Johannesburg, 29 Sep 2014
Schneider Electric, a global specialist in energy management, has signed an agreement to design, install and manage the distributed control system (DCS) for the two concentrated solar power (CSP) plants, Khi Solar One and KaXu Solar One, located in the arid land near Upington in the Northern Cape province of South Africa.
The solar project, which aims to create a clean energy future for South Africa by allowing the country to reduce its dependence on fossil fuel for power generation, specifically coal, is owned by international developer Abengoa, in conjunction with the Industrial Development Corporation and the Khi Community Trust.
Construction of the 50-megawatt CSP tower named Khi Solar One was completed towards the end of 2013. It is 205 metres tall and will be the first operating across Africa alongside the 100-megawatt CSP parabolic trough plant, KaXu Solar One, which is the first to utilise this technology in South Africa.
Both Khi Solar One and KaXu Solar One use advanced dry cooling technology, which means they will use about a third of the water consumed by wet-cooled power stations and a fraction compared with irrigated farms, which draw water from the Orange River that runs through the province.
The power tower plant will also use superheated steam receiver technology to improve the generation performance. High pressure saturated steam can also be stored in accumulators, which are huge storage tanks situated on the ground. There is capacity for about two hours of thermal storage in Khi Solar One. According to Pedro Moreno Valderrama, renewables solution architect at Schneider Electric, the saturated steam can be withdrawn on demand to be conditioned in an independent superheater and feed the turbine, allowing overnight power generation or during transient periods with cloud coverage. Serving the same purpose, in the case of Kaxu Solar One, is a full-load molten salt storage capacity of two and half hours.
"The Schneider Electric DCS solution will be responsible for controlling and operating one of the world's largest CSP tower projects and the first of its kind in Africa. The Khi Solar One plant extends over an area of six square kilometres, with a solar field consisting of more than 4 000 heliostats of 140 square metres each," says Moreno Valderrama.
He highlights that with the Schneider Electric DCS solution, both Khi Solar One and Kaxu Solar One's plant operators will have the ability to control and supervise all solar plant processes, including power block and solar field areas, in accordance with the most current technology. "This will allow operators to manage the position of the heliostats and the solar power trough collectors in order to efficiently capture the sun's energy over the entire course of the day, making the anticipation of climate conditions possible and the conversion of solar energy more reliable and cost effective.
"A high-precision sun tracking algorithm, implemented in our solar tracking controller, accurately positions the mirrors and can be used for either single (parabolic trough) or dual axis (heliostats) tracking systems. All the needs for a mirror tracking control integrated into the same board, including fibre optic upstream communications, electrical protections and solid state relays, reducing the number of elements and simplifying the tracker control cabinets design for these projects."
Schneider Electric's DCS solution manages the Khi Solar One and KaXu Solar One's operations at three levels: the physical solar field elements and data acquisition, the communications network and concentrators along the solar field, and the main controllers for the plant operation. As highlighted by Moreno Valderrama, a programmable logic control application adjusts the position of each parabolic mirror according to the angle of the sun's rays and the security parameters to maximise energy generation. The system communicates thousands of real time data among the mirrors, the three receivers on the top and the weather system to provide vital information for monitoring and controlling the solar field. At the plant itself, the DCS manages data in a user-friendly interface to create an efficient system that streamlines plant operations alongside a data analytics platform for business intelligence purposes.
In addition to providing the technology solutions, Schneider Electric's highly skilled technicians, who hold vast experience in CSP plant technology, will remain on-site for the commissioning period to ensure a smooth start-up once the plant begins official operations in the near future.
Schneider Electric worked on its first CSP project with Abengoa in 2005. Since then the company's solutions have been selected for different CSP plants technologies constructed by different clients across Europe, the United States, North Africa and the Middle East, with more than 1 800MW and 30 commercial power plants operating with its solutions
"It has become common knowledge that consumption of electricity is growing disproportionately as industry and domestic systems require ever-greater amounts of energy. An advantage for South Africa is that is has an excellent climate, solar irradiance and numerous kilometres of roof space available, lending itself most excellently to renewable energy solutions.
"Schneider Electric is committed to providing energy management and process automation solutions that are tailor made for the country and the CSP business. The company is especially pleased play an active role in building South Africa's green economy through the company's solar solutions, providing green energy with zero carbon emissions," concludes Moreno Valderrama.
Share