Research On Using The Subsurface Layer Of Seawater As A Regional Air Conditioning Cooling Source For Cities

A large amount of thermal energy can be used by developing the thermo cline layer of sea. To establish an economical, energy saving and environmental friendly regional air conditioning system research on using the subsurface layer of seawater as cooling source for cities was done in this thesis. It would help releasing the power shortage caused by air conditioning in summer and improving the ecological environment.A new heat exchange scheme with working units in certain depth of sea was put forward to make chilled water. Theoretic analysis and numerical computations showed its advantages and energy saving superiorities compared to the traditional on shore ones.In order to reduce the cost of maintaining the enormous artificial pipe systems, which would get rust and damaged after years'running, the idea of using underground aquifer as a brand new transferring medium was put forward. Aquifers were always used for thermal energy storage but it would play a different role in this whole new scheme. Mechanism of using the appropriate hydro-geological structure with a good water permeability and water bearing ability for chilled water's transportation was preliminarily demonstrated.Reasonable simplifications and assumptions were made to simulate the process of water's seepage flow and coolant transportation in underground aquifer. Ground subsidence can be avoided by over recharging. Leading wells were designed to guide the running water and dredging the aquifer and the range of water flow can be confined by interfering wells. A forefront assumption was made to describe the movements of chilled water and different time steps were used to verificate its location during the simulation, which confirmed the veracity and lessen the computation time relatively.A heat transfer model was set up and solved in a dispersed method. Analysis based on streamlines showed that the loss of coolant in aquifer would be reduced with time and chilled water can reach the required temperature after a certain period of time. The influence of thermal characteristics of rocks to the whole process was also discussed.At the end of this thesis three kinds of cooling systems, which are heat pump systems with coolant transportation by aquifer and pipes as well as electrical refrigeration respectively were compared in energy utilization efficiency. The results showed that former two systems can save energy and less power would be consumed with time by using underground aquifer as a transferring medium though it had a larger budget at the very beginning.The conception of making chilled water by exchanging heat in the sea and using the underground aquifer as a transferring medium was validated in this thesis. The thesis proved the potential in saving energy and protecting ecological environment of this new idea. This kind of district cooling system can be applied in a salty sea area and improve the efficiency of using the thermal energy contained in the subsurface layer of seawater. In addition, power consumed by air conditioning in summer in cities can be reduced with time. Thus using the subsurface layer of seawater as a regional AC cooling source and taking the underground aquifer as a transportation path could be a sustainable regional cooling system.