The object of this invention is a new method for the management of water maintenance temperature in a generic storage water heater controllable by electronic control.
It is known that in storage water heaters, the main cause of inefficiency is due to the thermal dispersions that can be even very high, due to the fact that water is brought to the preset temperature required even with great advance over the actual time of use.
It is equally known that if the storage water heater is kept exactly at the useful temperature T.u for hygienic use, it is capable of dispensing at such temperature an amount of water equal to a significant fraction of the tank volume but not equal to the volume itself, due to the so-called mixing phenomenon (the incoming cold water mixes with a part of the hot water in the tank, thus decreasing the temperature thereof below the useful temperature T.u). If the preset temperature T.set at which the storage water heater is kept is much higher than said useful temperature T.u, moreover, it is capable of ensuring, through mixing with cold water, amounts of water at useful temperature T.u much larger than the storage volume.
In the practice, it is difficult for the user to determine which the optimum value of the preset temperature T.set required for ensuring the service should be, also considering that it may be highly variable according to the days of the week; as a consequence, even where the preset temperature T.set is adjustable by the user, it is often kept at much higher values than those actually required day by day.
The document
Said document discloses a controlling device suitable for properly pre-setting the starting time of the heating element of the water heater, by means of a temperature sensor (placed in the lower part of the tank) for checking the storage temperature and of a plurality of sensors (located in the upper part of the tank) for detecting the quantity of remaining hot water.
The solution disclosed in this document
It is also known that in some countries, especially in countries where electrical energy is produced from nuclear sources, there is the possibility of taking advantage of time bands of electrical energy supply at reduced rate. Such rates by time bands will become increasingly widespread in the future.
Where energy rates for household purpose are differentiated by time bands, the houses are provided with information instruments and means that allow knowing the start and end time of said time bands and of course, counting the consumptions recorded in each band at the different rates.
It is also known that the methane distribution network, at least in certain zones, is overloaded in certain periods, for example during room heating; as a consequence, it is not excluded that sooner or later, methane suppliers may activate rate policies aimed at encouraging the postponement of consumptions, delaying them to certain low consumption time bands, as it happens with electrical energy.
In the description of this invention, hereinafter, "energy supply network" means without distinction both the supply of electrical energy and of methane, whereas "heating element" means without distinction both the group of electrical resistances of an electrical water heater and the combustion unit of a gas water heater.
The method according to the invention, hereinafter called "ECO method", usefully applies to both electrical and gas storage water heaters.
The main object of the ECO method is to reduce thermal energy dispersions, being equal the temperature of water made available to the user at the time of the first expected use.
A further object of the ECO method is to take advantage of the energy time bands at reduced rate.
A further object of the ECO method consists in preventing overloads in the household methane or electrical energy distribution network at the beginning of the reduced rate bands, when other appliances that activate at that time are connected to the same network.
A further object of the ECO method is to adjust the water temperature, automatically adjusting it to the actual user's requirements.
These and other objects are achieved with the method and control as defined in claims 1 or 18.
The ECO method allows reducing consumptions by thermal dispersion acting according to two main procedures, each envisaging multiple variants.
The execution of such two procedures requires the water heater to be piloted by an electronic control provided with means suitable at least for performing the following functions:
The first function, hereinafter called "Delay", is intended to carry out the heating of the appliance to the preset temperature T.set during the time band at reduced rate, but postponing the complete heating as much as possible, so that it may end just before the end of such time band at reduced rate (the so-called peak-off period).
The second function, hereinafter called "Optimisation", optimises the maintenance temperature automatically reducing the preset value T.set if the water heater is not usually used at full capacity thereof, that is, if the user has set a temperature T.set unusually high for his/her actual uses.
The ECO method may be activated/deactivated by pressing a simple key, for example located on the front of the generic storage water heater, or the Delay and Optimisation functions may be activated independently of each other, only one or both.
The Delay function shall now be described in greater detail.
The water heater electronic control monitors the energy supply network to identify the current rate type.
According to a version of the Delay function, the electronic control has the water heating speed v.r pre-stored, according to the model of water heater it is installed on; in fact, such speed is known knowing the electrical power P.w, the thermal dispersions Q.d and the thermal capacity C of the water heater model in question. It is noted, however, that such speed may be considered as valid only if a certain approximation is accepted, that is, if we set aside the fact that, according to the type of each model in operation:
According to this first version of the Delay function, then, the electronic control at the beginning of a band at reduced rate F.rid, starts a heating step F.2 during which:
By delaying the water heating to the last possible time, while performing it entirely within the time band at reduced rate, besides taking advantage of such rate there is the dual advantage of:
According to a useful additional version of the Delay function, said heating step F.2, suitable for reaching the preset temperature T.set starting from said initial temperature T.2, is preceded by a preheating step F.1.
According to such version, the electronic control enables the activation of the heating of the water heater with a delay time D.tr (for example, D.tr = 30 minutes) relative to the beginning of the band at reduced rate F.rid, so as to prevent said possible initial power absorption peaks.
Once the delay time D.tr has elapsed, only a preheating is allowed wherein from the initial temperature T.1, the water heater is made to reach a stand-by temperature T.sb, generally much lower than the water temperature set by the user T.set and preferably equal or close to the useful temperature T.u which, for example, is equal to 45 °C. The electronic control records the actual time Dt.1 of preheating from the initial temperature T. 1 to the stand-by temperature T.sb.
At this point the electronic control, the initial T.1 and stand-by T.sb temperatures and the actual time Dt.1 of the first preheating step F.1 being known, is capable of calculating the actual heating speed v.r of the water heater in those specific operating conditions and replacing the data optionally pre-stored with the new updated value.
The preheating step F. 1 as described offers the advantages of:
The heating step F.2 for reaching the preset temperature T.set follows, exactly as already described above, wherein of course:
The Delay function allows money saving as it activates the water heater during the band at reduced rate F.rid and energy saving, thanks to the keen-witted use of times within such band.
There may be cases wherein the electronic control is instructed not to carry out the preheating step F.1, even if it is activated by the user, and to switch directly to the heating step F.2.
By way of an example, the electronic control may ignore the preheating step F.1 if:
The Optimisation function shall now be described in detail.
In known storage water heaters, the water temperature maintenance value T.set, even if it is adjustable by the user, is normally unchanged with the time of the day and the day of the week.
According to the Optimisation function, said maintenance value T.set is optimised according to the actual water usage, making it variable according to the day of the week, and optionally for each day, according to the time, so as to keep into account the different water uses that there may be on holidays and working days, or more in general, also the time and in a different manner for each day of the week.
To this end, according to the Optimisation function, for each day of the week GG and at the end of consecutive periods of time Pt that cover the entire day, the storage temperature value T.acc and the maintenance value T.set are checked, for the same period of time of the same day of the next week, and such maintenance value T. set is changed or kept unchanged according to the storage temperature T.acc found.
More precisely, the maintenance value T.set is:
The procedure described above may be performed in various more or less accurate manners.
According to a first manner, said consecutive periods of time Pt consist in a single period of 24 hours. That is, the storage temperature T.acc is monitored at the time of usage end h.set of each day, wherein "h.set" means the time when the water heater daily use ends. Such usage end time h.set may be pre-stored in the electronic control and usually, it is a late evening time.
In order to understand for each day of the week which the actual usage end time h.set is, a time monitoring is useful: when only a slight temperature drop due to thermal dispersions is sensed from one hour to the next one, this means that no hot water was used within that time range.
Therefore, the time monitoring allows detecting the profile of daily uses, as a general rule different every day of the week, and thus store the actual usage end time h.set of each day as the last time of the day after which no temperature drops are sensed if not due to thermal dispersions.
The actual usage end time h.set of each day is then stored in place of the previous values.
At this point, if at the usage end time h.set the storage temperature T.acc is higher than the useful temperature T.u by a positive amount ΔT.ecc, this means that the preset temperature T.set may be reduced by the same positive amount ΔT.ecc, without absolutely affecting the user requirements.
On the contrary, if at the usage end time h.set the storage temperature T.acc is below the useful temperature T.u, by a negative amount ΔT.dif, this indicates that the user was not able to obtain the expected uses and that therefore, the preset temperature T.set must be increased at least by the same negative amount ΔT.dif, even if this is not necessarily sufficient to meet the user requirements.
This being said, the following variation to the Optimisation function is possible:
As an alternative to a number of sampling days GG equal to 7, it is possible to consider a number of sampling days GG equal to a multiple of seven, whereas for the optional change of the preset temperature T.set, the mean value of the storage temperatures T.acc sensed on the same day of the week is taken into account, that is, the generic day GG, day GG + 7 and so on.
Said procedure may be carried out periodically for even consecutive sequences of days, in order to check any changes in the user's habits.
As another alternative, the storage temperature value T.acc considered is that resulting from the mobile average of samplings made in the last SS weeks, where for example the number of weeks SS is equal to two.
As regards the actual usage end time h.set for each day of the week, as may be sensed by the above time monitoring, this may be continuously updated too, according to the same methods just described for the determination of the storage temperature T.acc. Without departing from the scope of the invention, the Optimisation function may envisage the following simplified procedure, at least as regards the methods for changing the preset temperature T.set.
According to such version, the Optimisation function:
Another simplifying version may relate to the definition of the usage end time h.set which, instead of being preset for every day of the week or being calculated by studying the profile of daily usage, may consist in the time of start of the time band at reduced rate.
A further version may consist in the fact that in order to optimise the maintenance temperature automatically varying the preset value T.set, the electronic control performs a monitoring of the storage temperature T.acc at multiple times of each day rather than only at the usage end time h.set of each day, at which the daily use of the water heater ends, as already described in detail.
Said last version of the monitoring therefore allows measuring a more detailed profile of daily uses, as it is capable of controlling the storage temperature T.acc every "H" hours within a day, for example every hour or every 4/6 hours, and consequently proceeding to the variation of the preset temperature T.set for each period Pt expiring at the H-teenth hour.
As described above, in particular, for each period Pt, the electronic control proceeds to a reduction of the preset temperature T.set if the storage temperature T.acc is higher than a maximum predetermined threshold T.s.max, whereas it proceeds to an increase of the preset temperature T.set if the storage temperature T.acc is less than a minimum predetermined threshold T.s.min. On the contrary, it keeps the temperature T.set unchanged if such storage temperature T.acc is comprised between said minimum threshold T.s.min and maximum threshold T.s.max.
By way of an example and without any limiting purpose, said reduction or increase of the preset temperature T.set is equal to 1-2 °C, whereas said minimum predetermined threshold T.s.min is still equal to 35 °C and said maximum predetermined threshold T.s.max is still equal to 45 °C.
The Optimisation function as described is capable of building a different profile of the preset water maintenance temperature T.set for each day of the week.
In general, without departing from the scope of the invention, the sampling days GG, rather than being 7 or a multiple of 7 are only one or a generic number M of days.
In general, therefore, the number of sampling days is equal to GG or a multiple M.GG, where GG is equal to 1 or 7.
The number of sampling days GG or M.GG may be predetermined by the manufacturer or it may be set by the user.
However, nothing prevents a very simplified version wherein the sampling days GG, rather than being 7 or a multiple of 7 are 1 or "a multiple of 1", or still the sampling may be performed not in days but hours, meaning that no difference is made between days of the week, and any consecutive sampling days are only used to sense the average value or the minimum value of storage temperatures T.acc.
In general, therefore, the number of sampling days is equal to GG or a multiple M.GG, where GG is equal to 1 or 7, or the sampling does not take place in hours.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.