Prefabricated deployment solutions developer Turnkey Modular rolled out the first of multiple solar alternating current (ac), low-voltage/medium-voltage, step-up skid or ‘e-houses’ in July for chemicals and energy company Sasol Chemicals Midlands, in Sasolburg, in the Free State.

The skid will be coupled to Sasol’s 10 MW solar photovoltaic (PV) plant, which forms part of the company’s broader greenhouse-gas emission reduction strategy.

“The majority of the PV plant has been constructed with the necessary joining cables and the foundation for the skid is already in place,” says Turnkey Modular MD and cofounder Warwick Jackson.

The company has worked in parallel with the team at Lead EPC and Sasol to have all aspects of the infrastructure and electrical work completed and on site simultaneously as opposed to a normal sequential approach – this approach has almost halved the execution time of the electrical balance of plant for this project.

The skid, which took about nine weeks to manufacture and weighs 37.2 t, was transported successfully by road from Turnkey Modular’s manufacturing plant in Germiston, to the Sasol Midlands site.

A specialised heavy-duty low-bed truck and crane were used, with the company securing “any and all licencing” required for the skid’s transport.

Once delivered, the installation process took one technician eight hours to be ready for site cabling, says Jackson.

The skid houses dual 2 500 A low voltage panels by multinational power management company Eaton, each with 20 low voltage feeders.

It also holds two dual 1.75 MVA transformers from electrical products manufacturer Zest WEG, with a total output of 3.5 MVA, as well as an onboard black-start solar system and battery storage.

A black-start solar system, complete with battery storage, enabled the substation to be fully functional on delivery.

A black start system can restart parts of the power system to recover from a blackout, he explains.

The unit offers a full telemetry system, with integrated fire detection and internal climate control systems.

The inverters, a key component of drawing power from the solar panels, is connected to a string of solar panels, commonly known as a solar array.

The string inverters harness the direct current from the solar panels, which is then converted to ac in the field and fed to the substation.

“Quite often, this can be done at 800 V and not 400 V, which results in a reduction in costs, less copper, and lower heat losses.”

The Turnkey skid then transforms low voltage power to medium voltage for local distribution, Jackson adds.

This medium voltage power then ties back into one of Sasol’s main distribution substations.

Building a Relationship

At an open day held on July 3, the skid and its operational capabilities were put on display for Turnkey Modular’s clients, prospective clients, suppliers and the media.

Attending the event was senior Sasol employee Leigh Visser who lauded the partnership between Turnkey Modular and Sasol.

“Sasol has worked closely with Turnkey Modular on several successful projects over the last 12 years,” he said, adding that he took delivery of about eight large substations that had been built fit-for-purpose for other projects, in addition to the solar skid delivered to Sasol Chemicals Midlands.

He points out that the fact that the skids require little to no municipal authorisations, and minimal infrastructure, besides a basic foundation, make them perfect for remote applications, with manoeuvrability across a project when and where its power is required.

“The units are essentially a plug-in, hassle-free, high-quality solution,” Visser said.

He concluded that the two companies, their technicians and foremen continue to develop the best substation solution for every individual project and its unique requirements while transforming the delivery execution methodology.