| China’s solar greenhouse area is the first in the world,and is mainly distributed in the northern part of China.At present,there is a problem of high energy consumption and carbon emission in winter heating,which is not in line with the national"double carbon"strategy.It has become an issue of concern to realize the low carbon sustainable development of solar greenhouses by using renewable energy to heat the greenhouses without heating in winter and with less heating.Ground source heat pump uses renewable geothermal energy to realize cooling and heating,which has the advantages of energy saving,environmental protection and green low-carbon.Ground-source heat pumps are gradually becoming a hot spot for research in environmental control of solar greenhouses.If ground source heat pump is used in solar greenhouse,it will cause thermal imbalance of underground soil if it is mainly used for heating in winter,and long-term operation will lead to system failure.How to solve this problem will be a difficult problem for ground source heat pump research.In this paper,in order to solve the problem of soil heat imbalance in the ground source heat pump operation,we propose the research of ground source heat pump combined with the skeleton of solar greenhouse.The skeleton of the solar greenhouse is used to supply heat in winter and cold in summer to meet the requirements of solar greenhouse operation throughout the year.By adjusting the balance of heat input to the ground for free cooling and ground source heat pump cooling and heat removal from the ground for ground source heat pump heating in winter,the heat balance of the subsoil is achieved throughout the year.The research in this paper is based on the ABAQUS and TRNSYS numerical simulation softwares,which simulate the operation of a ground source heat pump system combined with a greenhouse skeleton throughout the year.Firstly,the load calculation of a 12m span solar greenhouse skeleton was used as the basis to determine the load combination,and the model was built and mechanically analyzed using ABAQUS software.The next step is to establish the numerical model of the solar greenhouse,and establish the numerical models of natural ventilation,shading and insulation quilt in TRNSYS software.Then the numerical model of ground source heat pump was established.The heating and cooling period of the system is set according to the cooling and heating load of the building.The impact of natural ventilation,shading,and insulation on the greenhouse load is simulated with the objective of the lowest operational energy consumption.The last is to add the free heating and cooling system based on the original system model by TRNSYS simulation platform,and set the start/stop time and operation mode.Simulation operation system,skeleton set heat release capacity and heat transfer coefficient,free cooling energy saving operation,soil heat storage and release capacity,and system power consumption were characterized,and finally the energy consumption of this system was compared with common soil source heat pump.The main research results of this paper are as follows:1、The results of ABAQUS mechanical analysis of the skeleton structure shows that:the load combination of the human operation on the roof during the south wind is the most unfavorable load,under the action of this load combination,the maximum stress SX=13.92MPa<allowable stress[σ]=235MPa in the greenhouse skeleton;the maximum displacement 0.08387m<0.192m(12m×1.6%=0.192 m)to meet the stiffness requirements of greenhouse engineering design.2、Research shading,natural ventilation,insulation quilt on the solar greenhouse cooling,insulation results show that:the annual cumulative heat load is 4.47×10~7k J,the cumulative cold load is 3.18×10~7k J.Compared with no added insulation cooling energy-saving measures,the annual cumulative heat load is reduced by 68.1%,the annual cumulative cold load is reduced by 85.9%,the energy-saving effect is significant.3.The heat collection and release capacity of greenhouse skeleton pipe network.The heat collection capacity during the cooling period is 4.2×10~7k J,and the heat transfer coefficient is 8.9W/(m~2·℃).The heat release capacity in the heating period is 3.59×10~7k J,and the heat transfer coefficient is 9W/(m~2·℃).When the load is small,the cooling requirement can be achieved by adopting the free cooling supply model,and the cooling supply of free cooling is 60%of the unit cooling.The soil heat storage for the whole year of system operation is 5.07×10~7k J,and the soil heat release is 5.85×10~7k J,with a difference of5.4×10~6k J,and the soil imbalance rate is 13.34%.The system consumes a total of 2.38 MW·h in the transition season and 7.56 MW·h in winter.3.42 MW·h is consumed for cooling in summer,and 13.36 MW·h is consumed for greenhouse operation throughout the year.This paper provides a certain theoretical basis for improving the combination of greenhouse skeleton pipe network and ground source heat pump,and provides a reference for future application to engineering practice. |
PDF Full Text Request