Patent Description:
Today, it is common practice in many parts of the world to provide heating and hot water for houses and buildings via an energy grid. One example of such energy grid is a district heating grid comprising a system of conduits and valves for distributing hot water to the houses and buildings such that the houses can be heated when needed via thermal devices, i.e. heat exchangers, connected to the district heating grid. Alternatively, according to another example, instead of using hot water for providing space heating, gas may be provided to the houses and buildings via the system. By having access to gas, typically a fossil fuel gas, the houses can be heated by using a thermal device in the form of a gas burner. In addition to space heating, the hot water or the gas may be used for preparing hot tap water.

To cool the houses and buildings, similar systems may be used. The general principle of these systems is however the opposite. Instead of providing heat by e.g. providing hot water, heat is collected in the houses and transported away from the houses. District cooling grids, that is, networks of conduits and valves connecting several real estates for cooling purposes, using water as heat carrier are however still rare. The common practice is instead to use electrical energy for running air conditioning systems, which is a disadvantage at least from an environmental perspective.

Even if it is known how to add and control thermal devices, e.g. heat exchanges or heat pumps, to distribution systems once new buildings are built, these can be further improved. One area of improvement is efficient system maintenance. For instance, the prior art does not offer any solutions for detecting problems between the different thermal devices and the whole system. This would improve the overall performance of the system.

<CIT> discloses a district heating arrangement and a method for operating a district heating arrangement. The arrangement includes a heat-producing unit, which provides a hot primary fluid, local units, which each includes a heat-exchanger device, and a conduit network, which includes a feeding conduit for transporting the primary fluid from the heat-producing unit to each local unit. Each local unit receives the primary fluid through the heat-exchanger device for transfer of heat to a secondary fluid flowing through the heat-exchanger device. Each local unit includes first means, which provides at least a first parameter related to the efficiency of the heat transfer. Each local unit includes a communication device, arranged to communicate an instantaneous value of the first parameter to a communication device of the arrangement. Second means co-operate with this communication device and determine the local unit which has the largest need of maintenance depending on the instantaneous value.

It is an object of the present invention to solve at least some of the problems mentioned above.

According to a first aspect, a control unit configured to control an outtake of heat and/or cold of a thermal device from a distribution grid for a fluid based distribution of heat and/or cold is provided. The control unit comprising a communication unit and a control circuit. The communication unit is configured to communicate with a central server using a predetermined rule of communication. The control circuit is configured to execute a monitoring function and a mode setting function. The monitoring function is configured to monitor the communication between the control unit and the central server. The mode setting function is configured to: upon the communication between the control unit and the central server fulfills the predetermined rule of communication, set the thermal device in a normal operation mode, or upon the communication between the control unit and the central server does not fulfill the predetermined rule of communication, set the thermal device in a limited operation mode. The limited operation mode is more restricted than the normal operation mode. In the normal operation mode, the thermal device may be allowed to freely take out heat and/or cold from the distribution grid. In the limited operation mode, the thermal device may be restricted to take out heat and/or cold from the distribution grid below a preconfigured threshold.

As long as the communication works as expected, the control unit may set the thermal device to operate in the normal operation mode, e.g., the thermal device is allowed to freely take out heat and/or cold from the distribution grid. By the present control unit, while the communication works as expected, the central server has control over the thermal device and can therefore optimize the energy efficiency of the distribution grid and the thermal devices connected thereto. By using different operation modes, e.g., the normal operation mode and the limited operation mode, the central server can keep control of how much outtake of heat and/or cold that is taken out from the distribution system. Thus, this can secure good overall performance of the whole thermal energy distribution system comprising the distribution grid and the thermal devices connected thereto. This may also improve the detection of which thermal device that may have problems with the communication between the thermal device and the central server.

The predetermined rule of communication may be a ping communication. Ping measures the round-trip time for messages sent from the originating host to a destination computer that are echoed back to the source. The ping communication may be performed periodically. The term "periodically" refers to that the ping communication is performed recurrently, e.g., once a minute, once an hour, once a day or once a week.

In the normal operation mode, the thermal device may be controllable by the central server. Hence, the central server may send control instructions to the control unit controlling the thermal device.

According to a second aspect, it is provided a method for controlling an outtake of heat and/or cold of a thermal device from a distribution grid for a fluid based distribution of heat and/or cold. The method comprising:.

In the normal operation mode, the thermal device may be allowed to freely take out heat and/or cold from the distribution grid. In the limited operation mode, the thermal device may be restricted to take out heat and/or cold from the distribution grid below a preconfigured threshold. In the normal operation mode, the thermal device may be controllable by the central server.

The above mentioned features of the first aspect, when applicable, apply to this second aspect as well. In order to avoid undue repetition, reference is made to the above.

According to a third aspect, a central server configured to control a controllability of a thermal device connected to a distribution grid for a fluid based distribution of heat and/or cold is provided. The central server comprising a communication unit and a control circuit. The communication unit is configured to communicate with the thermal device using a predetermined rule of communication. The control circuit is configured to execute a monitoring function and a thermal device control function. The monitoring function is configured to monitor the communication between the central server and the thermal device. The thermal device control function is configured to: upon the communication between the central server and the thermal device fulfills the predetermined rule of communication, set the thermal device in a normal operation mode; or upon the communication between the central server and the thermal device does not fulfill the predetermined rule of communication, trigger an alarm indicating a problem with the communication between the central server and the thermal device.

The predetermined rule of communication may be a ping communication. The ping communication may be performed periodically.

The central server may further comprise a database. The control circuit may be configured to execute a register function. The register function is configured to, in the database, indicate the controllability of the thermal device.

The communication unit may be configured to communicate with a plurality of thermal devices using a predetermined rule of communication. The monitoring function may be configured to monitor the communications between the central server and the plurality of thermal devices. The thermal device control function may be configured to, for each of the plurality of thermal devices, determine whether the communication between the central server and the respective one of the plurality of thermal devices fulfills the predetermined rule of communication. The thermal device control function may upon the communication between the central server and a respective one of the plurality of thermal devices fulfills the predetermined rule of communication, set the respective one of the plurality of thermal devices in a normal operation mode; or upon the communication between the central server and the respective one of the plurality of thermal devices does not fulfill the predetermined rule of communication, trigger an alarm indicating a problem with the communication between the central server and the respective one of the plurality of thermal devices.

The register function may further be configured to, in the database, indicate the controllability of each of the plurality of thermal devices.

The above mentioned features of the first and second aspects, when applicable, apply to this third aspect as well. In order to avoid undue repetition, reference is made to the above.

According to a fourth aspect, it is provided a method for checking controllability of a thermal device connected to a distribution grid for a fluid based distribution of heat and/or cold. The method comprising: monitoring a communication between a central server and the thermal device; and upon the communication between the central server and the thermal device fulfills a predetermined rule of communication, setting the thermal device in a normal operation mode, or upon the communication between the central server and the thermal device does not fulfill the predetermined rule of communication, triggering an alarm indicating a problem with the communication between the central server and the thermal device.

The above mentioned features of the first, second and third aspects, when applicable, apply to this fourth aspect as well. In order to avoid undue repetition, reference is made to the above.

Hence, it is to be understood that this invention is not limited to the particular component parts of the device described or steps of the methods described as such device and method may vary. It must be noted that, as used in the specification and the appended claim, the articles "a," "an, " "the," and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise.

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiments of the invention. The figures are provided to illustrate the general structures of embodiments of the present invention.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments are the invention are shown.

<FIG> generally illustrates a distribution system <NUM> for distributing thermal energy. The distribution system <NUM> comprises a thermal server plant <NUM> and a plurality of thermal devices 106a-f. The distribution system <NUM> may comprise more than one thermal server plant <NUM>. One or more thermal devices <NUM> are located in a respective building <NUM>. The building <NUM> may be any type of building suitable for connection to the distribution system <NUM>, such as a residential building, commercial or office building, an apartment building, a free-standing house or an industrial building. The distribution system <NUM> may be a district heating system or a district cooling system known in the art. The district heating system (or a district cooling system) may comprise a supply conduit <NUM> providing heating (or cooling) medium from the thermal server plant <NUM> and a return conduit <NUM> which transport cooled heating medium (or heated cooling medium) to the thermal server plant <NUM>. The heating (or cooling) medium may be any fluid suitable for heating (or cooling) at the thermal server plant <NUM> and transported by means of the supply conduit <NUM> and the return conduit <NUM>, such as water. The heating (or cooling) medium will henceforth be referred to as "thermal fluid". The thermal server plant <NUM> may be a geothermal plant, an electrically powered plant for heating (or cooling) fluids, or may be driven by combustion of fuels, such as gas or oil. The thermal server plant <NUM> is configured to heat (or cool) the heating (or cooling) medium and pump it through the distribution system <NUM>. As an alternative to being a district heating or district cooling system, the distribution system <NUM> may be a combined district heating and cooling system as previously disclosed in, e.g., <CIT> filed by E. ON Sverige AB. In such as case the two conduits <NUM> and <NUM> are not to be seen as supply and return conduits but instead to be seen as a hot conduit and a cold conduit, wherein the hot conduit is configured to hold thermal fluid being warmer than the thermal fluid of the cold conduit.

Hence, the distribution system <NUM> comprises a distribution grid <NUM> having two conduits <NUM>, <NUM> for distributing thermal energy to thermal devices <NUM> connected to the distribution grid. The thermal devices <NUM> being part of the distribution system <NUM>. The thermal devices <NUM> being configured to extract heat from the thermal fluid of distribution grid and/or deposit heat in the thermal fluid of the distribution grid <NUM>. Hence, each of the thermal devices <NUM> is configured to distribute heating and/or cooling inside a building <NUM>. Each of the thermal devices <NUM> can serve one building <NUM> or a plurality of buildings <NUM>. A specific building may comprise one thermal device <NUM>. A specific building may comprise more than one thermal device <NUM>.

<FIG> illustrates a portion of the distribution system <NUM> of <FIG>. In addition to what has been discussed above each thermal device <NUM> is controlled by a control unit <NUM>. Hence, the distribution system <NUM> comprises a plurality of control units <NUM>. Each control unit <NUM> is configured to control at least one thermal device <NUM>. Each thermal device <NUM> may comprise a control unit <NUM> configured to control the thermal device <NUM>. The control unit <NUM> is configured to control an outtake of heat of the thermal device <NUM>, it is configured to control, from the distribution grid <NUM>. Alternatively, or in combination, the control unit <NUM> is configured to control an outtake of cold of the thermal device <NUM>, it is configured to control, from the distribution grid <NUM>.

A specific thermal device <NUM> may be a thermal energy consumer assembly, a thermal energy generator assembly, or a combined thermal energy consumer/generator assembly. A thermal energy consumer assembly is configured to extract heat from the distribution grid <NUM>. Hence, the thermal energy consumer assembly is configured to take out heat from the distribution grid <NUM> and deposit the same in a heating system of a building. The heating system may comprise a comfort heating system, a process heating system and/or a tap hot water system. The thermal energy consumer assembly may comprise a heat exchanger and/or a heat pump configured to extract heat from the distribution grid <NUM>. A thermal energy generator assembly is configured to extract cold from the distribution grid <NUM>. Hence, the thermal energy generator assembly is configured to take out heat from a building using a cooling system and deposit the same in the distribution grid <NUM>. The cooling system may comprise a comfort cooling system, a refrigerator system, a freezing system and/or a process cooling system. The thermal energy generator assembly may comprise a heat exchanger and/or a heat pump configured to extract heat from the building. A combined thermal energy consumer/generator assembly is an assembly that is configured to sometimes act as a thermal energy generator assembly and some other times act as a thermal energy consumer assembly. An example of a combined thermal energy consumer/generator assembly is disclosed in, e.g., <CIT>.

The distribution system <NUM> further comprises a central server <NUM>. The central server <NUM> is configured to communicate with the plurality of control units <NUM>. The communication may be wired or wireless. The communication may be performed using any suitable communication protocol. Such communication is well known to a person skilled in the art and will not be described in any detail herein. The central server <NUM> is configured to send control messages to the plurality of control units <NUM>. A control message may comprise information pertaining to time resolved outtake of heat and/or cold from the distribution grid <NUM>. For example, information pertaining to a time resolved maximum outtake of heat and/or cold from the distribution grid <NUM> or information pertaining to a time resolved minimum outtake of heat and/or cold from the distribution grid <NUM>.

In connection with <FIG> the central server <NUM> will be discussed in more detail. The central server <NUM> comprises a communication unit <NUM>, a control circuit <NUM> and a memory <NUM>.

The central server <NUM> is configured to control a controllability of thermal devices <NUM> connected to the distribution grid <NUM>. The central server <NUM> is configured to control a controllability of a thermal device <NUM> by checking whether a communication path <NUM> between the central server <NUM> and a control unit <NUM> controlling the thermal device <NUM> is open. A communication path <NUM> may, as in the in <FIG> shown example, be bidirectional, i.e. both the central server <NUM> and the control unit <NUM> can initiate a communication on the communication path <NUM>. Alternatively, the communication path <NUM> may be unidirectional, i.e. the central server <NUM> but not the control unit <NUM> can initiate a communication on the communication path <NUM>. The checking of whether a communication path <NUM> between the central server <NUM> and a control unit <NUM> is open may be performed by monitoring if the communication between the central server <NUM> and the control unit <NUM>, i.e. monitoring the communication between the central server <NUM> and the thermal device <NUM>, fulfills a predetermined rule of communication.

The predetermined rule of communication may be a ping communication. The ping communication may be performed periodically, i.e. performed recurrently, e.g., once a minute, once an hour, once a day or once a week. Many kinds of ping communications exist and will not be listed here. Basically, using a ping communication, the central server <NUM> may send a request message to the control unit <NUM>. Upon the control unit <NUM> receive the request message, the control unit <NUM> may send a response message back to the central server <NUM>. Upon the control unit <NUM> receive the request message, it is an indication that the central server <NUM> may initiate a communication with the control unit <NUM>. The central server <NUM> may hence send control messages to the control unit <NUM>. Accordingly, using the ping communication as the predetermined rule of communication it is made possible to check whether the central server <NUM> can send information to the control unit <NUM>. Also, a quality of a communication path <NUM> between the central server <NUM> and the control unit <NUM> may be checked using a ping communication. The central server <NUM> may be configured to initiate the ping communication. By such a ping communication it may be checked whether the central server <NUM> may open a communication with the control unit <NUM>. Using such a communication the central server <NUM> may, e.g., send control instructions to the control unit <NUM>. Alternatively, or in combination, the control unit <NUM> may be configured to initiate a ping communication. By such a ping communication it may be checked whether the control unit <NUM> may open a communication with the central server <NUM>. Using such a communication the control unit <NUM> may, e.g., report information to the central server <NUM>.

The ping communication may be encrypted. As a non-limited example, the transmission from the central sever208 may comprise of an encryption key. The control unit <NUM> may send a response encryption key/message in accordance to the received encryption key. The central server <NUM> then receives the response message. In case the response message is in accordance to the transmitted encryption key, the central server <NUM> may determine that the communication fulfills the predetermined rule of communication. In response thereto, the central server <NUM> may inform the control unit <NUM> to set the thermal device <NUM> in a normal operation mode. The normal operation mode will be discussed in more detail below. In case the response message is not in accordance to the transmitted encryption key, the central sever <NUM> may determine that the communication does not fulfill the predetermined rule of communication. In response thereto, the central server <NUM> may issue an alarm. The issuance of the alarm will be discussed in more detail below. Using encrypted ping communication, the central server may not only check that the communication itself is ok, but also that no one has modified the control unit <NUM> in the thermal device <NUM>.

The communication unit <NUM> is configured to communicate with the plurality of control units <NUM> controlling the thermal device <NUM>. The communication path <NUM> over which the communication is made may be wired or wireless. The communication may include data transfers, and the like. Data transfers may include, but are not limited to, downloading and/or uploading data and receiving or sending messages. The data may be processed by the central server <NUM> and/or the control unit <NUM>. The processing may include storing the data in a memory, e.g. the memory <NUM> of the central server <NUM>, executing operations or function, and so forth. The communication may be individual for each control unit <NUM>. Especially, the communication unit <NUM> is configured to communicate with each of the plurality of control units <NUM> using a predetermined rule of communication. The predetermined rule of communication may be the same for each control unit <NUM>. Alternatively, the predetermined rule of communication may be different for the communication with at least some of the control units <NUM>. As mentioned above, the predetermined rule of communication may be a ping communication initiated by the central server <NUM>. Hence, the communication unit <NUM> of the control server <NUM> may be configured to initiate a ping communication with a control unit <NUM> controlling a thermal device <NUM>.

The control circuit <NUM> is configured to carry out overall control of functions and operations of the central server <NUM>. The control circuit <NUM> may include a processor <NUM>, such as a central processing unit (CPU), microcontroller, or microprocessor. The processor <NUM> is configured to execute program code stored in the memory <NUM>, in order to carry out functions and operations of the central server <NUM>.

The memory <NUM> may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or another suitable device. In a typical arrangement, the memory <NUM> may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the control circuit <NUM>. The memory <NUM> may exchange data with the control circuit <NUM> over a data bus. Accompanying control lines and an address bus between the memory <NUM> and the control circuit <NUM> also may be present.

Functions and operations of the central server <NUM> may be embodied in the form of executable logic routines (e.g., lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (e.g., the memory <NUM>) of the central server <NUM> and are executed by the control circuit <NUM> (e.g., using the processor <NUM>). Furthermore, the functions and operations of the central server <NUM> may be a stand-alone software application or form a part of a software application that carries out additional tasks related to the central server <NUM>. The described functions and operations may be considered a method that the corresponding device is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may as well be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

The control circuit <NUM> is configured to execute a monitoring function <NUM>. The monitoring function <NUM> is configured to monitor the communication between the central server <NUM> and a control unit <NUM>, i.e. it may be said that the monitoring function <NUM> is configured to monitor the communication between the central server <NUM> and a thermal device <NUM>. The monitoring function <NUM> may be configured to individually monitor the communications between the central server <NUM> and the plurality of control units <NUM>. Especially, the monitoring function <NUM> may be configured to monitor a communication between the central server <NUM> and a control unit <NUM> to check whether the communication is made using the predetermined rule of communication.

The control circuit <NUM> is further configured to execute a thermal device control function <NUM>. Upon the communication between the central server <NUM> and the control unit <NUM>, i.e. the thermal device <NUM>, fulfills the predetermined rule of communication, the thermal device control function <NUM> is configured to control the thermal device <NUM> such that it is set in a normal operation mode. This may e.g. be made by sending, using the communication unit <NUM>, a control message to the control unit <NUM>. The control message may comprise instructions for the control unit <NUM> to set the thermal device <NUM> in the normal operation mode. Additionally, the control message may comprise instructions to check if the thermal device <NUM> is already set in the normal mode and if not set the thermal device <NUM> in the normal operation mode. Upon the communication between the central server <NUM> and the control unit <NUM> does not fulfill the predetermined rule of communication, the thermal device control function <NUM> is configured to trigger an alarm. The alarm indicating a problem with the communication between the central server <NUM> and the control unit <NUM> controlling the thermal device <NUM>. The alarm may be sent to a client monitoring the distribution system <NUM>.

The central server <NUM> may comprise a database <NUM>. The control circuit <NUM> may further be configured to execute a register function <NUM>. The register function <NUM> is configured to, in the database <NUM>, indicate the controllability of the thermal device <NUM>. The register function <NUM> may further be configured to, in the database <NUM>, indicate the controllability of each of the plurality of thermal devices <NUM> of the distribution system <NUM>. Accordingly, the database <NUM> may comprise entries of the thermal devices <NUM> of the distribution system <NUM> and an indication for each thermal device <NUM> whether the central server <NUM> can initiate a communication with the control unit <NUM> controlling the respective thermal device <NUM>.

Hence, by analyzing the ability for the central server <NUM> to initiate a communication with a control unit <NUM>, the central server <NUM> may control the controllability of the control unit <NUM>, i.e. the controllability of the thermal device <NUM>. The analysis is based on if the communication between the central server <NUM> and the control unit <NUM> fulfills the predetermined rule of communication.

In connection with <FIG> a method <NUM> for checking controllability of a thermal device <NUM> connected to the distribution grid <NUM> will be discussed. The method <NUM> comprises the following steps. The steps of the method <NUM> may be performed in any order suitable.

Monitoring <NUM> a communication between the central server <NUM> and a control unit <NUM> controlling a thermal device <NUM>. Hence, it may be said that the monitoring <NUM> is made for a communication between the central server <NUM> and a thermal device <NUM>. Upon the communication between the central server <NUM> and the thermal device <NUM> fulfills <NUM> a predetermined rule of communication, setting <NUM> the thermal device <NUM> in a normal operation mode. In the normal operation mode, the thermal device <NUM> may be controllable by the central server <NUM>. Upon the communication between the central server <NUM> and the thermal device <NUM> does not fulfill <NUM> the predetermined rule of communication, triggering <NUM> an alarm. The alarm indicating a problem with the communication between the central server <NUM> and the thermal device <NUM>.

In connection with <FIG> a control unit <NUM> configured to control a thermal device <NUM> will be discussed in more detail. The control unit <NUM> comprises a communication unit <NUM>, a control circuit <NUM> and a memory <NUM>.

The communication unit <NUM> is configured to communicate with the central server <NUM>. The communication path <NUM> over which the communication is made may be wired or wireless. The communication may include data transfers, and the like. Data transfers may include, but are not limited to, downloading and/or uploading data and receiving or sending messages. The data may be processed by the control unit <NUM> and/or the central server <NUM>. The processing may include storing the data in a memory, e.g., the memory <NUM> of the control unit <NUM>, executing operations or function, and so forth.

The control circuit <NUM> is configured to carry out overall control of functions and operations of the control unit <NUM>. The control circuit may include a processor <NUM>, such as a central processing unit (CPU), microcontroller, or microprocessor. The processor <NUM> is configured to execute program code stored in the memory <NUM>, in order to carry out functions and operations of the control unit <NUM>.

Functions and operations of the control unit <NUM> may be embodied in the form of executable logic routines (e.g., lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (e.g., the memory <NUM>) of the control unit <NUM> and are executed by the control circuit <NUM> (e.g., using the processor <NUM>). Furthermore, the functions and operations of the control unit <NUM> may be a stand-alone software application or form a part of a software application that carries out additional tasks related to the control unit <NUM>. The described functions and operations may be considered a method that the corresponding device is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may as well be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

The control circuit <NUM> is configured to execute a monitoring function <NUM>. The monitoring function <NUM> is configured to monitor the communication between the control unit <NUM> and the central server <NUM>.

The control circuit <NUM> is further configured to execute a mode setting function <NUM>. The mode setting function <NUM> is configured to determine whether the communication between the control unit <NUM> and the central server <NUM> fulfills a predetermined rule of communication. The predetermined rule of communication was discussed above in connection with the discussion of the central server in <FIG> and will not be repeated here.

Upon the communication between the control unit <NUM> and the central server <NUM> fulfills the predetermined rule of communication, the mode setting function <NUM> is configured to set the thermal device <NUM> in a normal operation mode. Upon the thermal device <NUM> is set to operate in the normal operation mode, the thermal device <NUM> may be allowed to freely take out heat and/or cold from the distribution grid <NUM>. Upon the thermal device <NUM> is set to operate in the normal operation mode, the thermal device <NUM> may be controllable by the central server <NUM>.

Upon the communication between the control unit <NUM> and the central server <NUM> does not fulfill the predetermined rule of communication, the mode setting function <NUM> is configured to set the thermal device <NUM> in a limited operation mode. The limited operation mode is more restricted than the normal operation mode. Upon the thermal device <NUM> is set to operate in the limited operation mode, the thermal device <NUM> is restricted to take out heat and/or cold from the distribution grid <NUM> below a preconfigured threshold. The preconfigured threshold may be different for different thermal devices <NUM>. The preconfigured threshold may be set to zero. Hence, upon being set to operate in the limited operation mode, the thermal device <NUM> may be forbidden to take out heat and/or cold from the distribution grid <NUM>. In other examples, the preconfigured threshold may be set to a percentage of = max heat or cold outtake, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>% of max heat or cold outtake. In yet another example, the limited operation mode may be that the thermal device <NUM> is only allowed to out take one of heat or cold, possibly with an outtake below a preconfigured threshold (e.g. <NUM>%, <NUM>%, <NUM>%, <NUM>% of max heat or cold outtake.

Hence, by analyzing the communication between the control unit <NUM> and the central server <NUM>, the control unit <NUM> may be configured to set the thermal device <NUM> in a normal operation mode or in a limited operation mode. The limited operation mode is more restricted than the normal operation mode. In case the central server <NUM> may initiate a communication with the control unit <NUM>, the control unit <NUM> is allowed to set the thermal device <NUM>, it is controlling, in the normal operation mode. In case, for some reason, the central server <NUM> may not initiate a communication with the control unit <NUM>, the control unit <NUM> is configured to set the thermal device <NUM>, it is controlling, in the limited operation mode.

In connection with <FIG> a method <NUM> for controlling an outtake of heat and/or cold of a thermal device <NUM> from a distribution grid <NUM> will be discussed. The method <NUM> comprises the following steps. These steps of the method <NUM> may be performed in any order suitable. Monitoring <NUM> a communication between a control unit <NUM> controlling the thermal device <NUM> and a central server <NUM>. Upon the communication fulfills <NUM> a predetermined rule of communication, setting <NUM> the thermal device <NUM> in a normal operation mode. Upon the communication does not fulfill <NUM> the predetermined rule of communication, setting <NUM> the thermal device in a limited operation mode. The limited operation mode is more restricted than the normal operation mode. In the normal operation mode, the thermal device <NUM> may be allowed to freely take out heat and/or cold from the distribution grid <NUM>. In the limited operation mode, the thermal device <NUM> may be restricted to take out heat and/or cold from the distribution grid <NUM> below a preconfigured threshold. In the normal operation mode, the thermal device <NUM> may be controllable by the central server <NUM> via the control unit <NUM>.

For example, the central server <NUM> may be embodied as a single server device having all the functionality of the central server <NUM>. Alternatively, the central server <NUM> may be a distributed device having different functionality in different devices.

Further, setting the thermal device (<NUM>) in the limited operation mode may be made after a certain amount of time has passed since the communication between the control unit (<NUM>) and the central server (<NUM>) does not fulfill the predetermined rule of communication. Hence, a delay in setting the thermal device (<NUM>) in the limited operation mode may be used. The certain amount of time, i.e. the delay time, may be in the range of <NUM> minutes to <NUM> hours. During the delay time, the communication between the control unit (<NUM>) and the central server (<NUM>) may be check in order to avoid entering the limited operation mode upon the communication will again fulfill the predetermined rule of communication.

Claim 1:
A control unit (<NUM>) configured to control an outtake of heat and/or cold of a thermal device (<NUM>) from a distribution grid (<NUM>) for a fluid based distribution of heat and/or cold, the control unit (<NUM>) comprising:
a communication unit (<NUM>) configured to communicate with a central server (<NUM>) using a predetermined rule of communication;
the control unit being characterized in that it comprises:
a control circuit (<NUM>) configured to execute:
a monitoring function (<NUM>) configured to monitor the communication between the control unit (<NUM>) and the central server (<NUM>);
a mode setting function (<NUM>) configured to:
upon the communication between the control unit (<NUM>) and the central server (<NUM>) fulfills the predetermined rule of communication, set the thermal device (<NUM>) in a normal operation mode,
upon the communication between the control unit (<NUM>) and the central server (<NUM>) does not fulfill the predetermined rule of communication, set the thermal device (<NUM>) in a limited operation mode, wherein the limited operation mode is more restricted than the normal operation mode