NEI to Monitor and Evaluate Solar Thermosyphon and PV Hot Water Systems in a Side-By-Side Experimental Setup at NUST, Namibia

Renewable heating and cooling are the primary focus of the SOLTRAIN+ project in building capacity for solar thermal technology. This emphasis is aligned with the United Nation’s 2030 agenda, which seeks for carbon-neutrality by the year 2030. To address thermal needs on a small-scale, thermosyphon systems and photovoltaic-to-heat systems are frequently used. To scale-up the application of these technologies, and for accelerated achievement of carbon-neutrality, a cost-effective technology must be prioritised in various areas of the world with different meteorological conditions. Supported by the AEE INTEC under the framework of the SOLTRAIN+ project, this experiment intends to establish the technical performance, and the cost-effectiveness of these technologies in Namibia’s environment whilst replicating a small-scale household daily hot water demand.

The system encompasses and will compare:  i) an indirect thermosyphon system with a flat plate collector, ii) an indirect thermosyphon system with evacuated heat pipe collector; and iii) a PV-to-heat system, and will be equipped with a monitoring system that logs all the data about the technical performance of the systems, such as hot water temperature, energy, and hot water flow rate. Primarily, the hot water temperature profiles within the tanks of the three systems will be analysed to establish which system is most efficient, and has the lowest levelised cost of thermal energy (LCOE). The three systems will be installed on a 6 meter shipping container, with the monitoring system, controls, and the storage tank of the PV-to-Heat system installed within the container. The container will be erected at NEI's premises. The three systems will be operated in a controlled manner that replicates hot-water consumption of a small-scale household. Figure 1 illustrates the concept.

Apart from the solar water heating components, a cooling system is incorporated to instantly cool the hot water. This is implemented as a water conservation measure i.e., a closed loop on the heating network is incorporated to eliminate waste of water. A 12-kW heat pump with 4 kW cooling capacity will dissipate heat from a 1,200 litres heat accumulator. The temperature within the heat accumulator is expected to be in a range of 40 °C - 70 °C. Safety devices will be incorporated in case the heat and pressure in the system exceeds the nominal operating temperature and pressure of the systems. The ambient temperature, irradiation data, and hot water temperature in the tanks will also be measured and logged.

To date, E3 Africa (Pty) Ltd has been appointed by the Namibia University of Science and Technology to deliver and assemble all equipment into a complete functioning system. The groundwork has been completed, and the next phase is expected to commence by September 2024. During the next phase, the container will be delivered and erected at the test site. Furthermore, the assembling of the solar water heater systems will begin.

The study will contribute to the University’s Green Vision of 2030, which aspires to contribute towards a future where all energy is consumed from sustainable sources and sustained by a public that understands and values the social, economic, and environmental benefits that green energy provides to communities, nations, and beyond through an integrated green energy creative value chain. In addition, the study will provide evidence-based information to the industry regarding the best systems suitable for the Namibian climatic conditions, considering the economic, environmental, and technical performance of the systems. Similarly, the results of the study will support market confidence in these technologies. A lifecycle cost analysis of these systems will also be carried out, and all results will also be availed to the IEA SHC Task 69.