The future of UPS for data centres? It’s been with us for quite some time.
Data centres are getting larger – and that trend is set to continue. Demands for increased profitability, better operational reliability and environmental concerns are key considerations for data centre design – and these demands have a strong bearing on the design of uninterruptible and backup power supply for data centres. There is much evidence to suggest that state-of-the-art rotary systems are much better suited to the needs of modern data centres than traditional battery-based UPS systems.
A key benefit of rotary UPS (RUPS) lies in its simplicity. The economic benefits and superior operational reliability of flywheel UPS systems means there is no longer a need to install tons of environmentally hazardous metals in data centres.
Static and rotary UPS compared
For a typical 9MW data centre split into 9 by 1 MW halls, the IT equipment required to provide the N+N connectivity, fault tolerance and concurrent maintainability to meet UTI Tier IV standards is dual chorded, supplied via an A and B UPS system, with each distribution system having a mains supply and a capacity generator bank.
To meet these same Tier IV classification requirements, the equivalent flywheel solution is simply a rotary UPS with kinetic energy in an IP-Bus configuration, coupled with generators and distributed to the dual chorded IT equipment.
Comparing the Total Cost of Ownership (TCO) of both systems over a period of 20 years – and taking a variety of factors into account – we can conclude that the capital cost of the Piller Flywheel Energy Storage system is slightly lower than the alternative. And in terms of operating costs it is over 30% more economical than the leading static alternative.
As with all facilities, it is ‘white space’ rather than power infrastructure which earns revenue. Maximising white space therefore, increases revenue opportunities – just as reducing space required for power infrastructure delivers reduction in building costs. Because flywheel solutions require 2.5 times less space than battery solutions there are considerable benefits to the cost/white space balance.
Reliability is also a key consideration. As there is no available database to assess the relative reliability of energy storage devices, evidence is anecdotal but no less valid. For a wet cell lead acid battery, a Mean Time Between Failures (MTBF) of approximately 880,000 hours can be assumed – against a MTBT of approximately 150,000 hours for a so-called maintenance-free battery.
Battery failures can only be prevented by regular maintenance and the installation of battery monitoring systems which measure the voltage of individual cells or blocks of cells so that deviations can be signalled.
Flywheel energy storage devices on the other hand, allow for a more precise calculation of their reliability because the data from their components is almost always known.
MTBF values of up to 3.4 million hours are typical for flywheel energy storage devices. They are, therefore, quite clearly more reliable than batteries and they offer the additional advantage of low maintenance outlay.
Piller Flywheel UPS – the ideal green solution
Governments and clients are now paying close attention not only to facilities’ environmental impact, but also their sustainability. Where battery systems produce increasing amounts of hazardous waste, flywheels offer a system in which almost the entire product is recyclable. A further environmental disadvantage of battery systems is that they need to be completely replaced up to 3 times over a 20-year life.
Five key factors that make Piller’s flywheels the ideal green solution:
- 97% energy efficiency
- Reductions of ongoing carbon emissions
- Reduction of pollution from wasted electricity
- 90% less carbon produced during manufacture compared to traditional batteries
- Permanent storage frees facilities of toxic chemicals
Further to this, flywheel systems remove the need to install, remove, and recycle thousands of pounds of batteries multiple times over a system’s life.
With Piller rotary UPS, the power supply can not only be secured with the system, installation can also be designed to reuse the heat from the system (as can be seen in the world largest Public-Private Partnership hospital in Stockholm, where Piller systems produce winter heating and hot water supply for the entire hospital complex).
The supply comprises two IP-Rings 24kV, with 5x UBTD+2250 with POWERBRIDGE in each ring. Total capacity 25MVA (22,5MW).