Navigant Research Blog

Data Centers Drive Market for DC Distribution Networks

— July 15, 2015

The market for direct current (DC) distribution networks is not a single, cohesive market. Rather, it encompasses several disparate opportunities—telecommunications towers, data centers, grid-tied commercial buildings, and off-grid military networks—that revolve around different market assumptions, dynamics, and drivers.

Given the expense of current existing redundant alternating current (AC) uninterruptible power supply (UPS) systems, DC data centers would appear to be a no-brainer from an engineering point of view. Despite this, energy remains a small portion of the overall operations budget of data centers. As a result, the value proposition to conservative operations managers may still be a hard sell in the near term. However, DC microgrids can actually offer higher reliability than status quo AC solutions, so validating early adopter DC microgrids is a critical step forward for this market opportunity. The ABB 1 MW DC data center located in Zurich, Switzerland, is just one example of how this application is gaining momentum.

Distributing DC enables replacement of AC-DC converters within individual devices with a smaller number of larger, more efficient converters. LED lighting installations that run on 24V DC lines, for example, require up to 15% less energy than the same lights running on fixture-level rectifiers. Nevertheless, losses in the linings limit 24V DC distributions to just 10 meters, so manufacturers are developing 380V DC wiring to extend comparable benefits to entire data centers and other commercial buildings. Asia Pacific is expected to lead this market in both the near and long-term, with China alone having already deployed hundreds of DC data centers.

DC Data Center Network Implementation Revenue by Region,
Base Scenario, World Markets: 2015-2024

DC Data Network Implementation Revenue

(Source: Navigant Research)

The core challenge facing DC distribution networks lies with the need for standards and open grid architectures that can help integrate the increasing diversity of resources being plugged into retail power grids. Even DC advocates maintain that distribution networks operating at the municipal level may always remain AC systems. The efficiency gains accrued by sticking with DC instead of converting to AC (and then back to DC) are not as great at this higher voltage level. This may remain the sweet spot for AC technology, serving the vital role of interconnecting large wholesale transfers from high-voltage DC (HVDC). In fact, DC microgrids and nanogrids could, ironically enough, extend the life of the incumbent AC distribution system by taking loads off that system in an intelligent and dynamic way.

The focus of the industry, working through the efforts of the EMerge Alliance, is currently medium-voltage DC distribution networks. These systems are mostly concentrated on the data center market segment, but can also apply to commercial buildings—especially those of considerable scale, such as big box retailers (Costco, Walmart, etc.). At present, the majority of progress in developing DC-based technologies has occurred at either the high-voltage (more than 1,000V) or low-voltage (less than 100V) level of electricity service. Since microgrids and building-scale nanogrids typically operate at medium-voltage (roughly 380V to 400V), much work needs to be done to bridge this voltage innovation gap, and this goal is the focus of companies such as ABB, Bosch, Emerson Network Power, and others.

As noted in a previous blog, Bosch is encountering a few regulatory issues when it comes to deploying DC microgrids, primarily an artifact of assumptions that distributed renewables and energy storage are interconnected to the alternating current utility grid. But surprisingly, DC fits in well with AC infrastructure, and is especially accommodating for integrating cutting-edge distributed energy resources.

 

Google Expands Data Center Fleet at Retiring TVA Coal-Fired Generation Site

— July 7, 2015

In late June, Google announced plans to site its 14th massive data center at the Widows Creek Tennessee Valley Authority (TVA)  coal-fired generation site in Alabama.  The $600 million facility will also re-purpose the 60-year-old coal-fired site, which will soon be retired, leveraging existing electric transmission and distribution infrastructure. This infrastructure might have otherwise become another stranded utility asset, ultimately abandoned.  While the data center is planned to be powered by 100 percent renewable energy, access to existing electric transmission infrastructure provides access to renewable power not generated at the data center site, as well as additional backup capabilities sometimes necessary to operate 24/7.

The size of and the electrical power requirements for Google data centers are huge. Google has a history of building creative large-scale data centers, which are some of the largest electric power consumers on the transmission grid.  The company’s data center designs are typically state of the art, utilizing the latest cooling technologies to keep aisle after aisle of servers running at optimal temperatures on a 24/7 basis.  Google’s designs are also known for their creative use of renewable energy where possible.

TVA’s Widows Creek Facility

TVA

(Source: Tennessee Valley Authority)

Model  Behavior

Gary Demasi, Google’s director of data center energy and location strategy, reported that, “The idea of re-purposing a former coal generating site and powering our new facility with renewable energy — especially reliable, affordable energy that we can count on 24/7 with the existing infrastructure in place — was attractive.”

Patrick Gammons, Google’s senior manager for data center energy and location strategy added, “Thanks to an arrangement with Tennessee Valley Authority, our electric utility, we’ll be able to scout new renewable energy projects and work with TVA to bring the power onto their electrical grid. Ultimately, this contributes to our goal of being powered by 100% renewable energy.”

With the seemingly insatiable need for power, infrastructure, and real estate that large data centers have, this 100% renewable data center plan provides a model for other utilities nationwide to use when determining how to redevelop coal plant sites. With the Energy Information Administration’s (EIA’s) recent announcement that the coal plant retirement timetable is accelerating, in part due to the U.S. Environmental Protection Agency’s Clean Power Plan mandate, Google’s clean energy leadership is certainly an inspiration.

 

Data Centers Morphing Into Virtual Power Plants

— February 12, 2013

Source: ABBWhat is a “virtual power plant?” The term means different things to different people in different parts of the world.  Pike Research has come up with its own definition: A system that relies upon software to remotely and automatically dispatch and optimize generation, demand-side, or storage resources (including PEVs and bi-directional inverters) in a single, secure web-connected platform.

At their core, VPPs tap existing grid networks to tailor electricity supply and demand services for a customer, utility, or grid operator.  Without any large-scale fundamental infrastructure upgrades, VPPs can stretch supplies from existing generators and utility demand reduction programs.

The latest VPP model to emerge is based not on geographic proximity – typically the top consideration – but rather on enterprise ownership of global operations.  Ironically enough, the farther away each facility linked in the VPP, the better!  Companies such as PowerAssure are investigating ways for companies that use large global data center operations, such as Apple and Google, to create enterprise VPPs that span the globe, whereby data centers shut down operations and shift load from the regions of the world in daylight to the nighttime half of the globe, where power is cheaper.  The technology to carry out this level of global energy arbitrage – known as “following the moon” – is nearly here (though some engineers may disagree). “Data centers can modulate their IT loads based on external events, such as the price of power, and in the process, save money and get paid for providing demand response (DR) services,” Peter Maltbaek, vice president of worldwide sales for PowerAssure, told me.

Changing Models and Mindsets

The U.S. Environmental Protection Agency (EPA) recently revised rules governing limits imposed upon use of diesel generators that should help increase the availability of DR throughout the United States.  The chief challenge for global enterprise VPPs comes on similar regulatory restraints as well as the accounting end of such transactions.  Of course, if large numbers of large energy users employed this strategy, it could wreak havoc with local grid stability instead of enhancing reliability.  How national and regional regulators would respond to such a business model, based largely on financial flows instead of engineering smarts, is unclear.

Another challenge is changing the mindset of data center owners.  “They need 100% availability and are leery of anyone fooling around with their power supply, especially since it is only typically 3% of total costs,” added Maltbaek.

Lawrence Berkeley National Laboratories (LBNL) released a study last year that looked at data centers and their potential for DR.  ABB, which has invested in PowerAssure and has its own Decathlon DCIM VPP offering for data centers, has already installed a 1 megawatt (MW) DC microgrid at a data center in Zurich, Switzerland providing DR through use of its emergency generators; this system is currently being expanded to 10 MW, will later go to 30 MW, and will then be aggregated with three other data centers in the region.

In Germany, meanwhile, Siemens claims that recent regulatory reforms will allow it to boost its supply-side VPP capacity to 3,000 MW by 2018.  Last year, the company announced that it would increase the capacity of its VPP from less than 10 MW to 200 MW by 2015.  The company says that Germany has enough spare capacity on its transmission lines to create VPPs that span the entire country.

 

A FVER Cure for Data Center Inefficiency

— October 31, 2012

An article in The New York Times on data center energy consumption has brought the debate over the hidden environmental costs of the digital society to a broader audience.  We have examined several of these issues in previous blogs and in our green data center report.

I think the article underplays the efforts the IT industry is making to encourage best practices on energy efficiency, notably through the work of organizations like The Green Grid. But it does highlight one particularly intractable problem: the unproductive consumption of energy by IT systems.  It’s a mark of shame for the industry that typically only 6% to 12% of the energy consumed by IT systems is used to do useful computational work.  This continues to be a problem despite campaigns to get data center managers to turn off idle servers and the availability of tools that can help monitor and manage the power use of IT.

One of the barriers to improvement has been the lack of an accepted metric that enables data centers to be compared in terms of their productive use of energy.  PUE (Power Usage Effectiveness) is now well established as a metric for data center energy efficiency, but it doesn’t capture data center productivity.  In fact, running your IT kit at full power even if it is not doing effective work will improve your PUE score (as IT would be a greater percentage of your energy consumption).

There are several current initiatives to produce a new metric that will account for the productive element of IT energy consumption, giving us a means of assessing which data centers are truly energy efficient.  The Green Grid has produced an initial model and work is also being done in the EU and in Japan, but it’s proving difficult to produce a metric that is both insightful and simple, which has been key to the uptake of PUE.  Now, though, a new metric developed by the BCS Data Centre Specialist Group may have cracked the problem.

Fixed vs. Productive Power

Called Data Centre Fixed to Variable Energy Ratio, or DC-FVER, it can be used to assess the amount of energy consumed for productive work compared to fixed energy consumption (that is, the energy consumed even when the servers are delivering little or no business value).  FVER allows each data center to define a useful work metric that is relevant to a company’s business, so it’s tailorable to different types of data center.  For example, a news website might measure productivity in terms of the number of webpages served per hour, while an online retailer may look at the number of transactions per second.  FVER is defined by the formula:

FVER = 1 + (Fixed Energy (kWh)) / Variable Energy (kWh))

As with PUE, the ideal FVER rating is 1, which would mean all energy is being consumed for productive work.  In reality, most data centers are expected to have scores closer to 10 on first assessment.

A simple example given by Victor Smith, Vice Chairman of the BCS, at the Green Data Centre Conference explains how it might work.  After choosing a useful work metric for a specific data center, the output and the energy consumption needs to be measured, say, every hour for a week.  At the time of minimal work, it’s possible to get a measure of the data center’s fixed energy consumption.  So if in the most productive hour 1.2 megawatt-hours (MWh) are consumed and in the least productive time 1 MWh, then variable consumption is 200 kWh, (the energy consumed for productive work).  In this case:

FVER =  1 +  (1000 kWh / 200 kWh) = 6

FVER will also allow direct comparison between data centers based on their productivity relative to energy consumption.  FVER is only one among a number of approaches to measuring data center productivity, and more complex metrics will also have their place, but it could help accurately assess the efficiency of data centers.

 

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