Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures

Beijing, China

Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures

Beijing, China

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Sun W.,Beijing Academy of Agriculture and Forestry Sciences | Sun W.,Key Laboratory of Agri informatics | Chen X.,Beijing Academy of Agriculture and Forestry Sciences | Chen X.,Key Laboratory of Agri informatics | And 10 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016

The closed greenhouse is a light-permeable greenhouse type, with totally-enclosed architectural structure. Cooling by ventilation is replaced completely by mechanical cooling. Excess solar energy is collected and stored to be reused to heat the greenhouse or other buildings. The closed greenhouse can achieve energy conservation and emission reduction, recycling water of evapotranspiration, maintaining a high level of CO2 concentration, as well as isolating the bacteria spores from external environment, etc. However, high air temperature inside the closed greenhouse is difficult to control effectively in summer, or a great deal of energy is needed to consume, resulting in a restriction of the closed greenhouse when used in actual production. In order to decrease air temperature inside the closed greenhouse, taking low carbon emission and energy-saving into consideration, a closed greenhouse with water-walls (CGWW) was designed and built in Changping District of Beijing, China. With an indoor ground surface of about 7.6 m2, it was supported by a steel skeleton and assembled from some glass tanks filled with water. And for suppressing the growth of green algae, pH value of the water was adjusted to 9.5. Water layer thickness of side walls and roof were 30 and 13 cm, respectively. Cooling characteristics of the CGWW in summer was tested from 26 Jul. to 10 Sep. 2015. During the test, cucumbers and rapes were cultivated inside the CGWW. The results showed that, average air temperature inside the CGWW was 29.4-34.3℃ around noon (10:00-16:00), decreased by 0.8-6.8℃ compared with ambient. Meanwhile, the air temperature drop range inside the CGWW got bigger with the increase of solar radiation or ambient air temperature (P<0.01). In 94.6% of the photosynthesis period (06:00-18:00), air temperature inside the CGWW was controlled within 35℃, which could avoid the high temperature stress effectively. So the CGWW had remarkable effect for cooling in summer. During the nighttime, relative humidity inside the CGWW was controlled within 80%, and the average value was 54.7%-73.7%, decreased by 7.2%-17.5% compared with ambient. Meanwhile, there was a negative linear correlation between humidity difference and temperature difference, inside and outside the CGWW (P<0.01). During the daytime, solar radiation in horizontal direction inside the CGWW was 31.5-67.4 W/m2, and accounted for 11.9%-17.8% of that outside the CGWW. As solar radiation transmitted into the CGWW from outside, ratio of far-red light decreased from 41.9% to 9.2%, with a transmittance of 6.0%, which was conducive to the suppression of high temperature inside the CGWW. Red and blue light had the most ratios and accounted for 23.9% and 27.1% of the spectrum distribution inside the CGWW, respectively, and both of them had an increase compared with outside. And red and blue light had transmittances of 32.4% and 37.5%, respectively, which were far higher than both UV-A and far-red light. Due to the selective permeability of the water-walls for solar spectrum, obviously, high temperature inside the CGWW could be controlled while adequate photosynthetically active radiation could be ensured. In addition, the CGWW showed some of regularity in distributions and daily variation of water-walls temperature and air temperature inside the CGWW. In summary, the CGWW which can obtain an ideal cooling effect, suitable humidity and illumination conditions via its own structure, has been proved to be a feasible, low carbon and energy saving greenhouse type, and will provide a reference and technical supports for the development of closed greenhouses. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.


Liang H.,China Agricultural University | Fang H.,Chinese Academy of Agricultural Sciences | Fang H.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Yang Q.,Chinese Academy of Agricultural Sciences | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

The Chinese Solar Greenhouse (CSG), characterized by an east-west orientation, transparent camber south roof, and solid north roof and east and west walls, is utilized primarily in horticulture in northern China. During the day, the CGS stores solar energy through the north wall and soil, and releases it when the inside air temperature is low. Because of limited energy capacity, during cold winter nights, the air temperature can be very low and this considerably decreases crop production. To increase this low nighttime air temperature, a heat collection and storage-release system was studied. This system was installed at Changping District (latitude 39°54' N, longitude 116°24' E), Beijing, China. The CSG was positioned towards the south along a south-north line. The Solar greenhouse was 49 m long, 8 m wide and 3.7 m high. The roof of the greenhouse was covered with polyethylene terephthalate (PET) films. The north wall and sidewalls were made of red brick and polystyrene board (24 cm thickness red brick inner, 10 cm thickness polystyrene board middle and 12 cm thickness red brick outer). During the experimental period from the 15th of November 2012 to the 20th of January 2013, the crop studied was tomato plants, and the covering layer was opened during the daytime (08:30-15:30) and closed during night (15:30-08:30) in sunny days. The results were compared to the nighttime air temperatures in a reference CSG. The system consisted of a solar collector, a heat storage device and a circulation pump. The solar collector was facing south and fixed on the north wall inside the CSG. During daytime, the absorbed solar energy from the system was transferred to the water by the circulation pump. At night, when the greenhouse air temperature dropped below 10°C the system then transferred the low temperature heat from the water to the greenhouse air. The results showed that the average nighttime air temperature in the CSG was 4.6 and 4.5°C higher than that in the reference CSG on cloudy and sunny days, respectively. When the outside air temperature was -12.5°C, the air temperature inside the normal greenhouse was just 5.4°C, while that in the experiment greenhouse was 10.1°C. The average efficiency of the heat storage-release system reached 42.3% and 57.7% on cloudy and sunny days, respectively. Compared with electricity heating equipment, the experiment achieved 51.1% energy savings. The results indicate that the heat storage-release curtain is an effective method to increase the nighttime air temperature in the Chinese Solar Greenhouse.


Fang H.,Chinese Academy of Agricultural Sciences | Fang H.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Zhang Y.,Chinese Academy of Agricultural Sciences | Zhang Y.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 8 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

The Chinese Solar Greenhouse (CSG) that is widely used in North China is characterized by a lean-to south-facing roof, a removable insulating blanket and a solid north wall. The south facing roof structure and removable insulating blanket maximize the exposure to short-wave radiation during the day and minimize heat loss at night, respectively. To increase the year-round greenhouse production in North China, a sustainable heating method needs to be developed to increase the night air temperature during the winter in CSGs. Solar heating is an inexpensive and effective way to heat greenhouses, and has been investigated by several previous studies. For the present study, a heat storage-release metal film system that was attached to the north wall was developed for CSG night temperature improvement. Two experimental greenhouses were located in Beijing, China, with a floor area of 304 m2 each. Environmental parameters (temperature, humidity, heat flux) inside and outside the greenhouse were investigated, including the average solar collection efficiency of the heating system and the energy saving rates. The results showed that the average solar collection efficiency of the system was 83%, 1.6 times greater than the reported value of a heat storage-release metal film system installed in a small CSG. The energy collection efficiency during the daytime decreased sharply with declining plate-air temperature differences. To have high energy collection efficiencies, plate-air temperature differences must be kept high and this can be achieved by applying a heat pump to reduce the circulating water temperature and transfer the energy to another water tank. The effective collector absorptivity was 0.81 and heat transfer was by natural convection. During the relatively cold nights of December 23 and 24 with the lowest outdoor air temperature of approximately-18℃, the inside air temperature of the experimental CSG also was 3.7℃ higher than in the reference CSG after starting operation of the heat storage-release metal film system. The night air temperature in the experimental CSG was increased by 2.4℃ on average compared to the reference CSG. The performance of the heat storage-release metal film system can be analyzed via the collected and released heat. The variations of the total heat collected and released by the heat storage-release metal film system during the day/night periods investigated were presented together with the radiation sum at the back wall over the total area of the heat storage-release metal film system. The system collected much more energy during sunny days than during cloudy days. The utilization ratio of the collected heat of the heat storage-release metal film system was calculated and it was between 64% and 71%. So the collected heat was not utilised completely during the night as some heat was lost during transport and storage. The heat collecting efficiency for these days was calculated as 86%, 82% and 82%, respectively which was nearly constant. So the use of the heat storage-release metal film system for heating the greenhouse at night during the winter can improve the environmental conditions inside Chinese solar greenhouses for crop production, achieving high energy collection efficiency and a reduction in energy consumption. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.


Li K.,Chinese Academy of Agricultural Sciences | Li K.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Yang Q.-C.,Chinese Academy of Agricultural Sciences | Yang Q.-C.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 4 more authors.
HortTechnology | Year: 2014

In this study, the effects of light-emitting diode (LED) panels with different illumination schedules and mounted above butterhead lettuce (Lactuca sativa var. capitata) seedlings on lettuce growth and photosynthesis were examined, and the performance of the vertical and horizontal movable system on energy savings was evaluated. The illumination schedules used were fixed LED [F-LED (four LED panels illuminated the area below)] and movable LED [M-LED (two LED panels moved left and right once per day to illuminate the same area as F-LED)] at distances of 10 and 30 cm above the seedlings. The plant yields were uniform in all LED treatments. The highest light utilization efficiencies and lowest electricity consumption were found for the treatments with irradiation from a shorter distance above the seedlings. The true leaf numbers and ascorbic acid concentrations were the highest in the M-LED and F-LED treatments at a distance above the seedlings of 10 cm, while the leaf lengths and sucrose concentrations in these groups were significantly lower than those in the 30-cm treatment. These results indicate that illumination with M-LED can halve the initial light source input while maintaining yield and that sustained illumination from a shorter distance above the seedlings is the main factor in electricity savings. © 2014, American Society for Horticultural Science. All rights reserved.


Zhou B.,Chinese Academy of Agricultural Sciences | Zhou B.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Zhang Y.,Chinese Academy of Agricultural Sciences | Zhang Y.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 5 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016

Traditional Chinese solar greenhouse has thick north wall and its structure is non-standard, in which crop yield is lower because of the lack of automatic equipment for controlling the inside temperature and humidity. In order to solve this problem, we designed a simply assembled Chinese solar greenhouse that was equipped with heating and dehumidification system. In this study we presented 2 simply assembled Chinese solar greenhouses with active heat storage-release systems as the experiment greenhouses. One of them was also equipped with dehumidification system. Each greenhouse was 33 m long and 8 m wide with 3.8 m ridge height, 3.2 m height and 0.166 m thickness of the north wall. The wall of simply assembled greenhouse was composed of 2 fiber cement boards and a polystyrene board in between. A traditional solar greenhouse with brick wall using active heat storage-release system was chosen to be a reference greenhouse. It was 60 m long and 8 m wide with 3.8 m ridge height, 2.3 m height and 0.58 m thickness of the north wall. Compared with the brick wall, simply assembled Chinese solar greenhouse could save 72% of land resources. Steel frames of the experiment greenhouse were assembled together. It saved much more time to build a simply assembled Chinese solar greenhouse. All greenhouse crops were tomatoes planted on October 20th, 2014. Active heat storage-release system and dehumidification system were active automatically at night during the experiment. Active heat storage-release system was a heat-energy storage and release system by using water as the medium. During the day time (from 09:00 to 16:00) this system was used to store solar energy. During the nighttime (from 00:00 to 08:00), it released the energy into greenhouse for increasing the indoor temperature. In the experiment the system increased the indoor temperature by 4.5 ℃ at night compared with the traditional solar greenhouse. And the average air temperature was 1.3℃ higher in the simply assembled Chinese solar greenhouse than that in the traditional solar greenhouse combined with active heat storage-release system, which was because of higher insulation of the wall material. On cloudy day, the active heat-release system also improved the indoor temperature by 1.1 ℃. The dehumidification system had an air duct on the floor along the south-facing roof that distributed the outside air from a ventilator installed in the system box. This box contained the water-to-air heat exchanger, and 2 electrical heaters. The cold, dry air outside was heated by warm water from the water tank through a heat exchanger. Heat energy got from the warm water was supplied by the active heat storage-release system. A manual valve was used to control the air speed and 2 automatic valves were used to control the inlet of outside air. The dehumidification system could be activated from 18:00 to 08:30 in the next morning. When the inside relative humidity was higher than 85%, water went through the heat exchanger while the ventilator was switched on. When the indoor air temperature would drop below 8 ℃, the dehumidification system would switch off for preventing further cooling of the greenhouse by the cold air outdoor. During dehumidifying process, the first electric heater would be switched on when the water temperature was below 25 ℃. The second would work when the water temperature was below 20℃. During the experiment, the dehumidification system reduced the indoor relative humidity by 14% compared with the traditional solar greenhouse. During the dehumidification process, the energy consumption of the water pump and ventilator was 218.3 kJ/m2 per day. The energy supplied by the electric heaters was 643.6 kJ/m2 per day assuming that the energy conversion efficiency was 100%. The heat energy supplied by the active heat storage-release system was 639.4 kJ/m2 and its consumption was 153.4 kJ/m2 per day on average. It was expected that the electric heaters could be eliminated if the active heat storage-release system could be scaled up to provide an additional heat energy of 643.6 kJ/m2 per day. For a commercial greenhouse, it was important to improve the performance of the active heat storage-release system to get more solar energy and reduce the additional energy input. A more energy-efficient way of auxiliary heating was necessary in case of continuous cloudy days. By the financial analyses, the cost of brick wall greenhouse was 491.7 yuan/m2, and the simply assembled greenhouse was 334.5 yuan/m2. The biggest difference was from the charge of north wall. In conclusion, the simply assembled greenhouse with heating and dehumidification equipment saves much land resource, and has better indoor environment and less cost. © 2016, Chinese Society of Agricultural Engineering. All right reserved.


Zhou S.,Chinese Academy of Agricultural Sciences | Zhou S.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Zhang Y.,Chinese Academy of Agricultural Sciences | Zhang Y.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 12 more authors.
Applied Engineering in Agriculture | Year: 2016

Chinese Solar Greenhouses (CSG) rely solely on solar radiation for heating to achieve energy savings. However their land utilization efficiency is only 30% to 48%. A new type of solar greenhouse was designed where an active heat storage-release system (AHS) was added to replace the north wall and the greenhouse ridge was north-south oriented. In this way, the spacing between greenhouses can be shortened and the land utilization efficiency can be increased up to 91%. To further improve the thermal performance of the new type of greenhouse, a heat pump (HP) was incorporated in the AHS system to form a new design defined as AHS-HP. The HP was used to regulate the water temperature in three storage tanks that served as the heat reservoir for the AHS system. By regulating the water temperatures, the heat collection and releasing can be done more efficiently than without HP. Two new types of greenhouses located in Beijing, one with AHS-HP (experimental greenhouse) and one without (reference greenhouse), were compared in terms of indoor air temperature, relative humidity (RH), and electricity consumption. Nighttime air temperature in the experimental greenhouse was increased from 2°C to 4.5°C, on average, compared with the reference greenhouse. The coefficient of performance (COP) of the HP was 4.8 to 6.3 during the daytime and 3.1 to 4.9 at night. The COP of the AHS-HP system was 3.2. The average daily electricity consumption of the AHS-HP is 0.04 kWh m-2 day-1. The low cost AHS-HP has the potential to be applied in solar greenhouses if it is properly designed and operated. © 2016 American Society of Agricultural and Biological Engineers.


Zhou B.,Chinese Academy of Agricultural Sciences | Zhou B.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Zhang Y.,Chinese Academy of Agricultural Sciences | Zhang Y.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 8 more authors.
Applied Engineering in Agriculture | Year: 2016

At nights during winter, Chinese solar greenhouses are heavily insulated with little ventilation and therefore suffer from high humidity. In this study we presented a dehumidification system that suits Chinese solar greenhouses. Dehumidification is achieved by introducing outside dry air into greenhouses after being heated. An active heat storagerelease (AHS) system provided part of the heating energy. During daytime, the AHS system stores the surplus solar energy in water and releases this energy at night to the incoming outside dry air through a water-air heat exchanger. The outdoor dry air was drawn in by a ventilator (blower) and distributed evenly across the greenhouse through a plastic duct. Electric heaters served as auxiliary heating when the AHS system could not meet the heat demand. Experiments were conducted in two Chinese solar greenhouses in Beijing. One of the greenhouses was equipped with the dehumidification system and the other was not. This study showed that the relative humidity in the greenhouse with the dehumidification system was maintained below 85% while air temperature was not significantly lower than the greenhouse without the dehumidification system. The dehumidification system can remove vapor at the level of 15g m-2 h-1 at an air exchange rate of 1 h-1. The power requirement to drive the dehumidification system was 4.2 W m-2. For commercial application, the capacity of the AHS system needs to be increased to eliminate the use of electric heaters. © 2016 American Society of Agricultural and Biological Engineers.


Zhang Y.,Chinese Academy of Agricultural Sciences | Zhang Y.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Yang Q.,Chinese Academy of Agricultural Sciences | Yang Q.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2012

In order to increasing air temperature at night in Chinese solar greenhouse which meet the need of crop growth, a water curtain system was designed to increase the air temperature in Chinese solar greenhouse at night. In this system north wall of Chinese solar greenhouse was regarded as a support, and water was used as media to store and release heat. In the day, when water circuited and passed water curtain, the solar radiation was absorbed in the system and stored the heat in a water tank simultaneously. At night, when water circuited and passed water curtain, the heat was released to the greenhouse and then the air temperature was increased in the Chinese solar greenhouse. The experiments had in last winter showed that the air temperature at night in greenhouse was increased by over 5.4°C and the soil temperature at crop rhizosphere was increased by over 1.6°C, the heat release from water curtain at night in this system was 4.9-5.6 MJ/m 2, the increasing of the thermal storage and heat release of water curtain system in greenhouse made the tomatoes safely grow in winter and the time that cherry tomatoes was came into the market was put ahead by 20 days. It is significant to structure improvement and temperature control in Chinese solar greenhouse.


Fang H.,Chinese Academy of Agricultural Sciences | Fang H.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Yang Q.,Chinese Academy of Agricultural Sciences | Yang Q.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 9 more authors.
Applied Engineering in Agriculture | Year: 2015

To increase the year-round greenhouse production in North China, a sustainable heating method should be developed to increase the night air temperature during the winter in Chinese Solar Greenhouses (CSGs). Solar heating is an inexpensive and effective way to heat greenhouses, and has been investigated by several previous studies. For the present study, a heat collection-heat release (HCHR) system that was attached to the north wall was developed for CSG night temperature improvement. Two experimental greenhouses were located in Beijing, China, with a floor area of 392 m2 each. Environmental parameters (temperature, humidity, heat flux) inside and outside the greenhouse were investigated, including the average solar collection efficiency of the heating system and the pump energy consumption rates. The results showed that the average solar collection efficiency of the system was 52%, which was 1.3 times greater than the reported value of a HCHR system installed in a small CSG. The effective collector absorptivity was 0.59 and heat transfer proved to be by natural convection. The night air temperature in the experimental CSG was increased by 5 ° C on average compared to the reference CSG. To meet the heating demand of the CSG during cold winter nights the release capacity must be increased by 40%. Pump capacity to circulate the water proved to be crucial for energy efficiency. © 2015 American Society of Agricultural and Biological Engineers.


Sun W.,Chinese Academy of Agricultural Sciences | Sun W.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | Yang Q.,Chinese Academy of Agricultural Sciences | Yang Q.,Key Laboratory of Energy Conservation and Waster Treatment of Agricultural Structures | And 7 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

The Chinese solar greenhouse has a unique greenhouse structure that regards solar energy as the main energy source, and has characteristics such as high efficiency, energy saving, and low cost. During a cold winter night, air temperature inside a solar greenhouse is low for crop growth, which would affect crop yield and quality, due to the heat-transfer characteristics and heat capacity limit of the north wall. In recent years, in trying to promote the heat storage capacity of the solar greenhouse, the thought of active heat storage-release came forward. Solar energy is a kind of clean renewable energy, but has intermittent and unstable performance when used for greenhouse heating. Meanwhile, the heat collecting efficiency of the solar thermal collector decreases with an increase in operating temperature. Thus, an active heat storage-release system (AHSRS) is difficult to use to ensure an appropriate temperature for a solar greenhouse in a frigid region or when it encounters weather conditions with weak solar radiation. As an efficient means of raising low-grade energy, the heat pump has been more and more applied to greenhouse heating which can reduce the operating temperature of the AHSRS when used in combination. In order to promote heating performance and stability of the AHSRS and improve air temperature inside a solar greenhouse at night, based on the concept of active heat storage-release, an active heat storage-release associated with heat pump heating system (AHSRHPS) applicable to solar greenhouse heating was designed in the present study. During the day, the solar energy reaching the north wall surface was absorbed by the circulating water and stored in reservoirs when the AHSRS was running. Running the heat pump unit was intended to promote low-grade heat energy and reduce the circulating water temperature which contributes to increasing the heat collecting efficiency of the AHSRS and maximum water temperature of the reservoir. When air temperature inside the solar greenhouse was low at night, the heat energy was released through the AHSRS. Tests for the AHSRHPS were carried on from 5 Dec. 2012 to 5 Feb. 2013. The results showed that when there was a sunny and cloudy day in winter, the air temperature inside the experimental greenhouse with the AHSRHPS was higher than that in comparative greenhouse both in the day and at night and the air temperature difference ranged from 5.26 to 6.64°C. In addition, the heating effect was more obvious when solar radiation was stronger during the day and the outdoor air temperature was lower at night. The coefficient of performance of the heat pump unit reached 4.38~5.17. The heat source temperature of the heat pump unit was ideal because of the sufficient heat supplied by the AHSRS and the outlet water temperature of the evaporator became the dominant factor influencing the COPHp of the heat pump unit, meanwhile, the COPHp value decreased with an increase in outlet water temperature of the evaporator. Under the specific thermal environment of the solar greenhouse, with running the heat pump unit for 1.5~3 hours per day, the heat collecting efficiency of the AHSRS increased to 72.32%~83.62%, and the heat collecting power was 156.26~258.05 W/m2. The COPSys of the overall system reached 5.59, and the energy-saving effect was obvious. Made from cheap materials, the active heat storage-release devices were much cheaper than traditional solar energy collectors. Compared with ground and water source heat pump units, the AHSRHPS doesn't need fan coil units or other heat dissipation facilities. Meanwhile, deep wells or buried pipes used as heat sources were never needed either. The high performance and low cost make AHSRHPS present a good application prospect.

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