The biggest solar heating system installed at any hotel in Africa has been installed at the Gaborone Sun Hotel in Botswana.

It is the first hotel in Botswana, as well as the first hotel in the Sun International hotel group, to harness solar power for its hot water requirements.

Johannesburg-based solar power specialist Home Comfort successfully commissioned the fully-fledged solar-power system with a backup diesel boiler. Omnibus Engineering provided the design and subcontracting services.

The installation comprises 176 flat-plate solar panels, each measuring 2m x 1m, effectively creating a 35 m2 solar collector providing an installed capacity of 225 kW, which is the biggest solar-powered system in Botswana. The panels feature a 345kW heat exchanger that is equipped with a drain-back system, to eliminate freezing and high maintenance.

The solar collectors are imported from Chinese company Sunda Solar Energy Technology, which manufactures them under license to Daimler-Benz Aerospace, in Germany, with reference to international standards. Most of the remaining equipment is manufactured in South Africa.

The Gaborone Sun project included a vertical hot-water storage tank with a specially designed stratification system, capable of storing 25 500 litres. The accompanying 233kW backup diesel boiler has been designed to yield a 90% efficiency.

Home Comfort MD Hendrik Roux says that the system will yield 283,5 MW of renewable energy a year, and has been configured to deliver more energy in the cooler months of the year.

This, he notes, amounts to an annual solar savings fraction of 379,21 t of carbon dioxide, 57,321.91 kg of ash, 3,505.46 kg of sulphur dioxide and 1,569.74 kg of nitrogen oxide avoided.

Sun International's Gaborone Sun hotel, casino and conference centre has a virtually uninterrupted fully booked status all year round and must generate in the region of 24,200 litres of hot water a day.

Gaborone Sun GM Lance Rossouw says, that, historically, the venue has relied on coal-fired boilers to generate its hot water requirements. However, he notes, with the boilers rapidly approaching the end of their service lives, it took an executive decision to replace them with the environmentally friendly alternative of solar power.

"Since the installation went live, it's been a real weight off our shoulders not having to worry about coal supply and storage, not to mention the environmental implications of burning coal. An unexpected benefit has also been the new system's efficiency in terms of temperature. Our average hot water temperature has increased from a previous temperature of 45°C, to 70 °C," he says.