USOO8131497B2
`
`(12) United States Patent
`Steinberg et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8.131,497 B2
`*Mar. 6, 2012
`
`(54) SYSTEMAND METHOD FOR CALCULATING
`THE THERMAL MASS OF A BUILDING
`
`(75) Inventors: John Douglas Steinberg, Millbrae, CA
`(US); Scott Douglas Hublou, Redwood
`City, CA (US)
`
`(73) Assignee: EcoFactor, Inc., Millbrae, CA (US)
`(*) Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by O days.
`This patent is Subject to a terminal dis
`claimer.
`(21) Appl. No.: 12/959,225
`y x- - -
`9
`Dec. 2, 2010
`
`(22) Filed:
`
`(65)
`
`Prior Publication Data
`
`Mar. 31, 2011
`US 2011 FOOT7896 A1
`Related U.S. Application Dat
`elated U.S. Application Uata
`(63) Continuation of application No. 12/21 1,733, filed on
`Sep. 16, 2008, now Pat. No. 7,848,900.
`(60) Provisional application No. 60/994,011, filed on Sep.
`17, 2007.
`51) Int. Cl.
`(51) In
`(2006.01) 702/130: 702/182
`52 else
`(52)
`ir grgrrr.
`s
`(58) Field of Classification Search .................. 702/130,
`702/182; 700/276, 277,278; 236/91 D;
`165/58, 200, 287
`See application file for complete search history.
`
`(56)
`
`References Cited
`
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`OTHER PUBLICATIONS
`Arens, et al., “How Ambient Intelligence Will Improve Habitability
`and Energy Efficiency in Buildings”, 2005, research paper, Centerfor
`the Built Environment, Controls and Information Technology.
`Continued
`(Continued)
`
`Primary Examiner — Edward Raymond
`Assistant Examiner — Elias Desta
`(74) Attorney, Agent, or Firm — Knobbe, Martens, Olson &
`Bear, LLP
`
`ABSTRACT
`(57)
`The invention comprises a system for calculating a value for
`the effective thermal mass of a building. The climate control
`system obtains temperature measurements from at least a first
`location conditioned by the climate system. One or more
`processors receive measurements of outside temperatures
`from at least one source other than the control system and
`compare the temperature measurements from the first loca
`tion with expected temperature measurements. The expected
`temperature measurements are based at least in part upon past
`temperature measurements obtained by said HVAC control
`system and said outside temperature measurements. The pro
`cessors then calculate one or more rates of change in tem
`perature at said first location.
`
`12 Claims, 13 Drawing Sheets
`
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`input profit oatar'
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`COPARATWE CATA
`
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`
`CALCULATE EXPECTED
`INSIDE TEPERATURE
`READING
`
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`
`DOES INSIDE
`TEMPERATURE REAEINGYYES
`weRGE FROM
`REDICTP VALU
`
`NO
`
`AND SOLAR PROGRESSION
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`CAcLATE EXPECE)
`DuRATION OF
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`
`A2
`
`tas
`SET TARGET TEPERATURE BASED
`08 CALCULATED DAA FOR
`RAON OF SORCNEVENT
`
`
`
`SENE MESSAGE 0.
`HOMEWNER RE PROBLEM
`
`f:37
`
`GOOGLE 1028
`
`001
`
`

`

`US 8,131497 B2
`Page 2
`
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`6/2007 Bodin et al.
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`7,356,384 B2
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`8, 2010 Harter
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`7,848,900 B2 * 12/2010 Steinberg et al. ............. TO2/130
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`2/2011 Sloup et al.
`2003/004.0934 A1
`2/2003 Skidmore et al.
`2005/0222889 A1 10, 2005 Lai et al.
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`2009,028.1667 A1 11/2009 Masui et al.
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`2010, 0211224 A1
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`9, 2010 Thind
`2010/0289643 A1 11/2010 Trundle et al.
`2011 OO31323 A1
`2/2011 Nold et al.
`OTHER PUBLICATIONS
`Honeywell, W7600/W7620 Controller Reference Manual,
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`Johnson Controls, Touch4 building automation system brochure,
`2007.
`Kilicotte, et al., “Dynamic Controls for Energy Efficiency and
`Demand Response: Framework Concepts and a New Construction
`Study Case in New York”. Proceedings of the 2006 ACEEE Summer
`Study of Energy Efficiency in Buildings, Pacific Grove. CA, Aug.
`13-18, 2006.
`Lin, et al., “Multi-Sensor Single-Actuator Control of HVAC Sys
`tems', 2002.
`Wang, et al., “Opportunities to Save Energy and Improve Comfort by
`Using Wireless Sensor Networks in Buildings.” (2003), Center for
`Environmental Design Research.
`Wetter, et al. A comparison of deterministic and probabilistic opti
`mization algorithms for nonsmooth simulation-based optimization.
`Building and Environment 39, 2004, pp. 989-999.
`* cited by examiner
`
`002
`
`

`

`U.S. Patent
`
`Mar. 6, 2012
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`Sheet 1 of 13
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`US 8,131497 B2
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`U.S. Patent
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`Mar. 6, 2012
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`Sheet 2 of 13
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`US 8,131497 B2
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`U.S. Patent
`U.S. Patent
`
`Mar.6, 2012
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`US 8,131497 B2
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`U.S. Patent
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`Mar. 6, 2012
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`U.S. Patent
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`Mar. 6, 2012
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`Sheet 5 of 13
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`US 8,131.497 B2
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`U.S. Patent
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`Mar. 6, 2012
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`Sheet 6 of 13
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`US 8,131497 B2
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`U.S. Patent
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`Mar. 6, 2012
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`US 8,131497 B2
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`U.S. Patent
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`Mar. 6, 2012
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`U.S. Patent
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`Mar. 6, 2012
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`U.S. Patent
`
`Mar. 6, 2012
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`Sheet 11 of 13
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`US 8,131497 B2
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`

`

`U.S. Patent
`
`Mar. 6, 2012
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`Sheet 12 of 13
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`US 8,131497 B2
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`

`U.S. Patent
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`Mar. 6, 2012
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`Sheet 13 of 13
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`US 8,131497 B2
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`

`

`1.
`SYSTEMAND METHOD FOR CALCULATING
`THE THERMAL MASS OF A BUILDING
`
`2
`advance with programmable thermostats is that they can shift
`between multiple present temperatures at different times.
`
`US 8, 131497 B2
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This application is a continuation of U.S. patent applica
`tion No. 12/21 1,733, filed Sept. 16, 2008 which claims pri
`ority under 35 U.S.C. S 119(e) to U.S. Provisional Application
`No. 60/994,011, filed Sept. 17, 2007, the entirety of each of
`which is hereby incorporated herein by reference and is to be
`considered part of this specification.
`
`BACKGROUND OF THE INVENTION
`
`10
`
`15
`
`30
`
`40
`
`45
`
`1. Field of the Invention
`This invention relates to the use of thermostatic HVAC
`controls that are connected to a computer network. More
`specifically, communicating thermostats are combined with a
`computer network to calculate the thermal mass of a struc
`ture.
`2. Background
`Climate control systems such as heating and cooling sys
`tems for buildings (heating, ventilation and cooling, or HVAC
`25
`systems) have been controlled for decades by thermostats. At
`the most basic level, a thermostat includes a means to allow a
`user to set a desired temperature, a means to sense actual
`temperature, and a means to signal the heating and/or cooling
`devices to turn on or offin order to try to change the actual
`temperature to equal the desired temperature. The most basic
`versions of thermostats use components such as a coiled
`bi-metallic spring to measure actual temperature and a mer
`cury Switch that opens or completes a circuit when the spring
`coils or uncoils with temperature changes. More recently,
`electronic digital thermostats have become prevalent. These
`thermostats use solid-state devices such as thermistors or
`thermal diodes to measure temperature, and microprocessor
`based circuitry to control the switch and to store and operate
`based upon user-determined protocols for temperature Vs.
`time.
`These programmable thermostats generally offer a very
`restrictive user interface, limited by the cost of the devices,
`the limited real estate of the small wall-mounted boxes, and
`the inability to take into account more than two variables: the
`desired temperature set by the user, and the ambient tempera
`ture sensed by the thermostat. Users can generally only set
`one series of commands per day, and in order to change one
`parameter (e.g., to change the late-night temperature) the user
`often has to cycle through several other parameters by repeat
`edly pressing one or two buttons.
`Because the interface of programmable thermostats is so
`poor, the significant theoretical savings that are possible with
`them (sometimes cited as 25% of heating and cooling costs)
`are rarely realized. In practice, studies have fund that more
`than 50% of users never program their thermostats at all.
`Significant percentages of the thermostats that are pro
`grammed are programmed Sub-optimally, in part because,
`once programmed, people tend to not to re-invest the time
`needed to change the settings very often.
`A second problem with standard programmable thermo
`stats is that they represent only a small evolutionary step
`beyond the first, purely mechanical thermostats. Like the first
`thermostats, they only have two input signals—ambient tem
`perature and the preset desired temperature. The entire
`
`50
`
`55
`
`60
`
`65
`
`SUMMARY OF THE INVENTION
`
`There are many other sources of information that could be
`used to increase comfort, decrease energy use, or both. For
`example, outside temperature and humidity strongly affect
`subjective comfort. On a 95 degree, 90 percent humidity day
`in August, when people tend to dress in lightweight clothing,
`a house cooled to 70 degrees will feel cool or even uncom
`fortably cold. On a below-freezing day in January, when
`people tend to wear Sweaters and heavier clothes, that same
`70 degree home will feel too warm. It would therefore be
`advantageous for a thermostat system to automatically incor
`porate information about external weather conditions when
`setting the desired temperature.
`Thermostats are used to regulate temperature for the ben
`efit of the occupants in a given space. (Usually this means
`people, but it can of course also mean critical equipment, Such
`as in a room filled with computer equipment.) In general,
`thermostats read temperature from the sensor located within
`the “four corners' of the thermostat. With a properly designed
`system, the thermostat may well be located such that the
`temperature read at the precise location of the thermostat
`accurately reflects the conditions where the human (or other)
`occupants tend to be. But there are many reasons and circum
`stances in which that will not be the case. A single thermostat
`may produce accurate readings in Some circumstances but not
`others; it may be located in a place far from the occupants, or
`too far from the ductwork controlled by the thermostat, etc. In
`one house, for example, the thermostat may be located in a
`spot that receives direct Sunlightonhot afternoons. This could
`cause the thermostatto sense that the local ambient tempera
`ture is extremely high, and as a result signal the A/C to run too
`long, making the rest of the home too cold, and wasting
`considerable energy. In anotherhouse, the thermostat may be
`located in a hallway without ductwork or where the nearby
`ducts have been closed. In Such a scenario, the thermostat is
`likely to (correctly) report cold temperatures in the winter,
`leading the heating system to overheat the rest of the house
`and waste considerable energy.
`These problems can be reduced or eliminated through use
`of additional remote temperature sensors connected to the
`thermostat's control circuitry. However, Such systems require
`additional hardware, additional thermostat complexity, and
`skilled installation and configuration.
`It would therefore be desirable for a thermostat system
`using only a single temperature sensor to take Such Sub
`optimal installations into account and to correct for the erro
`neous readings generated by Such thermostats.
`Different structures will respond to changes in conditions
`Such as external temperature in different ways. For example,
`houses built 50 or more years ago will generally have little or
`no insulation, be poorly sealed, and have simple single-glazed
`windows. Such houses will do a very poor job of retaining
`internal heat in the winter and rejecting external heat in the
`Summer. In the absence of applications of thermal measures
`Such as heating and air conditioning, the inside temperature in
`such houses will trend to track outside temperatures very
`closely. Such houses may be said to have low thermal mass. A
`house built in recent years, using contemporary techniques
`for energy efficiency Such as high levels of insulation, double
`glazed windows and other techniques, will, in the absence of
`intervention, tend to absorb external heat and release internal
`heat very slowly. The newerhouse can be thought of as having
`higher thermal mass than the older house.
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`A conventional thermostat has no mechanism by which it
`might take the thermal mass of the structure into account, but
`thermal mass significantly affects many parameters relating
`to energy efficiency.
`The cost to an electric utility to produce power varies over
`time. Indeed, the cost of production between low demand and
`peak demand periods can vary by as much as an order of
`magnitude. Traditionally, residential customers paid the same
`price regardless of time or the cost to produce. Thus consum
`ers have had little financial incentive to reduce consumption
`during periods of high demand and high production cost.
`Many electric utilities are now seeking to bring various forms
`of variable rates to the retail energy markets. Under such
`schemes, consumers can reduce costs by taking into account
`not just how much energy they use, but when they use it.
`Thus many consumers now can see real benefits from opti
`mizing not just the total number of kilowatt-hours of electric
`ity consumed, but also optimizing when it is used. The opti
`mum strategy for energy use over time will vary based upon
`many variables, one of which is the thermal mass of the
`structure being heated or cooled. In a structure with high
`thermal mass, heating and cooling can effectively be shifted
`away from high cost periods to lower cost “shoulder' periods
`with little or no effect on comfort. If, for example, a utility
`charges much higher rates on hot Summer afternoons, it is
`likely that pre-cooling a high-thermal mass structure just
`before the high-cost period and then shutting down the air
`conditioning during the peak will allow the house to remain
`comfortable. But in a house with low thermal mass, the ben
`efits of pre-cooling will quickly dissipate, and the house will
`rapidly become uncomfortable if the air conditioning is shut
`off. Thus it would be advantageous for a temperature control
`system to take thermal mass into account when setting desired
`temperatures.
`Many factors affect the efficiency of HVAC systems. Some
`may be thought of as essentially fixed. Such as the theoretical
`efficiency of a central air conditioner (often expressed as its
`SEER rating), the matching of a given system to the charac
`teristics of a given home, the location and size of forced-air
`ductwork, etc. Other contributors to efficiency are more
`dynamic, such as clogged filters, refrigerant leaks, duct leak
`age and “pop-offs.” and the like.
`Most of these problems are likely to manifest themselves in
`the form of higher energy bills. But the “signature' of each
`different problem can be discerned from the way in which
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`each such problem affects the cycle times of a given HVAC
`system over time and relative to weather conditions and the
`performance of other HVAC systems in other houses. If two
`otherwise identical houses are located next door to each other
`and have gas furnaces, but one is rated at 50,000 BTUs and the
`other is rated at 100,000 BTUs, the cycle times for the higher
`capacity furnace should be shorter than for the lower-capacity
`unit. If both of those same houses have identical furnaces, but
`one has a clogged filter, the cycle times should belonger in the
`house with the clogged filter. Because cycling of the HVAC
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`system is controlled by the thermostat, those differences in
`cycle time would be reflected in the data sensed by and
`control signals generated by the thermostat. It would be
`advantageous for a thermostat system to be able to use that
`information to diagnose problems and make recommenda
`tions based upon that data.
`These needs are satisfied by at least one embodiment of the
`invention that includes a system for calculating a value for the
`effective thermal mass of a building comprising: at least one
`HVAC control system that measures temperature at least a
`first location conditioned by said HVAC system, and report
`ing said temperature measurements as well as the status of
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`said HVAC control system; one or more processors that
`receive measurements of outside temperatures from at least
`one source other than said HVAC control systems and com
`pare said temperature measurements from said first location
`with expected temperature measurements wherein the
`expected temperature measurements are based at least in part
`upon past temperature measurements obtained by said HVAC
`control system and said outside temperature measurements;
`and one or more databases that store at least said temperatures
`measured at said first location over time; calculating one or
`more rates of change in temperature at said first location; and
`relating said calculated rates of change to said outside tem
`perature measurements.
`Another embodiment includes a system for calculating a
`value for the operational efficiency of an HVAC system com
`prising at least one HVAC control system that measures tem
`perature at least a first location conditioned by said HVAC
`system, and reporting said temperature measurements as well
`as the status of said HVAC control system; one or more
`processors that receive measurements of outside tempera
`tures from at least one source other than said HVAC control
`systems and compare said temperature measurements from
`said first location with expected temperature measurements
`wherein the expected temperature measurements are based at
`least in part upon past temperature measurements obtained by
`said HVAC control system and said outside temperature mea
`Surements; and one or more databases that store at least said
`temperatures measured at said first location over time; calcu
`lating one or more rates of change in temperature at said first
`location for periods during which the status of the HVAC
`system is "on': calculating one or more rates of change in
`temperature at said first location for periods during which the
`status of the HVAC system is “off; and relating said calcu
`lated rates of change to said outside temperature measure
`mentS.
`A further embodiment includes a system for evaluating
`changes in the operational efficiency of an HVAC system over
`time comprising at least one HVAC control system that mea
`Sures temperature at least a first location conditioned by said
`HVAC system, and reporting said temperature measurements
`as well as the status of said HVAC control system; one or
`more processors that receive measurements of outside tem
`peratures from at least one source other than said HVAC
`control systems and compare said temperature measurements
`from said first location with expected temperature measure
`ments wherein the expected temperature measurements are
`based at least in part upon past temperature measurements
`obtained by said HVAC control system and said outside tem
`perature measurements; and one or more databases that store
`at least said temperatures measured at said first location over
`time.
`A further embodiment includes a system for detecting and
`correcting for anomalous behavior in HVAC control systems
`comprising a first HVAC control system that measures tem
`perature at least a first location conditioned by said first
`HVAC system, and reporting said temperature measurements
`as well as the status of said first HVAC control system; at least
`a second HVAC control system that measures temperature at
`least a second location conditioned by said second HVAC
`system, and reporting said temperature measurements as well
`as the status of said second HVAC control system; one or
`more processors that receive measurements of outside tem
`peratures from at least one source other than said first and
`second HVAC control systems and compare said temperature
`measurements from said first HVAC controls system and said
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`second HVAC control system and said outside temperature
`measurements; and one or more databases that store said
`temperatures measurements.
`In at least one embodiment, the invention comprises a
`thermostat attached to an HVAC system, a local network
`connecting the thermostat to a larger network Such as the
`Internet, and one or more additional thermostats attached to
`the network, and a server in bi-directional communication
`with a plurality of such thermostats. The server logs the
`ambient temperature sensed by each thermostat vs. time and
`the signals sent by the thermostats to their HVAC systems.
`The server preferably also logs outside temperature and
`humidity data for the geographic locations for the buildings
`served by the connected HVAC systems. Such information is
`widely available from various sources that publish detailed
`weather information based on geographic areas such as by
`ZIP code. The server also stores other data affecting the load
`upon the system, Such as specific model of HVAC system,
`occupancy, building characteristics, etc. Some of this data
`may be supplied by the individual users of the system, while
`other data may come from third-party sources such as the
`electric and other utilities who supply energy to those users.
`Combining these data sources will also allow the server to
`calculate the effective thermal mass of the structures condi
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`tioned by those thermostats. By combining data from mul
`tiple thermostats in a given neighborhood, the system can
`correct for flaws in the location of a given thermostat, and can
`evaluate the efficiency of a given system, as well as assist in
`the diagnosis of problems and malfunctions in Such systems.
`This and other advantages of certain embodiments of the
`invention are explained in the detailed description and claims
`that make reference to the accompanying diagrams and flow
`charts.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 shows an example of an overall environment in
`which an embodiment of the invention may be used.
`FIG. 2 shows a high-level illustration of the architecture of
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`a network showing the relationship between the major ele
`ments of one embodiment of the subject invention.
`FIG. 3 shows an embodiment of the website to be used as
`part of the subject invention.
`FIG. 4 shows a high-level schematic of the thermostatused
`as part of the Subject invention.
`FIG. 5 shows one embodiment of the database structure
`used as part of the Subject invention
`FIGS. 6a and 6b show graphical representations of inside
`and outside temperatures in two different homes, one with
`high thermal mass and one with low thermal mass.
`FIGS. 7a and 7b show graphical representations of inside
`and outside temperatures in the same homes as in FIGS. 6a
`and 6b, showing the cycling of the air conditioning systems in
`those houses.
`FIGS. 8a and 8b show graphical representations of inside
`and outside temperatures in the same home as in FIGS. 6a and
`7a, showing the cycling of the air conditioning on two differ
`ent days in order to demonstrate the effect of a change in
`operating efficiency on the parameters measured by the ther
`moStat.
`FIGS. 9a and 9b show the effects of employing a pre
`cooling strategy in two different houses.
`FIGS. 10a and 10b show graphical representations of
`inside and outside temperatures in two different homes in
`order to demonstrate how the system can correct for errone
`ous readings in one house by referencing readings in another.
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`FIG. 11 is a flowchart illustrating the steps involved in
`calculating the effective thermal mass of a home using the
`Subject invention.
`FIG. 12 is a flowchart illustrating the steps involved in
`determining whether an HVAC system has developed a prob
`lem that impairs efficiency using the Subject invention.
`FIG. 13 is a flowchart illustrating the steps involved in
`correcting for erroneous readings in one house by referencing
`readings in another using the Subject invention.
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`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`FIG. 1 shows an example of an overall environment 100 in
`which an embodiment of the invention may be used. The
`environment 100 includes an interactive communication net
`work 102 with computers 104 connected thereto. Also con
`nected to network 102 are one or more server computers 106,
`which store information and make the information available
`to computers 104. The network 102 allows communication
`between and among the computers 104 and 106.
`Presently preferred network 102 comprises a collection of
`interconnected public and/or private networks that are linked
`to together by a set of standard protocols to form a distributed
`network. While network 102 is intended to refer to what is
`now commonly referred to as the Internet, it is also intended
`to encompass variations which may be made in the future,
`including changes additions to existing standard protocols.
`When a user of the subject invention wishes to access
`information on network 102, the buyer initiates connection
`from his computer 104. For example, the user invokes a
`browser, which executes on computer 104. The browser, in
`turn, establishes a communication link with network 102.
`Once connected to network 102, the user can direct the
`browser to access information on server 106.
`One popular part of the Internet is the World Wide Web.
`The World WideWeb contains a large number of computers
`104 and servers 106, which store HyperText Markup Lan
`guage (HTML) documents capable of displaying graphical
`and textual information. HTML is a standard coding conven
`tion and set of codes for attaching presentation and linking
`attributes to informational content within documents.
`The servers 106 that provide offerings on the World Wide
`Web are typically called websites. A website is often defined
`by an Internet address that has an associated electronic page.
`Generally, an electronic page is a document that organizes the
`presentation of text graphical images, audio and video.
`In addition to the Internet, the network 102 can comprise a
`wide variety of interactive communication media. For
`example, network 102 can include local area networks, inter
`active television networks, telephone networks, wireless data
`systems, two-way cable systems, and the like.
`In one embodiment, computers 104 and servers 106 are
`conventional computers that are equipped with communica
`tions hardware Such as modem or a network interface card.
`The computers include processors such as those sold by Intel
`and AMD. Other processors may also be used, including
`general-purpose processors, multi-chip processors, embed
`ded processors and the like.
`Computers 104 can also be handheld and wireless devices
`Such as personal digital assistants (PDAs), cellular telephones
`and other devices capable of accessing the network.
`Computers 104 utilize a browser configured to interact
`with the World Wide Web. Such browsers may include
`Microsoft Explorer, Mozilla, Firefox, Opera or Safari. They
`may also include browsers used on handheld and wireless
`devices.
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`The storage medium may comprise any method of storing
`information. It may comprise random access memory
`(RAM), electronically erasable programmable