US20090320829A1

US20090320829A1 - Monitoring apparatus

Info

Publication number: US20090320829A1
Application number: US12/491,832
Authority: US
Inventors: John David Aitken
Original assignee: Inform Energy Pty Ltd
Current assignee: Inform Energy Pty Ltd
Priority date: 2008-06-27
Filing date: 2009-06-25
Publication date: 2009-12-31
Also published as: AU2009202524A1

Abstract

Apparatus for monitoring a solar thermal system, the solar thermal system being for recovering heat energy by heating a heat transfer medium, the apparatus including a processing system for determining a flow rate of the heat transfer medium, determining a temperature change for the heat transfer medium, causing data to be stored based on the determined flow rate and the temperature change, the data being at least partially indicative of an amount of heat energy recovered.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method and apparatus for use in monitoring a solar thermal system, and in particular, to a method and apparatus for monitoring a solar thermal system to allow determination of heat energy recovered.

DESCRIPTION OF THE PRIOR ART

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 specification relates.
It is known to provide solar thermal system, which typically operate by heating a heat transfer medium, such as water or a thermal oil, using solar radiation. The heat transfer medium is used to store energy, allowing this to be recovered for a range of purposes, such as generating electricity, hot water, or the like.
Such solar thermal systems are often used by entities as part of an emissions control program. In this regard, as solar thermal systems generate energy without emitting greenhouse gases such as CO₂, this allows the entity to offset positive emissions from other sources. This can be achieved using any suitable mechanism, such as a carbon trading scheme or the like. To allow such offsetting to be performed, it is necessary to be able to determine the amount of energy recovered using the solar thermal system, and hence the amount of emissions saved.
Current techniques for determining energy generated typically involve estimation based on sunlight levels, or measurement of a resulting output, such as generated electricity. However, estimates provided by these techniques are extremely inaccurate. For example, the system may not be active during all sunlight hours, whilst monitoring generated electricity fails to take into account energy losses during the conversion of heat to electricity.

SUMMARY OF THE PRESENT INVENTION

The present invention seeks to substantially overcome, or at least ameliorate, one or more disadvantages of existing arrangements.
In a first broad for the present invention seeks to provide apparatus for monitoring a solar thermal system, the solar thermal system being for recovering heat energy by heating a heat transfer medium, the apparatus including a processing system for:

- a) determining a flow rate of the heat transfer medium;
- b) determining a temperature change for the heat transfer medium; and,
- c) causing data to be stored based on the determined flow rate and the temperature change, the data being at least partially indicative of an amount of heat energy recovered.

Typically the data includes at least one of:

- a) the flow rate;
- b) the temperature change; and,
- c) the amount of heat energy recovered.

Typically the processing system is for calculating the amount of heat energy recovered using the flow rate and the temperature change.
Typically the processing system is for at least one of:

- a) storing the data in a store; and,
- b) transferring the data to a remote processing system for storage.

Typically, at least one of:

- a) the processing system includes a store; and,
- b) a store is selectively connectable to the processing system.

Typically the processing system is for:

- a) determining a time at which the flow rate and temperature change are determined; and,
- b) causing an indication of the time to be stored as a time stamp associated with the data.

Typically the processing system is for encrypting at least some of the data prior to storage.
Typically the apparatus includes:

- a) a flow sensor; and,
- b) at least one temperature sensor.

Typically the flow sensor is provided in a connecting pipe coupled to an inlet or outlet of the solar thermal system.
Typically apparatus includes:

- a) a first temperature sensor for sensing a first temperature indicative of heat transfer medium supplied to an inlet of the solar thermal system; and,
- b) a second temperature sensor for sensing a second temperature indicative of heat transfer medium received from an outlet of the solar thermal system.

Typically the processing system is for:

- a) receiving signals from the first and second temperature sensors; and,
- b) using the signals to determine the temperature change.

Typically the processing system is for selectively activating the solar thermal system.
Typically the processing system is for selectively activating the solar thermal system in accordance with environmental conditions determined from an environment sensor.
Typically the processing system is for selectively activating a pump to thereby pump heat transfer medium through the solar thermal system.
Typically the solar thermal system includes at least one solar collector, the processing system being for selectively positioning the solar collector in use.
Typically the at least one solar collector includes:

- a) a heat tube for containing the heat transfer medium; and,
- b) a reflector for reflecting solar radiation towards the heat tube.

Typically the reflector has a substantially parabolic cross sectional shape to define a focal axis, the heat tube being positioned substantially aligned with the focal axis.
Typically the solar collector includes a framework for supporting the heat tube relative to the reflector.
Typically the solar collector is moveably mounted to a support to thereby allow the solar collector to be moved between operative and inoperative positions.
Typically the apparatus includes:

- a) a drive system; and,
- b) a controller coupled to the drive system for selectively moving the solar collector between the operative and inoperative positions.

Typically the solar collector includes an impact protection layer provided on a reverse side of the reflector.
Typically, in an inoperative position, the impact protection layer is facing away from the surface.
Typically the solar thermal system is coupled to a heat system via feed lines, and wherein, in use, the feed lines are at least one of:

- a) unpressurised; and,
- b) drained when the solar collector is not in use.

Typically the solar collector includes a heat tube for containing the heat transfer medium and wherein, in use, the heat tube is at least one of:

- a) unpressurised; and,
- b) drained when the solar collector is not in use.

Typically the processing system includes:

- a) an interface for receiving signals from at least one sensor; and,
- b) a processor for
  - i) determining the flow rate and temperature change; and,
  - ii) causing data to be stored based on the determined flow rate and the temperature change, the data being at least partially indicative of an amount of heat energy recovered.

Typically the processing system includes a memory for storing the data.
In a second broad for the present invention seeks to provide a method for monitoring a solar thermal system, the solar thermal system being for recovering heat energy by heating a heat transfer medium, the method including in a processing system:

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described with reference to the accompanying drawings, in which:—

FIG. 1 is a schematic diagram of an example of monitoring apparatus for a solar thermal system;

FIG. 2 is a flow chart of an example of a monitoring process performed by the monitoring apparatus of FIG. 1;

FIG. 3 is a schematic diagram of an example of a processing system;

FIG. 4 is a schematic diagram of an example of a solar thermal system including a solar thermal array;

FIGS. 5A and 5B are schematic side and plan views of the solar array of FIG. 4;

FIGS. 6A and 6B are schematic side views of a solar array in operative and inoperative positions respectively; and,

FIG. 7 is a flow chart of an example of a monitoring process for the apparatus of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of monitoring apparatus for a solar thermal system will now be described with reference to FIG. 1.
In this example the apparatus includes a solar thermal system 100, such as a solar array, coupled to a heat system 110. The heat system 110 may be any form of system that is able to utilise heat from the solar thermal system, and this could therefore include a heat storage vessel, allowing heat to be stored for later use, or a device that operates directly from heat generated by the solar thermal system 100, such as an absorption chiller, generator, Stirling engine, or the like.
In one example, the heat system 110 is coupled to the solar thermal system 100 via connecting pipes 120, 122, allowing a heat transfer medium, such as water or a thermal oil, to be circulated between the heat system 110 and the solar thermal system 100, as shown by the arrows 123, 124. Accordingly, it will be appreciated that the connecting pipe 120 is coupled to an inlet of the solar thermal system 100, with the connecting pipe 122 being coupled to an outlet. Generally, circulation of the heat transfer medium is achieved using a pump 121.
The apparatus includes a processing system 130 which can optionally be coupled to the solar thermal system 100 and the heat system 110 allowing their operation to be controlled. Additionally, the processing system 130 is typically coupled to the pump 121 to allow circulation of the heat transfer medium to be controlled.
In addition to this, in this example the processing system 130 is also coupled to a flow sensor 131 as well as first and second temperature sensors 132, 133.
The flow sensor 131 generates signals indicative of a flow rate of the heat transfer medium, and provides these to the processing system 130, allowing the flow rate to be determined and/or monitored, as well as being optionally controlled. The nature of the flow sensor will vary depending on the preferred implementation, and this could include for example a turbine flow sensor immersed within the heat transfer medium. As the heat transfer medium is typically relatively incompressible, the flow rate of the heat transfer medium will be substantially the same throughout the connection pipes 120, 122, allowing the flow sensor 131 to be positioned anywhere along the pipes 120, 122. As a further alternative, a flow rate may be derived based on operation of the pump 121, in which case a sensor may be incorporated into the pump 121, or may not be required.
The first and second temperature sensors 132, 133 sense temperatures indicative of the temperature of heat transfer medium supplied to or received from the solar thermal system 100. The temperature sensors 132, 133 typically generate signals indicative of the sensed temperatures and these can be provided to the processing system 130, allowing respective temperatures and/or a temperature change of the heat transfer medium temperature, to be determined. As there may be minor temperature variations along the lengths of the connecting pipes 120, 122, in one example, the first and second temperature sensors are provided near the inlet and outlet of the solar thermal system 100.
Thus, in use the processing system 130 can monitor signals from the flow and temperature sensors 131, 132, 133, allowing operation of the solar thermal system 100 to be monitored. An example of this process will now be described with reference to FIG. 2.
In this example, at step 200 the solar thermal system 100 is optionally controlled. As will be described in more detail below, this can involve any suitable form of control, such as positioning of solar collectors, activation of the solar thermal device 100, or the heat system 110. This may also involved controlling operation of the pump 121 to thereby selectively circulate heat transfer medium. It will be appreciated that this may not be required, for example if separate control mechanisms are provided.
At step 210 the processing system 130 operates to determine a heat transfer medium flow rate, which is typically achieved by having the processing system 130 receive signals from the flow rate sensor 131, or pump 121 and then interpret the signals allowing the flow rate to be determined.
At step 220 the processing system 130 determines a heat transfer medium temperature change, and this is typically performed on the basis of the signals received from the first and second temperature sensors 132, 133.
At step 230 the processing system 130 optionally determines an amount of heat energy recovered by the solar thermal system 100. The energy generated can be determined based on the specific heat capacity of the heat transfer medium, the change in temperature and the flow rate, using the equation:
ΔQ=mcΔT

- where: ΔQ—recovered heat energy;
  - m—mass of heat transfer medium (determined from the flow rate and density);
  - c—specific heat capacity of heat transfer medium; and,
  - ΔT—change in temperature of heat transfer medium.

At step 240 data indicative of heat energy recovered is stored by the processing system 130. This may be achieved in any one of a number of manners. Thus, in one example, the processing system 130 can store the signals received from the sensors, or values derived therefrom. Thus for example the processing system 130 could store an indication of the flow rate and the corresponding change in temperature. Alternatively, the processing system 130 can simply store an indication of the energy generated, as determined at step 230 above.
Accordingly the above described process allows the processing system 130 to monitor operation of the solar thermal system and record associated data such as a flow rate of and temperature change in the thermal transfer medium. This in turn allows the data to be used to calculate the energy recovered by the solar thermal system, such as a BTU (British Thermal Unit) value.
In one example, the processing system 130 is adapted to store the data locally. This can be achieved for example by storing the data in an internal memory, allowing this to be subsequently retrieved. A further option is for the processing system 130 to be coupled to a remote repository or other data store, via a suitable communication system, such as a computer network, wireless network or the like. In this example, the processing system 130 can be adapted to store the information remotely, for example by transferring the data to a remote processing system for storage.
A further alternative is for the data to be stored by the processing system 130 on a removable media, such as a memory card, USB key, or the like, allowing the data to be subsequently retrieved from the processing system for analysis. This could be achieved by having the processing system 130 store the data directly on the removable media, or alternatively could involve the temporary storage in local or internal memory, with subsequent transfer to the removable storage media.
Use of removable storage media can be particularly beneficial if the solar thermal system is located in a remote environment, as the system may only be physically attended periodically. In this situation, the removable media card can simply be removed from the processing system 130 and replaced with a new card, allowing the media card and hence data to be removed offsite for analysis. This allows the data to be readily transferred offsite without requiring complex reading equipment, such as a laptop, or the use of communications network, which can be expensive, particularly in remote regions.
In one example, transferring data offsite can be used to provide the data to an independent assessor that performs calculations to determine information such as the heat energy recovered, and consequently any greenhouse gas emissions that can be offset. This can be used to allow independent validation of emission savings, which in turn can be used to allow trading of the emissions, although this may not be required in all circumstances.
Transfer of data can also be performed so that the processing system 130 need only store data, allowing the subsequent analysis and determination of heat energy recovered to be performed remotely. This can be used to reduce computational requirements on the processing system 130, which can in turn reduce the complexity and cost of the apparatus.
Transfer of the data can be achieved in any suitable manner, and could be performed via a communications network as outlined above. However, in one example, this is achieved by physically transferring the removable media, using a suitable mechanism such as the postal service, or the like. This can be used to minimise costs, as compared to download via a GSM network or the like. Additionally, by suitable configuration of the memory card, this reduces the chance of data being tampered with, for example by manipulating the data to artificially inflate the amount of heat energy recovered, and thereby manipulate the CO₂emission savings determined.
The media card could be configured in a number of manners. For example, a custom format of card can be used for which readers are not generally available, reducing the opportunity for individuals to interact with the stored data. The memory card could be configured to allow communicate with a respective processing system 130, which could be achieved through the use of encryption protocols, or the like.
An alternative option is to store the data in some manner that prevents data manipulation, and this can be used either with a media card, or transfer in any other manner. Thus for example, the stored data could be provided with a time stamp representing the time the data was last altered, thereby indicating if data has been manipulated after initially being recorded. The data could be encrypted, for example, using public/private key encryption, so that it can only be accessed or stored with knowledge of a private key. Other suitable mechanisms may also be used.
In one example, the data may be stored in any suitable format suitable for retrieval by a separate device, such as a suitable computer system, or the like. In one example, the data is stored in a format, such as FAT32, which allows storage on existing forms of media and which is compatible with most computer systems, thereby allowing for easy retrieval without requiring the use of specialised equipment.
It will therefore be appreciated that the above described apparatus allows a monitoring system to be provided that is capable of measuring the energy recovered by a solar thermal system. This not only acts as useful reference data, allowing operators of the solar thermal system to determine its operational capabilities, but also allows the information to be used in a number of other manners, such as in assessing emissions offsets, or the like.
In one example, the data is stored to removable media, allowing the media to be removed from the apparatus and transferred to another location for subsequent analysis. This can advantageously be achieved by a suitable mechanism, such as the postal service, allowing a large volume of data to be transferred whilst avoiding costs associated with data transfer via communications networks, which is of particular concern in remote regions.
In addition to providing monitoring functionality as described above, the processing system 130 can also provide control functionality for the solar thermal unit, as described briefly above with respect to step 200 above.
In one example, the control can involve measuring and adjusting the flow rate of heat transfer medium, thereby allowing the temperature of the heat transfer medium to be controlled. It will be appreciated that such control operations can be performed in accordance with the flow rate and temperature data collected as described above. This can allow therefore allowing the monitoring process to be performed to allow control of the solar thermal system, as will be described in more detail below.
Additional control may be provided in accordance with other information. Thus, for example, this may involve having the processing system monitor environmental conditions, and position a solar collector to maximise solar radiation collection.
The processing system 130 can therefore integrate control and monitoring functionality into a single unit, thereby reducing overall costs and assisting with fitting and maintenance.
It will be appreciated that the processing system 130 can be any suitable form of processing system, and an example will now be described with reference to FIG. 3.
In this example the processing system 130 includes a processor 300, a memory 301, an input/output device 302 and an external interface 303 interconnected via a bus 304. In use the memory 301 is adapted to store instructions which can be accessed by the processor 300 allowing monitoring to be implemented. Thus, for example, this can cause the processor 300 to perform the process outlined above, as well as any other required control functions.
The input/output control 302 may be used to allow indications to be displayed to users, such as an indication of any of the stored data, or any values derived therefrom, as well as to allow user interaction with the processing system 130, for example to allow manual control over any processes implemented by the processing system. The external interface 303 can be used to couple the controller to a communications network, and/or to allow the controller 130 to interface with remote devices, such as a remote storage media shown 310, as well as the flow and temperature sensors 131, 132, 133.
Accordingly, in use signals are received from the flow and temperature sensors 131, 132, 133, via the interface 303, allowing the signals to be transferred to the processor 300. The processor 300 uses the signals to determine a flow rate and temperature change of the heat transfer medium, and optionally perform any required calculations, such as to determine generated energy, in accordance with instructions stored in the memory 301. The processor 300 then records an indication of the measurements, either in the memory 301, to allow subsequent retrieval, and/or in a remote storage media 310.
It will be appreciated from this that the processing system 130 can be any form of suitable processing system including a generic processing system such as a computer system, or the like, or custom configured hardware such as a programmable logic controller, field programmable gate array (FPGA) or the like.
An example in which the solar thermal system is a solar thermal system, and the heat system is a heat storage vessel, will now be described with reference to FIGS. 4 to 7.
In this example, similar reference numerals to those used in FIG. 1 are used for similar components, and these will not therefore be described in any further detail.
The solar array 100 includes a number of solar collectors 400A, 400B (with two being shown for the purpose of illustration only), each having a respective heat tube 401A, 401B. The heat tubes 401A, 401B are connected to each other via a second feed line 410, and to the heat system 110, by the connecting pipes 120, 122. This forms a fluid circuit allowing the heat transfer medium to be pumped from the heat storage vessel 110 through the connecting pipes 120, 122, 410, and the heat tubes 401A, 401B, and returned to the heat storage vessel 110. This is generally achieved using the pump 121, provided in the connecting pipe 120, although any suitable arrangement may be used.
In use, the heat tubes 401A, 401B are provided in the focal region of respective reflectors, allowing solar radiation to be focused thereon, as will be described in more detail below, thereby heating the heat transfer medium flowing therethrough.
In one example, a heat transfer medium such as a high temperature thermal oil is preferred as this generally has a high specific heat capacity and a high boiling point (relative to other typical heat transfer mediums such as water). As a result, the thermal oil can be heated to a much higher temperature without risk of the oil boiling. The oil also stores a greater amount of heat for a given temperature change than other fluids such as water. This makes it particularly useful in solar heat recovery, as it allows a large amount of heat to be recovered, without requiring pressurisation of the connecting pipes 120, 122, 410 and the heat tubes 401 to prevent boiling of the oil. To further ensure boiling does not occur, the solar collectors can be drained of any heat transfer medium when not in use.
Being able to avoid the need for pressurisation vastly reduces the complexity of the equipment and in turn allows cheaper materials to be used in construction, thereby reducing construction, installation and maintenance costs.
However, pressurised systems can be used, as can alternative heat transfer mediums, such as water.
In the event that thermal oil is used as the heat transfer medium, the heat storage vessel 110 is generally formed from a fully (double) bunded unpressurised tank, to thereby ensure safe storage of the thermal oil. Fully bunded tanks include a double skin so that the heat storage vessel effectively includes an inner tank positioned within an outer tank.
The inner tank is used as the primary form of storage but if it is overfilled or leaks, a pollution incident is avoided because the liquid collects in the outer tank, from where it can be disposed of in a safe manner. Additionally, the double skin arrangement can be used to improve the thermal insulation properties of the heat storage vessel, improving the heat retention properties as will be appreciated by those skilled in the art.
In this example, the processing system 130 acts as a controller controlling the operation of the pump 121, the solar collectors 400A, 400B, and any control valves provided in the feed lines.
In order to achieve this, the processing system 130 may be coupled to one or more sensors for sensing operating conditions. This can include, for example, an environment sensor 431 for determining information relating to one or more environmental attributes such as the levels of incident solar radiation, levels of wind, the likelihood of hail, or the like. A heat storage vessel temperature sensor 432 may be provided for sensing the temperature of the heat storage vessel 110 and/or heat transfer medium contained therein.
An example of the solar collectors shown in more detail in FIGS. 5A and 5B.
In this example, the solar collector 400 is generally formed from a reflective surface 500, with the heat tube 401A, 401B being held in position relative to the reflective surface using a framework 501 or the like. The reflective surface may be formed from a variety of materials, such as silvered glass, a mirror surface, electro-polished stainless steel, or the like, depending on the preferred implementation. The reflective surface 500 is typically parabolic in cross-sectional shape to focus sunlight onto a focal axis, with the heat tubes 401A, 401B, being aligned with the focal axis to thereby maximise heating of the heat transfer medium provided therein.
The solar collector 400 may also include an impact protection layer 503 mounted on a reverse side of the reflective surface 500, to thereby prevent damage to the surface during adverse weather, such as hail storms or the like.
Each heat tube 401 is generally formed from an outer tube 510 and an inner tube 511 which contains the heat transfer medium, in use. A vacuum is provided between the inner and outer tubes 511, 510, to reduce heat losses from the heat transfer medium through convection and conduction processes.
The ratio of the surface area of the heat tubes 401 and of the reflective surface 500 can provide up to a 400:1 increase in solar energy collection, whilst heat loss from the heat tube 401 is reduced by the surrounding vacuum. As this can result in high temperatures within the heat tubes 401, it is preferable to use a fluid with a high boiling point, such as thermal oil, as will be described in more detail below.
In one example, the solar collector 400 is typically mounted to a surface as shown in FIGS. 6A and 6B.
The solar collector 400 is mounted to the surface 600 using a support structure 601. The support structure 601 can be coupled to the framework 501, or any other part of the solar reflector 400, depending on the preferred implementation. In one example, this is achieved using a pivotal mounting, shown generally at 602. This allows the solar collector to be moved between an operative position shown in FIG. 6A, and an inoperative position shown in FIG. 6B.
In the operative position, the reflective surface 500 faces away from the surface 600, allowing the reflective surface 500 to be exposed to solar radiation. This, in turn, allows sunlight to be reflected from the reflective surface 500 onto the heat tube 401A, 401B thereby heating the fluid transfer medium provided therein.
In contrast, in the inoperative position, the reflective surface 500 faces generally downwards towards the surface 600. As a result, the impact protection layer 503 faces upwards, thereby preventing the reflective surface 500 from being damaged by impacts from falling objects, such as hailstones, or the like. Thus by placing the solar collectors 400A, 400B in the inoperative position when not in use, this prevents damage to the solar collector, and in particular the reflective surface 500, thereby increasing the solar collector's life span.
The impact protection layer may be formed from any suitable material depending on the preferred implementation, and the level of protection required. For example, in regions prone to large hailstones, then it is typical to provide a one inch (2.5 cm) thick layer of silvered foam insulation, which is relatively cheap and yet capable of absorbing hailstone impacts. However, it will be appreciated that a greater or lesser degree of protection may be provided.
In addition to moving the solar collector between the inoperative and operative positions, it may also be possible to orientate the solar collector at intermediate positions, to maximise exposure of the reflective surface 501 to solar radiation, based on the current sun position. Thus, for example, in the early morning and late afternoon, the sun will typically be situated near the horizon, in which case, the reflective surface may need to be directed towards the horizon (parallel to the surface 600) instead of upwards substantially perpendicular to the surface 600, as shown in FIG. 6A.
It will therefore be appreciated from the above that the solar collector may be placed in any suitable orientation depending on the implementation and current operating conditions.
In general, movement of the solar collectors 100A, 100B between the inoperative and operative positions can be achieved using any suitable drive system, such as a motor 434A, 434B for each solar collector. Operation of the motors is can be controlled by processing system 130, allowing the orientation of the solar collectors to be adjusted as required.
It will be appreciated however that the use of solar collectors 400A, 400B is for the purpose of example only, and that in practice any form of system that allows heating of a heat transfer medium may be used.
In use, the processing system 130 can control the pump 121, to control the rate of flow of heat transfer medium through the solar collectors 400A, 400B. This allows the processing system 130 to control the duration for which the heat transfer fluid is in the heat tubes 401A, 401B, which in turn can be used to control the amount of heat provided to the heat transfer medium.
Additionally, the connecting pipes 120, 122, 410, and the heat tubes 401A, 401B can be drained by allowing the heat transfer medium to return to the heat storage vessel 110 when further heating is not required. As a result, the degree of heating provided to the heat storage vessel 110 can be controlled.
As this arrangement can be used to control the temperature of the heat transfer medium and the heat storage vessel 110, this can be used to ensure that the heat transfer medium does not undergo a phase change, such as boiling, thereby obviating the need for a pressurised system. Thus, for example, if thermal oil is used as the heat transfer medium, a sufficiently high flow rate through the heat tubes 401A, 401B can be maintained to ensure the oil does not boil under atmospheric pressure, before being returned to the heat storage vessel 110.
In addition to this, the processing system 130 may be adapted to control the orientation of the solar collectors 100, based on signals from the environment sensor 431. This allows the solar collectors 100 to be orientated to maximise heat collection, as well as to be placed in the inoperative position either when inclement weather is likely, or when solar heating is not required. This helps maximise efficiency of the system, whilst reducing the likelihood of damage to the solar collectors 100A, 100B.
An example of the operation of the processing system 130 to control and monitor the arrangement of FIG. 4, will now be described with reference to FIG. 7.
At step 700 the processing system 130 monitors the temperature of the heat storage vessel 110 utilising the heat storage vessel temperature sensor 432. At step 710 the processing system 130 determines if heating is required. It will be appreciated that this may be achieved in any one of a number of ways. For example, this may involve comparing the current heat storage vessel temperature to a predetermined threshold, or the like.
The threshold value could be stored in the memory 301 allowing the processor 300 to perform the comparison. Such thresholds can be stored in memory 301 in the form of an LUT (Look Up Table), or the like, as will be appreciated by those skilled in the art.
If it is determined that heating is required at 710 the processing system 130 moves on to step 720 to determine if suitable conditions are present for performing heating using solar power. This may involve having the processing system 130 determine signals from the environment sensor 431 to determine if environmental conditions are appropriate, for example, if there is sufficient light to allow heating of the heat transfer medium. Thus, if it is currently night time, the processing system 130 will determine that heating cannot be achieved and hence that the solar collector should not be used.
It will be appreciated that other environmental conditions may also be examined, such as current wind velocity levels, the likelihood of hail or the like. This information may be obtained from the environmental sensor 431 and/or a remote computer system, such as a meteorological computer system, web-site, or other service. Thus, it will be appreciated that in one example the environmental sensor 431 could include a remote computer system adapted to provide meteorological or other environmental information.
If the current conditions are not suitable for performing solar collection, the processing system 130 can wait until changed conditions occur and heating can be performed, or cause an alternative heat source to be used at step 730. If this occurs, an indication of this may be stored in a log, or the like, together with any other relevant environment data, allowing the cause to be subsequently examined. This can be used in fault detection, as well as assisting in determining effective operating parameters, to thereby maximise efficiency.
Once it is determined that heating can be performed at step 740 the processing system 130 activates the pump 121 and positions the solar arrays 100A, 100B to allow heating of the heat transfer medium. This may involve positioning the solar arrays in an optimum operative position, depending on current prevailing conditions, such as the location of the sun relative to the solar array.
A required flow rate and corresponding pump speed may also be determined from memory 301. This may be in the form of a fixed flow rate, which can therefore be predefined and stored for example in the memory 301. Alternatively, this may involve selecting a flow rate based on the current ambient light incident on the solar collectors, and the temperature of the heat storage vessel 110.
It will be appreciated that the required flow rates will also typically depend on factors, such as the dimensions and in particular, the cross sectional area of the connecting pipes 120, 122, 410, and the heat tubes 401A, 401B, and would therefore typically need to be pre-stored in memory depending on the constructional of the system.
At step 750 the processing system 130 monitors signals from the flow sensor 131 to determine the flow rate of the heat transfer medium. The first and second temperature sensors 132, 133 are also monitored, allowing the temperature change in the heat transfer medium to be determined at step 760. Following this, at step 770 the processing system 130 optionally determines the heat energy stored, allowing data to be stored in an audit log, at step 780.
As mentioned above, the data stored can include any relevant data, and can include:

- a time and/or date stamp;
- first and second temperatures for the heat transfer medium;
- a temperature change;
- a flow rate;
- environment condition information; and,
- a heat storage vessel temperature.

The data may also be encrypted or otherwise protected, for example through the use of a hash verification value.
Following this, the processing system continues to monitor the temperature of the heat storage vessel 110 at step 700 until the processing system 130 determines that the heat storage vessel 110 no longer requires heating. This will occur for example if the temperature of the heat storage vessel 110 reaches a predetermined maximum threshold representing the maximum heat storage capability of the heat storage vessel 110.
At this stage, if it is determined that no further heating is required the processing system 130 can deactivate the pump 111 and optionally drain the connecting pipes 120, 122, 410 as well as the heat tubes 401A, 401B. The processing system 130 may additionally return the solar collectors to inoperative positions.
Periodically the stored data can be retrieved and/or analysed, allowing a total heat energy recovered to be determined, which in turn can be used to calculate CO₂offsets or other emissions information.
Accordingly, the above described apparatus provide a mechanism for monitoring energy recovered from solar radiation by solar thermal systems. This is typically achieved by measuring a flow rate and temperature change in a heat transfer medium, allowing an energy measure, such as a BTU value, to be determined. In one example, data is recorded on a removable media, such as a memory card, allowing it to be posted for subsequent analysis and/or verification, thereby saving data transfer costs.
The monitoring process can be combined with control functionality to allow the solar thermal system and any associated apparatus to be controlled. This allows a single controller or other processing system to act as both a control and monitoring system. This in turn has cost benefits in reducing the number of components required, particularly as some sensors may be used both in controlling and monitoring of the solar thermal system. It will be appreciated that this can assist particularly in retrofitting to existing solar thermal systems.
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

1) Apparatus for monitoring a solar thermal system, the solar thermal system being for recovering heat energy by heating a heat transfer medium, the apparatus including a processing system for:

a) determining a flow rate of the heat transfer medium;

b) determining a temperature change for the heat transfer medium; and,

c) causing data to be stored based on the determined flow rate and the temperature change, the data being at least partially indicative of an amount of heat energy recovered.

2) Apparatus according to claim 1, wherein the data includes at least one of:

a) the flow rate;

b) the temperature change; and,

c) the amount of heat energy recovered.

3) Apparatus according to claim 1, wherein the processing system is for calculating the amount of heat energy recovered using the flow rate and the temperature change.

4) Apparatus according to claim 1, wherein the processing system is for at least one of:

a) storing the data in a store; and,

b) transferring the data to a remote processing system for storage.

5) Apparatus according to claim 1, wherein, at least one of:

a) the processing system includes a store; and,

b) a store is selectively connectable to the processing system.

6) Apparatus according to claim 1, wherein the processing system is for:

a) determining a time at which the flow rate and temperature change are determined; and,

b) causing an indication of the time to be stored as a time stamp associated with the data.

7) Apparatus according to claim 1, wherein the processing system is for encrypting at least some of the data prior to storage.

8) Apparatus according to claim 1, wherein the apparatus includes:

a) a flow sensor; and,

b) at least one temperature sensor.

9) Apparatus according to claim 8, wherein the flow sensor is provided in a connecting pipe coupled to an inlet or outlet of the solar thermal system.

10) Apparatus according to claim 1, wherein apparatus includes:

a) a first temperature sensor for sensing a first temperature indicative of heat transfer medium supplied to an inlet of the solar thermal system; and,

b) a second temperature sensor for sensing a second temperature indicative of heat transfer medium received from an outlet of the solar thermal system.

11) Apparatus according to claim 10, wherein the processing system is for:

a) receiving signals from the first and second temperature sensors; and,

b) using the signals to determine the temperature change.

12) Apparatus according to claim 1, wherein the processing system is for selectively activating the solar thermal system.

13) Apparatus according to claim 12, wherein the processing system is for selectively activating the solar thermal system in accordance with environmental conditions determined from an environment sensor.

14) Apparatus according to claim 12, wherein the processing system is for selectively activating a pump to thereby pump heat transfer medium through the solar thermal system.

15) Apparatus according to claim 1, wherein the solar thermal system includes at least one solar collector, the processing system being for selectively positioning the solar collector in use.

16) Apparatus according to claim 15, wherein the at least one solar collector includes:

a) a heat tube for containing the heat transfer medium; and,

b) a reflector for reflecting solar radiation towards the heat tube.

17) Apparatus according to claim 16, wherein the reflector has a substantially parabolic cross sectional shape to define a focal axis, the heat tube being positioned substantially aligned with the focal axis.

18) Apparatus according to claim 16, wherein the solar collector includes a framework for supporting the heat tube relative to the reflector.

19) Apparatus according to claim 16, wherein the solar collector is moveably mounted to a support to thereby allow the solar collector to be moved between operative and inoperative positions.

20) Apparatus according to claim 19, wherein the apparatus includes:

a) a drive system; and,

b) a controller coupled to the drive system for selectively moving the solar collector between the operative and inoperative positions.

21) Apparatus according to claim 16, wherein the solar collector includes an impact protection layer provided on a reverse side of the reflector.

22) Apparatus according to claim 21, wherein, in an inoperative position, the impact protection layer is facing away from the surface.

23) Apparatus according to claim 1, wherein the solar thermal system is coupled to a heat system via feed lines, and wherein, in use, the feed lines are at least one of:

a) unpressurised; and,

b) drained when the solar collector is not in use.

24) Apparatus according to claim 1, wherein the solar collector includes a heat tube for containing the heat transfer medium and wherein, in use, the heat tube is at least one of:

a) unpressurised; and,

b) drained when the solar collector is not in use.

25) Apparatus according to claim 1, wherein the processing system includes:

a) an interface for receiving signals from at least one sensor; and,

b) a processor for

i) determining the flow rate and temperature change; and,

ii) causing data to be stored based on the determined flow rate and the temperature change, the data being at least partially indicative of an amount of heat energy recovered.

26) Apparatus according to claim 25, wherein the processing system includes a memory for storing the data.

27) A method for monitoring a solar thermal system, the solar thermal system being for recovering heat energy by heating a heat transfer medium, the method including in a processing system:

a) determining a flow rate of the heat transfer medium;

b) determining a temperature change for the heat transfer medium; and,