2012年，微軟宣布計劃汰換安裝在俄勒岡州昆西(Quincey)大數(shù)據(jù)中心(big data center)園區(qū)的柴油發(fā)電機。六年后，同樣的組織懷著同樣的愿望，結(jié)果申請安裝了72臺柴油發(fā)電機，而這也代表在短期內(nèi)還是需要仰賴發(fā)電機作為其關鍵設施的一部分。這個例子清楚地說明了柴油發(fā)電機對于大中型數(shù)據(jù)中心的運行是多么重要。幾乎沒有人—甚至很少有人—能夠考慮在沒有柴油發(fā)電機的情況下運營數(shù)據(jù)中心生產(chǎn)環(huán)境。

       大部分的經(jīng)營者和業(yè)主都希望淘汰或降低對發(fā)電機的需求，用更現(xiàn)代、更清潔的技術取而代之。由于柴油發(fā)電機的運行會造成一定程度的污染—它們排放二氧化碳和微粒，這意味著可能會受到政府監(jiān)管和運行上的限制;它們的價格也不便宜且在大部分時間里可能都是空閑的;它們在測試、法規(guī)一致性、和燃料管理方面需要考慮到額外的運營開銷(舉例來說: 質(zhì)量、供應、維護、和存儲等等)。

      但迄今為止，還沒有其他技術能如此有效地將低運行成本、能量密度、可靠性、本地控制、以及能在燃料無虞下長期無限制地供應連續(xù)動力給關鍵負載等等因素結(jié)合在一起。

      這種情況會改變嗎?這不會是完全地、立即地或戲劇性地—但是答案會是肯定的。淘汰發(fā)電機的動機對某些機構來看越來越強，特別是在超大型的運營商(大多數(shù)已經(jīng)消除或降低了電網(wǎng)供應中可報告的碳排放(透過清潔能源等)，剩下無法消除的大部分由發(fā)電機承擔)。而燃料電池、鋰離子電池和許多管理軟件等新技術的結(jié)合也開始顯得更加有效。即使發(fā)電機沒有完全被淘汰，我們預計從2020年起會開始有項目將涉及用較少的發(fā)電機和其他替代方案了來覆蓋原有的需求。

四個關注領域

       在技術、研究、和部署方面有四個關注領域，這可能意味著在未來的某些情況下，柴油發(fā)電機的地位和功能性可能將會減弱—或者在未來可能會被取代。

燃料電池和安裝在現(xiàn)場的連續(xù)可再生潔凈能源

       用燃料電池代替發(fā)電機的可能性已經(jīng)被深入探索了十年(應用在較小規(guī)模的程度上，也嘗試了十年)。至少有三家供應商—Bloom Energy(美國)、Doosan(韓國)和SOLIDPower (德國)—各擁有一些數(shù)據(jù)中心設施安裝的案例。其中，又以Bloom在Equinix上的成功最為人所知。燃料電池可以說是繼發(fā)電機之后，目前各方爭論里一種可能可以提供可靠的、現(xiàn)場的、連續(xù)的大規(guī)模電力的技術。

       然而燃料電池在數(shù)據(jù)中心的使用備受爭議。包括加州圣克拉拉市在內(nèi)的一些城市認為，燃料電池和發(fā)電機一樣，不見得干凈和環(huán)保，因為大多數(shù)燃料電池使用的是基于化石燃料的氣體(或氫，通常需要化石燃料的能量來分離)。 

        但燃料電池還有另外兩個缺點:首先，它們每美元的成本高于發(fā)電機，而且只有在獲得補貼的情況下，它們才被證明是經(jīng)濟的;第二，它們需要持續(xù)穩(wěn)定的負載(取決于燃料電池結(jié)構)。這導致了設計和成本的復雜性。

       爭論還將繼續(xù)，但即便如此，燃料電池已經(jīng)開始部署:有用戶計劃在康涅狄格州建立一個數(shù)據(jù)中心園區(qū)(所有者/運營商目前保密)，他們將擁有20兆瓦的燃料電池配置。目前采用燃料電池最主要的原因不是成本或可用性，而是實現(xiàn)大幅減少二氧化碳和其他排放的能力，以及建造沒有閑置設備的架構的能力。

      將現(xiàn)場設置可再生能源作為大規(guī)模能源的主要來源的想法目前只獲得非常少的支持。但Uptime Institute發(fā)現(xiàn)了一個正在發(fā)展的趨勢:將數(shù)據(jù)中心與水電(或是沼氣(理想上來說))等本地能源結(jié)合起來。至少有兩個在歐洲的項目考慮類似的方案。這樣的數(shù)據(jù)中心將兩個位于本地但各自獨立的可再生能源中獲取所需電力，并建立一個具備同時可維護性的可靠系統(tǒng)，以防其中一個發(fā)生故障。使用電池、抽水蓄能和其他技術的本地能源存儲方式并行能夠提供額外的安全保障。

邊緣數(shù)據(jù)中心

      中型和大型數(shù)據(jù)中心有很大的電源需求，在大多數(shù)情況下，需要高可用性。但對于較小的數(shù)據(jù)中心，并非總是有高可用性的要求。其容量可能低于500千瓦(kW)，且預計在未來10年還會有更多這樣規(guī)模的數(shù)據(jù)中心。這樣的數(shù)據(jù)中心可能更容易地將其負載和數(shù)據(jù)復制到附近的類似數(shù)據(jù)中心，可以參與到分布式災備恢復系統(tǒng)，這樣一來如果發(fā)生停機，在任何情況下所引起的問題都更少。

       但最重要的是，這些數(shù)據(jù)中心可以部署電池(或其他小的備用系統(tǒng))，從而在網(wǎng)絡重新部署流量和工作負載的同時，實現(xiàn)足夠的備用時間。例如，一個小型集裝箱大小的500千瓦時鋰離子電池除了可以提供所有的不間斷電源(UPS)功能外，且能將電力反饋給電網(wǎng)，并在電網(wǎng)斷電時為小型數(shù)據(jù)中心(比如250千瓦)提供數(shù)小時的電力。隨著技術的進步和價格的下降，這樣的部署將變得更加正常。此外，當與小型發(fā)電機一起使用時，這些系統(tǒng)可以提供長時間的電力。

基于云計算的彈性

       當微軟、Equinix和其他公司談到減少對發(fā)電機的依賴時，他們主要指的是廣泛使用替代電源。但是對于超大規(guī)模的數(shù)據(jù)中心，甚至更小的數(shù)據(jù)中心集群來說，它們的必殺技則是采用可用性區(qū)域、流量交換、復制、負載管理和管理軟件在數(shù)據(jù)中心失去電力來源時快速重新配置。

     這樣的架構被證明在某種程度上是有效的，但是它們是昂貴的、復雜的，并且并非萬無一失。即使采用完全復制，丟失整個數(shù)據(jù)中心也會導致性能問題。由于這個原因，所有主要的數(shù)據(jù)中心運營商都繼續(xù)在數(shù)據(jù)中心這個級別上構建具有同時可維護性和現(xiàn)場可控電力來源的數(shù)據(jù)中心。

      但隨著軟件的改進和摩爾定律的不斷發(fā)展，這種情況會改變嗎?根據(jù)2019年的目前發(fā)展技術水平和新建項目的計劃，答案可以說是“還沒有”。但在2019年，至少有一家大型運營商利用這些技術進行了測試，以確定其彈性?？赡艿哪繕瞬皇峭耆裼桶l(fā)電機，而是減少部分需要柴油發(fā)電機支撐的工作負載。

鋰離子和智慧能源

       對于數(shù)據(jù)中心的設計者來說，過去幾年最重要的進步之一是鋰離子電池在技術和經(jīng)濟上的成熟。根據(jù)彭博-新能源財經(jīng)(Bloomberg-NEF)的數(shù)據(jù)，從2010年到2018年，鋰離子電池的成本(以每千瓦時美元計算)下降了85%。多數(shù)分析師預計，未來5年價格將繼續(xù)穩(wěn)步下跌，而大規(guī)模制造業(yè)是主要原因。雖然這不是摩爾定律，但它創(chuàng)造了一個機會，以新的方式引入一種新的儲能形式—包括取代一些發(fā)電機。

      雖然現(xiàn)在還處于初期階段，但主要的運營商、制造商和新創(chuàng)公司都在考慮如何利用鋰離子存儲技術，結(jié)合多種形式的能源發(fā)電，以減少對發(fā)電機的依賴?；蛟S不應該將鋰離子電池看作是發(fā)電機的直接替代品，因為在一段時間內(nèi)，它不太可能是經(jīng)濟的，但是鋰離子電池的使用不僅僅是一個標準的UPS應用，而是更有創(chuàng)造性和更積極的。例如，根據(jù)關鍵重要程度結(jié)合負荷轉(zhuǎn)移和關閉應用程序，UPS的備用時間可大大擴展。發(fā)電機則可能將啟動時間向后延遲(但或不是所有) ，有些甚至可能可以做到淘汰發(fā)電機。這一領域的試驗和試點可能會在2020年或不久后啟動或公布。

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In 2012, Microsoft announced that it planned to eliminate engine generators at its big data center campus in Quincey, Oregon. Six years later the same group, with much the same aspirations, filed for permission to install 72 diesel generators, which have an expected life of at least a decade. This example illustrates clearly just how essential engine generators are to the operation of medium and large data centers. Few — very few — can even contemplate operating production environments without diesel generators.

Almost every operator and owner would like to eliminate generators and replace them with a more modern, cleaner technology. Diesel generators are dirty — they emit both carbon dioxide and particulates, which means regulation and operating restrictions; they are expensive to buy; they are idle most of the time; and they have an operational overhead in terms of testing, regulatory conformity and fuel management (i.e., quality, supply and storage logistics).

But to date, no other technology so effectively combines low operating costs, energy density, reliability, local control and, as long as fuel can be delivered, open-ended continuous power.

Is this about to change? Not wholly, immediately or dramatically — but yes, significantly. The motivation to eliminate generators is becoming ever stronger, especially at the largest operators (most have eliminated reportable carbon emissions from their grid supply, leaving generators to account for most of the rest). And the combination of newer technologies, such as fuel cells, lithium-ion (Li-ion) batteries and a lot of management software, is beginning to look much more effective. Even where generators are not eliminated entirely, we expect more projects from 2020 onward will involve less generator cover.

Four Areas of Activity 

There are four areas of activity in terms of technology, research and deployment that could mean that in the future, in some situations, generators will play a reduced role — or no role at all.

Fuel cells and on-site continuous renewables

The opportunity for replacing generators with fuel cells has been intensively explored (and to a lesser extent, tried) for a decade. At least three suppliers — Bloom Energy (US), Doosan (South Korea) and SOLIDPower (Germany) — have some data center installations. Of these, Bloom’s success with Equinix is best known. Fuel cells are arguably the only technology, after generators, that can provide reliable, on-site, continuous power at scale.

The use of fuel cells for data centers is controversial and hotly debated. Some, including the city of Santa Clara in California, maintain that fuel cells, like generators, are not clean and green, because most use fossil fuel-based gas (or hydrogen, which usually requires fossil fuel-based energy to isolate). Others say that using grid-supplied or local storage of gas introduces risks to availability and safety.

These arguments are possibly easily overcome, given the reliability of gas and the fact that very few safety issues ever occur. But fuel cells have two other disadvantages: first, they cost more than generators on a kilowatt-hour (kWh) per dollar($) basis and have mostly proven economic only when supported by grants; and second, they require a continuous, steady load (depending on the fuel cell architecture). This causes design and cost complications.

The debate will continue but even so, fuel cells are being deployed: a planned data center campus in Connecticut (owner/operator currently confidential) will have 20 MW of Doosan fuel cells, Equinix is committing to more installations, and Uptime Institute is hearing of new plans elsewhere. The overriding reason is not cost or availability, but rather the ability to achieve a dramatic reduction in carbon dioxide and other emissions and to build architectures in which the equipment is not sitting idle.

The idea of on-site renewables as a primary source of at-scale energy has gained little traction. But Uptime Institute is seeing one trend gathering pace: the colocation of data centers with local energy sources such as hydropower (or, in theory, biogas). At least two projects are being considered in Europe. Such data centers would draw from two separate but local sources, providing a theoretical level of concurrent maintainability should one fail. Local energy storage using batteries, pumped storage and other technologies would provide additional security.

Edge data centers

Medium and large data centers have large power requirements and, in most cases, need a high level of availability. But this is not always the case with smaller data centers, perhaps below 500 kilowatt (kW), of which there are expected to be many, many more in the decade ahead. Such data centers may more easily duplicate their loads and data to similar data centers nearby, may participate in distributed recovery systems, and may, in any case, cause fewer problems if they suffer an outage.

But above all, these data centers can deploy batteries (or small fuel calls) to achieve a sufficient ride-through time while the network redeploys traffic and workloads. For example, a small shipping container-sized 500 kWh Li-ion battery could provide all uninterruptible power supply (UPS) functions, feed power back to the grid and provide several hours of power to a small data center (say, 250 kW) in the event of a grid outage. As the technology improves and prices drop, such deployments will become commonplace. Furthermore, when used alongside a small generator, these systems could provide power for extended periods.

Cloud-based resiliency

When Microsoft, Equinix and others speak of reducing their reliance on generators, they are mostly referring to the extensive use of alternative power sources. But the holy grail for the hyperscale operators, and even smaller clusters of data centers, is to use availability zones, traffic switching, replication, load management and management software to rapidly re-configure if a data center loses power.

Such architectures are proving effective to a point, but they are expensive, complex and far from fail-safe. Even with full replication, the loss of an entire data center cannot but cause performance problems. For this reason, all the major operators continue to build data centers with concurrent maintainability and on-site power at the data center level.

But as software improves and Moore’s law continues to advance, will this change? Based on the state of the art in 2019 and the plans for new builds, the answer is categorically “not yet.” But in 2019, at least one major operator conducted tests to determine its resiliency using these technologies. The likely goal would not be to eliminate generators altogether, but to reduce the portion of the workload that would need generator cover.

Li-ion and smart energy

For the data center designer, one of the most significance advances of the past several years is the maturing — technically and economically — of the Li-ion battery. From 2010 to 2018, the cost of Li-ion batteries (in $ per kWh) fell 85%, according to Bloomberg-NEF (New Energy Finance). Most analysts expect prices to continue to fall steadily for the next five years, with large-scale manufacturing being the major reason. While this is no Moore’s law, it is creating an opportunity to introduce a new form of energy storage in new ways — including the replacement of some generators.

It is early days, but major operators, manufacturers and startups alike are all looking at how they can use Li-ion storage, combined with multiple forms of energy generation, to reduce their reliance on generators. Perhaps this should not be seen as the direct replacement of generators with Li-ion storage, since this is not likely to be economic for some time, but rather the use of Li-ion storage not just as a standard UPS, but more creatively and more actively. For example, combined with load shifting and closing down applications according to their criticality, UPS ride-throughs can be dramatically extended and generators will be turned on much later (or not all). Some may even be eliminated. Trials and pilots in this area are likely to be initiated or publicized in 2020 or soon after.

(Alternative technologies that could compete with lithium-ion batteries in the data center include sodium-ion batteries based on Prussian blue electrodes.)