Resource conservation was a top priority in designing the Data Center DC 10 in Ostermiething (Austria). Completed in 2018, the new facility with a minimum availability of 99.98 % (TSI Level 3 extended) is the first data center to be awarded a Gold Certificate for sustainability by the Austrian Sustainable Building Council (ÖGNI). While natural cooling with river water plays a key role in the system's eco-sustainability, the required non-stop cooling capacity is ensured by mechanical means – with four GEA BluAstrum ammonia chillers.

Maximizing energy efficiency and availability

The Data Center DC 10 opened in 2018 by Schwarz IT Data Center GmbH (Neckarsulm, Germany) in the Austrian town of Ostermiething achieves an extremely low power usage effectiveness (PUE) ratio of just 1.1. This makes it one of the most efficient facilities of its kind. The resource-conserving design concept was awarded a Gold Certificate by the Austrian Sustainable Building Council (ÖGNI). The remarkable new data center achieves a high availability of at least 99.98% (HA class n+1) and is TÜV certified.

Focus on natural cooling

To minimize secondary energy consumption and effectively combine reliability with energy efficiency, the general planners at dc-ce RZ Consulting GmbH & Co. KG (Frankfurt am Main) implemented the best options for a resource-conserving cooling system. Instead of conventional mechanical cooling, the DC 10 uses river water for its primary cooling system. Project planner Thomas Fischer explains: "The coal-fired power plant that previously operated at the DC 10 site was cooled with 9°C water from the nearby Salzach River. The availability of river water enabled Schwarz IT Data Center GmbH to integrate an environment-friendly and cost-effective climate control system into the data center."
The 1,500 square-meter data center is unlikely to reach the maximum permissible temperature difference of 10 Kelvin between the water drawn and the water returned to the river. Some of the thermal energy is used in winter to heat offices in the building. On cold days, the water flows through two heat pumps before it is discharged back into the river.

Mechanical cooling ensures reliability

The 1,500 square-meter data center. Each rack can draw up to 20 kW of electrical power
The data center has four GEA BluAstrum ammonia chillers installed to serve as a backup for the natural cooling system.

Using river water alone for cooling doesn't ensure 100 % availability. Fischer cites an example: "High water levels can cause flooding of the inlet structure and interfere with heat dissipation." When maintenance work is carried out on the inlet, pumps or heat exchanger that separates the river water from the internal cooling circuit, the system must be capable of handling a return flow of cooling water from the data center that may reach temperatures ranging from 25 °C to 27 °C.
Like the power supply, the DC 10 cooling system is designed to be highly redundant. The data center has four GEA BluAstrum ammonia chillers installed to serve as a backup for the natural cooling system. Each of these units can be regulated to provide up to 875 kilowatts of cooling capacity to feed the cooling circuit with 18 °C cold water from a return flow of 24 °C. Thomas Fischer: "The racks can be reliably cooled by 20 °C circulating air from the cooling units on site." The heat from the server area is discharged into the environment through roof-mounted heat exchangers or fed into heat pumps and used for indoor heating.

Climate control with power grid and raised floor

Four GEA BluAstrum chillers stand ready to cool the data center when the river water cooling system is unavailable
Four GEA BluAstrum chillers stand ready to cool the data center when the river water cooling system is unavailable

"At normal capacity utilization – even without river water cooling – it wouldn't be necessary to run all four GEA chillers at full load," Fischer adds. There is plenty of reserve power built into the backup cooling system. All of the GEA units are supplied by two independent power grids and connected by dual bus lines to a redundant building control system. But that's not all: in the event of a complete system failure, the local control would activate an emergency program and switch all chillers to maximum capacity in order to provide uninterrupted cooling to the data center. The output would be unregulated and probably exceed the level required to cool the racks.
To ensure Schwarz IT Data Center GmbH can always rely on the emergency cooling system, the four chillers used for the DC 10 are run for several hours every month. Operators can use the building control system or the GEA Omni Control on the chillers to check the current operating data and system functions.

Climate-friendly refrigerant: ammonia

Since the GEA chillers used for the data center only operate for a few hours per year and this is unlikely to change in the future, efficiency played a less important role in the selection process. But with an EER (energy efficiency ratio) of 4.9 at full load, the BluAstrum would have easily scored points in this discipline as well. For Schwarz IT Data Center GmbH it was important to ensure that the GEA units work with eco-friendly ammonia (R 717) as a refrigerant and only require about 45 kilograms per chiller (including evaporator/condenser). Using environmentally harmful F-gases was out of the question for the data center. Ammonia has been proven in industrial refrigeration and is exemplary in terms of eco-sustainability: it has zero ozone depletion potential (ODP) and no global warming potential (GWP = 0).

The importance of reliability and availability when it comes to planning and operating a data center is demonstrated by the choice of supplier for the chillers. Project planner Thomas Fischer:

We compared several different bids, but GEA convinced us with chillers designed and optimized to work with ammonia. The company also met our requirement for a good supplier rating."

Fischer explained that it's not only a question of technology: "The availability of replacement parts and a fast response time from the service team also play an important role. GEA convinced us in this respect. And thanks to many years of experience in ammonia refrigeration technology, the company is capable of producing technically-advanced chiller solutions.”