Patent Description:
In the prior art, electrically powered heating devices coupled with thermal storage devices are known. A relevant example is an air-to-water heat pump coupled with a domestic hot water (DHW) storage tank. The heat pump typically has a local controller system that provides autonomous control of the heat pump to heat the DHW tank. Typically, a thermostat type of control is used to maintain the DHW tank near a desired setpoint temperature value which is stored in the settings of the local controller, with feedback provided by a temperature sensor located in the tank. Additionally, the local control panel may include the ability to operate the heat pump based on signals received from an external source. This could be via a number of established communication protocols such as digitial I/O, Modbus, or Bacnet.

Increasingly many heat pumps and "smart" heating appliances have the ability to communicate with other devices and systems over the internet via a wireless home energy network. Mitsubishi Electric MELCloud™ is one example of an internet cloud-based control and monitoring system for heat pumps based on this principle. Presently, cloud-based control and monitoring systems for heat pumps and electric heating devices are used primarily for remote monitoring and control at the single-user level or to assist remote maintenance and technical support. Increasingly the potential is being considered for such communication technologies to enable coordinated control of multiple devices for demand-response (DR) or demand-side management (DSM). Multiple objectives for DR or DSM can be considered, such as CO<NUM>-emissions reduction through maximising utilisation of renewable energy sources ("renewables") or other grid-level services such as frequency response.

Recent legislation such as the EU Energy Performance in Buildings Directive (EPBD) encourages renewable energy for buildings to be from "local" sources (on site or close to site). Consuming locally generated energy when available and minimising grid interaction over large geographical distances is preferable for minimising the stress placed on the grid infrastructure and the logistical complexity encountered by the national/regional grid operator. This is also of particular relevance for off-shore island communities with a limited capacity connection to the mainland electricity grid via a sub-marine interconnector cable.

<CIT> discloses systems and methods of providing power as it is generated at a consumer's premises.

<CIT> discloses an energy analysis system which assists with obtaining a detailed view of how energy consumption occurs in a building, what steps may be taken to lower the energy footprint, and executing detailed energy consumption analyses.

<CIT> discloses a home energy management system and method which includes a database configured to store site report data received from a plurality of residential sites using a wireless home energy network at each site.

<CIT> discloses a method of determining a level of potential responsive-load electrical power network service susceptible to being provided by one or more power consuming devices.

<CIT> discloses an apparatus for controlling the storage of energy in an electrically-heated thermal energy storage unit.

<CIT> discloses that, when there is a hot water amount-deficient water heater whose remaining amount of hot water is less than a predetermined amount between heat pump water heaters which are not in boiling operation, an operation control part performs a boiling stop control to stop at least one of heat pump water heaters in boiling operation from performing the boiling operation, and also performs a boiling start control to let the hot water amount-deficient water heater start performing boiling operation.

<CIT> discloses a power management system which is connected to a system power supply, and which, with respect to a storage battery in a first customer facility having a storage battery and a power generator as electrical equipment, controls discharge thereof to the first customer facility or charge thereof with surplus power generated in the first customer facility.

<CIT> discloses systems and methods that improve grid performance by smoothing demand using thermal reserves, wherein the smoothed demand can reduce peak loads as well as the ramp rate of demand that will otherwise require the use of inefficient, expensive generation sources. The improvements are tied to the selective switching on or off electrical loads that are coupled to thermal reserves, effectively using the thermal reserves as an energy storage mechanism.

Prior art systems and methods for controlling a demand response of a plurality of electrical heating devices suffer the disadvantage that they are complicated and do not use simple control actions that can be implemented by a local thermostatic controller which is local to each electrical heating device. Moreover, known systems and methods do not have the possibility to control the electrical heating devices to maximally utilize renewable energy sources ("renewables") within an offer between renewable and non-renewable energy sources. Furthermore, prior art systems and methods do not rely on a control which considers that a dynamic response of the energy supply system (import and export of energy) may vary depending on the number and characteristics of the heating devices and thermal storage devices which are connected to the energy supply system. For example, prior art systems and methods do not rely on a control which is capable of shifting peak loads with respect to time.

Starting therefrom, it was the object of the present invention to provide a system for controlling a demand response of a plurality of electrical heating devices which does not suffer the drawbacks of prior art systems and methods. Specifically, the system should be more ecological by keeping the carbon footprint as small as possible (i.e. reduce the "carbon intensity"). Furthermore, the system should be more economical by reducing costs connected to electricity which is imported from distant electricity sources. Moreover, for avoiding temporary and strong burdens on a electrical-energy exchange means (i.e. temporary and strong demands of electricity from said means), the system should also be capable of providing a more steady and predictable energy exchange between a local microgrid and the electrical-energy exchange means.

The objective is solved by the system having the features of claim <NUM> and the use having the features of claim <NUM>. The dependent claims illustrate advantageous embodiments of the invention.

According to the invention, a system for controlling a demand response of a plurality of electrical heating devices is provided, comprising.

The advantage of the inventive system is that, at a specific point in time, the control of the systems allows the amount of active local electrical heating devices to be adjusted to the degree of import and export, i.e. to the ratio between import and export. Thus, the control of the system can ensure that a heating demand at a specific point in time can be met while minimizing an amount of import of electrical energy from a non-renewable-electrical-energy source. This allows the system to keep the carbon footprint as small as possible and to operate more ecologically.

The cloud-based supervisory control (CSC) system can be configured to operate in either the RSC operation mode or the PLS operation mode based on the CSC system operator preference. The choice of the CSC system operating mode thus depends on the preference of the system operator. In the renewables self-consumption (RSC) operation mode, a current local consumption of renewables is maximized, i.e. the use of electrical energy from the RES generator of the system is maximized. For the type of island applications to which this can be targeted, high rates of export at undesirable times can be problematic for the grid operator. Maximising local self-consumption of renewables to charge storage at times of low demand have the secondary benefit of reducing peak demand and associated peak import requirement. In the peak-load shifting (PLS) operation mode, peak-loads known to occur at a specific point in time are shifted to a different point in time at which peak-loads are known to not occur, i.e. this operation mode prevents an occurrence of (temporary) strong burdens on the electrical-energy exchange means connected to the system. Hence, said operation mode of the system reduces the risk of an occurrence of a power failure (blackout) of the electrical-energy exchange means (e.g. of a regional-scale or national-scale macrogrid or of a diesel-based generator) connected to the system.

The cloud-based supervisory control (CSC) system can be characterized in that it is configured to exchange information with each local thermostatic controller (LTC) and/or with the local renewable energy system (RES) generator by means of a suitable Internet of things (IoT) gateway located locally to each device.

The system can be characterized in that, after a start of either the renewables self-consumption (RSC) operation mode or the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to compare an amount of time that has elapsed since a previous control action, to a predetermined control interval. If the amount of time that has elapsed is less than the predetermined control interval, the total number of local electrical heating devices (EHDs) considered in the operation mode is not reviewed or not modified. If the amount of time that has elapsed is equal to or larger than the predetermined control interval, the total number of local electrical heating devices (EHDs) considered in the operation mode is reviewed and is modified, wherein preferably the total number of local electrical heating devices (EHDs) considered in the operation mode is increased, is decreased, or is maintained the same.

Moreover, the system can be characterized in that, in the renewables self-consumption (RSC) operation mode and/or in the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to exchange at least the following information with each local thermostatic controller (LTC):.

The cloud-based supervisory control (CSC) system is configured to receive information about a degree of import and export of electricity between the electrical-energy exchange means and the local, decentralized electricity microgrid. To this end, the cloud-based supervisory control (CSC) system can be configured to monitor a net instantaneous import or export of electricity from the local microgrid to the electrical-energy exchange means (e.g. to a wider area macrogrid). In this regard, the system can be characterized in that, in the renewables self-consumption (RSC) operation mode and/or in the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to receive information from at least one, preferably several, metering device(s) which is/are located on the microgrid and which is/are suitable for measuring the quantity of electricity which is exported from the electricity microgrid to the electrical-energy exchange means and which is imported from the electrical-energy exchange means to the electricity microgrid. The presence of the at least one metering device facilitates the cloud-based supervisory control (CSC) system to implement its configuration to make, among all of the plurality of local electrical heating devices (EHDs), active a specific amount of local electrical heating devices (EHDs) depending on a received information about the degree of import and export of electricity between the electrical-energy exchange means and the decentralized electricity microgrid for a specific point in time. In absence of information received from the cloud-based supervisory control (CSC) system, a local thermostatic controller (LTC) provides autonomous control of the local electrical heating device (EHD) based on the current settings stored in the local thermostatic controller (LTC).

Besides, the system can be characterized in that, in the renewables self-consumption (RSC) operation mode, the cloud-based supervisory control (CSC) system is configured to calculate a present average consumption (PEHD,avg) of all of the local electrical heating devices (EHDs) having sent a demand signal by dividing a present total consumption of all said devices (EHDs) by the number of said devices (EHDs) that are presently active, wherein the average consumption is used to predict how many of said devices (EHDs) should be activated or deactivated in order to balance import and export of electricity between the electrical-energy exchange means and the decentralized electricity microgrid, wherein said balancing is preferably performed as follows:.

Preferably, if the difference between a new value of the number of devices (EHDs) requested for demand operation (Nreq) and a current number of devices (EHDs) currently active (Nactive) is larger than a maximum value (Nstep,max) representing the maximum amount of local electrical heating devices (EHDs) that can be activated in a single control interval, a new value of the number of devices (EHDs) requested for demand operation (Nreq) is set equal to the sum of the current number of devices (EHDs) currently active (Nactive) and the maximum value (Nstep,max) representing the maximum amount of devices (EHDs) that can be activated in a single control interval, wherein, especially, if the new value of the number of devices (EHDs) requested for demand operation (Nreq) has been increased relative to a previous time interval, the timer is reset to zero.

Moreover, the system can be characterized in that, in the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to calculate a target electricity demand value (Pset) from the average of the total electrical power demand for the entire microgrid (Pdem) over the previous n measurement intervals in a certain period of time, wherein n is an integer, wherein, based on a current time of day (ToD) and the target electricity demand value (Pset).

Preferably, if the difference between a new value of the number of devices (EHDs) requested for demand response (Nreq) and a current number of devices (EHDs) currently active (Nactive) is larger than a maximum value (Nstep,max) representing the maximum amount of local electrical heating devices (EHDs) that can be activated in a single control interval, a new value of the number of devices (EHDs) requested for demand response (Nreq) is set equal to the sum of the current number of devices (EHDs) currently active (Nactive) and the maximum value (Nstep,max) representing the maximum amount of devices (EHDs) that can be activated in a single control interval, wherein, especially, if the new value of the number of devices (EHDs) requested for demand response (Nreq) has been increased relative to a previous time interval, the timer is reset to zero.

Furthermore, the system can be characterized in that, in the renewables self-consumption (RSC) operation mode and/or in the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to assess local electrical heating devices (EHDs) for eligibility criteria and to rank the local electrical heating devices (EHDs) based on their eligibility, wherein a lower ranking index number indicates a higher ranking priority, optionally an index of <NUM> indicates a highest ranking.

The eligibility criteria of the local electrical heating devices (EHDs) are preferably determined by.

Preferably, a local electrical heating device (EHD) is eligible if its current status is active and the current temperature of its local thermal energy store (TES) is below a heating setpoint temperature (Tsp,dr), or is eligible if its current status is inactive and the current temperature of its local thermal energy store (TES) is below a heating setpoint temperature (Tsp,dr) minus a value (ΔTdrop,min) by which the temperature of the local thermal energy store (TES) is allowed to drop after a previous operation mode.

What is more, the system can be characterized in that, in the renewables self-consumption (RSC) operation mode and/or in the peak-load shifting (PLS) operation mode, the cloud-based supervisory control (CSC) system is configured to assess local electrical heating devices (EHDs) individually according to their ranking index, such that the controller is configured to submit to.

Besides, the system can be characterized in that each local thermostatic controller (LTC) is configured to control an operation mode of the local electrical heating devices (EHD) to which it is connected based on at least the following information:.

In addition, the system can be characterized in that each local thermostatic controller (LTC) is configured to receive at least the following control parameters from the cloud-based supervisory control system (CSC):.

Beyond that, the system can be characterized in that each local thermostatic controller (LTC) is configured to send information about a current status of the local electrical heating device (EHD) to which it is connected and a current status of the local thermal energy store (TES) to which it is connected to the cloud-based supervisory control (CSC) system at regular intervals. The current status is preferably.

Besides that, the system may be characterized in that the cloud-based supervisory control (CSC) system comprises at least one of, preferably all, of the following functions and/or parameters:.

Moreover, the System can be characterized in that the electrical-energy exchange means comprises or consists of.

Furthermore, the system can be characterized in that each one of the plurality of local electrical heating devices (EHDs) is a device capable of converting electricity into storable heat, wherein the device capable of converting electricity into storable heat is preferably selected from the group consisting of electric immersion heater, vapour-compression heat pump, thermoelectric devices and combinations thereof.

In addition, the system can be characterized in that each one of the local thermal energy store (TESs) is a vessel containing a medium capable of storing heat within a desired temperature range, wherein the vessel is preferably selected from the group consisting of domestic hot water cylinder, heat transfer fluid buffer vessel, phase change material (PCM) store, packed bed storage vessel and combinations thereof.

According to the invention, a use of the system according to the invention for controlling a demand response of a plurality of electrical heating devices is proposed.

Based on the specific embodiments shown in the following figures and examples, the subject-matter of the invention shall be presented in more detail without wishing to restrict the invention to said specific subject-matter.

A specific example of a system according to the invention is shown in <FIG>, in which the electrical-energy exchange means comprises or consists a wide-area macrogrid.

In <FIG>, a network of EHDs located in a cluster of residential buildings or dwellings is shown. Each building contains an EHD for domestic hot water provision that is coupled to a thermal store (e.g. a domestic hot water tank) with a local thermostatic controller (LTC).

The cluster of buildings is connected to a decentralised electricity microgrid served by local renewable energy system (RES) generators. The microgrid also has a limited capacity connection to a electrical-energy exchange means, which in this case is a wide-area (regional or national scale) macrogrid, with which electricity can be exchanged (imported or exported). The objective for the CSC is to maximise the autonomy of the microgrid by operating the EHDs in a flexible manner to minimise import and export of electricity to or from the wider area macrogrid. This can be achieved by the configuration of the CSC to make, among all of the plurality of EHDs, active a specific amount of EHDs depending on a received information about the degree of import and export of electricity between the wide-area macrogrid and the decentralized electricity microgrid for a specific point in time.

The CSC system is able to exchange information with each LTC and each RES generator by means of a suitable Internet of things (loT) gateway located locally to each device. The CSC system is also able to the monitor net instantaneous import or export of electricity from the microgrid to the wider area macrogrid. In absence of information received from the CSC system, the LTC provides autonomous control of the EHD based on the current settings stored in the LTC.

The LTC controls the operation of the EHD based on the following information:.

This signal can be provided locally by the building user manually pressing a button on the LTC, or remotely from a command sent by the CSC system.

The operation of the LTC assumed here is based on the operation of a typical thermostatic controller for a heat pump or electric immersion heater and is described as follows:.

Each LTC sends information at regular intervals to the CSC system about the current status of the respective EHD and TES:.

Each LTC also receives the following control actions from the CSC system in demand response operation:.

The CSC system control algorithm can use the following parameters:.

In a further specific example of a system according to the invention, the electrical-energy exchange means consists of a diesel-based generator. In this case, the wide-area macrogrid of <FIG> is replaced by a diesel-based generator. This system can describe a microgrid operating in "island mode", where there is no connection to a wider area macrogrid. In such instance, there is no import or export of electricity to or from a wider area grid, but only an import of electricity from a diesel-based generator. Thus, any deficit in local RES generation is met by the diesel-based generator. Any surplus of local RES generation is curtailed through conventional means.

In such an application the RSC and PLS variants of the control method may still be applied, with the objectives modified as follows:.

In the renewables self-consumption (RSC) operation mode, an objective is to achieve maximum self-consumption from local RES generators supplying the microgrid (minimum import/export from the wider area grid), i.e. to minimise imported electricity at a specific point in time.

A control method implemented by the CSC system in the renewables self-consumption (RSC) operation mode is described below and illustrated in <FIG>:.

In the peak-load shifting (PLS) operation mode, an objective is not only to minimise imported electricity at a specific point in time to run the system more economically and ecologically, but also to minimise peaks in electricity demand by charging the TES during periods of low demand, i.e. to modulate total electricity demand to match a set value to prevent demand spikes and a possible occurrence of a power failure (blackout) in the electrical-energy exchange means (e.g. of a regional-scale or national-scale macrogrid) which is connected to the system. In short, an advantage of this operation mode is that a more stable total electricity demand (e.g. over the diurnal period) and a reduction in the peak requirement for import of electricity from a wider area macrogrid is provided.

The operating principle is to minimise electricity demand during pre-defined "peak" hours by pre-charging the TES devices prior to these peak hours. This assumes that the EHDs constitute a significant proportion of consumption during the peak hours that can be shifted to periods of lower demand by pre-charging the TES.

Claim 1:
System for controlling a demand response of a plurality of electrical heating devices, comprising
a plurality of local electrical heating devices, EHDs, a plurality of local thermostatic controllers, LTCs, and a plurality of local energy stores TESs, wherein each electric heating device, EHD, is connected to and controlled by a respective local thermostatic controller, LTC, and is connected to and thermally coupled to an associated local thermal energy store, TES, wherein each local thermal energy store, TES, comprises a temperature sensor for detecting the temperature of the local thermal energy store, TES; a local renewable energy system, RES, generator which provides electricity to each of the plurality of local electrical heating devices, EHDs, via a decentralized electricity microgrid, wherein the decentralized electricity microgrid is electrically connected to an electrical-energy exchange means which is different to the local renewable energy system, RES, generator;
a cloud-based supervisory control, CSC, system which is configured to receive information about a degree of import and export of electricity between the electrical-energy exchange means and the local, decentralized electricity microgrid;
wherein the cloud-based supervisory control, CSC, system is configured to control each local thermostatic controller, LTC, by receiving and sending information to each local thermostatic controller, LTC,
characterized in that the cloud-based supervisory control, CSC, system is configured to activate, among all of the plurality of local electrical heating devices, EHDs, a specific amount of local electrical heating devices, EHDs, depending on a received information about the degree of import and export of electricity between the electrical-energy exchange means and the local, decentralized electricity microgrid at a specific point in time, and
perform an operation mode selected from a group consisting of a renewables self-consumption, RSC, operation mode and a peak-load shifting, PLS, operation mode.