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Delta 50 kVA String Inverters in 4.5 MW Namibian PV Plant

By Nicky Callinan on May 27th, 2015

Delta has been selected to supply its RPI M50A string inverters for the construction of Namibia’s first and largest utility-scale solar PV power plant, totalling 4.5 MW across 16 hectares of arid land, located two hours northwest of the city of Windhoek.

The project began after the signing of the first-ever Power Purchase Agreement (PPA) between NamPower, Namibia’s national power utility, and InnoSun Energy Holdings, a subsidiary of renowned French wind developer, InnoVent.

InnoSun selected the Delta RPI M50A three-phase transformerless models with 50 kVA output because of their reliability and low maintenance. Due to their robust design, the RPI series inverters are an ideal choice for the rugged environment of Namibia.

The 4.5 MW Omburu PV plant is expected to generate a total of 13,500 MW hours of clean and reliable electricity annually which will cover a large percentage of the energy needs of the region, help maintain stable electricity prices, and avoid power shortages. Furthermore, the PV plant is estimated to help save over 8,500 tons of CO2 per year, the equivalent CO2 produced annually by 1,800 passenger vehicles.

System Structure:

InnoSun chose TSMC CIGS (copper, indium, gallium, selenium) thin-film modules for the plant which were mounted on a horizontal tracking system. The 1-axis tracking system adjusts the solar module position in relationship to the position of the sun over the course of the day thereby maximizing energy output, and increasing output by up to 25% when compared to a fixed-tilt system. A total of 33,418 thin-film solar modules were installed in the system as well as 100 Delta string inverters, providing a corresponding PV power of 4.5 MW.

The use of string inverters were preferred over central inverters because the former need less cables and components and can be installed without special housing in protected areas. As a result the investment costs can be reduced. Additionally, the string inverter creates a stable production level. The PV plant can continue to run with very low production losses when one string inverter fails in comparison to much larger losses when a central inverter stops functioning. Because the Delta RPI M50A string inverters require very little maintenance over the years, no maintenance contract is needed, which significantly lowers the operating costs.

With its inverters, Delta has made an important contribution to the success of the first-ever utility-scale PV project in Namibia and look forward to being part of the growing PV market in Africa. Delta plans to continue to work with InnoSun to provide its high efficiency string inverters for even more large-scale PV projects in this region.

Site construction commenced in August 2014 and took six months to complete.