| Low temperature environment in winter was an important reason for limiting the growth of greenhouse plants.In China,the general heating method was to heat the whole greenhouse,but for dwarf plants,the heating of the upper space of the greenhouse was a waste of energy.In order to solve the problem that the potted plants in greenhouse without heating equipment in the Yangtze river delta region in winter were vulnerable to low temperature and cold damage,and the traditional heating method has low energy consumption efficiency for dwarf plants,and it has environmental pollution.This paper designed a root zone heating system suitable for plants.Plant the plant in an energy-efficient nested double-layer pot.The accuracy of root heating system was studied,the effects of different root zone temperatures on above ground parts(stems and leaves)and growth(growth and dry matter accumulation)were studied.The energy consumption comparative analysis of the root zone heating system and its practicability was analyzed.The main research contents and conclusions are as follows:(1)A nested double-layer pot was developed.The intercalation using low heat transfer coefficient,bibulous rate was small,long service life of polyurethane foaming agent as insulation materials,cultivation basin within respectively placed two pieces of silicone rubber heating plate,simulating the thermal conductivity of the double-layer basin of cultivation model,the results show the power of 80W/m2 is relatively reasonable heating plate power.(2)The hardware part of the temperature control system was built.The hardware selection and layout were completed according to the system requirements.STM32F4 single-chip microcomputer was used as the main controller of the whole system to complete the design of temperature acquisition module,temperature control module and display module.(3)Temperature control adopts fuzzy PID algorithm,temperature sensors for real-time acquisition of plant root zone temperature,the measured temperature value compared with the set temperature,temperature deviation and temperature deviation change rate as input of fuzzy controller,PID parameter adjustment amount as output,STM32 microcontroller output signal to relay to control the heating power,through experiment showed that the relative error of the temperature control system was kept between 0 and 4.53%,so the system with good accuracy and stability.(4)Set experiment to observed the different temperature of root zone(CK,15℃,20℃,25℃)on the influence of the temperature of plants and the growh of plant,the test results showed that in the absence of solar radiation,the temperature distribution of plant canopy shows a trend of decreasing from the highest temperature at the bottom to the top.Under the condition of the continuous low temperature(the average temperature was lower than 5℃)for a week,the height of plants to the ground part of 25～35 cm(stem,stem and leaf)average temperature compared with the control group in plants,daytime respectively increased by 1.4℃,2.6℃ and 3.7℃,and at night respectively increased by 2.1℃,2.9℃and 4.0℃.In addition,the plant growth(plant height,stem diameter,leaf number,leaf length and leaf width)and the accumulation of dry matter were found more significant in root zone heated plants as compared to control group.The experiment showed that the heating method designed in this paper can not only increase the temperature in the root zone of plants effectively,but also increase the temperature of the aboveground part of plants,and make full use of the heating load.In a continuous low-temperature environment,the influence of low-temperature stress on the growth of winter plants could be alleviated under certain conditions.(5)Compared with common pot(monolayer pot without thermal insulation materials),the energy conservation of cultivation basins was analyzed.The experiment proved that in 15℃,20℃,25℃ three root zone temperature,heating cultivation of plants for two weeks,a statistical average power consumption,heat preservation pot save electric energy 24.2%,25.3%and 23.8%respectively,energy saving effect was obvious.(6)A comparative energy consumption analysis between the insulated heating cultivation pots and coal-fired boilers heating system by using an energy consumption model during the experiment.The same cultivation environment(the same external conditions,such as solar radiation,temperature,etc.)for both root zone heating methods for the purpose to obtain similar plant growth condition were adopted.The analysis results showed that the heat storage pots have lower energy consumption,low cost and no environmental pollution problem,and the heat pots were economical and practical as compared to coal fired heating method. |
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