Video about our test facilities

Our two test systems DE02 and DE03, which were built in April by our SoWaDi project group on the experimental field of the TU Darmstadt, have recently been running. SoWaDi stands for solar water disinfection: the system we developed boils water with the help of solar energy and thus reliably removes microbiological impurities. The parallel operation of the two new test plants allows us to evaluate design changes we will make to one of the two plants and to analyse its long-term performance.

The basic supply of safe water is still not assured in many parts of the world. Especially in rural regions in the global south, many people still depend on water sources that are contaminated with health-threatening pathogens and fall ill as a result. According to the WHO, an estimated 829,000 people die each year from diarrhoeal diseases related to unsafe water and inadequate sanitation.

Unfortunately, the video is currently only available in German.

SoWaDi construction weekend: DE02 and DE03 are ready for use

On the weekend of 17 & 18 April, it was time for us to get away from our desks and get to work with the jigsaw! Our goal for the weekend was to build two new facilities on our test field at the Lichtwiese in Darmstadt.

The planning

Already at the beginning of the year, we all knew that this build-up would be marked by the Corona pandemic.  Towards the end of March, the thematic groups of manual, construction and performance sat down and started planning. In addition to organising the purchasing and planning the schedule, the main focus was on developing a hygiene concept so that the set-up could take place despite the Corona pandemic.

The set-up

At 9:30 a.m. on Saturday, the set-up weekend kicked off. Beforehand, all participants did a Corona quick test, as it was planned in the hygiene concept. All tests were negative and the construction could begin. The group was divided into five teams, which were to stay together for the weekend in order to reduce the number of contacts within the group.

After the initial finding phase of the teams – many participants had never seen each other “in real life” before due to the pandemic – things got off to a productive start. By the time we had lunch together, the tools for teams 1 & 2 were ready, the wood for team 3 had been cut and team 4 had painted the first layer. Towards evening, the pipes were bent, a large part of the sheet metal for the absorbers was beaded, the two wooden boxes were assembled and the steel rack was painted.

On Sunday, the motivated team continued at 10 am. Everyone tested themselves on the second day as well – better safe than sorry. After the remaining metal sheets were bent, the assembly of the absorbers could begin. The metal sheets were connected to the pipes and painted black. Meanwhile, the wooden boxes were lined with mineral wool. After that, the wooden boxes only had to be integrated into the racks, the absorbers inserted, the glass panes carefully placed and everything made watertight. At about 6 p.m. we were finished and the result was definitely something to be proud of!

The result

The aim is to evaluate design changes with the two new installations. For this purpose, test series are planned for the summer to quantify the effects of different insulation materials, other pipe bends, etc. It is therefore important that both absorber boxes are identical. This is now the case with DE02 & DE03. The rack of DE02 was welded from metal, as our plants in Tanzania are on steel racks and this variant should also be illustrated in the manual. In summer, both systems will be “refuelled” via a central water supply, so that the test operation can take place without us on site. Our MONA system will record the data and send it to us via mobile radio.

As important as the set-up was for the research operation in the summer, it showed us above all that our team continues to work productively even during the pandemic.

We are excited about the commissioning of both facilities in the coming weeks and long for the next group event in “real life”!

Mr. Mrema’s experience with a SoWaDi system after one year of use

In 2020, a team from our project group travelled to Tanzania to build new SoWaDi plants together with our project partner Kilimanjaro Childlight Foundation (KCF) and future users.  One year after the construction of the devices, Sam, project manager at KCF, talked to Leonard Makala Mrema about his experiences with the SoWaDi plant and the project so far. Mr. Mrema is a teacher at Kidia Primary School, where a SoWaDi plant has been in operation since last year.

The interview was edited for this blog entry.

Sam: What did you think when you first heard about the SoWaDi plant? And what were your expectations of the plant and the project?

Mr. Mrema: The first thought in my head was CLEAN WATER. I expected the device to provide clean and safe water that will be used by the students and teachers. My expectations on the project were to be able to gain knowledge and construct the device on my own.

Sam: What tasks do you take on in the project and what was your motivation to  become part of it?

Mr. Mrema: The main motivation for me to part of SoWaDi project is to be able to provide clean water for the children. That‘s why I collect data and send it to EWB. I also maintain the device making sure it is working properly everyday.

In order to collect information about the lifespan and long-term performance of the plants, each plant is looked after by a person in charge who passes on data to the project group.  Mr. Mrema has been looking after TZ03 for a year now.

Sam: Can you describe an ordinary day with the plant? What exactly has to be done by whom?

Mr. Mrema: In the morning I check the device and inspect it if there any damages or leakages. I then instruct the students to fill in the water in the input container. Later on in the afternoon, I check the device to see how it’s going on and extract water from it (in a sunny day). In the evening, I cover up the device and head home. In summary, my main work is supervision of the device, data collection and sending it to EWB. The students (specifically chosen) fill in the water when it’s empty in the containers.

Sam: And what is the treated water then used for?

Mr. Mrema: The students and teachers use the water and mainly it’s for drinking.

Sam: You say that you send EWB data from the plant. How does the contact work and what do you talk about? 

Mr. Mrema: I am in contact with Julius and Max from the project group in Darmstadt. We normally communicate about general issues about the device, e.g. if it’s working properly or if there are any challenges on the device.

Sam: Now the plant has been at Kidia Primary School for almost a year. What is your opinion of the project after this long time? Have all your expectations been fulfilled or do you still see room for improvement?

Mr. Mrema: No, my expectations were not fully fulfilled. Nevertheless, I think that the project  as a whole is successful. The plant has been beneficial to us especially providing safe water for the children and reducing stomach ache problems. Still, there are also some things that could be improved: If the device could produce more output to be able to meet the need of the entire school, it would be good. In addition, problems sometimes occur when cleaning the containers because some of the cleaning water runs back into the main system and then mixes with the input water. A solution for this would be very good.

Sam: Have other people also become aware of the plant? And if so, what are their reactions?

Mr. Mrema: Yes I have spoken to a number of people about the project. They really wish to have the device at their homesteads too.

We thank Mr. Mrema and Sam for the interesting interview and the many insights!

Virtual SoWaDi Weekend

We used the last weekend in March to meet for a SoWaDi project weekend and work together on current work packages of the thematic groups, but also to make progress on tasks for which there is often no time in the daily project routine. For example, we finally found time to sift through and re-sort the archive in our cloud, where documents have accumulated since we started the project in 2010. Now it is integrated in our new knowledge management concept. We also looked again at the minimum technical and economic requirements of various stakeholders for the SoWaDi system, in order to be able to evaluate further technical developments and possible distribution strategies on the basis of this. Unfortunately, due to the still tense COVID19 situation, our meeting had to take place virtually via Zoom. But by now, we are all experienced in this and were able to work productively thanks to break-out rooms, screensharing & Co. And not only that – a virtual games evening on Saturday for team building with SoWaDi quizzes and online games was of course not to be missed! So not only did we take an important step forward in our project work, but we also had a lot of fun together.

This is how we look into the new year

This blog entry is about a review of the year 2020 and our expectations for the new year 2021. The past year will certainly be remembered by most people mainly because of the serious consequences of the Corona pandemic. We, too, had to get used to the new conditions created by the pandemic and adapt our way of working accordingly. Although many processes were slowed down or even hindered as a result, in retrospect we can still be very satisfied with what we achieved in 2020.

While in 2019, we mainly used our time to prepare for the departure and the construction of a plant in Germany, we were able to start 2020 directly with an important milestone of the current project phase, the departure of our volunteers to Tanzania in January and February 2020. Through this departure, we were able to build a solid foundation for the later course and success of the SoWaDi project.

First of all, we were able to carry out maintenance work on two of our solar water disinfection systems, which were built in Mwanga in 2017 together with our partner Kilimanjaro Childlight Foundation. In addition to the maintenance work, technical improvements of the two plants could be realized there. In the neighboring town of Kidia, Old-Moshi district, we were also able to build four new plants, so that Tanzania now has a total of six of our test plants.

Back from the trip to Tanzania, we are in weekly exchange with the beneficiaries to get data on the water output of the plants. Also, we get to know if there are problems with the plants and can give advice. To check the functioning of the plants, our project partner carries out water tests at regular intervals.

It is very important for our current test phase to obtain reliable data on the plants. To expand the data situation regarding the performance of the plants, students of the TU Darmstadt developed a self-sufficient measuring system in cooperation with our project team from May to August of last year. This measurement system was affectionately named MONA (Monitoring Offgrid Node for Assessment of SoWaDi Performance). A detailed blog entry about this measurement system can be found here. It is definitely worth reading!

In August 2020, our first construction manual was published. In order to achieve a worldwide availability of the plants, the material purchase and construction should be possible with this construction manual alone. The first version of the instructions was already created during a departure journey in 2017. Since then, however, we have been able to gain important experience regarding the construction by building the plant several times (twice during the departure in 2017, in summer 2018 and 2019, and four times during the 2020 outbound trip) and have been able to improve the instructions from 2017 crucially. By the way, the construction manualcan be freely downloaded here and is definitely worth a look!

In the third phase of the project, the current test phase, the main goal is to collect as much data as possible on the use, quality, and durability of the plant, so that in the long term, technical optimizations and efficiency improvements can be made. Only after these improvements, the plant can be distributed beyond Tanzania. With this in mind, the departure in 2020, the development of the MONA measurement system, and the publication of our construction manual were very important steps for the success of the SoWaDi’s project. Thus, as a project group, we are extremely satisfied with the results of these three events.

For the coming year 2021, we naturally want to build on the project success of the past year and accordingly also have certain goals and some expectations.

In order to obtain a broad and diversified database, it would be desirable to set up even more plants at different locations. For this purpose, we want to cooperate with other Engineers without Borders projects to build and test SoWaDi plants in their project regions. Our construction manual will also be very helpful for this purpose.

Another point we want to follow up on are the MONA boards. On the one hand, we want to use them to analyze the performance of the plants in Tanzania in more detail and, on the other hand, to equip any new plants that may be built as part of an Engineers Without Borders cooperation directly with our measuring system.

Last but not least, we also want to build a new, second test plant in Darmstadt in 2021. This will allow constructive changes to be tested directly on one of the plants and subsequently, the results can be compared with the unchanged plant. The aim is to evaluate the changes in terms of performance and thus to be able to work out concrete improvements.

Test plant DE01 in winter break

Our test plant DE01 is located on the experimental field of the TU Darmstadt. After successfully developing and testing a measuring system here in summer 2020, which will provide us with important data on the performance of the plant in the coming summers, the plant has now been sent into winter break: Different to our target countries such as Tanzania, the sun only shines for a few hours in winter in Germany, so that the DE01 plant cannot produce output over the winter and thus cannot provide usable measurement data. In order to protect the plant from sub-zero temperatures, ice, snow and wind, and related wear and tear during the winter months, it has now been made winter-proof by a small team.

For this purpose, the water was completely removed from the system, the sensitive parts of the measuring system were dismantled and the plant was covered to protect it from moisture. In this small video, the SoWaDi team introduces itself as it works to prepare the facility for winter. Unfortunately, the video is only available in German.

However, the fact that our plant is hibernating does not mean that our project group is also sleeping. In the summer, the new measurement system has already been used to collect a lot of data, which is now being evaluated by our performance group in order to make SoWaDi even more efficient in the future. In addition, we are currently working on new cooperations to spread our plant so that further test facilities can be built in Tanzania or other target countries in the coming year. Another test facility is also to be built in Darmstadt next spring. The construction of the second plant in Germany will be able to test further technical developments in real operation. For this purpose, technical changes are made to one of the two plants, and the performance is compared simultaneously with the unchanged reference system. This set-up is already being planned and prepared by our project group.

Developement of a measuring system for efficiency determination

From May to August 2020 the students Steffen Bißwanger, Leon Dungs, Sara Konrad, Nikola Milenkovski and Alexander Zinn  carried out a project as part of their studies at the TU Darmstadt in cooperation with our project SoWaDi. The goal was the development of a self-sufficient measurement system, which allows the determination of SoWaDi units efficiencies in the field. This is to be achieved by automated data collection of solar radiation, water output and environmental conditions.

In the following you can read some recordings from the students’ laboratory book. There they recorded their progress and described how they overcame the challenges they faced during the project.

Phase 1: Selection of components

09.04.2020 09:45

Today we firstly get to know each other, online of course, and get accustomed to the Solar Thermal Water Disinfection Unit we will work with during the project. Two of our team members already know the unit well. The rest of us are just getting to know it. In order to develop a suitable measuring system, it is important to have a good understanding of the function of the unit and the conditions in which it is used.

08.05.2020 15:15

Some time ago, we were able to agree on which quantities we wanted to measure. The important question now is: How? Today we discuss our latest ideas about which low-cost sensors and designs will give us the best results. A special challenge is to measure the amount of water coming out of the unit. In the past, several attempts have been made, which failed due to different reasons. Temperature variations from day to night have led to unreliable results of load cells and a sensor with moving parts blocked when it was used in wind and weather. But we have a new idea: a cut-off glass bottle with a small hole in the lid can be turned upside down to serve as a collecting container and accumulation device for the minutely water flushes from the unit. We then measure the time it takes for the glass bottle to empty again after a flush.

23.05.2020 17:18

We are finally ready: After 5 hours of discussion we have selected suitable components for all sensors, the computing units of the system, the data transmission and the power supply. Now all we can do is wait until the order arrives and hope that everything fits together.

31.05.2020 13:15

We just got the message that the first package has arrived. Now the real work can begin.

Phase 2: Programming and building the measuring system

31.05.2020 14:45

Except for one team member, none of us has worked with the microcontrollers we want to use for the project yet: Arduinos.

After we have set up the programming interface on the computer, we can finally load the first program onto the Arduino.

31.05.2020 14:46

The Arduino starts blinking. Hurray! Let’s see if it will be as easy to connect and read out the sensors as well.

02.06.2020 12:37

We were able to get the SD card reader, the current meters to measure the sun intensity and the simple thermometers working without any problems. The somewhat more complicated thermometers for the higher temperatures, however, only show strange values so far. Where they come from, we cannot explain. One thermometer shows us 65°C and another 9°C, both temperatures are definitely not correct.

02.06.2020 19:36

We just found a way to correct the strange values. One parameter in the calculation formula is a comparative voltage. While measuring this voltage at the sensors we noticed that it is different for each sensor individually. Now that we have incorporated this into the software, all thermometers show plausible values.

13.06.2020 09:42

We are now already in the middle of June, the weather offers optimal conditions to test the new measuring system. It is therefore about time to finally attach the measuring system to the unit. Therefore we are working at maximum effort to complete the circuit board for the measuring system. We solder all connections by hand. Hopefully our plan will work out. Also, the data transfer via the cellular module still doesn’t work. After we have ordered a better module in the meantime, at least we could get a connection to the mobile network, we unfortunately still haven’t managed to send the data automatically. Slowly time is running out. If we don’t manage to solve this, the whole project could fail.

14.06.2020 21:06

After two days of hard work the board is soldered. The measuring system can finally be installed in itscase, where it will be protected from rain when installed on the unit. We also made important progress with the sending of the data. The microcontrollers are now slowly reaching the limits of their computing capacity, further changes are becoming more and more difficult to implement. Fortunately, only a few minor software problems need to be fixed now, and then the measurements can start soon.

Phase 3: Attaching the measurement system to the unit

20.06.2020 09:16

The time has come: Today we can finally install the measuring system. It has been running continuously since yesterday and is ready for use.

20.06.2020 22:03

We have been waiting for the first data to arrive for 3 minutes now. Now comes the moment of truth. If everything goes smoothly today, we are confident that the measurement system will continue to work for the next three months until too little light is available in October.

20.06.2020 22:04

The first data have reached us. We are relived. We have done it and deserve a break for a while. As soon as we have enough data, we can start evaluating it and start to write a full report.


With the measurements over a period of 30 days, the team has succeeded in finding out which sensors are relevant and suitable for the assesment of efficiency. So that in the future it will be possible to build a low-cost measurement system that can perform all important measurements. Almost the entire team will continue to develop the measurement system on a voluntary basis at Engineers Without Borders in Darmstadt. The new measurement system is called MONA (Monitoring Offgrid Node for Assessment of SoWaDi Performance). In the future MONA will help to collect long-term data in Tanzania and to further develop the SoWaDi unit in Darmstadt. In contrast to her mother, MONA is a little smaller and more compact, and also not as transparent, just perfectly equipped for a world tour.

Video of our presentation “Introduction to SoWaDi”

Hello everybody!

As already announced in the previous blog entry, we had the possibility to give an online talk for SoWaDi supporters on 29.10.2020.

The presentation, which we are now able to provide in form of a video, gives an overview of the idea and the history of our research project, as well as of our project phase in Tanzania in spring 2020 and an outlook into the future. It was held by three members of the project group: Julius Breuer, Sara Konrad and Jan Erik Schliephake. Philipp Erdmann from the Darmstadt regional group was the moderator.

We apologize that the presentation is only available in German. Nevertheless, we would like to make it available here as well. The talk lasts about 30 minutes. Afterwards you can listen to the entire Q&A session of about 20 minutes. Unfortunately, the first 20 seconds of the presentation are missing due to technical difficulties. This is a great pity, but does not diminish the content of the lecture in any way! 🙂

We would like to thank all those who took part and made for an exciting Q&A session with their questions!

If you have any further questions about the lecture or the project, please contact us here:

[1] Icons made by Good Ware from
[2] Icons made by srip from
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Invitation to our SoWaDi online event

Access to safe water has been recognized worldwide as a human right since 2010. However, contaminated water continues to be a major problem for the health of the local population in many parts of the world. Therefore we develop SoWaDi.

SoWaDi stands for Solar Water Disinfection: The solar water disinfection systems developed and researched in the project use solar energy to improve the water quality. Since 2010 we have been developing technical solutions together with local partners in rural areas of Tanzania to improve the water situation for families and at schools.

The aim of our project is to ensure that as many people as possible have access to germ-free water, because clean water protects against diseases such as typhoid fever and cholera. To achieve this, a construction manual is available free of charge. This enables everyone to build and install the system themselves using locally available, inexpensive materials.

The work, which continues despite the corona pandemic, is carried out in close cooperation with our local project partner Kilimanjaro Childlight Foundation (KCF). In Tanzania, together with local school groups and families, six of the systems have already been installed. The local supervisors of the facilities regularly collect and evaluate the data, which is then used to continuously optimize the facilities. In this way, we want to identify possible weaknesses, improve effectiveness and contribute to a long-term and sustainable solution for rural water supply. In July, a team from KCF was able to visit the plants and ensure that they were back in operation in time for the beginning of the dry season.

If you would like to know more about how our solar water disinfection system works, how we continue the research and development work together with KCF in Tanzania despite Corona, or if you have any further questions, please take part in our online event in German language “SoWaDi introduces itself: Solar energy for clean water” on Thursday, 29.10. at 19:00! To get the link to the event, please write an E-Mail to: