| Strawberry is one of the fruits with high nutritional and economic value.Greenhouse cultivation can effectively promote the growth of strawberry and improve the quality of strawberry fruit.The change of temperature and light has obvious effect on the growth and quality of strawberry.Greenhouse planting can effectively provide suitable temperature and light environment for strawberry growth,but it needs to provide energy for greenhouse planting.The combination of solar energy and greenhouse will become a research trend.Based on the growth of strawberry,combined with solar thermal photovoltaic mode to provide energy for greenhouse,and under this coupling mode,the effect of temperature and light on the growth of strawberry,the quality and yield of fruit in greenhouse were studied.The Artificial Neural Network?ANN?is used to establish a nonlinear model to predict the growth index of strawberry,to achieve the effective matching of solar energy supply and temperature and light environment,and to predict the growth status of strawberry.The main research work includes the following aspects.?1?Two greenhouses covered with polyethylene film with the same area were designed and built.The solar combined heat pump system was used to heat the greenhouse,and two modes of stepped heating and parallel stereoscopic heating were established.The strawberries of‘Jingzangxiang'were planted in the greenhouse.The results showed that the coefficient of performance?COP?value of solar combined heat pump system for greenhouse heating in winter was between 3.0 and 5.2,which had better heating performance,in the mountainous monsoon climate area of the low latitude plateau in the north subtropical zone.The optimal heating height range for step heating was between 1.0-1.5 m above the ground.Within this height range,a space heating temperature with an average temperature of 15.5°C could be obtained.The parallel stereoscopic heating had better spatial uniformity,and the average daily temperature difference in the horizontal direction of the greenhouse during heating throughout the day was only 2.8°C.The change of heating temperature made strawberries yield higher and quality better than other height strawberries placed on the 1.0 m step.In the continuous rainy and low temperature weather,the average daily electric energy consumed by the heat pump for greenhouse heating was 10.9 kWh without solar collector assisted heating,and the heating electric energy consumption in greenhouse was 0.17 kWh·m-3.The weight of the maximum single fruit was 32.3 g,the soluble solids content was 12.5%,and the strawberry yield planted in the solar greenhouse was 1.56 times that of the normal greenhouse.Compared with the greenhouse with stepped heating mode,the heating uniformity of parallel stereoscopic heating mode was better.The total yield of strawberry was 1.2 times that of stepped heating mode,and the average soluble solids content was 13.4%.?2?Two photovoltaic?PV?greenhouses with different PV modules and different coverage areas were built,and the energy generated by different installation angles was simulated.The shading area model of PV modules in greenhouse was established,and the best range of light intensity suitable for the growth of‘Jingzangxiang'strawberry was studied in Kunming of low latitude and high altitude.The results showed that the maximum energy of the semi-transparent photovoltaic?STPV?modules covering 20%of the greenhouse roof area and the opaque photovoltaic?OPV?modules covering 25.9%of the greenhouse roof area were 388 and 880 kW·h respectively when the installed angle was 30 degrees.The shading model of OPV modules was suitable for simulating the shading area during 11:00-14:00.The temperature shaded by STPV and OPV modules was 1.1°C and 2.9°C lower than that in the unshaded area,respectively,but the effect on relative humidity was less.When the strawberry grew faster in the morning,the relative chlorophyll content of strawberry leaves below the PV module was 50.0-70.0 mg·g-1,the light intensity of the STPV and the OPV greenhouses were 38700-49300 Lux and 35300-38800 Lux,respectively.9:00-11:00 The soluble solids content of strawberry in the STPV and the OPV greenhouses were 15.7%and 16.4%respectively,which were higher than that of unshaded strawberry samples,the quality and yield of strawberry samples under OPV modules were better than those under STPV modules.?3?The greenhouse with the solar thermal photovoltaic coupling mode was constructed,and the energy conversion between solar thermal and photovoltaic was analyzed.The effects of temperature and light on strawberry characteristics in greenhouse with solar thermal photovoltaic coupling mode were studied.The results of the study showed that the solar thermal photovoltaic system could effectively provide energy for the greenhouse and the COP of solar combined heat pump heating system was 3.4-5.2 in the sunny condition.The indoor average temperature and relative humidity under the shade of photovoltaic modules were 2.9°C and 1.8%lower than those in the unshaded area,respectively.The optimal photosynthetically active radiation?PAR?for the growth of‘Jingzangxiang'strawberry growth in daytime was 387-437?mol·m-2·s-1 and the most suitable temperature range was20.5-27.4°C.Under the coupling effect of temperature and light of night heating and day shading,strawberry fruit under PV modules shading had better quality and higher yield per plant than that without shading.?4?The ANN model was constructed based on the greenhouse environmental parameters of solar thermal photovoltaic coupling mode.The temperature,relative humidity and light environmental parameters of greenhouse were predicted and validated,and the chlorophyll content of strawberry growth index was predicted.The predicted results were evaluated.The results showed that the coincidence index of chlorophyll content prediction is 0.955,which verifies the high accuracy of this model.It was suitable for measuring the greenhouse environment of solar thermal photovoltaic coupling mode.According to the highest chlorophyll content of strawberry between 12:00-14:00,the optimum average temperature was 26.3°C,the average relative humidity was 41.2%,and the average PAR was 284.8?mol·m-2·s-1for‘Jingzangxiang'strawberry. |
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