GB2501533A

GB2501533A - Livestock house ventilation

Info

Publication number: GB2501533A
Application number: GB1207455.5A
Authority: GB
Inventors: Toke Wilson
Original assignee: HYDOR Ltd
Current assignee: HYDOR Ltd
Priority date: 2012-04-26
Filing date: 2012-04-26
Publication date: 2013-10-30
Anticipated expiration: 2032-04-26
Also published as: GB201207455D0; GB2501533B

Abstract

A live stock house ventilation system 12 compromising a sensing device 16 for monitoring the level of carbon dioxide in the house, a ventilation arrangement for introducing a controlled amount of external atmospheric air into the house and a controller 15 configured to signal operation of the ventilation arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation. The system preferably includes a radiant heater 18 and a heat exchanger to recover heat from the exhausted air. The ventilation arrangement can be a discrete device 20 which introduces air via an opening in the side wall of the housing 10 and expels air via another opening.

Description

A Livestock House Ventilation System and Method

FIELD OF THE INVENTION

The present invention relates to a livestock house ventilation system and method, in particular, but not exclusively, in relation to pouitry houses.

BACKGROUND OF THE INVENTION

Poultry, for example chickens, raised for meat production are commonly reared in large houses or sheds containing up to 50,000 birds. k order for the birds to be healthy, and therefore put on weight rapidly and efficiently, the temperature and ventilation of such houses should be controlled.

However, control of ventilation has hitherto been carried out by rather imprecise methods. Typically, for chickens it is assumed that 1m3 of fresh air/hr/kg of birds within the house is needed for sufficient ventilation. Broiler chickens typically weigh 40g on the day they are introduced into a house, and will have grown to 500g by day 10. and will be 2kg at day 35 when ready for slaughter. Therefore, at the start of one bird production cycle, fans may be turned on for 10 seconds and then switched off for seconds, for example. As the birds mature, assumptions are made as to their weight gain and the cycling of fans on and off will be altered so that fans are switched on for a longer period and turned off for shorter periods progressively.

As growth rates may be lower or higher than anticipated by the farmer, there is a danger that the carbon dioxide (CO2) concentration in the air within the house exceeds optimal levels, meaning that the health and growth rate of the birds is impaired.

Conversely, the ventilation may be excessive, resulting in increased electricity and heating costs (typically increased gas consumption in order to maintain a desired temperature when ventilation with cold, fresh air is increased).

A typical maximum desirable concentration of carbon dioxide in the atmosphere of a house is 3,500 parts per million (ppm). Above this level, the feed conversion ratio of the birds is impaired. In other words, a greater mount of feed is consumed by a bird in order to gain a unit of mass. This inevitably increases the production cost of birds and is therefore undesirable.

In the first 14 days typically of a given production cyde, there is (in temperate climates) typically a requirement for a net supply of heat energy into a poultry house because the relatively immature birds do not generate sufficient heat of their own, and need to be maintained at a suitably high temperature to optimise their development.

Typically, at day one a temperature of 32°C is desirable and this requirement will reduce to say 28.5°C at day 14. Therefore, it is common for blown air gas burners to be used to heat the air of the house to maintain this temperature. Disadvantageously, such blown air burners also expel the carbon dioxide generated in the combustion of the gas into the house therefore increasing the carbon dioxide concentration.

Beyond 14 days. the birds typicafly generate more heat themselves than is required to maintain the house at an optimal temperature for their age, and generally the atmosphere in the house requires cooling, rather than heating. Typically this optimal temperature will decline to 22°C at day 35. Cooling the chicken house is generally achieved with forced ventilation by the use extract fans and air inlet flaps. The extract fans force out the hot air inside the chicken house, and consequently fresh cooler outside air is drawn in through the air inlets, to maintain the required temperature. In the cooling phase of a crop of chickens, high carbon dioxide is usually less of an issue because greater levels of forced ventilation are required for the cooling.

The present applicant has therefore recognised that it is desirable to overcome or at least mitigate one or more of the problems of known ventilation systems and methods.

SUMMARY OF THE INVENTION

Accordingly one aspect of the present invention provides a livestock house ventilation system comprising: a) a sensing device for monitor ng the level of carbon dioxide in the house; b) a ventilation alTangernent for introducing a controlled amount of external atmospheric air into the house; c) a controller configured to signal operation of the ventilation arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.

This ensures ventilation is optimal at all times -not too much as that would waste electrical and heat energy, and not too Uttle to starve the livestock of fresh air.

Preferred embodiments of the present invention are descnbed in the described in the dependent claims.

A second aspect of the present invention provides a ventilation device configured to ventilate a livestock house, the device comprising: a) an input from a sensing device for monitoring the level of carbon dioxide in the house; b) an air management arrangement for introducing a controlled amount of external atmospheric air into the house; and c) a controfler configured to signal operation of the air management alTangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.

A third aspect of the present invention provides a method of controlling ventilation in a livestock house, comprising the steps of: a) monitoring the level of carbon dioxide in the house; b) signalling operation of a ventilation arrangement in response to the level of carbon dioxide sensed so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of examp'e only. with reference to the accompanying drawings, in which: FIGURE 1 is a schematic plan view of a poultry house incorporating a ventilation system according to an embodiment of the present invention; FIGURE 2 is a side view of a ventilation device of a ventilation arrangement that forms part of the ventilation system of Figure 1 FIGURE 3 is a front view of the device of Figure 2; FIGURE 4 is a plan view of the device of Figure 2; and FIGURE 5 is a flowchart illustrating a control method for controlling the system of Figure 1.

DETAILED DESCRIPTION OF EMBODIMENTS

In broad terms, the present invention provides ventilation system for houses or sheds that contain livestock, including chickens, turkeys and other fowl, as well as other animals reared for meat, eggs, milk, or other products, such as pigs. The invention arises from a recognition that CO2 monitoring can be used as part of a closed loop control system to improve the efficiency of ventilation and heating. As such, the system typically requires a sensing device for monitoring the level of carbon dioxide in the house, a ventilation arrangement for introducing a controlled amount of external atmospheric/fresh air into the house and some form of controller, such as a microprocessor. The controller is configured to signal operation of the ventilation arrangement in response to the level of carbon dioxide sensed by the sensing device to maintain carbon dioxide below a predetermined evel and ensure there is an optimal amount of ventilation -not too much as that would waste electrical and heat energy, and not too little to starve the livestock of fresh air.

S

With reference to Figure 1, a schematic plan view of a typical livestock house, specifically a chicken rearing house or shed 10 which incorporates a ventilation system 12 of the present invention is shown.

S Such houses 10 are usually large portal framed structures that may house 50,000 birds or more. They may be up to 4m in height, and be substantially sealed from the external atmosphere. so that ventilation can be regulated by fans and vents as described in more detail below. The birds are reared on litter that consists of straw or wood shavings or the like. In order that the birds remain healthy. and achieve good condition, it is important that the litter is kept as dry as possiHe, so that production of harmful ammonia from the birds excreta is minimised. Keeping the litter as dry as possible is achieved by ventilation to keep the humidity as low as possible.

In this embodiment, the ventilation system comprises a ventilation anangement of four ventilation devices 20 located substantially evenly around the side walls of the house.

In this embodiment, each ventilation device 20 includes a suitable controller 15, typically a microprocessor controller that is programmed with an algorithm described in more detail below. The system further comprises a sensing device in the form of a carbon dioxide sensor 16, which is linked to each controller 15 by a hardwired signal cable 19. In alternative embodiments a wireless link using a suitable protocol such as IEEE 802.1 la, b, g or n, Zigbee. or Bluetooth may alternatively be used.

The controllers 15 control operation of each device 20 in response to the parameter of at least CO2 sensed by the sensor 16.

There is a heat source in the form of a radiant heater 18, which in this embodiment has its own control system in the form of a thermostat-type temperature sensor 14 connected thereto by a separate signalling cable 17 and therefore separate from the system of the present invention.

In other embodiments, a single central controller (not shown) may control operation of all ventilation devices 20 and in still further variants, each ventilation device 20 may be provided with its own CO2 sensor and its own temperature sensor aiong with its own controller 15. In further variants, the central controller or device controller 15 may individually control one or more heaters, instead of the heaters being operated by a separate control system. The system may additionally comprise a humidity sensor, that provides an input, either into the controller(s) 15 of the ventilation devices, or the central controller. The system may include further sensors such as temperature and humidity sensor for the external atmosphere, so as to provide further information that may be used by the controller optimise the control strategy.

Turning now to Figures 2, 3 and 4, a ventilation device 20 is illustrated in more detail.

It can be seen that the ventilation device 20 includes a main housing 30 suspended on legs 32. Substantially parallel air extraction and supply ducts 34, 36 extend from a face of the main body 30 and are intended to connect with corresponding openings (not shown) in a side wall of the house lO. The main housing 30 and ducts 34 and 36 contain an air management arrangement that enables fresh air to be introduced into the house 10 In this embodiment, the air management arrangement includes a fan 40 to draw stak air from the house 10 into the air extraction duct, and a supply fan 46 in the supply duct to drive fresh air into the house 10.

The extraction duct 34 further comprises a filter 38 at the inlet thereto together with the fan 40 to draw air into the duct 34. A flexible connection 42 is provided between inlet housing the fan 40 and filter 38 and the remainder of the duct in order to accommodate any slight misalignment between the openings in the side wall of the house 10.

The supply duct 36 comprises a similar flexible connection 44 between a main portion of the duct and an outlet section that houses the supply fan 46 and also a damper with aerofoil blades 48.

The main housing 30 of the ventilation device 20 further includes a fresh air intake 50 and an exhaust air exit 52 in a lower portion thereof A heat exchanger. preferably a plate-type heat exchanger 54, is mounted substantially centrally within the main housing 30 at an upper portion thereof. Warm, stale air is extracted from the house 10, being driven by the fan 40 and is directed into an inlet of the heat exchanger 54 on a path indicated schematically by arrow 56. The air is then fed via a tortuous path within the heat exchanger 54 and out through the exhaust air exit 52 as indicated by arrow 58.

At the same time, fresh atmosphenc air is drawn into another inlet of the heat exchanger 54 from the fresh air intake 50 via a path indicated schematically by arrow 60. The fresh air then feeds through a reverse tortuous path within the heat exchanger 54 and out through the supp'y duct 36 via a path indicated schematically by arrow 62 under the influence of fan 46. The fresh supply air is then directed over an arc by the reciprocating action of the damper 48.

The filter 38 at the entrance to the extraction duct 34 prevents dust and other foreign matter from entenng the duct and therefore also from clogging the heat exchanger, impairing its function.

As the warm, stale air extracted from the house 10 passes through the heat exchanger 54 simultaneously with the fresh cooler from the atmosphere, the heat energy of the extracted air is transferred to the fresh supply air. This prevents a significant proportion of the heat going to waste. However, the heat exchanger arrangement ensures that air high in CO2 is removed and replaced with air low in CO2.

As such the supply air remains low in CO2 but is supplied to the house 10 in at an elevated temperature compared to the atmospheric air, therefore minimising the artificial heating required in the house from the radiant heater 18. It is believed that an efficiency of 60% or more in heat recovery is achievable with a heat exchanger of this type. Therefore there is a significant saving in energy costs from a reduced need for radiant (or other) heaters 18. Locating the devices 20 outside the house provides for ease of installation and access for maintenance.

With reference now to figure 5, one embodiment of the control system function is illustrated in a flow chart. At the start of the process, the controller 15 substantially determines the level of carbon dioxide in the house 10 by monitoring the signals emitted by the sensor 16 and compares these with a predetermined acceptable range at steps S100 and S 102. In this embodiment the acceptable range for CO2 is between 2,500 and 3,000 parts per million, but may vary dependent upon the species of animal and age, for example.

If at step Sl00 the controller determines the concentration of CO2 is too high, it signals the ventilation device(s) 20 to increase the rate of ventilation by 5% at step SI 04. If, on the other hand, the concentration of CO9 is deemed to be too low (i.e. an excess of fresh air is introduced thus increasing ventilation and possibly heating costs) the ventilation is decreased by 5% at step S106. Once this ventilation rate has been changed, the controller IS then waits a further 60 seconds at step 5107 before returning to the start of the algorithm and again measuring CO2. If at step Sl00 CO2 concentration is within the acceptable range, the controller 15 simply waits 60 seconds at step S107 before measuring it again.

In this embodiment, the heater 18 operates separately under the influence of the thermostat temperature sensor 14. This is programmed with a timer to lower the threshold temperature at which the heater is switched on as the age of the birds increases. In one variant the thermostat is a simple manually set device that a farmer adjusts on a regular basis to account for aging of the birds.

The acceptable range for temperature is dependent upon the age of the birds within the house. When they are first introduced it may, in this embodiment, be within the range of 33 to 31°C, reducing to between 29 and 27°C at day 14.

Of course, if the control method is implemented with the ventilation system 12 described above, a large proportion of the heat extracted from the house 10 is transferred to the supply air, thereby reducing the requirement for use of the heaters 18. In other words the temperature drops below the threshold at which the heater is switched on less frequenfly.

In a preferred embodiment, the controller 15 is programmed to signal the extraction fan 40 to be periodically reversed to blow dust accumulated in the filter 38 back into the house in order to maintain a suitable flow rate. This may occur on a timer in some vanants, or in response to a measured reduction in flow or pressure drop in others.

This is advantageous over systems that require the filter to be washed, thus leaving the farmer with the issue of how to dispose of the polluted waste-water.

For the heat exchanger to function satisfactonly, a constant minimum flow rate of inlet and exhaust air is required. This is typically of the order of 20% of maximum flow rate, but may vary from heat exchanger to heat exchanger.

The system may include a suitable input to adjust operation thereof, and a display to output suitable information -for example both could be combined in a touchscreen interface (not shown), or the system may have a webpage based interface and be controlled remotely by a computer.

A further advantage in using heat exchangers of the present invention, coupled with radiant heaters rather than gas fired blown air heaters is in minimising humidity in the house 10. Buming gas emits water vapour in the exhaust, which is blown into the house, so minimising the need for gas fired heaters reduces the water vapour in the house. In addition, radiant gas heaters are typically more efficient than blown air heaters, since they are directed so as to heat the ground only, meaning that water vapour emissions are further reduced. This may improve bird welfare by reducing the generation of ammonia and the like.

In the control system variant described above, in which a central controller controls directly or indirectly the heater 18 and the ventilation devices 20 for the house 10, further control strategies become possible. For example, where humidity is also being monitored by the central controller, the ventilation devices alone, the heater alone, or a blended combination of heating and ventilation can be employed to ensure that humidity as well as CO2 does not exceed a threshold value. Algorithms to implement this may be optimised further if external atmospheric humidity is also known, because if this is low, higher ventilation rates may be more effective at lowering humidity, whereas if atmospheric humidity is high, increased heating may be more effective.

As explained above, it is anticipated that the control system described above will be particularly applicable within around the first 14 days of (chicken) bird rearing within a house, when there is usually a net requirement for heating. However this may vary by climate, as well as by the species of anima' being reared.

It will be appreciated that numerous changes may be made within the scope of the present invention. For example. the timings and ventilation increments may be altered from those described. An alternative layout of ventilation device may be employed.

For example a single unit may be provided for each house on a farm, or indeed for a whole farm, with suitable ducting to supply fresh air and remove stale air, and a suitable control system to sense CO2 and temperature and provide heating and ventilation as needed. Suitable alternative types of heat exchanger may be used. The ventilation alTangement may incorporate a ground source or air source type heat pump and low solar heating to further minimise energy needs. The ventilation arrangement may further include a dehumidifier and or refrigeration system. Multiple sensors for each parameter may located around a house and the results averaged by the controller, or the control strategy may be based on the most extreme value measured. Multiple heaters may be located around the house so as to provide a substantially even heating thereof.

Claims

Claims I. A livestock house ventilation system comprising: a) a sensing device for monitoring the level of carbon dioxide in the house; b) a ventilation arrangement for introducing a controlled amount of external atmospheric air into the house; c) a controller configured to signal operation of the ventilation arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.
2. A livestock house ventilation system according to claim I wherein the ventilation alTangement further includes a heating device.
3. A livestock house ventilation system according to claim I or claim 2 wherein the ventilation arrangement is further configured to recover heat energy from being expelled from the house as fresh air is introduced.
4. A livestock house ventilation system according to claim 3 when dependent upon claim 2 wherein the heating device is configured to transfer at least a proportion of the recovered heat energy to the fresh air as it is introduced.
5. A livestock house ventilation system according to claim 4 wherein the heating device comprises a heat exchanger.
6. A livestock house ventilation system according to any preceding claim wherein the ventilation arrangement comprises a fan.
7, A livestock ventilation system according to claims 2 to 6 wherein the heating device comprises a radiant heater.
8. A livestock ventilation system according to claims 2 to 7 wherein the heating device comprises a blown air heater.
9. A livestock ventilation system according to any preceding claim wherein the ventilation arrangement introduces atmosphere air via an opening in the side wall.
10. A livestock ventilation system according to any preceding claim wherein stale air expelled from the house is vented via an opening in the side wall.
11. A livestock ventilation system according to claim 10 when dependent upon claim 9 wherein the ventilation alTangement includes a heat exchanger and is located adjacent the side wall to connect to the openings for introducing atmospheric air and expelling stale air.
12. A livestock ventilation system according to any preceding claim wherein the system is configured to commence ventilation wherein the carbon dioxide concentration within the house is detected to exceed 4.000ppm. preferably 3,500 ppm.even more preferably 3,000ppm.
13. A livestock ventilation system according to any preceding claim wherein once a predetermined level of carbon dioxide is detected the ventilation arrangement is signalled to operate at an increased rate.
14. A livestock ventilation system according to claim 13 wherein after a predetermined period the carbon dioxide remains higher than the predetermined level, the ventilation arrangement is signalled to operate at a still higher rate.
15. A livestock ventilation system according to claim 14 wherein the ventilation arrangement comprises a heat exchanger and the arrangement is configured to operate when in service substantially constanfly at a minimum rate, and when an increased level of carbon dioxide is detected the increase is from this minimum rate.
16. A ventilation system according to any preceding claim wherein the ventilation anangement is located within at least one discrete ventilation device having an air management anangernent for introducing the controfled amount of external atmospheric air into the house.
17. A ventilation system according to claim 16 wherein the at least one ventilation device further comprises a controller.
18. A ventilation device configured to ventilate a livestock house, the device comprising: a) an input from a sensing device for monitoring the level of carbon dioxide in the house; b) an air management arrangement for introducing a controlled amount of external atmospheric air into the house; and c) a controfler configured to signal operation of the air management arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.
19. A method of controlling ventilation in a livestock house, compnsing the steps of: a) monitoring the level of carbon dioxide in the house; b) signalling operation of a ventilation arrangement in response to the level of carbon dioxide sensed so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation.Amendments to the claims have been filed as follows Claims I. A ventilation system for a livestock house having side walls, the system comprising: a) a sensing device for monitoring the level of carbon dioxide in the house; b) a ventilation arrangement for introducing a controlled amount of external atmospheric air into the house; c) a controller configured to signal operation of the ventilation arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxidc bclow a prcdctcrmincd level and minimise thc requirement for venfflation wherein the ventilation arrangement introduces atmospheric air via an opening in the side wall; 0) 15 wherein stale air expelled from the house is vented via an opening in the side wall; and 0) wherein the ventilation arrangement includes a heat exchanger, configured to transfer at least a proportion of the recovered heat energy fltm the stale air to the atmospheric air as it is introduced, and the ventilation arrangement is located adjacent the side wall to connect to the openings for introducing almospheric air and expelling stale air.2. A livestock house ventilation system according to claim 1 wherein the ventilation arrangement further includes a heating device.3. A livestock house ventilation system according to any preceding claim wherein the ventilation arrangement comprises a fin.4. A livestock ventilation system according to claims 2 to 3 wherein the heating device comprises a radiant heater.5. A livestock ventilation system according to claims 2 to 3 wherein the heating device comprises a blown air heater.6. A livestock ventilation system according to any preceding claim wherein the system is configured to commence ventilation when the carbon dioxide concentration within the house is detected to exceed 4,000ppm.7. A livestock ventilation system according to claim 6 wherein the system is configured to commence ventilation when the carbon dioxide concentration within the house is detected to exceed 3,500 ppm.8. A livestock ventilation system according to claim 14 wherein the system is configured to commence ventilation when the carbon dioxide concentration within the house is detected to exceed 3,000 ppm.9. A livestock ventilation system according to any preceding claim wherein once a C') is predetermined level of carbon dioxide is detected the ventilation arrangement is signalled to operate at an increased rate. C')10. A livestock ventilation system according to claim 9 wherein after a predetermined period the carbon dioxide remains higher than the predetermined level, the ventilation arrangement is signalled to operate at a still higher rate.11. A livestock ventilation system according to claim 10 wherein the ventilation arrangement is configured to operate when in service substantially constantly at a minimum rate, and when an increased level of carbon dioxide is detected the increase is from this minimum rate.12. A ventilation system according to any preceding claim wherein the ventilation arrangement is located within at least one discrete ventilation device having an air management arrangement for introducing the controlled amount of external atmospheric air into the house.13. A ventilation system according to claim 12 wherein the at least one ventilation device further comprises a controller.14. A ventilation device configured to ventilate a livestock house having side walls, the device comprising: a) an input from a sensing device for monitoring the level of carbon dioxide in the house; b) an air management arrangement for introducing a controlled amount of external atmospheric air into the house; c) a controller configured to signal operation of the air management arrangement in response to the level of carbon dioxide sensed by the sensing device so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation; d) an air supply duct, configured to conncct with a corrcsponding opening in the side wall; e) an air extracting duct to remove stale air, configured to connect with a C') is corresponding opening in the side wall; and a heat exchanger, connected to the openings for introducing atmospheric C') air and expelling stale air, configured to transfer at least a proportion of the recovered heat energy from the stale air to the atmospheric air as it is introduced.15. A method of controlling ventilation in a livestock house utilising a livestock ventilation system or ventilation device according to any previous claim, comprising the steps of: a) monitoring the level of carbon dioxide in the house; b) signalling operation of the livestock ventilation system or ventilation device in response to the level of carbon dioxide sensed so as to maintain carbon dioxide below a predetermined level and minimise the requirement for ventilation. sa.