US20100146996A1

US20100146996A1 - Data center cooling energy recovery system

Info

Publication number: US20100146996A1
Application number: US12/332,708
Authority: US
Inventors: Levi A. Campbell; Richard C. Chu; Michael J. Ellsworth, Jr.; Madhusudan K. Iyengar; Robert E. Simons
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 2008-12-11
Filing date: 2008-12-11
Publication date: 2010-06-17

Abstract

A method and associated system is provided for cooling of a data center. The method includes providing coolant to multiple cooling elements in the data center using a heat pump refrigeration cycle to cool the coolant and provide a high temperature at the condenser. This allows the reclaiming of at least a portion of the heat removed from the refrigeration cycle using a heat engine. The engine is disposed between the refrigeration condenser and the ambient environment or cooling medium.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to cooling of computing systems environments and more particularly to cooling of data centers housing a variety of heat generating components such as large computing systems and servers.
2. Description of Background
Businesses today have grown increasingly dependent on the processing power of computer systems. Traditionally, as the size and complex nature of a business grows, its computing needs are greatly increased. Many large businesses require a number of sophisticated computers such as servers to provide for their computing needs. These computing needs require fast and continuous operation of all systems that at times have to be in communication with one another.
It is often more convenient to house a variety of computer systems in a common facility known as a data center. Data centers also house associated computing components such as such as telecommunication and storage systems. Redundant and backup units such as power supplies, data communication connections and environmental and security devices are also housed in the same location. Because of cost concerns, however, data centers are designed to house a maximum number of units, including the computer systems and their associated components, in a tight foot print. Locating a large number of heat generating systems and components in one location and in close proximity to one another requires the designer of these facilities to address heat dissipation issues.
At the same time, the computer industry trend has been to continuously increase the number of electronic components inside each computer or systems to provide maximum processing power. The ever growing number of heat generating components inside the computer units further exacerbate the heat dissipation issues. These issues if not dealt with adequately can harm the structural and data integrity of the computer system and even the data center as a whole.
Cooling of data centers has become a significant cost of operation for businesses. Typically, the liquid coolant used to cool the data center is supplied by a chiller plant which rejects the heat to an ambient environment or medium, be it a river, groundwater, outside air, or via evaporative cooling tower. In this process, hundreds of kilowatts or even several megawatts of power are utilized by the computers and cooling equipment which is subsequently rejected to the ambient medium or environment. Unfortunately, with rising energy costs, the cost of maintaining data centers have become prohibitive. Consequently, it is highly desirable to reduce the energy consumption of the cooling equipment or reclaim some of that power to reduce data center operating cost and limit its impact to the environment.

SUMMARY OF THE INVENTION

The shortcomings of the prior art are overcome and additional advantages are provided through the provision of a method and associated system cooling a computer data center. The system comprises a heat exchanging assembly disposed in thermal communication with the data center. The heat exchanging assembly has a heat exchanger and a condenser in thermal communication with each other via a chiller. The heat exchanger also has a heat engine in thermal communication with said chiller and the condenser. The system also includes a pump enabled for supplying and returning coolants to the data center and the heat exchanging assembly. The heat exchanger assembly being in thermal communication with the ambient cooling medium for containing thermal needs of the data center. The heat engine extracts mechanical work from the heat transfer process between the condenser and the ambient environment. In one embodiment, the mechanical work extracted from the engine can then be used to at least partially drive the chiller. In an alternate embodiment, the system for cooling the computer data center comprises a chiller and a condenser in thermal communication with one another and enabled to receive a coolant to cool the data center. The chiller is in thermal contact with the data center and a condenser. The condenser, in turn, is in thermal contact with a heat engine that ultimately connects to an ambient environment or medium. The coolant supplied circulates via the chiller cooling both the heat exchanger and the data center directly. Mechanical work can then be extracted from the engine to drive the chiller at least partially. Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features, refer to the description and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other objects, features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view illustration of a computer housing having a rack frame;

FIG. 2 is a schematic representation of a data center such as used in the embodiments of the present invention;

FIG. 3 is a schematic illustration of one embodiment of the present invention;

FIGS. 4 and 5 are graphical depiction of performance curves as pertaining to different case scenarios obtained by analyzing a system as provided by the embodiment of FIG. 3;

FIG. 6 is a schematic illustration of an alternate embodiment of the present invention.

DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view illustration of a computer environment comprising of a housing 100, having a frame 102, preferably with a rack or cage like structure as shown. The housing 100 can also incorporate full or partial doors or covers such as referenced by numerals 101.
It should be noted that as used herein, the term computer or electronic rack 102, hereinafter will be used for ease of reference but can be construed to include any housing, frame, rack, compartment, blade server system or other structural arrangements including any that may incorporate doors and/or covers. In addition, the computer rack 102 can be either a stand alone computer processor or a sophisticated system, having high, mid or low end processing capability. The electronic rack 102 may also comprise a stack of electronic system chassis or multi-blade center systems 110, as well as supporting power supplies, networking equipment and other similar and necessary components, not individually illustrated.
In a typical data center, a plurality of such computer racks 102 are disposed next to one another in as tight of a fit as allowable by the rack design and needs of the electronic components inside each system. FIG. 2 is a schematic representation of a data center referenced by numerals 200. FIG. 2 is provided as a base case against which the methodology of different embodiments of the present invention will be compared to. In FIG. 2, a base design providing only the simplest and most rudimentary data center components as will be used in conjunction with the embodiments of the present invention is provided.
Referring back to FIG. 2, the data center 200 houses a plurality of heat generating components and computing systems, generally referenced by numerals 102. In this particular case, coolant used is water such as facility chilled water. The coolant (not shown specifically) is used to address the cooling needs of the data center 200. As shown, this coolant (water) flows in the direction of arrow 205 through heat exchange elements in the data center 200 to cool air or the electronics directly. In one embodiment, the water is cooled by a facility heat exchanging assembly 220, preferably liquid to liquid heat exchangers coupled to the evaporator and condenser sides of a vapor compression refrigeration chiller. The coolant is returned from the data center 200 and is generally circulated and moved via pump 290.
The heat exchanging components as shown can incorporate a chiller 222, such as one that uses vapor compression refrigeration or even one with absorption refrigeration. The chiller 222 functions such that it provides fluid to a cold side heat exchanger 224. The heat is then rejected to the ambient environment after passing through a condenser 226 (hot side heat exchanger). This heat rejection can be accomplished in a variety of ways as known to those skilled in the art. For example the heat can be rejected via a cooling tower, or exchanged to a water source such as a river or groundwater facilities, shown generally by arrows referenced by numerals 260.
FIG. 3 is an illustration of one embodiment of the present invention. In this embodiment, a coolant is provided to multiple cooling elements in thermal communication with the data center 202. As before, the data center houses a plurality of computing systems and other heat generating components 102. Certain elements have been added that will greatly decrease the energy required to cool the data center 202. As in FIG. 2 a heat pump refrigeration cycle is used to cool the coolant and provide a high temperature at the condenser 226 (or the hot side heat exchanger). In this embodiment, however, the heat exchanging assembly 320 of this embodiment has different components than those discussed in relation to FIG. 2 (referenced as 220). In this embodiment, the work generated in the heat engine 350 is used to at least partially drive the chiller 222, or preferably a liquid to liquid heat pump refrigeration assembly or system.
In FIG. 3, the heat from components housed in the data center 202 dissipates and is then removed by heat exchangers (224 and 226) within the data center facility via chiller 222. The coolant (not illustrated specifically) is supplied and circulated via a pump 390 throughout as shown. The coolant flow into and out of the pump is illustrated by arrows referenced as 305. The heat is then removed from the coolant by a chiller 222, preferably a vapor compression refrigeration chiller. The hot side of the chiller is preferentially at a high temperature with respect to the ultimate ambient environment (sink). This is in contrast to typical design goals and is designed specifically in order to maximize the efficiency of a heat engine 350, as will be discussed. The heat engine 350 then extracts mechanical work from the heat transfer process between the hot side heat exchanger or condenser 226 and the ambient environment 260. The extracted mechanical work is then used to at least partially drive the chiller 222, and in some cases even the pump. In this way, a portion of the heat transported by the refrigeration cycle is reclaimed using the heat engine referenced as 350.
A variety of heat engines can be utilized as known to those skilled in the art. It is desired to use a heat engine having an efficiency approaching the theoretical maximum or “Carnot efficiency”. Some examples are Stirling engines or Ericsson cycle engines. In the embodiment shown, the heat engine 350 is disposed between the refrigeration condenser and the ambient environment or cooling medium, which is referenced as 260 (i.e. cooling tower, outdoor air, water source such as groundwater, river or lake).
In alternate embodiments design parameters can be selectively changed to provide optimal results, as per needs of the individual data center.
In the embodiment of FIG. 3 one pump as referenced by numerals 390 is used to recirculate coolant supplied to data center and returned from it to the assembly 320. In other embodiments, more than one pump can be used. In some embodiments as will be discussed below, it can be possible to completely remove the pump or replace it with other components as known to those skilled in the art.
The embodiment of FIG. 2 was analyzed. In the embodiment provided in FIG. 2, a situation was examined where the data center comprised of 250 kW total load. This was for 20 systems each producing a heat load of 12.5 kW. The 250 kW of power was transferred into the air to liquid heat exchangers mounted in the exhaust path of warm air exiting each rack. The coolant supplied to each heat exchanger was water at a flow rate of 8 gpm and a temperature of 18 degrees Celsius. The pump consumption was about 1.4 kW (8 gpm at 20 psid for each of the 20 system units). The chiller had a COP (defined as COP=Q_load/W_compressor) of 6. This required about 42.6 kW of power to drive the chiller The cost of electricity was assumed to be $0.10/kWh, resulting in a cooling cost of $36.4 k/yr.
The same data center facility was also used with the same number of computing system units to obtain calculated results for the embodiment of FIG. 3. A similar pump and a similar chiller were used as before (at 1.4 KW and a COP of 6). Two cases were analyzed as will be discussed below.
In the first case (hereinafter Case I), a Stirling engine assumed to have the theoretical Carnot efficiency for work output was used (η=1−T_C/T_H). In the first case the temperature of the data center coolant was 18 degrees Celsius and T_Cwas outdoor air at 30 degrees Celsius.
In the second case, (hereinafter Case II) T_Cas ground water at 13 degrees Celsius and the data center coolant water temperature was at 22 degrees Celsius. In both cases, the pumps and chillers used were identical to those discussed above.
FIGS. 4 and 5 are graphical depictions of performance curves as pertaining to the two different cases discussed above in relation to the embodiment of FIG. 3. Both curves show the correlation between the energy cost savings versus the chiller condensation temperature.
FIG. 4 shows an example of a performance curve for the first case (Case I) scenario. In this case, the coolant supplied to the heat exchangers in the data center is at a lower temperature than the ambient environment (ultimate “ambient” sink). The heat engine can only provide a portion of the mechanical power required to drive the chiller and pump (at typical vapor compression chiller coefficient of performance of 6). The idealized Carnot heat engine (modern Stirling engines have an efficiency approaching the theoretical maximum or “Carnot efficiency”) can supply up to 72% of the power necessary to run the chiller and coolant pump. Similarly FIG. 5 shows an example performance curve for Case II, as discussed. In this case the coolant supplied to the heat exchangers in the data center is at a higher temperature than the ambient environment (ultimate sink). All of the mechanical power required to drive the chiller and coolant pump can then be supplied by the heat engine.
Comparing the highlighted data in FIGS. 4 and 5 to data as discussed for the cases analyzed it is evident that both cases as provided by the embodiment of FIG. 3 result in substantial energy savings as opposed to that provided in conjunction with the embodiment as discussed in conjunction with FIG. 2. As shown, in Case I (FIG. 4) for example the savings results in a 72% reduction in cooling (electricity) costs. This can translate into a 11.6 kW power requirement (using embodiment of FIG. 3) as opposed to a 41.6 kW power requirement (using embodiment of FIG. 2), resulting in an annual savings of $26,000. In Case II (FIG. 5) the savings are even greater. In Case II, the system results in a 100% reduction in cooling (electricity) needs. This is the entire cooling energy requirement for the system which is now recovered by the heat engine. The ultimate savings in this example will translate into an annual savings of $36.4 k/yr.
FIG. 6 is an illustration of an alternate embodiment of the present invention. In this embodiment, the refrigerant or coolant in the chiller 222 is used to cool the data center, referenced here as 202. As before, the chiller can be a liquid to liquid heat pump refrigeration assembly with heat engine types used as discussed in previous embodiments. The heat engine can again recuperate a portion of the power required to at least partially drive the chiller, extracting work from the heat transfer process between the condenser side heat exchanger 526 and the ambient 260.
While the preferred embodiment of the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.

Claims

1. A system for cooling a computer data center comprising: a heat exchanging assembly disposed in thermal communication with data center; said heat exchanging assembly having a cold side (evaporator) heat exchanger and a hot side (condenser) heat exchanger in thermal communication with each other via a chiller; said heat exchanging assembly also having a heat engine in thermal communication with said condenser; at least one pump enabled for supplying and returning coolants to said data center and said heat exchanging assembly; said heat exchanger assembly being in thermal communication with ambient environment for containing thermal needs of said data center; said heat engine extracting mechanical work from heat transfer process between said condenser and said ambient environment.

2. The system of claim 1, wherein said extracted mechanical work can be used to at least partially power said chiller.

3. The system of claim 2, wherein said extracted mechanical work can be used to at least partially power said at least one pump.

4. The system of claim 3, wherein said chiller is a liquid to liquid heat pump refrigeration assembly.

5. The system of claim 2, wherein said engine is a Stirling cycle heat engine.

6. The system of claim 2, wherein said engine is an Ericsson engine.

7. The system of claim 2, wherein said pump is connected to said cold side heat exchanger.

8. The system of claim 2, wherein a plurality of pumps are used.

9. A system for cooling a computer data center comprising: a chiller and a condenser in thermal communication with one another and enabled to receive a coolant to cool said data center; said chiller being in thermal contact with said data center and said condenser; said condenser also being in thermal contact with a heat engine connected ultimately to an ambient environment such that when coolant is supplied it circulates in said chiller, cooling said data center directly such that said heat engine extracts mechanical work from heat transfer process between said condenser and said ambient environment.

10. The system of claim 8, wherein said extracted mechanical work can be used to at least partially power said chiller.

11. The system of claim 9, wherein said heat engine is a Stirling cycle heat engine.

12. The system of claim 9 wherein said heat engine is an Ericsson cycle heat engine.

13. A method for cooling a data center comprising the steps;

disposing a heat a heat exchanging assembly disposed in thermal communication with data center; said heat exchanging assembly having a heat exchanger and a condenser in thermal communication with each other via a chiller;

said heat exchanger also having a heat engine in thermal communication with said condenser;

using a heat pump refrigeration cycle to cool coolants used in said heat exchanger assembly such that it provides a high temperature at said condenser and reclaiming a portion of heat removed from any refrigeration cycle using said heat engine between the refrigeration condenser and an ambient cooling medium also in thermal communication with said assembly;

and extracting mechanical work via said heat engine from heat transfer process between said condenser and said ambient environment.

14. The method of claim 13, wherein said extracted mechanical work can be used to at least partially power said chiller.

15. The method of claim 13, wherein said chiller is a liquid to liquid heat pump refrigeration assembly.

16. The method of claim 13 wherein said engine is a Stirling cycle heat engine.

17. The method of claim 13 wherein said engine is an Ericsson cycle heat engine.

18. The method of claim 13, wherein at least one pump is connected to said heat exchanger and circulates coolant through the data center.

19. The method of claim 13, wherein a cooling tower is used to reject said heat to ambient environment.

20. The method of claim 13, wherein said coolant is water.