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Opinion piece: Security of Supply with Renewable Energy – What is possible today?

By Robert Futter, Director at Cresco Group

Renewable Energy (RE) has been touted as a solution for providing reliable and consistent energy supply, but this has often been met with scepticism. As a result, there are a number of myths around renewable energy that need to be dispelled.

Dispelling the myths

The first myth is that solar photovoltaic (PV) panels alone can protect against load shedding. In reality, all renewable energy technologies require Battery Energy Storage Systems (BESS) to provide generation backup, and the sizing of these BESS is important for the length of the security of supply.

The second myth is that wheeling energy can guarantee security of supply, but this does not guarantee security of supply. While some wheeling deals prioritise certain users, these deals have a limited size and duration.

The third myth is that corporates can achieve 100% RE in South Africa. Using the 24/7 carbon-free energy approach, this is generally not possible with current technologies available in South Africa, except for larger loads of around >5 MW.

Defining renewable energy targets

Many corporations have simple RE targets based on a percentage of total MWh consumed. However, this is often viewed by stakeholders as overly simplistic, needing more detail to provide comfort. To provide better detail and comfort, many industry specialists now use the concept of 24/7 carbon-free energy, which involves objectively measuring the actual generation received from renewable sources over a 24-hour period, seven days a week, or a year if there is significant seasonal variation. The concept of 24/7 carbon free energy, developed to counter greenwashing allegations in the US telecoms industry, has become the “norm” by many industry specialists when considering the level of RE penetration within a business based on various initiatives.

The time for generation and storage is here

The following graphic displays the typical penetration of RE in a PV solution, with green indicating the highest production during daylight hours.

To achieve a higher amount of green than grey in the overall picture, a corporate has to have some form of dispatchable energy with a similar or higher load factor. Renewable technologies will require large-scale storage interventions, with BESS being the most common storage solution.

A use case in action

A use case example shows how a corporate requires secure power for its own site. This company currently has onsite gas and diesel to protect against load shedding. A PV-only solution is interesting, but a larger PV+BESS dispatch profile can provide financial and security of supply benefits too.

The analysis considers the “value of PV+BESS vs. other available onsite generation options.”

Onsite PV-only solution offers a large saving as it offsets yellow standard tariffs, while PV+BESS solution allows the use of excess energy generated in the afternoon to be used to offset the evening peak hours.

Dispatch profile over 72 hours

When overlaying all the available generation technologies over a typical 72-hour period onto the load, based on a phased implementation approach, short duration storage is compared to longer duration storage.

In figure 1 there is an overgeneration from PV in the hours where there is maximum sunlight, the BESS is then dispatched in the evening peak periods to conduct peak shaving.
Figure 1: Short duration storage
This company has access to available land which will allow for higher PV generation and long-duration BESS. In figure 2 longer duration storage dispatches over the night periods allowing for a renewable penetration rate of >80 to 90% to be achieved.