WO2015035468A1

WO2015035468A1 - Soil temperature regulation system

Info

Publication number: WO2015035468A1
Application number: PCT/AU2014/050223
Authority: WO
Inventors: Benjamin David LAMBERT; Justin Peter LAMBERT; Daniel John LAMBERT
Original assignee: Helicool Pty Ltd
Priority date: 2013-09-12
Filing date: 2014-09-10
Publication date: 2015-03-19

Abstract

A system for regulating soil temperature, the system including a heat transfer loop including a buried loop portion that is buried in soil, whereby a heat transfer medium is provided in the heat transfer loop in use, a solar collector thermally coupled to the heat transfer loop, a pump for pumping the heat transfer medium through the heat transfer loop, whereby operation of the pump can cause a heat exchange between the solar collector and the soil, via the heat transfer medium, a soil temperature sensor for sensing a soil temperature in the soil, an external temperature sensor for sensing an external temperature indicative of a temperature in the solar collector and a controller for controlling operation of the pump using the soil temperature and the external temperature so that the pump operates when the heat exchange between the solar collector and the soil will act to reduce a temperature difference between the soil temperature and a predetermined soil temperature, to thereby regulate the soil temperature.

Description

SOIL TEMPERATURE REGULATION SYSTEM Background of the I nvention

(00011 The present invention relates to a soil temperature regulatio system, which may he used, fo example, to regul ate the temperature of soil for planting and growing a crop.

Description of the Prio r Art

[0002] In agriculture, the successful cultivation, of crops can be highly dependent on environmental conditions. For example, many crops can only be grown under certain desirable conditions which can dictate the location and times of the year in which those crops will be cultivated. Even when a crop is planted in a suitable location and in a suitable time of the year, the yield of the crop can var depending on suc factors and temperature and rainfall during the growth of the crop.

[0003] Soil temperature is an important factor as this can impact on seed germination, root growth and nutrient availability. Whilst soil temperatures can be regulated to some extent by providing an insulating cover such as mulch, the traditional approach has been to accept the soil temperature in a give location and select crops suited to the soil temperature and their planting times accordingly.

[0004] Solar soil heating has proven to be effective in areas of crop viability and pest control . However, conventional solar soil heating techniques generally involve solar energy being radiated downwardly into soil, and research has shown that these methods are ineffective for heating soil layers deeper tha about 300 mm. Furthermore, these methods do not typically allow for cooling of th soil .

[0005] Chinese Utility Model No. CN202043502U discloses a topsoil irrigation system which, includes a solar water heater for heating the irrigation water to a suitable temperature for promoting crop growth, The heated water is supplied to the crop roots, and although this wi ll result in some heating of the soil in the vi cinity of the crop roots, in order to maintain an elevated temperature a heated water will need to be continuously supplied. Overwatering concerns will therefore impose practical limitations o the amount of heating that can be achieved. [0006] Australian Innovation Patent No. AU2Q08100203 discloses a solar soil heatirig and cooling system, in which aboye ground solar collectors are connected to underground pipes through whic water is circulated using pumps, to thereby heat or cool the soil. Whilst the system disclosed therein has proved to be effective, further improvements may he realised.

[0007] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specificatio relates.

Summary of the Present Invention

[0008] In a first broad form the present invention seeks to provide a system for regulating soil temperature, the system including;

a) a heat transfer loop including a buried loop portion that is buried in soil, whereby a heat transfer medium is provided in the heat transfer loop in use;

b) a solar collector thermally coupled to the heat transfer loop;

c) a pump for pumping the heat transfer medium through the heat transfer loop, whereby operation of the pump can cause a heat exchange between the solar collector and the soil, via the heat transfer medium;

d) a soil temperature sensor for sensing a soil temperature in the soil;

e) an external temperature sensor for sensing an external temperature indicative of a temperature in the solar collector; and,

f) a controller for controlling operation of the pump using the soil temperature and the external temperature so that the pump operates when the heat exchange between the solar collector and the soil will act to reduce a temperature difference between the soil temperature and a predetermined soil temperature, to thereby regulate the soil temperature.

[0009] Typically the solar collector is connected to the heat transfer loo such that the heat transfer medium can flo through the solar collector,

[0010] Typically the controller is configured to: a) determine, based on the temperature difference, whether heating or cooling of the soil is required;

b) determine, using the external temperature, whether heat exchange between the solar collector and the soil will heat or cool the soil; and,

c) cause the pump to operate if one of:

i) heating of the soil is required and it is determined that heat exchange between the solar collector and the soil will heat the soil; and,

ii) cooling of the soil is required and it is determined that the heat exchange between the solar collector and the soil will cool the soil.

[0011] Typically the controller is configured to only cause operation of the pump if the temperature difference is greater than a predetermined temperature difference threshold.

[0012] Typically the external temperature sensor is positioned proximate the solar collector.

[0013] Typically the system includes a return temperature sensor for sensing a return temperature indicative of a temperature of the heat transfer medium that has flowed through the buried loop portion, the controller being configured to control the pump by comparing the external temperature and the return temperature.

[0014] Typically the controller is configured so that, when the soil temperature is below the predetermined soil temperature, the controller causes operation of the pump when the external temperature is greater tha the return temperature, to thereby cause heating of the soil

[0015] Typically the controller is configured so that, when the soil temperature is above the predetermined soil temperature, the controller causes operation of the pump when the external temperature is less than the return temperature, to thereby cause cooling the soil.

[0016] Typically the controller is configured to cause operation of the pump when a return temperature difference between the external temperature and the return temperature is greater than a predetermined return temperature threshold,

[0017] Typically the system, includes a return tank for storing heat transfer medium that has flowed through the buried loop portion. [0018] Typically the return temperature sensor is provided in the return tank.

[0019] Typically the pum is positioned between the return tank and the solar collector,

[0020] Typically the system includes a pluraiity of soil temperature sensors including at least one of:

a) an upper soil temperature sensor positioned in the soil substantially at a soil surface and proximate the buried loop portion;

b) a buried soil temperature sensor positioned in the soil at a predetermined depth beneath the soil surface and proximate the buried loop portion;

c) a loop soil temperature sensor positioned in the soil at a depth similar to a burial depth of the buried loop portion and proximate the buried loop portion; and,

d) an offset soil temperature sensor positioned in the soil at a depth similar to a burial depth of the buried loop portio and offset from the buried loo portion by a predetermined offset amount,

[0021] Typically the controller is configured to control the pump based on respective soil temperatures sensed by two or more of the plurality of soil temperatures,

[0022] Typically the controller is configured to;

a) determine an average soil temperature using the respective soil temperatures; and, b) control the pump by comparing the average soil temperature with the predetermined, soil temperature.

[0023] Typically the system further includes at least one ambient soil temperature sensor including at least one of:

a) an ambient upper soil temperature sensor positioned in the soil substantially at a soil surface and sufficiently separated from the buried loop portion so as to be .substantially unaffected by heat exchange between the heat transfer medium and the soil; and,

b) an ambient buried soil temperature sensor positioned in the soil at a predetermined depth and sufficiently separated from the buried loop portion so as to be substantially unaffected by heat exchange between the heat transfer medium and the soil. [0024] Typically the controller is configured to control the pump using the at least one ambient soil temperature sensor.

[0025| Typically the system further includes an auxiliary heater connected to the heat transfer loop, whereby, when the auxiliary heater is activated, the heat transfer medium in the heat transfer loop is heated when the heat transfer medium flows through the auxiliary heater.

[0026] Typically the controller is configured to control activation of the auxiliary heater so that the auxiliary heater is activated when th soil temperature is below the predetermined soil temperature and the soil is not being heated using heat exchange between the solar collector and the soil.

[0027] Typically the auxiliary heater includes a heat pump. [0028] Typicall the auxiliar heater is electricaliy powered. [0029] Typically the auxiliary heater is a gas heater.

[0030] Typically the system further includes an auxiliary chiller connected to the heat transfer loop, whereby, when the auxiliary chiller is activated, the heat transfer medium in the heat transfer loop is chilled when the heat transfer medium flows through the auxiliary chiller.

[0031] Typically the controller is configured to control activation of the auxiliary chiller so that the auxiliary chiller is activated when the soil temperature is above the predetermined soil temperature and the soil is not being chilled using heat exchange between the solar collector and the soil.

[0032] Typically the system further includes a valve for controlling the flow of the heat transfer medium through the solar collector.

[0033] Typically the controller is configured to control the valve based on the soil temperature. [0034] Typically the valve has a first valve position for allowing the heat transfer medium to flow through the solar collector and a second vaive position for causing the heat transfer medium to bypass the solar collector,

[0035] Typically the controller is configured to control the valve so that the valve is moved into the second valve position when the soil temperature is below the predetermined soil temperature and the external temperature is less than a return temperature of the heat transfer medium that has flowed through the buried loop portion.

[0036] Typically the controller is a programmable logic controller.

[0037] Typically the controller is configured to receive a input from at least the soil temperature sensor and the external temperature and provide an output to at least pump relay for controlling the pump.

[0038] Typically the system further includes a data logger for logging temperatures sensed by at least one of the temperature sensors.

[0039] Typically the solar collector is installed on a roof of a bui l ding,

[0040] Typically the system further includes a solar power generator for generating electrical power to drive at least the pump.

[0041] Typically the system further includes an energy store for storing energy generated by the solar power generator.

[0042] Typically the solar collector is thermally coupled to the heat, transfer loop using a heat exchanger for exchanging heat between the heat transfer loop and a heat exchanger loo connected the solar collector.

[0043] Typically a heat transfer medium including an antifreeze mixture is provided in the heat exchanger loop.

[0044] Typically the system further includes a thermostatic mixing valve for controlling a temperature of the heat transfer medium flowing into the buried loop portion. [0045] Typically the thermostatic mixing valve is for supplying an output flow of heat transfer medium by mixing:

a) a first input flow of heat transfer medium that has been heated using one of the sol r collector and an auxiliary heater; and,

b) a second input flow of heat transfer medium that has flowed through the buried loop portion.

[0046] Typicall the system includes a mixing valve bypass for allowing heat transfer medium to bypass the thermostatic mixing valve.

[0047] Typically the system includes a bypass valve for controlling whether heat transfer medium bypasses the thermostatic mixing valve via the mixing valve bypass.

[004$] Typically the system further includes a cooling loop such mat the heat transfer medium can be diverted through the cooling loop to allow cooling of the heat transfer medium.

[0049] Typically the system includes a diversion valve at each end of the buried loop portion of the heat transfer loop, the diversion valves bein for controlling whether the heat transfer medium is diverted through the cooling loop.

[0050] Typically the system includes reversal valves for allowing a flow directio of the heat transfer medium through the heat transfer loop to be reversed.

[0051] i a second broad form the present invention seeks to provide a method of regulating soil temperature, the method being performed using a system including:

b) a solar collector thermally coupled to the heat transfer loop;

c) a pump for pumpin the heat transfer medium through the heat transfer loop, whereby operation of the pum can cause a heat exchange between the solar collector and the soil, via the heat transfer medium;

d) a soil temperature sensor for sensing a soil temperature in the soil; e) an external temperature sensor for sensing an external temperature indicative of a temperature in the solar collector; and,

f) a controller, wherein the method includes using the controller to control operation of the pump using the soil temperature and the external temperature so that the pump operates when heat exchange between the solar collector and the soil will act to reduce a temperature difference between the soil temperature and a predetermined soil temperature, to thereby regulate the soil temperature.

Brief Description of the Drawings

[0052] An example of the present invention will now be described with reference to the accompanying drawings, in ^'which: -

[0053] Figure 1 schematic diagram of a first example of a soil temperature regulation system ;

[0054] Figure 2 is a schematic diagram of an installation of an example of the soil temperature regulation system of Figure 1 including a plurality of soil temperature sensors;

[0055] Figure 3 is a schematic diagram of a second example of a soil temperature regulation system including a return temperature sensor;

[0056] Figure 4 is a schematic diagram of a third example of a soil temperature regulation system including a return tank;

[0057] Figure 5 is a schematic diagram of a fourth example of a soil temperature regulation system including an auxiliary heater and valve arrangement;

[0058] Figure 6 is a schematic diagram of a fift example of a soil temperature regulation System further including a cooling loop;

[0059] Figure 7 is a schematic diagram of a sixth example of a soil temperature regulation system further including an external heat exchanger; and,

[0060] Figure 8 is schematic diagram of a seventh example of a soil temperature regulation system including a thermostatic mixing valve. Detailed Description of the Preferred Embodiments

[0061] An example of a system 100 for regulating soil temperature will now be described with reference to Figure 1.

[0062] The system 100 includes a heat transfer loop 110 including a buried loop portion 1 1 1 that is buried in soil 101, whereby a heat transfer medium is provided in the heat transfer loop 110 in use, and a solar collector 120 is thermally coupled to the heat transfer loop 110. The system 100 also includes a pump 130 for pumping the heat transfer medium through the heat transfer loop 110, a soil temperature sensor 140 for sensing a soil temperature in the soil 101 and an external temperature sensor 1 50 for sensing an external temperature indicative of a temperature in the solar collector 120. Furthermore, the system 100 includes a controller 160 for controlling operation of the pump 130 using the soil temperature and the external temperature so that the pump 130 operates when the heat exchange between the solar collector 120 and the soil 101 will act to reduce a temperature difference between the soil temperature and a predetermined soil temperature, to thereby regulate the soil temperature.

[0063] It will be appreciated that such a system 100 can be used to regulate the soil temperature by having the pump 130 operate to cause heat to be exchanged between the sol r collector 1.20 and the heat transfer medium, and in turn between the heat transfer medium and the soil 101 as the heat transfer medium flows through the heat transfer loop 1 10, as required based on feedback of the soil temperature and monitoring the external temperature.

[0064] A comparison of the soil temperature sensed by the soil temperature sensor 140 and the predetermined soil temperature can allow the controller 160 to determine the temperature difference from a desired set point represented by the predetermined soil temperature, and thus allow the controller 160 to react to deviations from the predetermined soil temperature. Since the external temperature sensor 150 measures an external temperature that is indicative of the temperature in the solar collector 120, the external temperature can be used by the controller 160 in determinin whether the solar collector 120 is at a suitable temperature for causin a desired direction of heat exchange (i.e. heating or cooling) betwee the solar collector 120 and the soil 101. [0065] In the example shown in Figure 1 , the solar collector 120 is connected to the heat transfer loop 1 10 such that the heat transfer medium can flow through the solar collector 120. This results in an in-line arrangement which provides a direct thermal coupling between the solar collector 120 and the heat transfer loop 1 10 using a relatively simple piping configuration. However, in other examples, the solar collector 120 may be thermally coupled to the heat transfer loop 1 10 in different ways whilst still allowing equivalent overall functionality as described above. For example, the solar collector 120 may be thermally coupled to the heat transfer loop 110 using an external heat exchanger whereb the heat transfer medium does not flow directly through the solar collector 120, but instead flows through the heat exchanger to allow the heat exchange between the solar collector 120 and the soil 101. Further details of such an arrangement will be described in due course,

[0066] In any event, the system 100 is able to take advantage of natural heating or cooling effects by having the controller 160 operate the pump 130 when suitable heat exchanges that will adjust the soil temperature towards the predetermined soil temperature will take place. For example, if the soil 101 is cooler than desired such that heating of the soil 10 i s requi red (i.e. the sensed soil temperature is below than the predetermined soil temperature), the controller 160 will cause the pump 130 to operate if the heat exchange between the solar collector 120 and the soil 101 , via the heat transfer medium, i s in a direction that will heat the soil 101. This will typicall be the case during warm parts of the day when solar energy heats the solar collector 120 so that the heat transfer medium flowing through the sol r collector 120 will be heated and the heated heat transfer medium will in turn heat the soil 101 as it flows through the buried loop portion i l l . It will be appreciated that circumstances in which heating will occur due to heat exchange from a relatively warm solar collector 120 to relatively cool soil 101 can be determined using the external temperature sensed by the external temperature sensor 150.

[0067] The system 100 can also be used to cool the soil 101 in a generally reversed manner. If the soil 101 is wanner than desired (i.e. the sensed soil temperature is above the predetermined soil temperature), the controller 160 will cause the pump 140 to operate if the heat exchange between the solar collector 120 and soil 101 will cool the soil 101 . This may occur when ambient temperatures drop at night, which can result i the cooling of the heat transfer medium passing through the solar collector 120 such that heat can be transferred from the soil 101 into the cooled heat transfer medium flowing through the buried loop portion 1 11 , thus cooling the soil 101.,

[0068] I view of the above, it will be appreciated that the system 100 will be suitable for regulating the temperature of soil 101 that is used for planting and growing crops, to thereby help to maintain desirable soil temperatures for crop growth. This can allow crops to be grown with improved yields or extend the growing season for the crop by allowing soil temperatures to stay within desirable limits for a longer portion of the year, This can also allow particular crops to be grown in regions that are not traditionally considered suitable for growth of those crops due to undesirable naturally occurring soil temperature conditions,

[0069] it will be thus be appreciated that the soil temperature regulation system 100 can provide an improved means for maintaining ideal, crop specific, subsurface growing temperatures.

[0070] The controller 160 may be provided in any suitable form for controlling the pum 130 based on the soil temperature and the external temperature. In one example, the controller 160 may be programmable logic controller (PLC), programmed with suitable control logic for causing operation of the pump in response to particular soil temperature an external temperature inputs. In other examples, the controller 160 may be provided using any suitable processing system, such as a microcontroller, a field programmable gate array (FPGA) or a general, purpose computer having suitable input and output capabilities. It will be appreciated that the form of the controller 160 is not particularly limited, although typically the controller 160 should be configured to receive a input from at least one temperature sensor and at least one external temperature sensor and provide an output for controlling at least the pump 130, such as by providing a control signal to a pump relay for controlling operation of the pump 130.

[0071] In one example, the controller 160 may be particularly configured to determine, based on the temperature difference, whether heating or cooling of the soil is required (for example by determining which of the soi l temperature or the predetermined soil temperature is large). Then, the controller 160 would determine, using the external temperature, whether heat exchange between the solar collector .and the soil will heat or cool the soil 101. This may, for example, involve comparing the external temperature wit the soil temperature to determine whether there is a sufficient difference between the external temperature and the soil temperature to cause the required heat exchange for heating or cooling the soil 101. The controller 160 would cause the pump to operate if heating of the soil 101 is required and it is determined that heat exchange between the solar collector 120 and the soil 101 will heat the soil 101, or alternatively, if cooling of the soil 101 is required and it is determined that the heat exchange between the solar collector 120 and the soil 101 will cool the soil 101.

[0072] The controller 160 may have relatively simple control functionality so that the soil temperature is regulated about the predetermined soil temperature value which may be established, for example, based on desirable soil temperature conditions for growing a particular crop. However, it will be appreciated that control about a single set point may cause the pump 130 to be switched on and off unnecessarily.

[0073] In some examples, the controller 160 may be configured to only cause operation of the pump 130 if the soil temperature difference is greater than a predetermined soil temperature difference threshold. Thus, the system 100 may operate by maintaining tile soil temperature within a desired range. It will al so be appreciated that more sophisticated control regimes may be used so that a plurality of different predetermined temperature limits are used. For example, when soil heating takes place the pump 130 may be allowed to continue to operate until a maximum soil temperaurre limit is attained, but once the pump is 130 is stopped it will not becom operational again until the soil temperature falls below a minimum soil temperature limit This type of behaviour can prevent the pump 130 from being switched on and off rapidly as the soil temperature exceeds and falls below a temperature threshold.

[0074] In some examples, the controller 160 may be configured to control the operational speed of the pump 130 and thus vary the flow rate of the heat transfer medium through the heat transfer loop 110, to allow further control over the heat exchange.

[0075] The controller 160 may also use multiple temperature sensors to control the pump 130, and suitable techniques in this regard will be described below with reference to further examples. The system 100 may also optionally include a data logger (not shown) for logging temperature sensed by the temperature sensor, or in some implementations, a plurality of different temperature sensors. In one example, the combined functionality of controller 160 and the data logger may be provided using the same processing system.

[0076] The external temperature sensor 150 is desirably positioned proximate the solar collector 120, which can allow the sensed external temperature to more closely reflect the temperature in the solar collector 120 compared to positions away from the solar collector 120 and hence allow a more accurate determination of whether a desired heat exchange will occur when the pump 130 is operated. However, the external temperature sensor 150 does not necessarily need to be positioned proximate the solar collecto 120, and in other examples the external temperature sensor 150 may be placed in any position above ground such that the sensed external, temperature may be based on ambient temperatures anywhere out of the soil 101 but nevertheless be indicati ve of temperatures in the solar collector 120.

[0077] An example of a practical implementation of the system 100 is shown in Figure 2. The heat transfer loop 1 10 may be suitably provided in the form of piping, or any other suitable heat transfer medium conduit, including length o piping buried in the soil 101 of a field, paddock or other area to be heated cooled to provide the buried loop portion 1 1 1.

[0078] The heat transfer medium may be provided as any fluid having suitable heat transfer characteristics. In one example, the heat transfer medium may be water and the heat transfer loop 1.10 may be provided usin agricultural water piping or the like, The piping for providing at least the buried loop portion 1 1 1 should be constructed from a material which readily allows heat exchange between the water and the soil. I another example, readily available rubber based piping used for solar pool heating can be modified for the purpose of laying in trenches to convey water as the heat transfer medium. It will be appreciated that heat transfer media other than water may be used, such as refrigerants having improved heat transfer characteri tics or resistance to freezing in cold soils.

[0079] in this example, the buried loop portio 1 1 1 of the heat transfer loop 1 10 is buried at a depth beneath the surface where crop plants 201 are planted. The depth d may be selected depending on the depth to which soil heating/cooling is required, which may be determined by the type of crop, natural soil temperature profiles, or the like. For example, the depth d may be in the range of 200 mm to 1000 mm, and more preferably in the range of 400 mm to 800 mm. In one example the depth d is about 700 mm.

[0080| The buried loop portion 111 may extend along any desired path through the soil 10 , and in the example of Figure 2, the buried loop portion 11 includes parallel rows of piping generally aligned with rows of the plants 201 , separated by a row spacing a. This can allow the buried loop portion 1 11 t be installed so that each of the plants 201 has a similar proximity to the buried loop portion 1 11 of the heat transfer loop 1.1.0, in turn al lowing more consistent temperature regulation with respect to the regions of the soil 101 in which the plants 201 are growing, It will be appreciated, however, that any suitable underground piping arrangement may be used to provide the buried loop portion,

[0081] The solar collector 120, or a suitably interconnected array of a plurality of solar collectors 120, ma be placed at any position above the surface of the soil 301- As shown in Figure 2, the solar collector 120 may conveniently be installed on the roof of a building 202, such as a shed or the like which may already exist in the vicinity of the soil 101 to be heated/cooled. It will thus be appreciated any commercially available solar collectors 120 adapted for roof installation may be suitable for use in the system 100. In this case the external temperature sensor is also installed on the roof of the buildin 202 on or near the solar collector 120, The pump 130 and controller 160 may also be conveniently housed in or near the building 202 upon which the solar collectors 120 are installed.

[0082] Although the system 100 may be controlled based on the soil temperature sensed using a single soil temperature sensor 140, it may be desirable to provide a plurality of soil temperature sensors, examples of which are also shown in. Figure 2.

[0083] For instance, the system 100 may include an upper soil temperature sensor 241 positioned in the soil 101 proximate a soil surface and proximate the buried loop portion 1 1 1 of the heat transfer loop 1 10. In this case the upper soil temperature sensor 2 1 is placed near the base of a plant 241 for allowing soil temperature indicative of temperatures at the roots of the plant 241 to be obtained.

[0084] Alternatively or additionally, the system 100 may include a buried soil temperature senso 242 positioned in the soil 101 at a predetermined depth beneath the soil surface and proximate the buried loo portion 1 1 1 of the heat transfer loop 110. In this ease the buried soil temperature sensor 242 is placed approximately halfway between the soil surface and the buried loop portion 11 1, or at a predetermined depth of about d/2 as shown in Figure 2.

[0085] Furthermore, the system 100 may include a loop soil temperature sensor 243 positi oned in the soil 101 at a depth similar to the depth d of the buri ed loop portion 1 1 1 and proximate the buried loop portion 11 1 of the heat transfer loop 110. The loop soil temperature sensor 243 may allow temperature measurements to be taken which are indicative of the temperature of the heat transfer medium in the heat transfer loop 1 10 at intermediate locations along the buried loop portio 1 1 1, without needing to actually provide temperature sensors inside the piping.

[0086] An offset soil temperature sensor 244 may be provided, also being positioned in the soil 101 at a depth similar to the depth d of the buried loop portion 11 1 but being offset, from the buried loop portion 111 of the heat transfer loop b a predetermined offset amount b. This allows temperature measurements to be taken which indicate the penetration of heating/cooling effects into the soil 101 i the absence of other naturally occurring temperature gradients between the soil surface and the depth d,

[0087] It will be appreciated that any number and combinatio of soil temperature sensors of the above types may be used by the controller 160 to control the operation of the pump 130, In one example, the controller may be configured to control the pump 130 based on respective soil temperatures sensed by two or more of a plurality of soil temperatures, measured b different soil temperature sensors. For instance, the controller 160 may be configured to determine an average soil temperature using the respective soil temperatures, and control the pump 130 by comparing the average soil temperature with the predetermined soil temperature. In other examples, soil temperature sensors 140 may be provided which are not used by the controller, but which may nevertheless allow monitoring of soil temperatures i different positions in the soil. In any event, the particular selection of soil temperature sensors 140 and their positions in the soil may depend on the specific installation, the type of crop and numerous other factors. [0088] Ambient soil temperature sensors may also be used to allow monitoring of soil temperatures away from the soil 101 that is heated/cooled by the system 100. For example, the system 100 may include an ambient upper soil temperature sensor 245 positioned in the soil 101 substantially at the soil surface and sufficiently separated from the buried loo portion 1 1 1 of the heat transfer loop 110 so as to be substantially unaffected by heat transfer between the heat transfer medium and the soil 301 . Alternatively or additionally, the system 100 may include an ambient buried soil temperature sensor 246 positioned in the soil 101 at a predetermined depth similar to that of buried soil temperature sensors 242 and also suffici ently separated from the buried loop portion 1 1 1 of the heat transfer loop 3 10 so as to be substantially unaffected by heat transfer between the heat transfer medium and the soil 101.

[0089] It will be appreciated that ambient soil temperatures may be compared to soil temperatures measured in the vicinity of the buried loop portion 1 1 1 of the heat transfer loop 1 1 in order to assess the heating/cooling performance of the system 100. In some examples, the controller 160 may be further configured to control the pump 130 using at least one ambient soil temperature sensor 245, 246. For instance, the controller 160 may be configured to prevent operation of the pump 130 at times when ambient soil temperature measurements indicate that the soil temperature will naturally be within an acceptable range of the predetermined temperature. This can prevent unnecessary operation of the system 100 during the normal growing season of a crop so that energy is not used to drive the pum 130 when it is not required.

[0090] It will be understood that the above mentioned heating or cooling processes use naturally occurring temperature differentials, such that significant external power may only be required to drive the pump 140 so that the heat transfer medium flows through the heat transfer loop 1 10 as required. In some examples, a solar power generator (not shown) may be provided for generating electrical power to drive at least the pump 140. In some examples, the solar power generator may also be installed on the roof of the buildi ng 202 alongside the solar collector 120, or i any other suitable position.

[0091] An energy store such as battery (not shown) may also be provided for storing electrical energy provided by the solar power generator, so that the pump 140 can be powered fay the battery, thus allowing operation of the pump 140 at night or at other times when insufficient power is provided by the solar power generator. The controller 160 may also be powered by the solar power generator or the battery, although it will be appreciated that a separate power source may be provided for the controller 160 to ensure constant operation.

[0092] In one example, the system 100 may be configured to allow the flow of the heat transfer medium in the heat transfer loop 1 10 to be reversed. It will be appreciated that the heat transfer between the heat transfer medium and the soil 101 along the buried loop portion 11 1 will diminish along the length of the buried loop portion 1 1 1 as the temperature in the heat transfer medium approaches that of the soil 101 due to the heat transfer. Thus heat may he unevenly distributed through the soil with more heat transfer taking place in earlier portions of the buried loop portion 1 1 1. By reversing the flow in the heat transfer loop 110 periodically, the heat may be more evenly distributed. The system 100 may include reversal valves (not shown) or the like for allowing the flow direction of the heat transfer medium through the heat transfer loop 100 to be reversed. In some examples, the reversal valves may be implemented using automated solenoid or ball valves.

[0093] In any event, it will be appreciated that the system 100 can provide a sustainable, environmentally friendly method of achievin soil temperature regulation, which can operate with minimal or no external power requirements,

[0094] A further example of a system 300 for regulating soil temperature is shown in Figure 3. The system 300 is similar to that shown in Figure 1, but in. this case, the system 300 further includes a return temperature sensor 370, which is provided for sensing return temperature indicative of a temperature of the heat transfer medium that has flowed througli the buried loop portion 111. The controller 160 may be configured to control the pump 130 by comparing the external temperature and the return temperature. This can allow more reliable determination of whether a desired heat exchange will take place whe the heat transfer medium flows through the solar collector 120.

[0095] In particular embodiments of the system 300, the controller 1 0 may be configured so that, when the soil temperature is below the predetermined soil temperature, the controller 160 causes operation of the pump 130 when the external temperature is greater than the return temperature, to thereby cause heating of the soil. Additionally, the controller 160 may be configured so that, when the soil temperature is above the predetermined soil temperature, the controller 160 causes operation of the pump 130 when the external temperature is less than the return temperature, to thereby cause cooling the soil.

[0096] It will be understood that the controller 1.60 may be configured to cause operation of the pump 130 only when a return temperature difference between the external temperature and the return temperature exists that is sufficient to cause useful heat exchange to occur. For example, the controller 160 may only cause operation of the pump 130 if the return temperature difference is greater than a predetermined return temperature threshold. This can prevent operation of the pump 130 at times when, whilst a return temperature difference exists, the amount of heat transfer that would occur due to the flow of the heat transfer medium would not be enough to justify the energy expended to operate the pum 130.

[0097] As illustrated in Figure 4, a further example of a soil temperature regulation system 400 is similar to that shown in Figure 3 but may also include a return tank 470 for storing heat transfer medium that has flowed through the buried loop portion 1 1 1. The return temperature sensor 370 may be conveniently provided in or near the return tank, to allow accurate determination of the temperature of the heat transfer medium before it is supplied to the solar collector using the pump 130, which may be positioned between the return tank 470 and the solar collector 120. Whilst the return tank 470 is not essential, it will be appreciated that this can ensure an adequate supply of heat transfer medium to the pump 130 without needing to ensure the entire heat transfer loop 1 10 is primed with the heat transfer medium at all times.

[0098] An example of a controller configuration for a system 400 as shown in Figure 4 will now be outlined. For the purpose of this example, the system 400 is installed proximate a field including soil 101 to be heated/cooled, and includes a heat transfer loop 1 10 consisting Of piping filled with water, an array of solar collectors 120, a water pump 130, a return tank 470 for holding water before it is pumped into the heat transfer loop 1 10 piping, and a controller 160 in the form of a programmable logic controller. [0099] As discussed above, the pump 130 is controlled using the soil temperature, the external temperature and the return temperature. The soil temperature is sensed by using a soil temperature sensor 140 installed in the field at a predetermined depth beneath the soil surface, which is nominally 350mm in this case, although the predetermined depth can be adjusted depending on individual requirements. The external temperature is sensed using an external temperature sensor which is installed on a roof upon which the solar collectors 120 are also installed. The external temperature sensor may be provided in a sample portion of one of the solar collectors 120 to provide an accurate indication of the temperature in the solar collectors 120. The return temperature installed in the return tank and thus is indicative of the temperature of water in the return tank 470 after the water has flowed through the buried loop portion 111.

[0100] The controller 160 is programmed so that the pump 130 will not operate if the soil temperature reaches the predetermined soil temperature, which in this case is adjustable but is nominally set to 3Q°C. If the external temperature at the solar collectors 120 exceeds the return temperature by a predetermined temperature difference threshold, which is adjustable but nominally set as 1°C or greater, the after an adjustable time delay, such as minute or more, the pump 130 will operate (unless the soil temperature already exceeds the predetermined soil temperature), Subsequently if the external temperature drops belo the predetermined soil temperature by the predetermined temperature difference threshold, then after the time delay the pump 130 will switch off.

[0101] If any of the soil temperature sensor 140, the external temperature sensor 150, or the return temperature sensor 370 fails then the system 400 will transition into a fault condition and the controller 160 will cause the pump 130 to cease operation. Temperature sensor failure parameters may be established such that the sensor will be deemed to have failed if sensed temperatures fall outside of an established normal operating range. For example, failure may be deemed to have occurred if the sensed temperatures are less than 10°C or greater than 70°C, although it will be appreciated that this range is adjustable. It is noted that if a temperature sensor configured to provide readings in °C fail it will typically provide erroneous readings of 0°C or 1QQ°C. In some examples, however, the controller 160 will receive input from multiple redundant temperature sensors so that the system 400 ca continue to operate without transitioning into the fault condition.

[0102] The system 400 may also include a capability to allow manual selection of the particular soil temperature sensor to be used by the controller 160 in controlling the pump. For example, the controller 160 may include an input from a switch allowing user selection of the soil temperature sensor, such that the controller may obtain the soil temperatur from either a buried soil temperature sensor 242 or an offset soil temperature 244 depending on the selection.

[0103] A more sophisticated example of a soil temperature regulation system 500 is illustrated in Figure 5. In this example the system 500 includes a return tank 470 and return temperature sensor as per the previ ous example of Fi gure 4, but further includes an optional auxiliary heater 580 connected to the heat transfer loopi lO, whereby when the auxiliary heater 580 is activated, heat transfer medium in the heat transfer loop is heated as it flows through the auxiliar heater.

[0104) The controller 160 may be configured to control activation of the auxiliary heater 580 so that the auxiliary heater 580 is activated when the soil temperature is below the predetermined soil temperature and the soil 101 is not being heated using heat exchange between the solar collector 120 and the soil 101 , For instance, it might be determined that heating is required when the soil temperature 140 is less than the predetermined sensor, but the external temperature is less than the return temperature such that natural heat exchange would not cause the desired heating, as may be the case at night or during periods of cold weather. In previous examples, the pump 130 would not typically operate as it would cause undesirable cooling of the soil 101, however, in this example, the auxiliary heater 580 would be activated by the controller 160 and the purnp 130 would be operated to cause heat transfer medium to flow through the auxiliary heater 580 for heating,

[0105] it will also be appreciated that the auxiliary heater 580 may be activated even when a desirable heat exchange occurs using the solar collector 120, so as to supplement the natural heating of the soil . In such scenarios, the solar collector 120 ma be used to preheat the heat transfer medium before it is heated further by the auxiliary heater 5S0, [0106] Whilst the auxiliary heater 580 may be installed in series with the solar collector 120, this is not necessarily desirable as this would mean the auxiliary heater 580 would need to consume additional energy to add heat that would otherwise be lost through the solar collector through cooling heat exchange. Rather, it may be preferable to have a arrangement as show in Figure 5, where the System 500 includes a valve 590 for controlling the flow of heat transfer medium through the solar collector 120. This can allo the heat transfer medium to selectively flow througli the solar collector 120 when a desirable heat exchange will occur, otherwise the fl w of heat transfer medium can be diverted around the solar collector 120 so as to only pass through the auxiliary heater 580 when an undesirable heat exchange will occur. The controller 160 may be configured to control the valve 59 based temperature inputs in a similar manner as is used to control the operation of the pump.

[0107] In the example, of Figure 5, the valve 590 has a first valve position for allowing the heat transfer medium to flow through the solar collector 120 (and then through the auxiliary heater in this example) and a second valve position for causing the heat transfer medium to bypass the solar collector 120 and only flow through the auxiliary heater 580. The controller may be particularl configured to control the valve 590 so that the valve 590 is moved into the second valve position when the soil temperature is below the predetermined soil temperature and the external temperature is less than the return temperature. This can prevent the need for the auxiliary heater 580 to counteract heat loss via the solar collector 120, which may otherwise occur at night,

[0108] ft will be appreciated that, the auxiliary heater 580 may be provided in any suitable form, such as a heat pump or any other type of heat exchanger. The auxiliary heater 580 may be electrically powered, typically using the same source of power as the pump. In some alternative examples, however, the auxiliar heater 580 may be a gas heater which operates by burning natural gas or liquid petroleum gas, or may otherwise operate using any other suitable fuel or power source.

[0109] A further pre-soil temperature sensor 55 1 may be provided for sensing the temperature of heat transfer medium after it has flowed througli the auxiliary heater 580. This can allow the heating performance of the auxiliary heater 580 to be monitored more effectively. Additionally or alternatively, a solar water temperature sensor 55 may be proyided for sensing a solar temperature of the heat transfer medium after it has flowed through the solar collectors 120. This can be used to determine whether further heating of the heat transfer medium using the auxiliary heater 580 may be required.

[0110] The system 500 discussed above thus provides an optional capability to introduce additional heat provided using an external power source. The auxiliary heater 580 and valve 590 allow for closer temperature control and can extend the useful operation of the system 500 into situations where temperature conditions are not suitabl e for allowing heating of the soil 101 using natural solar heating of the solar collector 120. The valve 590 can prevent beat loss via the solar collector 120 by having the heat transfer medium bypass the solar collector 120 during cold conditions.

[01.11] Alternative embodiments of the system may include an auxiliary chiller (not shown) for providing an additional capability to cool the soil. In some examples, the auxiliary chiller may be provided alongside an auxiliary heater 580 to provide extended soil temperature regulation capabilities across a wide range of environmental conditions. It will be appreciated that this may necessitate more comple controller behaviour to selectively activate the pump 160, and auxiliary heater 580 or auxiliary chiller as required.

[0112] However, in some examples, such as in installations for hot climates, an auxiliary chiller ma be provided instead of the auxiliary heater 580,

[0113] The auxiliary chiller may be connected to the heat transfer loop 1 1.0 in a similar manner as discussed above for the auxiliary heater 590, such that when the auxiliary chiller is activated, the heat transfer medium in the heat transfer loop 1 10 is chilled when the heat transfer medium flows through the auxiliary chiller.

[0114] Accordingly, in examples having an auxiliary chiller, the controller 160 may be configured to control .activation of the auxiliary chiller so that the auxiliary chiller is activated when the soil temperature is above the predetermined soil temperature and the soil 101 is not being chilled using heat exchange between the solar collector 120 and the soil 101.

[0115] The auxiliary chiller can be provided using any suitable cooling technology, such, as a refrigeration unit or heat exchanger coupled to a suitable heat sink; or the like. [0116] An example of a controller configuration for a system 500 as shown in Figure 5 will now be outlined. As per the previous controller configuration example, the system 500 is installed proximate a field including soil 101 to be heated/cooled, and includes a heat transfer loop 1 10 consisting of piping filled with water, an array of solar collectors 120, a water pump 130. a return tank 470 for holding water before it is pumped into the heat transfer loop 110 piping, and a controller 1.60 in the form of a programmable logic controller.

[0117] Furthermore, the system 500 includes an auxiliary heater 580 in the form of an electrically powered heat pump and a 3 -way valve 590, In this example, the auxiliary heater 580 is controlled automatically to output heated water at 40°C, so will not. do any heating work when the temperature of water flowing through the solar collector 120 is above this temperature. Accordingly, the activation of the auxiliary heater 580 does not need to be controlled by the controller 160 in this example, although in other examples the auxiliary heater 580 may be operated directly by the controller 160.

[01 IS] The piping providing the buried loop portion 1 1 1 in the soil 10 ! is installed at a depth of approximately 550mm below the surface of the soil 101

[0119] i this example, the controller 160 receives inputs from a plurality of temperature sensors including multiple soil temperature sensors, a external temperature sensor 150, a return temperature sensor 370. Installation positions of the temperature sensors are similar to those described above with respect to the practical implementation shown in Figure 2.

[0120] In particular, the soil temperature sensors include:

• an upper soil temperature sensor 241 at a depth of approximatel 100mm below the surface of the soil 101, i a heat exchange affected region of the soil 101 proximate to the buried loop portion 1 1 1 ;

• a buried soil temperature sensor 242 at a depth of approximately 350mm proximate the buried loop portion 11 1;

• an offset soil temperature sensor 244 at a depth of approximately 350mm and offset horizontally from the buried loop portion 1 1 1 by approximately 500mm;

• an ambient upper soil temperature sensor 245 at a depth of approximately 100mm below the surface of the soil 101 , in a region of the soil 101 that is sufficiently distant from the buried loop portion 1 1 1 so as to be unaffected by heating or cooling of the soil by the system 500;

• and ambient buried soil temperature 246 at a depth of approximately 350mm below the surface of the soil 101, and similarly in a region of the soil 101 that is sufficiently distant from the buried loop portion 111 so as to be unaffected by heating or cooling of the soil by the system 500; and,

• a buried soil return temperature sensor havin simila positioning as the buried soil temperature sensor 242 but positioned proximate the end of the buried loop portion 1 1 1 so as to indicate the temperature of the water after heat exchange with the soil has taken place.

[0121] It will be appreciated that depths discussed above are provided as examples only and may be adjusted depending on individual requirements

[0122] The pum 130 is controlled by the soil temperature in the field as sensed by the buried soil temperature sensor 242 at the predetermined depth of 350mm. The controller 160 is configured to operate the pump 130 to cause heating of the soil 101 unless the soil temperature reaches the predetermined soil, temperature, which in this case is adjustable but is nominally set to 30°C as a maximum set point.

[0123] If the external temperature sensed by the external temperature sensor 150 at the solar collectors 120 exceeds the return temperature sensed by the return temperature sensor 370 hi the retur tank 470 by a predetermined temperature difference threshold sufficient to cause the heat transfer, then after an optional time delay the pump 130 will be operated and the valve 590 will be controlled to cause water to flow through the solar collectors 120 and the auxiliary heater 580, i.e. the first position of the valve 590 will be selected. In the event the external temperature is colder than the return temperature then after an optional delay the valve 590 will be controlled to cause water to bypass the solar collectors 120 and flow through the auxiliary heater 580 only, i.e. the second position of the valve 590 will be selected,

[0124] It will be appreciated that the only temperature sensors actually used by the controller 160 in this controller configuration are the buried soil temperature sensor 242, the external temperature sensor 150 and the return temperature sensor 370, whilst the other temperature sensors discussed above are not used. Nevertheless, all temperature readings from the temperature sensors will typically be logged by a data logger which can be provided as an integral function of the controller 160, and logged temperature readings can be analysed to determine whether the system 500 ha satisfactory performance. Predetermined values used by the controller, such as the predetermined soil temperature, predetermined temperature difference thresholds, and the like, can be adjusted to modify the performance of the system 500 in view of th logged temperature readings.

[0125] As per the earlier controller configuration example, if a temperature sensor relied upon by the controller 160 (i.e. buried soil temperature sensor 242, the external temperature sensor 150 or the return temperature sensor 370) fails then the controller 160 will transition into a fault condition and the pump 130 will cease operation.

[0126] An alternative example of a controller configuration for a system 500 having a similar implementation as discussed above will now be outline. As per the previous example, the pump 130 may be controlled by the soil temperature sensed by the buried soil temperature sensor 242 at a depth of 350mm, and the pump 130 will run to achieve heating unless the soil temperature reaches the predetermined soil temperature. If the external temperature exceeds the return water temperature by a predetermined temperature difference threshold then after an optional time delay the -way valve 590 directs water to the solar collectors 120 and the auxiliary heater 580.

[0127] In this example, the system 500 also includes a solar water temperature sensor 552 for sensing a .solar water temperature of the water after it has flowed through the solar collectors 120. When the 3-way valve 590 switches to allow water to flow through the solar collectors 120, then af er another optional, adjustable delay, the controller 160 wilt monitor the solar water temperature sensed by the solar water temperature sensor and compare it to the return water temperature. If the solar water temperature is hotter than the return water temperature b an adjustable solar water temperature threshold, then the controller 160 will allow the system 500 to continue to operate using the solar collectors 120 by keeping the valve 590 in the first position. If the solar water temperature is colder than the return water temperature then after another optional, adjustable delay the controller 160 will switch the valve 590 to the second position so as to allow water to flow through the auxiliary heater 580 only.

[0128| Figure 6 shows an example of a system 600 which further adds a cooling loop 612 to the system 500 of Figure 5, The cooling loop 6.12 as provided such that the heat transfer medium can be diverted through the cooling loop 612 to allow cooling of the heat transfer medium. It will be appreciated that this cart reduce the required control complexity to switch to cooling operation.

[0129] As shown in Figure 6, the system 600 may include a diversion valve 691, 692 at each end of the buried loop portion 11 1 of the main heat transfer loop 1 10. These diversion valves

691 , 692 are provided as a convenient means for controlling whether the heat transfer medium is diverted through the cooling loop 612, which is provided in parallel to the portion of the main heat transfer l oop 100 extending above ground .

[0130] The cooling loop 612 may include an auxiliary chiller 681, a cooling tank 671 and a cooling pump 631. When the diversion valves 691, 692 are in position for diverting the heat transfer medium from the main heat transfer loop through the cooling loop 612, the cooling pump 631 will circulate the heat transfer medium through the cooling loop 612 and the buried loop portion 1 1 1 . The heat transfer medium will flow from the buried loop portion 1 1 1 via the diversion valve 691 and through the auxiliary chiller 681 , Cooled heat transfer medium exiting the auxiliary chiller 681 will be held by the cooling tank 671 until drawn off by the cooling pump 631 , Cooled heat transfer medium will then be reintroduced into the buried loop portion 1 11 via the diversion valve 692. Accordingly, the soil 101 can be cooled even in high temperature conditions.

[0131] It will be appreciated that the operation of the cooling loop pump 6 1 and auxiliary chiller may also be controlled by the controller 160 as indicated by the dashed lines. The diversion valves 691, 692 may be controlled manually or also automatically controlled by the controller 160. When the controller 160 is configured to control the diversion valves 691,

692. the controller 160 would typically monitor the soil temperature sensor 140, and when excessive soil temperatures are detected, activate the diversion valves 691 , 692 to divert the flow of heat transfer medium into the cooling loop 612. This will override any heating taking place in the main portion of the heat transfer loop 1 10 that is coupled to the sol r collector 120. Thus, the soil 101 ma be immediately cooled as required.

[0132] As mentioned above, alternative implementations of the system ma have the solar collector 120 thermally coupled to the heat transfer loop 110 without necessarily having the heat transfer medium flow directly through the solar collector 120 in an in-line arrangement. An example of an alternative technique for thermally coupling the solar collector 120 to the heat transfer loop 110 is shown in Figure 7.

[0133] It will be noted that the example system 700 of Figure 7 is similar to the system 500 of Figure 5, but the solar collector 120 is now thermally coupled to the heat transfer loop 110 using a heat exchanger 721 for exchanging heat between the heat transfer loo 1 10 and a heat exchanger loop 713 connected the solar collector 120.

[0134] This external heat exchanger 721 arrangement can allow for different heat transfer media to be used in the heat exchanger loop 713 and the main heat transfer loop 1 10. For example, a first heat transfer medium provided in the main heat transfer loop 110 may be water, whilst a second heat transfer medium may be provided in the heat exchanger loop 713 , The second heat transfer medium may be a antifreeze mixture, such as mixture of water and a suitable antifreeze compound such as ethylene glycol, or the like, to prevent freezing of the heat transfer material in the solar collector 120 overnight in cold climates.

[0135] The heat exchanger loop 713 may also include at heat exchanger return tank 772 for storing the second heat transfer medium s it returns from the heat exchanger 721 and a heat exchanger pump 732 for circulating the second heat transfer medium along the heat exchanger loop 713. it will be appreciated that the second heat transfer medium will be pumped through the solar collector 120 to allow for a heat exchange between the solar collector 120 and the second heat transfer medium and then through the heat exchanger 721 to allow for a heat exchange between the second heat transfer medium and the first heat transfer medium via the heat exchanger 72 ,1.

[0136] It will be appreciated that any suitable form of heat exchanger 721 ma be used for allowing the heat exchange betwee the second heat transfer medium in the heat exchanger loop 713 and the first heat transfer medium in the main heat transfer loop 1.10 including the buried loop portion 1 11. In this example, the heat exchanger 721 includes an inner pipe which carries the first heat transfer medium from the main heat transfer loop 10 through the heat exchanger 721 , where it is surrounded by the second heat transfer medium that is circulated through the heat exchanger loop 713 using the heat exchanger pump 732.

[0137] It should also be understood that the operation of the heat exchanger pum 732 may also be controlled by the controller 130 as required. The main pump 130 would still be controlled based on temperature sensor feedback to regulate the soil temperature in the manner described above, but the heat exchanger pum 732 could also be selectively activated to provide further control over the amount of heat exchange that takes place through the heat exchanger 721.

[0138] The further example of Figure 8 illustrates another alternative system 800 which adds to the system 500 of Figure 5 a capability for providing further control over the temperature of the heat transfer medium being supplied into the buried loop portion H I .

[0139] In particular, the system 800 further includes a thermostatic mixing valve 894 for controlling a temperature of the heat transfer medium flowing into the buried loop portion I I I . The thermostatic mixing valve 894 may be configured for supplying an. output flow of heat transfer medium by mixing a first input flow of heat transfer medium that has been heated using the solar collector 120 and/or the auxiliary heater 580, and a second input flow of heat transfer medium that has flowed through the buried loop portion 11 I,

[0140] Accordingly, the thermostatic mixing valve 894 can mix a flow of heated heat transfer medium with a flow of cooler heat transfer medium returned from the buried loop portion 1 1 1 , to thereb supply warm heat transfer medium at a controlled temperate into the buried loop portion 1 1. 1 , Thus, the thermostatic mixing valve 894 may be used to supply heat transfer medium into the buried loop portion 1 Ϊ 1 at a controlled, intermediate temperature. In some examples, the thermostatic mixing valve 894 may be configured to supply heat transfer medium within a temperature range of 50°C to 65°C, although any temperature set point ma be selected depending on requirements. In any event, the use of the thermostatic mixing valve 894 can help to avoid supplying excessive heat into the soil 101 as the system 800 operates. [0141] Techniques for providing a suitable thermostatic mixing valve 894 using relatively simple mechanical valve arrangements are known and readily available to those skilled in the art, In preferred implementations the use of the thermostatic mixing valve 894 will not alter the operation of the pump 130.

[0142] As shown in Figure 8, the thermostatic mixing valve 894 may receive the first input flow of heated heat transfer medium after it has flowed through the auxiliary heater 580, via a heated loop portion 814. The thermostatic mixing valve 894 may receive the second input flow of cooler heat transfer medium by diverting some flow of the heat transfer medium pumped fro the return tank 470 to the themtostatic mixing valve 894, via the cool loo portio 815, The output flow of warm heat transfer medium can then be supplied via the output loop portion 816 into the main heat transfer loop 1 10 and buried loop portion 1 1 1.

[0143] In some embodiments, it may be beneficial to system includes a mixing valve bypass 817 for allowing heat transfer medium to bypass the thermostatic mixing valve 894. This can allow the ttierm^'ostatic mixing valve 894 to be bypassed in the event that higher heat is required. In the example of Figure 8, the system 800 includes a bypass valve 893 for controlling whether heat transfer medium bypasses the thermostatic mixing valve 894 via the mixing valve bypass 817. Thus, the mixing valve bypass function may be automated and controlled by having the controller 160 selectively activate the bypass valve 893 when predetermined criteria are met.

[0144] It will be appreciated that the example controller configurations discussed above allow the soil temperature regulation system to operate based on target climatic and subsurface climatic conditions, so that the ideal growing temperature for a crop can be established and maintained. Solar collectors are exposed to both warm and cool conditions and these conditions are monitored by temperature sensors. The system will operate to circulate either warm or cool ater through the pipes buried beneath the crops as required to regulate the temperature within desired parameters. The subsurface climatic conditions are monitored by soil temperature sensors buried at different depths and at different positions relative to the pipes. [0145] Accordingly, the above discussed examples allow for practical soil heating and cooling systems to be implemented, in order to promote and maintain optimal subsurface climatic conditions through the use of solar technology. By using above ground solar collectors that are connected to subsurface, closed circuit pipes, subsurface climatic conditions may be regulated by temperature sensors and water flow rates/times. Furthermore, by storing subsurface heat energy during warmer periods, this energy will continue to filter up through soil levels and sustain target temperatures during cooler periods.

[01461 It will be appreciated that the surface area, size, and model of solar collectors required; the material, length, depth, and diameter of subsurface piping; the size and flow rates of pumps; and temperature thresholds applied to controlling operation of the pump using the external and soil temperature sensors may be site specific and vary according to crop type, soil type, seasons, desired outcomes and budget.

[0147] An example of a beneficial target industry for this system is bananas. This technolog has the potential to remove issues of the seasonality of bananas by providing year round optimal soil temperatures; hence, improving the appearance of winter crops; producing a bigger yield; producing a quicker yield; encouraging deeper root growth making trees more resistant to wind, and having no ongoing energy costs. Success in the banan industry will lead to further development in other cro growing industries.

[0148] The system may also allow for a reduction in the need for chemicals to control pests and diseases leading to healthy improvements on and off farm ; an increased potential for crop productio in lower grade agricultural land with potential outcomes for impoverished communities and developing countries.

[0149] Testing of practical implementation of the soil temperature regulation system have concluded that sub-surface soil temperatures in a variety of soil conditions can be controlled and optimally maintained through the use of solar energy, an electric heat pump, automation including regulated temperature sensor controls, and controlled pumping through strategically pl aced sub -surfac e pipes.

[0150] Preliminary results of the system implemented to regulate the temperature of soil for planting banana crop samples show a increase in the size of the trees and subsequent yield, a faster return on the yield, and an improved appearance of the product. Also, an increase in the number of next generation banana trees ("suckers") has been noted. An increase in root depth and reach has also been recorded.

[0151 ] Preliminary effects of the system used to regulate the temperature of soil for a paw paw crop sample have also been observed. In this instance it was noted that the early stage subject crop showed improved growth and 'sexed' more rapidly than the unhealed sample. Improved root development was again noted.

[0152] It is noted that the soil temperature regulation system may also be used for purposes other than maintaining a desired growing temperature for a crop. In some examples, the system may be used to elevate the soil temperature to a temperature sufficient to eradicate pests and maintain the elevated soil temperature for a prolonged period of time to ensure that pests will be eradicated from the soil in the vicinity of the buried piping. This can be achieved by setting the predetermined soil temperature at a sufficient elevated temperature and otherwise operating the sy stem i the usual manner for the required period of time.

[0153] Throughout this specification and claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", wi ll be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers.

[0154] Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.

Claims

- J -

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1) A system for regulating soil temperature, the system including:

b) a solar collector thermally coupled to the heat transfer loop;

d) a soil temperature sensor for sensing a soil temperature i the soil;

f) a controll er for controlling operation of the pump using the soil temperature and th external temperature so that the pump operates when the heat exchange between the solar collector and the soil will act to reduce a temperature difference betwee the soil temperature and a predetermined soil temperature, to thereby regulate the soil temperature.

2) A system according to claim 1 , wherei the solar collector is connected to the heat transfer loop such that the heat transfer medium can flow through the solar collector,

3) A system according to claim 1 or claim 2, wherein the controller is configured to;

a) determine, based on the temperature difference, whether heating or cooling of the soi l is required;

c) cause the pump to operate if one of:

ii) cooling of the soil is required and it is determined that the heat exchange between the solar collector and the soil will cool the soil .

4) A system according to any one of claims 1 to 3, wherein the controller is configured to only cause operation of the pump if the temperature difference is greater than a predetermined temperature difference threshold. 5) A system according to any one of claims 1 to 4, wherein the external temperature sensor is positioned proximate the solar collector.

6) A system according to claim 5, wherein the system include a return temperature sensor for sensing a return temperature indicative of a temperature of the heat transfer medium that has flowed through the buried loop portion, the controller being configured to control the pump by comparing the external temperature and the return temperature.

7) A system according to claim 6, wherein the controller is configured so that, when the soil temperature is below the predetermined soil temperature, the controller causes operation of the pump when the external temperature is greater than the return temperature, to thereby cause heating of the soil.

8) A system according to claim 6 or claim 7, wherein the controller is configured so that, whe the soil temperature is above the predetermined soil temperature, the controller causes operation of the pump when the external temperature is less than the return temperature, to thereby cause cooling the soil.

9) A system according to any one of claims 6 to 8, wherein the controller is configured to cause operation of the pump when a return temperature difference between the external temperature and the return temperature is greater than a predetermined return temperature threshold.

10) A system according to any one of claims 6 to 9, wherein the system includes a return tank for storing heat transfer medium that has flowed through the buried loop portion.

11) A system according to claim 10, wherein the return temperature sensor is provided in. the return tank.

12) A system according to claim 10 or claim 1 1, wherein the pump is positioned between the return tank and the solar collector.

13) A system according to any one of claims 1 to 12, wherein the system includes a plurality of soil temperature sensors including at least one of:

b) a buried soil temperature sensor positioned in the soil at a predetermined depth beneath th soil surface and proximate the buried loop portion;

c) a loop soil temperature sensor positioned in the soil at a depth similar to a burial depth of the buried loop portion and proximate the buried loop portion; and, d) an offset soil temperature sensor positioned in the soil at a depth similar to a burial depth of the buried loop portion and offset from the buried loop portion by a predetermi ed offset amount.

14) A system according to claim 13, wherein the controller is configured to control the pum based on respective soil temperatures Sensed by two or more of the plurality of soil temperatures.

15) A system according to claim 14, wherein the controller is configured to:

a) determine an average soi l temperature using the respective soil temperatures; and, b) control the pump by comparing the average soil temperature with the predetermined soil temperature,

16) A system according to any one of claims 1 to IS, wherein the system further includes at least one ambient soil temperature sensor including at least one of:

a) an ambient upper soil temperature sensor positioned in the soil substantially at a soil surface and sufficiently separated from the buried loop portion so as to be substantially unaffected by heat exchange between the heat transfer medium and the soil; and,

b) an ambient buried soil temperature sensor positioned in the soil at a predetermined depth and sufficiently separated from the buried loop portion so as to be substantially unaffected by heat exchange between the heat transfer medium and the soil.

17) A system according to claim 16, wherein the controller is configured to control the pump using the at least one ambient soil temperature sensor.

18) A system according to any one of claims 1 to 17, wherein the system further includes an auxiliary heater connected to the heat transfer loop, whereby, when the auxiliary heater is activated, the heat transfer medium in the heat transfer loop is heated when the heat transfer medium flows through the auxiliary heater.

19) A system according to claim 18, wherein the controller is configured to control activation of the auxiliary heater so that the auxiliar heater is activated when the soil temperature is below the predetermined soil temperature and the soil is not being heated using heat exchange between the solar collector and the soil.

20) A system according to claim 18 or claim 19, wherein the auxiliary heater includes a heat pump. 21) A system according to any one of claims 18 to 20, wherein the auxiliary heater is electrically powered,

22) A system according to any one of claims 18 to 20, wherein the auxiliary heater is a gas heater.

23) A system according to any one of claims I to 17, wherein the system further includes an auxiliar chiller connected to the heat transfer loop, whereby, w en the auxiliary chiller is activated, the heat transfer medium in the heat transfer loop is chilled when the heat transfer medium flows throug the auxiliary chi ller.

24) A system according to claim 23, wherein the controller is configured to control activatio of the auxiliary chiller so that the auxiliary chil ler is acti vated when the soil temperature is above the predetermined soil temperature and the soil is not being chilled using heat exchange between the solar collector and the soil .

25) A system according to any one of claims 18 to 24, wherein the system further includes a valve for controlling a flow of the heat transfer medium through the solar collector.

26) A. system according to claim 25, wherein the controller is configured to control the valve based on the soil temperature.

27) A system according to claim 25 or claim 26, wherein die valve has a first valve position for allowing the heat transfer medium to flow through the solar collector and a second valve position for causing the heat transfer medium to bypass the solar collector,

28) A system according to claim 27, wherein the controller is configured to control the valve so that the valve is moved into the second valve position when the soil temperature is below the predetermined soil temperature and the external temperature is less than a return temperature of the heat transfer medium that has flowed through the buried loop portion.

29) A system according to any one of claims 1 to 28, wherein the controller is a programmable logic control ier,

30) A system according to any one of claims I to 29, wherein the. controller is configured to receive an input from at least the soil temperature sensor and the external temperature and provide an output to at least a pump relay for controlling the pump.

31) A system according to any one of claims 1 to 30, wherei the system further includes a data logger for logging temperatures sensed by at l east one of the temperature sensors. 32) A system according to any one of claims 1 to 3 , wherein the solar collector is installed on a roof of a building.

33) A system according to any one of claims 1 to 32, wherein the system further includes a solar power generator for generating electrical power to drive at least the pump.

34) A system according to claim 33, wherein the system further includes an energy store for storing energy generated by the solar power generator,

35) A system according to any one of claims 1 to 34, wherein the solar collector is thermally coupled to the heat transfer loop using a heat exchanger for exchanging heat between the heat transfer loop and a heat exchanger loop connected the soiar collector.

36) A system according to claim 35, wherein a heat transfer medium including an antifreeze mixture is provided in the heat exchanger loop.

37) A system according to any one of claims 1 to 36, wherein the system further includes thermostatic mixing valve for controlling a temperature of the heat transfer medium flowing into the buried loop portion.

38) A system according to claim 37, wherein the thermostatic mixing valve is for supplying an output flow of heat transfer medium by mixing:

a) a first input flow of heat transfer medium that has been heated using one of the solar collector and an auxiliary heater; and,

b) a second input flow of heat transfer medium that has flowed through the buried loo portion.

39) A system according to claim 37 or claim 38, wherein the system includes a mixing valve bypass for allowing heat transfer medium to bypass the thermostatic mixing valve.

40) A system according to claim 39, wherein the system includes a bypass valve for controlling whether heat transfer medium bypasses the thermostatic mixing valve via the mixing valve bypass.

41) A system according to any one of claims 1 to 40, wherein the system further includes a cooling loop such that the heat transfer medium can be diverted through the cooling loop to allow cooling of the heat transfer medium .

42) A system aceording to claim 41, wherein the system includes a diversion valve at each end of the buried loop portion of the heat transfer loop, the diversion valves being for controlling whether the heat transfer medium is diverted through the cooling loop. 43) A system according to any one of claims 1 to 42, wherein the system includes reversal valves for allowing a flow direction of the heat transfer medium through the heat transfer loop to be reversed.

44) A method of regulating soil temperature, the method being performed using a system including:^'

b) a solar collector thermally coupled to the heat transfer loop;

d) a soil temperature sensor for sensing a soil temperature in the soil

f) a controller, wherein the method includes using the controller to control operation of the pump using the soil temperature and the externa! temperature so that the pum operates when heat exchange between the solar collector and the soil will act to reduce a temperature difference between the soil temperature and a predetermined soil temperature,; to thereby regulate the soil temperature.