Midstream Estate in Gauteng has implemented a solar farm and battery storage system, providing backup power during load-shedding for about 4,500 households. Residents pay a standby surcharge based on their usage during outages, with a sliding scale tariff. The system has reduced diesel usage by 60%, producing 26% of the estate’s monthly power needs. Challenges remain in managing demand during peak periods, with approval pending to seamlessly switch from Eskom’s power to the estate’s system.
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By Hanno Labuschagne
For about two months, Midstream Estate between Centurion and Midrand in Gauteng has been providing many of its residents with backup power during load-shedding thanks to its own solar farm and battery storage system.
The Bondev-developed residential estate’s power distributor, Midstream Electricity Supply (MES), started testing the system in December 2023.
While the original aim was to have the system ready by August 2023, there were delays in the delivery of a final 2.5MVA transformer that only arrived at the plant’s site on 7 December 2023.
Following testing, the system went live for end users during January 2024.
The solar-and-battery hybrid plant can now produce up to 12MW of power when the sun is shining and 8MW at other times of the day thanks to a large battery energy storage system (BESS) from BlueNova and a network of fuel-powered generators.
Midstream Estate’s solar farm
Around 4,500 households in the estate have opted into a programme that allows them to use power during load-shedding with the electricity generated by this installation.
Residents pay a standby surcharge on top of their regular electricity tariff for this convenience.
The extra amount increases on a scale based on the average hourly consumption during load-shedding.
Surcharges start from R2.30 per kWh if the average hourly usage during load-shedding is less than 0.75kWh.
That increases to R4.60 per kWh for hourly consumption above 2.5kWh.
Other residents can also choose to join the programme on an opt-in/opt-out basis per load-shedding slot using a mobile app.
This requires the installation of a smart switch for R1,000. Those who registered for the programme before the end of November 2023 do not have to pay anything extra.
The table below summarises how the sliding scale for stand surcharge tariffs works.
Midstream Estate standby tariff surchargesAverage hourly consumption measured in previous weekSurcharge per kWhLess than 0.75kWhR2.30From 0.75kWh to 1.5kWhR2.88From 1.5kWh to 2.5kWhR3.45Over 2.5kWhR4.60
The Midstream Energy Plan team told MyBroadband the project reached a major milestone in February 2024, when the system produced roughly 26% of the total monthly consumption for Midstream.
Put differently, the plant was able to provide the estate’s total power needs for six out of the 24 hours of each day in February.
The solar plant delivered over a million kilowatt-hours of electricity to households during the month, or about 222kWh per household.
In addition, the diesel used to power generators to provide electricity to Midstream’s retirement village, schools, churches, commercial centres, and other buildings previously energised during load-shedding was reduced by 60% during February.
The team said it has made great progress in managing the intricate aspects of the project, with the most difficult part being to manage the demand during load-shedding.
Midstream BESS with transformer
The system has some limitations in its current form.
MES cannot avoid load-shedding altogether because the estate’s overall demand exceeds available supply from Eskom, especially during evening peak periods.
“While on a sunny day, ample supply is available and can be distributed, the weekday peak period between 18:00 and 21:00 poses a bigger challenge,” the team explained.
Similar to Eskom’s load-limiting approach, Midstream residents in the programme can only draw up to a certain amount of power during load-shedding.
While Eskom’s load-limited customers can use up to 2.3kW of peak power during outages, Midstream residents participating in the programme can only use up to 1.5kW.
MES is able to precisely monitor residents’ usage because all homes form part of a smart grid and their meters are connected via a fibre optic network.
In addition, backup power is only provided to essential groups — including Midstream commercial tenants, Ascend to Midstream, Retire@Midstream, and Midstream Heights estate — between midnight and 04:00.
Inside one of the Midstream BESS containers
MES is also awaiting grid code approval from Eskom to seamlessly switch over from the utility’s power to its own system.
As it stands, it takes around 10–15 minutes to switch from Eskom’s supply to its own once load-shedding begins and 5 minutes vice-versa.
Its application started early in 2023, and MES received in-principle approval around November 2023.
However, it may take another 9 to 18 months to obtain the final approval and install equipment as per Eskom requirements.
Read also:
How a Cape Town resident got his DIY solar setup to pay for itself in five months
How to keep your solar panels safe from theft, fire and other hazards
A tale of two tax breaks: A look at RAs and solar investments
This article was first published by My Broadband and is republished with permission
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