Patent Description:
Power consumption is a significant cost of operating computer systems, including rackmounted equipment. End users, information technology (IT) providers, and equipment rack vendors often look for ways to improve power usage effectiveness (PUE), in order to reduce total cost of ownership (TCO). Because electronics can generate considerable heat, a significant portion of the power consumption is due to cooling equipment. Air conditioners are one source of significant power consumption.

Approaches described in this section have not necessarily been conceived and/or pursued prior to the filing of this application. Accordingly, unless otherwise indicated, approaches described in this section should not be construed as prior art. Documents <CIT> and <CIT> disclose examples of methods and systems for controlling power consumption according to available prior art.

One or more embodiments improve PUE by selectively cooling inside a rack enclosure based on the external temperature, i.e., the temperature outside the rack enclosure. Specifically, based on the external temperature, one or more embodiments select among different power configurations for cooling components. In some power configurations, one or more fans provide(s) cooling from external air, thus reducing the cooling burden on an air conditioner inside the rack enclosure. In some power configurations, the air conditioner can be powered off. In general, fans consume less power than air conditioners. Thus, one or more embodiments improve PUE, in comparison to techniques that use an air conditioner full-time and do not take advantage of cooling from external air. Reduced power usage may translate to a significant reduction in TCO.

In general, in one aspect there is a computer implemented method according to claim <NUM>. An equipment rack is provided according to claim <NUM>. The operations may further include, when the power status of the air conditioner is on, controlling an intensity of air conditioning to manage a temperature inside the rack enclosure. Controlling the intensity of air conditioning may be performed by the air conditioner, based at least on a reading from a temperature sensor disposed within the rack enclosure. The operations include: receiving temperature and humidity inside the rack enclosure from a temperature and humidity sensor configured to sense the temperature and humidity inside the rack enclosure; and controlling operation of the air conditioner disposed within the rack enclosure, based at least on the temperature and humidity inside the rack enclosure. Controlling the power status of the at least one fan may include controlling power statuses of at least two groups of intake and exhaust fans. The at least one fan may include an exhaust fan and the temperature sensor is disposed near the exhaust fan.

In general, in a non-claimed example, a controller is configured to perform operations including:
receiving a temperature outside a rack enclosure from a temperature sensor configured to sense the temperature outside the rack enclosure; and controlling (a) a power status of at least one fan configured to provide airflow through the rack enclosure and (b) a power status of an air conditioner disposed within the rack enclosure, based at least on the temperature outside the rack enclosure. Controlling the power status of the at least one fan and the power status of the air conditioner disposed within the rack enclosure, based at least on the temperature outside the rack enclosure, may include comparing the temperature outside the rack enclosure with at least one threshold temperature value. The at least one threshold temperature value may include an upper threshold temperature value and a lower threshold temperature value. When the temperature outside the rack enclosure is in an upper range, the power status of the at least one fan may be off and the power status of the air conditioner disposed within the rack enclosure may be on. When the temperature outside the rack enclosure is in a middle range, the power status of the at least one fan may be on and the power status of the air conditioner may be on. When the temperature outside the rack enclosure is in a lower range, the power status of the at least one fan may be on and the power status of the air conditioner may be off. The operations may further include, when the power status of the air conditioner is on, controlling an intensity of air conditioning to manage a temperature inside the rack enclosure. Controlling the intensity of air conditioning may be performed by the air conditioner, based at least on a reading from a temperature sensor disposed within the rack enclosure. The operations may further include: receiving temperature and humidity inside the rack enclosure from a temperature and humidity sensor configured to sense the temperature and humidity inside the rack enclosure; and controlling operation of the air conditioner disposed within the rack enclosure, based at least on the temperature and humidity inside the rack enclosure. Controlling the power status of the at least one fan may include controlling power statuses of at least two groups of intake and exhaust fans. The at least one fan may include an exhaust fan and the temperature sensor is disposed near the exhaust fan.

In general, in one aspect, a system is provided according to claim <NUM>.

The operations may further include, when the power status of the air conditioner is on, controlling an intensity of air conditioning to manage a temperature inside the rack enclosure. Controlling the intensity of air conditioning may be performed by the air conditioner, based at least on a reading from a temperature sensor disposed within the enclosure. The operations include: receiving temperature and humidity inside the enclosure from a temperature and humidity sensor configured to sense the temperature and humidity inside the enclosure; and controlling operation of the air conditioner disposed within the enclosure, based at least on the temperature and humidity inside the enclosure. Controlling the power status of the at least one fan may include controlling power statuses of at least two groups of intake and exhaust fans. The at least one fan may include an intake fan and the temperature sensor configured to sense the temperature outside the enclosure may be disposed near the intake fan.

Various aspects of at least one embodiment are discussed below with reference to the accompanying Figures, which are not intended to be drawn to scale. The Figures are included to provide illustration and a further understanding of the various aspects and embodiments, and are incorporated in and constitute a part of this specification, but are not intended to define the limits of the disclosure. In the Figures, each identical or nearly identical component that is illustrated in various Figures is represented by a like numeral. For the purposes of clarity, some components may not be labeled in every figure. In the Figures:.

Any references to examples, embodiments, components, elements or acts of the systems and methods herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element or act herein may also embrace embodiments including only a singularity. References in the singular or plural form are not intended to limit the presently disclosed systems or methods, their components, acts, or elements. The use herein of "including," "comprising," "having," "containing," "involving," and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to "or" may be construed as inclusive so that any terms described using "or" may indicate any of a single, more than one, and all of the described terms.

<FIG> is a block diagram of an example of an equipment rack <NUM> according to an embodiment. In an embodiment, the equipment rack <NUM> may include more or fewer components than the components illustrated in <FIG>. Components illustrated in <FIG> may be local to or remote from each other. Components illustrated in <FIG> may be implemented in software and/or hardware. Each component may be distributed over multiple applications and/or machines. Multiple components may be combined into one application and/or machine. Operations described with respect to one component may instead be performed by another component. In the following discussion, examples are given with reference to a rack enclosure. In view of the present disclosure, those skilled in the art will appreciate that one or more embodiments may relate to any kind of enclosure for electrical equipment.

In an embodiment, an equipment rack <NUM> refers to an apparatus configured to house one or more rackable components <NUM>. Specifically, the equipment rack <NUM> includes a rack enclosure <NUM> that is designed to house a rackable component <NUM> that is sized according to an industry-wide standard, such as one or more standards defined by the Electronic Industries Alliance (EIA) (e.g., EIA-<NUM>), European Telecommunications Standards Institute (ETSI) (e.g., ETSI <NUM><NUM>), the Open Compute Project (OCP), or another standardizing organization. For example, the rack enclosure <NUM> may be a <NUM>-inch or <NUM>-inch 42U enclosure, a <NUM>-inch or <NUM>-inch 24U enclosure, or another size of enclosure. A rackable component <NUM> may be a 1U unit, 2U unit, 3U unit, 4U unit, or other size of unit. A rackable component <NUM> may be a half-rack component. Alternatively, the rack enclosure <NUM> and rackable component <NUM> may have proprietary sizes that do not conform to any industry-wide standard. Different rackable components <NUM> in the same rack enclosure <NUM> may have different sizes. In an embodiment, the equipment rack <NUM> is a 24U micro-datacenter, such as those manufactured by Schneider Electric SE. The equipment rack <NUM> may be configured to house many different kinds of rackable components <NUM>. For example, a rackable component <NUM> may be a server, telecommunications equipment, networking hardware, audiovisual equipment, scientific equipment, and/or another kind of equipment or combination thereof.

In an embodiment, the equipment rack <NUM> includes components configured to sense the temperatures inside and outside the rack enclosure <NUM>. The equipment rack <NUM> may also include one or more components configured to sense the humidity inside the rack enclosure <NUM>. A temperature and humidity sensor <NUM> may be configured to sense the temperature and humidity inside the rack enclosure <NUM>. Alternatively, an internal temperature sensor (not shown) may be configured to sense only the temperature inside the rack enclosure, without sensing humidity. A humidity sensor (not shown) may be configured to sense only the humidity inside the rack enclosure, without sensing the temperature. The temperature and humidity sensor <NUM> may be part of the controller <NUM>, part of the air conditioner <NUM>, part of another component, or a separate component operatively coupled with one or more other components in the rack enclosure <NUM>. An external temperature sensor <NUM> is configured to sense the temperature outside (i.e., physically external to) the rack enclosure <NUM>. For example, the external temperature sensor <NUM> may be mounted to, or otherwise coupled with, an outside-facing surface of the rack enclosure <NUM>, in order to sense the temperature physically proximate to the rack enclosure <NUM>.

In an embodiment, a controller <NUM> refers to hardware and/or software configured to perform operations described herein for selective rack cooling based on the temperature outside the rack enclosure <NUM>, i.e., based on data from the external temperature sensor <NUM>. Specifically, the controller <NUM> is configured to selectively control the power statuses of an air conditioner <NUM> and one or more fans (e.g., one or more draw fans <NUM> configured to draw air into the rack enclosure <NUM> and/or one or more exhaust fans <NUM> configured to expel air from the rack enclosure <NUM>), based on the external temperature. When the air conditioner <NUM> is powered on, the controller <NUM> may also be configured to control operation of the air conditioner <NUM> (i.e., control an intensity of air conditioning performed by the air conditioner <NUM>), for example, by transmitting temperature and/or humidity setpoints to the air conditioner <NUM>. Alternatively or additionally, the rack enclosure <NUM> may include a proportional-integral-derivative (PID) controller (not shown) configured to control operation of the air conditioner <NUM>, when the air conditioner <NUM> is powered on, to reach a temperature setpoint and/or humidity setpoint. Specifically, the PID controller may determine an intensity of air conditioning performed by the air conditioner <NUM>. The PID controller may be part of the controller <NUM>, part of the air conditioner <NUM>, part of another component, or a separate component operatively coupled with one or more other components in the rack enclosure <NUM> (e.g., the air conditioner <NUM>).

<FIG> is a block diagram of an example of an electrical layout for the equipment rack <NUM> of <FIG> according to an embodiment. The electrical layout illustrated in <FIG> is provided as an example only and should not be construed as limiting one or more embodiments. In an embodiment, an external power supply <NUM> refers to a power supply that is external to the equipment rack <NUM>. For example, the external power supply <NUM> may be a power utility, an uninterruptible power supply (UPS), or another kind of external power source. A rack power distribution unit <NUM> is configured to receive power from the external power supply <NUM> and distribute power to electrical components of the equipment rack <NUM>. In this example, the rack power distribution unit <NUM> distributes power to the rackable component <NUM>, air conditioner <NUM>, draw fan <NUM>, exhaust fan <NUM>, and power supply unit <NUM>. The rack power distribution unit <NUM> may also be configured to monitor power used by components of the equipment rack <NUM>, detect circuit overloads, and/or perform other operations to manage power supplied to components of the equipment rack <NUM>. For example, the rack power distribution unit <NUM> may be a NetShelter Power Distribution Unit (PDU) manufactured by Schneider Electric SE. The power supply unit <NUM> is configured to convert alternating current (AC) to direct current (DC), for use by components that require direct current. For example, the power supply unit <NUM> may be a <NUM> volts direct current power supply unit (24VDC PSU) or another kind of unit. In this example, the power supply unit <NUM> supplies direct current to the controller <NUM> and the temperature and humidity sensor <NUM>. In this example, the external temperature sensor <NUM> requires no more than <NUM> volts, which the controller <NUM> can provide, while the power supply unit <NUM> is configured to supply <NUM> volts. Therefore, in this example, the controller <NUM> is configured to supply power to the external temperature sensor <NUM>.

<FIG> illustrates an example of an equipment rack <NUM> according to an embodiment. The equipment rack <NUM> includes a rack enclosure <NUM> configured to house one or more rack components (not shown). Specifically, the rack enclosure <NUM> includes one or more sets of rails <NUM> configured to accommodate rack components at particular locations within the rack enclosure <NUM>. The inside of the rack enclosure <NUM> is accessible (e.g., to install or remove components) via a front door <NUM> and a back door <NUM>. In this example, the front door <NUM> and back door <NUM> are formed at least partly of glass, for visibility into the rack enclosure <NUM> while helping keep dust out of the rack enclosure <NUM>. A rack power distribution unit <NUM> is configured to receive power from an external power source (not shown) and distribute power to components of the equipment rack <NUM>. A power supply unit <NUM> is configured to convert alternating current to direct current, for components that require direct current.

As illustrated in <FIG>, the equipment rack <NUM> includes various cooling components. Specifically, the equipment rack <NUM> includes an air conditioner <NUM> disposed inside the rack enclosure <NUM>, and two groups of front draw fans <NUM> and top exhaust fans <NUM> that are configured to circulate air through the rack enclosure <NUM>. Other examples (not shown) may use a different number of fans and/or fan groups. A controller <NUM> is configured to control the power statuses of the air conditioner <NUM> and fans <NUM>, <NUM>, based on data from an external temperature sensor <NUM>. In this example, the external temperature sensor <NUM> is located on an outside-facing surface of the rack enclosure <NUM>, adjacent to the exhaust fans <NUM>. Alternatively, the external temperature sensor <NUM> may be located adjacent to the front draw fans <NUM> (or one or more draw fans in another location), to sense the temperature of air that will be drawn into the rack enclosure <NUM>. In addition, a temperature and humidity sensor <NUM> disposed inside the rack enclosure <NUM> is configured to sense the temperature and humidity inside the rack enclosure <NUM>. In <FIG>, the temperature and humidity sensor <NUM> is shown as a separate component. Alternatively, the temperature and humidity sensor <NUM> may be part of the controller <NUM>, part of the air conditioner <NUM>, or part of another component. A PID controller, which in this example is part of the air conditioner <NUM> (but may alternatively be part of the controller <NUM>, part of another component, or a separate component), is configured to control operation of the air conditioner <NUM> (i.e., an intensity of air conditioning), when the air conditioner <NUM> is powered on, based on temperature and humidity data from the temperature and humidity sensor <NUM>.

<FIG> is a flow diagram of an example of operations for selective rack cooling based on external temperature, according to an embodiment. One or more operations illustrated in <FIG> may be modified, rearranged, or omitted all together. Accordingly, the particular sequence of operations illustrated in <FIG> should not be construed as limiting the scope of one or more embodiments.

In the following discussion, the term "controller" may refer to multiple controllers. Specifically, different controller operations described herein may be performed by a single controller or divided between two or more controllers. For example, one controller may be configured to control power statuses of an air conditioner and fan(s), while a separate controller (e.g., a PID controller that is part of the air conditioner or another component) may be configured to control an intensity of air conditioning.

In an embodiment, selective rack cooling based on external temperature relies on the general observation that fans consume less power than air conditioners. In addition, external air (i.e., air that is outside of the rack enclosure) may be cold enough to help cool components inside the rack enclosure. Whether the external air is cold enough may depend, for example, on factors such as the season, weather, cooling provided by a building that houses the equipment rack, etc. The external temperature may vary over time. Accordingly, one or more embodiments use the external temperature to determine when to use an air conditioner and when to use fan cooling to take advantage of cold external air.

In an embodiment, a controller in an equipment rack receives an external temperature from an external temperature sensor (Operation <NUM>). Based on the external temperature, the controller controls the power statuses of one or more fans (Operation <NUM>) and an air conditioner (Operation <NUM>). Specifically, based on the external temperature, the controller may determine whether the fan(s) alone should be powered on, the air conditioner alone should be powered on, or both the fan(s) and the air conditioner should be powered on. As used in this context, the terms "powered on" and "powered off' refer to whether the fan(s) and/or air conditioner are actively providing cooling capabilities and may not indicate a complete lack of power supplied to the fan(s) and/or the air conditioner. Some power may still be supplied to a fan or air conditioner that is "powered off. " For example, a fan that is "powered off" may still receive some power even though it is not rotating, and an air conditioner that is "powered off" may still receive some power even though it is not cooling the air inside the rack enclosure.

<FIG> is a flow diagram of an example of operations for controlling fan and air conditioner power statuses based on external temperature (i.e., Operations <NUM> and <NUM> of <FIG>), according to an embodiment. One or more operations illustrated in <FIG> may be modified, rearranged, or omitted all together. For example, while <FIG> illustrates an external temperature being compared to an upper range, middle range, and lower range, such comparisons may be performed in a different order. In addition, as discussed below, more or fewer temperature thresholds and/or ranges may be used. Accordingly, the particular sequence of operations illustrated in <FIG> should not be construed as limiting the scope of one or more embodiments.

In an embodiment, the controller determines a high temperature threshold, abbreviated here as "TH" (Operation <NUM>). TH defines the lower boundary of an upper range of external temperatures, above which the air conditioner should be powered on and the fan(s) should be powered off. TH may be inclusive, i.e., the air conditioner should be powered on and the fan(s) should be powered off when the external temperature is greater than or equal to TH. Alternatively, TH may be exclusive, i.e., the air conditioner should be powered on and the fan(s) should be powered off when the external temperature is greater than TH. The upper range of temperatures may not have an upper limit. TH may be hard-coded into the controller's logical components (i.e., hardware and/or software). Alternatively, TH may be configurable, for example via a user interface that is configured to receive user input to configure cooling parameters of the equipment rack.

In an embodiment, the controller determines a low temperature threshold, abbreviated here as "TL" (Operation <NUM>). TL defines the upper boundary of a lower range of external temperatures, below which the air conditioner should be powered off and the fan(s) should be powered on. TL may be inclusive, i.e., the air conditioner should be powered off and the fans should be powered on when the external temperature is less than or equal to TL. Alternatively, TL may be exclusive, i.e., the air conditioner should be turned off and the fans should be powered on when the external temperature is less than TL. The lower range of temperatures may not have a lower limit. TL may be hard-coded into the controller's logical components (i.e., hardware and/or software). Alternatively, TL may be configurable, for example via a user interface that is configured to receive user input to configure cooling parameters of the equipment rack.

In an embodiment, the controller compares the external temperature with the threshold temperatures TH and TL (Operation <NUM>). Based on the comparison, the controller determines the power statuses of the fan(s) and air conditioner, and sets the power statuses accordingly via one or more electrical signals. If a fan or air conditioner is already in the appropriate power status, then the controller may not transmit an electrical signal to that component. The controller may track the current power statuses of the fan(s) and air conditioner (e.g., in one or more software variables, one or more hardware registers, and/or one or more other locations) and transmit an electric signal only when a change in power status is needed.

In an embodiment, if the external temperature is in the upper range (Decision <NUM>), then the controller powers on the air conditioner and power off the fan(s) (Operation <NUM>). When the external temperature is in the upper range, the external air is not cold enough to help with cooling. Accordingly, this configuration of power statuses avoids drawing in air from the external environment into the rack enclosure, while cooling the rack enclosure using the air conditioner. Because this power configuration relies entirely on the air conditioner, it uses more power than configurations that are able to also provide cooling from external air. Therefore, one or more embodiments can reduce power consumption by using this power configuration only when needed, i.e., when the external temperature is in the upper range.

In an embodiment, if the external temperature is in a middle range, i.e., between the upper range and the lower range (Decision <NUM>), then the controller powers on the air conditioner and powers on the fan(s) (Operation <NUM>). When the external temperature is in the middle range, the external air is cold enough to help with cooling, but not cold enough to provide all the cooling needed. Accordingly, this configuration of power statuses uses the fan(s) to provide cooling from external air, while also using the air conditioner to supply additional cooling. Because the external air is cold enough to partially alleviate the cooling burden placed on the air conditioner, one or more embodiments can reduce power consumption when the external temperature is in the middle range, in comparison to relying exclusively on the air conditioner.

In an embodiment, if the external temperature is in the lower range (Decision <NUM>), then the controller powers off the air conditioner and powers on the fan(s) (Operation <NUM>). In the lower range of external temperatures, the external air provided by the fan(s) is cold enough to provide all the cooling needed, and the air conditioner is not needed. Therefore, one or more embodiments can reduce power consumption when the external temperature is in the lower range, by taking advantage of cold external air and powering off the air conditioner.

While the example illustrated in <FIG> uses two threshold temperatures, one or more embodiments may use more than two threshold temperatures. For example, a rack enclosure may include multiple air conditioners. The controller may use multiple tiers of middle ranges to determine which and/or how many of the air conditioners to power on, with more air conditioners being powered on at higher temperatures. As another example, an air conditioner may have multiple power settings corresponding to different cooling intensities. The controller may use multiple tiers of middle ranges to determine which air conditioner power setting to use, with higher-intensity settings used at higher temperatures. Alternatively, the controller may use only a single threshold temperature, defining an upper range and an external range. For example, when the external temperature is in the upper range, the controller may power on the air conditioner and power off the fan(s). When the external temperature is in the lower range, the controller may power off the air conditioner and power on the fan(s), or power on both the air conditioner and the fan(s). Embodiments should not be considered limited to the particular thresholds and ranges illustrated in <FIG>.

Returning to <FIG>, in power configurations where the air conditioner is powered on (e.g., the upper and middle ranges of external temperatures, in the example illustrated in <FIG>), a controller (e.g., the same controller used to control power statuses and/or a separate PID controller) may control operation of the air conditioner (i.e., an intensity of air conditioning). In an embodiment, the controller determines whether the air conditioner is currently powered on (Decision <NUM>). In addition, the controller receives the temperature and humidity inside the rack enclosure (Operation <NUM>), e.g., from a temperature and humidity sensor as discussed above. The controller may receive the temperature and humidity on an ongoing basis, whether or not the air conditioner is powered on. Alternatively, the controller may receive the temperature and humidity only when the air conditioner is powered on. In an embodiment, the controller controls the air conditioner's cooling and dehumidifying based on the temperature and humidity inside the rack enclosure (Operation <NUM>). For example, the controller may use one or more feedback loops to control the intensities of cooling and dehumidifying, based on temperature and humidity setpoints. In other examples, the controller may control only the intensity of cooling, or only the intensity of dehumidifying.

In an embodiment, the controller continues to receive the external temperature (Operation <NUM>) on an ongoing basis (for example, at regular intervals and/or when requested by the controller) and adjusts the power statuses of the fan(s) and air conditioner as external temperature conditions change over time. Thus, one or more embodiments help ensure that the air conditioner is used only when needed, relying more on the fan(s) to reduce power consumption when the external temperature is sufficiently cold.

In an embodiment, a system includes one or more devices, including one or more hardware processors, that are configured to perform any of the operations described herein and/or recited in any of the claims.

In an embodiment, one or more non-transitory computer-readable storage media store instructions that, when executed by one or more hardware processors, cause performance of any of the operations described herein and/or recited in any of the claims.

Any combination of the features and functionalities described herein may be used in accordance with an embodiment. In the foregoing specification, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the Applicant to be the scope of the invention, is the literal and equivalent scope of the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.

In an embodiment, techniques described herein are implemented by one or more special-purpose computing devices (i.e., computing devices specially configured to perform certain functionality). The special-purpose computing device(s) may be hard-wired to perform the techniques and/or may include digital electronic devices such as one or more application-specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), and/or network processing units (NPUs) that are persistently programmed to perform the techniques. Alternatively or additionally, a computing device may include one or more general-purpose hardware processors programmed to perform the techniques pursuant to program instructions in firmware, memory, and/or other storage. Alternatively or additionally, a special-purpose computing device may combine custom hard-wired logic, ASICs, FPGAs, or NPUs with custom programming to accomplish the techniques. A special-purpose computing device may include a desktop computer system, portable computer system, handheld device, networking device, and/or any other device(s) incorporating hard-wired and/or program logic to implement the techniques.

For example, <FIG> is a block diagram of an example of a computer system <NUM> according to an embodiment. Computer system <NUM> includes a bus <NUM> or other communication mechanism for communicating information, and a hardware processor <NUM> coupled with the bus <NUM> for processing information. Hardware processor <NUM> may be a general-purpose microprocessor.

Such instructions, when stored in one or more non-transitory storage media accessible to processor <NUM>, render computer system <NUM> into a special-purpose machine that is customized to perform the operations specified in the instructions.

Computer system <NUM> may be coupled via bus <NUM> to a display <NUM>, such as a liquid crystal display (LCD), plasma display, electronic ink display, cathode ray tube (CRT) monitor, or any other kind of device for displaying information to a computer user. An input device <NUM>, including alphanumeric and other keys, may be coupled to bus <NUM> for communicating information and command selections to processor <NUM>. Alternatively or additionally, computer system <NUM> may receive user input via a cursor control <NUM>, such as a mouse, a trackball, a trackpad, or cursor direction keys for communicating direction information and command selections to processor <NUM> and for controlling cursor movement on display <NUM>. Alternatively or additionally, computer system <NUM> may include a touchscreen. Display <NUM> may be configured to receive user input via one or more pressure-sensitive sensors, multi-touch sensors, and/or gesture sensors. Alternatively or additionally, computer system <NUM> may receive user input via a microphone, video camera, and/or some other kind of user input device (not shown).

Computer system <NUM> may implement the techniques described herein using customized hard-wired logic, one or more ASICs or FPGAs, firmware, and/or program logic which in combination with other components of computer system <NUM> causes or programs computer system <NUM> to be a special-purpose machine. Alternatively or additionally, hard-wired circuitry may be used in place of or in combination with software instructions.

The term "storage media" as used herein refers to one or more non-transitory media storing data and/or instructions that cause a machine to operate in a specific fashion. Common forms of storage media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape or other magnetic data storage medium, a CD-ROM or any other optical data storage medium, any physical medium with patterns of holes, a RAM, a programmable read-only memory (PROM), an erasable PROM (EPROM), a FLASH-EPROM, non-volatile random-access memory (NVRAM), any other memory chip or cartridge, content-addressable memory (CAM), and ternary content-addressable memory (TCAM).

A storage medium is distinct from but may be used in conjunction with a transmission medium. Transmission media participate in transferring information between storage media. Examples of transmission media include coaxial cables, copper wire, and fiber optics, including the wires that comprise bus <NUM>. Transmission media may also take the form of acoustic or light waves, such as those generated during radio-wave and infra-red data communications.

The remote computer may load the instructions into its dynamic memory and send the instructions over a network, via a network interface controller (NIC), such as an Ethernet controller or Wi-Fi controller. A NIC local to computer system <NUM> may receive the data from the network and place the data on bus <NUM>.

In the Internet example, a server <NUM> might transmit a requested code for an application program through Internet <NUM>, ISP <NUM>, local network <NUM>, and communication interface <NUM>.

Claim 1:
A computer implemented method, when run on a controller, comprising the steps of:
determining an upper threshold temperature;
determining a lower threshold temperature;
receiving a temperature outside a rack enclosure (<NUM>) from a temperature sensor configured to sense the temperature outside the rack enclosure;
when the temperature outside the rack enclosure is greater than or equal/greater than said upper threshold temperature powering on an air conditioner (<NUM>) disposed within the rack enclosure and powering off at least one fan (<NUM>, <NUM>) configured to provide airflow through the rack enclosure, and
when the temperature outside the rack enclosure is less than or equal/less than said lower threshold temperature powering off the air conditioner, and powering on the at least one fan; and characterised by comprising the steps of:
receiving temperature and humidity inside the rack enclosure from a temperature and humidity sensor (<NUM>) configured to sense the temperature and humidity inside the rack enclosure; and
controlling operation of the air conditioner disposed within the rack enclosure, based at least on the temperature and humidity inside the rack enclosure.