U.S. patent application number 14/122420 was filed with the patent office on 2015-06-04 for method and system for buffering thermal energy and thermal energy buffer system.
This patent application is currently assigned to VLAAMSE INSTELLING VOOR TECHNOLOGISCH ONDERZOEK (VITO). The applicant listed for this patent is Bert CLAESSENS, Reinhilde D'HULST, Johan VAN BAEL, Koen VANTHOURNOUT. Invention is credited to Bert CLAESSENS, Reinhilde D'HULST, Johan VAN BAEL, Koen VANTHOURNOUT.
Application Number | 20150153071 14/122420 |
Document ID | / |
Family ID | 44856248 |
Filed Date | 2015-06-04 |
United States Patent
Application |
20150153071 |
Kind Code |
A2 |
VANTHOURNOUT; Koen ; et
al. |
June 4, 2015 |
METHOD AND SYSTEM FOR BUFFERING THERMAL ENERGY AND THERMAL ENERGY
BUFFER SYSTEM
Abstract
A method for buffering thermal energy comprises a thermal
buffering medium contained by a thermal energy buffer. The volume
of the thermal buffering medium is subdivided in one or more parts
such that the different parts of the volume of the thermal
buffering medium together form the total thermal buffering medium.
The thermal energy buffer comprises a temperature sensor for each
part. A controller has at least one signal representing at least
one thermal energy value related to the thermal energy buffer. The
thermal energy values comprise a predetermined minimum amount of
thermal energy present in the thermal energy buffer. The controller
controls a heater such that the amount of thermal energy present in
the thermal energy buffer is higher than or equals the
predetermined minimum amount of energy present in the thermal
energy buffer.
Inventors: |
VANTHOURNOUT; Koen; (Mol,
BE) ; VAN BAEL; Johan; (Westerlo, BE) ;
CLAESSENS; Bert; (Spalbeek, BE) ; D'HULST;
Reinhilde; (Mol, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VANTHOURNOUT; Koen
VAN BAEL; Johan
CLAESSENS; Bert
D'HULST; Reinhilde |
Mol
Westerlo
Spalbeek
Mol |
|
BE
BE
BE
BE |
|
|
Assignee: |
VLAAMSE INSTELLING VOOR
TECHNOLOGISCH ONDERZOEK (VITO)
Mol
BE
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20140190680 A1 |
July 10, 2014 |
|
|
Family ID: |
44856248 |
Appl. No.: |
14/122420 |
Filed: |
June 4, 2012 |
PCT Filed: |
June 4, 2012 |
PCT NO: |
PCT/EP2012/060527 PCKC 00 |
371 Date: |
November 26, 2013 |
Current U.S.
Class: |
165/287 |
Current CPC
Class: |
Y02E 60/14 20130101;
F24D 19/1063 20130101; F28F 27/00 20130101; F24H 9/2014 20130101;
G01K 17/06 20130101; Y02E 60/142 20130101; F28D 20/0039 20130101;
G01K 17/00 20130101; F28D 2020/0078 20130101; G05D 23/1923
20130101; G05D 23/1931 20130101; F24D 2240/26 20130101; F24H 9/2021
20130101 |
International
Class: |
F24H 9/20 20060101
F24H009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 3, 2011 |
EP |
11168672.1 |
Claims
1.-53. (canceled)
54. A method for buffering thermal energy in a thermal buffering
medium wherein contained within a thermal energy buffer wherein
having a controller wherein, wherein at least one signal
representing thermal energy values related to the thermal energy
buffer is provided to the controller wherein, the thermal energy
values comprising a maximal amount of heating energy, a
predetermined minimum amount of thermal energy present in the
thermal energy buffer and an amount of thermal energy present in
the thermal energy buffer, wherein the controller wherein controls
a heater wherein of the thermal buffer wherein, and wherein the
controller wherein calculates a value representing the amount of
thermal energy present in the thermal energy buffer, wherein the
thermal energy values comprise a minimal amount of heating energy
representing the amount of energy required to, using the heater
wherein, heat all the thermal buffering medium wherein to a
predetermined minimum temperature starting from the amount of
thermal energy present in the thermal energy buffer wherein, and
the thermal energy values also comprise a maximal amount of heating
energy representing the amount of energy required to heat all the
thermal buffering medium wherein to the predetermined maximum
temperature, using the heater wherein, starting from the amount of
thermal energy present in the thermal energy buffer wherein,
wherein the volume of the thermal buffering medium wherein is
subdivided in one or more different parts wherein such that the
different parts wherein of the volume of the thermal buffering
medium wherein together form the total thermal buffering medium
wherein present in the thermal energy buffer wherein; and the
thermal energy buffer wherein comprises a respective temperature
sensor wherein for each part wherein for sensing a temperature of
the thermal buffering medium wherein contained in the part wherein,
the controller wherein calculates a value representing the amount
of thermal energy present in the thermal energy buffer by
multiplying the temperature measured by the one or more sensors
wherein sensing the temperature of the one or more different parts
wherein of the thermal buffering medium wherein with the volume of
the part of thermal buffering medium wherein such as to obtain at
least one value representing the partial thermal energy contained
in the at least one part by the thermal buffering medium wherein
and adding the resulting at least one partial thermal energy value
to each other, wherein the controller wherein calculates the
minimal amount of heating energy by multiplying the difference of
the predetermined minimum temperature and the temperature measured
by the one or more temperature sensors of the one or more parts
wherein containing thermal buffering medium having a temperature
measured by their respective sensors wherein which is lower than
the predetermined minimum temperature with the respective volumes
of the parts wherein containing thermal buffering medium wherein
and adding the resulting values to each other, and wherein the
controller wherein calculates the maximal amount of heating energy
by at least multiplying the difference of the predetermined maximum
temperature and the temperature measured by the one or more
temperature sensors wherein with the respective volume of the part
wherein corresponding to the temperature sensor wherein and adding
the resulting values to each other.
55. The method for buffering thermal energy according to claim 54,
wherein the thermal energy buffer wherein is a water heating unit
wherein of a domestic hot water system.
56. The method for buffering thermal energy according to claim 54,
wherein the thermal buffering medium wherein is water.
57. The method for buffering thermal energy according to claim 54,
wherein the controller wherein further calculates a state of charge
by dividing the value representing the amount of thermal energy
present in the thermal energy buffer with the value representing
the maximum amount of thermal energy stored in the thermal energy
buffer or the controller calculates the state of charge by dividing
the value representing the amount of thermal energy present in the
thermal energy buffer with the total volume of the thermal
buffering medium multiplied with the difference between the
predetermined minimum and maximum temperature.
58. The method for buffering thermal energy according to claim 21,
wherein the controller wherein uses the temperature measured by the
one or more temperature sensors wherein with respect to the
predetermined minimum temperature.
59. The method for buffering thermal energy according to claim 54,
wherein the controller wherein further calculates the amount of
thermal energy present in the thermal energy buffer wherein by only
using the parts wherein containing thermal buffering medium wherein
having a temperature measured by their respective sensor which is
higher than or equal to the predetermined minimum temperature.
60. The method for buffering thermal energy according to claim 54,
wherein the one or more different parts wherein subdividing the
volume of the thermal energy medium are provided on top of each
other along an upright direction forming a stack of parts
wherein.
61. The method for buffering thermal energy according to claim 54,
wherein the heater wherein is positioned below the lowest
temperature sensor wherein.
62. The method for buffering thermal energy according to claim 54,
wherein wires wherein interconnecting the different temperature
sensors wherein to the controller wherein are guided to the outside
of the thermal energy buffer wherein at substantially the
respective locations of the temperature sensors wherein.
63. A thermal energy buffering system having a thermal buffering
medium wherein contained within a thermal energy buffer wherein
having a controller wherein, comprising Means for providing at
least one signal representing thermal energy values related to the
thermal energy buffer to the controller wherein, the thermal energy
values comprising a maximal amount of heating energy, a
predetermined minimum amount of thermal energy present in the
thermal energy buffer and an amount of thermal energy present in
the thermal energy buffer, wherein the controller wherein is
adapted to control a heater wherein of the thermal buffer wherein,
and wherein the controller wherein is adapted to calculate a value
representing the amount of thermal energy present in the thermal
energy buffer, wherein the controller wherein is adapted to
calculate the thermal energy values including: a minimal amount of
heating energy representing the amount of energy required to, using
the heater wherein, heat all the thermal buffering medium wherein
to a predetermined minimum temperature starting from the amount of
thermal energy present in the thermal energy buffer wherein, and a
maximal amount of heating energy representing the amount of energy
required to heat all the thermal buffering medium wherein to a
predetermined maximum temperature, using the heater wherein,
starting from the amount of thermal energy present in the thermal
energy buffer wherein, wherein the volume of the thermal buffering
medium wherein is subdivided in one or more different parts wherein
such that the different parts wherein of the volume of the thermal
buffering medium wherein together form the total thermal buffering
medium wherein present in the thermal energy buffer wherein; and
the thermal energy buffer wherein comprises a respective
temperature sensor wherein for each part wherein for sensing a
temperature of the thermal buffering medium wherein contained in
the part wherein, the controller wherein is adapted to calculate a
value representing the amount of thermal energy present in the
thermal energy buffer by multiplying the temperature measured by
the one or more sensors wherein sensing the temperature of the one
or more different parts wherein of the thermal buffering medium
wherein with the volume of the part of thermal buffering medium
wherein such as to obtain at least one value representing the
partial thermal energy contained in the at least one part by the
thermal buffering medium wherein and adding the resulting at least
one partial thermal energy value to each other, wherein the
controller wherein is adapted to calculate the minimal amount of
heating energy by multiplying the difference of the predetermined
minimum temperature and the temperature measured by the one or more
temperature sensors of the one or more parts wherein containing
thermal buffering medium having a temperature measured by their
respective sensors wherein which is lower than the predetermined
minimum temperature with the respective volumes of the parts
wherein containing thermal buffering medium wherein having a
temperature measured by their respective sensors wherein which is
lower than the predetermined minimum temperature and adding the
resulting values to each other, and the controller wherein is
adapted to calculate the maximal amount of heating energy by at
least multiplying the difference of the predetermined maximum
temperature and the temperature measured by the one or more
temperature sensors wherein with the respective volume of the part
wherein corresponding to the temperature sensor wherein and adding
the resulting values to each other.
64. The system according to claim 63, wherein the thermal energy
buffer wherein is a water heating unit wherein of a domestic hot
water system.
65. The system according to claim 63, wherein the thermal buffering
medium wherein is water.
66. The system according to claim 63, wherein the controller
wherein is adapted to further calculate the state of charge by
dividing the value representing the amount of thermal energy
present in the thermal energy buffer with the value representing
the maximum amount of thermal energy stored in the thermal energy
buffer or the controller calculates the state of charge by dividing
the value representing the amount of thermal energy present in the
thermal energy buffer with the total volume of the thermal
buffering medium multiplied with the difference between the
predetermined minimum and maximum temperature.
67. The system according to claim 63, wherein the controller
wherein is adapted to use the temperature measured by the one or
more temperature sensors wherein with respect to the predetermined
minimum temperature.
68. The system according to claim 63, wherein the controller
wherein is adapted to further calculate the amount of thermal
energy present in the thermal energy buffer wherein by only using
the parts wherein containing thermal buffering medium wherein
having a temperature measured by their respective sensor which is
higher than or equal to the predetermined minimum temperature.
69. The system according to claim 63, wherein the one or more
different parts wherein subdividing the volume of the thermal
energy medium are provided on top of each other along an upright
direction forming a stack of parts wherein.
70. The system according to claim 63, wherein the heater wherein is
positioned below the lowest temperature sensor wherein.
71. The system according to claim 63, wherein wires wherein
interconnecting the different temperature sensors wherein to the
controller wherein are guided to the outside of the thermal energy
buffer wherein at substantially the respective locations of the
temperature sensors wherein.
72. A computer program product having code segments which when
executed on a processing engine execute the method according to
claim 54.
73. A non-transient signal storage medium storing the computer
program product of claim 62.
Description
[0001] The current invention relates to a method for buffering
thermal energy according to the preamble of the first claim.
[0002] The present invention also relates to a thermal energy
buffer system for buffering thermal energy.
[0003] The present invention also relates to software for executing
the method or for implementing the above system.
[0004] Methods for buffering thermal energy and thermal energy
buffers are already known to the person skilled in the art. An
example of a thermal energy buffer is for example a water heating
unit of a domestic hot water system. Such a thermal energy buffer
contains a thermal buffering medium, often water, contained in a
tank and a controller controlling a heater of the thermal buffer.
The heater can for example be an electrical heater provided at the
bottom of the tank. In such water heating units, water often enters
the tank at the bottom of the tank and exits the tank at the top.
The controller is provided to receive a signal representing three
signals representing thermal energy values related to the thermal
energy buffer. These values purely represent temperatures and often
are a minimum temperature, a maximum temperature and the
temperature of the water in the tank measured by, for example, a
sensor present in the tank at a certain location. When the
temperature measured by the sensor drops below the minimum
temperature, the controller activates the heater, for example until
the maximum temperature is obtained. In such a configuration the
minimum temperature represents the predetermined minimum amount of
energy present in the thermal energy buffer.
[0005] However, such methods and corresponding water heating units
can not be readily implemented in a so called smart-grid in which
agents determine the functioning of the heater in function of
energy price, amount of energy needed, flexibility of the energy
consumption of the water heating unit, availability of renewable
energy, etc.
[0006] Moreover, it has been found that when multiple water heating
units of domestic hot water systems are for example controlled by a
single controller using the thermal energy values provided by the
different thermal energy buffers to the controller, the thermal
energy values being expressed in, for example, degrees Celsius,
controlling the water heating units in a consistent way such that
the amount of energy of the different water heating units can be
compared is not easy as the different thermal energy values are
determined for different water heating units having different
volumes for the tank, have different positions of the sensor
sensing the temperature of the water in the waterheating unit,
etc.
[0007] Although domestic water boilers of a complete population
consume a great deal of energy and hence could contribute to
maintaining stable network values if properly controlled, little
progress has been made in coordinating the switching of these
boilers other than to switch them on at night to make use of a
night tariff. Any network connections at domestic premises are a
potential security threat as they become easily accessible. It is
not obvious how to improve this situation.
[0008] Therefore, it is an object of the current invention to
provide an alternative method for buffering thermal energy and an
alternative thermal energy buffer system. To achieve certain
improvements embodiments of the present invention can provide one
or more advantages:
at least one thermal energy buffer can be controlled more easily by
a controller regardless of specific details of the thermal energy
buffer, local controllers can be used which do not require access
to wide area networks and their security threats while still
providing more flexibility of local control of heating energy, in
case of hierarchical market based control systems the demand bid
curve can be controlled effectively by provision of a suitable
control variable, in case of a time of use (ToU) demand response
system such as based on variable day-ahead prices for multiple
fixed time blocks per day, the scheduling of the energy buffer can
be based on the cheapest allocation of a first parameter with a
planning horizon proportional to a second parameter, and/or with
Variable Connection Capacity in which real time limits are set on a
household level for both consumption and production, the scheduling
of the energy buffer can also be based on the cheapest allocation
of a first parameter with a planning horizon proportional to a
second parameter.
[0009] Such benefits can be achieved according to the method for
buffering thermal energy according to any of claims 1 to 16 or 27
to 38.
[0010] For example, the controller calculates one or more values
representing amounts of thermal energy. According to preferred
embodiments of the current invention, the thermal energy values
comprise a minimal amount of heating energy representing the amount
of energy (E.sub.min) required to, using the heater, heat all the
thermal buffering medium to a predetermined minimum temperature
starting from the amount of thermal energy present in the thermal
energy buffer. The predetermined minimum temperature is preferably
the preferred minimum temperature at which water leaves the thermal
energy buffer.
[0011] According to preferred embodiments of the current invention,
the thermal energy values comprise a maximal amount of heating
energy (E.sub.max) representing the amount of energy required to,
using the heater, heat all the thermal buffering medium to a
predetermined maximum temperature starting from the amount of
thermal energy present in the thermal energy buffer.
[0012] It has been found that such a minimal and/or maximal amount
of heating energy allows the method or system to be employed
together with other devices in a smart grid control system with an
increased ease. [0013] According to preferred embodiments of the
current invention, the controller calculates the amount of thermal
energy present in the thermal energy buffer by dividing the value
representing the amount of thermal energy present in the thermal
energy buffer with the value representing the maximum amount of
thermal energy stored in the thermal energy buffer. The value is
the State of Charge (SoC). In a specific embodiment, the controller
calculates SOC, i.e. the amount of thermal energy present in the
thermal energy buffer by dividing the value representing the amount
of thermal energy present in the thermal energy buffer with the
total volume of the thermal buffering medium multiplied with the
difference between the predetermined minimum and maximum
temperature.
[0014] Another such value is the total amount, of thermal energy
present in the thermal energy buffer, said value being the sum of
values each representing the thermal energy measured for a
different part of the thermal buffering medium and each calculated
by multiplying the temperature measured by the sensor of at least
one part of the thermal buffering medium with the volume of the
part of thermal buffering medium such as to obtain at least one
value representing the partial thermal energy contained in the at
least one part by the thermal buffering medium.
[0015] Such a calculated thermal energy value, next to taking into
account the temperature of the volume of thermal buffering medium,
such as for example water, also takes into account the volume
itself of the thermal buffering medium such that a better
representation of the energy content of the thermal buffering
medium is obtained. Such an energy content can then be used to
represent the thermal energy values and it has been found that, for
example, thermal energy values represented in this way can be
successfully used to control completely different thermal energy
buffers with a single controller.
[0016] Moreover, it has been found that such a thermal energy
buffer can be used in a smart grid control system such as for
example the method described in the European patent application
EP11162735.2.
[0017] Embodiments of the present invention can provide one or more
advantageous technical solutions:
at least one thermal energy buffer can be controlled more easily by
a controller regardless of specific details of the thermal energy
buffer by using an interface that provides certain energy values
that can be used for control purposes. These values can include any
of, any combination of, or all of E.sub.max, E.sub.min, State of
charge (SoC) and optionally for example SoC.sub.min which is the
minimum SoC that must be maintained by any demand response control
system to ensure that hot water is available to meet users'
immediate demands and/or P, the electrical power consumption of the
buffer; local controllers can be used which do not require access
to wide area networks and their security threats while still
providing more flexibility of local control of heating energy, in
case of hierarchical market based control systems the demand bid
curve can be controlled effectively by provision of a suitable
control variable such as a slope or priority inversely proportional
to SoC-SoC.sub.min, weighted proportional to E.sub.min; in case of
a time of use (ToU) demand response system such as based on
variable day-ahead prices for multiple fixed time blocks per day,
the scheduling of the energy buffer can be based on the cheapest
allocation of a first parameter such as t.sub.max with a planning
horizon proportional to a second parameter such as SoC-SoC.sub.min,
and/or with Variable Connection Capacity (VCC) in which real time
limits are set on a household level for both consumption and
production, the scheduling of the energy buffer can also be based
on the cheapest allocation of a first parameter t.sub.max with a
planning horizon proportional to a second parameter such as
SoC-SoC.sub.min, tmax is not explained. tmax is the time required
to fully charge the buffer.
[0018] According to preferred embodiments of the current invention,
the thermal energy buffer is a water heating unit of a domestic hot
water system.
[0019] According to preferred embodiments of the current invention,
the thermal buffering medium is water.
[0020] According to further preferred embodiments according to the
current invention, the controller calculates the minimal amount of
heating energy by multiplying the difference of the predetermined
minimum temperature and the temperature measured by the one or more
temperature sensors of the one or more parts containing thermal
buffering medium having a temperature measured by their respective
sensors which is lower than the predetermined minimum temperature
with the respective volumes of the parts containing thermal
buffering medium having a temperature measured by their respective
sensors which is lower than the predetermined minimum temperature
and adding the resulting values to each other.
[0021] According to further preferred embodiments of the current
invention, the controller calculates the maximum amount of heating
energy by at least multiplying the difference of the predetermined
maximum temperature and the temperature measured by the one or more
temperature sensors with the respective volume of the part
corresponding to the temperature sensor and adding the resulting
values to each other.
[0022] Such a calculated minimal and/or maximal thermal energy
value, next to taking into account the temperature of the volume of
thermal buffering medium, such as for example water, also takes
into account the volume itself of the thermal buffering medium
considered. Such an energy content can be easily used to represent
the thermal energy values and it has been found that, for example,
thermal energy values represented in this way can be successfully
used to control completely different thermal energy buffers with a
single controller. For example, it has been found that such a
thermal energy buffer can be used in the method described in the
European patent application EP11162735.2.
[0023] According to further preferred embodiments of the current
invention the controller uses the temperature measured by the one
or more temperature sensors with respect to the predetermined
minimum temperature. Such an embodiment, especially in combination
with the previous embodiment, allows to calculate the amount of
thermal energy present in the thermal energy buffer relative to the
maximum total amount of energy which can be present in the thermal
energy buffer, defined by the multiplication of the predetermined
maximum temperature and the total volume of the thermal buffering
medium, and with respect to the predetermined minimum
temperature.
[0024] According to preferred embodiments of the current invention,
the controller further calculates the amount of thermal energy
present in the thermal energy buffer by only using the parts
containing thermal buffering medium having a temperature measured
by their respective sensor which is higher than or equal to the
predetermined minimum temperature. According to such embodiments,
the amount of thermal energy present in the thermal energy buffer
calculated by the controller for example range from 0 to 1, such
that an indication of the state of charge of the thermal energy
buffer can be provided by the controller which can be interpreted
independently from other parameters and which therefore can be
incorporated in smart grid network with increased ease. If required
the indication of the state of charge can be represented as a
percentage by multiplying it by 100.
[0025] According to preferred embodiments of the current invention,
the one or more parts subdividing the volume of the thermal energy
medium are provided on top of each other along an upright direction
forming a stack of parts. Such a subdivision of the volume of the
thermal buffering medium has been found to result in good
representations of the amount of thermal energy present in the
thermal energy buffer. Indeed, in such thermal buffers, such as for
example water heating units of domestic hot water systems, a
vertical distribution of temperatures of the thermal buffering
medium is present, which can be relatively good approximated by
such a stack of parts.
[0026] According to preferred embodiments of the current invention,
the heater is positioned below the lowest temperature sensor. It
has been found that such a positioning allows a better
representation of the thermal energy present in the thermal energy
buffer.
[0027] According to preferred embodiments of the current invention,
wires interconnecting the different temperature sensors to the
controller are guided to the outside of the thermal energy buffer
at substantially the respective locations of the temperature
sensors. Such an interconnection of the different wires
interconnecting the temperature sensors to the controller prevents
that temperature sensors near wires leaving the thermal energy
buffer at the same location are unwontedly affected by a leakage of
heat along these wires giving rise to an unwanted disturbance of
the temperature measurement by the temperature sensor, as is for
example the case when the different wires coming from the different
temperature sensors are assembled within the thermal energy buffer
and leave the thermal energy buffer at substantially that same
location, the different wires, often being made of material having
good thermal conducting properties, in such a case forming a heat
or cold bridge to the outside having an increased risk for heat
leaving the thermal energy buffer along it.
[0028] The invention also relates to a thermal energy buffer system
provided for performing the method according to the invention,
comprising a thermal energy buffer and a controller according to
any of the claims 17 to 24 or 39 to 49.
[0029] The present invention also provides a computer program
product having code segments which when executed on a processing
engine execute any of the methods according to the present
invention or implements the system in accordance with any of the
embodiments of the present invention.
[0030] The present invention also provides a non-transient signal
storage medium for storing the computer program product. The
storage medium can be for example an optical disk such as a CD-Rom
or DVD-ROM, a magnetic tape, a magnetic disk, a solid state memory
etc.
[0031] The present invention also provides a controller for
buffering thermal energy of a thermal energy buffer, the controller
being adapted to perform a method according to the present
invention or implement a system in accordance with the present
invention. The controller can be implemented as a microcontroller
and may include a processor such as a microprocessor or an FPGA and
one or more memories. The processor can be adapted to execute any
of the software of the present invention.
[0032] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention and how it may be practiced in particular
embodiments. However, it will be understood that the present
invention may be practiced without these specific details. In other
instances, well-known methods, procedures and techniques have not
been described in detail, so as not to obscure the present
invention.
[0033] The present invention will be described with respect to
particular embodiments and with reference to certain drawings but
the invention is not limited thereto but only by the claims. The
drawings described are only schematic and are non-limiting. In the
drawings, the size of some of the elements may be exaggerated and
not drawn on scale for illustrative purposes. The dimensions and
the relative dimensions do not necessarily correspond to actual
reductions to practice of the invention.
[0034] Furthermore, the terms first, second, third and the like in
the description and in the claims, are used for distinguishing
between similar elements and not necessarily for describing a
sequential or chronological order. The terms are interchangeable
under appropriate circumstances and the embodiments of the
invention can operate in other sequences than described or
illustrated herein.
[0035] Moreover, the terms top, bottom, over, under and the like in
the description and the claims are used for descriptive purposes
and not necessarily for describing relative positions. It is to be
understood that the terms so used are interchangeable under
appropriate circumstances and that the embodiments of the invention
described herein are capable of operation in other orientations
than described or illustrated herein.
[0036] The term "comprising", used in the claims, should not be
interpreted as being restricted to the means listed thereafter; it
does not exclude other elements or steps. It needs to be
interpreted as specifying the presence of the stated features,
integers, steps or components as referred to, but does not preclude
the presence or addition of one or more other features, integers,
steps or components, or groups thereof. Thus, the scope of the
expression "a device comprising means A and B" should not be
limited to devices consisting only of components A and B.
[0037] FIG. 1 shows an overview of a thermal energy buffer system
according to the invention.
[0038] FIG. 2a shows a simulation of the temperature sensed by the
different sensors along height direction of the thermal energy
buffer 10, in this case a water heating unit 18, in function of
time after initially using all heater water contained in the
thermal energy buffer 10 and subsequently heating the newly added
water which initially entered the heating unit at about 15.degree.
C.
[0039] FIG. 2b shows different thermal energy values such as the
state of charge 28, the E.sub.max 29 and the E.sub.min 30.
[0040] FIGS. 3a and 3b show the results of a different simulation
as the one shown in FIGS. 2a and 2b.
[0041] The thermal energy system 1 is provided for performing the
method according to the invention and thereto comprises a thermal
energy buffer 10 and a controller 3 provided to perform the method
according to the invention.
[0042] FIG. 1 shows that the thermal energy buffer 10 and the
controller 3 are incorporated in a single device, in this case a
domestic system, more specifically a domestic hot water system,
even more specific a water heating unit 18 of a domestic hot water
system. Such a configuration for example allows to replace an older
water heating unit by a new water heating unit 18 with a controller
without having to adapt the contacts with, for example, the power
grid, etc. This is however not critical for the invention and the
controller 3 and the thermal energy buffer 10 can also be
physically different devices, for example when several thermal
energy buffers 10 are connected to a single controller 3, allowing
reduction of the number of controllers 3 necessary.
[0043] The thermal energy buffer 10 contains thermal buffering
medium 2 which preferably is a liquid thermal buffering medium. The
thermal buffering medium 2 can be any medium known to the person
skilled in the art which allows to store thermal energy in it, but
preferably is water as water is known to have good thermal storage
properties, is safe and is widely available. Moreover, but not
limited thereto, in such case the thermal energy buffer can also be
used to provide a household with warm water making it a water
heating unit 18 of a domestic hot water system. This is however not
critical for the invention and the thermal energy buffer 10 can
also be used in combination with a heat pump such that heat
recovered by the heat pump can be temporarily stored in the thermal
energy buffer 10.
[0044] Other buffering media are however also possible, such as for
example gels having good thermal storage properties.
[0045] The controller 3 is provided to control a heater 4 of the
thermal buffer 10. The heater 4 shown in FIG. 1 is an electric
heater and is situated at the bottom of a tank inside the thermal
energy buffer 10. Such a configuration is however not critical for
the invention. It is for example possible to provide a heater 4
which is not electric but which, for example, uses gas, petrol,
diesel fuel, etc. Also, the position of the heater 4 is not
critical for the invention and can be at the bottom, near the
middle, near the top, etc. However, by providing the heater 4 near
the bottom it has been found that natural heat convection of the
thermal buffering medium 2 when heated by the heater 4 allows that
the thermal buffering medium 2 is heated homogeneously, as depicted
for example in FIG. 2a which will be explained in more detail
below.
[0046] The thermal energy buffer 10 shown in FIG. 1 comprises an
inlet 5 and an outlet 6. The inlet 5 is positioned such that the
thermal buffering medium 2 enters the thermal energy buffer at the
bottom and the outlet 6 is positioned such that the thermal
buffering medium 2 exits the thermal energy buffer 10 at the top.
This has as a consequence that heated thermal buffering medium 2,
which rises to the top due to convection, becomes near to the
outlet 6. As the heater 4 preferably is located near the bottom,
cold thermal buffering medium 2 entering near the bottom through
the inlet 5, is heated by the heater 4 and afterwards rises to the
top where the outlet 6 is located. Such a configuration has been
found to further improve the homogeneous heating of the thermal
buffering medium 2.
[0047] The exact configuration of the inlet 5 and the outlet 6 is
not critical for the invention. Although they are shown here as
pipes entering and leaving the thermal energy buffer 10 at the
bottom and the top respectively, this is not critical for the
invention. For example the inlet pipe 5 could for example enter the
thermal energy buffer at the top of the thermal energy buffer going
down through the thermal energy buffer 10 such that the thermal
buffering medium 2 exits the inlet 5 near the bottom of the thermal
energy buffer 10.
[0048] Preferably, the inlet 5 and the outlet 6 are configured such
that the thermal energy buffer 10, preferably the tank provided in
it, is substantially always, preferably always, filled with thermal
buffering medium. Preferably this is obtained by configuring the
inlet 5 and the outlet 6 such that when thermal buffering medium 2
is drawn from the thermal energy buffer 10 through the outlet 6,
new thermal buffering medium 2 is led into the thermal energy
buffer through the inlet 5 until the thermal energy buffer 2 is,
preferably its tank, is filled again with thermal buffering medium
2 such that the tank remains substantially filled, preferably
filled.
[0049] The volume of the thermal buffering medium 2, and
accordingly the tank of the thermal energy buffer in which it is
contained, is subdivided in at least one part 21 and suitably in a
number of parts 21, 22, 23, 24, 25, 26, 27. Preferably, at least
two parts are provided, more preferably even more such as for
example at least three, four, five, six, seven eight, etc. The
number of parts is not limited and can be determined by the person
skilled in the art. As can be seen in FIG. 1, the parts 21, 22, 23,
24, 25, 26, 27 subdividing the volume of the thermal energy medium
are provided on top of each other along an upright direction
forming a stack of parts 21, 22, 23, 24, 25, 26, 27.
[0050] As can be seen in FIG. 1, the different parts 21, 22, 23,
24, 25, 26, 27 of the volume of the thermal buffering medium 2
together form the total thermal buffering medium 2 present in the
thermal energy buffer 10 and the thermal energy buffer 10 comprises
a number of respective one or more temperature sensors 11, 12, 13,
14, 15, 16, 17 for each part 21, 22, 23, 24, 25, 26, 27 for sensing
a temperature of the thermal buffering medium 2 contained in the
corresponding part 21, 22, 23, 24, 25, 26, 27. In combination with
the preferred stack of parts 21, 22, 23, 24, 25, 26, 27, it has
been found that such a configuration allows an improved way of
sensing the temperature profile of the thermal buffering medium 2
as the temperature varies substantially only in height direction.
As for the parts, the number of temperature sensors is not limited
and can be determined by the person skilled in the art.
[0051] Although the parts 21, 22, 23, 24, 25, 26, 27 are indicated
as such in FIG. 1, it is to be understood that the parts 21, 22,
23, 24, 25, 26, 27 only imaginarily subdivide the volume of thermal
buffering medium 2 and not physically.
[0052] Preferably, the sensors 11, 12, 13, 14, 15, 16, 17 are
placed along the thermal energy buffer 10 such that the position of
each of these sensors corresponds to the position of each of the
corresponding parts 21, 22, 23, 24, 25, 26, 27 subdividing the
total volume of the thermal buffering medium 2. Thereto, preferably
the temperature sensors are equidistantially distributed along the
height of the thermal energy buffer 10, or along the height of the
tank 18 comprised by the thermal energy buffer 10 and containing
the thermal buffering medium 2.
[0053] The controller 3 is provided with at least one signal
representing at least one thermal value related to the thermal
energy buffer, wherein the at least one thermal energy value
comprises a predetermined minimum amount of energy present in the
thermal energy buffer and an amount of thermal energy present in
the thermal energy buffer.
[0054] The controller 3 for buffering thermal energy of a thermal
energy buffer is adapted to perform a method according to the
present invention or implement a system in accordance with the
present invention. The controller can be implemented as a
microcontroller and may include a processor such as a
microprocessor or an FPGA and one or more memories. The processor
can be adapted to execute any of the software of the present
invention.
[0055] The predetermined minimum amount of energy preferably can be
set by a user through an interface which is connected to the
controller. The interface can for example be provided on the
thermal energy buffer 10 in the form of a screen, possibly with
buttons added to the screen, reflecting information of the thermal
energy buffer 10. This is however not critical for the invention
and the interface can also be a computer 8 which is connected to
the controller 3, over for example a computer network 7. The
computer network 7 can for example be a LAN or the internet and can
be a physical wire or, for example, wireless network such as for
example WIFI. The controller 3, for example, is provided with a
server application, for example a web server application, allowing
the computer 8 to log in to the website to set, for example, the
predetermined values of the thermal energy values.
[0056] The controller 3 is provided to calculate a value
representing the amount of total thermal energy present in the
thermal energy buffer by multiplying the temperature measured by
each sensor 11, 12, 13, 14, 15, 16, or 17 corresponding to
respectively part 21, 22, 23, 24, 25, 26, 27 of the thermal
buffering medium 2 with the volume of the corresponding part of
thermal buffering medium 2 such as to obtain a value representing
the partial thermal energy contained in the corresponding part of
the thermal buffering medium 2 and adding the resulting partial
thermal energy values to each other.
[0057] The controller 3 shown in FIG. 1 directly interconnects the
heater 4 to the power grid through power lines 19, 20. This is
however not critical for the invention and the controller 3 could
also control a separate switch connecting/disconnecting the heater
4 to the power grid. Naturally, in stead of a power grid, depending
on the type of heater 4, a different source of heat can be used
such as for example diesel fuel, gas, etc.
[0058] Preferably, the controller 3 further calculates the amount
of thermal energy present in the thermal energy buffer 10 by only
using the parts 21, 22, 23, 24, 25, 26, 27 containing thermal
buffering medium 2 having a temperature measured by their
respective sensor which is higher than or equal to a predetermined
minimum temperature, which may be part of the thermal energy
values. For example, when new thermal buffering medium 2 has
entered the thermal energy buffer 10 at the bottom of the thermal
energy buffer 10, the temperature sensors at the bottom will record
a temperature which may be lower than the predetermined minimum
temperature such that these parts are not taken into account when
calculating the thermal energy present in the thermal energy buffer
10.
[0059] Preferably, the controller 3 uses the temperature measured
by the temperature sensors 11, 12, 13, 14, 15, 16, 17 with respect
to the predetermined minimum temperature. This is preferably done
by a subtraction of the measured temperature with the predetermined
minimum temperature.
[0060] Preferably, the thermal energy values also comprise a
predetermined maximum temperature, which preferably can be set by a
user according to his preferences, such as for example the desired
level of comfort. Preferably, the predetermined maximum temperature
is determined such that the thermal buffering medium, which
preferably liquid or semi-liquid, does not start boiling as in such
case the pressure inside the preferred tank of the thermal energy
buffer would start to rise such that the risk that explosions occur
would increase.
[0061] Preferably, the controller 3 further calculates the amount
of thermal energy present in the thermal energy buffer 10 by
dividing the value representing the amount of thermal energy
present in the thermal energy buffer with the value representing
the maximum amount of thermal energy stored in the thermal energy
buffer. The value is the State of Charge (SoC). In a specific
embodiment, the controller calculates SoC, i.e. In a specific
embodiment, the controller calculates SOC, i.e. the amount of
thermal energy present in the thermal energy buffer by dividing the
value representing the amount of thermal energy present in the
thermal energy buffer with the total volume of the thermal
buffering medium 2 multiplied with the difference between the
predetermined minimum and maximum temperature.
[0062] Preferably, the thermal energy values comprise a minimal
amount of heating energy representing the amount of energy required
to heat all the thermal buffering medium 2 to a predetermined
minimum temperature, using the heater 4, starting from the amount
of thermal energy present in the thermal energy buffer 10.
[0063] More preferably, the controller 3 calculates the minimal
amount of heating energy by multiplying the difference of the
predetermined minimum temperature and the temperature measured by
the temperature sensors sensing the temperature of the parts 21,
22, 23, 24, 25, 26, 27 containing thermal buffering medium having a
temperature measured by their respective sensors 11, 12, 13, 14,
15, 16, 17 which is lower than the predetermined minimum
temperature within the respective volumes of the parts 21, 22, 23,
24, 25, 26, 27 containing thermal buffering medium 2 having a
temperature measured by their respective sensors 11, 12, 13, 14,
15, 16, 17 which is lower than the predetermined minimum
temperature and adding the resulting values to each other. This is
for example mathematically represented as, where the thermal
buffering medium is water having a heat capacity of 4186 J/(kg
K):
E min = .A-inverted. j ( j : 0 -> n , T j < T min .cndot. )
-> j [ 4.186 V j ( T min - T j ) 3600 ] ##EQU00001## [0064]
wherein: [0065] T.sub.min is a predefined minimum temperature
[0066] n is the number of parts 21, 22, 23, 24, 25, 26, 27 +1
[0067] T.sub.j is the temperature measured by the respective
temperature sensors 11, 12, 13, 14, 15, 16, 17 [0068] V.sub.j is
the volume of the respective parts 21, 22, 23, 24, 25, 26, 27
[0069] Preferably, the thermal energy values comprise a maximal
amount of heating energy representing the amount of energy required
to, using the heater, heat all the thermal buffering medium to a
maximum temperature starting from the amount of thermal energy
present in the thermal energy buffer.
[0070] More preferably, the controller 3 calculates the maximal
amount of heating energy by at least multiplying the difference of
the predetermined maximum temperature and the temperature measured
by the at least one temperature sensor 11, 12, 13, 14, 15, 16, 17
with the respective volume of the part 21, 22, 23, 24, 25, 26, 27
corresponding to the temperature sensor 11, 12, 13, 14, 15, 16, 17
and adding the resulting values to each other. This is for example
mathematically represented as, where the thermal buffering medium
is water having a heat capacity of 4186 J/(kg K):
E max = i = 0 n [ 4.186 V i ( T max - T i ) 3600 ] ##EQU00002##
[0071] wherein in addition to above: [0072] T.sub.max is a
predefined maximum temperature [0073] n is the number of parts 21,
22, 23, 24, 25, 26, 27 +1 [0074] T.sub.i is the temperature
measured by the respective temperature sensors 11, 12, 13, 14, 15,
16, 17 [0075] V.sub.i is the volume of the respective parts 21, 22,
23, 24, 25, 26, 27 [0076] The preferred way of calculating the
amount of thermal energy present in the thermal energy buffer in
such case can be mathematically represented by:
[0076] SoC = .A-inverted. i ( i : 0 -> n ) , .A-inverted. j ( j
: 0 -> n , T j .gtoreq. T min .cndot. ) -> 100 [ j V j ( T j
- T min .cndot. ) i V i ( T max - T min .cndot. ) ] ##EQU00003##
[0077] wherein: [0078] T.sub.min is a predefined minimum
temperature [0079] T.sub.max is a predefined maximum temperature
[0080] n is the number of parts 21, 22, 23, 24, 25, 26, 27 +1
[0081] T.sub.j is the temperature measured by the respective
temperature sensors 11, 12, 13, 14, 15, 16, 17 [0082] V.sub.j or
V.sub.j is the volume of the respective parts 21, 22, 23, 24, 25,
26, 27 [0083] SoC represents the state of charge, representing the
amount of energy present in the thermal energy buffer as a
percentage with respect to the maximum amount of energy present in
the thermal energy buffer with respect to the minimal amount of
heating energy.
[0084] Although in the shown formula, the state of charge is
calculated as a percentage, this is not critical for the invention
and the state of charge can also be calculated as a value between 0
and 1 by leaving out the multiplication by 100. Optionally for
example the SoC.sub.min can be calculated and used as a control
variable. SoC.sub.min is the minimum SoC that must be maintained by
any demand response control system to ensure that hot water is
available to meet users' immediate demands.
[0085] Although the controller 3 can be provided to calculate the
state of charge as described above the state of charge can also be
calculated by the controller 3 by the following mathematical
formula:
SoC = 100 [ 1 - 3600 ( E max - E min .cndot. ) 4.186 ( T max - T
min .cndot. ) V t ] ##EQU00004## [0086] wherein V.sub.t represents
the total volume of the thermal buffering medium and the other
symbols are defined as described above.
[0087] Of course, the other way around it is possible to calculate
the state of charge using the earlier method and to calculate
E.sub.max and E.sub.min using either one of the following
mathematical formula:
E max = E min + 4.186 3600 ( T max - T min .cndot. ) ( 1 - SoC 100
) V t ##EQU00005## E min = E max = 4.186 3600 ( T max - T min
.cndot. ) ( 1 - SoC 100 ) V t ##EQU00005.2##
[0088] Using these thermal energy values, the predetermined energy
values, which can be set by a user according to his preferences,
such as for example corresponding to a "comfort" status, for
example are 35.degree. C.-50.degree. C., preferably 40.degree. C.,
for T.sub.min, 60.degree. C.-90.degree. C., preferably 70.degree.
C., for T.sub.max, 5%-50%, preferably 20%, for the predetermined
minimum amount of energy present in the thermal energy buffer.
[0089] The controller 3 is provided to control a heater 4 of the
thermal buffer 10 in function of the thermal energy values such
that the amount of thermal energy present in the thermal energy
buffer 10 is higher than or equals the predetermined minimum amount
of energy present in the thermal energy buffer 10.
[0090] Preferably, wires 19 interconnecting the different
temperature sensors 11, 12, 13, 14, 15, 16, 17 to the controller
are guided to the outside of the thermal energy buffer 10 at
substantially the respective locations of the temperature sensors
11, 12, 13, 14, 15, 16, 17 and are subsequently connected to the
controller 3, which is schematically shown in FIG. 1.
[0091] Preferably, the heater 4 is positioned below the lowest
temperature sensor 17 as shown in FIG. 1.
[0092] FIG. 2a shows a simulation of the temperature sensed by the
different sensors along height direction of the thermal energy
buffer 10, in this case a water heating unit 18, in function of
time after initially using all heater water contained in the
thermal energy buffer 10 and subsequently heating the newly added
water.
[0093] FIG. 2b shows different thermal energy values such as the
state of charge 28 (%, with the scale shown at the right-hand
side), the E.sub.max 29 (kWh) and the E.sub.min 30 (kWh).
[0094] FIG. 3a shows a simulation of the temperature sensed by the
different sensors along height direction of the thermal energy
buffer 10, in this case a water heating unit 18, in function of
time after initially using all heater water contained in the
thermal energy buffer 10 and subsequently heating the newly added
water. However in this simulation the heater 4 is not situated
below the lowest temperature sensor and it can be observed that a
distorted temperature profile is being measured making it
distorting a the representation of the different thermal energy
values shown in FIG. 3b such as the state of charge 28, the
E.sub.max 29, the E.sub.min 30 and the measured energy.
[0095] The present invention comprises a controller for carrying
out any of the methods of the present invention. In particular the
controller may have a processing engine such as a microprocessor or
an FPGA which is able to execute a program. This program may
include software having code segments which when executed on the
processing engine, are adapted to receive at least one signal
representing at least one thermal energy value related to the
thermal energy buffer, and to calculate an at least one thermal
energy value comprising a predetermined minimum amount of thermal
energy present in the thermal energy buffer and an amount of
thermal energy present in the thermal energy buffer.
The software may be adapted to provide signals to control a heater
of the thermal buffer in function of the thermal energy values such
that the amount of thermal energy present in the thermal energy
buffer is higher than or equals the predetermined minimum amount of
energy present in the thermal energy buffer. The software may also
be adapted to calculate a value representing the amount of thermal
energy present in the thermal energy buffer, whereby the thermal
energy values comprise a minimal amount of heating energy
representing the amount of energy required to, using the heater,
heat all the thermal buffering medium to a predetermined minimum
temperature starting from the amount of thermal energy present in
the thermal energy buffer, and the thermal energy values also
comprise a maximal amount of heating energy representing the amount
of energy required to heat all the thermal buffering medium to a
predetermined maximum temperature, using the heater, starting from
the amount of thermal energy present in the thermal energy buffer.
The software may be adapted to calculate a thermal energy value
that comprises the amount of thermal energy present in the thermal
energy buffer by dividing the value representing the amount of
thermal energy present in the thermal energy buffer with the value
representing the maximum amount of thermal energy stored in the
thermal energy buffer. The value is the State of Charge (SoC). In a
specific embodiment, the controller calculates SOC, i.e. the amount
of thermal energy present in the thermal energy buffer by dividing
the value representing the amount of thermal energy present in the
thermal energy buffer with the total volume of the thermal
buffering medium multiplied with the difference between a
predetermined minimum and maximum temperature. For use with the
software the volume of the thermal buffering medium can be
subdivided in one or more different parts such that the different
parts of the volume of the thermal buffering medium together form
the total thermal buffering medium present in the thermal energy
buffer; and the thermal energy buffer can comprise a respective
temperature sensor for each part for sensing a temperature of the
thermal buffering medium contained in the part. The software can be
adapted to calculate a value representing the amount of thermal
energy present in the thermal energy buffer by multiplying the
temperature measured by the one or more sensors sensing the
temperature of the one or more different parts of the thermal
buffering medium with the volume of the part of thermal buffering
medium such as to obtain at least one value representing the
partial thermal energy contained in the at least one part by the
thermal buffering medium and adding the resulting at least one
partial thermal energy value to each other. The software may be
adapted to calculate the minimal amount of heating energy by
multiplying the difference of the predetermined minimum temperature
and the temperature measured by the one or more temperature sensors
of the one or more parts containing thermal buffering medium having
a temperature measured by their respective sensors which is lower
than the predetermined minimum temperature with the respective
volumes of the parts containing thermal buffering medium having a
temperature measured by their respective sensors which is lower
than the predetermined minimum temperature and adding the resulting
values to each other. The software can be adapted to calculate the
maximal amount of heating energy by at least multiplying the
difference of the predetermined maximum temperature and the
temperature measured by the one or more temperature sensors with
the respective volume of the part corresponding to the temperature
sensor (and adding the resulting values to each other. The software
can be adapted to calculate the amount of thermal energy present in
the thermal energy buffer by only using the parts containing
thermal buffering medium having a temperature measured by their
respective sensor which is higher than or equal to the
predetermined minimum temperature.
[0096] The software may be compiled for a target processing engine
in the controller. Alternatively the software may be written in an
interpretative language such as Java and the controller may include
a processor with an interpreter configured as a virtual
machine.
[0097] The software may be supplied in executable form on a
non-transient signal storage medium such as an optical disk (e.g.
DVD- or CD-ROM), magnetic tape, magnetic disk (diskette, hard
drive), solid state memory (RAM, USB memory stick, solid state
drive).
* * * * *