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Air conditions are usually used to control the environmental parameters in plant factories with artificial light. Among them, the air velocity is generally lower than the optimum range of 0.1-1 m/s that is required for plant growth. The occurrence of tipburn behavior is often observed on the inner and newly developed leaves of lettuce plants, especially during the last days of transplanting. It is very necessary to properly design the airflow in the indoor cultivation systems, thus promoting the growth for less occurrence of tipburn in the lettuce plants. The perforated air tubes can be used to improve the airflow. However, this ventilation scheme is required by the installation of pipelines in the plant factory, inevitably leading to an increase in the installation process and the complexity of the project. In this study, a kind of air-conducting cultivation tank was designed to integrate with the cultivation bed (CBT). The airflow disturbance increased inside the crop canopy in the multi-layer cultivation mode of the plant factory, indicating the simple construction of the ventilation pipe. A model of CBT was also constructed using three-dimensional Computational Fluid Dynamic software (CFD). The airflow velocity was simulated and measured inside the plant canopy with the inlet velocity of 5 m/s. The root mean square error was 0.22 m/s between the calculated and measured airflow velocity. There was a consistent distribution of the simulated and measured geometric center section in the cultivation area, indicating the accurate simulation of the airflow velocity. The validated model was used to simulate the effects of different air inlet velocities on the airflow direction and distribution inside the crop canopy. The simulation results showed that the airflow entered the crop canopy area via the holes of the cultivation pipe, thus forming a regular airflow beam profile. There was a larger airflow area of high velocity in the crop canopy with the increase of the inlet airflow velocity. Once the inlet velocity was 6 m/s, the percentage of volumes was 56.3% inside the plant canopy with the air velocity between 0.1 and 1 m/s, and the volume-weighted average air velocity was 0.15 m/s in the canopy interior. Correspondingly, 6 m/s was selected as the entrance speed of CBT, where the mature lettuce was used as the test material. The microenvironment was compared in the inner part of the lettuce canopy under CBT and traditional ventilation control mode (TVC) under the same environmental conditions. A systematic investigation was carried out to test the effect of ventilation and temperature regulation on the air flow velocity. The results showed that the air temperature was 22.4 ℃ inside the canopy under CBT treatment during the light period, which was lower than the TVC treatment of 23.7 ℃. There was a relatively less significant difference in air temperature in the dark period. The average air relative humidity in the light and dark periods inside the canopy under the CBT treatment was 65.8% and 71.6%, respectively, which were 5.6% and 8.7% lower than those under the TVC treatment. As such, the CBT greatly contributed to the regulation and control of various micro-environmental parameters inside the crop canopy, compared with the traditional ventilation mode. The finding can provide the promotion value to reduce the requirements of environmental control for the high efficiency of air conditioning temperature. [ABSTRACT FROM AUTHOR]

The plant factory realizes environmental control and plant growth prediction by integrating environmental data, monitoring plant growth conditions, utilizing computers to make dynamic adjustments, and ultimately carrying out environmental control to realize the planned annual production of plants. However, its internal temperature and airflow space distribution are uneven between the two sides and the middle cultivation shelf, the same row of cultivation shelves between the different layers of shelves has a certain temperature and airflow speed difference. Airflow velocity is related to the position of the air inlet, within the direct radiation range of the air inlet, the airflow flow is intense, the airflow velocity is large, and the air exchange efficiency is high; while not in the direct radiation range of the air inlet area, the airflow flow is slow, the velocity is small, and the air exchange efficiency is low. Traditional plant factories have large differences in environmental factors, resulting in poor plant growth consistency. Therefore, the air inlet setting is the key to solving the problem of large differences in local environmental factors within the airflow plant factory. At present, most studies on airflow circulation patterns inside plant factories take the position, number, and angle of air inlets and outlets as the entry points. The effect of airflow circulation in plant factories is significantly affected by the internal structure, and it is worthwhile to study whether it is possible to improve the uniformity and stability of the distribution of environmental factors in plant factories by optimizing the airflow circulation mode and improving the internal structure. In this study, we improved the setting of the air inlet of the plant factory, designed a plant factory with a full mesh ventilating wall under the air circulation mode of side inlet and top outlet, compared the uniformity of the distribution of the environmental factors in the plant factory with and without the full mesh ventilating wall, which was simulated by computational fluid dynamics (CFD) software, and analyzed the temperature, air temperature, and air temperature in this type of plant. We analyzed the changes in temperature, airflow velocity, CO2 concentration, relative humidity, percentage of suitable wind speed, air age, and specified streamline velocity under this type of plant to evaluate the improvement effect of the full mesh ventilation wall on the local environmental differences in the plant factory. The full mesh ventilation wall type plant factories designed by this institute changed the original airflow trajectory, increased thermal convection, promoted greenhouse cooling, and improved temperature distribution uniformity. The full mesh ventilation wall type plant factories increased the airflow flow in the middle and lower layers, alleviated the stagnant airflow area percentage of the original structure, increased the percentage of suitable wind speed area by 20.05% compared with that of the type without a full mesh ventilation wall, and significantly improved the CO2 distribution uniformity in the plant factory. The relative humidity of this design is better than that of the plant factory without full mesh ventilation wall type, and the uniformity is significantly improved; the average air age of this design is only 1/9 of that of the side inlet and top outlet type, which is 7.5 s; and the air renewal efficiency is effectively improved. The study shows that the full mesh ventilation wall structure has a significant effect on the uniformity of the distribution of environmental factors in the plant factory. [ABSTRACT FROM AUTHOR]

Stereo cultivation is usually used in plant factories for seedling and cultivation. Transportation of cultivation bed is an important part of the stereo cultivation automation. At present, cultivation bed is mostly handled manually, which has problems such as high labor intensity and low level of automation. To solve this problem, a multifunctional operation platform, which had the functions of autonomous tracking, automatic positioning, and automatic conveying of cultivation bed, was developed in this paper. The multifunctional operation platform mainly consists of navigation system, positioning system, communication system, walking system, lifting system, automatic docking system, and automatic conveying system. The working principle and technical parameters of the multifunctional work platform were introduced. During operation, the cultivation bed was transported from nursery workshop to greenhouse by the multifunctional operation platform firstly. Then， the multifunctional operation platform reached the target stereo cultivation rack through the road reserved in greenhouse and lifted the cultivation bed to the target height. The automatic conveying mechanism started to push cultivation bed to stereo cultivation rack by automatic docking mechanism. The cultivation bed was transported to stereo cultivation rack when the proximity switch installed on stereo cultivation rack detected the cultivation bed. Finally, the multifunctional operation platform stopped working and go back to the charger area. When the crops were mature, the multifunctional operation platform would automatically transport the cultivation bed to the picking area, so as the logistics automation of the crop production process was realized by the multifunctional operation platform. To meet the requirements of multi-layer cultivation of stereo cultivation rack, the lifting mechanism was designed based on principle of virtual displacement according to the weight of the cultivation bed and the height of the stereo cultivation rack. Single hydraulic cylinder driving and two scissor lift mechanisms were chosen. The maximum driving force of the hydraulic cylinder was about 15 443.9 N through theoretical analysis. The length, stroke, outer diameter and inner diameter of the hydraulic cylinder were determined to 940, 360, 63, and 35 mm respectively. The automatic docking and automatic conveying mechanism of the cultivation bed were studied. The automatic docking was realized between the multifunctional operation platform and stereo cultivation rack by automatic docking mechanism, and two-way transportation of the cultivation bed was realized by automatic conveying mechanism. Thus, the automatic loading and unloading of the cultivation bed was realized. The positioning system based on the RFID (Radio Frequency Identification) sensor was determined. Walking system and the lifting mechanism of the working platform would stop working when the RFID sensor detected the electronic labels on the ground and stereo cultivation rack.STM32 was used as the main controller of the automatic control system. The software and hardware of the control system were designed. A human-machine interaction interface was designed based on the Android. It was to monitor the motion status and operating parameters of the multifunctional operation platform in real time. To evaluate the operation performance of the multifunctional operation platform, the experiments were conducted. The test indexes were the height range of the lifting mechanism, the front and rear positioning deviation, the height positioning deviation, and the success rate of the platform and the stereo cultivation frame docking. The experiment results show that the height range and effective lift height of the multifunctional mobile platform was 833-2 460 mm and 1 627 mm. The front and rear positioning deviation is less than 9 mm, average value was 4.5 mm. The height positioning deviation was less than 5 mm, average value was 3.7 mm. And the docking success rate was not less than 96%, which meet the requirements of the operation. This study provides a reference for further improving the automation level of stereo cultivation of plant factories. [ABSTRACT FROM AUTHOR]

Much more cultivation layers and high canopy density have posed great challenges to the even distribution of airflow in plant factories. It is highly required for the optimal design of airflow distribution systems, thereby improving the physiological orders and post-harvest quality for a high commercial value of the products. In this study, a ventilation system was designed with the three parallel lines of perforated air tubes, further to generate a constant airflow inside the plant canopy. The air tube was fabricated in a diameter of 0.02 m with a length of 1.5 m using the layout and size of a cultivation shelf. Each air tube was equipped with two rows of jets. A three-dimensional computational fluid dynamics (CFD) model was developed to analyze the distribution of airflow in the plant’s canopy under different inlet velocities. Furthermore, the lettuce leaves were assumed as the porous medium with the drag coefficient of 0.02, resulting in a viscous resistance factor and the inertial resistance factor of 25 and 1.3, respectively. A LED lamp (Ø0.02 m) was assumed as an aluminum substrate and a glass part. An energy term with a constant heat generation of 297 525 W/m3 was also defined as the heat source lost by the volumetric convection from the LED lamp aluminum substrate part for the heat dissipation. The average error of simulated air velocity was 16%, compared with the measured. Three groups of air velocity (lower than 0.1 m/s, between 0.1 and 1.0 m/s, and higher than 1.0 m/s) were selected to calculate the proportion of the areas of the plant’s canopy surface and the volume proportion inside the plant’s canopy. The results showed that the percentage of air velocity at the lettuce canopy surface between 0.1 and 1 m/s increased from 33.33% to 68.57%, while, the percentage of volumes inside the plant’s canopy increased from 44.84% to 77.08%, respectively, when the air velocity increased from 6 to 9 m/s. By contrast, the percentage of volumes inside the plant’s canopy increased from 0.01% to 0.06%, with the air velocity higher than 1.0 m/s. The maximum distance between the ventilation pipe and high airflow increased from 50 to 70 mm. Therefore, the air velocity was recommended as 8 m/s, further to avoid the air velocity higher than 1 m/s plants canopy. At the inlet air flow velocity, the percentage of volumes inside the plant’s canopy with the air velocity between 0.1 and 1 m/s was 67.58%, the percentage of areas on the plant’s canopy surface with the air velocity between 0.1 and 1.0 m/s was 55.23%, and the volume-weighted air velocity in the canopy was 0.14 m/s. This finding can provide a new solution to improve the canopy environment in a plant factory. Much more cultivation layers and high canopy density have posed great challenges to the even distribution of airflow in plant factories. It is highly required for the optimal design of airflow distribution systems, thereby improving the physiological orders and post-harvest quality for a high commercial value of the products. In this study, a ventilation system was designed with the three parallel lines of perforated air tubes, further to generate a constant airflow inside the plant canopy. The air tube was fabricated in a diameter of 0.02 m with a length of 1.5 m using the layout and size of a cultivation shelf. Each air tube was equipped with two rows of jets. A three-dimensional computational fluid dynamics (CFD) model was developed to analyze the distribution of airflow in the plant’s canopy under different inlet velocities. Furthermore, the lettuce leaves were assumed as the porous medium with the drag coefficient of 0.02, resulting in a viscous resistance factor and the inertial resistance factor of 25 and 1.3, respectively. A LED lamp (Ø0.02 m) was assumed as an aluminum substrate and a glass part. An energy term with a constant heat generation of 297 525 W/m3 was also defined as the heat source lost by the volumetric convection from the LED lamp aluminum substrate part for the heat dissipation. The average error of simulated air velocity was 16%, compared with the measured. Three groups of air velocity (lower than 0.1 m/s, between 0.1 and 1.0 m/s, and higher than 1.0 m/s) were selected to calculate the proportion of the areas of the plant’s canopy surface and the volume proportion inside the plant’s canopy. The results showed that the percentage of air velocity at the lettuce canopy surface between 0.1 and 1 m/s increased from 33.33% to 68.57%, while, the percentage of volumes inside the plant’s canopy increased from 44.84% to 77.08%, respectively, when the air velocity increased from 6 to 9 m/s. By contrast, the percentage of volumes inside the plant’s canopy increased from 0.01% to 0.06%, with the air velocity higher than 1.0 m/s. The maximum distance between the ventilation pipe and high airflow increased from 50 to 70 mm. Therefore, the air velocity was recommended as 8 m/s, further to avoid the air velocity higher than 1 m/s plants canopy. At the inlet air flow velocity, the percentage of volumes inside the plant’s canopy with the air velocity between 0.1 and 1 m/s was 67.58%, the percentage of areas on the plant’s canopy surface with the air velocity between 0.1 and 1.0 m/s was 55.23%, and the volume-weighted air velocity in the canopy was 0.14 m/s. This finding can provide a new solution to improve the canopy environment in a plant factory. [ABSTRACT FROM AUTHOR]

LEDs are more commonly used than fluorescent lamps in plant factories with artificial light for energy savings. But the LEDs cannot convert the input power to light at 100 % efficiency. Part of energy can be converted into heat, and then be transferred to the ambient environment, in terms of heat conduction, radiation, and convection. However, heat dissipation of LEDs has become a great challenge, as the power increased while the volume of LEDs reduced. In this study, a circular serrated water-cooled LED was designed to transmit the heat generated by LEDs in time for a longer service life. A three-dimensional computational fluid dynamic (CFD) model was developed to assess the design, where the LED bubbles were set as the internal heat source. The electrical efficiency was assumed to be 32% and 49% in the red (wavelength: 655 nm) and blue (wavelength: 455 nm) LEDs, respectively. The heat flux of 1.7×107 W/m³ was calculated, according to the number of lamp beads and the electrical to light conversion efficiency. The constructed grids were approximately 1162800 for each case, including 220881 nodes with a minimum element size of 2 mm. Much finer meshes were automatically imposed near the bubbles with proximity and curvature size functions in meshing. The SIMPLE was selected for the pressure-velocity coupling. A least-square cell-based scheme was used for the gradient term in spatial discretization. The second-order scheme was applied for the pressure term. The second-order upwind discretization schemes were used for momentum and energy equations, whereas, the first-order upwind discretization schemes were used for turbulence equations, mainly for higher accuracy. The convergence criterion was set as 10-6 on energy and 10-3 on continuity, momentum and viscous terms. Inlet and outlet boundary conditions were set for the numerical solution using the velocity-inlet and pressure-outlet. The inlet water velocity and water temperature were set as 0.2 m/s and 297 K, respectively. The simulated value of the LED water-cooled lamp was close to the measured value, with the maximum error of 16.4%, indicating that the CFD model could accurately simulate the temperature distribution of each structure of the lamp. The validated model was used to simulate the influence of different water flow velocities on the temperature distribution and water flow pressure drop in a water-cooled LED lamp. The results showed that the temperature distribution of bubbles and water flow was relatively uniform, and the structure of the lamp was reasonable. The heat released by the bead chip was quickly transferred into the water flow; when the inlet velocity of the lamp increased from 0.10 to 0.25 m/s, and the difference of water temperature between the inlet and outlet dropped from 1.4 ℃ to 0.5 ℃. Therefore, a series of connected lamps were calculated, according to the temperature difference between the inlet water and the ambient air, when the water-cooled LED lamps were connected in series. The inlet flow velocity also improved the flow resistance, where the resistance coefficient of lamps to the water flow was 2.2. [ABSTRACT FROM AUTHOR]

Groundwater source heat pumps have high efficiency and environmental protection in greenhouse temperature control. Most importantly, the operating energy consumption can be further reduced if the water storage technology were combined. Although the energy storage type ground source heat pump plant factory energy supply system avoids the problems of low primary energy utilization and serious pollution in traditional fossil energy supply, it currently lacks long-term operating experience. This study takes Shanghai Chongming Natural Light Plant Factory as an example to optimize the energy-saving operation of the energy storage groundwater source heat pump energy supply system. The total area of the plant factory is 21 000 square meters, which is divided into three areas A, B and C. The 7 greenhouses in area A use an energy storage groundwater source heat pump air-conditioning system with an area of 5 880 square meters. The greenhouse uses two cylindrical concrete storage tanks, of which the volume of the thermal storage tank is 400 cubic meters and the diameter is 7.65 meters; the volume of the cold storage tank is 600 cubic meters and the diameter is 9.29 meters. The plant factory has 2 hot water wells and 2 cold water wells. In winter, water was drawn from the 2 hot water wells and passed through a convection plate heat exchanger to exchange heat with the cold water flowing from the cold water tank. The low-temperature water after the heat exchange was pumped back by pressure fill 2 cold water wells. Under typical operating conditions in winter, the output temperature of hot water wells was basically maintained at 16-20℃.The inlet water temperature of cold water wells remained stable at about 7℃, and the pumping flow of hot water wells was maintained at about 40 m³/h. According to the statistics of the operating parameters of the heat pump in the first quarter, it could be concluded that the four output water temperatures and input water temperatures of the heat pump remain stable, and the heat pump operated normally during the heating season. The power consumption of the heat pump in the first quarter was 208 559.5 kWh. Among them, the power consumption in January was 83 525.9 kWh, February was 76 673.3 kWh, and March was 48 360.3 kWh; the total heat output to the greenhouse and hot water tank was 3 542.7 GJ, of which 1 445.9 GJ was output in January and 1 258.6 GJ was output in February. In March, the heat output was 838.2 GJ; in the first quarter, the total heat pump operation was 1 322.8 h, including 557.7 h in January, 454.4 h in February, and 310.7 h in March. After research, there are three unreasonable operating conditions of the system: A. The heat pump continued to supply heat when the plant factory heat load s negative; B. The heat pump output excessive heat to the hot water storage tank; C. The heat pump was still running during peak hours. After optimization and control, to avoid the A operation, the heat pump could finally reduce the output energy by 21.55 GJ in the first quarter, which could reduce the power consumption by 1 012.50 kWh, which could save 747 yuan when converted to electricity price; to avoid the B operation, set the upper limit of hot water charge rate at 85% in the first quarter, which can reduce the output of 97.2 GJ energy under the premise of ensuring that the heat pump is fully powered by the plant factory; to avoid the C operation, to avoid the C operation, assuming that the heat pump was used during the price trough, the total output energy of the heat pump was unchanged. Transferring the heat of the heat pump 140.25 GJ in the first quarter to the parity stage output could save 5 530 yuan, and the total power at this time was 8 654.07 kWh, at this time, the total amount of electricity was 8 654.07 kWh. By optimizing the operation process of the natural light plant factory's energy supply system, energy saving and consumption reduction can be achieved, and economic operation can be achieved. [ABSTRACT FROM AUTHOR]

It is important for crop growth to maintain suitable temperature in plant factory, however large heating energy consumption has been proved to be an obstacle that restricts its development. In Europe, the cost of heating accounts for about 30% of the total operation cost during the winter, but in the north of latitude 43° of China, the proportion reaches 60% to 70%. The traditional heating equipment such as coal-fired boilers has an energy utilization rate of only 40% to 50%. So it is very necessary to apply renewable energy to plant factory. Regulating heating modes by tracking and predicting the heating load changes in plant factory is the key to achieve energy saving. Because of the high energy consumption in winter, accurate heating load prediction can improve the energy saving effect of groundwater source heat pump with water energy storage. Changes of heating load in natural light plant factory are dynamic, time-varying, highly turbulent and uncertain. Artificial neural networks is ideal for predicting load changes, especially BP (back propagation) neural network has strong nonlinear mapping ability, which is generally used by many scholars for building heating load prediction, but rarely in plant factory. Given that heating load of both plant factory and building have nonlinear characteristics, we used BP neural network to predict the next day's heating load of plant factory to promote energy-saving control optimization. The BP neural network model has three levels: input layer, hidden layer and output layer. Input parameters include indoor and outdoor air temperature, solar radiation intensity, indoor relative humidity, indoor absolute humidity, indoor wind speed, etc. For plant factory, the next day's weather condition has a significant impact on the heating load. The output variable is determined as the next day's hourly glass greenhouse load value. The number of neurons in the input layer was 9, the number of neurons in the hidden layer was 13, the selected layer number of hidden layers was 1, the learning rate was 0.25 to 0.30, and the initial momentum factor was 0.9. Common evaluation indicators used to determine whether the neural network converges, included standard deviation, coefficient of variation, and expected error percentage. After algorithm steps being determined, the next day's heating load was predicted based on reasonable algorithmic procedures and steps. Experimental data in the paper was obtained from a natural light plant factory powered by groundwater source heat pump with water energy storage system in Chongming National Facility Agricultural Engineering Technology Research Center. Using the neural network toolbox of Matlab to train and simulate the model to process the experimental data from January 19th to 28th, the value of the error function was 0.002 999 94 which was less than the set value of 0.003, so the neural network was convergent. Prediction effect can be drawn by comparison between the actual surveyed value and the predicted value of the heating load. The main heating load was concentrated on 0:00-6:00 and 17:00-24:00 o’clock in the plant factory, and most of these periods were in the cheap electricity price period of Shanghai. Adjusting the operating strategy and operating mode of the energy supply system were based on the predicted heating load，the heat pump operated at full load or high load during the period of cheap electricity prices, and excess heat was stored in the hot storage tank. The hot storage tank provided heat to plant factory during the period of moderate and expensive electricity price. In this case, the energy cost would be reduced. Therefore, it was significantly economical to control start-stop time of the groundwater source heat pump with water energy storage for plant factory heating project. The error was controlled within ±6% basically between the actual value and the predicted value of the heating load, and the standard deviation was 27. 54, deviation factor was 9.4%, expected deviation percentage was 4.35%. Therefore, the results showed that the BP neural network was suitable for the next day's heating load prediction of plant factory. [ABSTRACT FROM AUTHOR]

Virus-free seed potato is the basis for potato production in field. Nutrient solution cultivation technology for virus-free seed potato can maximize the potential of seed multiplication and avoid bacterial infection. It is now deficient in the systematic research on the management of the nutrient solution for the virus-free potato cultivation in the LED (light emitting diode) plant factory, and the effective guidance for the whole growth duration of potato has not been put forward. This research tried to investigate the influence of nutrient solution management on the whole growth and tuberization of virus-free potato plantlets. The virus-free plantlets were acclimatized for 7 d, and then the plantlets with the height of 6-8 cm were transplanted into vermiculite. The light intensity was set at 300 μmol/(m2·s-1) and the daytime and night temperature were (22±1) ℃ and (16±1) ℃ respectively. Three different tests were performed, and in the first test 3 different formulas of nutrient solution were set up: Hoagland nutrition solution (H), mixed nutrition solution (MX) and Japanese garden test nutrition solution (J). In the second test, for 3 stages i.e. seedling stage, tuber formation and expansion period and mature stage, different combinations of nutrition solution concentration were set up: 0.8MX+0.8MX+0.8MX (A), 0.8MX+MX+0.6MX (B) and 0.8MX+1.2MX+0.6MX (C). In the third test, different combinations of nutrition formula and concentration were set up: H+MX+0.6MX (D), 0.8MX+MX+0.6MX (E) and 0.8MX+MX+0.7MX (F). Different nutrient solutions were watered at seedling stage, tuber formation and swelling stage, and mature stage. The results showed that the leaf area and chlorophyll content of H treatment were significantly higher than MX treatment at seedling stage, indicating that Hoagland nutrient solution had more advantages on the early growth of potato plants. Tuber number per plant, effective tuber number per plant and the ratio of plants whose effective tuber number was more than 3 treated by MX were 3.2, 2.8 and 83.33%, respectively, which were significantly higher than J and H treatment. At tuber formation and swelling stage, 0.8MX caused the plant to grow thinly and 1.2MX inhibited the plant height elongation, and the 1.0MX treatment was beneficial to plant morphological development. At mature stage, tuber number, effective tuber number, tuber mass, effective tuber mass per plant and the ratio of plants whose effective tuber number was more than 3 under the B treatment were 4.0, 3.5, 23.66 g, 23.18 g and 100% respectively, which were significantly higher than A and C. The plant height, shoot dry mass, leaf area and tuber number and mass of the 0.6MX treatment were higher than the 0.7MX, indicating that the 0.6MX was conducive to the formation of the tuber number and yield. Tuber mass, and effective tuber mass per plant under the D treatment were both 29.78 g, which were significantly higher than E and F. Taking into account the convenience of management and control in nutrition solution in the plant factory, the reliability in management and the stability of system, the management of H+MX+0.6MX nutrition solution for the production of virus-free potato tubers has more advantages in LED plant factory. [ABSTRACT FROM AUTHOR]

Protected agriculture was one of the highest forms of modern agriculture, which had been the focus of world agricultural development in each country. The demand for organic fruit and vegetables accounted for around 30%-40% of the global demand, but the total area for organic vegetable production was only 0.5% of the total area of vegetables grown in the world. Although it was generally considered that the output of organic agriculture was 10%-20% lower than that of conventional agriculture, it exceeded conventional agriculture in terms of economic benefits, environmental impact, and social benefits. It also had a positive performance in providing nutrition, adapting to climate change, promoting soil health, protecting biodiversity, increasing employment and creating new economic model. In the face of rapid population growth, climate change and environmental degradation in the 21st century, new organic greenhouse horticulture was the major force for sustainable agricultural development. The total area for organic greenhouse horticulture was estimated to be over 8302 hm2 (1.8% of total vegetable greenhouse area). There were 5236 hm2 in European Union and 3066 hm2 in Non-European Union. With the rapid development of agriculture in the world, the organic greenhouse horticulture had been shown to be sustainable, productive and profitable in foreign countries, but the standards of organic greenhouse horticulture were still a blank in China. This paper introduced the background, definition, origin, objectives, area of organic certification, yield and profitability, the basic forms of organic greenhouse horticulture and the rules of certification, and analyzed the feasibility and problems on the organic greenhouse horticulture in China: 1) Certification standards of organic greenhouse horticulture were lacked. 2) Greenhouse ecological environment had been deteriorated. 3) Plant varieties for greenhouse were scarce. 4) There were only a few studies on organic greenhouse horticulture. The feasibility of the development of organic greenhouse horticulture in China was further analyzed. It was suggested that organic greenhouse horticulture should be actively developed in China, but organic greenhouse horticulture cannot be simply equivalent to “greenhouse + organic planting”. It should be an integration with sustainable development, which consisted of greenhouse climate control, planting material, soil fertility, water management, disease and pest management, energy conservation and sustainability. However, to promote the development of organic greenhouse horticulture in China, we need to implement it based on national conditions and learn the rules of the foreign organic greenhouse horticulture. Moreover, the basic research of the biological agriculture in our country should be strengthened: 1) Strengthen the formulation of organic farming laws and industry standards in China, and point out the development goals and technical requirements of organic greenhouse horticulture. 2) Strengthen basic research in bio-agriculture to propose novel theories, technologies and equipment for protected agriculture. 3) Strengthen the development of agricultural machinery for organic greenhouse horticulture. The aim was to compensate for the lack of manpower, increase production efficiency and transform people’s bias that organic agriculture has low yield and inefficiency. 4) Strengthen the demonstration and promotion of organic facilities horticultural technology integration. We need to construct a diversified organic facility horticultural extension service system with national public welfare promotion institutions as the main body, scientific research units, colleges and universities, agriculture-related enterprises, professional cooperative organizations and consumers participating in it. The system can provide information and technical services for farmers and consumers, which can ensure the sustainable development of the protected agriculture industry in China. [ABSTRACT FROM AUTHOR]

With the rapid development of modern agricultural technology, plant factory has become the most advanced development stage of facility agricultural. At present, the majority of work tasks in plant factory completed by manpower are labor-intensive and low efficient, therefore, the agricultural intelligent equipment system has become a hot spot in the development of plant factory. In view of the task demand of the carrying and spraying of the three-dimesional seedling tray, the three-dimesional seedling tray management robot was developed. In order to make the manipulator of three-dimesional seedling tray management robot complete all carrying and spraying tasks flexibly and efficiently, meanwhile to reduce operating space and structure size of manipulator, parameters of the manipulator were optimized by the method of theory and experiment. Firstly, in order to determine the relationship between the end coordinate of the manipulator’s connecting rod and the base coordinate system, the kinematic model of the robot system was established by D-H method, which was important theoretical basis for the workspace analysis. Then the workspace of manipulator was constructed by graphic method, and the workspace constraint conditions were determined according to the condition that manipulator workspace accommodated target workspace. Based on that, the objective function was established according to shortest distance and compact structure, and genetic algorithm was used to solve the objective function. The optimal rod lengths (big arm, medium arm, small arm) of the manipulator were 648, 472, and 396 mm, and the limit values of the optimal joint angle were 96○, 68○, and 126○. The workspace and the target workspace of the robot were depicted in the MATLAB (Matrix Laboratory) software platform according to the optimal solution of the manipulator parameters, the kinematics equation of the robot and the range of the manipulator’s parameters. The simulation result showed that the target workspace was between the inner limiting envelope interfaceand the outer limiting envelope interface of the manipulator, which verified the manipulator’s ability to cover the target workspace, and the rationality of the theoretical optimization for the parameters of the manipulator was proved. Finally, in order to further validate whether the manipulator could complete all the action tasks of the target workspace, the robot prototype and the three-dimesional seedling tray experimental platform were built in the laboratory, and the motion planning test of carrying and spraying of the robot system prototype was carried out. The carrying test was planned as follows: According to the target workspace size and the theoretical position coordinate value, the manipulator was controlled to move vertically upward from the lowermost (lower limit) to the topmost (upper limit) of the target workspace, this group of actions were repeated 100 times, and seedling tray was always placed horizontally during carrying. The carrying test mainly verified the manipulator’s ability to cover the target workspace in the vertical direction. Spraying test steps were as follows: 1) The initial spraying height value was 100 mm; 2) Divide the seedling disk plane into m×n grids, and each grid point represented the spray position point, m=10, n=20; 3) The target path point group consisted of all the spray points at the current height, and the manipulator was controlled to pass through the target path point group sequentially; 4) The spraying height value was increased by 20 mm; 5) Repeat step 2), 3) and 4) until the spraying height value was equal to 1 020 mm. The spraying test mainly verified the manipulator’s ability to cover the target workspace in the horizontal direction. The high-speed video camera system was used to mark trajectory coordinates of manipulator in the motion planning test of carrying and spraying (high-speed camera was KODAK’s color CCD (charge coupled devices) camera, a resolution of 512×480 pixels, frame rate of 125 frames/s). Test results showed that the optimized manipulator could reach all limiting positions and other characteristic positions of target workspace, and the maximum relative positioning error was 0.98% which was within error range and could meet the accuracy requirements for manipulator containing the target workspace effectively; what was more, it was proved that the optimal parameters of manipulator were reasonable. Parameters optimization and experiment of three-dimesional seedling tray management robot could provide the reference for trajectory planning and motion control. [ABSTRACT FROM AUTHOR]

Forage grass is an important material basis and security guarantee for the development of livestock industry. Forage grass with high quality not only provides adequate nutrition for livestock, but also has important impact on the quality of livestock products. Alpine areas are not suitable for planting corn, alfalfa, and other conventional forage grass because of the insufficient accumulated temperature and transient frost-free season. However, the forage grass requirement of herbivorous livestock is large, for example, one sheep requires 657 kg hay per year, and it is very inelastic. In this case, shortage of forage grass has become a key limiting factor of herbivorous animal husbandry development and grassland ecological construction due to the dual pressures of the natural grassland degradation and the grazing blocked by fencing in alpine region. Plant factory is a new agricultural model which can achieve the purpose of efficient crop production by high-precision environmental control in facility. Though research and practice of plant factory in China have achieved the gratifying results in recent years, applying this technology to the forage grass production is still blank. For the energy-saving production of fresh forage grass in poor environment such as the alpine region, a container-type plant factory was designed and tested. To maximize space usage of the production departments, a six-level hydroponic cultivation system (1.5 m×0.55 m×2.3 m) (length×width×height) was installed. Semi-automatic control of artificial lighting lamps, automatic water circulation, and automatic heating facilities were used to optimize temperature, humidity, light, nutrient solution, and other environmental factors on forage grass production. In a plant factory, the optimal control for obtaining higher yield and better quality of plants was essential. Optimal regulators with temperature sensing probe and humidity sensing probe were used to control the water status and growth temperature of forage grass, and the nutrient solution was supplied by bottom watering. Light emitting diode (LED) fluorescent lamp was controlled by an automatic timing switch. All installation and debugging of facilities and equipments had been completed in a farming cooperatives of Tianzhu County, Gansu Province. Four batches of forage grass production experiments were carried out in January 2015 in order to test the operation and production capacity of equipment. The ordinary merchandise maize (Jinkai 3) bought from Jin Lvyuan Farming Technology Company was used as the experimental material. Maize after harvest was dried to a moisture content that was below 13% and then threshed for later use. The thousand kernel weight of experimental maize after the screening of impurities and broken grains was 330 g while the germination rate was higher than 85%. Temperature of the forage grass factory under natural conditions was between -21 and -4 °C. According to the dimension of seedling tray used in this experiment (54 cm×27 cm×6 cm), we set up 5 treatments with different seed quantity of 300, 350, 400, 450 and 500 g) and each had 5 replicates. The upper and lower limit of the forage grass factory temperature were set to 30 and 26 °C, respectively, and those of relative humidity were set to 85% and 65%, respectively. Supplementary illumination time was from 7:00 to 18:00. The effects of different planting densities on height, growth, root-shoot ratio and other indicators of forage grass were detected under the same conditions. And then the optimum seeding rate and productivity of the system were determined. The first batch of test material was sowed on January 5, 2015. Nine days after planting, the hydroponic forage grass with the seed quantity of 450 g showed the best production performance. The average height and yield were reached 24.96 cm and 1 891.5 g respectively, while the cost reduced to 0.4 yuan producing 1 kg fresh grass. On this calculation, this container-type plant factory could produce 16.33 ton fresh forage grass. Test results show that this factory production installation can meet the needs of pasture plant production in alpine region. [ABSTRACT FROM AUTHOR]

The luminous efficiency and energy consumption of LED (light emitting diode) are affected by heat dissipation of high power LED. In the study, LED surface light source used in plant factory with water-cooled cooling system was designed, and the purpose was to take away the heat generated by the LED using water cycle, to reduce the junction temperature and delay light attenuation of the LED, to distribute the heat according to requirement for heat of plant factory, and thus to reduce energy consumption for controlling temperature. The system was mainly made of LED surface light source, radiator and water circulation system. LED surface light source was made of the high-power LED, with 28 identical array units which were arrayed in 4 rows and 7 columns, and each array unit consisted of 44 LEDs. LED surface light source could give out red, blue, white, green and yellow light or any combination light made by above-mentioned light. Supplying voltage of light source was 220 V, and power of LED was provided by the conversion from 220V AC (alternating current) signal to 0-48V DC (direct current) signal. Electrical energy of the light with different colors was respectively supplied by independent power. Dimmer was used to adjust output DC voltage of the power, to regulate current of the LED and realize the aim of adjusting light intensity. Light intensity of LED surface light source could be adjusted in the range of 0-2000 μmol/(m2·s). The radiator of LED surface light source (length×width×height, 500 mm×400 mm×20 mm) was made of hot galvanized Q235 steel, which was composed of bottom plate, hanging lug, cover plate, etc. Water path of bottom plate was S type. The function of water circulation system was to transfer the heat produced by LED surface light source to water. After giving out heat, water was recycled into the radiator to maintain the temperature of the radiator at a low level. The water circulation system mainly consisted of supplying water tank, constant-flow pump, recycling water tank, valves, radiators, sensors and pipelines, etc. The waterway was divided into 2 parts; in the heating season, the heat was input into plant factory for raising indoor temperature, while in the non heating season, the heat was output to the outdoor, and then water was cooled by air before entering the water circulation system. During the time from 2 to 6 a.m. of November 2, 3 and 4, 2014, the effect of the cooling system of LED surface light source was tested in 13 m2 plant factory in the Life Science Building of Nanjing Agricultural University. Under water cooled and non-water cooled conditions, radiator temperatures of 4 corners on the radiator were measured, and average value for each measurement was recorded. The results showed that water-cooled system had obvious effect of reducing temperature of LED surface light source. Compared with non-water cooled system, plate temperature was lower, which was decreased by at least 5.3℃ and up to 19.3℃. Water-cooled system directly reduces the temperature of the radiator, and indirectly reduces the junction temperature of the LED. And thus it can prolong the service life of LED surface light source. [ABSTRACT FROM AUTHOR]