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Greenhouse Heating and Cooling with a Heat Pump System using Surplus Air and Underground Water Thermal Energy *
Abstract
Energy saving is an important issue for greenhouse farming. Natural and sustainable energy sources are critical to energy conservation. In this study, greenhouse heating and cooling technology was developed using a heat pump system that used surplus air thermal energy (SATE) and underground water thermal energy (UWTE) as heat sources. The greenhouse system was operated during February and March 2012. The SATE and UWTE system was successfully utilized for heating. Temperature control between desired set-points was also achieved. The heat pump system performed at average COP of 3.25 and 2.84 in February and March, respectively. In conclusion, greenhouse energy conservation was achieved by utilizing SATE and UWTE.
... Using a different heat pumps system in greenhouse enables large energy savings for heating and cooling. Yang at al. [18] investigated heat pump system that used surplus air thermal energy and underground water thermal energy as heat sources for greenhouse. Significant energy saving was achieved by using two of this type of heat pump. ...
Greenhouses have significant importance in the field of agriculture and horticulture. A special type of greenhouse is solar greenhouse, which is designed to collect solar energy during sunny days and to store heat for use at night or during periods without the Sun. In this paper it is investigated a solar greenhouse with photovoltaic panels. For greenhouse heating in the winter period and cooling in the summer period, a ground source heat pump was used. Solar greenhouse is simulated in EnergyPlus environment, while Open Studio plug-in in Google SketchUp was used for greenhouse design. Energy analysis was performed with the major aim to minimize greenhouse energy consumption, and to achieve solar greenhouse with net-zero energy consumption. Cases of different solar greenhouse orientations, different photovoltaic slope and different photovoltaic cell efficiency were considered. The simulation results showed that total energy consumption for heating and cooling of the greenhouse can be significantly reduced by using the optimal parameters (orientation and photovoltaic slope angle). Also, by changing the photovoltaics area and by using photovoltaics with higher cell efficiency, a concept of net-zero energy solar greenhouses can be achieved.
... There are listed some studies, who investigated different heat pump systems for greenhouse heating. Seung et al. developed a ground-source heat pump to maintain the greenhouse internal setpoint temperature during winter and reported a 3.25 coefficient of performance (COP) of the heat pump in heating mode [13]. Kim et al. used thermal effluent from a power plant and applied it to a heat pump system to fulfil the heat energy requirement of the greenhouse. ...
This study proposes a building energy simulation (BES) model of an air-to-water heat pump (AWHP) system integrated with a multi-span greenhouse using the TRNSYS-18 program. The proposed BES model was validated using an experimental AWHP and a multi-span greenhouse installed in Kyungpook National University, Daegu, South Korea (latitude 35.53° N, longitude 128.36° E, elevation 48 m). Three AWHPs and a water storage tank were used to fulfill the heat energy requirement of the three-span greenhouse with 391.6 m 2 of floor area. The model was validated by comparing the following experimental and simulated results, namely, the internal greenhouse temperature, the heating load of the greenhouse, heat supply from the water storage tank to the greenhouse, heat pumps' output water temperature, power used by the heat pumps, coefficient of performance (COP) of the heat pump, and water storage tank temperature. The BES model's performance was evaluated by calculating the root mean square error (RMSE) and the Nash-Sutcliffe efficiency (NSE) coefficient of validation results. The overall results correlated well with the experimental and simulated results and encouraged adopting the BES model. The average calculated COP of the AWHP was 2.2 when the outside temperature was as low as −13 °C. The proposed model was designed simply, and detailed information of each step is provided to make it easy to use for engineers, researchers, and consultants.
... Yang and Rhee [45] evaluated a heat pump system using the excess thermal energy available inside the greenhouse (SATE) during winter period, and found that the energy conservation and the SATE amount are maximal in March. A heating and cooling system is developed by Yang et al. [46,47] using the SATE in a greenhouse which performed the recovery and supply of the heat according to design purposes. They pointed out that the greenhouse energy conservation was achieved by using SATE. ...
The solar thermal storage is an important issue for greenhouse applications in winter period. For the reason that greenhouse operations, such as heating and cooling, consume a large amount of energy. The thermal storage is important to minimize the cost of greenhouse production. Surplus air thermal energy (SATE) is available in greenhouses during all the year, even in the cold period, hence its use in greenhouse applications is possible. In this present work, a solar heating cooling system (SHCS) with quartzitic sandstone as thermal storage material to store and use the SATE in greenhouse production was operated for cooling and heating processes and its performance was evaluated during winter period. This system consists of a quartzitic sandstone and including thermal storage blocks and pipes with fans to manage those processes in greenhouse. This system was located in the Souss-Massa region, Morocco. The heating and cooling of inside air by SHCS can improve the greenhouse microclimate and tomato yield. The results show that the air temperature in greenhouse equipped with SHCS exceeds than that of the control one about 3 °C at night and 6 °C lower during day, with fewer fluctuations. Moreover, the relative humidity was 10% lower at night. The SATE stored was varied between 15.68 and 140 MJ/day in plastic greenhouse with an area of 165 m 2 during day, and 65% of this heat recovered at night. The SHCS was improved the tomato yield about 1.74 kg/m 2 than that of normal production. An economic analysis revealed that this system is very profitable and could generate profits for farmers.
... Another thought was presented [12][13][14], heat pump was used for the energy saving. Heat pump is a device that can transfer heat from low to high heat source. ...
Heating saving energy plays a very significant role in the energy saving industry. CANbus is a modern system in reliability improvement design concept which shows the transmission distance is longer than ordinary methods, and it can hang node on the optional position in availability distance. The nodes are linked in parallel, and not interfere with each other. By using the CANbus technology, the relay output module with a radiator, thermocouple acquisition module is linkedto the temperature sensor. The temperature sensor collects information from the outside system. Relay output module controls heating valve based on the temperature information, and make temperature of the room controlled automatically. Four energy-saving modes are developed in this project. Testing result reflects that the system designed under the new methodology offers outstanding results in energy-saving.
... Recently, there is a composite system; same system could be used for heating the greenhouses in winter and cooling them in summer [54,55]. Yang et al. [56] developed a heating and cooling system to utilize surplus air thermal energy (SATE) and underground water thermal energy (UWTE) as heat sources. The system consisted of a heat pump system including high and low temperature heat storage tanks, fan coil units (FCU) in the greenhouse, and an underground water source. ...
As an essential facility for crop growth, the greenhouse creates an indoor microclimate that affects not only the growth quality of vegetation, but also the energy consumption and carbon emission of agriculture. China's agriculture has long been restricted by the traditional nature-dependent mode and lacks an comprehensive theoretical brace for the design and reform of greenhouses. Based on the exothermic and endothermic principle of phase change materials (PCM(s)), this study mainly focuses on the implantation of PCM(s) layers into the envelopes of an actual greenhouse for passive heating. A dynamic simulation of the whole-day indoor temperature self-regulation performance of the greenhouse was performed, and the calculation model was verified. Results show that the embedding of PCM(s) layer in the envelope structure can cut down the high temperature (>30 °C) during daytime and release heat to indoor delayed at night for warming up around 1–2 °C. The north wall is the key component for laying PCM(s), and the critical thickness is the best thermal performance thickness for heating effect. This design solely relies on solar energy with zero carbon emission, and allows for winter passive heating.
PurposeA hybrid system combining a hydrothermal heat pump and pellet boiler was investigated as a potential heating system for a smart farm.MethodsA double-layer automatic side opening and closing system and an automatic ventilation system were installed in a greenhouse with an area of approximately 90 m2 located at Kangwon National University, Chuncheon, Gangwon-do, Republic of Korea. In the hybrid system, comprising a pellet boiler and hydrothermal heat pump, heat transfer was facilitated using a fan coil unit and tube rail. Thermocouples were installed in indoor and outdoor pipes for data acquisition. The fuel and power consumption of the boilers and pumps were measured daily. Eleven experiments were conducted between February and March 2020. Heating performance and energy consumption were analyzed for the different systems.ResultsComparative analysis revealed that the hybrid system showed the highest thermal efficiency at 64%. In terms of the energy cost per temperature lifting, the hybrid system reduced cost by ~23% compared with a single pellet boiler.Conclusions
Thus, the hybrid system can successfully be applied to smart farm heating and is efficient in terms of heating performance and energy costs.
Geothermal heat pump systems use the earth as a heat source in heating mode and a heat sink in cooling mode. These systems can be used for heating or cooling systems in farm facilities such as greenhouses for protected horticulture, cattle sheds, mushroom house, etc. A horizontal type means that a geothermal heat exchanger is laid in the trench buried in 1.2 to 1.8 m depth. Because a horizontal type has advantages of low installation, operation and maintenance costs compared to a vertical type, it is easy to be adopted to agriculture. In this study, to heat and cool farm facilities and obtain basic data for practical application of horizontal geothermal heat pump systems in agriculture, a horizontal geothermal heat pump system of 10 RT scale was installed in greenhouse. Heating performance of this system was estimated. The horizontal geothermal heat pump used in this study had heating COP of 4.57 at soil temperature of 14^{\circ}C for depth of 1.75m and heating COP of 3.75 at soil temperature of 7^{\circ}C for the same depth. The stratification of water temperature in heat tank appeared during the whole heat rejection period.
Purpose: Utilizing air thermal energy during over-heated time in the greenhouse is a necessary component to save greenhouse heating costs for nighttime. However, there is no practical way to implement the related principles. Methods: In this study, a heating and cooling system which utilizes the surplus air thermal energy in a greenhouse was developed. Available air thermal energy and heating load for this experimental glasshouse were estimated based on temperature conditions of the plant growth and weather data. Results: Estimated values were 400 MJ/day for maximum surplus air thermal energy and 340 MJ/day for maximum heating energy which were target values of the design as well. The system consists of a heat pump, fan-coil units and heat storage tanks which are divided into low and high temperature tanks. Moreover, a new control logic was developed for surplus air thermal energy utilization. Conclusions: This paper explains the details of conceptual design process of the system. Results of test operations showed that the developed system performed the recovery and supply of the thermal energy according to design purposes.
The use of renewable energy for greenhouse heating in winter and cold days, helps to save fossil fuels and conserve green farm environment on the one hand, and on the other hand, enhances the quality of agricultural products, reduces production costs and limits the release of greenhouse gases. In this study, a ground-source heat pump-phase change material (GSHP-PCM) latent heat storage system was developed to use natural energy, to the extent possible, for thermal environment control of the greenhouse. The coefficient of performance of the heat pump (COPHP), that of the overall system (COPsys) and the energy capacity of the PCM during the charge–discharge phases has been determined. Based upon the measurements made in the heating mode from 1 September 2005 till 30 April 2006 in Elazığ, Turkey, the average heating COPHP of the GSHP unit and the overall system COPsys were obtained to be in the range of 2.3–3.8 and 2–3.5, respectively. These results showed that the utilization of a GSHP-PCM system is a suitable approach for greenhouse heating in this district.
This study was carried out in order to reduce the amount of underground water which is used in the double layered single span plastic greenhouse for retaining heat. For this research, two plastic green houses of the double layered single span plastic greenhouse were installed. There was equipped of internal small tunnel for keeping warm air in the interior of the house. Then the internal small tunnel for keeping warm air was fitted with PVC duct of 50 cm in diameter filled with subsurface water. The surplus solar energy in the greenhouse was stored in the water in the PVC duct. Four FCUs (Fan Coil Unit), which has the capacity of 8,000 kcal per hour, were installed in the middle of the house, and a circulation motor in heat storage water tank was operated from 10:30 a.m. to 16:00 p.m. in order to circulate water between the water tank and the FCUs. Consequently about 5 degrees celsius could be maintained in the interior of the internal small tunnel for keeping warm air with the external temperature of lower than minus 5 degrees celsius. It appeared that the alteration of an internal temperature of the house was flexible depending on the sunlight during daytime. To prevent the water freezing, mixing antifreezing liquid in the water or operating FCU continuously was needed. Also, in order to use the surplus solar thermal energy on plastic green house of water curtain system efficiently, storing the surplus heat during daytime simultaneously finding a method of using water curtain systematic underground water happened to be important. As a result of this research, when the house`s interior temperature is below zero the operation of FCU appeared to be impossible. Considering the amount of water used in the house with water-curtain-heating system is 150~200 ton per day, using the system mentioned in this research showed that reducing the underground water more than 80% in order to maintain the internal temperature as the level of 5 degree celsius at the extreme temperature of minus 5 degrees celsius.
This research performed to analyze surplus solar energy, which is generated from a greenhouse during daytime, and to make the basic materials for designing thermal energy storage system for surplus solar energy. For this goal, it analyzed the surplus solar energy coming from two types of greenhouse. The results of this research are as per the below: In the case of 1-2W-type greenhouse, this research gave the same temperature and ventilation condition regardless of regions, but it was judged that the quantity of surplus solar energy could be greatly changed, depending on the energy consumed for the photosynthesis and evapotranspiration of crops in the greenhouse, on the heating temperature during daytime and night, on the existence/non-existence of a curtain and its warming effect, and on the ventilation temperature suitable for the overcoming of high temperature troubles or for the optimum cultivation temperature. In the case of a single-span greenhouse, there was a big difference in energy incoming and outgoing by month, but throughout seasons, 85.0 % of the total energy put into the greenhouse was solar energy and the energy input by heating was just 15.0 % of the total. 26.4 % of the total energy input for the greenhouse was used for photosynthesis and evapotranspiration of crops, and 44.2 % of the remaining 73.6 % went out in the form of radiant heat through the surface of the greenhouse. That is, 25.2 % of the total energy loss was just the surplus solar energy. 67.6 % of the total heating energy was concentrically used for 3 months from December to February next year, but the surplus solar energy during the same period was just 19.4 % of the total annual quantity so it was found that the given condition was more restrictive in directly converting the surplus heat into greenhouse heating. Under the disadvantageous circumstance of 3 months from December to February next year, it was possible to supplement 28 % (December) 85 % (February) of heating energy with surplus solar energy.
In this paper, we report on an underground water-source water-loop heat-pump (UWSWLHP) air-conditioning system for a tall apartment building in Beijing. Water at 14 °C was used as an external low-temperature heat-source. By analyzing field-test data for two years, the authors assessed the operating and controlling conditions of the system. Based on the electricity consumed by public-use air-conditioning power equipment and terminal heat-pumps, the authors put forward an overall evaluation of the energy-conservation characteristics of the system.