U.S. patent application number 13/680581 was filed with the patent office on 2013-05-23 for efficiency heating, ventilating, and air conditioning through indirect extension of compressor run times.
This patent application is currently assigned to COOPER TECHNOLOGIES COMPANY. The applicant listed for this patent is Cooper Technologies Company. Invention is credited to Joseph E. Childs, Roger W. Rognli.
Application Number | 20130125572 13/680581 |
Document ID | / |
Family ID | 48425483 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130125572 |
Kind Code |
A1 |
Childs; Joseph E. ; et
al. |
May 23, 2013 |
EFFICIENCY HEATING, VENTILATING, AND AIR CONDITIONING THROUGH
INDIRECT EXTENSION OF COMPRESSOR RUN TIMES
Abstract
A load control device for improving energy efficiency of a
heating, ventilating, and air-conditioning (HVAC) system by
controlling shed times of a compressor of the HVAC system. The load
control device includes a compressor cutoff switch, a sensing
circuit, and a processor. The processor determines a subsequent
mandatory shed time based upon a previous shed time, a previous run
time, and a minimum run time. A subsequent mandatory shed longer
than the previous mandatory shed time causes a subsequent run time
to be increased, thereby increasing system efficiency.
Inventors: |
Childs; Joseph E.; (Golden,
CO) ; Rognli; Roger W.; (Otsego, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cooper Technologies Company; |
Houston |
TX |
US |
|
|
Assignee: |
COOPER TECHNOLOGIES COMPANY
Houston
TX
|
Family ID: |
48425483 |
Appl. No.: |
13/680581 |
Filed: |
November 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61561609 |
Nov 18, 2011 |
|
|
|
Current U.S.
Class: |
62/126 |
Current CPC
Class: |
F24F 11/56 20180101;
F25B 49/022 20130101; F24F 11/62 20180101; F04B 49/065 20130101;
F24F 11/46 20180101; F24F 11/30 20180101 |
Class at
Publication: |
62/126 |
International
Class: |
F25B 49/02 20060101
F25B049/02 |
Claims
1. A load control device for improving energy efficiency of a
heating, ventilating, and air-conditioning (HVAC) system by
controlling shed times of a compressor of the HVAC system, the load
control device comprising: a compressor cutoff switch comprising a
first terminal connectable to a second terminal, the first terminal
adapted to receive a control signal from a temperature control
device of an HVAC system, the second terminal adapted to transmit
the control signal to a device controlling power to a compressor of
an HVAC system, compressor cutoff switch adapted to selectively
cause an electrically-powered compressor of an HVAC system to be
disconnected from a power source by disconnecting the first
terminal from the second terminal and interrupting the transmission
of the control signal to the device controlling power to the
compressor; a sensing circuit in electrical communication with the
second terminal of the compressor cutoff switch, the sensing
circuit configured to detect the presence of the control signal and
transmit a signal representative of the control signal; and a
processor in electrical communication with the sensing circuit and
the compressor cutoff switch, the processor configured to receive
the signal representative of the control signal, to determine a
subsequent mandatory shed time for a subsequent operating cycle of
the compressor based on the run time and the shed time of the
previous operating cycle of the compressor, and to cause the
compressor cutoff switch to disconnect the first terminal from the
second terminal for a period of time substantially equal to the
determined subsequent mandatory shed time of the previous operating
cycle, the period of time following the previous operating
cycle.
2. The load control device of claim 1, wherein the subsequent
mandatory shed time is determined by adding the difference between
a predetermined minimum run time and the run time of the previous
operating cycle to the shed time of the previous operating
cycle.
3. The load control device of claim 1, further comprising a
transceiver, the transceiver configured to receive load control
messages, the load control messages including a command causing the
first terminal to disconnect from the second terminal for a
predetermined load shed time period, thereby causing power to the
compressor to be removed for the predetermined load shed time
period.
4. The load control device of claim 1, wherein the sensing circuit
comprises a trigger sense circuit.
5. The load control device of claim 1, wherein the sensing circuit
comprises a conductive path between the second terminal and the
processor.
6. The load control device of claim 2, wherein the compressor
comprises an air-conditioning compressor used for cooling.
7. The load control device of claim 2, wherein the predetermined
minimum run time is received by the load control device as
transmitted by a master controller over a network.
8. The load control device of claim 2, wherein the predetermined
minimum run time is saved in a memory of the load control device at
or before a time of installation of the load control device.
9. The load control device of claim 1, wherein the processor is
further configured to determine a system efficiency of the HVAC
system.
10. A method of improving efficiency of a
thermostatically-controlled, compressor-based heating or cooling
system by controlling a shed time of the compressor with a
load-control device that includes a compressor cutoff switch, and a
processor, the method comprising: determining a mandatory shed time
of a previous operating cycle of the compressor; measuring a run
time of the previous operating cycle of the compressor; determining
using a processor a mandatory compressor shed time of a subsequent
operating cycle of the compressor, the subsequent operating cycle
occurring after the previous operating cycle and comprising the
subsequent mandatory shed time followed by a subsequent compressor
run time, and the mandatory shed time determined based on the
mandatory shed time of the previous operating cycle, the compressor
run time of the previous operating cycle, and a predetermined
minimum run time; opening a compressor cutoff switch for a period
of time substantially equal to the mandatory shed time of the
subsequent operating cycle; and removing power to the compressor
for at least the period of time substantially equal to the
mandatory shed time of the subsequent operating cycle as a result
of the opening of the compressor cutoff switch, thereby causing the
compressor run time of the subsequent operating cycle to increase
and increasing an energy efficiency of the heating or cooling
system.
11. The method of claim 10, further comprising determining the
minimum compressor run time.
12. The method of claim 10, wherein measuring a run time of the
previous operating cycle of the compressor includes: detecting a
control signal transmitted to a control circuit of the compressor,
the control signal selectively causing the compressor to be
connected to a power source; receiving a signal representing the
control signal at a processor of a load-control device; determining
by the processor a run time of a previous operating cycle of the
compressor based upon the received signal representing the control
signal.
13. The method of claim 10, wherein measuring a run time of the
previous operating cycle of the compressor includes: sensing a
control signal at an output of the compressor cut-off switch;
determining the duration of the control signal at the output of the
compressor cut-off switch, the duration of the control signal at
the output of the compressor cut-off switch being representative of
the previous operating cycle of the compressor.
14. The method of claim 13, wherein sensing a control signal at an
output of the compressor cut-off switch comprises sensing a control
signal at an output of the compressor cut-off switch using a
sensing circuit in electrical communication with the processor and
the output of the compressor cut-off switch.
15. The method of claim 10, wherein determining a mandatory shed
time of a previous operating cycle of the compressor comprises
retrieving an initial mandatory shed time stored in a memory of the
load-control device.
16. A load control device for improving energy efficiency of a
heating, ventilating, and air-conditioning (HVAC) system by
controlling shed times of a compressor of the HVAC system, the load
control device comprising: means for determining a mandatory shed
time of a previous operating cycle of the compressor; means for
measuring a run time of the previous operating cycle of the
compressor; means for determining a mandatory compressor shed time
of a subsequent operating cycle of the compressor, the subsequent
operating cycle occurring after the previous operating cycle and
comprising the subsequent mandatory shed time followed by a
subsequent compressor run time, and the mandatory shed time
determined based on the mandatory shed time of the previous
operating cycle, the compressor run time of the previous operating
cycle, and a predetermined minimum run time; means for opening a
compressor cutoff switch for a period of time substantially equal
to the mandatory shed time of the subsequent operating cycle; and
means for removing power to the compressor for at least the period
of time substantially equal to the mandatory shed time of the
subsequent operating cycle as a result of the opening of the
compressor cutoff switch, thereby causing the compressor run time
of the subsequent operating cycle to increase and increasing an
energy efficiency of the heating or cooling system.
17. The load control device of claim 16, further comprising means
for sensing a duration of a control signal at an output of the
compressor cut-off switch, the duration of the sensed control
signal indicative of a compressor run time.
18. A load control device for improving energy efficiency of a
heating, ventilating, and air-conditioning (HVAC) system by
controlling shed times of a compressor of the HVAC system, the load
control device comprising: a compressor cutoff switch in electrical
communication with a temperature control device of an HVAC system,
compressor cutoff switch adapted to selectively cause an
electrically-powered compressor of an HVAC system to be
disconnected from a power source; a processor in electrical
communication with the compressor cutoff switch, the processor
configured to determine a subsequent mandatory shed time for a
subsequent operating cycle of the compressor based on a
predetermined minimum run time of the compressor, a run time and a
shed time of a previous operating cycle of the compressor, and to
cause the compressor cutoff switch to cause power to the compressor
to be disconnected for a period of time substantially equal to the
determined subsequent mandatory shed time of the previous operating
cycle, the subsequent mandatory shed time being a first period of
time following the previous operating cycle.
19. The load control device of claim 18, further comprising a
sensing circuit in electrical communication with the processor and
configured to detect the presence of a control signal at an output
of the compressor cut-off switch, the control signal requesting
that power be connected to the compressor.
20. The load control device of claim 19, wherein the sensing
circuit comprises a trigger sense circuit.
21. The load control device of claim 18, wherein the subsequent
mandatory shed time is determined by adding a difference between
the predetermined minimum run time and the run time of the previous
operating cycle to the shed time of the previous operating
cycle.
22. The load control device of claim 18, further comprising a
receiver, the receiver configured to receive load control messages,
the load control messages including a command causing power to the
compressor to be removed for a predetermined load shed time
period.
23. The load control device of claim 22, wherein the predetermined
minimum run time is received by the receiver over a long-haul
communications network.
24. The load control device of claim 22, wherein the compressor
comprises an air-conditioning compressor used for cooling.
25. A load control device for determining and selectively improving
energy efficiency of a heating, ventilating, and air-conditioning
(HVAC) by controlling operation of a compressor of the HVAC system,
the load control device comprising: a compressor cutoff switch in
electrical communication with a temperature control device of an
HVAC system, the compressor cutoff switch adapted to selectively
cause an electrically-powered compressor of an HVAC system to be
disconnected from a power source; a processor in electrical
communication with the compressor cutoff switch, the processor
configured to determine a system energy efficiency of the HVAC
system based on run times of operating cycles of the compressor and
a predetermined optimal run time of the compressor, and to
selectively operate the compressor cutoff switch to cause power to
the compressor to be disconnected for a mandatory shed-time period,
thereby causing a run time of the compressor to be extended and
increase the system energy efficiency of the HVAC system.
26. The load control device of claim 25, wherein the mandatory shed
time is longer than a shed time of a previous operating cycle, and
the processor is further configured to cause the cutoff switch to
interrupt transmission of a control signal from the temperature
control device.
Description
RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Application No. 61/561,609 filed Nov. 18, 2011, which
is incorporated herein in its entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to improving energy
efficiency of heating, ventilating, and air-conditioning systems.
More particularly, the present invention relates to systems,
devices, and methods for improving efficiencies of over-sized
heating, ventilating, and air-conditioning systems by controlling
and extending cyclical run times of the systems.
BACKGROUND OF THE INVENTION
[0003] Utilities need to match generation to load, or supply to
demand. Traditionally, this is done on the supply side using
Automation Generation Control (AGC). As loads are added to an
electricity grid and demand rises, utilities increase output of
existing generators to solve increases in demand. To solve the
issue of continuing long-term demand, utilities typically invest in
additional generators and plants to match rising demand. As load
levels fall, generator output to a certain extent may be reduced or
taken off line to match falling demand. As the overall demand for
electricity grows, the cost to add power plants and generation
equipment that serve only to fill peak demand becomes extremely
costly.
[0004] In response to the to the high cost of peaking plants,
electric utility companies have developed solutions and incentives
aimed at reducing both commercial and residential demand for
electricity. In the case of office buildings, factories and other
commercial buildings having relatively large-scale individual
loads, utilities incentivize owners with differential electricity
rates to install locally-controlled load-management systems that
reduce on-site demand. Reduction of any individual large scale
loads by such a load-management systems may significantly impact
overall demand on its connected grid.
[0005] In the case of individual residences having relatively
small-scale electrical loads, utilities incentivize some consumers
to allow them to install demand-response technology at the
residence to control high-usage appliances such as air-conditioning
(AC) compressors, water heaters, pool heaters, and so on. Such
technology aids the utilities in easing demand during sustained
periods of peak usage.
[0006] Traditional demand-response technology used to manage
thermostatically-controlled loads such as AC compressors typically
consists of a demand-response thermostat or a load-control switch
(LCS) device. Such demand-response devices traditionally receive
commands over a long-distance communications network for
controlling the electrical load. A demand-response thermostat
generally controls operation of a load by manipulating space
temperature or other settings to control operation. An LCS device
can be wired into the control circuit of the AC compressor or power
supply line of another electrical load, and thereby interrupts
power to the load when the load is to be controlled.
[0007] Such demand-response thermostats, LCS devices, and other
known demand-response devices are designed to be used with a wide
variety of ducted, thermostatically-controlled heating,
ventilating, and air conditioning (HVAC) systems as commonly used
in single-family residences in the United States. Typical ducted
HVAC systems in the United States utilize distinct and separate
thermostat devices, circulation fan controls, electrical
contactors, switches, and so on, that are easily accessible for
connection to demand-response devices. Further, most control logic
relies on analog control voltages for operation. For example, 24VAC
is commonly used for thermostatic control. As such, demand-response
devices are designed to operate with such systems, and may be
installed into most ducted, thermostatically-controlled HVAC
systems.
[0008] However, while the traditional demand-response schemes
described above shed demand during peak times, especially for
systems utilizing AC units, that demand is often time-delayed and
merely pushed to another time along the utility demand timeline. In
other words, the traditional demand-response schemes are suitable
for reducing peak loads, but don't affect an actual decrease in
energy usage. A key problem lies in the energy consumed by AC units
typically used in thermostatically-controlled HVAC systems. A
majority of the energy consumed by such a system is spent powering
the AC compressor. In a recent Environmental Protection Agency
report, it was reported that air conditioning accounts for 13% of
total home energy expenses on average, and over 20% in hot, humid
regions. This statistic is made more significant by the fact that
AC units are typically used between three to five months per year,
so their effect on the peak demand during summer periods is very
significant.
[0009] The accurate sizing of HVAC equipment, and specifically, the
AC unit, is often quite challenging. Many factors contribute to the
proper sizing of an AC unit, including the angle at which the sun
contacts the home, the type of windows installed in the home, the
interior window shading of the windows, the insulation installed in
the home, the air circulation patterns, the efficiency of the duct
system, and the size of the living space, among others. In
addition, those factors change over time as the home and
landscaping ages. Because those involved with home construction or
AC unit selection, like homeowners and homebuilders, do not want to
undersize an AC unit and have to replace the unit later, AC units
tend to be oversized. Additionally, oversized units typically
provide cooling more quickly, thus avoiding any chance of not
meeting the cooling demand of the occupants.
[0010] However, the oversizing of AC units contributes to the
problem of energy overusage, among other issues. A primary problem
is the short run times of oversized units where the units run for
shorter periods of time than are engineered for optimum operation.
The efficiency of air conditioners is low when first starting, and
increases gradually, reaching peak efficiency in about 10 minutes
for most residential AC units (e.g. long enough for the unit to be
running at optimum efficiency). In addition, even a properly sized
unit will have short run times on days where cooling demand is low.
The problem of AC unit efficiency is illustrated in FIG. 1, a graph
of energy efficiency ratio (EER) as a function of AC unit run
time.
[0011] A number of other problems arise because of short run times.
Relatively short operation times followed by relatively long off
times do not allow the HVAC system to effectively lower humidity
levels. Improperly dehumidified air effects home comfort, reduces
AC cooling efficiency, and can also promote the growth of mold and
mildew indoors. Likewise, short run times decrease overall air
circulation, resulting in repercussions on air quality and home
comfort. Short run times also increase wear and tear on HVAC
systems. Problems like dirty filters, leaky ducts, and improper
refrigerant are often masked by oversized units. These problems can
increase the amount and magnitude of maintenance required by AC
units and can potentially shorten the operable life of the units.
And, perhaps most importantly, short run times cost homeowners and
commercial building owners additional money to operate, as the
units are not operating at peak efficiency.
[0012] One attempt at improving the energy-efficiency
characteristics of HVAC systems relies on variable speed AC unit
compressors and fans that may be used to increase system turndown.
However, such technology remains relatively expensive for new HVAC
systems. Further, retrofitting existing, working HVAC systems to
replace "single-speed" technology with variable-speed technology
does not provide a convenient nor cost-effective solution for
improving energy efficiency.
[0013] Another attempt at improving AC system efficiency is
described in U.S. Pat. No. 5,960,639 to Hammer, entitled "Apparatus
for Regulating Compressor Cycles to Improve Air
Conditioning/Refrigeration Unit Efficiency". Hammer discloses
methods and systems for addressing compressor short-cycling.
Short-cycling occurs when the time between a compressor stopping
and restarting is so short that coolant pressures within the HVAC
system do not have time to equalize, and the compressor does not
have time to cool. Such conditions may occur in undersized HVAC
systems, and result in decreased system efficiency. While the
invention disclosed by Hammer addresses inefficiencies for systems
experiencing short-cycling, often in undersized units or on peak
usage days, Hammer fails to address the energy inefficiencies
caused by short run times (as opposed to short off times) occurring
in oversized AC systems.
[0014] Thus, there remains a need for a solution that reduces
energy usage of oversized compressor-based HVAC systems in
residential or even commercial buildings.
SUMMARY OF THE INVENTION
[0015] In an embodiment, the present invention comprises a load
control device for improving energy efficiency of a heating,
ventilating, and air-conditioning (HVAC) system by controlling shed
times of a compressor of the HVAC system. The load control device
comprises: a compressor cutoff switch comprising a first terminal
connectable to a second terminal, the first terminal adapted to
receive a control signal from a temperature control device of an
HVAC system, the second terminal adapted to transmit the control
signal to a device that controls the on/off signal to a compressor
of an HVAC system, compressor cutoff switch adapted to selectively
cause an electrically-powered compressor of an HVAC system to be
disconnected from a power source by disconnecting the first
terminal from the second terminal and interrupting the transmission
of the control signal to the device controlling power to the
compressor; a sensing circuit in electrical communication with the
second terminal of the compressor cutoff switch, the sensing
circuit configured to detect the presence of the control signal and
transmit a signal representative of the control signal; and a
processor in electrical communication with the sensing circuit and
the compressor cutoff switch, the processor configured to receive
the signal representative of the control signal, to determine a
subsequent mandatory shed time for a subsequent operating cycle of
the compressor based on the run time and the shed time of the
previous operating cycle of the compressor, and to cause the
compressor cutoff switch to disconnect the first terminal from the
second terminal for a period of time substantially equal to the
determined subsequent mandatory shed time of the previous operating
cycle, the period of time following the previous operating
cycle.
[0016] In another embodiment, the present invention comprises a
method of improving efficiency of a thermostatically-controlled,
compressor-based heating or cooling system by controlling a shed
time of the compressor with a load-control device that includes a
compressor cutoff switch, a sensing circuit. The method includes
the steps of determining a mandatory shed time of a previous
operating cycle of the compressor; measuring a run time of the
previous operating cycle of the compressor; determining using a
processor a mandatory compressor shed time of a subsequent
operating cycle of the compressor, the subsequent operating cycle
occurring after the previous operating cycle and comprising the
subsequent mandatory shed time followed by a subsequent compressor
run time, and the mandatory shed time determined based on the
mandatory shed time of the previous operating cycle, the compressor
run time of the previous operating cycle, and a predetermined
minimum run time; opening a compressor cutoff switch for a period
of time substantially equal to the mandatory shed time of the
subsequent operating cycle; removing power to the compressor for at
least the period of time substantially equal to the mandatory shed
time of the subsequent operating cycle as a result of the opening
of the compressor cutoff switch, thereby causing the compressor run
time of the subsequent operating cycle to increase and increasing
an energy efficiency of the heating or cooling system.
[0017] In another embodiment, the claimed invention comprises a
load control device for improving energy efficiency of a heating,
ventilating, and air-conditioning (HVAC) system by controlling shed
times of a compressor of the HVAC system. The load control device
includes: means for determining a mandatory shed time of a previous
operating cycle of the compressor; means for measuring a run time
of the previous operating cycle of the compressor; means for
determining a mandatory compressor shed time of a subsequent
operating cycle of the compressor, the subsequent operating cycle
occurring after the previous operating cycle and comprising the
subsequent mandatory shed time followed by a subsequent compressor
run time, and the mandatory shed time determined based on the
mandatory shed time of the previous operating cycle, the compressor
run time of the previous operating cycle, and a predetermined
minimum run time; means for opening a compressor cutoff switch for
a period of time substantially equal to the mandatory shed time of
the subsequent operating cycle; and means for removing power to the
compressor for at least the period of time substantially equal to
the mandatory shed time of the subsequent operating cycle as a
result of the opening of the compressor cutoff switch, thereby
causing the compressor run time of the subsequent operating cycle
to increase and increasing an energy efficiency of the heating or
cooling system.
[0018] In another embodiment, the claimed invention comprises a
load control device for improving energy efficiency of a heating,
ventilating, and air-conditioning (HVAC) system by controlling shed
times of a compressor of the HVAC system. The load control device
includes: a compressor cutoff switch in electrical communication
with a temperature control device of an HVAC system, compressor
cutoff switch adapted to selectively cause an electrically-powered
compressor of an HVAC system to be disconnected from a power
source; and a processor in electrical communication with the
compressor cutoff switch, the processor configured to determine a
subsequent mandatory shed time for a subsequent operating cycle of
the compressor based on a predetermined minimum run time of the
compressor, a run time and a shed time of a previous operating
cycle of the compressor, and to cause the compressor cutoff switch
to cause power to the compressor to be disconnected for a period of
time substantially equal to the determined subsequent mandatory
shed time of the previous operating cycle, the subsequent mandatory
shed time being a first period of time following the previous
operating cycle.
[0019] While the disclosure herein is focused generally on AC units
and specifically, controlling AC compressors, one skilled in the
art will appreciate that the embodiments described are applicable
to many other areas as well, such as a heat pump system, and can be
used for any compressor-based system. For example, air conditioning
compressors for indoor space management, heating compressors for
indoor space management, and pool heating compressors, among
others.
[0020] Embodiments of the present invention as described above
provide a number of features and benefits. In embodiments, as
described above, the AC unit compressor run time is increased
toward or to the optimum run time by introducing a variable
mandatory shed time after the completion of every "on" cycle.
Because the AC unit compressor run time is increased, efficiency is
necessarily increased, as is evident by the efficiency slope of the
graph of FIG. 1. Increased efficiency therefore allows for the
feature and advantage of improved comfort in the conditioned space.
When conditioned air is supplied over a longer period of time, the
conditioned air is allowed to gradually mix into the space, thus
reducing cold drafts near the supply registers. A less drastic and
more consistent level of comfort throughout the conditioned space
is therefore provided.
[0021] Increased efficiency also allows for the feature and
advantage of better humidity control. In order for air conditioners
to dehumidify or dry the air, they have to cycle long enough for
moisture to condense on the coils and drain away. When AC units
have short run times, the amount of condensation that drains off
the coils is reduced and can even allow some moisture to evaporate
back into the air. In contrast, in embodiments of the invention,
run time is increased, thereby allowing on cycles long enough to
effectively dehumidify the air. As a result, comfort is increased
and the risk of mold growth and indoor mildew growth is
reduced.
[0022] Additionally, increased efficiency allows for the feature
and advantage of fewer maintenance problems for the AC unit and
HVAC system. Longer run cycles typically expose problems typically
hidden by units running with short run times like dirty filters,
leaky ducts, and improper refrigerant charge. Therefore,
maintenance costs are reduced by spotting maintenance problems
properly.
[0023] Perhaps most importantly for the individual homeowner,
increased efficiency allows for the feature and advantage of lower
utility bills. As longer run cycles necessarily increase AC unit
efficiency (again, see FIG. 1, less energy is consumed by the
compressor and thus, the entire HVAC system to control the
temperature of the homeowner's space. Thus, utility bills are
likewise decreased, as the homeowner no longer pays for excess
energy consumed by system inefficiencies.
[0024] Another feature and advantage of the various embodiments of
the present invention is that demand is reduced during peak load
times. In an embodiment, the present invention comprises a
load-control device (LCD) configured to receive commands over a
long-distance communications network from a controlling utility and
subsequently act on these commands to interrupt power to the load
when the load is to be controlled. As individual LCSs can be
installed at numerous locations having both large-scale individual
loads and small-scale individual loads, utility load can be very
precisely controlled.
[0025] Another feature and advantage of the various embodiments of
the present invention is the ability to adapt to changing weather
conditions. Because of the iterative algorithm implemented by
embodiments of the invention, the run times of the compressor are
automatically adjusted for day-to-day temperature differences, and
even day-to-night differences. Further, no additional shed time set
points need to be defined, and nothing further needs to be
programmed by the utility, customer, or HVAC technician after the
initial installation. The iterative algorithm is defined to account
for the differences in temperature experienced by an interior space
to be cooled, and is defined so that further maintenance or
involvement is limited.
[0026] Another feature and advantage of the various embodiments of
the present invention is that the methods implemented by
embodiments are suitable for use not only in systems having LCSs
for receiving commands from a remote utility, but are also
appropriate for local use by individual homeowners. For example, a
homeowner can utilize embodiments of the invention to simply
increase the efficiency of his existing HVAC system, thereby
receiving all of the benefits described above with respect to
embodiments implemented to control peak load.
[0027] The above summary of the invention is not intended to
describe each illustrated embodiment or every implementation of the
present invention. The figures and the detailed description that
follow more particularly exemplify these embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The invention may be more completely understood in
consideration of the following detailed description of various
embodiments of the invention in connection with the accompanying
drawings, in which:
[0029] FIG. 1 is a graph of efficiency versus run time for an
exemplary, theoretical air-conditioning system;
[0030] FIG. 2 is a diagram of a facility receiving electricity
through an electrical-distribution network and having a heating,
ventilating, and air conditioning (HVAC) system with a load control
switch (LCS) device, according to an embodiment;
[0031] FIG. 3 is a block diagram of a portion of the HVAC system
with the LCD device of FIG. 2 in a commanded-off mode, according to
an embodiment;
[0032] FIG. 4 is a flowchart of operation of a demand-response load
control system according to an embodiment;
[0033] FIG. 5 is a flowchart of an algorithm implemented by an LCD
according to an embodiment; and
[0034] FIG. 6 is a flowchart of an algorithm for determining a
system efficiency.
[0035] While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
[0036] Referring to FIG. 2, a demand-response load control system
100 is depicted according to an embodiment. Demand-response load
control system 100 generally includes master station 102,
electrical power generator 104, electrical distribution network
106, long-distance/long-haul communications network 108, and one or
more facilities 110. Demand-response load control system 100
generally operates in tandem with improved heating, ventilating,
and air conditioning (HVAC) system 112, which can be located a
facility 110 in an embodiment. Though the term "HVAC" is generally
understood to mean "heating, ventilating, and air conditioning", it
will be understood that improved-efficiency HVAC system 112 may
comprise heating and cooling capability, just cooling capability,
or just heating capability. As such, when specific reference is
made to a cooling configuration and operation, it will be
understood that the same configuration and operation may exist and
operate as a heating configuration and operation.
[0037] Master station 102 can comprise the utility or power company
headquarters, in an embodiment. Master station 102 can originate
signals or commands relating to energy load in order to control the
energy load demanded by the aggregation of the demand of individual
facilities 110. In an embodiment, master station 102 contains
electrical power generator 104.
[0038] Electrical power generator 104 is contained within master
station 102 in an embodiment, or, in another embodiment, is not
contained within master station 102 but is under the direction of
master station 102. Electrical power generator 104 comprises the
source of electrical energy for system 100. Electrical power
generator 104 therefore includes electricity generation equipment
such that electricity can be generated by electricity generation
equipment.
[0039] Electrical distribution network 106 is configured to carry
electricity from electrical power generator 104 at master station
102 to appropriate facilities 110. In an embodiment, electrical
distribution network 106 generally comprises power lines.
Electrical distribution network 106 can further comprise
substations, pole-mounted transformers, and distribution
wiring.
[0040] Long-distance/long-haul communications network 108 is
configured to carry the signals or commands originated by master
station 102 to the appropriate component or components within
individual facilities 110 to effect one-way communication. In
another embodiment, communications network 108 is configured to
carry signals from the appropriate component or components of
facilities 110 back to master station 102 to effect two-way
communication.
[0041] The invention can be implemented with such long-haul one-way
and two-way communication interfaces or protocols that include, but
are not limited to, 900 MHz FLEX one-way paging, Sensus Flexnet,
Cellnet, IEEE 802.15.4, AERIS/TELEMETRIC Analog Cellular Control
Channel two-way communication, SMS Digital two-way communication,
or DNP Serial compliant communications for integration with
SCADA/EMS communications currently in use by electric generation
utilities. Other short-haul wired or wireless communications
protocols may be employed, including, but not limited to,
ZigBee.RTM., Bluetooth.RTM., WiFi.RTM., and others.
[0042] Facility 110, as depicted in FIG. 2, is a residential home
having an interior space requiring heating or cooling. Facility 110
can also be a commercial building, industrial building, or any such
building or structure having an interior space requiring heating or
cooling. Facility 110 generally houses the components of
improved-efficiency HVAC system 112.
[0043] In general operation of the electricity generation and
transmission components, electricity is generated by electrical
power generator 104 at master station 102 and transferred to
facilities 110 via electrical distribution network 106. Actual
electricity consumption at any individual facility 110 may be
measured by electricity meter 114.
[0044] Electricity meter 114 may be a standard non-communicative
device, or may be a "smart meter" tied into an Advanced Meter
Infrastructure (AMI) or an electricity "smart grid", capable of
communicating with master station 102 over long-haul communication
network 108 and in some cases capable of communicating with local
devices a short-haul communication network (not depicted) at or
near facility 110. Electricity meter 114, as depicted in FIG. 2, is
connected to electrical distribution network 106 and one or more
components of improved-efficiency HVAC system 102.
[0045] Improved-efficiency HVAC system 102 includes temperature
control device 116, load control device (LCD) 118, outdoor unit
120, and forced air unit (FAU) 122. In an embodiment, as depicted,
temperature control device 116 is in electrical communication with
LCD 118 and FAU 122. LCD 118 is further in electrical communication
with outdoor unit 120.
[0046] Temperature control device 116 may be any of a number of
known temperature control devices or thermostats used to regulate a
temperature of a space within facility 110. As such, temperature
control device 116 may be programmable, non-programmable, digital,
mechanical, communicative, and so on. Thermostat 104 may operate on
24VAC, line voltage, or another voltage as needed.
[0047] Outdoor unit 120 in an embodiment is a condensing unit of an
air-conditioning system or HVAC system 112. Outdoor unit 120
includes compressor 124, and as understood by those skilled in the
art, generally includes a heat exchanger with condensing coils, a
fan, valving, electrical components including a compressor
contactor, and so on. Although generally referred to an "outdoor"
unit, it will be understood that although condensing units and
other such units of an HVAC system are typically located at an
exterior of a building, such as facility 110, unit 120 could in
some embodiments be located inside facility 110. Further, it will
also be understood that while outdoor unit 120 may comprise a
condensing unit of an air-conditioning system designed for cooling,
outdoor unit 120 may also be a unit of a heat-pump or other such
system, providing heating, rather than cooling.
[0048] FAU 122 includes circulation fan 126, and may also include
electrical control circuitry having several electrical terminals,
as discussed further below. FAU 122 may be any of several known
types of forced air units used to condition and circulate air. FAU
122 may also include heating and cooling elements, filters,
dampers, and other related HVAC equipment not depicted. FAU 122 and
circulation fan 126 may be connected to ductwork for distributing
conditioned air to all or portions of facility 110.
[0049] Circulation fan 126 in an embodiment may be a single-speed
electric fan located within FAU 122, and turned on and off to move
air through facility 110. In other embodiments, circulation fan 126
may be a variable-speed or adjustable-speed fan controlled to vary
the rotation speed of the fan, and hence the air volume output of
the fan.
[0050] Load-control device (LCD) 118, as described further below,
in an embodiment may comprise a load-control switch (LCS) which
receives signals or commands from master station 102 by way of
long-distance/long-haul communications network 108 to interrupt
compressor 124 of outdoor unit 120 in order to reduce energy
demand, even when temperature control device 116 calls for run
operation. In another embodiment, LCD 118 may receive signals or
commands over a short-haul network. In yet another embodiment LCD
118 operates locally without receiving external communications.
[0051] Further, it will be understood that when compressor 124 is
interrupted, circulation fan 126 can and will often still run.
[0052] In general operation without interruption from LCD 118 and
master station 102, air is heated or cooled by HVAC system 112, and
forced through a network of air ducts by circulation fan 126. Based
upon a temperature set point at temperature control device 116,
temperature control device 116 calls for heating or cooling based
on feedback from a temperature sensor within the conditioned space
of facility 110. In the case of cooling, temperature control device
116 signals compressor 124 to turn on, and for circulation fan 126
to circulate cooled air through the ductwork to various points
about facility 110. The duration of time that compressor 124 is
powered and runs may generally be considered the compressor "run
time". When a temperature set point is reached, temperature control
device 116 ceases signaling compressor 124 and fan 126 to run, and
power is removed from compressor 124. The duration of time that
compressor 124 is not powered, or is off, before restarting may
generally be considered the compressor "off time", or "shed time".
As explained further below, the "shed time" may be determined
solely on the basis of the on-off control of compressor 124 by
temperature control device 116 as temperature control device 116
seeks to hold a constant space temperature ("natural" shed time),
or may be determined wholly or in part by control of compressor 124
by LCD 118 ("mandatory" shed time). A single compressor 122 cycle
comprises an off/shed time followed by a run time. When the space
temperature rises, temperature control device 116 again calls for
cool, and the process repeats.
[0053] Referring again to FIG. 1, an efficiency versus run time
chart for an exemplary HVAC system is depicted. The vertical axis
of the chart represents a range of system energy efficiency ratings
(EER) ranging from "Min" for minimum efficiency to "Max" for
maximum efficiency. The horizontal axis of the chart represents
system run time in minutes. In this depicted example chart, energy
efficiency ranges from 0 to 7 EER, while time ranges from 0 to 10
minutes.
[0054] Three points, Point A, Point B, and Point C are also
depicted on the EER vs. Run Time chart of FIG. 1. At Point A, after
1 minute, the system efficiency rating is 3 EER; at Point B, after
running 5 minutes, the system efficiency has improved to 6 EER; and
at Point C, after running 9 minutes, which may be considered an
optimal amount of time, or T.sub.OPT, system efficiency is
essentially maximized at 7 EER.
[0055] Although the depicted EER v. Run Time chart is only an
example of performance of a particular theoretical HVAC system, the
chart illustrates the general concept that when a compressor-based
HVAC system begins to operate, system efficiency may be rather low,
then, after some time has passed, energy efficiency increases
non-linearly to its maximum after a period of time.
[0056] In the graph depicted in FIG. 1, at time t=9 minutes, system
energy efficiency is maximized. Such a time is referred to as
T.sub.OPT. For the portion of time that HVAC system runs beyond
T.sub.OPT, 9 minutes for the example depicted in the chart of FIG.
1, the system will generally operate at maximum system
efficiency.
[0057] Consequently, in an HVAC system where a compressor is
regularly cycled on and off, such as improved-efficiency HVAC
system 112, it is generally desirable to size and operate the
system such that the system runs for at least a minimum run time
T.sub.MIN which may be equal to, or greater than T.sub.OPT, so as
to maximize energy efficiency. Alternatively, T.sub.MIN may be less
than T.sub.OPT, resulting in an efficiency below a maximum
efficiency. As explained further below, in such a case T.sub.MIN
will result in an improved efficiency, though the efficiency will
not be Optimum.
[0058] However, in an oversized system, one with excess cooling or
heating capacity, the system can run for significantly less time
than T.sub.OPT. LCD 118 provides a solution for improving the
efficiency of such an oversized HVAC system by extending compressor
124 off time to thereby subsequently increase compressor 124 run
time such that run time T.sub.MIN approaches or exceeds
T.sub.OPT.
[0059] Referring to FIG. 3, a block diagram of a portion of HVAC
system 112 is depicted according to an embodiment. The portion
depicted includes temperature control device 116, LCD 118, and
compressor 124, as well as cooling contactor 144.
[0060] Temperature control device 116 comprises call-for-fan output
signal 128 and call-for-cool output signal 130. Call-for-fan output
signal 128 is electrically connected to FAU 122. Call-for-cool
signal is electrically connected to LCD 118, and specifically,
compressor cutoff relay 140, described further below.
[0061] LCD 118 generally includes, according to the embodiment of
FIG. 3, processor 132, memory 134, optional radio transceiver 136,
power supply 138, compressor cutoff switch 140, monitoring line 142
and sensing circuit 145.
[0062] Processor 132 can comprise a microprocessor,
microcontroller, microcomputer, and any other such processing
device. Processor 132 can comprise a central processing unit,
microprocessor, microcontroller, microcomputer, or other such known
computer processor. Processor 132 is in communication with memory
134, radio transceiver 136, power supply 138, and compressor cutoff
switch 140. Further, processor 132 is connected with the line
controlled by compressor cutoff switch 140 via monitoring line
142.
[0063] Memory 134, which may be a separate memory device or memory
device integrated into processor 132, may comprise various types of
volatile memory, including RAM, DRAM, SRAM, and so on, as well as
non-volatile memory, including ROM, PROM, EPROM, EEPROM, Flash, and
so on. Memory 134 may store programs, software, and instructions
relating to the operation of LCD 118.
[0064] Radio transceiver 136 receives the signals or commands
originated by master station 102. In an embodiment, radio
transceiver 136 thus allows for one-way communication from the
outside world to LCD 118. In such an embodiment, radio transceiver
136 may be considered a radio receiver. In another embodiment,
radio transceiver 136 can originate signals for receipt by master
station 102 or any other component along long-distance/long-haul
communications network 108. In such an embodiment, radio
transceiver 136 thus allows for two-way communication between the
outside world and LCD 118.
[0065] Power supply 138, receives power from an external power
source, such as from FAU 122, and as understood by those skilled in
the art, conditions the power to provide an appropriate power to
processor 132, radio transceiver 136, and other components of LCD
118 as needed. In an embodiment, power supply 138 receives a 24VAC
power from FAU 122. In other embodiments, power supply 138 may
receive a 120VAC or other such power as is locally available.
[0066] Compressor cutoff switch 140 comprises an electrically
operated switch, which in an embodiment comprises a relay, such as
a normally-closed single-pole, double throw relay switch.
Compressor cutoff switch 140 may also comprise other types of
switching devices, in addition to any of various types of known
relays. Compressor cutoff switch 140 as depicted includes first
terminal 141a and second terminal 141b. When compressor cutoff
switch 140 is closed, first terminal 141a and second terminal 141b
are electrically connected, such that control line COOL is
electrically connected to cooling contactor 144 via control line
143. Compressor cutoff switch 140 is driven by a control signal
received from processor 132. In an embodiment, LCD 118 also
includes a relay driver (not shown) intermediate processor 132 and
compressor cutoff switch 140 such that the relay driver receives
the control signal from processor 132 and drives switch 140 to open
or close.
[0067] Monitoring line 142 is connected to control line 143.
Monitoring line 142 connects control line 143 to processor 132,
such that processor 132 can monitor the control line 143 voltage to
determine whether call-for-cool output 130 has been commanded and
is operative. In an embodiment, sensing circuit 145 may be located
between processor 132 and control line 143. In an embodiment,
monitoring line 142 is positioned subsequent to compressor cutoff
switch 140. In such an embodiment, the logic of processor 132 is
reduced in determining whether call-for-cool output 130 is
commanded and operative with respect to compressor cutoff switch
140, as the line can merely be monitored after compressor cutoff
switch 140, instead of a case where the line is monitored prior to
compressor cutoff switch 140, whereby both the state of compressor
cutoff switch 140 and call-for-cool output 130 would need to be
monitored and then acted on. In an embodiment, processor 132
samples the voltage of control line 143 between call-for-cool
output 130 and cooling contactor 144 every 5 seconds. Other
monitoring algorithms utilizing monitoring line 142 can also be
implemented.
[0068] In an embodiment, LCD 118 may include sensing circuit 145 in
communication with control line 142, monitoring line 143, and
processor 132. Such a sensing circuit may sense the absence or
presence of a voltage or current signal by sampling control line
143 at a predetermined sampling frequency f.sub.s. In an
embodiment, a sensing circuit may comprise a Schmitt trigger that
senses voltage, or a current sensor that senses current flow in
control line 143. In other simplified embodiments, sensing circuit
145 may not be present, or may merely comprise an electrical
connection between processor 132 and control line 143, i.e.,
monitoring line 142.
[0069] Cooling contactor 144, in an embodiment, is a contactor
relay or other similar switch that switches line voltage to
compressor 124 on and off based on a received control signal, such
as COOL. Contactor 144 may be one of many known contactors or other
known controlling devices for switching the power of compressor
124, wherein compressor 124 may be an air-conditioning compressor,
heat pump, or other such compressor of a heating or cooling
circuit. Contactor 144 may operate on alternating current (AC) or
direct current (DC), and at a control circuit voltage appropriate
for the particular control circuit, such as 24VAC.
[0070] In operation generally where compressor cutoff switch 140 is
in a closed position such that first terminal 141a and second
terminal 141b are connected, and the line between call-for-cool
output 130 and cooling contactor 144 is uninterrupted, temperature
control device 116 is allowed to directly control the operation of
compressor 124. In the case where cooling is desired, temperature
control device 116 places an appropriate voltage on call-for-cool
output 130. Cooling contactor 144, upon receiving the call-for-cool
signal 130 from temperature control device 116 switches line
voltage on to compressor 124. Thus, cooling is commanded and
implemented by cooling contactor 144 through compressor 124. Note
that the aforementioned operation is how a typical HVAC system
would operate without an LCD 118.
[0071] In operation wherein a remote, commanding master station 102
implements load controls, compressor cutoff switch 140 can be, most
basically, commanded open or closed. Referring to FIG. 4, master
station 102 originates a load control signal at 146. Master station
102 transfers the signal to long-distance/long-haul communications
network 108 at 148. Long-distance/long-haul communications network
108 subsequently conveys the signal to individual facilities 110,
and specifically, to radio transceiver 136 of LCD 118 at 150. After
receipt by radio transceiver 136 of the signal of master station
102, the signal is communicated to processor 136 so that processor
136 can interpret the signal and subsequently act on compressor
cutoff switch 140 at 152. As described above, most basically, LCD
118 can command compressor cutoff switch 140 to be closed or
opened. In the case where compressor cutoff switch 140 remains in
its normal closed position, HVAC system 112 operates as described
above wherein the line between call-for-cool output 130 and cooling
contactor 144 is uninterrupted. If, however, master station 102
signal to facilities 110 is to lessen demand on the utility,
compressor cutoff switch 140 can be commanded open. The line
between call-for-cool output 130 and cooling contactor 144 is then
broken such that temperature control device 116 signals to cooling
contactor 144 are not received. Thus, compressor 124 does not run
when it normally would have and energy demand is lessened.
[0072] As such, LCD 118 may implement a variety of load-shedding
and load-control algorithms, including known algorithms, such as
those described in U.S. Pat. Nos. 7,355,301, 7,242,114, 7,702,424,
and 7,528,503, 7,869,904, assigned to the assignees of the present
invention, and herein incorporated by reference in their
entireties.
[0073] However, while such operation reduces overall energy load,
such operation does not necessarily address or improve, energy
efficiency. To improve energy efficiency, LCD 118 can implement
various compressor run time algorithms that result in longer run
times of compressors. Such algorithms can be commanded by master
station 102, transmitted via long-distance/long-haul communications
network 108, received by radio transceiver 136 and subsequently
stored in memory 134 by processor 132 and ultimately implemented by
processor 132. Alternatively, such algorithms may be preprogrammed
and stored in LCD 118 on site, or prior to installation.
[0074] In one such energy-saving embodiment, run time of compressor
122 is extended by manipulating the off time, or shed time of
compressor 122. As explained further below, LCD 118 implements a
mandatory shed time based on a preceding mandatory shed time and a
preceding measured run time such that a subsequent run time will
generally be longer than the preceding measured run time. In one
embodiment, a mandatory compressor shed time duration, S(x), is
determined as follows:
S(x)=S(x-1)+T-R(x-1), EQN. 1:
Where x represents a particular cycle in a sequence of cycles,
e.g., x=1 represents a first cycle, x=2 represents a second,
subsequent cycle, and so on, and wherein each cycle comprises a
mandatory shed time duration followed by a run time duration;
S(x-1) is the mandatory shed time duration of the previous cycle; T
is the duration of a minimum preferred compressor run time, and
R(x-1) is the measured duration of the run time of the (x-1).sup.th
cycle. For the sake of understanding, S(x) may also be referred to
as the "present" mandatory shed time duration to distinguish from a
previous mandatory shed time duration S(x-1).
[0075] As such, Equation 1 provides that a mandatory shed time
duration is determined to be substantially equal to the previous
mandatory shed time plus the difference between the minimum
preferred compressor run time and the measured previous run time.
In an embodiment, run time durations R will be measured or
estimated run time durations, while mandatory shed times S will be
predetermined durations (based on the above algorithm), rather than
measured durations.
[0076] In a theoretical example comprising five compressor cycles,
an operating sequence of the five compressor cycles may be
described as (S1, R1), (S2, R2), (S3, R3), (S4, R4), and (S5, R5).
The first cycle, x=1, comprises mandatory shed time S1 followed by
run time R1, the second cycle, x=2, comprises mandatory shed time
S2 followed by run time R2, and so on. In such a sequence,
mandatory shed time S2 is determined by the previous shed and run
time durations, mandatory shed time S1 and run time R1.
[0077] As evident by Equation 1, mandatory shed time duration S(x)
will be longer than the previous mandatory shed time duration
S(x-1) when the previous run time R(x-1) is less than the minimum
run time T. The result of the increase in mandatory shed time
duration S(x) is to cause subsequent run time R(x), R(x+1), and so
on, to generally increase in duration, even though compressor run
times R(x) are not directly controlled by LCD 118. Subsequent run
time durations R(x) tend to increase due to an increased
incremental load on compressor 124. The incremental load on
compressor 124 is caused by a space temperature falling further
below a temperature set point than would normally have been allowed
by temperature control device 116. For example, temperature control
device 116 might normally call for cool after a temperature rises
0.5 degrees above a temperature set point, and after a 6 minute off
time or shed time duration. When the shed time duration is extended
from the "natural" shed time of 6 minutes, to a mandatory shed time
S(x) of, for example, 9 minutes, as implemented by LCD 118, a space
temperature might rise to 0.8 degrees above the desired temperature
set point thereby causing compressor 124 to run for a longer
subsequent period of time, R(x).
[0078] Referring to FIG. 5, a flowchart of the above
energy-efficiency improving algorithm implemented by LCD 118 is
depicted. The algorithm illustrated is implemented upon
installation of LCD 118 into a facility 110, or upon the
transmission of the specific algorithm to LCD 118 by master station
102, or as is appropriate. The algorithm may be stored in a
non-transitory memory device, such as memory 134, or another such
memory device (see also FIG. 3).
[0079] The utility, homeowner, HVAC technician, processor 132, or
other entity determines minimum run time T at 154, which may be
stored in memory 134. In one embodiment, minimum run time T may be
derived from a system efficiency chart similar to the one depicted
in FIG. 1. In an embodiment, minimum run time T may be set to
maximize system efficiency. For example, T=9 minutes (referring to
the exemplary system efficiency depicted in FIG. 1). In other
embodiments, T may be determined and set based upon a minimum run
time that does not necessarily maximize system efficiency, but
merely improves compressor and system efficiency, for example, T=6
minutes (again referring to the exemplary system efficiency
depicted in FIG. 1).
[0080] In another embodiment, T may be set to exceed the time
required to maximize system efficiency, for example, T=12 minutes
(again referring to the exemplary system efficiency depicted in
FIG. 1). The operating characteristics of the system of FIG. 1 are
based on an assumed set of climatic conditions or other influencing
factors. Weather changes, solar radiation, elevation, humidity, and
so on affect the actual characteristics. Having a minimum run time
T above a run time that theoretically corresponds to a maximum run
time makes it more likely that a maximum system efficiency will be
met, especially under changing climatic conditions.
[0081] Other methods and criteria may be used or considered to
determine an appropriate minimum run time T. Such criteria may
include maximum humidity levels (implies longer minimum run times),
measured or perceived temperature variation at facility 110,
compressor manufacturer recommended minimum run times, and so
on.
[0082] The previous mandatory shed time duration S(x-1) is
retrieved at 156. In an embodiment, S(x-1) is a calculated value
stored in memory 134, such that it is not necessary to measure
and/or store actual measurements of shed time durations of
compressor 124. In the case where the algorithm is being executed
in the first instance and thus there is no previous shed time
duration, the value of S(x-1) may be set to a default of zero. In
other embodiments, an initial default value of S(x-1) may be
non-zero, such as S(x-1) being set equal to a previous known
mandatory shed time, or an estimated previous known mandatory shed
time. However, upon all subsequent iterations, a previous mandatory
shed time is available and thus factors in to the adaptability of
the algorithm to account for changes in temperature from day-to-day
and within days, as well.
[0083] At 158, the previous run time R(x-1) is determined. In an
embodiment, according to FIG. 3, processor 132 determines the
previous run time duration based on data sampled at monitoring line
142 or control line 143, which may be via sensing circuit 145.
[0084] It will be understood that steps 156 and 158 may be
interchanged, such that a determination of a previous run time
R(x-1) is made prior to a determination or retrieval of previous
mandatory shed time S(x-1), as both are required for determining a
new or present mandatory shed time S(x).
[0085] A new mandatory shed time, S(x) can then be calculated at
160 by processor 132 according to the above Equation 1.
[0086] Referring also to FIG. 3, at step 162, processor 132 causes
compressor cutoff switch 140 to open, thereby starting the new
mandatory shed time period. If temperature control device 116 was
calling for cool, power to compressor 124 would be removed via
cooling contactor 140. If temperature control device 116 was not
calling for cool, cooling contactor 150 would remain open, such
that power remained off at compressor 124.
[0087] At step 164, if the new mandatory shed time S(x) is not
expired, at step 166, compressor cutoff switch 140 remains open,
and compressor 124 is not powered, regardless of whether
temperature control device 116 calls for cool.
[0088] At step 164, when mandatory shed time S(x) expires, at step
168, processor 132 causes compressor cutoff switch 140 to close. If
temperature control device 116 is calling for cool, upon the
closure of compressor cutoff switch 140, cooling contactor 144 will
cause power to be applied to compressor 124, causing compressor 124
to begin to run, starting a new run time period R(x).
[0089] Following step 168, the algorithm returns to the step of
retrieving the previous mandatory shed time S(x-1) at 156 in order
to iteratively operate following any run cycle. Other algorithms
can also be implemented.
[0090] As described generally above, if HVAC system 112
traditionally had short run times due to oversizing or weather
conditions, the aforementioned algorithm causes the mandatory shed
time to increase after each run, until individual run times are
gradually extended to meet or even exceed the minimum run time. For
example, the following theoretical data illustrates an example set
of run times generated according to a typical interior space
cooling scenario and the related calculated mandatory shed times,
summarized in Table 1. In this example, the minimum run time T is
10.
TABLE-US-00001 TABLE 1 Mandatory Shed Compressor Run Cycle Count
(x) Time S(x) Time R(x) 1 0 (default) 5 2 5 5 3 10 5 4 15 7 5 18 9
6 19 10 7 19 10 8 19 10
[0091] As illustrated by the values of Table 1, the calculated
mandatory shed time (S(x)) continues to increase as the run times
approach the set minimum run time T. As the calculated mandatory
shed time increases, the space is warmed by heating environmental
forces, and therefore, subsequent future run times are increased in
length as the compressor needs to run longer to cool the
increasingly warmed space. As the run time approaches the minimum
run time T, the calculated mandatory shed time levels off and
reaches an equilibrium point.
[0092] Traditionally, HVAC system 112 has natural on (nm) and off
(shed) times based on the space and the desired temperature,
whereby the compressor runs for a period of time to cool the
interior space, then remains off for a period of time while the
space gradually heats up. The aforementioned algorithm forces
deviations from the natural times, both shed times and run times.
Specifically, run time is extended via an increase in commanded off
time. Note that there will necessarily be larger swings in
temperature in a space when such an algorithm is implemented, due
to the underlying assumptions of the algorithm that it will take
longer to subsequently cool the space (and therefore the compressor
will be required to run longer and hence, more efficiently) when
HVAC system 112 is commanded off when naturally it would have been
commanded on by temperature control device 116, had LCD 118 not
been able to interrupt.
[0093] As understood by the above description, LCDs 118 of the
present invention may be configured to operate as load-shedding
devices, receiving commands from master station 102 via transceiver
136, and implementing predetermined or received load shedding
algorithms so as interrupt power to compressors 124 and decrease
overall energy demand on the utility. LCDs 118 may also, or
instead, be configured to operate as an energy-efficiency improving
device by indirectly extending run times of compressor 124 by
controlling shed times of compressor 124 using the methods and
algorithms described herein.
[0094] In an embodiment, LCD 118 is configured to continually
operate as an energy-efficiency improving device, and upon
receiving a load-shedding command from master station 102, override
the energy-efficiency algorithm in favor of a load shedding event.
Such a load-shedding event may comprise LCD 118 opening compressor
cutoff switch 140 for a predetermined period of time based upon a
predetermined duty cycle, for example, 15 minutes out of every
hour. Such a load-shedding event may interrupt the
energy-efficiency algorithm, causing it to restart after the
load-shedding event. In such an instance, a previous mandatory run
time duration S(x-1) may be reset to a default value, or return to
a pre-load-shedding-event value, without having to measure an
actual shed time. It will be understood that other combinations and
interactions of the at least two operational aspects of LCD 118,
namely traditional load shedding, and energy-efficiency
improvement, are intended to be within the scope of the present
invention.
[0095] In an embodiment, the methods and algorithms for indirectly
extending run times to improve efficiency may comprise an
efficiency feature that may be turned on or off in a particular
system 112 and its LCD 118. In other words, a system 100 or HVAC
system 112 may be allowed to run without being controlled so as to
indirectly extend the run times, but have the feature built in,
ready to be enabled as needed. In one such embodiment, the criteria
for turning the efficiency feature on or off may be based on local
or remote factors, including whether a measured system efficiency
falls below a threshold or optimal efficiency. A system 112 that is
already operating at or near an optimal efficiency may not have the
feature enabled, while a system 112 that regularly operates at a
low efficiency, may be directed to enable the efficiency feature of
the claimed invention. As will be discussed further below, the
decision to enable, or turn the feature on or off, may be made by a
utility, an end user/utility customer, or both.
[0096] In an embodiment, LCD 118 determines a system efficiency,
EFFsystem. As will be described further below, the system
efficiency may be based on one or more determined cycle
efficiencies, EFFcycle, such as on an average of a number of
determined cycle efficiencies. A cycle efficiency EFFcycle may be
based on a determined system efficiency of a single operating cycle
of system 112.
[0097] In an embodiment, cycle efficiency EFFcycle for a cycle is
determined based on a measured compressor run time R(i) of an
operating cycle according to Equation 2:
EFFcycle(x)=R(i)/T.sub.OPT EQN 2:
where EFFcycle(x) is the cycle efficiency, R(i) is the compressor
run time for the ith cycle, and T.sub.OPT is an optimum run time.
For instance, if compressor 124 runs for 4.5 minutes during a
particular cycle, the ith cycle, and an optimum run time is
previously determined to be 9 minutes, the cycle efficiency is 0.5,
or 50%.
[0098] While cycle efficiency represents system efficiency for a
single cycle, an improved method of determining system efficiency
EFFsystem determines system efficiency based on multiple data
points, or multiple cycle efficiencies, EFFcycle. In one such
embodiment, system efficiency EFFsystem is simply an average cycle
efficiency, such as determined according to Equation 3:
EFFsystem ( X N ) = ( 1 N i = 1 N EFFcycle ( Xi ) ) EQN . 3
##EQU00001##
Where EFFsystem(X.sub.N) is the system efficiency of the xth cycle,
EFFcycle(Xi) is the cycle efficiency of an ith cycle, and N is the
number of sampled cycles.
[0099] In the above embodiment, LCD 118 captures N run time values
for N cycles, determines a cycle efficiency EFFcycle for each
cycle, then determines an average system efficiency EFFsystem to be
an average of the cycle efficiencies over the N cycles. In an
embodiment, the N cycles are consecutive cycles, and in another
embodiment, the N cycles are not consecutive. It will be understood
that the system efficiency may be calculated in similar ways, such
as determining a number of run times, averaging the run times, then
dividing the average run time by an optimal run time T.sub.OPT, to
determine a system efficiency.
[0100] Referring to the flow diagram of FIG. 6, and to FIGS. 2 and
3, a method for determining system efficiency is depicted and
described.
[0101] At step 180, if a command or request to reset system
efficiency EFFsystem is received by LCD 118, or LCD 118 otherwise
determines to reset system efficiency EFFsystem, at step 182,
system efficiency EFFsystem is reset to an initial system
efficiency EFFsystem-initial. The initial system efficiency,
EFFsystem-initial, corresponds to a baseline efficiency determined
for a particular HVAC system 120, a particular region, a particular
climate, and so on. In some embodiments, the initial system
efficiency may be 100%.
[0102] It will be understood that LCD 118 may store in memory 134
data corresponding to system efficiency, including
EFFsystem-initial and EFFsystem. A value corresponding to an
initial system efficiency EFFsystem-initial may be stored in memory
134 of LCD 118. In an embodiment, this initial system efficiency
value may be entered into memory prior to deployment of LCD 118.
Further, EFFsystem-initial may remain constant, or may be subject
to change via processor 132. Processor 132 may change
EFFsystem-initial based on local data or conditions, or may change
or update EFFsystem-initial based on commands received over network
118.
[0103] Resetting system efficiency EFFsystem to be equal to an
initial system efficiency EFFsystem-initial may be desirable when
previous data relating to system efficiency is not required for
determining a current system efficiency or to measure system
efficiency after enabling/disabling the efficiency feature.
[0104] At step 184, an optional step, system 100 determines whether
the current time is within a predetermined time window. In an
embodiment, cycle and system efficiencies are only calculated
within a permissible time window. The time window generally
includes a start time and an end time. The start time is generally
the time of day that cycle run-times and related data are collected
for inclusion in the system efficiency calculation. The window end
time is generally the time of day to end collection of data for
determining system efficiency. Data used for determining cycle and
system efficiencies may be collected continuously during the
predetermined time window, or may be collected periodically during
the duration of the time window.
[0105] In an embodiment, the start time and end time remain the
same for each day. In other embodiments, the start and end time may
change. In one such embodiment, the start and end times change on a
seasonal basis, for example, the time window for summer may be
later in the day as compared to fall. The start and end times may
also be modified or optimized based on the processing needs of LCD
118. In one such embodiment, the time window may be shifted if LCD
118 is collecting data for other purposes, or transmitting data
over network 108.
[0106] If at step 184, a current time is not within the time
window, cycle and system efficiencies are not updated.
[0107] If the current time is within the time window, data is
collected, and cycle efficiency and/or system efficiency is
calculated.
[0108] At step 186, cycle efficiency, EFFcycle is calculated for a
particular cycle. The cycle efficiency may be calculated according
to EQN. 2 as described above. In an embodiment, if a measured run
time R(x) exceeds an optimal run time, T.sub.OPT, the cycle
efficiency EFFcycle(x) for that cycle is set to 1 or 100%.
[0109] In an embodiment, the optimal run time T.sub.OPT is saved in
memory 134 of LCD 118, as is the minimum run time T.sub.MIN. As
discussed above with respect to FIG. 1, the optimal run time is
generally determined by the operating characteristics of HVAC
system 112, under a predetermined set of climatic conditions such
as air temperature, air humidity, and so on. The optimal run time,
T.sub.OPT, may be set to a predetermined value, such as 9 minutes
in the example of FIG. 1, and saved in LCD 118 prior to deployment
at a facility 110. However, the optimal run time may be modified on
site by an installer based on local conditions, by a master
controller communicating to LCD 118 over network 108, or otherwise
modified. The modifications, an increase or decrease, to the
optimal run time may be due to regional or local conditions such as
expected air temperature, air humidity, solar radiation (cloud
cover), and elevation. In an embodiment, a current state of the
optimal run time, as well as other stored or saved parameters
including minimum run time, window start and end times, and initial
system efficiency, may be read at LCD 118 or communicated over a
network, such as network 108.
[0110] At step 188, system efficiency EFFsystem is determined. In
an embodiment, system efficiency is determined by EQN. 3, or by
similarly averaging cycle efficiencies EFFcycle. In another
embodiment, system efficiency EFFsystem is iteratively determined
by adjusting the currently-stored system efficiency, which could be
the system efficiency calculated at a previous time, or the initial
system efficiency, EFFsystem-initial, following a reset, plus a
weighted average of cycle efficiencies EFFcycle. In such an
embodiment, system efficiency may be determined by EQN. 4 as
follows:
EFFsystem(X.sub.N)=EFFsystem(X.sub.N-1)+EFFcycle(Xi)/Weighting
Factor EQN. 4:
where EFFsystem(X.sub.N) represents a current system efficiency,
EFFsystem(X.sub.N-1) represents a previously determined system
efficiency value, EFFcycle(Xi) represents a current determined
cycle efficiency, and Weighting Factor is a weighting factor. The
weighting factor determines the effect that an individual sample
may have on the overall, determined system efficiency,
EFFsys(X.sub.N). In an embodiment, Weighting Factor is 64, such
that a current efficiency is the sum of a previous system
efficiency plus 1/64.sup.th of a current cycle efficiency. In other
embodiments, the weighting factor may be greater or lesser,
resulting in a current cycle efficiency have more or less influence
on determined system efficiency.
[0111] At step 190, the system efficiency, EFFsystem(X.sub.N), may
be stored in memory 134 of LCD 118, may be transmitted over network
108, or LCD 118 may continue to monitor and collect run time data
for efficiency determination as needed.
[0112] Any of the system efficiency or cycle efficiency data may be
stored locally or transmitted to a remote location, such as
transmitted over network 108 to a utility 102. Such efficiency data
may be used in any number of ways, including to determine whether
to turn on the extended run-time feature of the claimed
invention.
[0113] In an embodiment, an authorized user, such as a utility, an
installer, or in some cases, an authorized end-user, may activate
or deactivate the extended run-time feature. In the case of the
authorized user being a utility, the utility may authorize use of
the feature as part of an energy-efficiency program. If the
authorized user is an end-user consumer, the feature may be
activated by the end-user as part of a rate-based program. If an
end-user consumer has purchased or otherwise owns LCD 118 (as
opposed to a utility), the end-user will generally be able to
modify the parameters or authorize a third party to make
modifications.
[0114] The activation may be implemented as a binary state stored
in memory 134 of LCD 118. When activated system 100 and LCD 118
will perform the efficiency control functions described above; when
deactivated, LCD 118 will not perform the extended run time
control, but in some embodiments, may continue to measure,
calculate, and store or transmit, cycle and system
efficiencies.
[0115] In an embodiment, extended run time control is implemented
if a system efficiency is below a predetermined threshold. In one
such embodiment, the threshold may be 80%; in another such
embodiment, the threshold may be 70%. It will be understood that
such a threshold may be determined, and may comprise any desired
value.
[0116] The embodiments above are intended to be illustrative and
not limiting. Additional embodiments are within the claims. In
addition, although aspects of the present invention have been
described with reference to particular embodiments, those skilled
in the art will recognize that changes can be made in form and
detail without departing from the spirit and scope of the
invention, as defined by the claims.
[0117] Persons of ordinary skill in the relevant arts will
recognize that the invention may comprise fewer features than
illustrated in any individual embodiment described above. The
embodiments described herein are not meant to be an exhaustive
presentation of the ways in which the various features of the
invention may be combined. Accordingly, the embodiments are not
mutually exclusive combinations of features; rather, the invention
may comprise a combination of different individual features
selected from different individual embodiments, as understood by
persons of ordinary skill in the art.
[0118] Any incorporation by reference of documents above is limited
such that no subject matter is incorporated that is contrary to the
explicit disclosure herein. Any incorporation by reference of
documents above is further limited such that no claims included in
the documents are incorporated by reference herein. Any
incorporation by reference of documents above is yet further
limited such that any definitions provided in the documents are not
incorporated by reference herein unless expressly included
herein.
[0119] For purposes of interpreting the claims for the present
invention, it is expressly intended that the provisions of Section
112, sixth paragraph of 35 U.S.C. are not to be invoked unless the
specific terms "means for" or "step for" are recited in a
claim.
* * * * *