Undoped and vanadium‐doped ZnO thin films were prepared on single‐crystalline p‐type Si(100) substrates by a sol–gel process and further annealed in an oxygen atmosphere. The influence of vanadium doping on the structural, surface morphological and optical properties of ZnO thin films was investigated by X‐ray diffraction, atomic force microscopy and photoluminescence measurements. Both the undoped and V‐doped ZnO thin films were of polycrystalline hexagonal wurtzite structure with (002)‐preferred orientation. The crystallite size and the root‐mean‐square roughness of V‐doped ZnO are smaller than those of undoped ZnO. Vanadium doping could reduce deep level defects of ZnO and thus strengthen ultraviolet (UV) emission. The peak intensity of UV emission increased with increasing annealing temperature above 400 °C. After annealing at 800 °C, the UV emission for the V‐doped ZnO films was largely enhanced, while the visible emission was distinctly weakened. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Poor economic performance has limited the diffusion of the combined cooling, heating, and power (CCHP) system. Various factors influence the economic performance of the CCHP system. To analyze the impacts of these different factors and promote the CCHP system, this study evaluated its comprehensive performance through a multi-criteria method, using an amusement park resort in Shanghai as a research case. First, three CCHP systems with different penetration rates were presented and simulated in a transient simulation model for comparison. The economic and environmental performance of these different penetration CCHP systems were evaluated based on the dynamic payback period and carbon dioxide emissions. The impacts of investment cost, energy prices, investment subsidy and a carbon tax on the economic performance of the three systems were discussed, and a sensitivity analysis was used to compare these factors. The results show that the current subsidy can reduce the economic gap between the CCHP system and the conventional system, but it still needs to be increased by 1.71 times to achieve market competitiveness of the CCHP system with 100% penetration under the current investment cost and energy prices. In addition, the introduction of a carbon tax could accelerate the promotion of the CCHP system. When the carbon tax reaches 25 $/ton, the CCHP system becomes the best choice of energy supply system.
Emergency power system refers to a system that is composed of self-generating equipment in the building. By providing power support for emergency events such as power outages, it can keep the energy safety assurance. Usually, emergency power systems are independent and redundant. As a backup, their utilization rates are extremely low, resulting in excessive redundancy causing a lot of waste of resources and equipment. In this paper, a model integrating stand-alone emergency power systems with micro-network was proposed to improve power supply reliability in a more economic manner. Integrated emergency power system with the dispatch strategy of self-priority was established based on reliability and power demand of buildings simulated through Monte Carlo method. To evaluate the impact of integration, the total cost of integrated emergency power system was calculated including economic loss during power outages and system costs. Finally, genetic algorithm was used to obtain the optimal capacity and dispatch strategy of the integrated emergency power system by minimizing the total cost. Results showed that the reliability was improved, and the total cost was reduced to 80.05% by integrated emergency power system in the illustrated case.
In recent years, the peak–valley differences in urban power loads have been increasing. It is difficult to maintain the real-time balance of a power system by relying solely on the generation-side resources. As a typical flexible load, an air conditioning load can balance the supply and demand of a power grid by adjusting power using the thermal inertia of buildings. From the perspective of a load aggregator, this study models and aggregates the dispatch of a single inverter air conditioner distributed in a region to determine the adjustment potential of an air conditioning cluster. Then, according to the demand response capacity requirements, an optimal strategy for the aggregate dispatch of an inverter air conditioner considering incentive compensation measures is proposed with the objective of maximizing the load quotient economic benefit. The sensitivity analysis of the compensation factor for temperature rise is also performed. The results show that 3000 inverter air conditioners in the load quotient dispatch area participate in the demand response for 4 h, with a load reduction of 1.267 MW and a net income of RMB 14,435.97. Secondly, an increase in the temperature rise compensation factor will reduce the cost of temperature rise compensation by the loader to the user, but it will also reduce the load reduction and the net income of the loader. This study has practical significance for load aggregators to formulate compensation strategies and improve the economic benefits of participating in demand response.
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