2012年，微软宣布计划汰换安装在俄勒冈州昆西(Quincey)大数据中心(big data center)园区的柴油发电机。六年后，同样的组织怀着同样的愿望，结果申请安装了72台柴油发电机，而这也代表在短期内还是需要仰赖发电机作为其关键设施的一部分。这个例子清楚地说明了柴油发电机对于大中型数据中心的运行是多么重要。几乎没有人—甚至很少有人—能够考虑在没有柴油发电机的情况下运营数据中心生产环境。
大部分的经营者和业主都希望淘汰或降低对发电机的需求，用更现代、更清洁的技术取而代之。由于柴油发电机的运行会造成一定程度的污染—它们排放二氧化碳和微粒，这意味着可能会受到政府监管和运行上的限制;它们的价格也不便宜且在大部分时间里可能都是空闲的;它们在测试、法规一致性、和燃料管理方面需要考虑到额外的运营开销(举例来说: 质量、供应、维护、和存储等等)。
但迄今为止，还没有其他技术能如此有效地将低运行成本、能量密度、可靠性、本地控制、以及能在燃料无虞下长期无限制地供应连续动力给关键负载等等因素结合在一起。
这种情况会改变吗?这不会是完全地、立即地或戏剧性地—但是答案会是肯定的。淘汰发电机的动机对某些机构来看越来越强，特别是在超大型的运营商(大多数已经消除或降低了电网供应中可报告的碳排放(透过清洁能源等)，剩下无法消除的大部分由发电机承担)。而燃料电池、锂离子电池和许多管理软件等新技术的结合也开始显得更加有效。即使发电机没有完全被淘汰，我们预计从2020年起会开始有项目将涉及用较少的发电机和其他替代方案了来覆盖原有的需求。
四个关注领域
在技术、研究、和部署方面有四个关注领域，这可能意味着在未来的某些情况下，柴油发电机的地位和功能性可能将会减弱—或者在未来可能会被取代。
燃料电池和安装在现场的连续可再生洁净能源
用燃料电池代替发电机的可能性已经被深入探索了十年(应用在较小规模的程度上，也尝试了十年)。至少有三家供应商—Bloom Energy(美国)、Doosan(韩国)和SOLIDPower (德国)—各拥有一些数据中心设施安装的案例。其中，又以Bloom在Equinix上的成功最为人所知。燃料电池可以说是继发电机之后，目前各方争论里一种可能可以提供可靠的、现场的、连续的大规模电力的技术。
然而燃料电池在数据中心的使用备受争议。包括加州圣克拉拉市在内的一些城市认为，燃料电池和发电机一样，不见得干净和环保，因为大多数燃料电池使用的是基于化石燃料的气体(或氢，通常需要化石燃料的能量来分离)。
但燃料电池还有另外两个缺点:首先，它们每美元的成本高于发电机，而且只有在获得补贴的情况下，它们才被证明是经济的;第二，它们需要持续稳定的负载(取决于燃料电池结构)。这导致了设计和成本的复杂性。
争论还将继续，但即便如此，燃料电池已经开始部署:有用户计划在康涅狄格州建立一个数据中心园区(所有者/运营商目前保密)，他们将拥有20兆瓦的燃料电池配置。目前采用燃料电池最主要的原因不是成本或可用性，而是实现大幅减少二氧化碳和其他排放的能力，以及建造没有闲置设备的架构的能力。
将现场设置可再生能源作为大规模能源的主要来源的想法目前只获得非常少的支持。但Uptime Institute发现了一个正在发展的趋势:将数据中心与水电(或是沼气(理想上来说))等本地能源结合起来。至少有两个在欧洲的项目考虑类似的方案。这样的数据中心将两个位于本地但各自独立的可再生能源中获取所需电力，并建立一个具备同时可维护性的可靠系统，以防其中一个发生故障。使用电池、抽水蓄能和其他技术的本地能源存储方式并行能够提供额外的安全保障。
边缘数据中心
中型和大型数据中心有很大的电源需求，在大多数情况下，需要高可用性。但对于较小的数据中心，并非总是有高可用性的要求。其容量可能低于500千瓦(kW)，且预计在未来10年还会有更多这样规模的数据中心。这样的数据中心可能更容易地将其负载和数据复制到附近的类似数据中心，可以参与到分布式灾备恢复系统，这样一来如果发生停机，在任何情况下所引起的问题都更少。
但最重要的是，这些数据中心可以部署电池(或其他小的备用系统)，从而在网络重新部署流量和工作负载的同时，实现足够的备用时间。例如，一个小型集装箱大小的500千瓦时锂离子电池除了可以提供所有的不间断电源(UPS)功能外，且能将电力反馈给电网，并在电网断电时为小型数据中心(比如250千瓦)提供数小时的电力。随着技术的进步和价格的下降，这样的部署将变得更加正常。此外，当与小型发电机一起使用时，这些系统可以提供长时间的电力。
基于云计算的弹性
当微软、Equinix和其他公司谈到减少对发电机的依赖时，他们主要指的是广泛使用替代电源。但是对于超大规模的数据中心，甚至更小的数据中心集群来说，它们的必杀技则是采用可用性区域、流量交换、复制、负载管理和管理软件在数据中心失去电力来源时快速重新配置。
这样的架构被证明在某种程度上是有效的，但是它们是昂贵的、复杂的，并且并非万无一失。即使采用完全复制，丢失整个数据中心也会导致性能问题。由于这个原因，所有主要的数据中心运营商都继续在数据中心这个级别上构建具有同时可维护性和现场可控电力来源的数据中心。
但随着软件的改进和摩尔定律的不断发展，这种情况会改变吗?根据2019年的目前发展技术水平和新建项目的计划，答案可以说是“还没有”。但在2019年，至少有一家大型运营商利用这些技术进行了测试，以确定其弹性。可能的目标不是完全消除柴油发电机，而是减少部分需要柴油发电机支撑的工作负载。
锂离子和智慧能源
对于数据中心的设计者来说，过去几年最重要的进步之一是锂离子电池在技术和经济上的成熟。根据彭博-新能源财经(Bloomberg-NEF)的数据，从2010年到2018年，锂离子电池的成本(以每千瓦时美元计算)下降了85%。多数分析师预计，未来5年价格将继续稳步下跌，而大规模制造业是主要原因。虽然这不是摩尔定律，但它创造了一个机会，以新的方式引入一种新的储能形式—包括取代一些发电机。
虽然现在还处于初期阶段，但主要的运营商、制造商和新创公司都在考虑如何利用锂离子存储技术，结合多种形式的能源发电，以减少对发电机的依赖。或许不应该将锂离子电池看作是发电机的直接替代品，因为在一段时间内，它不太可能是经济的，但是锂离子电池的使用不仅仅是一个标准的UPS应用，而是更有创造性和更积极的。例如，根据关键重要程度结合负荷转移和关闭应用程序，UPS的备用时间可大大扩展。发电机则可能将启动时间向后延迟(但或不是所有) ，有些甚至可能可以做到淘汰发电机。这一领域的试验和试点可能会在2020年或不久后启动或公布。
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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.)
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