Computer data centres are springing up around the world to create enormous power and cooling loads. Here, David Blair describes what has been called the ‘world’s greenest’ installation, at Syracuse University in the US, which incorporates combined uninterruptible power, heating and cooling technology based on microturbines.

Last year, Syracuse University – regularly ranked among the top 100 schools in the United States – determined it needed a new data centre. Escalating demand from researchers, students and professors for greater computing capabilities and data storage was straining the campus’ outdated data center, which had been housed in an old brick building for decades.

Constructed in just six months and showcased to the public in December 2009, Syracuse University today boasts one of the world’s most energy efficient and green data centres. The 12,000 square foot (1114 m2) facility – named the Green Data Center – is expected to use 50% less energy and produce fewer greenhouse gasses than traditional data centres.

Key to the Green Data Center’s energy savings are 12 patented ‘Hybrid UPS MicroTurbines’ from Capstone Turbine that power the entire facility. Capstone’s Hybrid UPS is the first on-site power system to integrate clean-and-green C65 (65 kW) microturbines directly with a dual-conversion UPS to provide power for mission-critical loads.

Even better, the low-emission microturbines are the heart of an innovative trigeneration – or combined cooling, heating and power (CCHP) system – that further boosts the data centre’s energy efficiency. For the CCHP system, the 12 microturbines, fueled by natural gas, produce electricity and supply heat and cooling power to the data center and a nearby building.

The Green Data Center is the first in the world to combine a number of advanced technologies, including Hybrid UPS microturbines, absorption chillers, IBM-developed cooling doors on each server rack that use chilled water to maintain constant server temperatures, a rooftop cooling tower and on-site conversion of utility AC power to DC power.

Capstone Turbine distributor BHP Energy, which installed the microturbines, also helped coordinate integration of the microturbines with other on-site energy-saving technologies to achieve the data centre’s high efficiency goals.

 

GROWING DEMAND

 

The Syracuse University project and its energy solution address critical concerns for modern data centres around the world: spiraling energy consumption and costs driven by growing demand for Internet communication, entertainment, global commerce and services.

In 2006, the US Environmental Protection Agency estimated US data centers consumed 1.5% of the country’s electricity – more than all of the nation’s colour TVs combined. And without significant changes, the EPA expects energy use at US data centers to double by 2011.

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Power comes from 12 natural gas fuelled microturbines at Syracuse University data centre

A 2008 report on data centre energy efficiency by global management-consulting firm McKinsey & Company stated, ‘With their enormous appetite for energy, today’s data centers (around the world) emit as much carbon dioxide as all of Argentina. Left on their current path, data centre output will quadruple by the year 2020.’

The Syracuse University Green Data Center, a partnership between the University, IBM and the New York State Energy Research and Development Authority (NYSERDA), is a model for how data centres worldwide can operate more efficiently.

‘We need to understand how to make data centres smart,’ said Chris Sedore, vice president of information technology at Syracuse University, in a project video. ‘This entire process, in terms of modeling and understanding energy use, applies not only to data centers, but to buildings in general.’

 

MICROTURBINES – HEART OF ENERGY SAVINGS

 

Traditional data centers rely on power from the utility and have banks of batteries which keep servers and equipment running during a short power loss.

At Syracuse University, primary power for its new data centre comes from 12 natural gas fueled microturbines. The hybrid design generates power while also using utility power to meet the electrical load demand. This allows the system to operate at the optimum point, balancing electrical requirements and heating and cooling demand. In the event utility power is lost, the system will assume the electrical load.

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In rare circumstances batteries are used as emergency back-up

A 40 tonne battery bank with enough power to carry the maximum load for 17 minutes is available for rare catastrophic situations. It’s highly unlikely, however, that the batteries ever will be used because microturbines are renowned for their high reliability and low maintenance.

Capstone microturbines have only one moving part and incorporate patented air-bearing technology, which means no lubricants or liquid coolants ever are needed to keep the microturbine operating.

Capstone’s Hybrid UPS combines the reliability of conventional UPS with the power efficiency and dependability of microturbines. The Hybrid UPS microturbine operates in multiple modes that allow the data centre to be isolated from the utility yet draw on the utility as a backup power source. Top-level data centers worldwide operate with redundant power systems, each with N+1 redundancy, which means they have more power sources on-site than are actually needed. So if one primary power source fails, another can immediately kick in and keep the facility operating.

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The absorption chiller

The Green Data Center has two trains of six microturbines arranged to provide the IT equipment with two highly reliable power sources.

Steve Gillette, Capstone vice president for Business Development, played a key role in the development of Hybrid UPS. Gillette and other Capstone engineers designed a system (see Figure 1) which consists of two separate inverters, called load control modules (Grid LCM and Load LCM).

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Figure 1: The system uses two separate inverters called load control modules.

Grid LCM acts as a connect inverter, including the integrated protective relaying most electric utilities require to allow a microturbine generator to be interconnected with their system. Grid LCM also is bi-directional, which allows power to flow either to or from the Utility Bus.

Load LCM acts as a stand-alone inverter, meaning that it provides voltage to the critical loads regardless of what the utility bus voltage is doing. Internal to the Hybrid UPS system is a DC connection that ties Grid LCM and Load LCM together, but also allows power to come from the microturbine generator and an external battery storage system.

Although 12 microturbines are installed at Syracuse’s Green Data Center, a maximum of ten are used at one time to power the servers and equipment. Depending on the data center’s fluctuating power needs, the number of microturbines producing power strictly for the center varies from five to ten.

The remaining microturbines don’t just sit idle. Instead, they produce extra power that’s shipped to the university power grid or the building next door. In addition, they provide cooling and heating for the same facility.

The design team at Syracuse considered multiple levels of redundancy. For example, propane-air mixture is available as a backup in the event the natural gas system fails.

 

THREE MICROTURBINE MODES

 

The Hybrid UPS microturbine can operate in three modes – High Efficiency, Standard UPS or Emergency Backup mode. No matter the mode, the system always operates in an N+1 redundancy configuration with the level of reliability required by a productive data centre

High efficiency mode is when the turbine system runs at its ‘sweet spot’ with optimum energy efficiency and is the mode in which the microturbines run the majority of the time. In High Efficiency mode, all microturbines are running and a select number of microturbines carry the data centre load. Power from the remaining microturbines is directed to the university grid or building next door.

A separate heat exchanger captures heat energy from the microturbines’ combined exhaust to make hot water for heating. Included in the energy recovery are two 150 tonne double-affect absorption chillers that convert exhaust heat into chilled water used for air conditioning and to cool the servers.

Normally, about 27% of power consumption in a data center is used to make chilled water. At Syracuse, when the microturbines are running in efficiency mode, operators can pipe extra chilled water and power to the building next door, which boosts energy efficiency even further.

In Standard UPS mode, the system seamlessly switches to utility power as the power source. The data center runs electrically isolated and the turbines are turned off. This allows the data center to operate during routine maintenance or during selective use of turbine power.

The third mode, emergency backup, occurs if utility power is not available as a backup power source. In this mode, the turbines continue to be the primary source of power. The batteries take on the role of back-up power.

For example, power can be drawn from the batteries to make up for a transient power swing as a supplement to adjusting turbine power. The batteries allow the Green Data Center to ride through a full start up time in an emergency.

 

EFFICIENCY THROUGH TECHNOLOGY INTEGRATION

 

The Green Data Center achieves its renowned energy savings and efficiency through the integration of several advanced technologies, many of which never have been used together in a data center setting.

‘Imagine coordinating essentially 12 jet engines, numerous pumps and other sorts of devices to move water around and to push air that’s been chilled through the data center,’ Syracuse’s Sedore said. ‘Coordinating all that has been a significant challenge.’

Ez Khalifa, Syracuse engineering professor noted in the video interview, ‘We don’t intend to use it just as a production data center. We intend to use it as a living test bed, in which we can try the various technologies and optimize these technologies in real time.’

The 12 Capstone microturbines and the tri-generation system are a hallmark of the innovative on-site technologies. In addition, IBM provided $5 million in design services, support and equipment to the project, such as ‘cooling doors’ that use chilled water to remove heat from the server racks. Rather than rely only on air conditioning to cool the large room where the computers are located, the water-cooled cabinets allow each rack to be cooled independently of its neighbors. As a result, air-conditioning needs are reduced, along with energy costs.

Two absorption chillers on-site convert exhaust heat from the microturbines into energy that chills water used to cool the racks and the entire building. The chilled water then is sent to the cooling doors. Sensors monitor server temperatures and are used to tailor the amount of cooling delivered to each server – thus further improving efficiency.

IBM also was instrumental in providing computer equipment capable of operating from a direct current powered distribution system. In a typical data centre, alternating current is delivered by a central power plant through the local utility’s electric grid and then converted to DC to power the servers. This conversion process results in power loss through multiple conversion steps.

The power loss can be reduced by generating DC power using the microturbines or by using ‘Validus’ high-voltage AC-DC rectification.

Another technology that boosts the facility’s energy efficiency is a water-side heat exchanger, which produces chilled water from the cooling tower on the roof. During favourable weather conditions, the cooling tower produces 45°F (7.2°C) water that provides another source of chilled water to cool the facility.

 

EMISSIONS REDUCTIONS

 

Syracuse’s Green Data Center is combating the alarming trend of ever-increasing data centre emissions. Because of the low-emission Capstone microturbines, the Syracuse data centre emits significantly less greenhouse gases than traditional data centres.

By generating power, cooling and heating on-site using a microturbine, facilities use fuel much more efficiently than burning coal at a power plant 100 miles (160 km) away. Off-site power plants throw tremendous amounts of carbon dioxide into the atmosphere. Microturbines, however, are extremely low-emission power sources, and through energy recovery, offer a significant reduction in carbon dioxide.

David Blair is president of BHP Energy, Hudson, Ohio, US – an 8-year Capstone Turbine Corporation distributor.

Email: dblair@bhpenergy.com.

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