RWE Piller: 6.82 MVA Underwater Uninterruptible Power Supply
The new Service Centre of the Commerzbank in Frankfurt am Main became fully operational in October 2001. Since then all the critical jobs of this large European bank have been handled by the central Service Centre in Mainz’s main highway. This Centre also deals with financial transactions and the provision of the necessary computing power for the smooth operation of the commercial and investment bank. Every system administrator’s nightmare is the thought of a computer centre crash following a power failure. Because of the extensive interlinking between computers, especially in the global financial world, data losses have fatal consequences. Computer centres must therefore not break down under any circumstances. In order to ensure the highest possible availability of their data systems, Commerzbank is using dynamic systems from RWE Piller to protect their power supply. A new type of system with direct water cooling, which reduces the outlay on infrastructure to a minimum, is currently being employed.
Basic Conditions
Due to their limitations, Uninterruptible Power Supply (UPS) systems have an efficiency that is less than 100 per cent, that is to say they produce heat losses. Especially in the case of high-power UPS systems, a not inconsiderable amount of heat therefore usually has to be conducted away from closed operating areas. Typically, an airconditioning plant that is operated in parallel with the UPS system removes the surplus heat and thus maintains a constant room temperature. This “classical” solution brings a few disadvantages for the operator:
• Air-conditioning plants mean investment and operating costs in addition to those of the actual UPS system;
• If for safety reasons the UPS is of a redundant design, the air-conditioning plant must also have built-in redundancy;
• The UPS systems, as well as the air-conditioning, have to be taken into account when considering reliability;
• In highly polluted operating environments, the ambient air which is to pass through the UPS installation must be expensively filtered. Ambient air which is aggressive, corrosive or contains aerosols can be a problem.
New Ways with Proven Technology
RWE Piller has developed a system based on the UNIBLOCK-type dynamic UPS modules, in which the UPS unit and the air-conditioning plant are directly combined.
“Dynamic systems have a clear technological advantage when the protection of sensitive loads in critical applications, such as computer centres, is involved”, explains Karl Staudter, project manager in the Service Centre. “Dynamic systems like the water-cooled UNIBLOCK-RW have the advantage that they electrically isolate the load and the supply network. Harmonics, flicker and other mains disturbances have no effect on the load. We don’t and must not involve ourselves with such things.”
Generally speaking, in previous UPS technology cool air is sucked in and is then ducted internally over the UPS components to be cooled and then exhausted into the room as warm air. In this configuration, none of Piller dynamic UPS systems has vulnerable electrical ventilation; instead, a fan impeller is incorporated in the rotor of the electrical machine, so 100 per cent of the corresponding ventilation power is available as soon as the UNIBLOCK machine is in service and the rotor is rotating. With the direct-water-cooled UNIBLOCK, Piller has gone a step further: the circulating air circuit of the UPS system is completely closed.
An air/water heat exchanger built into the air circuit, which is fed via a cooling water supply, takes up the dissipated heat and removes this from the system via the warm water outlet. Warm and cold water connections are coupled directly to the air-conditioning system of the building supply. With a UPS module having an electrical output of 625 kVA, the residual heat radiation is under 0.5 kW.
The UPS system and air-conditioning grow together with common redundancy. Each water-cooled UPS module also automatically incorporates its own correctly dimensioned air-conditioning components in one overall redundant concept.
Extended Range of Applications
The preferred application of the new concept is in areas where “classical” systems can be installed only with considerable additional technical measures or additional infrastructure, for example:
• In closed UPS rooms, for example also on different storeys where otherwise there are problems with installing the air cooling;
• In areas with high ambient air temperatures (e.g. in industrial environments or in specific countries). In this case the unit can be located close to the heat source, and the sensible heat reliably removed in a defined manner;
• In highly polluted environments. The circulating air circuit of the water-cooled Piller UNIBLOCK is hermetically sealed, i.e. it is totally independent of the environmental conditions. So now for the first time here is a UPS solution in industrial areas for handling materials such as dust, small conductive particles and aerosols, which can be a problem for electro-technical equipment.
System Security and Integration
The failure of the coolant supply is always a factor to be considered in the combined operation of UPS systems and air-conditioning plants. In such a case, the Piller UNIBLOCK with water cooling automatically switches over from liquid cooling to the exhaust air mode, which uses the normal air volumes of the operating area for cooling. Consequently, cooling power is still available, even following a failure of the water supply. In the event of a failure, this extends the operating time and also enables an orderly shut-down of the connected loads. The following cooling parameters are also continuously recorded:
• Air inlet temperature of the UPS;
• Coolant flow;
• Leakage warning.
In addition, the monitoring of the cooling function can be covered by the UPS controller. Then all that is required is an interface to the building services management system.
UPS and air-conditioning plant are merged into one unit.
This reduces investment and operating costs, since separate cooling units are dispensed with and maintenance has to be carried out only during regular UPS inspections, and this requires only one system partner.
The Commerzbank Solution
Commerzbank employs these innovative systems with a total UPS output of 6.82 MVA in its Service Centre. “The effective use of the infrastructure is our prime concern.
Anyway, from a purely physical point of view we wouldn’t have been able to accommodate the number of cooling plants”, Staudter reports. Some 25 of the direct watercooled Piller UNIBLOCK modules are used in this installation. Approximately 70 recirculating air units were eliminated and considerable outlay on infrastructure saved in this way right at the planning stage. Furthermore, two short-term mains failures, which were not noticeable to staff yet were a potential catastrophe for sensitive data, occurred a few months ago. Protected by Piller UPS systems, however, financial business continued unaffected.
Conclusion – Benefits of a High-power Rotary UPS
Apart from the advantages offered by direct integration of the air-conditioning function in the UPS system, the user should see maximum performance and reliability, particularly in the case of the UPS-specific parameters.
The rotary UPS has a clear set of benefits to the end user and has brought together the merits of solid-state technology with those of the rotary machine to provide the best UPS for all-round performance. Is the Rotary UPS state-of-the-art today? Of course it is – after all, there is no solid-state power station just yet!
MICHAEL RICHTER
PILLER
Entry Filed under: Outsourcing/Domain Expertise