CA2358337A1 - Greenhouse climate control system - Google Patents
Greenhouse climate control system Download PDFInfo
- Publication number
- CA2358337A1 CA2358337A1 CA002358337A CA2358337A CA2358337A1 CA 2358337 A1 CA2358337 A1 CA 2358337A1 CA 002358337 A CA002358337 A CA 002358337A CA 2358337 A CA2358337 A CA 2358337A CA 2358337 A1 CA2358337 A1 CA 2358337A1
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- Prior art keywords
- air
- greenhouse
- processing unit
- coils
- water
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
- A01G9/00—Cultivation in receptacles, forcing-frames or greenhouses; Edging for beds, lawn or the like
- A01G9/18—Greenhouses for treating plants with carbon dioxide or the like
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01G—HORTICULTURE; CULTIVATION OF VEGETABLES, FLOWERS, RICE, FRUIT, VINES, HOPS OR SEAWEED; FORESTRY; WATERING
- A01G9/00—Cultivation in receptacles, forcing-frames or greenhouses; Edging for beds, lawn or the like
- A01G9/24—Devices or systems for heating, ventilating, regulating temperature, illuminating, or watering, in greenhouses, forcing-frames, or the like
- A01G9/246—Air-conditioning systems
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/25—Greenhouse technology, e.g. cooling systems therefor
Abstract
The invention relates to air processing unit for a greenhouse that compries a main body having a greenhouse return air inlet, a greenhouse supply air outlet, and an airflow path between the inlet and outlet. Inside the main body in the air flow path are: an air temperature modifier, an air humidity modifier, and a CO2 injector. The greenhouse return air fed into the air processing unit is processed to modify one or more of its temperature, relative humidity, or CO2 content before being discharged from the air processing unit as supply air back into the greenhouse.
Description
Matter no.: V80012CA
Filename: 28452 v1 Greenhouse Climate Control System FIELD OF THE INVENTION
The invention relates generally to a climate control system for a greenhouse.
BACKGROUND OF THE INVENTION
A greenhouse is an enclosure for cultivating and protecting plants inside the greenhouse from the outside environment. Greenhouses are designed to control the balance oftemperature, moisture, COZcontent, and light to suit the growth requirements for plants, and particularly, for tender plants or plants grown out of season.
The temperature conditions inside the greenhouse will depend on the type of plant grown in the greenhouse. Some plants require substantially the same temperature to be maintained 24 hours a day, while other plants will require very specific temperature changes at different times of the day. The temperature outside the greenhouse of course affects the temperature inside. Further, solar radiation during a sunny day can heat the greenhouse, dramatically increasing the inside temperature.
Typical energy sources used to heat greenhouses include natural gas, propane, wood, coal, solar radiation, and electricity. Some of the energy sources can be used directly to heat the greenhouse, wherein others such as propane or natural gas are burned in a gas-fired boiler to heat water. The heated water is distributed through heat-conductive pipes that typically are located near the plants to be heated. The heat radiated by these pipes is typically distributed around the greenhouse by a series of fans that are used to circulate air.
Cooling the greenhouse may be achieved via a number of ways. For example, wall and roof vents may be provided that are opened to allow outside ambient air inside the greenhouse and inside hot air to escape. Fans may be provided to assist in this air Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 exchange. Roof vents in particular can be configured to open small or large portions of the roof. A shading system may be provided on the roof and walls that during the day block incoming solar radiation from entering the greenhouse. The shading system may also serve as thermal barriers, and as such be used at night to reduce heat loss out of the greenhouse when the outside is cooler than the inside. Typical shades are made of a porous fabric that allow for some limited air flow through the fabric. Other cooling systems include fog systems that include high pressure pumps that are used to distribute a fine mist of high pressure water (often in excess of 1000psi) via a plurality of very small nozzles. The water molecules tend to absorb some of the heat inside the greenhouse, but will fall to the ground and increase relative humidity (RH).
Therefore, fog systems are best used for temporary cooling.
Another important consideration for greenhouse design is the control of humidity within the greenhouse. The relative humidity inside a greenhouse usually builds up during the night while the plants are transpiring, and by evaporation of any liquid water that is left on the floor during the day from irrigation cycles, fog cooling, etc. Overly high RH will prevent a plant from cooling itself adequately, while an overly low RH
will cause the plant to dry out. Therefore, precise control of the RH in a greenhouse is important to prevent the plants within from suffering.
Typically, greenhouse operators vent the greenhouse early in the morning, e.g.
by opening roof vents, to reduce the RH that has built up inside the greenhouse over the night. Also, exhaust fans typically used for cooling can be turned on to increase the air exchange rate into and out of the greenhouse. When internal RH is lower than desired, systems typically used for cooling can be activated to increase the RH, e.g.
by turning on the fog mist system and/or pad cooling system, provided that appropriate conditions exist for such operation. Many of these known humidity controlling techniques require the exchange of outside and inside air; if the RH or the temperature of the outside air is not at an appropriate level, then such techniques are less effective, or even dangerous to the health of the plant. For example, venting moisture from a greenhouse on a cold damp day may not appreciably reduce the RH inside the greenhouse, may cause a dramatic temperature change-related shock to the plants, Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 2 -and may increase operating costs by requiring additional heat to be supplied to warm the greenhouse back to its pre-venting temperature.
Other factors that are considered in greenhouse design include plant irrigation and carbon dioxide supply. It has been long recognized that elevated levels of enhances crop growth, and as such, growers try to maintain C02 levels at higher than ambient conditions inside the greenhouse. Typically, C02 introduced into the greenhouses is produced by one or more of open air natural gas or propane burners, flue gas recovery systems, or supplied from liquid C02 tanks. If C02 is introduced via a combustion process, unwanted water, carbon monoxide and nitrous oxides are typically also introduced with the C02 into the greenhouse. C02 is typically introduced into the greenhouse during the day. Unfortunately, other climate control techniques used during the day compromise the effectiveness of COZ injection. For example, periodic venting of moisture from the greenhouse tends to also vent a substantial amount of the injected CO2.
Various factors must be controlled to maintain an ideal environment for plant growth. The traditional methods and systems for controlling one factor are often not compatible with controlling another factor, and thereby results in high operating costs and reduced plant growth. A typical day and night cycle illustrates the difficulty of controlling such factors. During the night, plants give off moisture and C02.
By the end of the night, the RH and C02 will tend to be relatively high. As the sun rises, and the plants awaken to their day cycle, they requires moisture which is provided to them by the greenhouse irrigation system, which further raises the RH inside the greenhouse.
The RH must be reduced quickly to avoid damaging the plants. Air exchange methods are thus undertaken to replace the RH-heavy greenhouse airwith lower RH
outside air.
As the internal air is discharged, accumulated COZthat would be usefully used during the day is also flushed out of the greenhouse. The vents are often left open for extended periods to cool and reduce the moisture content inside the greenhouse, forcing the operator to pump a relatively high amount of COZ into the greenhouse to compensate for the amounts lost by venting. As the sun falls and evening sets in, venting may also occur to lower the RH prior to nightfall. Such venting often prevents Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 3 the use of the greenhouse's shading system that would normally be used for heat retention. Heaters must therefore be run at a relatively high level to compensate for the heat lost by venting.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided an air processing unit for a greenhouse comprising a main body having a greenhouse return air inlet, a greenhouse supply air outlet, and an air flow path between the inlet and outlet. Further, inside the main body in the air flow path there is: an air temperature modifier, an air humidity modifier; and a COZ injector. Greenhouse return air fed into the air processing unit is processed to modify one or more of its temperature, relative humidity, or C02 content before being discharged from the air processing unit as supply air back into the greenhouse.
The air temperature modifier may comprise an air cooler and an air heater, and the humidity modifier may comprise a dehumidifier and a humidifier. The dehumidifier and cooler may comprise dehumidification and cooling coils that flow cooling fluid therethrough so that heat in the air path passing by the coils is transferred to the cooling fluid, and moisture in the air path is condensed inside the unit. The humidifier may comprise at least one water jet for spraying a mist of water into the air path. The heater may comprise primary heating heat exchanger coils that flow hot water therethrough so that heat is radiated from the hot water and into the air stream.
The air processing unit may further comprise reheating heat exchanger coils that are fluidly connected to the dehumidification and cooling coils, such that return cooling fluid from the dehumidification and cooling coils is flowable through the reheating heat exchanger coils to transfer some of the heat extracted during cooling and dehumidification back into the air stream.
According to another aspect of the invention, a climate control system for a greenhouse is provided that comprises the air processing unit as described above, a Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 4 -greenhouse return air collector inside the greenhouse, a return air duct fluidly connected to the return air collector and the inlet of the processing unit; a greenhouse supply air distributor inside the greenhouse, and, a supply air duct fluidly connected to the supply air distributor and outlet of the processing unit.
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Distribution tubes may be provided that are fluidly connected to the supply air distributor and mounted to the floor of the greenhouse, and have a plurality of spaced openings for discharging supply air into the greenhouse.
The climate control system may further comprise temperature, humidity and carbon dioxide sensors mounted inside the greenhouse. The climate control system may further comprise a control unit communicatively linked to the temperature, humidity and carbon dioxide sensors, and the processing unit. The computer system has stored therein at least one reference plant climate profile; the control unit is configured to 1$ measure the temperature, humidity and carbon dioxide levels inside the greenhouse, compare the measured levels against the reference plant climate profile, and adjust the settings of the processing unit to modify the greenhouse air to conform to the reference plant climate profile.
The climate control system may further comprise a boiler and a main radiant heating water loop fluidly connected to the boiler, and wherein the primary heating coils are fluidly connected to the main radiant heating water loop. A floor heating system may_also be fluidly connected to the main radiant heating water loop. The floor heating system may comprise a heat exchanger thermally connected to the floor heating system 2$ and to a cooling fluid return conduit connected to the processing unit, such that some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the floor heating system.
The climate control system may further comprise an irrigation heating system that is fluidly connected to the main radiant heating water loop. The irrigation heating system may comprise a heat exchanger thermally connected to the irrigation heating system and to a cooling fluid return conduit connected to the processing unit, such that Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - $ -some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the irrigation heating system.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic perspective view of an air processing unit of a greenhouse climate control system according to an embodiment of the invention;
Figure 2 is a schematic top view of the processing unit of Figure 1;
Figure 3 is a schematic perspective view of a greenhouse incorporating the climate control system;
Figure 4 a schematic top view of a greenhouse supply air distribution array of the greenhouse climate control system;
Figure 5 is a schematic piping diagram of an another embodiment of the greenhouse climate control system; and, Figure 6 is schematic piping diagram of yet another embodiment of the greenhouse climate control system.
DETAILED DESCRIPTION
Referring to Figures 1 and 2 and according to one embodiment of the invention, there is provided a greenhouse climate control system 10 for controlling the temperature, relative humidity (RN) and COZ levels in a greenhouse. The system has an air processing unit 12 that receives return air from the greenhouse via a return air duct 14 connected to an inlet 16 of the unit 12. The unit 12 discharges processed supply air back to the greenhouse via a supply air duct 18 connected to an outlet 20 of the unit 12. The unit 12 is preferably fluidly sealed to prevent or at least significantly impede air from escaping from the unit 12.
Inside the unit 12 are a number of components for processing the greenhouse air, including primary dehumidication and cooling coils 22, airfilters 24, re-heat coils 26, heating coils 28, a COZ injector 30, a humidifier 32, and a fan 38. All of these Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 6 -components are arranged in-line with the air flow so that air passing through the unit 12 will encounter each of these components in sequential downstream order.
Return air from the greenhouse is typically warm and saturated with water. The air entering the unit 12 first passes by air filters 24 to remove any unwanted particulates that may damage the unit 12, as well as to provide cleaner air back into the greenhouse. The filters 24 per se are of a conventional design and may be for example, disposable fibre filters commonly used in the HVAC industry.
Having passed through the filters 24, the air then passes by the primary dehumidification and cooling coils (PDC coils) 22. The PDC coils 22 are made from thin copper tubing and have an inlet and an outlet for the inflow and outflow of a cooling fluid, such as water, or a suitable refrigerant fluid. The coil pattern can be based on one of many known heat exchanger coil designs in the refrigeration industry. The PDC coils 22 are preferably made of copper but may be made with any material having a suitably high degree of thermal conductivity. In a system using cooling water as the cooling fluid, cooling water is pumped through the PDC coils 22 from a cold water source via cooling water conduit 40 connected to the inlet of the PDC coils 22. As warm greenhouse return air passes by the PDC coils 22, heat will be transferred from the air to the cooling water, thereby lowering the temperature of the air and raising the temperature of the cooling water. As the air cools, its RH will reach 100% and the air will reach its dew point and will not be able to hold any more water; as the air is cooled further, some of the water vapour will condense inside the unit 12 and particularly on the PDC coil 22. This condensed water is drained from the unit 12 through a drain (not shown) at the bottom of the unit 12. The recovered water can then be stored for reuse by other systems, such as the irrigation and fog systems.
The cooling water warmed during the cooling and dehumidification of the greenhouse air can be immediately removed from the unit 12 for discharge via a cooling water return conduit 42 connected to the outlet of the PDC coils 22, or can be directed through the reheat coils 26 to return some of the heat back to the greenhouse air stream, before being removed from the unit 12. The removed heat can be stored in a heat sink (not shown) such as a pond or an irrigation storage tank, such that the heat can be usefully used later. The path of the cooling water is controlled by a diversion Leeb % ::ODMA\PCDOCS\VAN LAW\28451\1 - 7 valve 44. If the greenhouse requires cooling, then the diversion valve 44 is set to bypass the re-heat coils 26 and to direct the water immediately to the return conduit 42 for removal from the unit 12. If however, the temperature of the greenhouse is at or about nominal levels, or requires heating (e.g. at night, or during the winter), the diversion valve 44 can be set to direct water through the reheat coils 26 to return some of the heat back to the greenhouse air. The re-heat coils 26 are a heat exchanger having a construction similar to the PDC coils 22, and in particular has an outlet that is fluidly connected to the return conduit 42.
The heating coils 28 are a heat exchanger and are constructed similarly to the PDC coils 22 and the reheat coils 26. Heated water is transmittable through the heating coil 28 via a heated water inflow conduit 46 fluidly connected to an inlet of the heating coil 28, and a heated water return conduit 48 fluidly connected to an outlet of the heating coil 28. On occasions requiring heating of the greenhouse air, the heating coil 28 is activated by flowing hot water through the heating coil 28 so that heat from the heating water can be transferred to the greenhouse air stream.
COZ can be introduced into the air stream by one or more COZ injectors 30 located downstream of the heating coil 28. The C02 injectors 30 have an injection port 36 which is fluidly connected to a COZ supply (shown as 49 in Figure 3). The supply may be a propane or natural gas burner located remote from the unit 12.
If the PDC coils 22 lowered the RH of the greenhouse air stream below a desired level, or the return air is low in RH (e.g. during high solar periods when internal air temperatures rise), water can be reintroduced into the air stream by the humidifier 32, which may suitably be a series of water jets that are controllable to emit a fine spray of water into the air stream. The humidifier 32 has an injection port 33 that is fluidly connected to a water supply (not shown).
The fan 38 is provided downstream of the humidifier 32 to move the greenhouse air stream through the system 10, and particularly, from the air return ducting 14, through the unit 12, and back into the greenhouse via air supply ducting 18.
After the greenhouse air stream has been processed by the unit 12, it is returned as supply air to the greenhouse. In particular, the supply air is discharged through the Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - g -supply air ducting 18 and into the greenhouse through a supply air distribution array 50.
Referring to Figure 3, the distribution array 50 is located inside and along the floor at one end of the greenhouse. Referring to Figure 4, the distribution array 50 is a series of branching tubes that distribute air from a main supply tube 51 to a plurality of branch tubes 52 and then to a plurality of outlets 54 of each branch tube 52. An air damper may be provided at each branching point to balance the air flow between each of the downstream branches; such air dampers are conventional devices known in the HVAC
industry to serve such a purpose.
Each branch tube outlet 54 is connected to a distribution tube 56 that has a plurality of small apertures along its length to discharge processed air back into the greenhouse. A plurality of distribution tubes 56 are shown in Figure 3 to extend from the distribution array 50 at one end of the greenhouse, along the floor of the greenhouse, and to the opposite end of the greenhouse. With such a configuration, processed supply air is discharged relatively uniformly from the ground of the greenhouse.
Mounted near the top of the greenhouse at the end opposite the end having the distribution array 50, is a greenhouse air collector array 60. Hot air rising towards the roof of the greenhouse is sucked into the collector array 60 for delivery via return air return ducting 14 to the processing unit 12.
One or more C02 sensors, thermometers and hygrometers (not shown) are provided in the greenhouse nearthe distribution tubes 56 to measure the respective C02 level, RH and temperature of the processed supply air. Additional C02 sensors, thermometers and hygrometers (not shown) are located above the plants and/or near the air collector array 60 to measure the RH and temperature of the return air. A
computer (not shown) is programmed with a climate control program, and is communicatively linked to the COZ sensors, thermometers and hygrometers and the processing unit 12. In the computer system, the program has stored a number of reference climate profiles for different plants. For each plant's climate profile there is included a number of parameters such as preferred temperature range, RH range, and C02 range for different times of the day, and for different seasons in the year. The parameters in each reference profile are adjustable by operator, enabling the operator to fine tune the reference profile to the particular plant he is growing; or, the operator Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 -may input his own parameters and create his own unique climate profile. In operation, the computer compares the actual climate conditions inside the greenhouse as measured by the thermometers and hygrometers against the reference levels, and controls the processing unit 12 to process air to conform to the reference levels.
Alternatively, such control may be performed manually by an operator, who can monitor the measured climate conditions, e.g. via a computer monitor at a station inside the greenhouse, and make the necessary adjustments to the unit 12.
According to a second embodiment of the invention, and referring to Figure 5, a climate control system 100 is provided that includes the climate control unit 12 as described above, as well as components for providing hot water radiant heating to the greenhouse interior. The system includes a pair of boilers B1 and B2, a main water distribution loop 102 fluidly connected to the boilers B1 and B2, a primary pump P3 for pumping water through the main water distribution loop 102, an expansion tank fluidly connected to the distribution loop 102 for accepting increased water volume resulting from thermal expansion, a make-up water source MU1 fluidly connected to the distribution loop 102 for providing a uniform water pressure inside distribution loop 102, a roof heating system A fluidly connected to the distribution loop 102, a floor heating system C thermally connected to the distribution loop 102, and an irrigation system D
thermally connected to the distribution loop 102.
Roof heating system A comprises a loop of metal roof piping 104 mounted near the roof of the greenhouse, and serves to heat the roof by hot water radiant heating, to melt any snow that may have accumulated on the roof. The roof piping 104 has an inlet and an outlet connected to the main water distribution loop 102 such that supply water heated by the boilers B1, B2 is delivered to the roof piping 104, and return water cooled from the heat transfer to the roof is returned to the boilers B1 and B2 for reheating. Flow of heating water through the roof piping can be controlled by controlling a control valve Z.
Floor heating system C comprises a heat exchanger HA, a closed loop of floor piping 106 mounted to the floor of the greenhouse and having a portion passing through the heat exchanger HA, heat transfer piping 108 having an inlet and outlet fluidly connected to the main water distribution loop 102 and having a closed portion passing Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 10 -through the heat exchanger HA, control valves V1A and V1B located at the inlet and outlet of the heat transfer piping 108, a pump P7 located in the heat transfer piping 108, pumps P8 and P9 located in the floor piping 106, a make-up water source MU2 fluidly connected to the floor piping 106, and an expansion tank E2 fluidly connected to the floor piping 106. In heating operation, valves V1A and V2A are opened and hot water heated by boilers B1, B2 is pumped through the heat transfer piping 108 by pump P7.
Heat is radiantly transferred from the heat transfer piping 108 to the floor piping 106 inside heat exchanger HA, and the heated water in the floor piping 106 is pumped through the floor piping 106 by the pumps P8 and P9. Water flow inside the main water distribution loop 102 is fluidly isolated from the water flow inside the floor system C.
Irrigation system D comprises a heat exchanger HB, a loop of irrigation piping mounted to the floor of the greenhouse and having a closed portion of the loop passing through the heat exchanger HB, heat transfer piping 112 having an inlet and an outlet fluidly connected to the main water distribution loop 102 and having a closed portion passing through the heat exchanger HB, a control valves V2A and V2B located at the inlet of the heat transfer piping 112, a pump P10 located in the heat transfer piping 112, and pumps P11 and P12 located in the irrigation piping 110. In heating operation, irrigation water to be delivered to the plants inside the greenhouse receives heat from boiler in a manner similar to the heat transfer to the floor heating system C.
That is, heated water from the boilers B1, B2 is pumped through heat transfer piping 112 by pump P10, and heat is radiantly transferred to the irrigation piping 110 inside heat exchanger HB. Water flow inside the main water distribution loop 102 is fluidly isolated from the water flow inside the irrigation system D.
Heating coils 28 of the unit 12 are fluidly connected to the main water distribution loop 102 by the heating water inflow conduit 46 and the heating water return conduit 48.
In this embodiment, heating coils 28 can also serve as cooling coils: control valve X is provided upstream of heating water inflow conduit, and can be closed to stop flow of heating water from the boilers B1, B2 to the heating coils 28; cold water from the cold water source is fluidly connected to the heating water inflow conduit 46 by cold water supply pipe 120; a control valve Y is provided between the inflow conduit 46 and cold water supply pipe 120. In heating operation, control valve Y is closed and control valve Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 11 -X is opened, so that hot water from boilers B1, B2 are pumped by a pump P5 through the heating coils 28. In cooling operation, control valve Y is opened, and control valve X is closed so that cold water from cold water source is pumped through the heating coils 28.
According to third embodiment of the invention, and referring to Figure 6, a climate control system 200 is provided that includes the climate control unit 12 as described above, the components of the second embodiment, as well as components to direct heat captured during the dehumidification and cooling operation of the unit 12 back into the greenhouse at an appropriate time.
l0 The additional components of the third embodiment include:
a heat exchanger HP;
floor heating supply conduit 202 having an inlet connected to the heat transfer piping 108 of floor heating system C downstream of the heat exchanger HA, an outlet connected to the heat transfer piping 108 upstream of the heat exchanger HA, and a closed portion passing through heat exchanger HP;
a control valve V3 in floor heating supply conduit 202 upstream of heat exchanger HA;
a irrigation heating supply conduit 206 having an inlet connected to heat transfer piping 112 of irrigation heating system D downstream of heat exchanger HB, an outlet connected to the heat transfer piping 112 upstream of the heat exchanger HB, and a closed portion passing through heat exchanger HP;
a control valve V4 in irrigation heating supply conduit 206 upstream of heat exchanger HB;
a heat exchanger pump 204 for pumping water in the floor heating supply conduit 202 and the irrigation heating supply conduit 206 and, a cooling water return conduit 208 fluidly connected to the outlet of the PDC
coils 22 and having a portion passing through the heat exchanger HP.
On occasions where greenhouse heating is required, e.g. at night or during the winter, the boilers B1 and B2 are operated to provide heat to the greenhouse interior via the radiant heating water loop and via heating coils 28. Additional heating can also be Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 12 -provided to the greenhouse interior using heat extracted from the greenhouse return air by the processing unit 12, as follows: Valves V1A, V1 B and V2A, V2B are closed to stop radiant heating water from flowing into heating loops HA and HB (boilers B1 and B2 may be shut off or turned down at this time to save energy). Then, valves V3 and V4 are opened and pump 204 is operated to pump water through heat transfer piping 108, 112 to heat exchangers HA and HB.
Cooling water that has absorbed heat during the greenhouse air cooling process is directed through the conduit 208 and through the heat exchanger HP; heat is then radiantly transferred from the cooling water to the water in heat transfer piping 108, 112.
In all embodiments, a system is provided to process the internal air of a greenhouse and provide simultaneous control of various climate parameters, namely RH, temperature and carbon dioxide content. These climate parameters are monitored and adjusted as needed by a computer or operator. Recovered heat can be reused in the greenhouse to reduce energy costs associated with operating the greenhouse.
Recovered water (condensate) can be reused by the greenhouse to reduce water usage. By controlling the climate using climate using system 10, the use of venting or other conventional energy or resource wasting measures can be minimized. For example, studies have shown that carbon dioxide usage is reduced by up to 54%
by using system 10, i.e. a reduction of 81 kg/hour/? of carbon dioxide lost to the atmosphere.
While the present invention has been described herein by the preferred embodiments, it will be understood to those skilled in the art that various changes may be made and added to the invention. The changes and alternatives are considered within the spirit and scope of the present invention.
Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 13 -
Filename: 28452 v1 Greenhouse Climate Control System FIELD OF THE INVENTION
The invention relates generally to a climate control system for a greenhouse.
BACKGROUND OF THE INVENTION
A greenhouse is an enclosure for cultivating and protecting plants inside the greenhouse from the outside environment. Greenhouses are designed to control the balance oftemperature, moisture, COZcontent, and light to suit the growth requirements for plants, and particularly, for tender plants or plants grown out of season.
The temperature conditions inside the greenhouse will depend on the type of plant grown in the greenhouse. Some plants require substantially the same temperature to be maintained 24 hours a day, while other plants will require very specific temperature changes at different times of the day. The temperature outside the greenhouse of course affects the temperature inside. Further, solar radiation during a sunny day can heat the greenhouse, dramatically increasing the inside temperature.
Typical energy sources used to heat greenhouses include natural gas, propane, wood, coal, solar radiation, and electricity. Some of the energy sources can be used directly to heat the greenhouse, wherein others such as propane or natural gas are burned in a gas-fired boiler to heat water. The heated water is distributed through heat-conductive pipes that typically are located near the plants to be heated. The heat radiated by these pipes is typically distributed around the greenhouse by a series of fans that are used to circulate air.
Cooling the greenhouse may be achieved via a number of ways. For example, wall and roof vents may be provided that are opened to allow outside ambient air inside the greenhouse and inside hot air to escape. Fans may be provided to assist in this air Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 exchange. Roof vents in particular can be configured to open small or large portions of the roof. A shading system may be provided on the roof and walls that during the day block incoming solar radiation from entering the greenhouse. The shading system may also serve as thermal barriers, and as such be used at night to reduce heat loss out of the greenhouse when the outside is cooler than the inside. Typical shades are made of a porous fabric that allow for some limited air flow through the fabric. Other cooling systems include fog systems that include high pressure pumps that are used to distribute a fine mist of high pressure water (often in excess of 1000psi) via a plurality of very small nozzles. The water molecules tend to absorb some of the heat inside the greenhouse, but will fall to the ground and increase relative humidity (RH).
Therefore, fog systems are best used for temporary cooling.
Another important consideration for greenhouse design is the control of humidity within the greenhouse. The relative humidity inside a greenhouse usually builds up during the night while the plants are transpiring, and by evaporation of any liquid water that is left on the floor during the day from irrigation cycles, fog cooling, etc. Overly high RH will prevent a plant from cooling itself adequately, while an overly low RH
will cause the plant to dry out. Therefore, precise control of the RH in a greenhouse is important to prevent the plants within from suffering.
Typically, greenhouse operators vent the greenhouse early in the morning, e.g.
by opening roof vents, to reduce the RH that has built up inside the greenhouse over the night. Also, exhaust fans typically used for cooling can be turned on to increase the air exchange rate into and out of the greenhouse. When internal RH is lower than desired, systems typically used for cooling can be activated to increase the RH, e.g.
by turning on the fog mist system and/or pad cooling system, provided that appropriate conditions exist for such operation. Many of these known humidity controlling techniques require the exchange of outside and inside air; if the RH or the temperature of the outside air is not at an appropriate level, then such techniques are less effective, or even dangerous to the health of the plant. For example, venting moisture from a greenhouse on a cold damp day may not appreciably reduce the RH inside the greenhouse, may cause a dramatic temperature change-related shock to the plants, Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 2 -and may increase operating costs by requiring additional heat to be supplied to warm the greenhouse back to its pre-venting temperature.
Other factors that are considered in greenhouse design include plant irrigation and carbon dioxide supply. It has been long recognized that elevated levels of enhances crop growth, and as such, growers try to maintain C02 levels at higher than ambient conditions inside the greenhouse. Typically, C02 introduced into the greenhouses is produced by one or more of open air natural gas or propane burners, flue gas recovery systems, or supplied from liquid C02 tanks. If C02 is introduced via a combustion process, unwanted water, carbon monoxide and nitrous oxides are typically also introduced with the C02 into the greenhouse. C02 is typically introduced into the greenhouse during the day. Unfortunately, other climate control techniques used during the day compromise the effectiveness of COZ injection. For example, periodic venting of moisture from the greenhouse tends to also vent a substantial amount of the injected CO2.
Various factors must be controlled to maintain an ideal environment for plant growth. The traditional methods and systems for controlling one factor are often not compatible with controlling another factor, and thereby results in high operating costs and reduced plant growth. A typical day and night cycle illustrates the difficulty of controlling such factors. During the night, plants give off moisture and C02.
By the end of the night, the RH and C02 will tend to be relatively high. As the sun rises, and the plants awaken to their day cycle, they requires moisture which is provided to them by the greenhouse irrigation system, which further raises the RH inside the greenhouse.
The RH must be reduced quickly to avoid damaging the plants. Air exchange methods are thus undertaken to replace the RH-heavy greenhouse airwith lower RH
outside air.
As the internal air is discharged, accumulated COZthat would be usefully used during the day is also flushed out of the greenhouse. The vents are often left open for extended periods to cool and reduce the moisture content inside the greenhouse, forcing the operator to pump a relatively high amount of COZ into the greenhouse to compensate for the amounts lost by venting. As the sun falls and evening sets in, venting may also occur to lower the RH prior to nightfall. Such venting often prevents Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 3 the use of the greenhouse's shading system that would normally be used for heat retention. Heaters must therefore be run at a relatively high level to compensate for the heat lost by venting.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided an air processing unit for a greenhouse comprising a main body having a greenhouse return air inlet, a greenhouse supply air outlet, and an air flow path between the inlet and outlet. Further, inside the main body in the air flow path there is: an air temperature modifier, an air humidity modifier; and a COZ injector. Greenhouse return air fed into the air processing unit is processed to modify one or more of its temperature, relative humidity, or C02 content before being discharged from the air processing unit as supply air back into the greenhouse.
The air temperature modifier may comprise an air cooler and an air heater, and the humidity modifier may comprise a dehumidifier and a humidifier. The dehumidifier and cooler may comprise dehumidification and cooling coils that flow cooling fluid therethrough so that heat in the air path passing by the coils is transferred to the cooling fluid, and moisture in the air path is condensed inside the unit. The humidifier may comprise at least one water jet for spraying a mist of water into the air path. The heater may comprise primary heating heat exchanger coils that flow hot water therethrough so that heat is radiated from the hot water and into the air stream.
The air processing unit may further comprise reheating heat exchanger coils that are fluidly connected to the dehumidification and cooling coils, such that return cooling fluid from the dehumidification and cooling coils is flowable through the reheating heat exchanger coils to transfer some of the heat extracted during cooling and dehumidification back into the air stream.
According to another aspect of the invention, a climate control system for a greenhouse is provided that comprises the air processing unit as described above, a Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 4 -greenhouse return air collector inside the greenhouse, a return air duct fluidly connected to the return air collector and the inlet of the processing unit; a greenhouse supply air distributor inside the greenhouse, and, a supply air duct fluidly connected to the supply air distributor and outlet of the processing unit.
$
Distribution tubes may be provided that are fluidly connected to the supply air distributor and mounted to the floor of the greenhouse, and have a plurality of spaced openings for discharging supply air into the greenhouse.
The climate control system may further comprise temperature, humidity and carbon dioxide sensors mounted inside the greenhouse. The climate control system may further comprise a control unit communicatively linked to the temperature, humidity and carbon dioxide sensors, and the processing unit. The computer system has stored therein at least one reference plant climate profile; the control unit is configured to 1$ measure the temperature, humidity and carbon dioxide levels inside the greenhouse, compare the measured levels against the reference plant climate profile, and adjust the settings of the processing unit to modify the greenhouse air to conform to the reference plant climate profile.
The climate control system may further comprise a boiler and a main radiant heating water loop fluidly connected to the boiler, and wherein the primary heating coils are fluidly connected to the main radiant heating water loop. A floor heating system may_also be fluidly connected to the main radiant heating water loop. The floor heating system may comprise a heat exchanger thermally connected to the floor heating system 2$ and to a cooling fluid return conduit connected to the processing unit, such that some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the floor heating system.
The climate control system may further comprise an irrigation heating system that is fluidly connected to the main radiant heating water loop. The irrigation heating system may comprise a heat exchanger thermally connected to the irrigation heating system and to a cooling fluid return conduit connected to the processing unit, such that Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - $ -some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the irrigation heating system.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic perspective view of an air processing unit of a greenhouse climate control system according to an embodiment of the invention;
Figure 2 is a schematic top view of the processing unit of Figure 1;
Figure 3 is a schematic perspective view of a greenhouse incorporating the climate control system;
Figure 4 a schematic top view of a greenhouse supply air distribution array of the greenhouse climate control system;
Figure 5 is a schematic piping diagram of an another embodiment of the greenhouse climate control system; and, Figure 6 is schematic piping diagram of yet another embodiment of the greenhouse climate control system.
DETAILED DESCRIPTION
Referring to Figures 1 and 2 and according to one embodiment of the invention, there is provided a greenhouse climate control system 10 for controlling the temperature, relative humidity (RN) and COZ levels in a greenhouse. The system has an air processing unit 12 that receives return air from the greenhouse via a return air duct 14 connected to an inlet 16 of the unit 12. The unit 12 discharges processed supply air back to the greenhouse via a supply air duct 18 connected to an outlet 20 of the unit 12. The unit 12 is preferably fluidly sealed to prevent or at least significantly impede air from escaping from the unit 12.
Inside the unit 12 are a number of components for processing the greenhouse air, including primary dehumidication and cooling coils 22, airfilters 24, re-heat coils 26, heating coils 28, a COZ injector 30, a humidifier 32, and a fan 38. All of these Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 6 -components are arranged in-line with the air flow so that air passing through the unit 12 will encounter each of these components in sequential downstream order.
Return air from the greenhouse is typically warm and saturated with water. The air entering the unit 12 first passes by air filters 24 to remove any unwanted particulates that may damage the unit 12, as well as to provide cleaner air back into the greenhouse. The filters 24 per se are of a conventional design and may be for example, disposable fibre filters commonly used in the HVAC industry.
Having passed through the filters 24, the air then passes by the primary dehumidification and cooling coils (PDC coils) 22. The PDC coils 22 are made from thin copper tubing and have an inlet and an outlet for the inflow and outflow of a cooling fluid, such as water, or a suitable refrigerant fluid. The coil pattern can be based on one of many known heat exchanger coil designs in the refrigeration industry. The PDC coils 22 are preferably made of copper but may be made with any material having a suitably high degree of thermal conductivity. In a system using cooling water as the cooling fluid, cooling water is pumped through the PDC coils 22 from a cold water source via cooling water conduit 40 connected to the inlet of the PDC coils 22. As warm greenhouse return air passes by the PDC coils 22, heat will be transferred from the air to the cooling water, thereby lowering the temperature of the air and raising the temperature of the cooling water. As the air cools, its RH will reach 100% and the air will reach its dew point and will not be able to hold any more water; as the air is cooled further, some of the water vapour will condense inside the unit 12 and particularly on the PDC coil 22. This condensed water is drained from the unit 12 through a drain (not shown) at the bottom of the unit 12. The recovered water can then be stored for reuse by other systems, such as the irrigation and fog systems.
The cooling water warmed during the cooling and dehumidification of the greenhouse air can be immediately removed from the unit 12 for discharge via a cooling water return conduit 42 connected to the outlet of the PDC coils 22, or can be directed through the reheat coils 26 to return some of the heat back to the greenhouse air stream, before being removed from the unit 12. The removed heat can be stored in a heat sink (not shown) such as a pond or an irrigation storage tank, such that the heat can be usefully used later. The path of the cooling water is controlled by a diversion Leeb % ::ODMA\PCDOCS\VAN LAW\28451\1 - 7 valve 44. If the greenhouse requires cooling, then the diversion valve 44 is set to bypass the re-heat coils 26 and to direct the water immediately to the return conduit 42 for removal from the unit 12. If however, the temperature of the greenhouse is at or about nominal levels, or requires heating (e.g. at night, or during the winter), the diversion valve 44 can be set to direct water through the reheat coils 26 to return some of the heat back to the greenhouse air. The re-heat coils 26 are a heat exchanger having a construction similar to the PDC coils 22, and in particular has an outlet that is fluidly connected to the return conduit 42.
The heating coils 28 are a heat exchanger and are constructed similarly to the PDC coils 22 and the reheat coils 26. Heated water is transmittable through the heating coil 28 via a heated water inflow conduit 46 fluidly connected to an inlet of the heating coil 28, and a heated water return conduit 48 fluidly connected to an outlet of the heating coil 28. On occasions requiring heating of the greenhouse air, the heating coil 28 is activated by flowing hot water through the heating coil 28 so that heat from the heating water can be transferred to the greenhouse air stream.
COZ can be introduced into the air stream by one or more COZ injectors 30 located downstream of the heating coil 28. The C02 injectors 30 have an injection port 36 which is fluidly connected to a COZ supply (shown as 49 in Figure 3). The supply may be a propane or natural gas burner located remote from the unit 12.
If the PDC coils 22 lowered the RH of the greenhouse air stream below a desired level, or the return air is low in RH (e.g. during high solar periods when internal air temperatures rise), water can be reintroduced into the air stream by the humidifier 32, which may suitably be a series of water jets that are controllable to emit a fine spray of water into the air stream. The humidifier 32 has an injection port 33 that is fluidly connected to a water supply (not shown).
The fan 38 is provided downstream of the humidifier 32 to move the greenhouse air stream through the system 10, and particularly, from the air return ducting 14, through the unit 12, and back into the greenhouse via air supply ducting 18.
After the greenhouse air stream has been processed by the unit 12, it is returned as supply air to the greenhouse. In particular, the supply air is discharged through the Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - g -supply air ducting 18 and into the greenhouse through a supply air distribution array 50.
Referring to Figure 3, the distribution array 50 is located inside and along the floor at one end of the greenhouse. Referring to Figure 4, the distribution array 50 is a series of branching tubes that distribute air from a main supply tube 51 to a plurality of branch tubes 52 and then to a plurality of outlets 54 of each branch tube 52. An air damper may be provided at each branching point to balance the air flow between each of the downstream branches; such air dampers are conventional devices known in the HVAC
industry to serve such a purpose.
Each branch tube outlet 54 is connected to a distribution tube 56 that has a plurality of small apertures along its length to discharge processed air back into the greenhouse. A plurality of distribution tubes 56 are shown in Figure 3 to extend from the distribution array 50 at one end of the greenhouse, along the floor of the greenhouse, and to the opposite end of the greenhouse. With such a configuration, processed supply air is discharged relatively uniformly from the ground of the greenhouse.
Mounted near the top of the greenhouse at the end opposite the end having the distribution array 50, is a greenhouse air collector array 60. Hot air rising towards the roof of the greenhouse is sucked into the collector array 60 for delivery via return air return ducting 14 to the processing unit 12.
One or more C02 sensors, thermometers and hygrometers (not shown) are provided in the greenhouse nearthe distribution tubes 56 to measure the respective C02 level, RH and temperature of the processed supply air. Additional C02 sensors, thermometers and hygrometers (not shown) are located above the plants and/or near the air collector array 60 to measure the RH and temperature of the return air. A
computer (not shown) is programmed with a climate control program, and is communicatively linked to the COZ sensors, thermometers and hygrometers and the processing unit 12. In the computer system, the program has stored a number of reference climate profiles for different plants. For each plant's climate profile there is included a number of parameters such as preferred temperature range, RH range, and C02 range for different times of the day, and for different seasons in the year. The parameters in each reference profile are adjustable by operator, enabling the operator to fine tune the reference profile to the particular plant he is growing; or, the operator Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 -may input his own parameters and create his own unique climate profile. In operation, the computer compares the actual climate conditions inside the greenhouse as measured by the thermometers and hygrometers against the reference levels, and controls the processing unit 12 to process air to conform to the reference levels.
Alternatively, such control may be performed manually by an operator, who can monitor the measured climate conditions, e.g. via a computer monitor at a station inside the greenhouse, and make the necessary adjustments to the unit 12.
According to a second embodiment of the invention, and referring to Figure 5, a climate control system 100 is provided that includes the climate control unit 12 as described above, as well as components for providing hot water radiant heating to the greenhouse interior. The system includes a pair of boilers B1 and B2, a main water distribution loop 102 fluidly connected to the boilers B1 and B2, a primary pump P3 for pumping water through the main water distribution loop 102, an expansion tank fluidly connected to the distribution loop 102 for accepting increased water volume resulting from thermal expansion, a make-up water source MU1 fluidly connected to the distribution loop 102 for providing a uniform water pressure inside distribution loop 102, a roof heating system A fluidly connected to the distribution loop 102, a floor heating system C thermally connected to the distribution loop 102, and an irrigation system D
thermally connected to the distribution loop 102.
Roof heating system A comprises a loop of metal roof piping 104 mounted near the roof of the greenhouse, and serves to heat the roof by hot water radiant heating, to melt any snow that may have accumulated on the roof. The roof piping 104 has an inlet and an outlet connected to the main water distribution loop 102 such that supply water heated by the boilers B1, B2 is delivered to the roof piping 104, and return water cooled from the heat transfer to the roof is returned to the boilers B1 and B2 for reheating. Flow of heating water through the roof piping can be controlled by controlling a control valve Z.
Floor heating system C comprises a heat exchanger HA, a closed loop of floor piping 106 mounted to the floor of the greenhouse and having a portion passing through the heat exchanger HA, heat transfer piping 108 having an inlet and outlet fluidly connected to the main water distribution loop 102 and having a closed portion passing Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 10 -through the heat exchanger HA, control valves V1A and V1B located at the inlet and outlet of the heat transfer piping 108, a pump P7 located in the heat transfer piping 108, pumps P8 and P9 located in the floor piping 106, a make-up water source MU2 fluidly connected to the floor piping 106, and an expansion tank E2 fluidly connected to the floor piping 106. In heating operation, valves V1A and V2A are opened and hot water heated by boilers B1, B2 is pumped through the heat transfer piping 108 by pump P7.
Heat is radiantly transferred from the heat transfer piping 108 to the floor piping 106 inside heat exchanger HA, and the heated water in the floor piping 106 is pumped through the floor piping 106 by the pumps P8 and P9. Water flow inside the main water distribution loop 102 is fluidly isolated from the water flow inside the floor system C.
Irrigation system D comprises a heat exchanger HB, a loop of irrigation piping mounted to the floor of the greenhouse and having a closed portion of the loop passing through the heat exchanger HB, heat transfer piping 112 having an inlet and an outlet fluidly connected to the main water distribution loop 102 and having a closed portion passing through the heat exchanger HB, a control valves V2A and V2B located at the inlet of the heat transfer piping 112, a pump P10 located in the heat transfer piping 112, and pumps P11 and P12 located in the irrigation piping 110. In heating operation, irrigation water to be delivered to the plants inside the greenhouse receives heat from boiler in a manner similar to the heat transfer to the floor heating system C.
That is, heated water from the boilers B1, B2 is pumped through heat transfer piping 112 by pump P10, and heat is radiantly transferred to the irrigation piping 110 inside heat exchanger HB. Water flow inside the main water distribution loop 102 is fluidly isolated from the water flow inside the irrigation system D.
Heating coils 28 of the unit 12 are fluidly connected to the main water distribution loop 102 by the heating water inflow conduit 46 and the heating water return conduit 48.
In this embodiment, heating coils 28 can also serve as cooling coils: control valve X is provided upstream of heating water inflow conduit, and can be closed to stop flow of heating water from the boilers B1, B2 to the heating coils 28; cold water from the cold water source is fluidly connected to the heating water inflow conduit 46 by cold water supply pipe 120; a control valve Y is provided between the inflow conduit 46 and cold water supply pipe 120. In heating operation, control valve Y is closed and control valve Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 11 -X is opened, so that hot water from boilers B1, B2 are pumped by a pump P5 through the heating coils 28. In cooling operation, control valve Y is opened, and control valve X is closed so that cold water from cold water source is pumped through the heating coils 28.
According to third embodiment of the invention, and referring to Figure 6, a climate control system 200 is provided that includes the climate control unit 12 as described above, the components of the second embodiment, as well as components to direct heat captured during the dehumidification and cooling operation of the unit 12 back into the greenhouse at an appropriate time.
l0 The additional components of the third embodiment include:
a heat exchanger HP;
floor heating supply conduit 202 having an inlet connected to the heat transfer piping 108 of floor heating system C downstream of the heat exchanger HA, an outlet connected to the heat transfer piping 108 upstream of the heat exchanger HA, and a closed portion passing through heat exchanger HP;
a control valve V3 in floor heating supply conduit 202 upstream of heat exchanger HA;
a irrigation heating supply conduit 206 having an inlet connected to heat transfer piping 112 of irrigation heating system D downstream of heat exchanger HB, an outlet connected to the heat transfer piping 112 upstream of the heat exchanger HB, and a closed portion passing through heat exchanger HP;
a control valve V4 in irrigation heating supply conduit 206 upstream of heat exchanger HB;
a heat exchanger pump 204 for pumping water in the floor heating supply conduit 202 and the irrigation heating supply conduit 206 and, a cooling water return conduit 208 fluidly connected to the outlet of the PDC
coils 22 and having a portion passing through the heat exchanger HP.
On occasions where greenhouse heating is required, e.g. at night or during the winter, the boilers B1 and B2 are operated to provide heat to the greenhouse interior via the radiant heating water loop and via heating coils 28. Additional heating can also be Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 12 -provided to the greenhouse interior using heat extracted from the greenhouse return air by the processing unit 12, as follows: Valves V1A, V1 B and V2A, V2B are closed to stop radiant heating water from flowing into heating loops HA and HB (boilers B1 and B2 may be shut off or turned down at this time to save energy). Then, valves V3 and V4 are opened and pump 204 is operated to pump water through heat transfer piping 108, 112 to heat exchangers HA and HB.
Cooling water that has absorbed heat during the greenhouse air cooling process is directed through the conduit 208 and through the heat exchanger HP; heat is then radiantly transferred from the cooling water to the water in heat transfer piping 108, 112.
In all embodiments, a system is provided to process the internal air of a greenhouse and provide simultaneous control of various climate parameters, namely RH, temperature and carbon dioxide content. These climate parameters are monitored and adjusted as needed by a computer or operator. Recovered heat can be reused in the greenhouse to reduce energy costs associated with operating the greenhouse.
Recovered water (condensate) can be reused by the greenhouse to reduce water usage. By controlling the climate using climate using system 10, the use of venting or other conventional energy or resource wasting measures can be minimized. For example, studies have shown that carbon dioxide usage is reduced by up to 54%
by using system 10, i.e. a reduction of 81 kg/hour/? of carbon dioxide lost to the atmosphere.
While the present invention has been described herein by the preferred embodiments, it will be understood to those skilled in the art that various changes may be made and added to the invention. The changes and alternatives are considered within the spirit and scope of the present invention.
Leeb / ::ODMA\PCDOCS\VAN LAW\28451\1 - 13 -
Claims (14)
1. An air processing unit for a greenhouse comprising:
(a) a main body having a greenhouse return air inlet, a greenhouse supply air outlet, and an air flow path between the inlet and outlet; and inside the main body in the air flow path:
(b) an air temperature modifier (c) an air humidity modifier; and (d) a C02 injector, wherein greenhouse return air fed into the air processing unit is processed to modify one or more of its temperature, relative humidity, or CO2 content before being discharged from the air processing unit as supply air back into the greenhouse.
(a) a main body having a greenhouse return air inlet, a greenhouse supply air outlet, and an air flow path between the inlet and outlet; and inside the main body in the air flow path:
(b) an air temperature modifier (c) an air humidity modifier; and (d) a C02 injector, wherein greenhouse return air fed into the air processing unit is processed to modify one or more of its temperature, relative humidity, or CO2 content before being discharged from the air processing unit as supply air back into the greenhouse.
2. The air processing unit of claim 1 wherein the air temperature modifier comprises an air cooler and an air heater.
3. The air processing unit of claim 2 wherein the humidity modifier comprises a dehumidifier and a humdifier.
4. The air processing unit of claim 3 wherein the dehumidifier and cooler comprise dehumidification and cooling coils that flow cooling fluid therethrough so that heat in the air path passing by the coils is transferred to the cooling fluid, and moisture in the air path is condensed inside the unit.
5. The air processing unit of claim 3 wherein the humidifier comprises at least one water jet for spraying a mist of water into the air path.
6. The air processing unit of claim 2 wherein the heater comprises primary heating heat exchanger coils that flow hot water therethrough so that heat is radiated from the hot water and into the air stream.
7. The air processing unit of claim 6 further comprising reheating heat exchanger coils that are fluidly connected to the dehumidification and cooling coils, such that return cooling fluid from the dehumidification and cooling coils is flowable through the reheating heat exchanger coils to transfer some of the heat extracted during cooling and dehumidification back into the air stream.
8. A climate control system for a greenhouse comprising the air processing unit of claim 1, a greenhouse return air collector inside the greenhouse;
a return air duct fluidly connected to the return air collector and the inlet of the processing unit;
a greenhouse supply air distributor inside the greenhouse; and, a supply air duct fluidly connected to the supply air distributor and outlet of the processing unit.
a return air duct fluidly connected to the return air collector and the inlet of the processing unit;
a greenhouse supply air distributor inside the greenhouse; and, a supply air duct fluidly connected to the supply air distributor and outlet of the processing unit.
9. The climate control system of claim 8 further comprising distribution tubes fluidly connected to the supply air distributor and mounted to the floor of the greenhouse, and having a plurality of spaced openings for discharging supply air into the greenhouse.
10. The climate control system of claim 8 further comprising a temperature, humidity and carbon dioxide sensors mounted inside the greenhouse.
11. The climate control system of claim 10 further comprising a control unit communicatively linked to the temperature, humidity and carbon dioxide sensors, and the processing unit, and having stored therein at least one reference plant climate profile, the control unit configured to measure the temperature, humidity and carbon dioxide levels inside the greenhouse, compare the measured levels against the reference plant climate profile, and adjust the settings of the processing unit to modify the greenhouse air to conform to the reference plant climate profile.
12. The climate control system of claim 10 further comprising a boiler, and a main radiant heating water loop fluidly connected to the boiler, and wherein the primary heating coils are fluidly connected to the main radiant heating water loop.
13. The climate control system of claim 12 further comprising a floor heating system fluidly connected to the main radiant heating water loop, a heat exchanger thermally connected to the floor heating system and to a cooling fluid return conduit connected to the processing unit, such that some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the floor heating system.
14. The climate control system of claim 12 further comprising a irrigation heating system fluidly connected to the main radiant heating water loop, a heat exchanger thermally connected to the irrigation heating system and to a cooling fluid return conduit connected to the processing unit, such that some of the heat absorbed by cooling fluid in the unit is transferred via the heat exchanger to the irrigation heating system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002358337A CA2358337A1 (en) | 2001-10-02 | 2001-10-02 | Greenhouse climate control system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002358337A CA2358337A1 (en) | 2001-10-02 | 2001-10-02 | Greenhouse climate control system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2358337A1 true CA2358337A1 (en) | 2003-04-02 |
Family
ID=4170185
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002358337A Abandoned CA2358337A1 (en) | 2001-10-02 | 2001-10-02 | Greenhouse climate control system |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2358337A1 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3007620A1 (en) * | 2013-07-01 | 2015-01-02 | Objectif Technologie & Systemes | METHOD FOR MANAGING GAS FLOWS FROM A COMPOSTER AND SUPPLYING THE INSIDE OF A CARBON DIOXIDE GREENHOUSE |
| ITUB20150681A1 (en) * | 2015-05-21 | 2016-11-21 | Micoperi Blue Growth S R L | Plant and process for the production of microorganisms in aquaculture |
| CN113519321A (en) * | 2021-06-02 | 2021-10-22 | 邓燕 | Agricultural greenhouse ventilation's heat recovery economizer |
| WO2022195528A1 (en) * | 2021-03-19 | 2022-09-22 | Reuvers Eduard Johannis Adrianus | Plant growing apparatus and method for enriching air with exhaled co2 |
-
2001
- 2001-10-02 CA CA002358337A patent/CA2358337A1/en not_active Abandoned
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR3007620A1 (en) * | 2013-07-01 | 2015-01-02 | Objectif Technologie & Systemes | METHOD FOR MANAGING GAS FLOWS FROM A COMPOSTER AND SUPPLYING THE INSIDE OF A CARBON DIOXIDE GREENHOUSE |
| ITUB20150681A1 (en) * | 2015-05-21 | 2016-11-21 | Micoperi Blue Growth S R L | Plant and process for the production of microorganisms in aquaculture |
| WO2016185438A1 (en) * | 2015-05-21 | 2016-11-24 | Micoperi Blue Growth S.R.L. | Plant and method for producing microorganisms in aquaculture |
| WO2022195528A1 (en) * | 2021-03-19 | 2022-09-22 | Reuvers Eduard Johannis Adrianus | Plant growing apparatus and method for enriching air with exhaled co2 |
| CN113519321A (en) * | 2021-06-02 | 2021-10-22 | 邓燕 | Agricultural greenhouse ventilation's heat recovery economizer |
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