AU2006202086A1 - Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) - Google Patents
Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) Download PDFInfo
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P001 Section 29 Regulation 3.2(2)
AUSTRALIA
Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) The following statement is a full description of this invention, including the best method of performing it known to me: METHOD AND APPARATUS FOR ENHANCING PLANT GROWTH IN A c GREENHOUSE (OR OTHER CONTROLLED ENVIRONMENT) FIELD OF THE INVENTION The field of the invention relates generally to enhancement of plant growth in a greenhouse and particularly to enhancement of plant growth by controlling 1the conditions and environment within the greenhouse, by converting a fuel gas 00 0 and available oxygen to products useful to assist photosynthesis on vegetation and surplus heat energy and electrical power. It will be convenient hereinafter to describe the invention in relation to application in a greenhouse and greenhouse environment. It should be appreciated, however, that the present invention is not limited to greenhouse applications only.
BACKGROUND OF THE INVENTION The yield from cultivated crops, and length of the growing season, can be altered by controlling the crop environment. The correct amounts of water and nutrients can be supplied to plants to ensure growth. However, factors also affecting plant growth include the temperature conditions, intensity and duration of lighting, carbon dioxide (CO2) levels, water supply, soil saturation and humidity.
Plants may be kept warm by a circulating hot water system, the water heated by burning a fuel gas. In a glasshouse situation, heat from sunlight is trapped by the glass and also contributes to keeping plants warm.
Water may be provided from storage reservoirs to irrigate the crops and in some applications additional UV lighting may be provided to simulate a longer day, or more intense sunlight to stimulate the photosynthesis process of plants.
It is disclosed in US6,205,704 to enhance plant growth in a greenhouse by burning a fuel gas such as natural gas (methane CH 4 US6,205,704 discloses a system wherein the fuel gas (obtained from landfill gas reclamation) is combusted to heat water, the water then being circulated in order to raise the temperature inside the greenhouse. US6,205,704 also discloses a method of producing relatively pure CO2 from the landfill gas and supplying the gas to the greenhouse to stimulate plant growth. CO2 is an essential ingredient in the photosynthesis of plants. In the presence of water, sunlight and CO2, plants will grow and also produce oxygen The process is optimised for various plants O at particular temperatures, levels of sunlight and humidity. US6,205,704 also discloses a system which additionally includes a turbine generator to recover Ssome of the additional energy from the combustion of the fuel gas.
However this and other similar means of adjusting the conditions inside a greenhouse remain wasteful of energy. For example, the energy in fuel gas combusted to provide heating is wasted as the combustion exhaust products are IN simply vented to atmosphere. Furthermore, the ability to control the various 00 important factors affecting plant growth is not stable and reliable, as adjusting one factor affecting plant growth may have a destabilising effect on another factor.
SIt is therefore desirable to provide apparatus for enhancing plant growth in N a greenhouse, and a control system for adjusting conditions in a greenhouse, which enable the improved use of total energy contained in the fuel gas. It is also desirable to ensure that the control system for operating such a greenhouse environment adjusting system is stable and reliable.
SUMMARY OF THE INVENTION A first aspect of the present invention provides apparatus for enhancing plant growth, in a greenhouse (or other controlled environment) including: a carbon dioxide sensor for detecting carbon dioxide levels in the greenhouse; and a combustion device for combusting a fuel gas to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; wherein the CO2 level in the greenhouse is maintained at a selected predetermined level by supplying the exhaust gases into the greenhouse and adjusting the rate of combustion of the fuel gas in response to the carbon dioxide level detected; Preferably, the combustion device is one of an internal combustion engine or a turbine.
In a preferred embodiment, the apparatus further includes: a humidity sensor for detecting humidity levels in the greenhouse; and a water supply system; wherein humidity and overall watering in the greenhouse is maintained at a selected predetermined level by adjusting the supply of water. Preferably, the water is supplied as a direct spray, misting, or as irrigation (depending on the status of soil saturation levels).
In a further preferred embodiment, the apparatus also includes a secondary means of maintaining humidity and overall watering in the greenhouse at a selected predetermined level, said secondary means operating only when humidity is increasing above the selected predetermined level.
IPreferably the apparatus includes: a heat exchanger for adjusting the temperature of the exhaust gases; wherein the humidity level in the greenhouse is maintained at a selected 0 predetermined level by adjusting the temperature of the exhaust gases in response to the humidity level detected, in order to condense some or all of the water vapour to a liquid, and supplying the remaining exhaust gases into the greenhouse, thereby adjusting the humidity of the greenhouse.
Under normal operating conditions, the water supplied as a combustion product into the greenhouse, whether as water vapour forming a part of the exhaust gas, or as a condensed liquid obtained from cooling exhaust gases, will be insufficient to plant requirements, and additional water supply from a reservoir or mains may be required.
The temperature of the greenhouse environment is partly regulated by the control of humidity in the greenhouse. However, in order to maintain a desired humidity, it may be necessary to cool the exhaust gases to a less than optimal temperature, therefore making additional greenhouse heating necessary.
Conversely, the heat supplied via exhaust gases may be excess to requirements.
Heat in the form of hot exhaust gases is supplied into the greenhouse atmosphere. The temperature of the exhaust gases maybe lowered in response to excess humidity levels. If not in conflict with humidity control, the temperature of the exhaust gases may be adjusted by passing them through the heat exchanger.
In a preferred embodiment, the apparatus further includes: a temperature sensor for detecting the temperature in the greenhouse; wherein heat rejected from the exhaust gases by passing the gases through the exhaust heat exchanger is supplied into the greenhouse in response to the temperature detected.
O Preferably, the apparatus also includes a refrigeration circuit associated C with the exhaust gas heat exchanger, the refrigeration circuit including a Scompressor driven by the combustion device.
Preferably, heat rejected from the refrigeration circuit is used to heat return air from the greenhouse, to provide a warm air stream which may selectively be supplied into the greenhouse, or used for a purpose external to the greenhouse, N or, not preferred, vented to atmosphere.
An additional source of heat for temperature adjustment is also available.
The combustion device may have a cooling circuit with an associated cooling circuit heat exchanger. Return air from the greenhouse may be passed through c the cooling circuit heat exchanger to become warmed air which may then be supplied as additional greenhouse heating.
Preferably, this warm air from the cooling circuit heat exchanger is combined with warm air obtained from heat rejected by the refrigeration circuit and controlled as a single additional source of greenhouse heating. The temperature in the greenhouse is thereby maintained at a selected predetermined level by controlling the amount of warm air supplied into the greenhouse in response to the temperature detected.
Preferably the apparatus further includes: an oxygen sensor for detecting oxygen levels in the greenhouse; and a modulated two-way air control valve controllable to selectively feed fresh air from outside the greenhouse and/or return air from inside the greenhouse to the combustion device for combustion of the fuel gas; wherein the oxygen level in the greenhouse is maintained at a selected predetermined level by controlling the source of air fed to the combustion device in response to the oxygen level detected.
Oxygen is produced by photosynthesis within the greenhouse as a product of plant growth. When oxygen for combustion is sourced solely from within the greenhouse atmosphere, the greenhouse becomes depleted or starved of oxygen. When oxygen for combustion is sourced solely from outside the greenhouse, 02 levels in the greenhouse may build up and ultimately inhibit plant growth, as the 02 displaces CO 2 SPreferably data from the 02 sensor is also used to control a fresh air fan.
O
SThe fresh air fan may be operated to supplement 02 requirements in the Sgreenhouse, for example, where seeds or seedlings do not produce sufficient 02 to balance the environment, or, more importantly, to enable the air inside the greenhouse to be purged.
The optimum CO2 levels for growing various crops may exceed the maximum safe level of C0O2 for humans and/or animals. Accordingly, it is desirable to have a fresh air fan which assists in venting the greenhouse N atmosphere and replacing the atmosphere with outside fresh air. This allows ahuman access to the greenhouse, for example, to attend to crops, harvest, or c perform maintenance.
Locking apparatus may be provided in order that humans are prevented from entering the greenhouse when conditions are hostile. For example, an interlock preventing the greenhouse door from being opened from the outside when the CO2 levels are above a safe level may be provided. It is also desirable to provide an emergency venting arrangement which may utilise the fresh air fan, and motion sensors to detect a human or animal presence in the greenhouse.
In a preferred embodiment, the apparatus further includes an alternator driven by the combustion device to generate electrical power and a UV sensor for detecting UV (Ultra Violet) lighting levels. The electrical power may then be used to power the control systems and sensors for the apparatus, pumps and other auxiliary equipment, and in particular to power artificial lighting, particularly UV lighting, in response to the UV level detected.
Any power generated excess to requirements may be fed back to the mains power grid or optionally stored for later usage. Any additional power required may be obtained from mains power. For example, when very low amounts of CO2 are required to be supplied into the greenhouse, the combustion device is controlled to operate at a lower power level, burning less fuel, and power supply may not be sufficient for total requirements.
Preferably, the apparatus further includes: a soil saturation sensor for detecting soil saturation levels in the greenhouse; and irrigation means for supplying water to said soil; 0 wherein the soil saturation level is maintained at a selected predetermined level by supplying water to the soil in response to the soil saturation level detected.
A second aspect of the present invention provides apparatus for enhancing plant growth, in a greenhouse (or other controlled environment) including: a carbon dioxide sensor for detecting carbon dioxide levels in the Igreenhouse; and i- a fuel cell for consuming a fuel gas to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; Swherein the 002 level in the greenhouse is maintained at a selected Spredetermined level by supplying the exhaust gases into the greenhouse and adjusting the rate of consumption of the fuel gas in response to the carbon dioxide level detected.
The second aspect of the invention may have other preferred features as described above in relation to the first aspect of the invention. The consumption of the fuel gas by a fuel cell is analogous to the consumption of the fuel gas by a fuel cell, requiring similar inputs and providing similar outputs, save that an internal combustion device or turbine provides work output as shaft work, which may be used and/or converted to electrical power, whereas a fuel cell provides electrical power as a direct current output.
The compressor for the refrigeration circuit of a preferred embodiment is not driven directly by the fuel cell, but rather electrically powered by an inverter converting the fuel cell direct current to alternating current.
A third aspect of the present invention provides a method for enhancing plant growth, in a greenhouse (or other controlled environment) including the steps of: combusting a fuel gas in a combustion device to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; supplying the exhaust gases into the greenhouse; detecting the carbon dioxide level in the greenhouse using a carbon dioxide sensor; and adjusting the rate of combustion of fuel gas to adjust the CO2 level in the greenhouse.
O Preferably the combustion device is an internal combustion engine or a Sgas turbine.
In a preferred embodiment, the method includes the subsequent steps of: detecting the humidity level in the greenhouse using a humidity sensor; supplying water for the greenhouse, preferably as a spray, mist or irrigation (depending on soil saturation levels), thereby adjusting the humidity Ilevel in the greenhouse in order to maintain a selected predetermined humidity 00 level.
In a further preferred embodiment, applicable only when humidity is
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Sincreasing above the selected predetermined level, the method further includes a Ssecondary humidity method including the subsequent steps of: adjusting the temperature of the exhaust gases in order to condense some or all of the water vapour to a liquid and supplying the remaining exhaust gases into the greenhouse, thereby adjusting the humidity level in the greenhouse in order to maintain a selected predetermined humidity level.
In a preferred embodiment, the method includes the subsequent steps of: detecting the temperature in the greenhouse using a temperature sensor; adjusting the temperature of exhaust gases using the exhaust heat exchanger (provided such adjustment is not in conflict with humidity control), thereby adjusting the temperature in the greenhouse in order to maintain a selected predetermined temperature.
Preferably, the method further includes a secondary temperature control method including the subsequent steps of: selectively supplying waste heat created by any of the preceding steps into the greenhouse, thereby adjusting the temperature in the greenhouse in order to maintain a selected predetermined temperature.
Said waste heat may be obtained from a cooling circuit associated with the combustion device, or from heat rejected by passing exhaust gases through the exhaust heat exchanger.
In a preferred embodiment the method includes the subsequent steps of: detecting the oxygen level in the greenhouse using an oxygen sensor; selectively supplying fresh outside air and/or return air from inside the greenhouse to the combustion device for combustion of the fuel gas, thereby O adjusting the oxygen level in the greenhouse in order to maintain a selected C predetermined oxygen level.
SIn a preferred embodiment, the method includes the subsequent steps of: detecting the UV light level in the greenhouse using a UV sensor; selectively providing artificial UV lighting, thereby adjusting the UV level in the greenhouse in order to maintain a selected predetermined UV level.
IPreferably, the UV lighting is powered by electricity generated by the 0o combustion device.
0 Preferably, the method includes the subsequent steps of: S- detecting the soil saturation level using a soil saturation sensor; N selectively supplying water to said soil to irrigate; wherein the soil saturation level is maintained at a selected predetermined level by supplying water to the soil in response to the soil saturation level detected.
A fourth aspect of the present invention provides a method for enhancing plant growth, in a greenhouse (or other controlled environment) including the steps of: consuming a fuel gas in a fuel to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; supplying the exhaust gases into the greenhouse; detecting the carbon dioxide level in the greenhouse using a carbon dioxide sensor; and adjusting the rate of consumption of fuel gas to adjust the CO2 level in the greenhouse.
The fourth aspect of the invention may have other preferred features as described above in relation to the third aspect of the invention.
The selected, predetermined levels of various factors affecting plant growth are dependent on the type of crop and the stage of the crop's development. It may be desirable to provide varied predetermined levels in order to stimulate, for example, a night/day cycle in summer, when the season is actually winter. Accordingly, the selected, predetermined levels may be varied manually, or in accordance with a pre-programmed schedule to suit particular requirements.
O The above apparatus and method enable economical and efficient use of a Sfuel gas, by minimising wasted energy. The combustion device, or fuel cell, is Sdeliberately operated and controlled to produce the desired level of CO2, with all other products of combustion being utilised as efficiently as possible. Hence the waste heat and power is used to heat and power the greenhouse, while combustion energy absorbed in vaporising the water portion of exhaust gases is Nrecovered and used in two ways some of the water vapour is used to control 00 humidity in the greenhouse, while heat recovered through the exhaust heat exchanger from condensing the excess water vapour is used in adjusting 0 greenhouse temperature.
N Various fuel gas types may be used, including natural gas, biogas and landfill gas. The various heating values and CO2 levels in each gas do not materially affect operation of the apparatus and method, as control is determined by the required CO2 level, with controls for humidity, temperature, oxygen, UV lighting and soil saturation successively and stably controlled in correct order for a stable control system.
BRIEF DESCRIPTION OF THE DRAWINGS By way of non-limiting examples, preferred embodiments of the present invention are detailed in the accompanying drawings, in which: Fig 1 is an embodiment of the present invention incorporating an internal combustion engine.
Fig 2 is a second embodiment of the present invention incorporating a packaged fuel cell.
Fig 3 is a third embodiment of the present invention incorporating a turbine.
Fig 4 is a simplified molecular flow diagram according to an embodiment of the present invention.
Fig 5 is a simplified process flow diagram according to an embodiment of the present invention, utilising a biogas fuel source.
Figs 2 and 3 repeat the same reference numbers where the elements are identical or analogous to those in Fig 1.
0 DESCRIPTION OF PREFERRED EMBODIMENT SA preferred embodiment of the invention is described below.
SReferring to Fig 1, an apparatus and method for enhancing growth of a plant crop in a greenhouse (or other controlled environment) is described.
Fuel gas (18) together with air containing oxygen (57) is combusted in a combustion device (10) which in this embodiment is an internal combustion O engine The products of combustion are exhaust gases (20) containing carbon dioxide, water vapour and heat. Additional heat from a cooling circuit (64) associated with the internal combustion engine (12) is also obtained.
SOne or more carbon dioxide sensors (30) detect the level of carbon dioxide in the greenhouse. Carbon dioxide is an essential ingredient of the photosynthesis of plants. By optimising the carbon dioxide level, in the presence of water and sunlight, plants will grow and produce oxygen as a product of photosynthesis. The rate at which the fuel gas (18) is combusted in the internal combustion engine (12) is controlled in order to increase or decrease carbon dioxide levels to a selected, predetermined and optimal level for a given plant crop Carbon dioxide controls and adjustment hence form the first control loop in the control loop hierarchy.
When humidity levels are below the desired predetermined level, as detected by one or more humidity sensors the water spray control (29) supplies increased water through nozzles (98) to the plant crop When humidity levels as detected by the humidity sensor (32) are increasing above the desired predetermined level, less water is sprayed (98) onto the crops The fail safe state for humidity water spraying is to stop watering.
In the instance where no water is being supplied and humidity levels remain above the desired level, secondary humidity control may operate.
Secondary control of humidity is provided by adjusting the level of water vapour from the exhaust. gases (20) supplied to the crops. The products of combustion, hereinafter referred to as the exhaust gases (20) containing carbon dioxide, heat and water vapour are passed through a heat exchanger The exhaust gases may be cooled, causing some of the water vapour in the exhaust gases (20) to condense as a liquid This liquid is pumped (27) to a water storage which may be also fed from a mains or other water reservoir supply O When humidity levels are lowering below the desired predetermined level, C the refrigeration circuit (60) associated with exhaust heat exchanger (22) does not operate, unless called up by the temperature control loop. However, when humidity levels are increasing above the desired levels, a larger amount of water is condensed from water vapour in the exhaust gases This occurs in heat exchanger (22) in co-operation with refrigeration circuit By increasing the Irefrigeration, more water vapour is condensed to liquid water (26) and a drier, cooler, exhaust stream (24) is provided to the greenhouse atmosphere and crops The fail safe state of this secondary control loop is for full refrigeration.
ITemperature in the greenhouse atmosphere is determined by one or Smore temperature sensors (36) detecting the temperature and responding to the temperature detected by controlling the level of refrigeration provided by refrigeration circuit (60) to exhaust heat exchanger (22).
When the temperature is lowering below the predetermined desired temperature, refrigeration in refrigeration circuit (60) is decreased, resulting in a warmer flow of exhaust gases (24) to the greenhouse atmosphere When temperatures are increasing above the desired predetermined level, refrigeration in refrigeration circuit (60) is increased. The fail safe state for this circuit is for full refrigeration.
A secondary temperature control loop controls waste heat via diverter (84).
Waste heat is obtained from the internal combustion engine (12) in two ways.
Firstly, heat is rejected from the internal combustion engine (12) via cooling circuit (64) and heat exchanger to become warm air A second source is waste heat which may be rejected from the refrigeration circuit (60) when refrigeration circuit (60) is operating. The heat carried by the refrigeration circuit is from the exhaust heat exchanger (22).
The heat rejected from refrigeration circuit (60) as warm air is combined with warm air (80) to form a single source of warm air, passing through diverter From diverter warm air may be supplied into the greenhouse or made available for external use as warm air via path The diverter may be modulated so that a proportion of the warm air is supplied into the greenhouse and the remainder carried to external uses.
O This secondary temperature control loop provides additional heat to the C greenhouse when maximum heat energy from the exhaust stream (20) is already Sbeing utilised, i.e. that refrigeration via heat exchanger (22) is not taking place (and hence, that the second source of waste heat is not available).
However, when additional heat for the greenhouse is not required, and refrigeration circuit (60) is in operation, the control circuit ensures that as much as Ipossible of the total waste heat is available for external use as warm air via path 0o The fail safe state for this control loop is to stop heat flow into the greenhouse.
SOne or more oxygen sensors (34) detect the level of oxygen in the c greenhouse atmosphere and a diverter (50) (preferably a modulated two way air control valve) selectively sources air for combustion in internal combustion engine (12) from either or both of fresh air (54) and greenhouse return air (52) in the required proportions. Optionally, an air filter (56) is provided. By adjusting the source of combustion intake air the oxygen level in the greenhouse is adjusted. The fail safe state for oxygen control is to source air from outside fresh air (54).
The plant crops produce oxygen as a result of the photosynthesis process, and therefore act as a source of oxygen inside the greenhouse However, when it is desired to increase the levels of oxygen in the greenhouse above the amount produced by plants, a fresh air inlet fan (not shown) may be operated. In order to balance total fresh air intake, a pressurised vent (58) is also provided. It may be necessary to increase oxygen levels in the greenhouse, for example for maintenance purposes, or in an emergency situation.
In order to ensure the greenhouse is safe in commercial applications, automatic links to prevent human occupancy when greenhouse atmosphere falls outside safe levels for humans are provided and include a personnel entry restriction system, a minimum of two access doors, fail safe ingress restriction door locks, emergency exit doors and movement sensors, internal and external system purge, fail safe emergency stop push buttons, intrusion and an unauthorised access alarm including a fail safe auto purge system.
Preferably, the compressor for refrigeration circuit (60) is driven by internal combustion engine which also drives an alternator (76) generating AC O power The generated power may be used internally to power UV lighting N sensors, pumps and other auxiliary equipment, or if power is generated excess to requirements, the power may be supplied back to an external power grid. Where insufficient power is generated, the electrical system may draw power from the external grid or from an uninterruptible power supply (UPS)(102).
UV lighting levels are detected by one or more UV light sensors (38) and IN UV lighting (96) is increased when UV levels are lowered below the desired 00 predetermined levels and are decreased when UV lighting increases above the desired predetermined level. Accordingly, UV levels may be held constant Idespite variations in the natural UV light (97) due to clouds or the day/night cycle, or alternately levels may be programmed and adjusted in accordance with a desired predetermined schedule. The fail safe state for UV lighting control is to stop providing artificial UV lighting.
Soil saturation is detected by one or more soil saturation sensors (40) and when soil saturation levels are lowering below the desired predetermined value, irrigation to the crops is increased. When soil saturation is increasing above the desired predetermined level, irrigation supplies to the crops may be decreased.
The fail safe state for irrigation is to stop irrigation.
If for any reason, the fuel gas conversion process is stopped, power is made available from uninterruptible power supply (UPS)(102) and/or the external power grid, in order to retain control of the watering and UV lighting levels within the greenhouse. A temperature interlock may also be provided to automatically open wall and roof mounted ventilation flaps in the event of excessive greenhouse temperature. Preferably, these flaps are mechanically fail safe and during a power disruption will default to the open position.
Further preferred embodiments of the invention including a fuel cell stack and a gas turbine which are shown in Figures 2 and 3. These embodiments of the invention operate according to the same control hierarchy and differ schematically only as necessary to account, for example, for the fact that a fuel cell does not produce shaft work, but rather directly produces electricity. In all of the embodiments, the fuel conversion apparatus, (whether combustion or consumption by a fuel cell) is controlled to produce a desired output of CO2, with Sother by-products of this process being utilised in as efficient manner as possible Sby the subsidiary control loops in the hierarchy.
Table 1, below, summarises the control loops in their order of precedence.
The control loop hierarchy ensures control stability as the loops interact (constructively and interferingly) with each other within the greenhouse environment. Using this hierarchy of controls, it is possible to optimise the oO greenhouse energy usage when high or low heating loads are required. The Scontrol loop hierarchy maximises the availability of surplus heat and power for Suse external to the greenhouse, thereby reducing waste and increasing efficiency.
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C Table 1 Loop Measurement Lowering Increasing Fail Safe State 1 002 Increase fuel gas Decrease fuel gas Stop fuel gas 2 Humidity sprays Increase watering Decrease watering Stop watering 3 Humidity-exhaust HE No action Increase refrigeration Full refrigeration 4 Temp exhaust HE Decrease refrigeration Increase refrigeration Full refrigeration Temp waste heat Increase heat flow Decrease heat flow Stop heat flow 6 Oxygen Decrease GH return Increase GH return Stop GH return 7 UV light Increase UV lighting Decrease UV lighting Stop UV lighting 8 Soil Saturation Increase irrigation split Decrease irrigation split Stop irrigation "Lowering" refers to greenhouse sensor readings below the desired level (value). "Increasing" refers to greenhouse sensor readings beyond the desired level (value).
Hence, when COz2 levels are increasing beyond the desired level, the control system response is to decrease fuel gas supply. A cascading effect on other factors may occur and each factor is controlled in order of control loop hierarchy. By controlling each loop in correct order of precedence, destabilising effects on a factor having a more senior position in the hierarchy are avoided, ensuring stable and reliable operation and constant control of greenhouse conditions.
It is highly desirable to have at least two or more sensors installed for each of the factors to be controlled, as a single point of failure can be catastrophic for O greenhouse stock. The failure modes for each of the control loops cover Sinstrument failure, power failure and/or mechanical failure.
The control system, incorporating a hierarchy of control loops, is preferably monitored and operated by a local control screen and activation panel, from a personal computer over standard Ethernet or over the internet utilising TCPIP.
The word "loop" may be described by measurement of an existing process 11level (Process Variable PV), mathematical assessment of the existing process 0o 0 level and its rate of change against the desired process level (Set Point SP) N using a PID algorithm, and controlling a real world output (Output Variable OV) to alter the operation of devices in such a way as to achieve the desired process c level.
All loops are performed by software controlled process control performing PID algorithms (Proportional, Integral, Derivative). This provides independent control of responsiveness full attainment of desired level and predictive modification for each loop. The loops are configured to individually optimise response times relative to the physical response of the greenhouse as measured by the various instruments, while avoiding unstable control or hunting as various loops interact with each other. Hence undesirable control system behaviours are avoided, while the total energy supplied in to the greenhouse is utilised as efficiently as possible, and that portion of the energy which cannot be immediately utilised is made available for uses outside the greenhouse.
Claims (34)
1. An apparatus for enhancing plant growth, in a greenhouse or other controlled environment, including: a carbon dioxide sensor for detecting carbon dioxide levels in the greenhouse; and I- a device for combusting or consuming a fuel gas to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; wherein the carbon dioxide level in the greenhouse is maintained at a selected Ipredetermined level by supplying the exhaust gases into the greenhouse and adjusting the rate of combustion or consumption of the fuel gas in response to the carbon dioxide level detected.
2. An apparatus for enhancing plant growth according to claim 1 wherein the device is a combustion device and is one of an internal combustion engine or a turbine.
3. An apparatus for enhancing plant growth according to any one of the preceding claims further including: a humidity sensor for detecting humidity levels in the greenhouse; and a water supply system; wherein humidity and overall watering in the greenhouse is maintained at a selected predetermined level by adjusting the supply of water.
4. An apparatus for enhancing plant growth according to claim 3 wherein the water is supplied as a direct spray, misting, or as irrigation.
An apparatus for enhancing plant growth according to claim 3 or 4 further including a secondary means of maintaining humidity and overall watering in the greenhouse at the selected predetermined level, said secondary means operating only when humidity is increasing above the selected predetermined level.
6. An apparatus for enhancing plant growth according to claim 5 further including: an exhaust gas heat exchanger for adjusting the temperature of the exhaust gases; wherein the humidity level in the greenhouse is maintained at the selected predetermined level by adjusting the temperature of the exhaust gases in response to the humidity level detected, in order to condense some or all of the water vapour to a liquid, and supplying the remaining exhaust gases into the greenhouse, thereby adjusting the humidity of the greenhouse. 00
7. An apparatus for enhancing plant growth according to any one of claims 3 to 6 wherein water is supplied from a reservoir or mains. IND
8. An apparatus for enhancing plant growth according to one of claims 3 to 7 further including: a temperature sensor for detecting the temperature in the greenhouse; wherein the temperature in the greenhouse is maintained at a selected predetermined level using heat rejected from the exhaust gases by passing the gases through the exhaust gas heat exchanger, the rejected heat supplied into the greenhouse in response to the temperature detected.
9. An apparatus for enhancing plant growth according to claim 8 when appended through claim 2 further including a refrigeration circuit associated with the exhaust gas heat exchanger, the refrigeration circuit including a compressor driven by the combustion device and wherein the heat rejected from the refrigeration circuit is used to heat return air from the greenhouse, to provide a warm air stream which may selectively be supplied into the greenhouse, or used for a purpose external to the greenhouse.
An apparatus for enhancing plant growth according to claim 8 or 9 wherein the device has a cooling circuit with an associated cooling circuit heat exchanger and wherein return air from the greenhouse is passed through the cooling circuit heat exchanger to become warmed air which is then supplied as additional greenhouse heating.
11. An apparatus for enhancing plant growth according to claim 10 wherein warmed air from the cooling circuit heat exchanger is combined with warm air O obtained from heat rejected by the refrigeration circuit and controlled as a single N additional source of greenhouse heating.
12. An apparatus for enhancing plant growth according to any one of claims 8 _to 11 further including: an oxygen sensor for detecting oxygen levels in the greenhouse; and IN a modulated two-way air control valve controllable to selectively feed 00 fresh air from outside the greenhouse and/or return air from inside the greenhouse to the combustion device for combustion of the fuel gas; IN wherein the oxygen level in the greenhouse is maintained at a selected 0predetermined level by controlling the source of air fed to the combustion device in response to the oxygen level detected.
13. An apparatus for enhancing plant growth according to claim 12 wherein data from the oxygen sensor is also used to control a fresh air fan which assists in venting the greenhouse atmosphere and replacing the atmosphere with outside fresh air.
14. An apparatus for enhancing plant growth according to any one of the preceding claims further including a locking apparatus such that humans are prevented from entering the greenhouse when conditions are hostile.
An apparatus for enhancing plant growth according to claim 14 wherein the locking apparatus is an interlock preventing the greenhouse door from being opened from the outside when the carbon dioxide level is above a safe level.
16. An apparatus for enhancing plant growth according to any one of claims 13 to 15 further including an emergency venting arrangement and motion sensors to detect a human or animal presence in the greenhouse.
17. An apparatus for enhancing plant growth according to any one of the preceding claims further including: an ultra violet sensor for detecting ultra violet lighting level in the greenhouse; and O ultra violet lighting; Swherein the ultra violet lighting level in the greenhouse is maintained at a selected Spredetermined level by controlling the ultra violet lighting and adjusting the ultra violet lighting in response to the ultra violet lighting level detected.
18. An apparatus for enhancing plant growth according to any one of the preceding claims further including an alternator driven by the device to generate 00 electrical power for powering the control systems and sensors for the apparatus and other auxiliary equipment. IND
19. An apparatus for enhancing plant growth according to claim 18 wherein any power generated excess to requirements is fed back to a mains power grid or stored for later usage.
An apparatus for enhancing plant growth according to any one of the preceding claims further including: a soil saturation sensor for detecting soil saturation levels in the greenhouse; and irrigation means for supplying water to said soil; wherein the soil saturation level is maintained at a selected predetermined level by supplying water to the soil in response to the soil saturation level detected.
21. An apparatus for enhancing plant growth according to any one of claims 1, 3 to 8 or 10 to 20 wherein the device is a fuel cell.
22. An apparatus for enhancing plant growth according to claim 21 when appended through claim 8 further including a refrigeration circuit associated with the exhaust gas heat exchanger, the refrigeration circuit including a compressor powered by the fuel cell and wherein the heat rejected from the refrigeration circuit is used to heat return air from the greenhouse, to provide a warm air stream which may selectively be supplied into the greenhouse, or used for a purpose external to the greenhouse. O
23. A method for enhancing plant growth including the steps of: S- combusting a fuel gas in a combustion device or consuming a fuel gas in Sa fuel cell to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; supplying the exhaust gases into the greenhouse; detecting the carbon dioxide level in the greenhouse using a carbon Idioxide sensor; 00 and adjusting the rate of combustion of fuel gas to adjust the carbon cdioxide level in the greenhouse.
24. A method for enhancing plant growth according to claim 23 including the subsequent steps of: detecting the humidity level in the greenhouse using a humidity sensor; supplying water for the greenhouse as a spray, mist or irrigation thereby adjusting the humidity level in the greenhouse in order to maintain a selected predetermined humidity level.
A method for enhancing plant growth according to claim 24 further including a secondary humidity method applicable only when humidity is increasing above the selected predetermined level, including the subsequent steps of: adjusting the temperature of the exhaust gases in order to condense some or all of the water vapour to a liquid and supplying the remaining exhaust gases into the greenhouse, thereby adjusting the humidity level in the greenhouse in order to maintain a selected predetermined humidity level.
26. A method for enhancing plant growth according to any one of claims 24 to including the subsequent steps of: detecting the temperature in the greenhouse using a temperature sensor; adjusting the temperature of exhaust gases using an exhaust gas heat exchanger thereby adjusting the temperature in the greenhouse in order to maintain a selected predetermined temperature.
S27. A method for enhancing plant growth according to claim 26 including a secondary temperature control method including the subsequent steps of: selectively supplying waste heat created by any of the preceding steps into the greenhouse, thereby adjusting the temperature in the greenhouse in order to maintain a selected predetermined temperature.
28. A method for enhancing plant growth according to claim 27 wherein said 00 waste heat may is obtained from a cooling circuit associated with the combustion device or fuel cell, or from heat rejected by passing exhaust gases through the IN exhaust heat exchanger.
29. A method for enhancing plant growth according to any one of claims 26 to 28 including the steps of: detecting the oxygen level in the greenhouse using an oxygen sensor; selectively supplying fresh outside air and/or return air from inside the greenhouse to the combustion device for combustion of the fuel gas or to the fuel cell for consumption of fuel gas, thereby adjusting the oxygen level in the greenhouse in order to maintain a selected predetermined oxygen level.
A method for enhancing plant growth according to any one of claims 23 to 29 including the steps of: detecting the UV light level in the greenhouse using a UV sensor; selectively providing artificial UV lighting, thereby adjusting the UV level in the greenhouse in order to maintain a selected predetermined UV level.
31. A method for enhancing plant growth according to claim 30 wherein the UV lighting is powered by electricity generated by the combustion device.
32. A method for enhancing plant growth according to any one of claims 23 to 31 including the steps of: detecting the soil saturation level using a soil saturation sensor; selectively supplying water to said soil to irrigate; wherein the soil saturation level is maintained at a selected predetermined level by supplying water to the soil in response to the soil saturation level detected. 22 NO O
33. An apparatus for enhancing plant growth, in a greenhouse or other Scontrolled environment, including: a carbon dioxide sensor for detecting carbon dioxide levels in the greenhouse; and a device for combusting or consuming a fuel gas to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; Nwherein the carbon dioxide level in the greenhouse is maintained at a selected predetermined level by supplying the exhaust gases into the greenhouse and Sadjusting the rate of combustion or consumption of the fuel gas in response to the NO carbon dioxide level detected, substantially as hereinbefore described, with Sreference to any one of the embodiments shown in the accompanying Figures.
34. A method for enhancing plant growth including the steps of: combusting a fuel gas in a combustion device or consuming a fuel gas in a fuel cell to produce heat and exhaust gases, the exhaust gases including carbon dioxide and water vapour; supplying the exhaust gases into the greenhouse; detecting the carbon dioxide level in the greenhouse using a carbon dioxide sensor; and adjusting the rate of combustion of fuel gas to adjust the carbon dioxide level in the greenhouse, substantially as hereinbefore described, with reference to any one of the embodiments shown in the accompanying Figures. DATED this 17th day of May 2006 JOHN EDWARD NORWOOD WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2006202086A AU2006202086A1 (en) | 2005-05-17 | 2006-05-17 | Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2005902512 | 2005-05-17 | ||
| AU2005902512A AU2005902512A0 (en) | 2005-05-17 | Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) | |
| AU2006202086A AU2006202086A1 (en) | 2005-05-17 | 2006-05-17 | Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| AU2006202086A1 true AU2006202086A1 (en) | 2006-12-07 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| AU2006202086A Abandoned AU2006202086A1 (en) | 2005-05-17 | 2006-05-17 | Method and apparatus for enhancing plant growth in a greenhouse (or other controlled environment) |
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| AU (1) | AU2006202086A1 (en) |
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- 2006-05-17 AU AU2006202086A patent/AU2006202086A1/en not_active Abandoned
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