Electricity generation from landfill leachate was examined by using both a dual-chamber microbial fuel cell (MFC) and a single chamber MFC. Experimental results showed that the maximum power density of 2060.19 mW/m3 in the dual-chamber MFC and that of 6817.4 mW/m3 in the single chamber MFC were obtained. It was recognized that the difference in internal resistance for two MFC systems was the main reason for resulting in the difference of power generation. Power generation as function of chemical oxygen demand (COD) in single chamber MFC showed a Monod-type relationship with Pmax of 5920.96 mW/m3 and Ks of 251.39 mg/L at an external resistance of 500 Omega. Cyclic voltammetry showed that electrons were directly transferred onto the anode by bacteria in biofilms, rather than self-produced mediators of bacteria in the solutions. At low COD concentration, electricity generation was limited by the anode due to kinetic limitation; while at high COD concentration, the cathode was shown to have more significant effects on the electricity generation than the anode. COD in leachate could be removed when it increases, mainly because oxygen diffused from the cathode was substantially reduced by aerobic or anoxic bacteria in the anode chamber, leading to the substrate loss. Removal of ammonium-nitrogen was not observed in the single chamber MFC. This novel technology provides an economical route for electricity energy recovery in leachate treatment.
A large number of seawater-source heat pump systems (SWHP) have been used in residential and commercial buildings in coastal areas due to the attractive advantages of high efficiency and environmental friendliness. To overcome the disadvantages of the open loop SWHP in winter of cold regions, a closed loop SWHP system with casted heat exchanger (CHE) is presented in this paper. The CHE is consisted of pipes immersed in the seawater and used for transferring heat between the seawater and the heat exchanger pipes of the SWHP. In addition, two mathematical models that described heat transfer process of CHE in the icing and non-icing conditions in winter have been developed and validated by an experimental study. The temperature distributions along the CHE were compared between the experimental data and numerical simulation results. The relative error is less than 5%. As a result, application of SWHP systems with CHE in coastal areas in China is feasible due to the favorable geographical conditions and environment.
The method of numerical simulation was adopted in this study to explore the size of the natural ventilation inlet opening, outdoor temperature and ambient wind speed and other environmental parameters to effect of the varied rules of thermal environment of the strawberry solar greenhouse. The variation of outdoor air temperature effected greatly to the indoor thermal environment, the average air velocity in the strawberry growing zoon within the greenhouse was rose initially and dropped tend to the steady with increasing outdoor air temperature. The average temperature in the strawberry growing zoon was decreased with increasing the outside wind speed. The average air velocity was increased gradually in the strawberry growing zoon within the greenhouse with increasing outdoor wind speed. The average velocity was reduced gradually toward to constant.
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