Method and Controller to Operate a Hot Water Storage Device Heater and Hot Water Storage Device

The present disclosure relates to a method to operate a hot water storage device. Further, the present disclosure relates to a controller to operate a hot water storage device and to a hot water storage device.

Hot water storage devices known from prior art comprise a tank configured to store water, wherein the tank has a bottom wall, a top wall and a side wall extending between the bottom wall and the top wall. Hot water storage devices known from prior art further comprise a heating unit positioned at a first distance from the bottom wall, wherein the heating unit is configured to heat the water stored within the tank, namely in such a manner that water heated by the heating unit rises up within the tank such that the heated water is stratified above unheated water within the tank. Hot water storage devices known from prior art further comprise a temperature sensor positioned at a distance from the bottom wall, the temperature sensor being configured to measure a water temperature of the heated water. Hot water storage devices known from prior art further comprise a controller being configured to control the heating unit and thereby the water temperature of the heated water stored within the tank. Heating of the water within the tank may be initiated when the temperature of the water within the tank falls under a respective threshold.

GB 2 518 365 A, US 2009/0 188 486 A1, U.S. Pat. Nos. 11,060,763 B2, 10,295,199 B2 and 7,971,796 B2 disclose hot water storage devices.

Controllers of a hot water storage devices known form prior art keep permanently a defined water volume within the tank of the hot water storage device at a defined hot water temperature, either 24 hours per day and 7 days per week or according to a daily ON/OFF schedule of the hot water storage device when the hot water storage device is in the ON status. Keeping the defined water volume within the tank of the hot water storage device permanently at a defined hot water temperature is energy inefficient and creates carbon emissions when no actual hot water demand is present.

Against this background a novel method to operate a hot water storage device as defined in claimand a novel controller of a hot water storage device as defined in claimas well as a novel hot water storage device as defined in claimare provided that allow an energy efficient operation of a hot water storage device with lower carbon emissions.

The method according to claimdetermines from a water temperature measurement signal provided by the at least one temperature sensor a water usage profile, said water usage profile providing for defined time intervals of a day and/or for defined days of a week a nominal temperature and a nominal volume of the heated water to be stored within the tank.

The method according to claimoperates the heating unit in such a manner that for each defined time interval of a day and/or for each defined day of a week the actual temperature and the actual volume of the heated water stored withing the tank corresponds automatically to the respective nominal value of the water usage profile.

According to a first alternative, the at least one water temperature measurement signal provided by the at least one temperature sensor is provided to a database like a cloud-database, wherein the database determines the water usage profile providing for each respective time interval of a respective day of a week the nominal temperature and the nominal volume of the heated water to be stored within the tank, and wherein the controller operates the heating unit of basis of said water usage profile provided by the database to the controller. In the first alternative, the functionality of the method is split up between the database and the controller.

According to a second alternative, the at least one water temperature measurement signal provided by the at least one temperature sensor is provided to the controller, wherein the controller determines the water usage profile providing for each respective time interval of a respective day of a week the nominal temperature and the nominal volume of the heated water to be stored within the tank, and wherein the controller operates the heating unit of basis of said water usage profile. In the second alternative, the functionality of the method is provided by the controller only.

The controller of the hot water storage device according to claimis configured to determine from a water temperature measurement signal provided by the at least one temperature sensor of the hot water storage device a water usage profile, said water usage profile providing for defined time intervals of a day and/or for defined days of a week a nominal temperature and a nominal volume of the heated water to be stored within the tank.

The controller of the hot water storage device according to claimis configured to operate the heating unit of the hot water storage device in such a manner that for each defined time interval of a day and/or for each de-fined day of a week the actual temperature and the actual volume of the heated water stored withing the tank of the hot water storage device corresponds automatically to the respective nominal value of the water usage profile.

The method as well as the controller of the hot water storage device according to the present disclosure allow an energy efficient operation of a hot water storage device with lower carbon emissions. The water usage profile is determined from the water temperature measurement signal provided by the at least one temperature sensor. Said water usage profile provides for each respective time interval of a day and for each respective day of a week the nominal temperature and the nominal volume of the heated water to be stored within the tank. So, the water usage profile does not only provide a nominal value for the water temperature but also a nominal value for the volume of the heated water to be stored within the tank.

Preferably, the water usage profile is determined from a first water temperature measurement signal provided by a first temperature sensor positioned at a second distance from the bottom wall of the tank and from a second water temperature measurement signal provided by the second temperature sensor positioned at a third distance from the bottom wall of the tank and/or from an average water temperature signal of the first water temperature measurement signal and the second water temperature measurement signal, wherein said second distance is greater than said first distance and said third distance is greater than said second distance. This allows an even more precise control of the temperature and of the volume of the heated water within the tank to provide an energy efficient operation of a hot water storage device with lower carbon emissions.

Preferably, the water usage profile is determined as a function of a change rate of the at least one water temperature measurement signal in the respective time interval of the respective day and/or as a function of a frequency and as a function of an amount of a hot water demand in the respective time interval of the respective day. This allows to determine the water usage profile in a reliable and simple manner.

Preferably, the water usage profile is determined in such a manner that for each respective time interval of each respective day of a week a nominal value pair comprising the nominal temperature and the nominal volume of the heated water to be stored within the tank is determined, namely a nominal value pair N of a set of nominal value pairs comprising at least the following nominal value pairs: pair 1: first nominal volume and first nominal temperature, pair 2: first nominal volume and second nominal temperature, pair 3: second nominal volume and first nominal temperature, pair 4: second nominal volume and second nominal temperature, wherein the second nominal volume is greater than the first nominal volume, and wherein the second nominal temperature is greater than the first nominal temperature. The set of nominal value pairs on basis of which the water usage profile for each respective time interval of each respective day of a week is determined may comprise the following additional nominal value pair: pair 5: third volume and second nominal temperature, wherein the third nominal volume is greater than the second nominal volume. The set of nominal value pairs on basis of which the water usage profile for each respective time interval of each respective day of a week is determined may comprise the following additional nominal value pair: pair 0: fourth volume and fourth nominal temperature, wherein the fourth nominal volume is smaller than the first nominal volume and the fourth nominal temperature is smaller than the first nominal temperature. Pair 0 may correspond to on OFF status or STANDBY status of the hot water storage device. Pairs 1 to 5 all belong to an ON status of the hot water storage device. With pairs 1 to 4 a respective volume of heated water is stratified above unheated water within the tank. With pair 5 the tank may become de-stratified such that the full volume of the tank is filled with heated water. This allows an simple and reliable, energy efficient operation of a hot water storage device with lower carbon emissions using a limited number of nominal value pairs defining the nominal temperature and the nominal volume of the heated water to be stored within the tank.

Preferably, for each respective time interval of each respective day a confidence factor associated with the nominal temperature and the nominal volume of the heated water to be stored within the tank is determined, wherein the confidence factor depends on the frequency and from the amount of a hot water demand in the respective time interval of the respective day. Based on the confidence factor the nominal value pair used for the operation of the hot water storage device may be changed.

Preferably, the confidence factor of a respective time interval is increased if the frequency of hot water demands and/or the amount of a hot water demand in the respective time interval is above a respective upper threshold within the respective time interval of the respective day. The confidence factor of a respective time interval is decreased if the frequency of hot water demands and/or the amount of a hot water demand in the respective time interval is below a respective lower threshold within the respective time interval of the respective day. The confidence factor of a respective time interval remains unchanged if the frequency of hot water demands and/or the amount of a hot water demand in the respective time interval is above a respective lower threshold and below the respective upper threshold. A change of the confidence factor of a respective time interval of a respective day may affect the confidence factor of time intervals adjoining the respective time interval in which the confidence factor has changed. Such a confidence factor allows an simple and reliable change of the nominal value pair used in a respective time interval to control temperature and volume of heated water stored within the tank of the hot water storage device and to provide an energy efficient operation of a hot water storage device with lower carbon emissions.

Preferably at an initial state or at an initialization state of the hot water storage device, the water usage profile of each time interval of each day is initialized with the pair N (N=2 or 3 or 4) of the nominal value pairs, preferably with pair 4. If the confidence factor of the respective time interval of the respective day is below a lower limit, then the water usage profile of the respective time is changed to pair N−1 of the nominal value pairs. If the confidence factor of the respective time interval of the respective day is above an upper limit, then the water usage profile of the respective time interval is changed to pair N+1 of the nominal value pairs. If the confidence factor of the respective time interval of the respective day is above the lower limit and below the upper limit, then the water usage profile of the respective time interval remains at pair N of the nominal value pairs. This allows an simple and reliable change of the nominal value pair used in a respective time interval to control temperature and volume of the heated water within the tank to provide an energy efficient operation of a hot water storage device with lower carbon emissions.

Further on, a hot water storage device as defined in the claimhaving such a controller is provided.

shows a hot water storage device. The water hot storage devicecomprises a tankconfigured to store water. The tankof the hot water storage devicehas a bottom wall, a top walland a side wallextending between the bottom walland the top wall.

The hot water storage devicefurther comprises a heating unitpositioned at a first distance from the bottom wallof the tank. The heating unitis configured to heat the water stored within the tankin such a manner that water heated by the heating unitrises up within the tanksuch that the heated water is stratified above unheated water within the tank.

shows a pipethrough which heated water can be taken out of the tankin order to provide the heated water to a hot water consumer. The pipeis connected to the top wallor to the side walladjacent to the top wall.further shows a pipethrough which unheated water can be provided to the tankin order to replace the volume of water which has been taken out of the tankthrough the pipe. The pipeis connected to the bottom wallor to the side walladjacent to the bottom wall.

The hot water storage devicefurther comprises at least one temperature sensor,positioned at a distance from the bottom wall, wherein the at least one temperature sensor,is configured to measure a water temperature of the heated water stored within the tank.

In the preferred embodiment shown in, the hot water storage devicecomprises a first temperature sensorpositioned at a second distance from the bottom wallof the tank, said second distance being greater that said first distance, and a second temperature sensorpositioned at a third distance from the bottom wallof the tank, said third distance being greater that said second distance. Both temperature sensors,are assigned to the side wallof the tank. Both temperature sensors,are configured to measure a water temperature of the heated water stored within the tank.

The hot water storage devicefurther comprises a controller. The controlleris configured to control the heating unitand thereby the water temperature of the water stored within the tank.

The controllerprovides a control signal to the heating unitin order to control the operation of the heating unitof the hot water storage device.

The controlleris configured to receive a respective water temperature measurement signal from the respective temperature sensor,.

further shows an optional recirculation pipeextending between the pipeand the tank. A pumpis assigned to the recirculation pipe. The pumpand recirculation pipemay be used to recirculate the heated water taken out of the tankthrough the tank. The recirculation pipeis connected to the bottom wallor to the side walladjacent to the bottom wall. With the pumpthe water within the tankmay be de-stratified.

Controllers of a hot water storage device known form prior art keep permanently a defined water volume within the tank of the hot water storage device at a defined hot water temperature, either 24 hours per day and 7 days per week or according to a daily ON/OFF schedule of the hot water storage device when the same is in the ON status. Keeping the defined water volume within the tank of the hot water storage device permanently at a defined hot water temperature is energy inefficient and creates carbon emissions when no actual hot water demand is present.

According to the present disclosure, the controllerof the hot water storage deviceis configured to determine from a water temperature measurement signal provided by at least one temperature sensor,a water usage profile, said water usage profile providing for defined time intervals of a day and/or for defined days of a week a nominal temperature and a nominal volume of the heated water to be stored within the tankof the hot water storage device.

Preferably, the controlleris configured to determine from a first water temperature measurement signal provided by the first temperature sensorand from a second water temperature measurement signal provided by the second temperature sensorand/or from an average water temperature signal of the first water temperature measurement signal and the second water temperature measurement signal the water usage profile providing for defined time intervals of a day and/or for defined days of a week the nominal temperature and the nominal volume of the heated water to be stored within the tankof the hot water storage device.

The controlleraccording to the present disclosure is configured to operate the heating unitof the hot water storage devicein such a manner that for each defined time interval of a day and/or for each defined day of a week the actual temperature and the actual volume of the heated water stored withing the tankof the hot water storage devicecorresponds automatically to the respective nominal value of the water usage profile.

The controllerof the hot water storage deviceaccording to the present disclosure allows an energy efficient operation of a water storage device with lower carbon emissions.

If the controlleris configured to determine the water usage profile, the functionality of the present disclosure is provided by the controlleronly. In this case the at least one water temperature measurement signal provided by the at least one temperature sensor,is provided to the controller, wherein the controllerdetermines the water usage profile providing for each respective defined time interval of a respective day of a week the nominal temperature and the nominal volume of the heated water to be stored within the tank, and wherein the controlleroperates the heating unitof basis of said water usage profile.

Alternatively, the functionality of the present disclosure may be split up between the controllerand a databaselike a cloud database. In this alternative, the at least one water temperature measurement signal provided by the at least one temperature sensor,is provided to the databasepreferably through the controller, wherein the databasedetermines the water usage profile providing for each respective defined time interval of a respective day of a week the nominal temperature and the nominal volume of the heated water to be stored within the tank, and wherein the controlleroperates the heating unitof basis of said water usage profile provided by the databaseto the controller.

shows the tankin different conditions, The conditions can be provided with the method and controllerof the present disclosure.

In condition I of, the tankstores a first volume Vof heated water being stratified above unheated water within the tank. In condition I of, the volume Vhas a size that the first, lower temperature sensormeasures the temperature of the unheated water and the second, upper temperature sensormeasures the temperature of the heated water. The second, upper temperature sensormeasures the temperature of the heated water of volume Vin a lower section of volume V, preferably adjacent to or abutting a lower boundary surface of volume V. In condition I of, the heated water being present at the first volume Vmay have a first, relative low temperature Tof example given 45° C. or a second, relative high temperature Tof example given 60° C.

In condition II of, the tankstores a second volume Vof heated water being stratified above unheated water within the tank. The second volume is greater than the first volume. In condition II of, the volume Vhas a size that the first, lower temperature sensorand the second, upper temperature sensorboth measure the temperature of the heated water. The first, lower temperature sensormeasures the temperature of the heated water of volume Vin a lower section of volume V, preferably adjacent to or abutting a lower boundary surface of volume V. In condition II of, the heated water being present at the first volume Vmay have the first, relative low temperature Tof example given 45° C. or the second, relative high temperature Tof example given 60° C.

In both conditions I and II of, the heated water of the respective volume V, Vis stratified above unheated water within the tank.

In condition III of, the tankstores a third volume Vof heated water occupying the entire volume of the tank. In condition III of, no unheated water is present within the tankand the tankis de-stratified. In condition III of, the first, lower temperature sensorand the second, upper temperature sensorboth measure the temperature of the heated water. In condition III of, the heated water being present at the first volume Vhas the second, relative high temperature Tof example given 60° C.

Depending on the above combination of the volumes V, V, Vof the heated water within the tankand the temperatures T, Tthe tankmay have different conditions in case the hot water storage deviceis in an ON status. A sixth condition may be the OFF status of hot water storage device.

The controllerof the hot water storage devicemay be configured to determine the water usage profile as a function of the change rate of the at least one water temperature measurement signal in the respective time interval of the respective day. The controllermay further be configured to determine the water usage profile as a function of a frequency and as a function of an amount of a hot water demand in the respective time intervals of the respective day.

The controllerof the hot water storage devicemay be configured to determine the water usage profile in such a manner that for each respective time interval of each respective day of a week a nominal value pair comprising the nominal temperature and the nominal volume of the heated water to be stored within the tankis determined, namely a nominal value pair of a set of nominal value pairs comprising at least:

The second nominal volume of the heated water to be stored in the tankis greater than the first nominal volume of the heated water to be stored in the tank. The second nominal temperature of the heated water to be stored in the tankis greater than the first nominal temperature of the heated water to be stored in the tank.

Pairs 1 and 2 may be used to provide condition I of, namely pair 1 a first volume Vof heated water having the first temperature Tand pair 2 a first volume Vof heated water having the second temperature T.

Pairs 3 and 4 may be used to provide condition II of, namely pair 3 a second volume Vof heated water having the first temperature Tand pair 4 a second volume Vof heated water having the second temperature T.

The nominal value pairs on basis of which the water usage profile for each respective time interval of each respective day of a week is determined may comprise the following additional nominal value pair:

The third nominal volume is greater than the second nominal volume.

Pair 5 may be used to provide condition III of, namely a third volume Vof heated water having the second temperature T.

The second nominal volume and thereby the second volume Vis greater than the first nominal volume and thereby the first volume V. A ratio R2/1 between the second nominal volume and thereby the second volume Vand the first nominal volume and thereby the first volume Vmay be from 2:1 to 4:1, preferably from 2.5:1 to 3.5:1. The third nominal volume and thereby the third volume Vis greater than the first and second nominal volume and thereby the first volume Vand second volume V. A ratio R3/1 between the third nominal volume and thereby the third volume Vand the first nominal volume and thereby the first volume Vmay be from 3:1 to 5:1, preferably from 3.5:1 to 4.5:1. In any case the ratio R3/1 is greater than the ratio R2/1. In an embodiment the ratio R2/1 may be 3:1 and the ratio R3/1 may be 4:1. These ratios are of exemplary nature.