Private hospital group Netcare has made its third and largest investment in renewable energy at the Union Hospital in Gauteng, where a R1,6-million, 18 500-l solar water heating system was commissioned early in November.

Considering the future electricity tariff increases proposed, Netcare national technical manager Peter Schilder, expects a payback period of three years, which came down from an initial estimate of about four years. The return on investment would then continue, as the solar water heating installation has a life expectancy of about 20 years, with savings over the life cycle of up to R24-million.

"We did an extensive survey before we did the installation. We probably looked at between 12 and 15 suppliers. It took us almost a year to decide on the current supplier, and it was primarily based on a return on investment. I think it is important when one engages in environmental diversification of energy, that it has got to make financial sense," adds Schilder.

"To strive for sustainability at all costs is perhaps not the best way to do things," says Schilder, adding that functionality is imperative, followed by financial matters, and the quality of installation and materials are also important while considering environmental benefits.

Eskom, through its demand-side management programme, also wants to incentivise commercial solar water heating installations and the rebate expected from the utility is about R210 000.

Maintenance costs for the system are expected to be about R3 000 a year, taking inflation into account.

The project was awarded to Johannesburg-based Voltas Technologies in June, and installation started in September 2009.

"The technology is known - it is the application of the technology in South Africa that is new. Choosing the right technology for a specific application is imperative," explains Voltas Technologies director Cristian Cernat.

Taking into account the limitations of the hospital roof, the potential for future expansion, and other equipment needed on the roof, as well as the required orientation and inclination of the collectors, the most appropriate application was chosen for the specific site.

The structural integrity of the building also had to be considered to ensure that the roof could take the weight of the collectors, and certain structural steel frames were required for the installation.

The intricacy of a hospital installation makes it very different to installing a solar water heating system in a residential home, and co-ordination is very important. Contractors responsible for the installation of the 92 evacuated tube collectors, and all the piping requirements, had to ensure minimal disruption to the hospital when the switchover took place.

Installation contractor JSM Pipe projects MD Joaquin Nkomo explains that all the collectors on the roof, as well as the pump stations, and connections from the roof to the tanks had to be set up beforehand, and switchover to the solar system had to be done in six hours once everything was ready.

Skills capacity is often cited as a major challenge facing the solar water heater industry, however, Netcare Gauteng south-west regional manager Khanchane Leteba affirms that "we do have the capacity in South Africa".

"The Netcare technical teams, which are based at Union, coordinated together with the contractor, who has the expertise. We worked harmoniously and made sure that that installation was done without hamper or any damage, giving the patients top priority," Leteba adds.

The collectors are imported, and Cernat maintains that it would be a great thing if the solar water heating market in South Africa opened up to the point where investment in an evacuated tube collector manufacturing facility was justified.

The Himin U-pipe evacuated tube collectors were chosen because of the 97% light absorption efficiency, and the 90,3% thermal efficiency. "This is a very high-efficiency panel," says Cernat, who explains that the evacuated tubes absorb ultraviolet radiation, and a broader spectrum of light.

"It is an optimisation exercise. Especially in existing facilities you can't always design the ideal system. You have to work with certain givens and find a balance between the size of the plant and the financial implications on the project," explains Voltas Technologies operations manager Frank Major.

The final design solution came after the hospital's baseline water consumption was measured, placed in context with seasonal requirements, and put through a simulation programme, establishing weekly, daily and even hourly water usage. The electricity used to heat water was also monitored.

The real savings will now be measured and verified against the baseline. These measurements should show that the water usage stays the same, but the electricity usage drops.

The plant will operate at a solar fraction of about 86%, which takes into account cloudy days, and means that, essentially, the hospital should see a saving in water heating costs of about 86%.

The two electronic logging systems, monitoring the operation for the two separate buildings, the North wing and the South wing of the hospital, offer Netcare the opportunity to track savings continuously.