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Securing a reliable source of backup power

Dependence on a reliable and stable source of electrical power is a part of everyday life, whether for an individual or a business. There is, therefore, hardly a person in South Africa who would not have been affected to some degree when Eskom implemented load shedding for about a week during February this year.

Eskom’s woes have been well documented and widely publicised elsewhere, so I won’t go into the impact of load shedding other than to share an interesting estimate by industry experts that each stage of load shedding costs the country roughly R1 billion per day, i.e., stage 1 costs R1 billion, stage 2 costs R2 billion, and so on and so forth.

It is easy to get overwhelmed by these enormous figures and get sucked into the general doom and gloom, but there is no getting away from the fact that power delivery problems are going to affect us for years to come. In the security industry the implications are not only in terms of cost to often expensive equipment, but potentially more severe threats to the safety of assets and people. It is therefore especially important to have power protection and backup systems in place, and to plan for the worst.

One of the most powerful tools available for achieving this is the UPS (uninterrupted power supply), as it can perform both functions – providing a backup power source and protecting equipment connected to it. The most obvious source of surge damage to electrical equipment comes in the form of lightning, but surges caused by the power going off and coming on again are also a threat.

Don Drennan founded Drensky Technologies to provide a full ecosystem of power protection and backup solutions, and knows all too well the threats posed by power disruptions such as load shedding. “We see a lot of latent-type damage caused by switching off and on of equipment, and this can be to the UPS itself and to the equipment connected to it,” he explains.

Protection provided by a UPS

A UPS provides protection from surges by supplying a stable voltage that buffers downstream devices from a certain amount of irregularities in the incoming supply, but determining the right type and size of UPS is a multi-faceted problem. “Firstly, you need to know how much power the UPS needs to be able to supply in the case of a power failure. Ideally we would use a device to measure the actual current consumption at the distribution board, but this is not always possible.

“That is because the steady-state consumption while equipment is operational is not enough to fully specify the UPS required. A major factor is the inrush current, which is the initial current surge drawn by equipment when powering up, and is higher than the steady-state current. To measure this we would need to shut off the power completely and start it up again, which is not viable for certain types of operations,” says Drennan.

One also needs to take into consideration future growth – a company might have 30 computers today but plan to have 60 in six months’ time. “You don’t want to start re-designing your backup power system and buying a new UPS in those circumstances,” Drennan states, “you want to have that in place now, or at least the infrastructure, or a system that is scalable. So let’s say you have a 5 kVA load and you’re planning on upping that to 7 kVA at a later stage – in this case you could put in a 10 kVA UPS to allow for that. With scalability, if your requirement goes up to 12 kVA in the future, you can then parallel it with another 10 kVA unit to increase the overall capacity.”

Besides its raw power output capabilities, there are a number of different types of UPS that are best suited to different applications and budgets. Drennan identifies the following three predominant types:

1) Offline, where the UPS system switches over to the inverter when the power goes out. This provides very little protection, if any, and is mainly used for non-critical applications as a backup source of power only.

2) Inline or line-interactive, where power continuously goes into and comes out of the UPS. This provides some voltage regulation protection depending on the quality of the UPS, and automatically switches over to the inverter when the power goes out. This will assist with power failures, sags, some types of surges, brownouts and brief spikes in the power grid.

3) Online, of which the higher-end models act like a sort of mini power station, using incoming power to create its own source of ‘clean’ power at the output. This will assist with power failures, sags, some types of surges, brownouts and brief spikes in the power grid, as well as line noise, frequency variations, switching transients and harmonic distortions.

The cost of a UPS is directly related to the quality of build components, the protection provided and its efficiency, which is represented by its power factor rating. The more expensive models provide a higher power factor, which essentially amounts to less wasted power. There is also a choice between transformer-based and transformerless models, the former of which is more resilient to power problems and better suited for harsh industrial environments, but comes with a bigger price tag.

Plan for things to get worse

The range of choices and considerations mean that, unless you’re an expert yourself, you’re probably better off consulting with a specialist, but it would be unwise to just hope that Eskom’s power delivery problems go away any time soon. “If you have a look at the companies that have been proactive and had all their systems in place, and especially the maintenance of those systems, they were much less affected by the load shedding,” Drennan points out.

“It’s the people who sit on the fence and wait to see what happens, who end up in a panic when the worst does happen. We are then faced with a supply problem – we just can’t get these things in fast enough and everybody wants them at the same time. We know Eskom is in trouble, we know it’s not going to be fixed in the next six months to a year; if anything it’s going to take at least five years before they actually get on top of things. So you can expect there are going to be outages, whether they call it load shedding, maintenance or whatever. It is going to be a reality and we are going to have a lot more of it over the next five years.”

The power of solar

Another way of reducing reliance on Eskom is by harnessing the power of sunshine, of which we are blessed with plenty in this country. The biggest argument against using solar power has always been the high capital outlay of installing a system, but it can pay for itself in a surprisingly short timeframe if done right.

One company that’s made effective use of solar power is Mustek, which in 2013 installed nearly 1000 solar panels on the roof of its main building in Midrand, at a cost of R4,3 million. These provide 213 kW of power under ideal conditions or realistically around 190 kW on a good day, which is enough to power the building with some to spare. Combined with the installation of LED lighting costing

R2,7 million, the total investment amounts to R7 million. That is more than most companies will have to throw around, but the 40% reduction in energy consumption and costs it has yielded means it paid for itself in just 3,5 years.

Mustek’s installation is a grid-tied system that uses solar power to generate electricity only during the daylight hours and relies entirely on Eskom overnight, rather than storing it in batteries. This is due to the high cost of batteries, but the company is monitoring this as the cost of buying electricity from Eskom potentially changes in the future.

The success of its solar power project has meant the company recently also installed 200 solar panels on the roof of its MST (Mustek Security Technologies) division in the same Midrand building complex, which generates in the region of 50 to 60 kW.

Behind the scenes into the making of a solar power solution

Specialised Battery Systems is a designer, supplier and installer of solar PV (photovoltaic) energy solutions which are generally custom-designed to suite a client’s specific requirements and unique issue it may have in terms of energy. The company designed one such system for PD Nixon Holdings, a company specialising in the mining/manufacturing sector.

PD Nixon Holdings is primarily involved in container conversion and light engineering, which involves the use of tools and machinery that use electricity as a power source. The electricity bill, while not massive relatively speaking, is significant as an overhead in the business. In addition, significant cost increases were expected from the utility over the next few years, which would only increase the cost disproportionally.

In terms of solutions, options were limited. The one option considered was to run a generator during peak loading times. However, while this is fine for load shedding, the cost of running a generator regularly is too expensive – more so than using electricity. Another alternative was to find ways of reducing consumption without impacting on production, however any reduction of electricity usage would be negligible. In short, only a cheaper source of electricity would have an impact.

Implementation

While alternative energy forms such as wind generators and solar thermal (solar water heating) were all options, it was obvious that solar PV would have the most direct, most significant and most immediate impact on reducing the cost of energy consumption.

The aim was to reduce energy consumption from the grid and thereby reduce the cost of electricity consumption. A grid-tie solar system would achieve this and has been proven to achieve this in a relatively short period of time.

A number of grid-tie solar solutions were offered, as available and useable roof space was no problem. PD Nixon decided to opt for a smaller system to start, which would as a minimum supply 30% of the current usage on an annual basis. This 30% saving – which equates to around R60 000 per year, will go straight to the bottom line.

Since Specialised Battery Systems has a large amount of experience in installing these systems, once the client decided which way he wanted to go the process was smooth and faultless. Specialised Battery Systems managed the whole process from design, through procurement to installation and commissioning. As it had supplied PD Nixon with another system previously, the latter was happy to let it proceed with the whole process.

Measuring progress is possible in two ways:

1) By installing power meters and measuring consumption for one to three months, then doing the same after the installation of the PV system. A comparison of the numbers will quickly show what savings the solar PV system is making.

2) By merely comparing the electricity charges from the utility from before and after installation.

The client opted for option 2 as there are additional costs attached to metering, and the time delay factor also played a role. In addition, the system’s output is monitored online on a permanent basis and the client is supplied with monthly output figures for its solar array.

Review

The client’s aim was to reduce its grid supplied electricity usage and reduce costs. The solar system chosen by the client was designed based on worst-case scenario. The system offered a reduction in grid usage of approximately 40 000 kWh per annum, but the reality is proving to be some 10% to 20% higher than that.

The project (or at lease phase one, since the customer will most certainly double the system’s size) consists of a 26 kW solar array and a 27 kVA Fronius 3-phase inverter. The array is mounted on Schletter non-penetrating brackets and profiles. The system was installed in 5 days – from the time the first bracket was laid to commissioning. Because the cost of summer power is relatively cheap @ R1,03 per kWh, the system will pay for itself in 3,5 years instead of inside 3, but is still a very viable investment.

For more information contact:

Don Drennan, Drensky Technologies, +27 31 940 0463, [email protected], www.drensky.co.za

Mustek Security Technologies, +27 11 237 1000, [email protected], mst.mustek.co.za

Specialised Battery Systems, +27 11 425 3447, [email protected], www.special-battery.co.za

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