Botswana’s first solar thermal system subsidized by SOLTRAIN was commissioned in February this year. SOLTRAIN’s partner in Botswana, the Centre for Clean Energy Research, University of Botswana, actively guided and supported the project through the phases from inception to installation and commissioning. The beneficiary of the project is Mara-u-Pula Secondary School, which is a premium Senior Secondary School located in the proximity of Gaborone Central Business District.
With a price tag of close to 18,000 Euros, the project timeline took roughly three months from the time of submission of application for the SOLTRAIN subsidy to installation and commissioning, and the design and installation was done by Botswana-based company, So Solar (Pty) Ltd.
Technical Description of the systems
The installation consists of two pumped solar thermal water heating systems. The first is for the boy’s boarding house which was a refurbishment. This system was sized to provide hot water for 65 students and consists of a 2000 litre tank with a heat exchanger and an electric heater as backup. It was designed to operate with a 90% solar fraction and is powered by 16 flat plate collectors in combination of series and parallel. Due to roof orientation, the collectors face north west and consequently, a modest addition to the collector area was needed to compensate for the orientation away from north. The pumped system supplies 1800 litres per day on average.
The second system is installed at the girl’s boarding house and is designed to meet water demand for 65 girls. It consists of a hot water tank of 2000 litres and is powered by 12 flat plate collectors, also connected in a parallel and series arrangement. The collectors face north for optimal solar gain.
To comply with SOLTRAIN requirements, the systems are equipped with remote monitoring capabilities to enable their performance to be tracked on a continuous basis. A number of parametersarecapturedandrecorded,including collector inlet and outlet temperatures, storage tank heat exchanger temperatures across the primary and secondary loops, mass flow rates for the heat transfer media, water glycol mixture for the input and output of the collector circuit and the mass flow rates for the heat exchanger system. More importantly, the solar radiation resource available at the site is monitored continuously to enable the yield, efficiency and economic performance to be evaluated over a desired time-horizon.
Site Visit and Quality Assurance Training
The completion and commissioning of the Mara-u-pula system coincided with two important SOLTRAIN events in Botswana, namely, SOLTRAIN’s annual two-day conference held in early February, and SOLTRAIN’s Quality Inspectors: Solar Water Heating training course which took place after the conference. Conference delegates were taken on a site visit to the installation where they experienced the contribution that SOLTRAIN is making in practice towards promoting and developing capacity in the field of solar thermal systems in Botswana.