• Energy Research
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• 7. Clean energy close
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In this paper, we propose and investigate an original approach to energy conversion based on polyzwitterionic hydrogels, which exhibit an antipolyelectrolyte effect that enables them to swell in salt water and shrink in water of a different (i.e., desalinated water) salinity. The swelling and shrinking processes run cyclically and can move a piston up or down reversibly, thus transforming the antipolyelectrolyte effect into a mechanical force based on the salinity gradient. This phenomenon makes polyzwitterionic hydrogels suitable for use in a smart, polymeric engine. We apply this approach to investigate energy recovery from a polysulfobetaine-based hydrogel. The cross-linking density, external load, particle size, and repeatability of energy recoverability of hydrogels are examined. The maximum energy recovery from 0.4 g of hydrogel in feed (calculated based on dry form) of 102 mJ/kg was obtained by a hydrogel with a 3% cross-linking density, a 200-300 μm particle size, and 100 g external load. Excellent reproducibility of engine cycles was achieved over 10 cycles. This concept is complementary to the osmotic engine concept based on a polyelectrolyte hydrogel. In addition, polyzwitterionic materials have become a benchmark material for preventing biofouling, and the swelling properties of such materials can be further modulated and tuned.

Beside their technological importance in soldering, the low melting eutectic alloys based on bismuth and indium have potential for commercial application in the field of phase- change materials (PCMs). In this respect, the knowledge of their microstructure and thermal properties such as melting temperature, latent heat of melting, supercooling tendency, thermal conductivity, etc. is of large importance. In this study, two ternary eutectic Bi-In-Sn alloys were investigated by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) and differential scanning calorimetry (DSC). Microstructure of the prepared eutectic alloys was analyzed using SEM- EDS and identification of co-existing phases was done. Melting temperatures and latent heats of eutectic melting were measured using DSC technique. Experimentally obtained results were compared with the results of thermodynamic calculation according to CALPHAD (calculation of phase diagram) approach and good mutual agreement was obtained.

Abstract Using an econometric energy demand model, this paper separates price from non-price conservation effects in the period 1974–1977 and examines what might have happened to Canadian energy demands if Canada had priced its energy at OPEC equivalent levels instead of pursuing a gradual ‘phase-in’ policy. Prices accounted for the major proportion of energy savings over the period 1974–1977, particularly in the industrial and transport sectors, and for oil and gas. Non-price effects seem to have had a larger impact in the earlier years and for oil and electricity. Movement to international prices during the period studied could have reduced Canadian secondary energy demands by the oil equivalent output of 1.3 Syncrude-sized (125 000 bbl/day) oilsands plants.

Technical solutions for optimizing the flame aerodynamics and the design of tangentially arranged burners in a TGMP-314 boiler are proposed. The implementation of these solutions will make it possible to achieve more reliable operation of the boiler during fuel oil combustion, smaller amount of NOx emissions during the combustion of gas and fuel oil, and a somewhat lower air excess factor in the furnace.

With the integration of a high penetration of wind power into distribution system, the ability to cope with the voltage fluctuation issue arising from the intensified uncertainty should be improved. Energy storage system (ESS) with effective control strategies keeps a key role in smoothing the voltage fluctuation caused by the uncertainty of wind turbine generators (WTGs). Considering the constraints of state of charge (SOC), charge-discharge efficiency and continuous operation of ESS, this paper proposes a novel approach to determine the minimum capacity of ESS to satisfy the voltage fluctuation limit based on unbalanced three-phase interval power flow. An unbalanced forward-backward sweep interval power flow considering the constraints of ESS and the voltage fluctuation limit is proposed. The interval model of uncertain WTG output is established on basis of wind speed fluctuation curve. The interval model of the practical ESS output is obtained on basis of the present SOC, nominal capacity and comprehensive efficiency. The output voltages of power flow can directly demonstrate the voltage fluctuation rate due to their interval forms. Therefore, a feedback mechanism is established between the output voltage fluctuation rate and the input ESS practical power, which is used to determine the minimum capacity of ESS to satisfy the fluctuation limit. A modified IEEE 33-bus system with high penetration of WTGs is implemented to test the proposed method. Results demonstrate the validity and effectiveness of the proposed approach.

Abstract A CFD modelling study has been undertaken to examine the co-firing of pulverised coal and biomass with particular regard to the burnout of the larger diameter biomass particles. Computations were based on a research combustion facility that replicates an industrial coal-fired power station. Three percent, by mass, of pinewood was blended with a bituminous UK coal, and the effects of the wood particle size and shape on the burnout of the combined wood and coal char were investigated. The effect of varying the devolatilisation and char combustion rate constants for the biomass component in the blend was also investigated. It was concluded that the combustion of small (200 μm) wood particles was rapid but the rate of combustion of larger particles was dependent on their composition, size, and shape.

In order to improve the accuracy of the battery state of charge (SOC) estimation, in this paper we take a lithium-ion battery as an example to study the adaptive Kalman filter based SOC estimation algorithm. Firstly, the second-order battery system model is introduced. Meanwhile, the temperature and charge rate are introduced into the model. Then, the temperature and the charge rate are adopted to estimate the battery SOC, with the help of the parameters of an adaptive Kalman filter based estimation algorithm model. Afterwards, it is verified by the numerical simulation that in the ideal case, the accuracy of SOC estimation can be enhanced by adding two elements, namely, the temperature and charge rate. Finally, the actual road conditions are simulated with ADVISOR, and the simulation results show that the proposed method improves the accuracy of battery SOC estimation under actual road conditions. Thus, its application scope in engineering is greatly expanded.

The Severn Estuary has the world's second largest tide range and a barrage across the estuary, located just seawards of Cardiff in Wales and Weston in the South West England, has been proposed for over half a century, with the objective of extracting large amounts of tidal energy. A Severn Barrage, as previously proposed by the Severn Tidal Power Group (STPG), would be the largest renewable energy project for tidal power generation in the world, if built as proposed, and would generate approximately 5% of the UK's electricity needs. However, concerns have been raised over the environmental impacts of such a barrage, including potential increase in flood risk, loss of intertidal habitats etc. In addressing the challenges of maximizing the energy output and minimizing the environmental impacts of such a barrage, this research study has focused on using a Continental Shelf model, based on the modified Environmental Fluid Dynamics Code (EFDC) with a barrage operation module (EFDC_B), to investigate both the far and near field hydrodynamic impacts of a barrage for different operating scenarios. Three scenarios have been considered to simulate the Severn Barrage, operating via two-way generation and using different combinations of turbines and sluices. The first scenario consisted of 216 turbines and 166 sluices installed along the barrage; the second consisted of 382 turbines with no sluices; and the third consisted of 764 turbines and no sluices. The specification of the sluice gates and turbines are the same for all scenarios. The model results indicate that the third scenario has the best mitigating effects for the far-field and near-field flood risks caused by a barrage and produces the most similar results of minimum water depth and maximum velocity distributions to those obtained from simulating the natural conditions of the estuary, i.e. the current conditions. The results also show that the flow patterns around the barrage are closest to those for the existing natural conditions with minimal slight changes in the estuary. Thus, the results clearly indicate that the environmental impacts of a Severn Barrage can be minimized if the barrage is operated for two-way generation and under the third scenario. Although it appears that the energy output for the third scenario is less than that obtained for the other two scenarios, if very low head (VLH) turbines are used, then the third scenario could generate more energy as more turbines could be cited along the barrage structure. Therefore, the study shows that a Severn Barrage, operating in two-way generation and with 764 turbines (ideally VLH turbines), would be the best option to meet the needs of maximizing the energy output, but having a minimal impact on environmental changes in the estuary and far-field.