SALT doubles grid-tied solar system, supported by year-long test

22nd February 2021 By: Schalk Burger - Creamer Media Senior Contributing Editor

The Southern African Large Telescope (SALT), in the Northern Cape, has added a new 53 kW solar installation to its grid-tied 40 kVA solar rooftop system.

This follows after a system installed on the workshops of the South African Astronomical Observatory (SAAO) provided one year of operational data that convinced the SALT board that a similar-sized system would work on the SALT stores roof.

South African sustainable energy and water solutions company SEM Solutions installed a grid-tied solar photovoltaic (PV) plant at the SAAO workshops in 2019. The SAAO has a dedicated research and observation station with several telescopes (including SALT) outside the Karoo town of Sutherland. The first installation provided 53 kW and served as a supplementary power supply to the existing Eskom supply.

In late 2020, SEM Solutions installed another 53 kW system on the SALT stores roof that also feeds the entire site.

“The observatory site has a good solar resource, as it has an altitude of 1 780 m with low rainfall and a relatively cool climate, all of which contributed to excellent PV operations,” says SALT electronics engineer Keith Browne.

Although both installations have the same installed capacity, the first installation comprised 156 PV modules of 340 W each, while the second installation comprised 128 PV modules of 415 W each, says SEM Solutions operations manager Menno Sulsters.

“This demonstrates the improved efficiency of the PV modules over just a year, going from a maximum of 340 W coming out of one PV module to 415 W coming out of the same size PV module. Both installations have the same Huawei 40 kW inverter installed and are connected to the same online monitoring portal. The installations are running exceptionally well and are continuing to show a positive return on investment as operations continue despite load-shedding and energy consumption costs decrease.”

The SAAO's overall demand is around 150 kVA on average so there is still room to grow the contribution from renewable energy. With an annual saving of around R312 000 at the current Eskom rates, it is a viable long-term solution, says Browne.

The SAAO is on the Ruralflex tariff structure from Eskom, and the cost of electricity varies during the day and in the summer and winter season.

“Electricity use is highest in the winter when the tariffs are highest and solar power the lowest. The SAAO is currently considering wind power to compensate for the high winter electricity consumption by residences on-site for heating in winter,” he says.

SALT is funded by a consortium of international partners from South Africa, Poland, the US, the UK and India, and the telescope attracts astronomers from around the world to the Karoo.

The US National Aeronautics and Space Administration (Nasa) became interested in placing a telescope on the SALT site as part of their Asteroid Terrestrial-impact Last Alert System (ATLAS) project, which focuses on identifying and locating asteroids that could potentially hit Earth.

However, owing to South Africa’s ongoing load-shedding, Nasa had concerns about the availability of electricity. To alleviate the site’s dependence on Eskom, funds to develop a supplementary power plant, relying on batteries and solar power were made available and the move towards sustainable energy solutions began.

“The backup generators at the site were also upgraded, removing the need for an independent power supply for Nasa’s ATLAS telescope. It was then possible to redirect funds to install a 40 kVA grid-tied system that would benefit the entire site," says Browne.

While the SAAO and SALT operations are of significant international importance, they are also costly to run and maintain. In 2011, the SAAO started an investigation into the feasibility of using solar power to offset the cost of electricity. Initially, the cost of installing solar power was prohibitive and not implemented as it required capital investment, which, at the time, was required for the primary focus of collecting data for astronomy sciences.

“As the globe looks towards using renewable energy sources, it is very satisfying that the largest single optical telescope in the Southern Hemisphere is already on that path. Mankind has always loved to look towards the stars, and in Sutherland, that star watching is powered by one,” he concludes.