1. Solar Thermal Energy Research Group, Department of Mechanical Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa
2. Department of Mechanical Engineering, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa
3. Howden Netherlands, Haaksbergerstraat 67, Hengelo 7554 PA, The Netherlands