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| Estimation of energy efficiency of a destratification system for reservoirs: a case study of Jinpen Reservoir |
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Abstract In order guide the selection of effective and energy-saving destratification technologies for reservoirs, an uniform criteria of energy efficiency should be developed. The average water temperature after complete mixing can be calculated based on the conservation laws of mass and heat, the reservoir’s gravity centres before and after mixing were calculated.The total potential energy (PE) was determined by integrating the PE in each thin sub-layer over the water depth with data of water volume and density depending on the water temperature. The difference of total potential energy before and after mixing is the minimum energy input required for destratification. The minimum carbon emission from destratification was then calculated based on conversion ratio of the energy consumption to carbon emission. The energy efficiency of a destratification system was the ratio of the minimum required energy input to the actual energy input for destratification. Taking Jinpen Reservoir in Xi’an as a study case, water volumes under different water levels of the reservoir were numerically calculated using the geometry data, this new method was applied to estimate the energy input required for destratification and energy efficiency of destratification system. Minimum energy required for destratification of different months were both calculated using the geometry data. The results showed that minimum energy increase with the temperature gradient, was relatively high during the period from June to October, and reached a peak of 2432.08kW?h in July. The energy efficiency of the water-lifting aeration system was about 4%. It would be efficient at reducing the energy required for destratification and saving carbon emission by running the destratification system at the initial stratification period.
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Received: 13 January 2014
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