Study On Long Distance Transportation Energy Supply System And Its Application Based On Solution Storage

Energy is an essential material basis of human beings.With the improvement of production technology and living standards,the world's demand for energy is also increasing.On the one hand,the volatility and instability of some distributed energy sources make it urgent to study large-scale,low-cost and high-reliability energy storage methods suitable for these energy sources;on the other hand,these distributed energy sources are separated from energy users,and at present,the sensible/latent heat of water(hot water,cold water,ice storage,etc),which mainly utilized to transport heat/cold energy over distances,the corresponding heat loss is very large.And the heat/cold transport radius is relatively short(?10km)in this way.Aiming at solving some key problems in the energy system research of various low-grade energy sources,this paper focuses on the long-distance transportation energy system based on solution energy storage and its further application in wind-heat conversion and utilization system,enhanced geothermal system and cogeneration system.Firstly,this paper proposed a new type of long-distance hot/cold supply system based on solution energy storage,analyzed its basic principle,established a thermodynamic analysis model,and further verified the built model.This paper first introduced a novel solution energy storage system.The typical working mediums suitable for this system were NH3-H2O and LiBr-H2O.For the low-grade heat source energy utilization system that needs large-scale energy storage,NH3-H2O was chosen as the working medium pair in this paper.Then,based on the Schulz ammonia-water mixture state equation,a calculation program with a high applicability and accuracy of the thermodynamic properties of ammonia aqueous solution at different regions was constructed and verified.Based on the mathematical model,the ammonia water absorption solution energy storage system model and the long-distance heating/cooling supply model were established respectively,and the accuracy was also verified.The current work made a base for the following research work on several distributed energy system and its application based on solution energy storage and long-distance transportation for heating/cooling.Aiming at the solving grid-connection problems caused by the randomness and intermittence of wind energy,and the wind curtailment phenomenon of "Abandoned Wind Power Rationing",based on the built system above,this paper proposed a wind heating conversion and long distance transmission system,and conducted a thermodynamic analysis of the system on the basis of the wind heating conversion experiment.The experimental demonstrated that the heating efficiency of 90.3%can be achieved by hydraulic oil-pressure damping heating.The theoretical analysis of the wind heating conversion system showed that when the wind energy power density increased from 250 W m 2 to 350 W m-2,the wind energy utilization efficiency of the system increases gradually.When it increased from 350 W·m-2 to 650 W·m-2,the efficiency was basically unchanged.When it exceeded 650 W·m-2,the efficiency of the system decreased gradually.With the increase of the ambient temperature and the decrease of the heating temperature,the circulation ratio of the concentrated solution F decreased continuously.The lower the circulation ratio of the concentrated solution,the smaller the pipe diameter of the transportation pipeline and the lower pump power consumed by the transportation pump would be.Compared with the conventional hot water delivery system,the wind heating conversion and long distance transmission system can significantly reduce the mass flow rate and pipe diameter of the transportation pipeline,as well as the transportation energy consumption and capital cost of the system.At the same time,the maximum heating distance was greater than 10 times of the conventional high temperature hot water delivery system.The difficulties in geothermal exploration and exploitation caused the high capital investment,and the insufficiency utilization rate of geothermal itself,which resulted in insufficient investment costs.An ammonia-water absorption long-distance cooling/heating system for enhanced geothermal resources was proposed And influences of geothermal well injection parameters and formation structure parameters on the energy transmission system was emphatically analyzed.The results showed that when the heating capacity of the enhanced geothermal system was 20MW,the heating distance of the ammonia-water absorption long-distance energy supply system based on EGS was 2.5-3 times that of the conventional high temperature hot wat er transportation system,and the average pipe diameter decreased by 78.5%.The ammonia water absorption long-distance energy supply system based on EGS can obtain the maximum cooling capacity/heat production at the thermal reservoir length of 150 m,but in this case,the maximum cooling/heat supply distance was the shortest Cooling capacity/heat production of ammonia water absorption long-distance energy supply system based on EGS was positively correlated with injection mass flow rate,well depth and reservoir fracture porosity.The maximum cooling/heating distance was positively correlated with well depth,reservoir fracture porosity,cooling temperature,and outlet temperature of water for the recovery well,and negatively correlated with injection mass flow.In addition,the pipe diameter has a significant impact on the maximum cooling/heating distance.In order to further explore the long-distance transportation and energy supply system suitable for distributed energy sources with different forms and structures,this paper combined the improved Kalina cycle,absorption refrigeration,solution energy storage and long-distance transport system,and proposed a new type of Combined Heat and Power(CCHP)system which integrates power generation,energy storage,cold storage,heat storage,and long-distance heating/cooling.The system can also flexibly change the energy storage and release process according to various heat sources and conditions,so as to achieve the purpose of peak shifting and valley filling.The results showed that thermal efficiency and exergy efficiency were positively correlated with inlet concentration and inlet temperature of the turbine.For a certain turbine inlet concentration,the base solution concentration was negatively correlated with thermal efficiency,exergy efficiency,net output power,and refrigeration output capacity.With the increase of cycle refrigeration to power ratio ?,the net output power remained unchanged,while the refrigeration output capacity,thermal efficiency,exergy efficiency increased linearly.However,the pinch temperature difference of the generator limited the further improvement of refrigeration to power ratio ? Therefore,for the proposed cogeneration system,there existed an optimal refrigeration to power ratio ?,which could achieved the best thermal performance by matching different types of heat sources.For the basic working conditions of the base-case cycle,the distribution of the exergy loss of each component showed that the generator accounted for 39.06%of the total exergy destruction,followed by ABS2,BOL,PRC,and HEX1,and their exergy loss ratios accounted for 16.31%,15.85%,9.84%and 4.94%respectively.Further utilization of exhaust steam and waste heat,as well as the use of optimized design and high-efficient heat exchangers can improve the exergy destruction loss of the corresponding components.The turbine inlet concentration and the generator heat source inlet temperature were positively correlated with the system solution storage energy density,while the ambient temperature and the refrigeration temperature were negatively correlated with solution storage density.When the turbine inlet concentration was 0.7 kg·kg-1,and the generator heat source inlet temperature was 180?,the maximum solution storage density reached 523 MJ·m-3.