GB2478811A

GB2478811A - Power and cooling system for a data centre

Info

Publication number: GB2478811A
Application number: GB1021102A
Authority: GB
Inventors: Edward Zakrzewski
Original assignee: 2OC Ltd
Current assignee: 2OC Ltd
Priority date: 2009-12-23
Filing date: 2010-12-13
Publication date: 2011-09-21
Anticipated expiration: 2030-12-13
Also published as: GB201021102D0; GB2478811B; GB2476475B; GB2476475A; GB0922444D0; US20110146315A1

Abstract

A data centre 40 has a primary power source comprising a fuel gas pressure reduction station 42 driving a generator 54, and a secondary, backup power source that comprises a large scale electricity distribution network such as the national grid. The fuel gas is a gas combustible with air. Heat exchangers 65 within the data centre can provide heat to heat exchangers 52, downstream of expansion engine comprising turbine 50, in the gas pressure reduction centre which in turn can cool the data centre. Further backup power may be provided by a diesel internal combustion engine (fig 3, 92) driving a generator (fig 3, 90) and a compressor. Carbon dioxide from the exhaust of the engine can be captured, cooled and used as a heat exchange medium to cool servers 4 and act as a fire suppressant in the data centre. Heat from the engine can be fed by heat exchangers (fig 3, 94, 96, 98) to provide heat to the pressure reduction station, to an absorption chiller (fig 3, 98) and to a Rankin engine and generator (fig 3, 102 and 104).

Description

DATA CENTREg AND POWER AND COOLING SYSTEM THEREFOR

FIELD OF THE INVENTION

The present invention relates to a data centre.

BACKGROUND OF THE INVENTION

Data centres are buildings where organisations choose to cluster their computers. The computers are held in a secure environment. In this context this means that environmental controls are applied such that the computers are adequately cooled, access to the computers is restricted, fire protection systems are provided, and continuity of electrical power is also ensured. Issues surrounding the provision of backup generation and cooling will be discussed further with reference to Figure 1.

Figure 1 schematically shows a prior art data centre configuration. The data centre is generally labelled 2 and comprises a plurality of servers 4 which may be owned by a single organisation or which may be owned by multiple organisations where, for example, the data centre owner rents out rack space. The servers require electrical power and this is normally provided by a national electrical infrastructure, i.e. one or more physically remote power stations 10 are connected to the data centre 2 via a generally nationwide distribution network 12, which for example in the UK is referred to as "the national grid". Power generation via the national grid is generally reliable but is not warranted to be available 24/7. Furthermore because the national grid is national and is shared by all other users within the country then it can be liable to disruption on a local basis due to circumstances outside the grid operator's control. Examples of such disruption might include the accidental severing of power cables by builders doing ground works on nearby construction sites.

In order to reduce the risk of disruption data centre owners install uninterruptible power supplies 20 which often include banks of batteries to provide short term power and standby generators running continuously or available at short notice so as to minimise start-up time.

Even if the generator is not running it may be kept warm so as to facilitate a rapid start.

Thus, such UPS systems 20 consume fuel, even under "no load" conditions. They do, however, ensure that the servers 4 can remain powered even if the national grid or a local part of it fails thereby preventing mains power being distributed from the power station 10 to the data centre 2.

The servers in the data centre are often quite densely packed, and deliberately so as high speed computing requires dissimilar computers to be located physically close to one another. As a consequence the servers generate significant amounts of heat which needs to be removed from the data centre by a computer room air-conditioning plant 30 which in reality is a refrigeration unit using chillers, compressors, heat pumps and the like as is well known to the person skilled in the art, to provide a chilled environment around the servers and to pump heat therefrom into the environment. This functionality needs to be maintained even when, for example, on a hot summers day the environmental temperature is greater than the target temperature inside the room containing the servers.

There is, of course, little point in maintaining power to the servers in the event of a failure of the main power supply 12 if cooling is not provided to the server room otherwise the servers would quickly initiate self controlled thermal shutdown in order to protect their components. Consequently the computer room air-conditioning unit 30 also has to be protected by the uninterruptible power supply 20.

GB 1518949 discloses an arrangement in which compressed air from an existing distribution network is provided to a turbine which drives an alternator. The compressed air cools as it expands in the turbine. The alternator provides power to a computer data centre and the cool air is supplied to the data centre for air conditioning. A back up motor servers as an auxiliary source of compressed gas in the event of failure of the compressed air distribution network.

The existing compressed air distribution network that is assumed to exist almost certainly uses electric compressors to compress the gas, so taking account of the cost to run those compressors together with the fact that the gas existing the compressor will be hot and must be allowed to cool, it follows that overall this increases the cost of data centre ownership. Furthermore if the compressors are powered from the national grid then the back up motor will be unpowered when it is needed.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a data centre having a primary power source and a backup power source, wherein the primary power source comprises a gas pressure reduction station driving a generator, and the secondary power source comprises a large scale electricity distribution network.

As used herein "fuel gas" refers to a gas which can be combusted with air. An example is "natural gas" The inventors realised that the data centre power model could be "stood on its head" and the national grid used as the uninterruptible power supply with local power generation forming the primary source of power for the data centre.

According to a second aspect of the present invention there is provided a data centre in combination with a gas pressure reduction station, wherein cooling for the data centre is provided at least in part by the gas pressure reduction station.

The inventors further realised that, looking at the power budget for a data centre as a whole, around half of the electricity consumed by the data centre is used by auxiliary equipment, namely the computer room air-conditioning system, chillers, and the UPS system. Thus the overall power requirement of a data centre could be significantly reduced by placing it in proximity or conjunction with a gas pressure letdown station as the gas pressure letdown station causes gas to become chilled during the expansion process and significant amounts of heat are required by the letdown station in order to prevent undue cooling of pipes in the vicinity of the letdown station, possibly leading to damage of the pipes by ground heave, or the formation of deposits within the pipe as a result of impurities or moisture within the gas condensing out. Similarly the data centre requires large amounts of cooling therefore the data centre can provide the heat that is required by the gas letdown pressure reduction station and is so doing the pressure reduction station provides the cooling required by the data centre.

Advantageously the expansion of gas at the letdown station is performed by allowing the gas to expand in a turbo-expander such that the gas does mechanical work, and this mechanical work, such as rotation of a turbine, can be used to drive a generator thereby providing a source of electricity. The electricity can be provided to run electrical equipment within the data centre.

In data centres the computers are often density packed. It becomes important to deliver cooling to the computers. However a risk of fire also exists. The inventors have realised that the problems can be addressed by using carbon dioxide as a coolant in a cooling system where the carbon dioxide is discharged around and/or into the servers.

BRIEF DESCRIPTION OF THE DRAW1ThIGS

The present invention will further be described, by of non-limiting example only, with reference to the accompanying Figures, in which: Figure 1 schematically represents power and cooling systems for a prior art data centre; Figure 2 schematically represents the power and cooling systems for a data centre constituting an embodiment of the present invention; and Figure 3 schematically shows a further embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Figure 2 schematically shows a combination of a data centre 40 in association with one or more gas pressure letdown stations 42. In broad terms the gas pressure letdown station 42 is connected to a gas distribution network, generally designated 44. Gas pressure within the transmission system 44 can be quite high. For example in the UK it is typically in the region of 72 bar. However gas at this pressure is unsuitable for distribution to consumers and hence the pressure has to be reduced before delivery to pipes 46 that form the final link to consumers. Thus one or more gas pressure letdown stations 42, 42' are provided such that the gas pressure in pipe 46 can ultimately be reduced to around 1 bar.

Reducing the gas pressure causes it to change its volume, and since the expansion process is essentially adiabatic the energy used to change the gas volume is extracted from the internal (thermal) energy of the gas and hence the gas temperature reduces. However since gas, such as natural gas used for fuel, is a complex mix of chemicals this may result in formation of ice or complex hydrates in and around the gas carrying pipes which can damage control valves of the gas distribution system or cause freezing of the ground around the pipe which again may cause damage.

As a consequence a typical gas pressure reduction station comprises an expansion unit 50 such as a turbo expander which is followed by a heat exchanger 52 such that heat can be delivered to the gas exiting the turbo expander 50 so as to warm it sufficiently in order to prevent the problems caused by excessively cold gas. The gas around the heat exchanger is quite cold, so the heat exchanger 52 can be regarded as a source of cold, or a source of cooling power.

The turbo expander 50 performs mechanical work and advantageously is connected to a generator 54 for generating, for example, three phase electricity which can be used to power electrical machines.

It can thus be seen that the gas expansion station 42 generates electricity by virtue of its generator 54 but also requires heat to be supplied to it. Conversely the data centre 40 requires electricity and is also a source of heat which has hitherto required the use of air-conditioning and refrigeration equipment which itself consumes electricity whilst extracting heat from the server environment and pumping it into the atmosphere.

The inventors noted that by combining a gas expansion station with or associating it with a data centre then some or all of the power requirements of the servers could be met by the electricity generated from the generator 54. Similarly the servers present a source of heat.

The servers exchange their heat with the atmosphere surrounding them in the data centre and this can then be circulated by one or more fans 60 past one or more heat exchangers 62 of a cooling unit 65, of which only one is shown, which are in thermal connection with the heat exchanger 52. A transfer medium, such as a liquid or a gas, needs to be circulated inside the heat exchanger network and is driven around the heat exchanger network by a pump (not shown). Simplistically it has been assumed that the heat generation from the servers is sufficient to match the heat requirements at the gas expander. However, as we shall show later additional heating for the heat exchanger 52 can be provided from an internal combustion engine which may also be used as a source of primary electrical power in order to augment or top up the power provided by the generator 54. Similarly, it may be possible that due to load imbalances the heat generated by the servers, and possibly the result of other environmental factors effecting the data centre, might be in excess of the heat load required by the heat exchanger 52. Under such circumstances an otherwise conventional computer room air conditioning plant 70 can be brought into operation, with its power being provided either by the national grid as shown in Figure 2 or being switchable to receive power either from the generator 54 or as will be discussed later from the internal combustion engine.

As shown in Figure 2 one or more letdown stations may be provided in series. If this is the case the second or indeed further letdown stations may also be connected to the data centre providing additional cooling and/or electricity. Where multiple letdown stations are provided, either in series or parallel, then it is highly unlikely that all the letdown stations will either be switched off or develop a fault at the same time and under such circumstances the backup computer room cooling equipment 70 may be of reduced size compared to the conventional plant when used in the configuration shown in Figure 1.

The arrangement shown in Figure 2 not only reduces the general power required by the data centre on a per computer basis because the cooling requirements are much reduced by removing the need to run fully electrically powered computer room air-conditioning equipment, but it also has a surprising effect on the need to provide an uninterruptible power supply.

When considering the prior art case, the uninterruptible power supply is generally running on standby mode all of the time and has to provide sufficient power to run both the servers and the air-conditioning system 30. When the data centre is associated with a gas let down unit then the gas pressure reduction station is running continuously, except in the event of mechanical failure, and this allows for the national grid 12 to take the role of the uninterruptible power supply as there is a high probability that, at the time of a mechanical failure occurring in a turbo expander or generator of a letdown station, that the national grid will be running. Furthermore, where multiple letdown stations are provide in parallel then the chances of a fault effecting all of them becomes significantly reduced.

Figure 3 shows a modified arrangement where two sets of turbo-expanders, designated 50a and SOb respectively are coupled to respective generators 54a and 54b, and each turbo-expander is followed, in gas flow terms, by an associated heat exchanger 52a and 52b. A further heat exchanger 55 is provided upstream of the first turbo-expander 50a so as to warm the high pressure (HP) gas prior to it arriving at the first turbo-expander.

A heat exchange medium, such as a gas, is circulated between the heat exchangers 55, 52a, 52b and the computer room air conditioning equipment 65 of the data centre 40. The flow of the heat exchange medium from any of the heat exchangers 55, 52a and 52b is controlled by a valve system 58 which may incorporate electrically operated valves under the control of a computerised control system (not shown).

In the further arrangement, and as shown in Figure 3, not only may an auxiliary heat and power unit be provided in the form of an internal combustion engine 92 and generator set 90, but a thermal store 80 may also be provided for example in the form of a large volume of water, such that short term outages of the cooling provided by the gas pressure letdown station may be accommodated by dumping heat into the previously cooled thermal store.

This may obviate the need to provided backup cooling 70 in its entirety, or may allow the backup cooling plant to be of reduced size if, for example, the data centre owners work on the assumption that they need only to provide adequate power and cooling for a given number of hours and at the end of that period either the data centre can be de-powered, some of the services can be switched off, or additional power generation and cooling facilities will have been brought online even if that means physically transporting the generators and coolers to the data centre via lorry.

The ability to remove the standby UPS diesel set and battery set should not be underestimated. Even when the UPS is running on standby it is consuming power, and generating heat that may itself need to be removed.

As mentioned before, it may be necessary or desirable to augment the output of the generator 54 by a further generator 90 which is driven by an internal combustion engine 92. Heat from the internal combustion engine may be released to the environment via a conventional water based cooling system for such an engine or may be ducted towards any of the heat exchangers 94, 96 and 98 which may be provided in parallel, or series with controllable by-pass valves. Heat exchanger 94 allows heat from the engine to be added to the heat exchange fluid returning from the data centre computer room air conditioning unit 65, and from here it can be directed to any of the heat exchangers 55, 52a or 52b to warm the gas, with respective warming powers to the heat exchangers being controlled by the valves of the valve system 58.

Heat exchanger 96 allows heat to be delivered to an absorption chiller 98 (such devices being known to the person skilled in the art) which can further cool the heat exchange fluid via a heat exchanger 100.

Heat exchanger 98 allows heat to be delivered to a heat engine, such as an organic Rankin cycle engine 102 (known to the person skilled in the art) which drives a further generator 104.

Generators 54a, 54b, 90 and 104 can all deliver electrical power to the data centre 40, and excess power may be returned to the national grid. Frequency converters may be associated with each generator, but are also known to the person skilled in the art.

As part of its operation the internal combustion engine generates carbon dioxide. The carbon dioxide in the exhaust might be separated from the other exhaust components at a separation unit 110 and may then be purified and compressed by compressor 112 and stored in a tank 114. Suitable known carbon dioxide separation technologies include membrane technologies and pressure swing adsorption techniques. The carbon dioxide may, for example, be used as the heat exchange medium in the heat exchangers 52a, 52b and 65 as its escape into the environment would cause little harm (given that the carbon dioxide would otherwise have been released by operation of the internal combustion engine) and if escape of the carbon dioxide occurs within the server room, then as the server room is generally unmanned, it only serves to further reduce the risk of fire within the server environment. In a further modification the carbon dioxide may be processed to place it into a supercritical state, which can then be used in the computer room air conditioning unit 65.

The carbon dioxide from the internal combustion engine can be compressed by a compressor driven either electrically or from the internal combustion engine to raise its pressure to about 73 atmospheres at about 60°C, where the carbon dioxide becomes supercritical, and behaves like a low viscosity liquid. The supercritical carbon dioxide can be cooled by a heat exchanger and conveyed along pipes to provide heat exchange at the servers. The pipes may have apertures in them such that the carbon dioxide can be conveyed into the server by a pipe and then vented over the electrical components so as to cool them. The carbon dioxide can be recovered, either with or without the use of a carbon dioxide separator depending on concentration within the server cabinets, and reused.

Waste carbon dioxide from the engine might, for example, be ducted towards greenhouses where it is already known to grow plants in an enriched C02 environment as this enhances their rate of growth.

Claims

CLAIMS1. A data centre having a primary power source and a backup power source, wherein the primary power source comprises a fuel gas pressure reduction station driving at least one generator, and the secondary power source comprises a large scale electricity distribution network.
2. A data centre as claimed in claim 1, wherein the gas pressure reduction station is coupled to heat exchangers within the data centre, such that heat produced by computers or other electronic devices within the data centre can be used by the gas pressure reduction station.
3. A data centre as claimed in claim 1 or 2, wherein the gas pressure reduction station is connected to a cooling system of the data centre such that cold from the gas pressure reduction station is used to cool the data centre.
4. A data centre as claimed in any one of the preceding claims further including an internal combustion engine adapted to drive at least one of a generator and a compressor, and wherein carbon dioxide in the exhaust gas of the internal combustion engine is captured and cooled, and used as a heat exchange medium to cool the servers or as a fire suppressant in a server space.
5. A data centre as claimed in claim 4, further including an absorption chiller in combination with the internal combustion engine.
6. A data centre as claimed in claim 4 or 5, in which the internal combustion engine is diesel or bio-fuel powered.
7. A data centre as claimed in any of the preceding claims, in which a heat exchanger is provided downstream of an expansion engine in the gas pressure reduction station.
8. A data centre as claimed in any of claims 3, 4 or 5, where carbon dioxide from the internal combustion engine is used as a cooling medium within the data centre.
9. A data centre as claimed in claim 8, in which the carbon dioxide is converted to supercritical carbon dioxide.
10. A data centre as claimed in claim 8 or 9, in which the carbon dioxide is conveyed into server cabinets or adjacent to electrical components and allowed to flow around electrical components to cool them.