Equipment shelf

An equipment shelf includes at least one power supply unit (PSU) positioned in an upper region of the equipment shelf. The equipment shelf also includes at least one battery backup unit (BBU) positioned in a lower region of the equipment shelf. An airflow path extends through the equipment shelf between the upper region and the lower region. The airflow path separates the upper region of the equipment shelf from the lower region of the equipment shelf and thermally isolates the at least one PSU in the upper region from the at least one BBU in the lower region when air flows through the airflow path. Other example equipment shelves are also disclosed.

FIELD

The present disclosure relates to an equipment shelf, and in particular, an equipment shelf enabling enhanced thermal performance of equipment stored thereon.

BACKGROUND

Various electronic equipment is commonly mounted in racks, for example at data centers, to compactly house the electronic equipment during operation and use of the electronic equipment. The electronic equipment may be included in a shelf that is mounted in the rack. Some electronic equipment is known to generate heat during operation and some electronic equipment is known to be temperature-sensitive such that the equipment performs better under certain temperature conditions.

SUMMARY

According to one aspect of the present disclosure, an equipment shelf includes at least one power supply unit (PSU) positioned in an upper region of the equipment shelf. The equipment shelf also includes at least one battery backup unit (BBU) positioned in a lower region of the equipment shelf. An airflow path extends through the equipment shelf between the upper region and the lower region. The airflow path separates the upper region of the equipment shelf from the lower region of the equipment shelf and thermally isolates the at least one PSU in the upper region from the at least one BBU in the lower region when air flows through the airflow path.

According to another aspect of the present disclosure, a power shelf includes an enclosure having a plurality of upper receptacles and a plurality of lower receptacles. The power shelf also includes multiple power supply units (PSUs) positioned within the plurality of upper receptacles and multiple battery back-up units (BBUs) positioned within the plurality of lower receptacles. The power shelf also includes an airflow region between the multiple PSUs and the multiple BBUs.

According to another aspect of the present disclosure, a rack-mounted equipment shelf includes an enclosure having at least one receptacle for housing electronic equipment. The equipment shelf also includes electronic equipment positioned within the at least one receptacle. A channel is coupled to the enclosure and at least one fan is coupled to the channel to draw air through the channel, whereby the air drawn through the channel maintains the electronic equipment and/or the shelf at a desired temperature.

Corresponding reference numerals indicate corresponding parts or features throughout the several views of the drawings.

DETAILED DESCRIPTION

An equipment shelf according to one example embodiment of the present disclosure is illustrated inFIG. 1and indicated generally by reference number100. The equipment shelf100includes an enclosure102for supporting and/or housing electronic equipment within the equipment shelf100. The electronic equipment includes various electronic equipment such as heat-generating equipment (e.g., electronic equipment with a high heat loss density and a high operating temperature) and/or thermally-sensitive equipment (e.g., electronic equipment whose performance is impacted by temperature (e.g., precision control devices, measurement devices, battery devices, etc.)). The enclosure102is configured to support and/or house the electronic equipment during operation and use of the electronic equipment.

As shown inFIG. 1, the equipment shelf100includes both heat-generating equipment and temperature-sensitive equipment. In other embodiments, an equipment shelf may include only heat-generating equipment or only temperature-sensitive equipment. In the illustrated embodiment, the equipment shelf100is configured as a power shelf. As shown inFIG. 1, a power supply unit (PSU)104and a battery back-up unit (BBU)106are included within the equipment shelf100. Although only one PSU104and only one BBU106are illustrated inFIG. 1, the equipment shelf100may include multiple PSUs104and multiple BBUs106. In some embodiments, the equipment shelf100includes an equal number of PSUs104and BBUs (e.g., six PSUs104and six BBUs106, three PSUs104and three BBUs106, etc.). The PSU104is an example of heat-generating equipment as the PSU104generates heat within enclosure102during operation and has a high heat loss density and a high operating temperature. The BBU106is equipment that is sensitive to temperature (e.g., high temperatures) during operation. For example, temperature is a critical parameter for BBUs affecting functionality of the battery such as performance and battery life.

As shown inFIG. 1, PSU104is included in an upper region108of the equipment shelf100and BBU106is included in a lower region110of the equipment shelf100. In alternate embodiments, PSU104is positioned within the lower region110and BBU106is positioned in the upper region108. In general, heat-generating equipment is included in a separate region of the equipment shelf100than any temperature-sensitive equipment.

To support the electronic equipment included in the upper region108, the enclosure102of the equipment shelf100includes a partition or support plate112in the upper region108. The support plate112generally divides the equipment shelf100along a mid-plane of equipment shelf100. Equipment in the upper region108of the equipment shelf100may be positioned on the support plate112of the enclosure102. In the illustrated embodiment, the PSU104is positioned within the upper region108and coupled to support plate112.

The equipment shelf100includes an airflow region114(e.g., a channel, a gap, etc.) to permit moving air to flow through the equipment shelf100. The airflow region114is positioned between the upper region108and the lower region110of the equipment shelf100. In this way, the air moving through the airflow region114thermally isolates the equipment included in the upper region108(e.g., one or more PSUs104) from equipment included in the lower region110(e.g., one or more BBUs108). For example, the airflow region114thermally isolates the heat-generating equipment (e.g., PSUs104) from the temperature-sensitive equipment (e.g., BBUs106).

The airflow region114is defined by and extends vertically between the support plate112of the upper region108and a secondary plate116that is configured to retain the BBU106within the enclosure102. In some embodiments, the secondary plate116is omitted, such that the airflow region114is defined by the support plate112and an upper surface of the BBU106. In these embodiments, other features may be included to retain the BBU106within the enclosure102.

The height h of the airflow region114is generally sized to permit air to flow through the airflow region114and thermally isolate the equipment in the upper region108from equipment in the lower region110. The height h may be adjusted based on the equipment included in the equipment shelf100, the operating conditions/parameters of such equipment, the overall equipment shelf height requirements, environmental factors such as ambient temperature, etc. Size considerations of the airflow region114are discussed in more detail below.

As shown inFIG. 1, the airflow region114generally extends horizontally along at least a length of the equipment (e.g., PSUs104and BBUs106) in equipment shelf100, through a mid-plane of the equipment shelf100. In the example embodiment, the airflow region114is positioned above a center of the equipment shelf100due to the sizing of the equipment in the lower region110. As can be appreciated, the airflow region114may be adjusted higher or lower (e.g., with respect to a bottom of the enclosure102(e.g., bottom plate136shown inFIG. 4)) depending on the size of the equipment in the upper region108and the lower region110. In this way, the airflow region114extends generally through a mid-plane of the equipment shelf100that passes between the equipment in the upper region108(e.g., PSU104) and the equipment in the lower region110(e.g., BBU106), whereby moving air (e.g., ambient air) passes between the upper region108and the lower region110to thermally isolate the two regions.

The equipment shelf100also includes at least one fan118. As shown inFIG. 2, the equipment shelf100includes two fans118. In some embodiments, a greater or lesser number of fans118may be included in the equipment shelf100. In the illustrated embodiment, the fan118is generally coupled to the airflow region114(e.g., indirectly coupled) and mounted on the equipment shelf100at a first end120(e.g., a rear end) of the equipment shelf100. The fan118is configured to draw air through airflow region114from a second end122(e.g., a front end) of the equipment shelf100. In alternate embodiments, one or more fans118may be located at other positions on or within the equipment shelf100(e.g., at a front end122of the enclosure102) and/or provided on the rack (not shown). The air drawn into the airflow region114by the fan118is generally at an ambient temperature. This ambient temperature is relatively cool in comparison to a temperature of the heat-generating PSUs104included within the equipment shelf100. As the ambient temperature passes through the airflow region114, the flowing air thermally isolates the upper and lower regions108,110and generally lowers the temperature of any structure or equipment defining the airflow region114(e.g., at a boundary or edge of the airflow region114). In this way, rather than cooling the equipment shelf100in a general manner, the fan118included in this embodiment creates a directed air stream through the airflow region114of the equipment shelf100to thermally de-couple portions of the equipment included within the equipment shelf100(e.g., heat-generating equipment is de-coupled from thermally-sensitive equipment).

With continued reference toFIG. 1, arrows124generally indicate the path of air flowing through the equipment shelf100(e.g., through the airflow region114and a rear portion126of the equipment shelf100). As shown inFIG. 1, the air flowing through the airflow region114follows a single path, as indicated by arrows124, through the equipment shelf100. For example, the air flows from the front end122of the equipment shelf100through the airflow region114to the rear portion126of the equipment shelf100(e.g., an area of the equipment shelf100behind the PSUs104and BBUs106) where the air then flows out of the rear end120of the equipment shelf100as drawn by fan118. As can be appreciated, the ambient air moving through the airflow region114enables thermal isolation of the BBU106in the lower region110from heating by the PSU104in the upper region108, thus allowing the BBU106to operate at lower temperatures which improves BBU106performance.

In the illustrated embodiment, rather than enabling air to flow through the equipment shelf100in multiple different directions (e.g., along multiple different paths), the airflow region114generally enables air to pass through the equipment shelf100in a single direction from a lower temperature, or cool, side of the equipment shelf100to a higher temperature, or hot, side of the equipment shelf100(e.g., from the front end122to the rear end120). In alternate embodiments, the airflow region114may enable air to pass through the equipment shelf100from the rear end120to the front end122(e.g., where the rear end120is the cool side and the front end122is the hot side of the equipment shelf100). The use of a single airflow path (e.g., as shown by arrows124) simplifies the design of the equipment shelf100as well as minimizes the airflow impedance of the equipment shelf100. By minimizing airflow impedance (e.g., by utilizing a single airflow path), maximum airflow is achieved for a given fan. In addition, the single airflow path (e.g., as shown by arrows124) enables use of a quieter, slower, less expensive, etc. fan for a given airflow due to the minimized airflow impedance. For example, a more powerful, louder, and/or more expensive fan (or multiple fans) would be required when multiple airflow paths are included in an equipment shelf due to the increased airflow impedance caused by the multiple paths.

As shown inFIGS. 1 and 2, the equipment shelf100includes one or more baffles128,130to further define the path for the air moving through the equipment shelf100(e.g., to guide the air exiting the airflow region114through the rear portion126towards the rear end120of the equipment shelf100). Baffles128,130limit and/or inhibit the mixing of air exhausted by the equipment in the upper region108from the air exiting the airflow region114. When heat-generating equipment (e.g., one or more PSUs104) is included in the upper region108, such equipment generates heat which is generally exhausted from the equipment. To prevent this exhausted hot air from mixing with the air (e.g., ambient air) drawn through the airflow region108, baffles128and130are positioned in such a manner as to block any airflow between the PSUs104and the fans118.

Generally, baffles128and130are positioned between the upper region108of the equipment shelf100and the airflow region114to separate the upper region108from the airflow region114(e.g., air exiting the airflow region). The baffles128,120are positioned within the rear portion126of the equipment shelf100(e.g., behind the PSUs104and BBUs106in the equipment shelf100). In the example embodiment, baffle128is coupled to the support plate112of the enclosure102towards the rear end120of the equipment shelf100and baffle130is coupled to the equipment shelf100, at the rear end120of the equipment shelf100, above the fan118. In this way, the baffles123,130are positioned to block airflow between the PSUs104and fans118. Baffles128,130may also seal against other electronics included in the rear portion126of the equipment shelf100(e.g., a backplane PCB) to inhibit airflow mixing. In other embodiments, a greater or lesser number of baffles may be used, positioned in similar or different configurations, to inhibit PSU exhaust from mixing with ambient air drawn through the airflow region114.

In some embodiments, however, baffles128and130are not included in the equipment shelf100.FIG. 3illustrates a temperature map of the equipment shelf100that does not include baffles128,130. The temperature map depicts temperatures of equipment and air within equipment shelf100while operating at steady state condition, at sea level, with an ambient air temperature of 40° C. As shown inFIG. 3, the temperature of the PSU104is generally higher than the temperature of the BBU106. In particular, the temperature towards the back of the BBU106is 46.2° C. Because baffles128and130are not included in this embodiment, airflow mixing is present within the rear portion126of the equipment shelf100(e.g., towards the rear end120of the equipment shelf100), resulting in a temperature that is between the temperature of the equipment in the upper region108and the temperature of the equipment in the lower region110. For example, in the rear portion126near the fan118(e.g., where at least a portion of the air exits the equipment shelf100), the temperature is 59.0° C. which is 12.8° C. higher than at the back of the BBU106. In addition, the internal components of the PSU104are at different temperatures, including temperatures up to 110° C. The temperature of the air exiting the rear of the PSU104is approximately 60° C. to 65° C.

As shown inFIG. 4, the equipment shelf100includes multiple PSUs104and multiple BBUs106. In particular, six PSUs104are included in the enclosure102in the upper region108of the equipment shelf100and six BBUs106are included in the enclosure102in the lower region110of the equipment shelf100. In alternate embodiments, a greater or lesser number of PSUs104and BBUs106may be included in the equipment shelf100. In the exemplary embodiment, each PSU104is positioned in a receptacle132of the enclosure102in the upper region108of the equipment shelf100. The upper receptacles132are defined in part by support plate112and walls134of the enclosure102. Walls134generally extend from a bottom plate136of the enclosure102to the top of the enclosure102. Each BBU106is positioned in a receptacle138of the enclosure102in the lower region110of the equipment shelf100. The lower receptacles138are defined by the bottom plate136, the secondary plate116, and walls134. In this way, enclosure102includes two rows of receptacles: an upper row of receptacles132and a lower row of receptacles138.

In some embodiments, the enclosure102includes only one row of receptacles (e.g., receptacles132) for housing and/or receiving electronic equipment. In these embodiments, the airflow region114(e.g., configured as a channel) is coupled to either an upper surface of the enclosure102or the lower plate136of the enclosure102. For example, when the airflow region114is coupled to the lower plate136of the enclosure102, the lower plate136defines an upper surface defining the airflow region114(e.g., similar to support plate112) and another plate (e.g., similar to secondary plate116) is positioned below the airflow region114to further define the airflow region114. In these embodiments, the equipment in the enclosure102may be heat-generating equipment and/or temperature-sensitive equipment and the airflow region114may be configured to generally lower the temperature of any structure or equipment defining the airflow region114(e.g., at a boundary or edge of the airflow region114).

In some embodiments, walls136divide the airflow region114into multiple channels (e.g., six channels). Each channel of the airflow region114corresponds to a pair of one PSU104and one BBU106(e.g., a corresponding pair of PSUs104and BBUs106). For example, each channel of the airflow region114is positioned between one PSU104and one BBU106. The multiple channels of the airflow region114are parallel and permit air (e.g., at ambient temperature) to flow between PSUs104and BBUs106through the multiple channels in the same direction from a cool side of the equipment shelf100to a hot side of the equipment shelf100(e.g., from the front end122to the rear end120, from the rear end120to the front end122, etc.). In some embodiments, a filter (not shown) is coupled to the equipment shelf100to prevent dust, debris etc. from entering the equipment shelf100through the airflow region114. In some embodiments, the equipment shelf100is generally rack-mounted such that one or more equipment shelves100may be mounted in a rack (not shown), for example, at a data center.

In another example embodiment, a power supply unit and an enclosure may both be modified to provide air into an airflow region. For example, in this embodiment, air may be provided to the airflow region from the modified power supply unit (e.g., from cooling air circulating through the power supply unit). A modified power supply unit (PSU) is illustrated inFIGS. 5A-5Band is indicated generally by reference number204. As shown inFIGS. 5A-5B, the PSU204includes a case240surrounding the internal components of the PSU204. The PSU204includes an internal fan (not shown) for cooling the PSU204. In general, the internal fan of the PSU204enables cooling air to pass through the PSU204. In the exemplary embodiment, the case240includes an air vent242in the case240(e.g., in a bottom surface of the case240). The air vent242is positioned adjacent to the internal fan such that a portion of the cooling air flowing through the PSU204is diverted through the air vent242and into airflow region114. The air vent242may comprise an opening, a grate, a grille, etc. for permitting the portion of diverted cooling air to exit the PSU204and enter airflow region114.

A modified enclosure is illustrated inFIG. 6and is indicated generally by reference number202. As shown inFIG. 6, the modified enclosure202is similar to the enclosure102, however, the modified enclosure202further includes an opening244in a support plate212of the enclosure202. Similar to enclosure102, enclosure202includes an upper region208including upper receptacles232for receiving electronic equipment (e.g., PSUs204). Enclosure202also includes a lower region210including lower receptacles238for receiving electronic equipment (e.g., BBUs106). In this way, the enclosure202is configured, via opening244, to permit cooling air diverted from PSU204into the airflow region114(not shown inFIG. 6) positioned below the support plate212. Although not shown inFIG. 6, enclosure202may include a plate such as secondary plate116to further define the airflow region114that extends through enclosure202.

FIGS. 7A-7Billustrate another exemplary embodiment of an equipment shelf200that includes the modified enclosure202and at least one modified PSU204and at least one BBU106positioned within the modified enclosure202. As shown inFIG. 7A, a PSU204is included in one of the upper receptacles232of the enclosure202. For illustration purposes, the central lower receptacle238is not occupied by electronic equipment (e.g., a BBU106) and the secondary plate116is not shown.FIG. 7Billustrates a view through the unoccupied receptacle238towards the support plate212of the upper receptacle232and the PSU204. As shown inFIG. 7B, the opening244of the support plate212of enclosure202is generally larger than air vent242of PSU204and, in the illustrated embodiment, is generally rectangular in shape. In this way, the case240of PSU204is partially visible through the opening244, when viewed through the unoccupied receptacle238. Alternatively, the opening244may configured as other shapes (e.g., circular, square, etc.) and/or other sizes (e.g., as the same size as the air vent242of the PSU204, smaller than the air vent242, etc.). The air vent242of PSU204and the opening244of enclosure202enable a portion of cooling air to be diverted from the PSU204to flow through the airflow region114.

FIG. 8illustrates a flow diagram of airflow through the equipment shelf200. As shown, a portion of cooling air flowing through PSU204, as propelled by the internal fan (not shown) of PSU204, is diverted through air vent242and into airflow region114. As the portion of cooling air moves through the airflow region114, the BBU106included in the equipment shelf200is thermally isolated from the heat-generating PSU204. This cooling air also generally lowers the temperature of any structure or equipment defining the airflow region114(e.g., at a boundary or edge of the airflow region214). Because the cooling air flowing through airflow region114cools the BBU106, the BBU106is able to operate at lower temperatures, resulting in improved BBU performance. As such, equipment shelf200induces airflow through the airflow region114through the use of a fan included in the PSU204, whereas the equipment shelf100induces airflow through the airflow region114through one or more fans118included on the equipment shelf100.

In some embodiments, equipment shelf200also includes at least one baffle (similar to baffles128and130). In these embodiments, the at least one baffle is configured to guide air from the airflow region114towards a rear end of the equipment shelf200and inhibit airflow mixing of exhaust from PSU204with air from the airflow region114.

As shown in the following tables andFIGS. 9-11, varying the size (e.g., height) of an airflow region or channel within an equipment shelf impacts the temperature of equipment within the shelf. In particular, with respect to BBUs within the equipment shelf, varying the height of the airflow region enables the BBU to operate at lower temperatures which improves performance and functionality of the BBU. Table 1 characterizes the effect of varying the height (e.g., h as shown inFIG. 1) of a channel (e.g., airflow region114, airflow region214) within an equipment shelf (e.g., equipment shelf100, equipment shelf200) on the temperature of the battery back-up unit (e.g., BBU106) (as measured at a case surrounding internal components of a BBU). As shown in Table 1, the temperature of the case of the battery back-up unit (e.g., BBU106) was taken at the front of the case and at the rear of the case, in Celsius (° C.). The temperature of a power shelf controller (PSC) located in a rear portion of the equipment shelf was also measured, in Celsius (° C.). Table 1 also includes the speed of airflow through the channel (e.g., airflow region114, airflow region214), in units of cubic feet per minute (CFM). The values provided in Table 1 represent values obtained during simulated operation of an equipment shelf including a channel and rear fans (e.g., fans118), with an output power of 18 kW, an input of 180 Vac, an ambient air temperature of 40° C., and exhaust from the PSU (e.g., PSU104) at approximately 65° C. In the simulated embodiment, the equipment shelf does not include baffles (e.g., baffles128,130) and the PSU is not modified (e.g., PSU104included rather than PSU204). As shown in Table 1, generally as the height (i.e., height h) of the channel is increased, the temperature of the battery back-up unit decreased.

Similar to Table 1, Table 2 characterizes the effect of varying the height (e.g., has shown inFIG. 1) of the channel (e.g., airflow region114, airflow region214) on the temperature of the case of the battery back-up unit (e.g., BBU106). The values provided in Table 2 represent values obtained during simulated operation of an equipment shelf including a channel and rear fans (e.g., fans118), with an output power of 18 kW, an input of 240 Vac, an ambient air temperature of 40° C., and exhaust from the PSU (e.g., PSU104) at approximately 61° C. Similar to the equipment shelf model of Table 1, the equipment shelf of this simulation does not include baffles (e.g., baffles128,130) and includes a PSU similar to PSU104, rather than PSU204. As shown in Table 2, the temperature of the case of the battery back-up unit (e.g., BBU106) was taken at the front of the case and at the rear of the case, in Celsius (° C.). The temperature of the power shelf controller (PSC) was also measured, in Celsius (° C.). Table 2 also includes the speed of airflow through the channel (e.g., airflow region114, airflow region214), in units of cubic feet per minute (CFM). As shown in Table 2, generally as the gap size (i.e., height h) of the airflow region is increased, the temperature of the battery back-up unit decreased.

FIG. 9graphically illustrates the effect of increasing the height h of the channel (e.g., airflow region114,214) (also referred to herein as gap size) to the temperature at the rear portion of the BBU106case, using values from Tables 1 and 2. As shown inFIG. 9, as the gap size increases, the temperature of the rear portion of the BBU case decreases, regardless of the operating conditions of the power shelf (e.g., regardless of whether the 18 kW power shelf is operating with a 180 Vac input (and approximately 65° C. PSU exhaust) or a 240 Vac input (and approximately 61° C. PSU exhaust)). As gap sizes are increased (e.g., taller airflow regions), further reductions in temperature may be achieved. It can be appreciated that it may be necessary to balance such further reductions in temperature with overall size constraints and/or size concerns for the equipment shelf.

FIG. 10graphically illustrates the temperature of a battery backup unit in several equipment shelves10,20,30. Equipment shelves10,20, and30do not have certain features included in equipment shelf100. For example, the values illustrated inFIG. 10were obtained from equipment shelves including multiple power supply units and multiple battery backup units positioned within the equipment shelf. The PSUs included in the reference equipment shelves10,20,30are similar to PSUs104(e.g., are not modified similar to PSUs204). Further, the PSUs included in the reference equipment shelves10,20,30are positioned directly on top of the BBUs (e.g., such that there is no gap between the PSUs and the BBUs). In contrast to equipment shelf100, the reference equipment shelves do not include an airflow region (e.g., such as airflow region114) such that the PSUs are not thermally isolated from the BBUs. The reference equipment shelves likewise did not include baffles (such as baffles128,130) or rear fans (such as fans118).

During normal operating conditions of the reference equipment shelves, the PSUs generate heat inside of the equipment shelf and conduct at least a portion of that heat to the BBUs. Due to the heat generated by the PSUs, the temperature of the BBUs increases and puts the BBUs at risk of reaching (and exceeding) an over-temperature protection (OTP) limit. When the temperature has exceeded a safe value, OTP initiates a shutdown process to prevent malfunctioning or damage to the equipment. As shown inFIG. 10, the temperature of the BBUs of three equipment shelves10,20,30were measured during different modes of operation including at steady state, after a discharge period of three minutes, during and after an OTP recovery period, during a charge period, and again once the equipment shelves returned to steady state. As shown inFIG. 10, the OTP discharge limit for the equipment shelf is 65° C., the OTP charging limit for the equipment shelf is 50° C., and the OTP recovery temperature is 47° C.

A first reference equipment shelf10has an output power of 18 kW, a PSU fan speed of 27,000 rpm, and a charge current of 3.0 A that operated in an environment with an ambient air temperature of 40° C. As shown, at the start of testing, the BBUs of this equipment shelf10operated at a temperature of 56° C. During the discharge period, the BBUs of the equipment shelf10met the OTP discharge limit and eventually returned to their starting temperature, a temperature above the OTP recovery temperature. Because the BBUs of the first tested equipment shelf10did not return to the OTP recovery temperature, the BBUs were unable to charge.

A second reference equipment shelf20has an output power of 15 kW, a PSU fan speed of 36,000 rpm, and a charge current of 3.0 A that operated in an environment with an ambient air temperature of 40° C. As compared to the first reference equipment shelf10, the reference equipment shelf20has a reduced output power and a better fan. As shown, at the start of testing, the BBUs of this equipment shelf20operated at a temperature of 48° C. During the discharge period, the BBUs of equipment shelf20did not meet the OTP discharge limit, but were unable to reach or fall below the OTP recovery temperature. Because the BBUs of the second tested equipment shelf20did not return to the OTP recovery temperature, the BBUs were unable to charge.

A third reference equipment shelf30has an output power of 15 kW, a PSU fan speed of 36,000 rpm, and a charge current of 2.0 A that operated in an environment with an ambient air temperature of 35° C. As compared to the first reference equipment shelf10, the reference equipment shelf30has a reduced power output power and a better fan. The reference equipment shelf30also operates at a lower ambient air temperature and is subject to a longer charge. As shown, at the start of testing, the BBUs of this equipment shelf30operated at a steady state temperature of 43° C. During the discharge period, the temperature of the BBUs of equipment shelf30increased but did not meet the OTP discharge limit. The temperature of the BBUs continued to drop during the OTP recovery period and met the OTP recovery temperature. During charging of the BBUs at 2.0 A, the temperature of the BBUs of equipment shelf30again increased and subsequently returned to steady state after the BBUs were fully charged.

As can be appreciated fromFIG. 10, relaxing the shelf output power, reducing the BBU charge rate, and/or improving the PSU fan performance may be insufficient to allow the BBU to be safely charged after a full power discharge, without also lowering the ambient temperature, as the BBU was unable to cool sufficiently to reach the OTP recovery temperature. To achieve charging, the ambient temperature may also need to be reduced.

FIG. 11graphically illustrates the temperature of a battery backup unit (e.g., BBU106) in equipment shelf100during several different modes of operation. The equipment shelf100used inFIG. 11includes an airflow region114with a height of 7 mm, fans118, and PSUs104, but does not include baffles128,130or PSUs204. The equipment shelf100used inFIG. 11operated in an environment with an ambient air temperature of 40° C. with an output power of 15 kW, a charge current of 3.0 A, and a PSU fan speed of 36,000 rpm. As shown, the equipment shelf100is able to discharge and fully charge without exceeding OTP limits. In this way, as compared to reference equipment shelf20for example, implementing the features of equipment shelf100such as an airflow region114, etc. results in a performance improvement that is equivalent to reducing the ambient air temperature by at least 5° C.

Example embodiments described herein may enhance and improve thermal performance of equipment housed in the equipment shelf. For example, the equipment shelf may allow for thermal isolation of temperature-sensitive equipment (e.g., battery back-up units (BBUs)) from heat-generating equipment (e.g., power supply units (PSUs)) using moving air between the equipment housed within the same shelf through an airflow region. The airflow region allows relatively cool ambient air to flow over the BBUs which keeps their temperature lower (e.g., at or near ambient temperatures). This lower temperature creates a “thermal bonus” which may be utilized or “spent” to enhance performance of the equipment shelf in one or more ways including higher power output, longer life, higher efficiency, increased reliability, improved acoustics through lower fan speeds, etc. These embodiments further minimize the risk of BBUs reaching over-temperature protection (OTP) due to heat generated inside the power shelf by the PSUs during normal operating conditions as the BBUs are thermally isolated from the PSUs. In this way, by keeping the BBUs at lower temperatures, BBU functionality and performance is improved, resulting in higher discharge rates, higher efficiency, longer battery life, quicker recharge of BBUs in a shelf with PSUs, etc.