrated that thermal annealing could be effective in improving the dielectric performance of ferromagnetic materials for various applications.
    • Hybrid Heat Pump for Micro Heat Network

      Counsell, M. J.; Khalid, Yousaf; Stewart, M.; University of Chester (World Academy of Science, Engineering and Technology (WASET), 2017-10-17)
      Achieving nearly zero carbon heating continues to be identified by UK government analysis as an important feature of any lowest cost pathway to reducing greenhouse gas emissions. Heat currently accounts for 48% of UK energy consumption and approximately one third of UK’s greenhouse gas emissions. Heat Networks are being promoted by UK investment policies as one means of supporting hybrid heat pump based solutions. To this effect the RISE (Renewable Integrated and Sustainable Electric) heating system project is investigating how an all-electric heating sourceshybrid configuration could play a key role in long-term decarbonisation of heat. For the purposes of this study, hybrid systems are defined as systems combining the technologies of an electric driven air source heat pump, electric powered thermal storage, a thermal vessel and micro-heat network as an integrated system. This hybrid strategy allows for the system to store up energy during periods of low electricity demand from the national grid, turning it into a dynamic supply of low cost heat which is utilized only when required. Currently a prototype of such a system is being tested in a modern house integrated with advanced controls and sensors. This paper presents the virtual performance analysis of the system and its design for a micro heat network with multiple dwelling units. The results show that the RISE system is controllable and can reduce carbon emissions whilst being competitive in running costs with a conventional gas boiler heating system.
    • Quality-Control of UV offset Lithographicaly Printed Electronic-Ink by THz Technology

      Zeng, Yang; Donnan, Robert; Edwards, Marc; Yang, Bin; University of Chester (IEEE Conference Publications, 2017-10-16)
      In this paper, a novel quality-monitor method of inkjet-printed electronics based on terahertz (THz) sensing is presented. Specifically, two different approaches, namely THz reflection spectroscopy and THz near-field scanning, are proposed.
    • Titanium Dioxide Engineered for Near-dispersionless High Terahertz Permittivity and Ultra-low-loss

      Chuying, Yu; Zeng, Yang; Yang, Bin; Donnan, Robert; Huang, Jinbao; Xiong, Zhaoxian; Mahajan, Amit; Shi, Baogui; Ye, Haitao; Binions, Russell; Tarakina, Nadezda V.; Reece, Mike J.; Yan, Haixue; University of London; University of Chester; Xiamen University; Aston University (Nature Publishing Group, 2017-07-26)
      Realising engineering ceramics to serve as substrate materials in high-performance terahertz(THz) that are low-cost, have low dielectric loss and near-dispersionless broadband, high permittivity, is exceedingly demanding. Such substrates are deployed in, for example, integrated circuits for synthesizing and converting nonplanar and 3D structures into planar forms. The Rutile form of titanium dioxide (TiO2) has been widely accepted as commercially economical candidate substrate that meets demands for both low-loss and high permittivities at sub-THz bands. However, the relationship between its mechanisms of dielectric response to the microstructure have never been systematically investigated in order to engineer ultra-low dielectric-loss and high value, dispersionless permittivities. Here we show TiO2 THz dielectrics with high permittivity (ca. 102.30) and ultra-low loss (ca. 0.0042). These were prepared by insight gleaned from a broad use of materials characterisation methods to successfully engineer porosities, second phase, crystallography shear-planes and oxygen vacancies during sintering. The dielectric loss achieved here is not only with negligible dispersion over 0.2 - 0.8 THz, but also has the lowest value measured for known high-permittivity dielectrics. We expect the insight afforded by this study will underpin the development of subwavelength-scale, planar integrated circuits, compact high Q-resonators and broadband, slow-light devices in the THz band.
    • Terahertz Characterisation of UV Offset Lithographically Printed Electronic-Ink

      Zeng, Yang; Edwards, Marc; Stevens, Robert; Bowen, John; Donnan, Robert S.; Yang, Bin; University of London; National University of Defense Technology; University of Chester; Nottingham Trent University; University of Reading (Elsevier, 2017-06-10)
      Inkjet-printed electronics are showing promising potential in practical applications, but methods for real-time, non-contact monitoring of printing quality are lacking. This work explores Terahertz (THz) sensing as an approach for such monitoring. It is demonstrated that alterations in the localised dielectric characteristics of inkjet-printed electronics can be qualitatively distinguished using quasi-optically-based, sub-THz reflection spectroscopy. Decreased reflection coefficients caused by the sintering process are observed and quantified. Using THz near-field scanning imaging, it is shown that sintering produces a more uniform spatial distribution of permittivity in the printed carbon patterns. Images generated using THz-TDS based imaging are presented, demonstrating the combination of high resolution imaging with quantification of complex permittivities. This work, for the first time, demonstrates the feasibility of quality control in printed electronic-ink with THz sensing, and is of practical significance to the development of in-situ and non-contact commercial-quality characterisation methods for inkjet-printed electronics.
    • Design and specification of building integrated DC electricity networks

      Stewart, M.; Counsell, M. J.; Al-Khaykan, A.; University of Chester (IEEE, 2017-01-19)
      Adoption of millions of small energy efficient, low power digital and DC appliances at home and at work is resulting in a significant and fast growing fraction of a building's electricity actually consumed in low voltage DC form. Building integrated energy systems featuring renewable photovoltaics are also increasingly attractive as part of an overall electricity and emissions reduction strategy. This paper details design and specification of a novel system level method of matching building integrated photovoltaic electricity generation with local low voltage DC appliances in office and other ICT intensive environments such as schools. The chosen scenario considers load components consisting of a diverse range of modern low power ICT and DC appliances, networked and powered by industry certified smart DC distribution technologies. Energy supply to the converged DC, IT and ICT network is described as featuring a roof-mounted or other on-site photovoltaic array in combination with conventional supply from the local grid infrastructure. The direct and strategic benefits of smart DC infrastructures are highlighted as the enabling technology for optimal demand reduction through fully integrated energy management of DC systems in buildings.
    • Assessment of Multi-Domain Energy Systems Modelling Methods

      Stewart, M.; Counsell, M. J.; Al-Khaykan, A.; University of Chester (World Academy of Science, Engineering and Technology, 2017)
      Emissions are a consequence of electricity generation. A major option for low carbon generation, local energy systems featuring Combined Heat and Power with solar PV (CHPV) has significant potential to increase energy performance, increase resilience, and offer greater control of local energy prices while complementing the UK’s emissions standards and targets. Recent advances in dynamic modelling and simulation of buildings and clusters of buildings using the IDEAS framework have successfully validated a novel multi-vector (simultaneous) control of both heat and electricity approach to integrating the wide range of primary and secondary plant typical of local energy systems designs including CHP, solar PV, gas boilers, absorption chillers and thermal energy storage, and associated electrical and hot water networks, all operating under a single unified control strategy. Results from this work indicate through simulation that integrated control of thermal storage can have a pivotal role in optimizing system performance well beyond the present expectations. Environmental impact analysis and reporting of all energy systems including CHPV LES presently employ a static annual average carbon emissions intensity for grid supplied electricity. This paper focuses on establishing and validating CHPV environmental performance against conventional emissions values and assessment benchmarks to analyze emissions performance without and with an active thermal store in a notional group of non-domestic buildings. Results of this analysis are presented and discussed in context of performance validation and quantifying the reduced environmental impact of CHPV systems with active energy storage in comparison with conventional LES designs.
    • Effect of cell-size on the energy absorption features of closed-cell aluminium foams

      Nammi, Sathish K.; Edwards, Gerard; Shirvani, Hassan; Anglia Ruskin University, University of Chester, Anglia Ruskin University, (Elsevier, 2016-07-02)
      The effect of cell-size on the compressive response and energy absorption features of closed-cell aluminium (Al) foam were investigated by finite element method. Micromechanical models were constructed with a repeating unit-cell (RUC) which was sectioned from tetrakaidecahedra structure. Using this RUC, three Al foam models with different cell-sizes (large, medium and small) and all of same density, were built. These three different cell-size pieces of foam occupy the same volume and their domains contained 8, 27 and 64 RUCs respectively. However, the smaller cell-size foam has larger surface area to volume ratio compared to other two. Mechanical behaviour was modelled under uniaxial loading. All three aggregates (3D arrays of RUCs) of different cell-sizes showed an elastic region at the initial stage, then followed by a plateau, and finally, a densification region. The smaller cell size foam exhibited a higher peak-stress and a greater densification strain comparing other two cell-sizes investigated. It was demonstrated that energy absorption capabilities of smaller cell-size foams was higher compared to the larger cell-sizes examined.
    • Electromagnetic wave absorption properties of ternary poly (vinylidene fluoride)/magnetite nanocomposites with carbon nanotubes and graphene

      Tsonos, Christos; Soin, Navneet; Tomara, Georgia N.; Yang, Bin; Psarras, Georgios C.; Kanapitsas, Athanasios; Siores, Elias; University of Chester (Royal Society of Chemistry, 2015-12-21)
      Ternary nanocomposite systems of poly(vinylidene fluoride)/magnetite/carbon nanotube (PVDF/Fe3O4/CNT) and poly(vinylidene fluoride)/magnetite/graphene (PVDF/Fe3O4/GN), were prepared using high shear twin screw compounding followed by compression moulding. The electromagnetic (EM) microwave absorption properties of the nanocomposites were investigated in the frequency range of 3–10 GHz. PVDF/Fe3O4/CNT samples with the thickness d = 0.7 mm present a minimum reflection loss (RL) of −28.8 dB at 5.6 GHz, while all the RL values in the measurement frequency range 3–10 GHz are lower than −10 dB. PVDF/Fe3O4/GN with a thickness of 0.9 mm, presents a minimum RL of −22.6 dB at 5.4 GHz, while all the RL values in the measurement frequency range 3–10 GHz are lower than −10 dB as well. The excellent microwave absorption properties of both nanocomposites, in terms of minimum RL value and broad absorption bandwidth, are mainly due to the enhanced magnetic losses. The results indicate that the ternary nanocomposites studied here, can be used as an attractive candidate for EM absorption materials in diverse fields of various technological applications, not only in the frequency range 3–10 GHz, but also at frequencies <3 GHz for PVDF/Fe3O4/CNT and >10 GHz for PVDF/Fe3O4/GN with a realistic thickness of close to 1 mm.
    • Atomic and vibrational origins of mechanical toughness in bioactive cement during setting

      Tian, Kun V.; Yang, Bin; Yue, Yuan-Zheng; Bowron, Daniel T.; Mayers, Jerry; Donnan, Robert S.; Dobo-Nagy, Csaba; Nicholson, John W.; Greer, A. Lindsay; Chass, Gregory A.; Greaves, G. Neville; Fang, De-Cai; Semmelweis University; University of Chester; Queen Mary University of London (Nature Publishing Group, 2015-11-09)
      Bioactive glass ionomer cements (GICs) have been in widespread use for ~40 years in dentistry and medicine. However, these composites fall short of the toughness needed for permanent implants. Significant impediment to improvement has been the requisite use of conventional destructive mechanical testing, which is necessarily retrospective. Here we show quantitatively, through the novel use of calorimetry, terahertz (THz) spectroscopy and neutron scattering, how GIC’s developing fracture toughness during setting is related to interfacial THz dynamics, changing atomic cohesion and fluctuating interfacial configurations. Contrary to convention, we find setting is non-monotonic, characterized by abrupt features not previously detected, including a glass–polymer coupling point, an early setting point, where decreasing toughness unexpectedly recovers, followed by stress-induced weakening of interfaces. Subsequently, toughness declines asymptotically to long-term fracture test values. We expect the insight afforded by these in situ non-destructive techniques will assist in raising understanding of the setting mechanisms and associated dynamics of cementitious materials.
    • Microwave and terahertz dielectric properties of MgTiO3–CaTiO3 ceramics

      Huang, J. B.; Yang, Bin; Yu, Chuying; Zhang, Guang; Xue, Hao; Xiong, Zhaoxian; Viola, Giuseppe; Donnan, Robert S.; Yan, Haixue; Reece, Mike J.; College of Materials; Queen Mary University of London (Elsevier, 2015-10-05)
      The THz dielectric properties of MgTiO3–CaTiO3 ceramics are reported. The ceramics were prepared via a solid-state reaction route and the sintering conditions were optimized to obtain ceramics with high permittivity and low loss in the terahertz frequency domain. The amount of impurities (MgTi2O5) and grain size increased with increasing sintering temperature. The dielectric properties improved with increasing density, and the best terahertz dielectric performance was obtained at 1260 °C, with a permittivity of 17.73 and loss of 3.07×10−3. Ceramics sintered above 1260 °C showed a sharp increase in loss, which is ascribed to an increase in the impurity content.
    • Active Power and DC Voltage Coordinative Control for Cascaded DC–AC Converter With Bidirectional Power Application

      Tian, Yanjun; Chen, Zhe; Deng, Fujin; Sun, Xiaofeng; Hu, Yanting; University of Chester (IEEE, 2015-10)
      Two stage-cascaded converters are widely used in dc–ac hybrid systems to achieve the bidirectional power transmission. The topology of dual active bridge cascaded with inverter DABCI) is commonly used in this application. This paper proposes a coordinative control method for DABCI and it is able to reduce the dc-link voltage fluctuation between the DAB and inverter, then reduce the stress on the switching devices, as well as improve the system dynamic performance. In the proposed control method, the DAB and inverter are coordinated to control the dc-link voltage and the power, and this responsibility sharing control can effectively suppress the impact of the power variation on the dc-link voltage, without sacrificing stability. The proposed control method is also effective for DABCI in unidirectional power transmission. The effectiveness of the propose control has been validated by both simulations and experiments.
    • DC-Link Voltage Coordinated-Proportional Control for Cascaded Converter with Zero Steady-State Error and Reduced System Type

      Tian, Yanjun; Loh, Poh C.; Deng, Fujin; Chen, Zhe; Hu, Yanting; 1. Department of Energy Technology, Aalborg University, Denmark; 2. Faculty of Science and Engineering, University of Chester, UK (IEEE, 2015-06-11)
      Cascaded converter is formed by connecting two sub-converters together, sharing a common intermediate DC-link voltage. Regulation of this DC-link voltage is frequently realized with a Proportional-Integral (PI) controller, whose high gain at DC helps to force a zero steady-state tracking error. Such precise tracking is however at the expense of increasing the system type, caused by the extra pole at the origin introduced by the PI controller. The overall system may hence be tougher to control. To reduce the system type while preserving precise DC-link voltage tracking, this paper proposes a coordinated control scheme for the cascaded converter, which uses only a proportional DC-link voltage regulator. The resulting converter is thus dynamically faster, and when compared with the conventional PI-controlled converter, it is less affected by impedance interaction between its two sub-converters. The proposed scheme can be used with either unidirectional or bidirectional power flow, and has been verified by simulation and experimental results presented in the paper.
    • Impedance interaction modeling and analysis for bidirectional cascaded converters

      Tian, Yanjun; Deng, Fujin; Chen, Zhe; Sun, Xiaofeng; Hu, Yanting (2015-06)
      For the cascaded converter system, the output impedance of source converter interacts with the input impedance of load converter, and the interaction may cause the system instability. In bidirectional applications, when the power flow is reversed, the impedance interaction also varies, which brings more uncertainty to the system stability. An investigation is performed here for showing that the forward and reverse interactions are prominently different in terms of dynamics and stability even though the cascaded converter control remains unchanged. An important guideline has been drawn for the control of the cascaded converter. That is when voltage mode converter working as the load converter; the constant power mode converter as the source converter, the system is more stable. The concluded findings have been verified by simulation and experimental results.
    • Research on the synchronization control strategy for microgrid-connected voltage source inverter

      Cao, Yuanzhi; Hu, Yanting; Hu, Rui; Chen, Jianfei (IEEE, 2015-06)
      Microgrid is intended and featured to be able to operate in both grid-connected and islanded mode to ensure high quality and reliable power supply. In order to achieve stable operation of the microgrid-connected voltage source inverter (MVSI) units under paralleled or grid-connected mode, a novel synchronization method based on droop control is proposed in this paper. The difference of phase and amplitude between different MVSI units is detected and is used to calculate the output frequency and amplitude of the MVSI. This method can smooth transfer the MVSI units from standalone mode to paralleled mode. The simulation and experimental results show that the proposed method is effective in achieving paralleled operation of the MVSI units.
    • Impedance coordinative control for cascaded converter in bidirectional application

      Tian, Yanjun; Deng, Fujin; Chen, Zhe; Sun, Xiaofeng; Hu, Yanting; University of Chester (IEEE, 2015-06)
      Two stage cascaded converters are widely used in bidirectional applications, but the negative impedance may cause system instability. Actually the impedance interaction is much different between forward power flow and reversed power flow, which will introduce more uncertainty to the system stability. This paper proposes a control method for the constant power controlled converter in cascaded system, and consequently it can change the negative impedance of constant power converter into resistive impedance, which will improve the cascaded system stability, as well as merge the impedance difference between forward and reversed power flow. This paper addresses the analysis with the topology of cascaded dual-active-bridge converter (DAB) with inverter, and the proposed control method can also be implemented in unidirectional applications and other general cascaded converter system. The effectiveness has been validated by both simulation and experimental results.