FEATURE: Load-Shedding Solutions

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Answers provided by Jack Ward, MD of power provisioning specialist, Powermode

1. What are the leading solutions available for organisations to cope with load-shedding?

One of the leading solutions that enable organisations to cope better with load-shedding is the new long-run battery pack incorporating ‘smart’ technology.
Traditionally, uninterruptible power supply (UPS) systems have been used to help businesses cope with power outages but these systems are not ideally positioned to address load-shedding issues. This is because the prevalence of routine load shedding has exposed one of the Achilles heels of these standby power devices – the shortened lifespan of batteries when subjected to full depletion on a regular basis.

Even specialised, sealed, deep cycle batteries are not able to cope with repeated load-shedding periods, usually ranging from two to four hours. Subject to this challenge often enough, the batteries’ life can be reduced to around six months or less.

Now, a long run battery pack has been launched in South Africa to obviate this problem. It features a comprehensive three-year guarantee – a ‘first’ for the industry.
Underpinning the guarantee is the ‘smart’ technology built into the battery pack. This includes a computerised battery balancing harness that automatically reports – via a ‘cloud-based’ portal – on a range of parameters associated with individual batteries in the pack.

One of the keys to battery longevity is the use of technology to automatically balance load between individual batteries in the pack and gain a thorough understanding of the status of batteries in terms of their duty cycles and load factors.

2. What solar solutions can be used to provide the business with cost-effective and renewable energy?

Solar power – nature’s free alternative – continues to be seen as an attractive, cost-effective ‘green’ solution, particularly when compared to noisy diesel- or petrol-powered generators.
Today, decisions to select solar power as the ‘go-to’ option are being supported by advances in rooftop solar photovoltaic (PV) technology, examples of which include new-generation utility grid-connected, hybrid solar PV power systems.
These hybrid systems function as back-up as well as complementary power sources which set them apart from conventional solar PV power systems.
They can be operated in three modes: linked to the electricity grid (grid-tied); as grid-tied units with battery backup (in a hybrid configuration); or as a stand-alone hybrid units.

3. What does the business have to have in its arsenal in order to prepare for load-shedding season?

A new, eco-aware long-run UPS system is a good weapon. Unlike traditional systems of the past, modern long-run UPS systems are designed to reduce environmental impact by being more energy efficient thus minimising a user’s carbon footprint while saving on electricity costs.

Every kilowatt of electricity ineffectively used costs in the region of R 400 – 500 per month. Today’s UPS systems slash electricity costs by reducing the energy used and heat generated by the unit – both during normal running mode and under full load. Older technology (on-line double conversion) UPS systems are inefficient and waste power which is radiated as heat. This heat also requires cooling systems to work harder, using even more electricity.

The latest UPS systems feature the newest developments in componentry to deliver overall efficiency ratings as high as 92 to 98% – an improvement of between five and 10% on comparable, legacy systems, thus facilitating significant savings while cutting harmful CO2 emissions.
For a modest 20kW load, for example, CO2 emissions can be reduced by around 87 tons per year. In addition, over a five-year period, more than 394,000 kilowatt-hours of electricity can be saved – sufficient to power two average homes for more than five years.

Features of the latest generation of UPS systems include a wide input range, integrated power management software and extendable run time options often backed by a network interface which allows load levels to be monitored remotely via SNMP (Simple Network Management Protocol) links.
This level of highly efficient technology presents opportunities for on-line monitoring and control functionality which allows for small yet vital daily cost savings that amount to a considerable total in the long term.

4. What are the biggest issues to avoid and pitfalls to dodge when it comes to preparing for load-shedding season?

While small-scale solar PV systems are increasingly sold in hardware stores and builders’ supply depots, users should resist the temptation to effect a DIY installation.
Although most roofs can support the added weight of a solar energy system, some can’t. It takes a professional – preferably a structural engineer – to check the condition of the rafters and assess the capability of the roof to safely support the added dead load of the solar array, the mounting rack and the temporary live load imposed by the installation crew. (Unsurprisingly, the latter calculation is often omitted by DIY’ers.)

While the type of solar panels and the number to be installed will need to be professionally selected and calculated, it’s important to choose a manufacturer that will back its products with an optimum performance guarantee of 80% over a 25 year period and offer panels with an expected lifetime of over 30 years.

Grid-tied PV systems should be interconnected by a licensed electrician while solar hot water systems (often employed in tandem with a solar PV system) should be installed by a licensed plumber.
Choosing a solar PV inverter also requires expert intervention. The inverter converts solar energy to electricity and will also have to be expertly sized and selected. Many inverters are energy wasters. Choose one that isn’t.

In most grid-tied installations, the building’s electrical demand may be determined and used to specify the inverter needed for the solar PV system. In other cases, however, the estimated peak array output is used as the basis for specifying the inverter.

In a remote or stand-alone solar PV system installation, the average daily electric load of the building needs to be calculated first. The building’s electric demand should include the Watt demand of all AC loads running at the same time, plus the wattage from the surge of starting motors, and all DC loads operating simultaneously. This demand should be further increased by a factor of 1.2 to 1.4 in order to account for inverter losses.

In both grid-tied and remote site situations, the initial estimate of the inverter’s capacity may be impacted by future plans, such as increasing the size of the PV array. This needs to be accommodated at the planning stage by a professional PV system engineer.

Eskom produces electricity that is a true sine wave. A modified sine wave inverter produces a slightly squared off electrical waveform, but some computers, power tools, refrigerators and most other powered equipment can use this generated electricity.

On the other hand, pure sine wave inverters produce a true sine wave that is the same as Eskom’s which is needed by high-end audio and other specialised equipment that are electrically sensitive, such as life support systems.

Importantly, in grid-tied installations the inverter must be able to be shut down rapidly in situations where utility power goes down. This is called anti-islanding and is a safety function for any Eskom personnel and electricians who may be working on the lines in the area. An off-grid system will require storage batteries (the number and capacity are critical) and – usually – a backup diesel or petrol generator to take up the slack on cloudy days.

5. What business recovery strategies do you need to have in place?

Recovering from data loss from an unprotected power outage can be a costly business. Grocery retailers, food producers, fast food restaurants and supermarkets are among the hardest hit by South Africa’s on-going electricity crisis. Lost trading hours and wasted food are among the biggest concerns.

Information disseminated by a large retail chain estimates the cost of a power outage at over R 60,000 per hour in lost sales per outlet.
Research seems to show that shoppers are reluctant to enter a store when the lights are out. This has placed an increasing emphasis on the efficiency and reliability of backup power systems, including inverters, uninterruptible power supply systems (UPSs) and diesel generators.

While many stores have installed generators, these units are unable to immediately restore power for lighting and the check-out counter tills when load shedding occurs. This causes all tills and security systems to power down and then re-boot when the generator comes up to power. This can result in shoppers abandoning their trolleys and leaving the store. What’s more, power ‘spikes’ can occur when grid power is re-established in installations without the necessary power management devices, such as in-line UPSs. These power ‘surges’ can end up blowing fridges and freezers, resulting in further losses and additional waste.

An alarming lack of maintenance of many backup systems has resulted in conditions that are ripe for disaster as the harmful effects of load shedding impact the retail sector.
Without regular servicing, generators may well not start or run effectively when called up to do so in an emergency. Much like an insurance policy, the value of routine servicing may not be immediately apparent, but in a crisis situation a maintenance plan will be priceless.

Importantly, any power outage, particularly at night, is a signal to criminal elements that security systems are down and lights are out, presenting an ideal scenario for shop-lifting and looting.

6. What are the best solutions for the SME, midsize organisations and large organisations – and why?

Rooftop solarPV solutions are among the best at addressing power provisioning problems while providing businesses with more effective energy returns and boosting the limited availability of Eskom power where this occurs.

One of the newer solutions pioneered in South Africa is a new installation paradigm for solarPV that allows for efficient renewable power generation for business needs – no matter what the size of the organisation.

This solution flies in the face of conventional wisdom which maintains that solar PV panels should be orientated towards north in the southern hemisphere.
This orientation, from a solar power production standpoint, produces a ‘bell curve’ reflecting power increases throughout the day peaking at midday and gradually falling again to zero at sunset.
However, South African engineers have found that a convention-breaking, east-west orientation is more advantageous, particularly when boosting an Eskom power supply unable to satisfy the business’ full demand. This meets twin goals of matching energy production to the business’ measured load profile with maximum financial benefit.

It is noteworthy that the lower peak output of an ‘east-west’ system compared to a north facing installation (the flattening of the power production bell curve) means that the inverters can be over-panelled by approximately 10% without any change to the inverter system or balance of plant. In addition, the east-west installation results in approximately 5% lower installation cost because the brackets and mounting material are used more effectively and the panel density on the roof can be as much as 30% higher, allowing for a higher yield per square metre.
Independent tests confirm that the east-west oriented system is comparable to a north-facing system on a ‘cost of energy’ versus a ‘kilowatts peak (kWp) installed’ basis. (kWp is essentially the rate at which a solar PV installation generates energy at peak performance.)

However, when the added advantages of over-panelling the inverters at a fraction of the cost of the entire system is maximised, and the lower cost of installation is taken into account, an east-west orientated installation is seen to provide significant cost advantages over a north facing system.

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