Mar 2019

How to prevent loadshedding in commercial buildings

3 Options to proof your commercial and industrial building from load shedding

The nationwide spate of load shedding in South Africa is not just a highly frustrating situation for individuals: it is a hindrance to businesses and the economy in general. As South Africa starts to approach level 5 and 6 load shedding scenarios, it is important to look at the alternatives available to businesses around the country in order to prevent the loss of productivity across the board. At the same time, various different alternative sources of power should be evaluated based on their cost-effectiveness and environmental impact. The following article explores various load shedding prevention methods for commercial and industrial buildings.

Option 1: Using backup diesel generator

Option 2: Retrofitting a grid-tied solar PV system

Option 3: Going off grid using a solar PV/battery microgrid


Option 1: Using backup generators

This commonly used form of commercial backup power consists of diesel gensets that switch on when the power goes off. This is a good option for ad-hoc power cuts in places that cannot afford to lose power, such as hospitals, convention centres and large retail centres.

Before relying on a diesel backup generator, though, the system should be tested with the total load of the building to make sure that it is able to take the full electricity load. If it not possible for the gensets to handle the building’s entire load, an “emergency” scenario – where nothing but the critical systems are backed up – should be tested. An Automatic Transfer Switch (ATS) will be needed to ensure that when the power goes off, the diesel generators are initiated.

Within Eskom’s current loadshedding trajectory, using backup diesel generators is likely to be very expensive, depending on the load size of the building. Diesel itself is much more expensive per kWh than typical Eskom tariffs, and even more expensive when compared with the costs per kWh of solar PV. When evaluating the efficacy of installing diesel gensets, the following questions should be asked:

  1. How many hours per day will the genset(s) be required?
  2. How many litres of diesel are likely to be required?
  3. What are the ongoing maintenance requirements of consistently using diesel generators?
Robben Island has historically used diesel generators to provide the power needed on the island.
Robben Island has historically used diesel generators to provide the power needed on the island.

Option 2: Retrofitting a grid-tied solar PV system

In South Africa, many commercial buildings – hospitals, retail centres, distribution centres, etc – have grid-tied solar PV systems that supply power from the sun during the day. These relatively simple systems are tied to the grid, so they do not provide 100% of the offtaker energy requirement but rather supplement it. Unfortunately, grid-tied solar PV systems do not automatically prevent a building from experiencing load shedding.

Because solar generates Direct Current (DC) power, this needs to be converted into Alternating Current (AC) to be used in buildings as electricity. In order for a solar system to produce usable electricity, therefore, a solar inverter is required. However solar inverters are designed to switch off during a grid outage.

Why is this? For grid-tied solar PV systems, this serves as a vital safety mechanism for personnel that might be working on transmission lines during outages. With solar inverters off, buildings with solar PV systems are prevented from generating power during a grid outage and potentially exporting power to the national grid, which could be fatal for maintenance personnel.

Solar inverters are designed according to international safety standards that require this functionality, which means that grid-tied inverters cannot operate in off-grid conditions. As such, when Eskom goes down, most solar systems do, too.

However, this does not mean that large buildings with solar PV systems do not have options for load shedding. With careful engineering, It is possible to form one’s own “microgrid”, by replicating a fake grid-tied scenario to “trick” the solar inverters into staying on. This requires the use of a generator or battery, and specialised control equipment.

In order to retrofit a grid-tied solar system to operate during load shedding, two essential steps need to be taken. Firstly, the system needs to be isolated from the grid to prevent any exporting of power that could affect the safety of maintenance personnel. Secondly, a voltage forming source is required, in order to provide a reference voltage and frequency to the solar inverter.

Therefore, to prevent a grid-tied solar PV system from going out during a power outage, the following is required:

  1. Hardware that can disconnect the main supply from the grid, effectively isolating the building/facility from the grid.
  2. A diesel generator or battery bank that can provide backup power for the entire facility and provide the necessary voltage and frequency reference to the solar inverters.

These two points require careful engineering and a proper control system to manage the change-over, the dispatching of generators/batteries, and synchronisation of the solar inverters. It also has to oversee resynchronisation to the grid once the grid is available again. This can be automated and should not need any human input. Further, the system would need to be sized correctly in order not to trip under various loading scenarios.

With these two mechanisms in place, there would be a short down-time after an unexpected grid outage, due to the system having to switch itself on and switch to off-grid mode. Once switched over, however, the solar powered electricity which is being generated can be distributed throughout the building.

In order to avoid an outage entirely, it is possible to either isolate from the grid before an expected outage, or have an uninterruptible power supply (UPS) capable of providing continuous, uninterrupted power during an outage.

solar could help Africa's economy to grow

Option 3: Going off-grid: Using solar PV, batteries and Generators to go off-grid

Taking a commercial building off the grid entirely is another, although slightly pricier, option. Solar PV systems, when combined with energy storage, can store excess solar power produced during the day and distribute this later when needed. Solar PV is now one of the cheapest forms of energy, and its distributed nature means it’s perfect for use at source, where it is needed.

However, the costs of batteries and the sophisticated engineering of microgrid systems needs to be evaluated against the building’s requirements. Perhaps, a commercial or retail building operator does not mind paying a premium if that means consistent, clean power. (Microgrids also have particular relevance to supplying power in weak-grid scenarios – such as the one in Cedar Mill Mall which supplements the grid’s 250 kVA with an additional 250 kVA of power).

If your commercial or industrial building is currently using its diesel generators around 30% of the time, the business case for a solar PV and battery combined microgrid will likely look feasible. In a typical stage 4 load shedding scenario, power cuts generally occur for around 7 hours per day. Given the assumption that the energy load in the building is similar throughout the day and that diesel generators are being used to supply power consistently when the grid goes down, this would equate to around 30% of the total electricity consumption – making it a worthwhile investigation.

Whether it is a backup generator, installing a solar PV system with a backup generator or battery, or going entirely off-grid, there are options for commercial and industrial buildings in South Africa to prevent the damage that load shedding can do to business.

Cedar Mill Mall goes solar
Cedar Mill Mall in Clanwilliam is an islandable on-grid microgrid

Aries utility solar PPA in South Africa

Electricity in SA seems bleak, but it’s loaded with opportunity.

Originally published on LinkedIn

What the Eskom’s current state of nation-wide load shedding and their 15% tariff increase appeals are teaching us, it is that the fate of South African industry is tied fundamentally to the availability of stable and affordable electricity supply. The sustainability of the utility requires brave, informed and decisive leadership: but it is possible.

We’re in a landmark year that will determine not only the fate of Eskom, but South Africa more broadly. In May, the country will vote on whether to extend the term of the ruling party in a an uncertain global market.  The ANC’s latest manifesto has clear intentions around energy: more renewables, more private partnerships (IPPs), repositioning Eskom and ensuring fair treatment of South Africans as part of a Just energy transition. It also plans to integrate solar PV in state buildings and new developments.

This year, we’re looking at a year of continued change in a sector that badly needs a modern restructure.

Arriving at today’s energy market

In South Africa, 2018 held much in the way of energy sector developments. The renewables-vs-nuclear stalemate came to an end with new energy minister Jeff Radebe signing 27 long overdue renewables projects. Eskom’s mismanagement was placed under the spotlight and a new CEO, Phakamani Hadebe, was appointed in May. In August, the much-awaited draft Integrated Resource Plan (IRP) was released, showing favour toward renewables and gas and less coal and nuclear. Why the sudden change in South Africa’s energy landscape after years of stagnation?

One answer is that South Africa has started to take heed of global trends toward renewable energy. This is not simply a fad: the upsurge in solar PV technology, in particular, is part of a global market context. According to the Global Market Outlook report for solar energy, solar PV accounted for nearly 40% of all new generation technology during 2017: more than any other power generation technology. This was mostly driven by China, US and Japan, whose overall manufacturing influence also drove the costs of solar modules to record lows. It is undisputable that Solar PV’s cost per unit is now cheapest in the world by a significant margin.  Even more growth is expected in coming years.

The challenges for the energy landscape

Back in South Africa, Eskom has a major debt-service problem on its existing assets. The assets aren’t able to cover their own costs at Eskom’s current tariff rate, which is why they are asking for 45% increase over the next 3 years when inflation is just 5% p.a. Put another way, these assets are worth less than the R420Bn of debt that Eskom borrowed when building them in the first place.This is the primary cause of  Eskom’s death spiral.

The challenge for Eskom, and South Africa, remains that a different electricity path is cheaper. The cold numbers show that the lowest cost model is renewable energy and gas, with no new nuclear builds and limited further coal. This has brought up some valid social issues around transformation and the displacement of employment. These issues are important and need to be tackled head on, they also need to be seen in the light of education, upskilling, entrepreneurship and opportunity.

The opportunities for the energy landscape

The energy minister has recently said that the IRP will be signed off in mid-February.  The IRP draft, combined with the ANC’s policy manifesto, does show willingness to dissolve the electricity monopoly, bring private players into the market, reduce the costs of electricity and stimulate the economy, allowing the government to focus on the key areas of the country that need it most.

The President’s recent announcement of his intent to divide Eskom into separate Generation, Transmission and Distribution entities is not only in line with global trends, but it will also ringfence Eskom’s unprofitable generation assets from affecting its profitable grid infrastructure, which is crucial to our country’s stability as an economic entity.  It is hard to know the series of actions that will follow, but we can be sure that it will be done sensitively in an election year.

We’re already seeing large users of electricity investing in their own power consumption, and when the IRP is released, we’ll see generation licenses starting to be awarded to private embedded generators.  Most of this is, and will be in future, solar PV due to the ease of implementation and abundance of solar resource in South Africa. However, there will also be some cogeneration and biowaste projects too.  These steps are very positive, as they set the stage of a socialised electricity grid with multiple power sources, allowing the most affordable energy to be available to South African industry and encouraging economic growth.

The Future is Bright

We have an extraordinary opportunity for electricity reform in South Africa.  If our renewable resources are harnessed, we not only have 20 years of upskilling and job creation, but with our natural resources we could have, sustainably, the cheapest electricity in the world. If we get the structure right, and manage the transition in the best interests of all of our people, it will be a positive boon for South Africa’s economy. This is a major task, but if achieved, we have a lot to look forward to.