Zest Energy, part of the Zest WEG Group, is experiencing robust growth across the African continent in three key energy generation arenas — power generation, substations and co-generation.
“Although our company started out with an initial focus on power generation, we soon recognised that every power plant needs infrastructure and out of this necessity the other two segments have emerged,” Zest Energy managing director, Coenraad Vrey, says. “Being part of the WEG Group has given us invaluable access to WEG equipment, services and technology, as well as the group’s decades of international experience in substation and infrastructure projects, notably in developing regions like South America.
“The solutions we’ve been proposing to customers are therefore comprehensive, innovative and cost effective and have placed us in a leading position in southern Africa. Our differentiator is being able to supply total integrated solutions specific to power and infrastructure.
“The power plants we build are fit-for-purpose which means we don’t have specific agreements with OEMs — instead we utilise the equipment that will provide a unique solution for each customer. We understand the significant capital cost requirement involved in building a power station and the Zest Energy team’s depth of engineering experience on power plants enables us to specify the most appropriate equipment for each application.
“Most of our work is currently taking place outside of South Africa, with many of these projects in remote areas, so the systems we’re familiar with installing are multi-functional, with standby units that assist with voltage stability and protect against equipment and production loss in the event of a power interruption.”
Zest Energy is presently working on a generator upgrade contract awarded by Barrick Gold at its Bulyanhulu operations in Tanzania. Scheduled for completion in September 2012, this contact was awarded amid tough competition and involves the supply of a bank of six 2 MW Caterpillar containerised generator sets. This equipment is being integrated into the existing network of 20 generators of various sizes already in operation on the mine and Vrey comments that the challenge was to integrate the off-the-shelf, standard generators with the existing plant infrastructure, which often has limited functionality. To provide local support and in line with local government requirements, Zest Energy is exploring the opportunity of establishing a dedicated office in Tanzania.
The company has just completed another generator upgrade project at Lonmin’s Western Platinum Refinery in the Brakpan area. The project involved upgrading the existing 2 MVA prime power generators with two new 2.2 MVA power generators that run in parallel when necessary to support power supply to the refinery.
Substations and reticulation
The Zest Energy team focuses on two main types of substation and reticulation projects — fixed conventional outdoor substations, typically up to 275 kV, and mobile substation solutions with a variety of voltages to meet different customer needs.
“Much of the existing power infrastructure in Africa is more than 30 years old, so a high proportion of our work in this arena involves upgrading of live substations via a phased approach,” says Vrey. “Here we draw from WEG’s experiences in recommending a combination of power generation plants with electrical integration solutions that stabilise the network. This is a safe, cost effective and flexible approach that takes into account future expansion and improvements as well as long term maintenance and support.”
Zest Energy is poised to complete an upgrade to Metorex’s 220 kV Kasumbalesa substation in the Democratic Republic of Congo (DRC). This project involved the rigging, positioning and testing of a new transformer to energise the substation’s existing transformer bay, and the replacement of the ageing high voltage electrical equipment. Building on WEG’s success in other parts of the world, this is Zest Energy’s first fixed substation project and the company’s first project in the DRC.
Zest Energy’s mobile power solutions came into being against a background of the high capital cost required for permanent and fixed power generation and substation installations. Today the company manufactures mobile generators with the ability to feed power to multiple locations, which Vrey says is by far the most cost effective approach. In areas where infrastructure is required, mobile substations ensure that the power supply is not interrupted during the construction process.
“Where mining operations have a lifespan between five and seven years, mobile substations present the perfect solution in terms of being temporary equipment integrated as part of the overall electrical infrastructure and the reduced delivery periods associated with such equipment facilitates quick solutions for electrical network problems,” he comments.
“Backed by WEG’s success with mobile substations in Brazil, Zest Energy is now manufacturing this technology in South Africa with a high local content. WEG has also sent a mobile substation specialist to assist over the next few months with the growing demand from the African market.”
Zest Energy is about to complete a contract awarded by Eskom for the design, construction, supply and commissioning of four 22 kV mobile distribution switching substations, in line with the power authority’s policy of standardising this equipment across the board. Custom trailers were designed to suit Eskom’s standard equipment dimensions and to remain within the South African road ordinance. This project involved a complete custom-designed solution that included the supply of four 22 kV medium voltage switchboards.
Co-generation – Biogas
With a worldwide focus on saving energy and harnessing the heat produced by operating equipment, Zest Energy is having a great deal of success in integrating this power source with the overall process to improve efficiencies and reduce production costs. While effectively recycling the energy inherent in production processes, this approach also reduces harmful emissions such as methane and cuts down power overheads.
“We’re also introducing tri-generation to our customers, which involves generating electrical power, harnessing the heat produced by the operation of the mechanical equipment to optimise the process and further using the heat produced to provide cooling through the use of equipment such as absorption chillers,” Vrey adds. “In this emerging area of our business we draw on our Spanish technology partner and generator set manufacturer, Guascor, for whom Zest Energy is the local distributor, as well as WEG expertise and the expertise of the other companies in the Zest WEG Group. This means that we offer one point of contact to give our customers access to a complete power generation offering.”
Principal contractor WEC Projects has awarded Zest Energy a contract to complete the co-generation and electrical integration solution as part of Johannesburg Water’s first municipal waste water biogas to power plant with heat recovery. The project is currently being executed at the Northern Waste Water Treatment Works (WWTW), after which it will continue at Driefontein WWTW. In total at both project sites, five containerised Guascor SFGLD240 biogas generators will be installed and commissioned. Zest Energy has drawn in expertise from other companies in the Zest WEG Group for this project, including EnI Electrical and Shaw Controls.
Co-Generation – Steam
Zest Energy also focuses on the generation of power in the sugar and ethanol as well as paper and pulp industries. In these applications, steam is created by heating water at high temperatures in a boiler. The heat for the boiler is produced by the burning of various types of fuel matter, which in these industries, is usually some form of waste material left over as a result of the product manufacturing process.
Within this industry, Zest Energy supplies steam turbines manufactured by Brazilian turbine manufacturer, TGM Turbinas. The association between WEG and TGM has been a longstanding and fruitful relationship over the last two decades. As a result, the alternators for use with these turbines are sourced directly through WEG, which gives Zest Energy the opportunity to supply a complete turbo generator set for this segment of the market. Further to this, Zest Energy endeavours to grow the local market by building on the experiences and many successes shared as a result of the past relationship between WEG and TGM Turbinas.
Recently, Zest Energy was awarded a contract by Mondi Limited, Richards Bay for the design, manufacture, delivery, complete installation and commissioning of their first steam turbine in South Africa. A new 48 MW multi-extraction condensing steam turbine will be installed to utilise the additional high pressure steam provided when running the plant boilers at full load. The power generated will then be used for internal consumption as well as for export to the utility. The scope will include the supply of the turbine, condenser, lube oil system, alternator and all other ancillary equipment required to guarantee a 98% availability factor. The contractual completion date of the project will be October 2013, after which the equipment will be supported and maintained by Zest Energy as part of a long term service agreement with Mondi.
