Power Security

How benefits of uninterruptible power supply systems are vital for protecting both business data and lives.
Power Security
By Adam Dawson
Tue 03 Jul 2007 06:17 PM

Even in the oil-rich Middle East, power supply cannot always be guaranteed. Huge energy demands come from a need for air conditioning and a construction industry that is growing at a rapid pace. The threat of power failure is a real one, with Qatar experiencing its latest in May and Kuwait's power supplies coming to within 100MW of their capacity in June. The use of uninterruptible power supplies (UPS) is one way to keep power flowing in the event of a mains failure, so that data or even lives are not lost.

"You expect power in this part of the world to be guaranteed, but it isn't and the availability and quality of the power can vary greatly," explains Vipin Sharma, vice president, Eastern Europe, Middle East, Africa and India sales, Tripp Lite. "Power cuts can potentially lead to loss of life in hospitals and businesses need to ensure that their data is protected, so a UPS can be seen as an insurance policy for a company."

You expect power in this part of the world to be guaranteed, but it isn’t and the availability and quality of the power can vary greatly.

UPS systems are typically used to protect computers, telecommunications products or other electrical equipment where an unexpected power outage could cause injuries, fatalities, data loss or serious business disruption. They range in size from units that will back up single computers to those that will power entire buildings or data centres. Larger UPS units typically work in conjunction with generators.

"There are two different categories of UPS systems; on-line and off-line (standby)," explains Derrick Hong, general manager of CPG Facilities Management. "An on-line system provides power from its own internal energy supply, which is charged by power from the mains. A standby system is different in that the load is powered directly by the input power and the backup power only kicks in when the mains power fails." Of these two categories three types of UPS emerge: off-line or standby; line-interactive; and on-line double-conversion technology.

"Standby is the most common form of technology for protecting computers," says Vineet Kajaria, MGE Office Protection Systems. "The UPS passes utility power through to the load until a power cut occurs, at which point the UPS switches the load onto battery power and disconnects the utility power until it returns to an acceptable level." With standby UPS units there is typically a break in power of between 4-10ms during the transfer to and from battery mode.

Line-interactive UPS operate in a similar fashion to standby models except with better filtering and output voltage boost/reduce features. They also reduce the impact of spikes, surges and sags by clipping the peaks and troughs, boosting power or switching to battery backup. As with standby UPS there will be a break during the transfer to and from battery mode, although this is generally shorter.

"On-line double-conversion provides the highest level of power protection available," states Hong. "The UPS converts incoming ac mains supply to dc and then converts the dc back to ac. Because the ac is completely regenerated it is free from any mains-borne interference such as spikes and voltage variations," he explains. This type of UPS is typically used with sensitive equipment or environments where a generator is used to provide backup power to the UPS. Almost all UPS of 5kVA and above are on-line.

In larger installations rotary or flywheel technology can be used, which removes the need for batteries within the system. Unlike batteries, the flywheel UPS uses a mechanical means of storing energy. The flywheel spins around an axis - the motor generator rotor - by the use of magnets in a vacuum. This energy is then stored in the motor generator rotor and released if the normal power supply to a building is interrupted. "This type of technology is used where there is a lot of energy needed, like in airports, metro systems and by utility operators," says Sharma. "They have a built-in generator that operates after the UPS has stopped supplying power.

"There are many benefits to using a flywheel instead of a battery," states Hong. "Firstly, unlike batteries, flywheels don't produce gas so no ventilation is needed when storing them. The typical limit of a battery cell's life is five years, whereas a flywheel UPS has a service life of around 20 years. Placing a flywheel UPS ahead of your batteries will reduce the number of hits the battery receives during power cuts and increases cell life significantly," he adds. Rotary technology UPS systems also take up less floor space than batteries and remove the need to deal with toxic substances associated with their removal.
Despite this, the market appears to be moving away from rotary UPS. "The problem with rotary technology is that it is expensive and can be inefficient," explains Sharma. "Many places are starting to think about using solar technology instead, by placing photovoltaic cells onto the top of buildings in conjunction with generators. Therefore you have power from the sun, mains and a backup generator as well."

In recent years fuel cell UPS have also been developed. Using hydrogen as a power source, the fuel cell replaces the batteries as energy storage, providing long run times in a small space. "This is the future," admits Sharma. "But it is still not commercially available yet and it is expensive technology. The advantage is that the shelf-life of a fuel cell will be ten times more than lithium-ion batteries. In time, as with all technology, the price will come down," he predicts.

Fuel cells are also making their mark within the backup generator sector. Cummins is spending US $54 million (AED198.30million) in research and development to create a generator from a solid oxide fuel cell (SOFC). The system should provide virtually silent power with lower fuel consumption and exhaust emissions than existing generator sets.

The major advantage of using SOFC technology is that it facilitates the use of fuels such as natural gas, liquified petroleum, gasoline and diesel fuel to create power with extremely low emissions. The only waste products are water vapour and a small amount of carbon dioxide. Using SOFC technology will also reduce the amount of noise produced by the generator.

UPS systems: the theoryA UPS is designed to provide an uninterrupted source of electrical power for equipment that requires protection.

Any electrical device that is plugged directly into the mains supply has only one source of power and if there is a power cut the device will go off immediately. Where failure of equipment is unacceptable, a UPS can be applied to ensure it has two power sources: one from the mains - known as the primary source - and another, the secondary source, which kicks in if the primary is disrupted.

This secondary power source is the battery contained within the UPS. A switch controls which of the sources powers the equipment at any given time, changing from primary to secondary when it detects failure in the primary power supply. An inverter within the UPS converts the battery's stored dc electricity to ac so that it can operate equipment; once the primary power has returned, the UPS automatically switches back to that source.

Several manufacturers supply UPS products in the Middle East, with more expected to become available. SmartOnline UPS systems from Tripp Lite offer on-line double-conversion technology for mission-critical applications.The Pulsar MX from MGE Office Protection Systems is a range of high performance UPS upgradeable from 5 to 20kVA. These products are suitable for departmental networks, servers and workstations.

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