The reality of daily rolling blackouts and systematic load shedding schedules issued by Eskom

Negating The Costs Of Unreliable Utility Supply

Considering the reality of daily rolling blackouts and systematic load shedding schedules issued by Eskom, one has to ensure that critical sites are effectively backed up.

As a supplier and service provider to the Riello Aros UPS (Uninterruptible Power Supply) range, Standby Systems have the experience and technical expertise to support your critical load during the coming months of load shedding.

The backup time given by the UPS is normally calculated at full inverter load. Therefore, Riello Aros RPS UPS battery sized for 10 minutes at full inverter load will vary in terms of the percentage of load that your Riello Aros RPS UPS is supplying.

However, this is not a straight line discharge curve because the lower the percentage load, the better the efficiency of your Elite AGM (Absorbed Glass Mat) VRLA (Valve Regulated Lead Acid) battery. This quality Elite battery is recommended for use in today’s modern Riello Aros RPS UPS systems.

Eskom Load Shedding

If your battery backup of 10 minutes were to support a UPS inverter load of 50%, one can calculate that 20 minutes plus of backup should be achieved due to the battery being more efficient at lower discharge characteristics – providing that your VRLA AGM battery is at 100% of charge when the discharge occurs. When subjected to long daily discharges, the UPS will not be able to sufficiently recharge the VRLA AGM battery for it to achieve top of charge. The battery is limited in the amount of recharge current it can accept without it being subjected to overcharge and permanent damage.

The two main reasons for damage occurring to your VRLA AGM technology battery resulting in premature failure in the current load shedding situation are:

1. Number of Discharges

Daily discharges due to load shedding as currently being experienced are classified as cyclic use and not standby use for the UPS VRLA AGM technology battery. Depending on the design life of the battery of three to five years or ten years, it can be expected that their daily load shedding interruptions of approximately four hours daily, will reduce your batteries service life drastically based on the fact that the battery is now cycling as opposed to its intended standby application.

A VRLA AGM technology UPS battery product is designed to deliver a full deep discharge of between 100 and 300 times depending on mainly the design life and various other smaller factors. Therefore, the daily load shedding expevcted and almost guaranteed for well into the later half of 2015 means that your UPS battery will give less and less backup time after two to nine months of blackouts resulting in permanent battery failure shortly thereafter. This does not take into account the next point which drastically compounds the situation.

2. Depth of Discharge

A Riello Aros RPS UPS is typically used for short discharge times of up to 60 minutes (as the costs to customers for very long discharges are relatively high); which the Elite VRLA AGM technology
battery is sized for. In a “normal” utility supply environment with generator backup, longer discharge times can be achieved which are better suited to the battery design. The design criteria that come into play in this current “abnormal” utility supply environment on the battery are due to chemical factors that impact every battery manufacturer.

In essence, the problem arises when the discharge time is longer than the ideal design criteria of 30 to 60 minutes and is lengthened beyond this to 1,5 to 4 hours or more. This results in the battery being subjected to a very deep discharge where it runs at nearly 100% efficiency and depth of discharge due to the low discharge rate and hence delivers all its available capacity, discharging all its available power to support the UPS inverter. This deep discharge must be coupled to a very in depth recharge of about 72 hours no matter what make VRLA battery is being used.

Although the Riello Aros RPS UPS encompasses intelligent design in that on long discharges it lifts the shut off voltage of the inverter to prevent over discharge of the battery in a long discharge environment which will damage the battery, the capacity taken out must be put back and due to a batteries nature and inefficiencies it takes around 72 hours to achieve this.

This is cannot be achieved in rolling blackout scenarios of daily long discharges. All VRLA AGM technology batteries being discharged before they are fully recharged i.e. achieved top of charge before the next discharge – It generally takes around 72 hours for any VRLA AGM technology battery to reach this point as the amount of current it can take without damage is maximum 10%, so even if your Riello Aros RPS UPS is more than capable of recharging at many different values, it has to be set to a value of maximum 10% of the battery ampere hour rating multiplied by the number of battery strings in parallel. This limits recharge time ability and on a daily discharge basis ends up with a flat battery within 2 to 3 days of the long daily discharges

Conclusion

The rolling blackouts are clearly here to stay. The fact is that Eskom’s maintenance and new projects are in arrears and thus rolling blackouts and load shedding can be expected to continue well into 2015 until the backlog is rectified. There will be no spare capacity to meet the demand on the grid during winter months due to additional heating requirements. It is imperative to understand that your battery cannot be discharged on an on-going daily basis without the need for regular replacement – it is not designed to do this nor can any battery achieve this on a continual basis.

As a Riello Aros RPS UPS customer, we urge you to change batteries timeously and to only resort to deep discharges if it is impossible to use generator backup with a shorter UPS Elite VRLA AGM technology battery to carry your critical load for the start interval.

Unfortunately the current utility supply crisis will most likely result in the same scenario we experienced in 2008. The negative spinoff we can attest to from the previous crisis was the sudden influx of “fly by night” UPS and emergency power suppliers who did not understand the demands on this industry or the technical specifics of this sophisticated product for cyclic applications during on going load shedding. These cheap inferior imports that flooded the market were sold without spares availability or competent service support. The panic buying ultimately resulted in customers wasting huge amounts of money to replace inferior products with competent equipment from a reliable supplier.

This makes the difference when dealing with Standby Systems. Our hands on approach and service orientated mind-set have distinguished us in the UPS industry for the past 11 years.

  • We specialise in UPS systems, batteries, battery charges and are committed to the standby industry.
  • We have a full range of UPS products to support our customers ever changing needs.
  • We only sole source products from reputable mainly European suppliers who are ISO 9001 accredited with good and long track records in SA for these suppliers.
  • We back up our service commitment by ensuring the availability of spares across the range at our warehouse in Johannesburg.
  • Our technicians are handpicked based on their tertiary qualification and receive on-going factory training.

In addition, Standby Systems offers our loyal Riello Aros RPS UPS and Elite VRLA AGM customer base optional in house thermal imaging analysis of batteries during routine service visits. The analysis will identify any hot spots which will indicate weak points in your battery particularly during these demanding high usage times. We have further boosted the availability of several battery newly launched hand held intelligent impedence measurement instruments. The value of these modules rests in their ability to record battery impedence data fo rthe first time in industry and compare readings from one service visit to the next. We have made a substantial investment in the procurement of these sophisticated devises as an additional safe guard to our loyal Elite VRLA AGM customer base that can depend on early problem detection. By tracking and monitoring data, Standby Systems is able to predict VRLA battery deterioration before the failure occurs by never before available cell impedance measurements.

Author G. Bennett, Managing Director, Standby Systems

Sources List