| 1. |
- Duan, Zhiyin, et al.
(author)
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Indirect evaporative cooling : Past, present and future potentials
- 2012
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In: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 16:9, s. 6823-6850
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Journal article (peer-reviewed)abstract
- This paper reported a review based study into the Indirect Evaporative Cooling (IEC) technology, which was undertaken from a variety of aspects including background, history, current status, concept, standardisation, system configuration, operational mode, research and industrialisation, market prospect and barriers, as well as the future focuses on R&D and commercialisation. This review work indicated that the IEC technology has potential to be an alternative to conventional mechanical vapour compression refrigeration systems to take up the air conditioning duty for buildings. Owing to the continuous progress in technology innovation, particularly the M-cycle development and associated heat and mass transfer and material optimisation, the IEC systems have obtained significantly enhanced cooling performance over those the decade ago, with the wet-bulb effectiveness of greater than 90% and energy efficiency ratio (EER) up to 80. Structure of the IEC heat and mass exchanger varied from flat-plate-stack, tube, heat pipe and potentially wave-form. Materials used for making the exchanger elements (plate/tube) included fibre sheet with the single side water proofing, aluminium plate/tube with single side wicked setting (grooved, meshed, toughed etc), and ceramic plate/tube with single side water proofing. Counter-current water flow relevant to the primary air is considered the favourite choice; good distribution of the water stream across the wet surface of the exchanger plate (tube) and adequate (matching up the evaporation) control of the water flow rate are critical to achieving the expected system performance. It was noticed that the IEC devices were always in combined operation with other cooling measures and the commonly available IEC related operational modes are (1) IEC/DEC system; (2) IEC/DEC/mechanical vapour compression system; (3) IEC/desiccant system; (4) IEC/chilled water system; and (5) IEC/heat pipe system. The future potential operational modes may also cover the IEC-inclusive fan coil units, air handle units, cooling towers, solar driven desiccant cycle, and Rankine cycle based power generation system etc. Future works on the IEC technology may focus on (1) heat exchanger structure and material; (2) water flowing, distribution and treatment; (3) incorporation of the IEC components into conventional air conditioning products to enable combined operation between the IEC and other cooling devices; (4) economic, environment and social impacts; (5) standardisation and legislation; (6) public awareness and other dissemination measures; and (7) manufacturing and commercialisation. All above addressed efforts may help increase the market ratio of the IEC to around 20% in the next 20 years, which will lead to significant saving of fossil fuel consumption and cut of carbon emission related to buildings.
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| 2. |
- He, Wen, et al.
(author)
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Metal Ti quantum chain-inlaid 2D NaSn2(PO4)3/H-doped hard carbon hybrid electrodes with ultrahigh energy storage density
- 2021
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In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 403
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Journal article (peer-reviewed)abstract
- We report the development of a new hybrid electrode that allows for a reinforcing combination of different energy storage mechanisms, providing enhanced energy and power densities. This hybrid electrode is composed of chain-like metal titanium (zero valency state) quantum dots (< 10 nm), two-dimension NaSn2(PO4)(3) layer and H-doped hard carbon layer, and possesses unique sandwich and hierarchically meso-macroporous structures. These chain-like quantum dots are inlaid on the edge of ultra-thin NaSn2(PO4)(3) nanosheets by using a convenient and economic method, enhancing its conductivity. This design takes advantage of the unique properties of each component and nanostructure, resulting in synergistic effects to improve the charge transfer and energy storage. The hybrid electrode not only shows high capacity, outstanding rate performance and long cycling stability, but also matches well with porous Na3V2(PO4)(3) cathode. Remarkably, the Na/Li mixed-ion full battery exhibits significant improvements on the energy and power densities (555 Wh Kg(-1)/804 W Kg(-1) at 1C). Detailed charge storage mechanism investigation reveals that the prelithiation reduces the pseudocapacitive of hybrid electrode and increases its battery behavior, resulting in an ultrahigh energy storage density. Our findings demonstrate that this hybrid electrode is a new potential candidate for high-performance mixed-ion batteries.
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| 3. |
- He, Wei, et al.
(author)
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Operational performance of a novel heat pump assisted solar facade loop-heat-pipe water heating system
- 2015
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 146, s. 371-382
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Journal article (peer-reviewed)abstract
- This paper aims to present an investigation into the operational performance of a novel heat pump assisted solar façade loop-heat-pipe (LHP) water heating system using both theoretical and experimental methods. This involved (1) development of a computer numerical model; (2) simulation of the operational performance of the system by using the model; (3) test rig construction; and (4) dedicated experiment for verification of the model. It was found that the established model is able to predict the operational performance of the system at a reasonable accuracy. Analyses of the research results indicated that under the selected testing conditions, the average thermal efficiency of the LHP module was around 71%, much higher than that of the loop heat pipe without heat pump assistance. The thermal efficiency of the LHP module grew when the heat pump was turned-on and fell when the heat pump was turned-off. The water temperature remained a steadily growing trend throughout the heat pump turned-on period. Neglecting the heat loss of the water tank, the highest coefficient of the performance could reach up to 6.14 and its average value was around 4.93. In overall, the system is a new façade integrated, highly efficient and aesthetically appealing solar water heating configuration; wide deployment of the system will help reduce fossil fuel consumption in the building sector and carbon emission to the environment.
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| 4. |
- He, Wei, et al.
(author)
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Recent development and application of thermoelectric generator and cooler
- 2015
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In: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 143, s. 1-25
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Journal article (peer-reviewed)abstract
- Energy crisis and environment deterioration are two major problems for 21st century. Thermoelectric device is a promising solution for those two problems. This review begins with the basic concepts of the thermoelectric and discusses its recent material researches about the figure of merit. It also reports the recent applications of the thermoelectric generator, including the structure optimization which significantly affects the thermoelectric generator, the low temperature recovery, the heat resource and its application area. Then it reports the recent application of the thermoelectric cooler including the thermoelectric model and its application area. It ends with the discussion of the further research direction.
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| 5. |
- He, Wei, et al.
(author)
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Theoretical investigation of the thermal performance of a novel solar loop-heat-pipe facade-based heat pump water heating system
- 2014
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In: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 77, s. 180-191
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Journal article (peer-reviewed)abstract
- The aim of the paper was to present a dedicated theoretical investigation into the thermal performance of a novel solar loop-heat-pipe façade based heat pump water heating system. This involved thermo-fluid analyses, computer numerical model development, the model running up, modelling result analyses and conclusion. An energy balance network was established on each part and the whole range of the system to address the associated energy conversion and transfer processes. On basis of this, a computer numerical model was developed and run up to predict the thermal performance of such a system at different system configurations, layouts and operational conditions. It was suggested that the loop heat pipes could be filled with either water, R134a, R22 or R600a; of which R600a is the favourite working fluid owing to its relatively larger heat transfer capacity and positive pressure in operation. Variations in the system configuration, i.e., glazing covers, heat exchangers, would lead to identifiable differences in the thermal performance of the system, represented by the thermal efficiency and COP. Furthermore, impact of the external operational parameters, i.e., solar radiation and ambient air temperature, to the system's thermal performance was also investigated. The research was based on an innovative loop-heat-pipe façade and came up with useful results reflecting the thermal performance of the combined system between the façade and heat pump. This would help promote development and market penetration of such an innovative solar heating technology, and thus contribute to achieving the global targets in energy saving and carbon emission reduction.
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| 6. |
- Liu, Xuezhi, et al.
(author)
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Damping control for power system based on state observer
- 2014
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In: SOP Transactions on Power Transmission and Smart Grid. - 2380-0003 .- 2380-0011. ; 1:1, s. 9-19
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Journal article (peer-reviewed)abstract
- In this work, design of damping controller for Power System based on state observer is studied. The linearized state equation model of multi-machine power system is built, which includes four-order generator model and three-order excitation model. The power system damping characteristic is improved using feedback control based on the states that are estimated by full-order and reduced-order observer. The simulation results using a four-machine two-area system is utilized to validate the effectiveness of the proposed method.
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| 7. |
- Liu, Xuezhi, et al.
(author)
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Transmission network expansion planning by improved simulated annealing approach
- 2014
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In: SOP Transactions on Power Transmission and Smart Grid. - 2380-0003 .- 2380-0011. ; 1:1, s. 1-8
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Journal article (peer-reviewed)abstract
- The transmission network expansion planning problem is effectively solved by the improved simulated annealing approach. A mixed integer nonlinear programming model of this problem is formulated using the DC power flow model. The detailed process of simulated annealing algorithm has been improved, and applied to 6-bus and 24-bus systems. The solutions obtained by the improved SA approach are compared with solutions found using LINGO software. Numerical results have shown that the proposed approach requires less time to obtain local optimal solutions.
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| 8. |
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| 9. |
- Lu, Lu, et al.
(author)
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Theoretical analysis of natural-gas leakage in urban medium-pressure pipelines
- 2014
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In: Journal of Environment and Human. - 2373-8324 .- 2373-8332. ; 1:2, s. 71-86
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Journal article (peer-reviewed)abstract
- With widespread deployment of the urban natural gas industry, the energy security is now becoming one of the priorities in practice. Gas leakage may occur from the pipeline during the collection and transportation process. This article therefore presented a theoretical study on the urban natural gas pipeline leakage in order to provide the basic theory of the rescue policy making in emergent occasions. The investigation was undertaken through the fundamental analysis based on derivation of gas leakage models. The gas leakage model was applied to analyze the pressure, temperature and flow rate of gas leakage over time under both the steady-state and dynamic conditions. Two main impacting factors, pressure and hole size, were subsequently discussed. It is concluded that for the steady leakage the flow rate increases with the increase of pipeline pressure and hole size. And the distribution of pressure, temperature, density and velocity were calculated along the pipeline. For the unsteady leakage, the time of leakage is very short under different initial pressure and hole size, and the total leakage and average leakage rates were analyzed.
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| 10. |
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