Development and Validation of Air-to-Water Heat Pump Model for Greenhouse Heating
Abstract
:1. Introduction
2. Materials and Methods
2.1. Experimental Greenhouse
2.2. AWHP
2.3. BES Modeling and Simulation
2.4. Statistical Analysis of BES Model
3. Results and Discussion
4. Conclusions
- The RMSE values for the internal greenhouse air temperatures were 1.9, 1.8, and 2.0 °C, indicating the maximum temperature difference between the predicted and experimental results. The NSE values were 0.71, 0.70, and 0.65, respectively.
- The RMSE values of the energy load results for greenhouse compartments 1, 2, and 3 were 5140, 3674, and 5141 Kcal·h−1, respectively, and the NSE values of greenhouse compartments 1, 2, and 3 were, 0.73, 0.81, and 0.67, respectively.
- The validation results of the energy supplied from the water storage tank to the greenhouse showed an RMSE value of 20 Kcal·h−1·m−2 and an NSE value of 0.70.
- The heat pump output water temperature validation results showed an RMSE of 0.4 °C, and the COP of the heat pump was 2.2.
- The validation results for the water storage tank temperature show an RMSE value of 0.5 °C.
- The maximum heating energy demand for the studied greenhouse was found to be 250 kcal·h−1·m−2.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Appendix A
25 | 30 | 35 | 40 | 45 | 50 | T_water_in |
---|---|---|---|---|---|---|
2.2 | 7.2 | 12.2 | 15 | 20 | T_air_in | |
0.759 | 0.787 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 25 | |||
1.08 | 0.868 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 25 | |||
1.137 | 0.843 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 25 | |||
1.233 | 0.843 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 25 | |||
1.403 | 0.844 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 25 | |||
0.737 | 0.86 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 30 | |||
1.048 | 0.938 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 30 | |||
1.106 | 0.923 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 30 | |||
1.199 | 0.924 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 30 | |||
1.359 | 0.924 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 30 | |||
0.714 | 0.944 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 35 | |||
1.017 | 1.044 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 35 | |||
1.075 | 1.016 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 35 | |||
1.165 | 1.017 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 35 | |||
1.314 | 1.018 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 35 | |||
0.692 | 1.027 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 40 | |||
0.986 | 1.136 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 40 | |||
1.043 | 1.108 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 40 | |||
1.131 | 1.109 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 40 | |||
1.269 | 1.112 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 40 | |||
0.67 | 1.132 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 45 | |||
0.955 | 1.255 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 45 | |||
1.012 | 1.224 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 45 | |||
1.097 | 1.226 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 45 | |||
1.224 | 1.229 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 45 | |||
0.648 | 1.249 | !Fraction capacity and power at T_air = 2.2 | deg. C and T_water_in = 50 | |||
0.923 | 1.385 | !Fraction capacity and power at T_air = 7.2 | deg. C and T_water_in = 50 | |||
0.981 | 1.352 | !Fraction capacity and power at T_air = 12.2 | deg. C and T_water_in = 50 | |||
1.062 | 1.355 | !Fraction capacity and power at T_air = 15 | deg. C and T_water_in = 50 | |||
1.18 | 1.359 | !Fraction capacity and power at T_air = 20 | deg. C and T_water_in = 50 |
Hot Water Outlet Temperature | Ambient Temperature °C | |||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
−10 | −6 | −2 | 2 | 7 | 10 | 13 | ||||||||
Capacity | Power | Capacity | Power | Capacity | Power | Capacity | Power | Capacity | Power | Capacity | Power | Capacity | Power | |
°C | kW | kW | kW | kW | kW | kW | kW | kW | kW | kW | kW | kW | kW | kW |
40 | 43.51 | 13.70 | 54.39 | 15.57 | 63.98 | 17.30 | 71.09 | 18.81 | 77.28 | 19.80 | 86.55 | 20.98 | 99.53 | 22.66 |
41 | 42.05 | 13.98 | 52.63 | 15.89 | 61.98 | 17.65 | 68.95 | 19.19 | 75.03 | 20.20 | 83.88 | 21.41 | 96.29 | 23.12 |
42 | 40.83 | 14.27 | 51.17 | 16.21 | 60.34 | 18.01 | 67.19 | 19.58 | 73.20 | 20.61 | 81.69 | 21.85 | 93.61 | 23.60 |
43 | 39.85 | 14.56 | 50.0 | 16.54 | 59.03 | 18.38 | 65.80 | 19.98 | 71.76 | 21.03 | 79.94 | 22.29 | 91.45 | 24.08 |
44 | 39.08 | 14.86 | 49.09 | 16.88 | 58.03 | 18.76 | 64.76 | 20.39 | 70.70 | 21.46 | 78.62 | 22.75 | 89.78 | 24.57 |
45 | 38.51 | 15.16 | 48.44 | 17.23 | 57.32 | 19.14 | 64.05 | 20.81 | 70.00 | 21.90 | 77.70 | 23.21 | 88.58 | 25.07 |
46 | 37.76 | 15.31 | 47.55 | 17.40 | 56.34 | 19.33 | 63.02 | 21.01 | 68.95 | 22.12 | 76.40 | 23.45 | 86.94 | 25.32 |
47 | 36.64 | 15.62 | 46.20 | 17.75 | 54.81 | 19.72 | 31.38 | 21.43 | 67.23 | 22.56 | 74.35 | 23.92 | 84.46 | 25.83 |
48 | 35.19 | 16.09 | 44.44 | 18.28 | 52.77 | 20.31 | 59.16 | 22.08 | 64.87 | 23.24 | 71.62 | 24.63 | 81.22 | 26.60 |
49 | 33.28 | 16.73 | 42.07 | 19.01 | 50.02 | 21.12 | 56.14 | 22.96 | 61.63 | 24.17 | 67.92 | 25.62 | 76.88 | 27.67 |
50 | 31.14 | 17.57 | 39.41 | 19.96 | 46.92 | 22.18 | 52.72 | 24.11 | 57.93 | 25.38 | 63.73 | 26.90 | 72.01 | 29.05 |
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Weather Parameter | Unit | Time Interval | Sensor | Accuracy of Sensors |
---|---|---|---|---|
Air temperature | ℃ | 10 min | MTV Active, Ridder | ±1% |
Relative humidity | % | 10 min | MTV Active, Ridder | ±2% |
Solar radiation | W·m−2 | 10 min | SR05-D2A2-TMBL, Hukseflux | IEC 61724-1:2017 standard, Class C, Basic |
Wind speed | m·s−1 | 10 min | Clima Sensor US, Thies Clima | ±5% |
Wind direction | degrees | 10 min | Clima Sensor US, Thies Clima | ±5% of measured value |
Water temperature | ℃ | 10 min | HortiMax Omni, Ridder | ±0.5% |
Water flow rate | Liter | 10 min | FS-WLH 40, FLSTRONIC | ±1% of measured value |
Ambient pressure | hPa | 10 min | PTB-220TS, VAISALA | ±5% hPa |
Component | Properties | Specification |
---|---|---|
Heat pump | Model | PSET-C60W (MIDEA) |
Heating capacity | 70 kW | |
Power consumption | 21.9 | |
Voltage | 380 V–415 V, 3-phase, 60 Hz | |
Refrigerant | R-410a | |
Heat storage tank | Heat storage fluid | Water |
Capacity | 50 m3 | |
Water circulation pump | Model | Wilo TOP-S 40/7 |
Max. fluid temperature | 130 °C | |
Max. fluid temperature | −20 °C | |
Power consumption | 390 W | |
Fan coil unit | Model | IN-FCG0016-L |
Heating capacity | 27,000 W | |
Airflow rate | 83 m3·m−1 |
Component | Type | Description |
---|---|---|
Data reader | 9 | Reads the user-defined weather data file |
Solar radiation processor | 16 | Uses total direct solar radiation on the horizontal surface as an input and calculates the total, beam, reflected, and diffuse radiation on all greenhouse tilt surfaces |
Sky temperature calculator | 69 | Input: dewpoint temperature, beam, and diffuse radiation on horizontal surface to calculate sky temperature |
Psychrometric chart | 33 | Calculates dewpoint temperature using dry bulk temperature and humidity ratio |
Equation editor | Inserts equation in the model | |
Greenhouse building model | 56-TRNFlow | Uses TRNBuild and processes the thermal behavior of the greenhouse along with the natural ventilation |
Air-to-water heat pump (AWHP) | 941 | This model is based on user-supplied data files containing catalog data for water capacity and power. It takes air-relative humidity and outside temperature as an input |
Water storage tank | 4 | Water storage tank |
Pipe | 709 | Models the fluid flow into the pipe; calculates the heat loss from the pipe |
Fan coil unit | 928 | Takes hot water as an input and provides hot air to the greenhouse for temperature control |
Pump | 3 | Variable-speed water circulation pump |
Pump | 114 | Constant-speed water circulation pump |
Valve | 649 | Water-mixing valve, which combines different liquid streams into a single output mass flow. Combines the output water of three heat pumps and delivers water to the storage tank |
Thermostat | 108 | A five-stage thermostat for the on/off control function. Controls the circulation pump and fan coil unit for the greenhouse’s internal temperature setpoint |
Controller | 165 | Controls the natural ventilation of the greenhouse |
Monthly forcing function | 518 | Inputs schedules and screen opening and closing times that change monthly |
Printer | 25 | Prints results on user-provided external files |
Plotter | 65 | This type was used to plot the results. |
Cover Characteristics | Covering | Screens | ||
---|---|---|---|---|
HG | PC | PH_66 | Luxous | |
Solar transmittance front | 0.89 | 0.78 | 0.38 | 0.58 |
Solar transmittance back | 0.89 | 0.78 | 0.38 | 0.57 |
Solar reflectance front | 0.08 | 0.14 | 0.50 | 0.30 |
Solar reflectance back | 0.08 | 0.14 | 0.48 | 0.25 |
Visible radiation transmittance front | 0.91 | 0.75 | 0.38 | 0.58 |
Visible radiation transmittance back | 0.91 | 0.75 | 0.38 | 0.57 |
Visible radiation reflectance front | 0.08 | 0.15 | 0.50 | 0.30 |
Visible radiation reflectance back | 0.08 | 0.15 | 0.48 | 0.25 |
Thermal radiation transmittance | 0.1 | 0.02 | 0.35 | 0.26 |
Thermal radiation emission front | 0.90 | 0.89 | 0.48 | 0.45 |
Thermal radiation emission back | 0.90 | 0.89 | 0.55 | 0.42 |
Conductivity (W·m−1·K−1) | 0.1 | 0.19 | 0.06 | 0.05 |
Air permeability (m2) | — | — | 1.49 × 10−11 | 1.33 × 10−11 |
Thickness (mm) | 4 | 16 | 0.24 | 0.25 |
Material | Thickness (m) | Thermal Conductivity (kJ·h−1·m−1·K−1) | Thermal Capacity (kJ·kg−1·K−1) | Density (kJ·m−3) | Convective Heat Transfer Coefficient (kJ·h−1·m−2·K−1) | |
---|---|---|---|---|---|---|
Front | Back | |||||
Steel | 0.04 | 54 | 1.8 | 7800 | 11 | 64 |
Ground | 0.100 | 0.97 | 0.75 | 2900 | 11 | 0.001 |
Parameter | Operating Condition |
---|---|
Greenhouse type | Multi-span |
Roof type | Venlo |
No. of spans | 3 |
Roof glazing | HG, 4 mm |
Side glazing | PC, 16 mm |
GH portion dividing glazing | HG, 4 mm |
Orientation | North–South |
Dimension | 20.6 m × 16.3 m × 7.6 m |
Floor area | 391.2 m2 |
Volume | 2362.8 m3 |
Period | 1 January 2021 to 28 February 2021 |
Natural ventilation | roof vents |
Natural vents control set point temp | 26 °C |
Energy screen position | Roof only |
Energy screens (1 and 2) | PH-66, Luxous |
Thermal screens’ control | Ph-66 retract (After sunrise, OR S.R 100 W) Ph-66 Deploy (After sunset, AND S.R 100 W) Luxous_1 retract (After sunrise, OR S.R 150 W) Luxous_1 deploy (After sunset, AND S.R 150 W) |
Heating setpoints, GH portion (1, 2, 3) | 16, 18, and 17 ℃ |
Lowest Outside Air Temp (℃) | Greenhouse Setpoint Temp (℃) | Greenhouse Heating Area (m2) | Max. Heating Load (kcal·h−1) | Max. Heating Load per Unit Area (kcal·h−1·m−2) |
---|---|---|---|---|
−13 | 18 | 391.2 | 97,800 | 250 |
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Rasheed, A.; Na, W.H.; Lee, J.W.; Kim, H.T.; Lee, H.W. Development and Validation of Air-to-Water Heat Pump Model for Greenhouse Heating. Energies 2021, 14, 4714. https://doi.org/10.3390/en14154714
Rasheed A, Na WH, Lee JW, Kim HT, Lee HW. Development and Validation of Air-to-Water Heat Pump Model for Greenhouse Heating. Energies. 2021; 14(15):4714. https://doi.org/10.3390/en14154714
Chicago/Turabian StyleRasheed, Adnan, Wook Ho Na, Jong Won Lee, Hyeon Tae Kim, and Hyun Woo Lee. 2021. "Development and Validation of Air-to-Water Heat Pump Model for Greenhouse Heating" Energies 14, no. 15: 4714. https://doi.org/10.3390/en14154714