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Tackling global electricity shortage through human power: Technical opportunities from direct or indirect utilizations of the pervasive and green human energy
Dan DAI, Jing LIU
Frontiers in Energy. 2012, 6 (3): 210-226.
https://doi.org/10.1007/s11708-012-0200-3
With the energy and environmental problems becoming increasingly serious, human power, as a pervasive, renewable, mobile and environment friendly energy, draws more and more attention over the world. In this paper, the most basic features of human power are presented. The currently available human power harvesting theories and devices are briefly reviewed and compared. Further, direct or indirect utilization of human power in daily life, especially transportation and home appliances, such as human-powered car, watercraft, aircraft, washing machine and television etc. are summarized. Considering that the total energy from an individual is rather limited, as previously focused by most of the former works, it is conceived in this paper that an important future for large scale use of human powers lies in the efficient conversion, collection and storage of such energy from discrete people and then use it later on as desired. With the huge amount of energy gathered, the application category of human power would be significantly expended. Starting from this point, three technical ways towards efficiently utilizing human power are sketched, which are termed as human-powered grid (HPG), human-powered charger (HPC) and human-powered storage (HPS), among which, HPG is capable of collecting the electric power produced by each individual at different regions and thus can supply unique and flexible power to the customers covered in the area, without relying on the conventional electricity grid. The HPC can then charge various kinds of electrical devices instantly by a human driven generator which converts human power into electricity. Finally, the HPS can store electricity in time for later use. In this way, even for the devices requiring electricity that is strong enough, the collected human power can also serve as its reliable energy source. Meanwhile, utilization of human power becomes rather convenient and timely which guarantees its practical value. It is expected that with further research and increasing applications, human power could partially relieve the current global electricity shortage and environmental issues via its pervasive contribution.
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Sensorless direct torque control for salient-pole PMSM based on extended Kalman filter fed by AC/DC/AC converter
F. BENCHABANE, A. TITAOUINE, O. BENNIS, K. YAHIA, D. TAIBI, A. GUETTAF
Frontiers in Energy. 2012, 6 (3): 247-254.
https://doi.org/10.1007/s11708-012-0190-1
In this paper, a new sensorless interior permanent magnet synchronous motor (IPMSM) drives method with extended Kalman filter (EKF) for speed, rotor position and load torque estimation is proposed. The direct torque control (DTC) technique for permanent magnet synchronous motor (PMSM) is receiving increasing attention due to the important advantages of the low dependence on motor parameters when compared with other motor control techniques. The Kalman filter is an observer for linear and non-linear systems and is based on the stochastic intromission, in others words, noise. The PMSM is fed by an indirect power electronic converter which is controlled by a sliding mode technique. The simulation tests performed for different operating conditions have confirmed the robustness of the overall system; and it is shown that the sliding mode technique has successfully minimized the different harmonics introduced by the line converter.
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Investigation on available wind energy at Tungku beach
M. G. YAZDANI, M. A. SALAM
Frontiers in Energy. 2012, 6 (3): 275-279.
https://doi.org/10.1007/s11708-012-0194-x
In this paper, wind velocities and directions (sea and land) are recorded in different days and times. The data collected were compared with the weather data from the Brunei Darussalam Meteorological Service (BDMS) and the findings of other researchers and were found to be in good agreement. The potential of wind energy is predicted from the available data collected. The average generated power (forenoon and afternoon) is found to be 25 (mean) and 18 W (median), 101 (mean) and 73 W (median), 912 (mean) and 660 W (median), 10137 (mean) and 7331 W (median) for a rotor with a diameter of 2.5, 5, 15 and 50 m, respectively. The power density Pd for wind farming is found to be 0.26 (mean) and 0.19 (median), 0.31 (mean) and 0.22 (median) for the rotor whose diameter is 2.5 and 50 m, respectively, while the average Pd values are found to be 0.28 (mean) and 0.2 (median) for the rotor whose diameter is 5 and 15 m.
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Effect of variable heat capacities on performance of an irreversible Miller heat engine
Xingmei YE
Frontiers in Energy. 2012, 6 (3): 280-284.
https://doi.org/10.1007/s11708-012-0203-0
Based on the variable heat capacities of the working fluid, the irreversibility coming from the compression and expansion processes, and the heat leak losses through the cylinder wall, an irreversible cycle model of the Miller heat engine was established, from which expressions for the efficiency and work output of the cycle were derived. The performance characteristic curves of the Miller heat engine were generated through numerical calculation, from which the optimal regions of some main parameters such as the work output, efficiency and pressure ratio were determined. Moreover, the influence of the compression and expansion efficiencies, the variable heat capacities and the heat leak losses on the performance of the cycle was discussed in detail, and consequently, some significant results were obtained.
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Numerical simulation of bituminous coal combustion in a full-scale tiny-oil ignition burner: influence of excess air ratio
Zhengqi LI, Chunlong LIU, Xiang ZHANG, Lingyan ZENG, Zhichao CHEN
Frontiers in Energy. 2012, 6 (3): 296-303.
https://doi.org/10.1007/s11708-012-0191-0
The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 (corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively), which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the burner wall and the high-temperature region was enlarged in the radial direction along the primary air flow direction. The O2 concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.
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