Patent Application
20150025693
The present invention relates generally to a system and method for temperature control.
Intelligent thermostats today contain algorithms to monitor the occupant's habits and predict thermostat settings, predict how long it takes to reach a desired thermostat temperature, and estimate how the outside temperature affects energy usage.
Conventional thermostats do not take into account the perceptual aspect of heating and cooling. All heater and air conditioning units generate air at a much higher or lower temperature than typical thermostat temperature settings. Indeed, many heaters or AC units only produce air at a fixed (or a narrow range of) temperature. That is, a heater or AC that turns on more often will “feel” warmer or cooler than what the thermostat thermometer indicates. This may create a less than ideal environment which can cause, for example, discomfort to building occupants.
There is a nonlinear perceptual mapping that connects the rate of heating/cooling versus the temperature perceived by occupants in the room. This mapping can also depend on other factors such as the amount of (sun)light, the humidity in the room and the temperature and flow rate at the output of the climate control device. An exemplary aspect of the invention leverages this notion to design a thermostat that is more consistent in comfort to the occupants, regardless of the outside temperature, the inside temperature, the desired temperature and, optionally, other factors as stated above.
In view of the foregoing and other exemplary problems, drawbacks, and disadvantages of the conventional systems, an exemplary aspect of the invention is directed to providing more consistent comfort in a climate control device such as HVAC (heating, ventilation and air conditioning) systems of human-occupied buildings. A climate control device or an HVAC device can be heaters, furnaces, chillers, fans and other devices used to regulate the temperature of an area.
An exemplary aspect of the invention includes a method of controlling a temperature of an area. The method includes determining a perceptual temperature factor based on at least the schedule and the inside temperature, adjusting the desired temperature based on the perceptual temperature factor, and after the adjusting the desired temperature, determining a schedule for a climate control device needed for the inside temperature to reach the adjusted desired temperature.
Another exemplary aspect of the invention is directed to a thermostat including a temperature sensor input configured so as to receive a temperature of an area, a desired temperature input unit, a control unit configured so as to output a control signal to an climate control device, and a processor configured so as to determine a schedule for the climate control device and which adjusts the desired temperature based on a perceptual temperature factor. The perceptual temperature factor is determined based on the temperature of the area and the schedule.
Yet another exemplary aspect of the invention includes, in addition to the previous exemplary aspect, a temperature sensor unit configured so as to receive the temperature outside of the area, and a module to determine the perceptual temperature factor based on the temperature of the area, and the outside temperature.
Yet another exemplary aspect of the invention includes, in addition to the previous exemplary aspect, a humidity sensor unit configured so as to receive the humidity, and a module to determine the perceptual temperature factor based on the temperature of the area, the outside temperature and the humidity of the area.
Yet another exemplary aspect of the invention includes a non-transitory programmable storage medium tangibly embodying a program of machine-readable instructions executable by a digital processing apparatus to perform a method. The method includes receiving a desired temperature and a temperature of an area, determining a schedule for a climate control device based at least on the desired temperature and the temperature of the area, determining a perceptual temperature factor based on at least the schedule and the temperature of the area, adjusting the desired temperature based on the perceptual temperature factor, after the adjusting the desired temperature, repeating the determining the schedule, and sending instructions to the climate control device based on the schedule.
The above exemplary aspects of the invention may provide a thermostat that is more consistent in comfort to the occupants, regardless of the outside temperature, the inside temperature and the desired temperature.
The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of embodiments of the invention with reference to the drawings, in which:
Referring now to the drawings, and more particularly to
An exemplary aspect of the invention leverages the nonlinear perceptual mapping that connects the rate of heating/cooling versus the temperature perceived by occupants in the room. This can provide a thermostat/controller 1 that is more consistent in comfort to the occupants, regardless of the outside temperature, the inside temperature and the desired temperature. While exemplary embodiments will be described in reference to an HVAC system 3, any system(s) affecting the air or climate of an enclosed area (e.g., a room or building) may be controlled (e.g., fan, heater, cooler, humidifiers, air conditioning unit, chiller, blinds, etc.).
The perceived temperature is affected by several factors. For instance, if the outside temperature is low, then a heater will need to turn on more frequently or longer to maintain a temperature setting. The frequency and amount of time in which the heater is on affects the temperature actually felt in the room which can be hotter or colder as the temperature fluctuates and air mixes. Thus, in a traditional thermostat, setting an inside temperature to 75 degrees when the outside temperature is 20 degrees would provide an perception of inside temperature that is different from that when the inside temperature setting is set to 75 degrees and the outside temperature is 70 degrees.
Humidity also plays a role in perceived temperature. For example, a humid room will feel much different than a non-humid room during a heating or cooling operation. (e.g., see the Heat Index chart at www.nws.noaa.gov/om/heat/index.shtml), the entirety of which is incorporated herein by reference. In addition, the amount of radiant heating (e.g., solar heating) received in the room can alter the perceived temperature.
In addition, the temperature and the flow rate (which can depend on the fan speed of the climate control device) of the air at the output of the climate control device will also affect the perceived temperature if that air comes directly into contact with the room occupants (e.g., see the Windchill chart at www.nws.noaa.gov/om/winchill/), the entirety of which is incorporated herein by reference.
An exemplary embodiment of the invention may control an HVAC system 3 based on not just a set or desired temperature, but also on the outside temperature, inside temperature, inside humidity, room geometry, temperature and flow rate at air vents, and other factors. Any appropriate sensor(s) 2 may be used to detect or determine the humidity, inside temperature, outside temperature, radiant heating (e.g., solar heating), and etc. In addition, it is possible to have multiple thermostats communicate so as to coordinate schedules and data using a protocol such as BACnet (e.g., see www.bacnet.org, the entirety of which is incorporated herein by reference).
An exemplary aspect of the invention calculates a schedule for running the HVAC system 3 based on the building/room size and/or geometry, inside and outside temperature, humidity, heating or cooling capacity of the HVAC system, minimum and maximum cycle time for the HVAC system, air flow rates, air flow, etc.
For instance, in an exemplary embodiment of the invention the thermostat 1 measures both outside temperature To and inside temperature Ti and estimates the schedule of turning the HVAC system 3 on or off to allow the inside temperature Ti to reach the desired temperature Td over a period of time H. This schedule is denoted S(t)=F(To, Ti, Td, H) and is typically an indicator function of time.
Based on the value of S(t), the system can estimate a perceptual temperature factor W of the schedule and adjust Td: Td←Td+W. The perceptual temperature factor is somewhat similar to a “wind chill” factor (e.g., see www.en.wikipedia.org/wild/Wind_chill, the entirety of which is incorporated herein by reference) or a “heat index” factor mentioned above, in that it is used to calculate the perceived temperature. This new schedule S(t) is then used to control the HVAC system.
In an exemplary embodiment, a new S(t) is computed and the process iterated to arrive at the final schedule S(t). There are several ways to do the iterations. One way is to iterate S(t) over the entire period of interest until a fixed point is obtained. Another way is to solve the implicit function S(t)=F(To, Ti, Td, S(t), H) using numerical analysis. For instance, one method is to use Newton's method to solve for the value of S(t) (e.g., see www.en.wikipedia.org/wiki/Newton's_method, the entirety of which is incorporated herein by reference). Yet another way is to calculate S(t)=F(To, Ti, Td, H) for a short period of time and use the adjusted Td to calculate the schedule for the next period of time.
The estimation of the schedule S(t) can be based on thermal and heat transfer models of the building or empirical data collected over time and may require knowledge of the HVAC capacity (BTU/Hr) as well. Examples of such modeling can be performed using computer tools such as Autodesk Revit (www.autodesk.com/products/autodesk-revit-family/overview) or Energy Plus (www.appsl.eere.energy.gov/buildings/energyplus/), the content of each of which is incorporated by reference in its entirety.
The curve W=W(S(t),Ti), used to estimate the adjustment factor W, can be determined using psychological experiments. For instance, there could be a relationship between the duty cycle of S(t) and W. The function W could also depend on the desired temperature Td. The function W could also depend on factors such as the amount of solar heating in the room and the humidity. Another way to determine the function W is record how users adjust the thermostat temperature setting in a traditional thermostat depending on the original thermostat setting, the indoor temperature, and the outdoor temperature. Implementation of the curve W can be done either by computations using equations or via a table lookup, similar to the tables for “wind chill” factor or “heat index” mentioned earlier, which are 2-D tables. In an exemplary embodiment, these tables may have more than 2 dimensions.
In an exemplary embodiment, the schedule S(t) can be determined without the need of outside temperature To by using historical data about heating schedules of the same room or of room of similar dimension and structure, Td and Ti(t).
In addition, the determination of S(t) can include constraints on the HVAC system(s) 3 such as minimum rest time, minimum run time, energy usage, etc.
An exemplary method is illustrated in
By using the above factors, the system can turn on and off a HVAC system(s) 3 at intervals while attempting to reach the desired adjusted temperature in order to maintain a comfortable environment.
While the invention has been described in terms of exemplary embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims
Further, it is noted that, Applicant's intent is to encompass equivalents of all claim elements, even if amended later during prosecution.
