2020: Development of the measuring system MONA
The measuring system, which we affectionately call MONA, measures not only the water flow of the unit, several temperatures at different points of the system and the available solar energy, but also all relevant environmental parameters, such as wind, pressure and ambient temperature, which affect the efficiency of the unit. The measuring system performs the measurements automatically and sends the data to the project group via mobile phone and e-mail every night. Thanks to a small solar cell and a battery, the system is completely autonomous. Thus, the measuring system makes it possible to collect and evaluate the data of many plants simultaneously and in high resolution. This will allow a more precise investigation of system failures of individual units in the future and also increase the efficiency of the SoWaDi unit in general.
A prototype of the measuring system MONA was added to the SoWaDi test unit DE01 in Darmstadt in June 2020 as part of a student project. After measuring the system activities over a month, the measuring system was checked thoroughly. By evaluating the measurements, the measuring system and the partly self-developed sensors could be further optimized, so that future MONA measuring systems can be built more cost-efficiently by the group.
2019: Test device DE01
The DE01 test device was used in 2019 to further develop and test the glass construction of the facility. In the past, the high temperatures inside the plant (up to 160°C) had caused damage to the test facilities in Tanzania. In order to avoid expensive damage to the plants, a glass breakage caused by overheating of the plant was traced and analysed in Darmstadt. As a result, the design could be adjusted and the risk of expensive plant damage was reduced.
2018: Prototype of a heat exchanger
The aim of the heat exchanger is to increase the amount of water disinfected by the SoWaDi plant. This is realized by warming the cold water from the input container with the already boiled water without mixing them. Thus the input temperature of the water to be boiled is increased, so that less solar energy is needed to reach the boiling temperature.
After designing several models through theoretical considerations and numerical simulations, the most promising concept was built and then tested in the laboratory. The results suggest a mean increase in output of about 6 liters. The design of the heat exchanger, like the system itself, can be manufactured from simple materials from the sanitary sector and is cost-effective. The heat exchanger’s test on the SoWaDi system is still pending.
2014: Microbiological tests
We developed a test plan to examine the performance of the system. Using time switched pumps and valves the system was run totally automated. We chose different dilutions, up to very dirty water as input for the system, in order to test even higher contaminations than what is expected for a normal day to day usage of the system. Over a period of multiple months data about different parameters was collected multiple times a day, among others the amount of water, concentration of germs, turbidity and pH-value.
The results of these tests are summarized at technical data (6.2 and 6.3).
2013: Thermal examination
The prototype was run with a closed water cycle, where the output water was collected and used to refill the input tank. The throughput was measured with a pressure sensor.
We also collected data about the solar radiation, as well as temperatures at different points of the water cycle and the absorber. Over the following weeks and months we used this data to validate our thermodynamic model and the associated calculations and improve the construction. Parts of the data can be found in the scientific publication. The focus of the operation of the prototype was laid on potential weaknesses of the system and insights on the aging of the used materials and necessary maintenance.
In the following summer we used the prototype to test alternative construction techniques and materials. We were able to test alternatives for the building process of the absorber and the cover and were able to evaluate the experience of the prototype construction regarding the manufacturing techniques.