| Solar greenhouse because of its simple phase structure,but has a strong ability to absorb solar energy has been used in large-scale agricultural production.However,due to the material,technology and other restrictions,the use of cold areas encountered difficulties.In this paper,the characteristics of solar greenhouse in daqing area were analyzed and the low temperature at night would result in crop loss.In order to ensure that crops can grow in winter,the environmental temperature of solar greenhouse and the surface soil temperature should be guaranteed first.With the energy stress and environmental pollution becoming more and more serious,GSHP stands out because of its energy saving and efficiency.GSHP has been proved to be efficient in the current research results.On this basis,the idea of GSHP heating system for solar greenhouse heating is proposed.Sunlight greenhouse physical model is established,through the study of the heat transfer analysis of greenhouse,calculate the greenhouse the largest heat load during the heating season,according to the geographical location and climate characteristics of the daqing area,comprehensive consider saving land and cost,the Gree SSD_H2800 for five(5)the same type of greenhouse heating system,and the total length of buried pipe and number of buried pipes are calculated,finally calculate the total linear meter length is 5840 m,the buried pipes drilling number is 60.Because solar greenhouse only takes heat in winter,long-term operation will lead to soil heat loss year by year,causing soil temperature to drop year by year,and then system failure and ecological damage.In order to ensure the soil heat balance and improve the heat collection efficiency,it is proposed to use the solar heat collection system to replenish the soil heat in the non-heating season,which requires 193 pieces of the solar plate collector of about 2 ㎡.Through the establishment of physical model and a heat transfer model on the basis of the sunlight greenhouse,according to the indoor air flow and heat transfer of the sunlight greenhouse to choose the corresponding mathematical model,and then determine the sunlight greenhouse in the continuity equation,momentum equation and energy equation,and the discretization equations listed,will not easily to solve differential equations into relatively simple algebraic equations.Then,based on the three-dimensional model of solar greenhouse,ansys software ICEM is used to divide the grid.Through the determination of the boundary conditions of each enclosure structure,the mathematical model established before was used,and the simulation software FLUENT was used to simulate the temperature field inside the solar greenhouse.It was verified that after installing the ground-source heat pump heating system,the temperature of the greenhouse at nightreached 15-25℃,which could meet the temperature demand of the crops growing at the greenhouse at night.Economic comparative analysis can be made from three aspects: initial investment,operating cost and annual cost.Taking the solar greenhouse of 3600 square meters in daqing area as an example,the cost and benefits of the ground source heat pump system are estimated.Further economic evaluation of the system by using the net present value and the investment payback period: for solar greenhouses in the northern cold areas of China,the net present value of the ground source heat pump system is greater than zero within the operation life(20 years),which has the ability to resist risks and is suitable for investment and operation.With the benchmark discount rate of 10%,the payback period of the GSHP heating system is 19.5 years. |
