| As a big energy province,heilongjiang province has passed the peak mining period,reduced energy resources,difficult mining,and increased output costs.There is an urgent need to conserve energy and transform the way it is used.Geothermal energy is a new type of renewable energy with large reserves,wide distribution,green and low carbon,recyclable and highly competitive.The application of ground source heat pump technology is very effective in reducing haze.But heilongjiang province is located in the cold zone,the user side of the cold,heat load demand is very unbalanced.It can easily cause the problem of cold soil accumulation.This paper is based on a heating demonstration project in heilongjiang province.Before the experiment,the in-situ thermal response test was carried out to find out the formation lithology,drillability,initial temperature of rock and soil,thermophysical parameters of the experiment site,and the appropriate temperature range of inlet was selected and the corresponding heat was taken.In order to alleviate the problem of cold accumulation of soil,the buried tube heat exchanger has a depth of up to 600m.It adopts galvanized seamless steel tube material and titanium nano-polymer layer anticorrosion treatment.The experiment data of the whole heating period were analyzed to understand the law of soil temperature change during heating period and recovery period.After a year of heating operation,the soil temperature decreased by 0.23 from the initial temperature of 19.35 to 19.12.The cold accumulation problem still exists.If the heat is taken in the second year,the soil temperature will drop year by year,destroying the soil thermal balance.Based on the experiment,TRNSYS simulation software is used to establish the simulation platform of ground source heat pump system with buried pipes.The simulation accuracy was verified by comparing with the experimental data of heating period.When the system simulates the annual hourly cooling and heat load,it is found that the cooling load demand is very small in 37 out of 67 days of the cooling period,and the direct cooling can meet the requirements.And put forward two kinds of operation scheme,one is heat pump heating and cooling operation scheme,the second is heat pump heating and direct cooling operation scheme.The 10-year operation simulation was conducted respectively,and the comparative analysis showed that the EER of the first operation plan during the cold supply period was 4.75.However,the second operation plan adopts the direct cooling operation mode within 37 days when the cooling load demand is low,which is 23.80.The average soil temperature of the two operating schemes was simulated.The results show that the temperature of recirculating water supplied by direct cooling is relatively high,which is more effective to alleviate the cold accumulation of soil.Finally,TRNSYS simulation software is used to simulate the long-term running effects of the two operating modes.The results showed that the COP of winter heating decreased year by year,and the decreasing range decreased gradually.Summer cooling EER is rising trend;After 10 years of operation,the average soil temperature of the two operation modes has been reduced by 1.5 and 1.25 respectively,while the EER of direct cooling has reached 24.26,which is five times of that of conventional cooling.The direct cooling method has more advantages in relieving the cold accumulation of soil and more energy saving in the operation process.Compared with traditional central heating,the energy saving rate of GSHP in winter is 39%.Compared with traditional central air-conditioning,the energy saving rate of GSHP in summer is 72%and 84%respectively.Compared with the conventional cooling system,the CO2 and SO2 emissions of the direct cooling system decreased by 963.08kg and 9.06kg respectively.The payback period of GSHP for heating,conventional cooling and direct cooling systems is 9.95 years and 9.53 years respectively.From the aspects of energy saving,environmental protection and economy,it is proved that direct cooling is a feasible and energy-saving operation mode in the cold region,and provides some Suggestions for practical projects. |
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