Enabling Clean and Sustainable Water through Smart UV/LED Disinfection and Solar Energy Utilization
Access to clean drinking water is both a human right and part of the Sustainable Development Goals of the United Nations. Safe and clean drinking water is vital to human life but access to drinkable water is not a standard in many countries around the world. Especially in remote areas like rural zones in Africa, people often only have access to water sources such as self-constructed wells or boreholes which are contaminated by bacteria and germs. In Africa, one in three citizens are affected by water scarcity and about 400 million people do not have access to drinking water.
The LEDSOL project is funded under the LEAP-RE programme (The Long-term Europe-Africa Partnership on Renewable Energy), which aims to increase the use of renewable energy via a well-balanced set of research, demonstration, and technology transfer projects in both continents.
The LEDSOL project is fostering renewable energy to provide clean and safe drinking water based on UV/LED disinfection augmented with classical decontamination and powered by lightweight flexible solar cells. The LEDSOL system is designed to be packed in a self-powered wearable backpack with a positioning engine, which offers an easy to use and affordable technology to local population who is off the grid.
A multidisciplinary consortium comprising partners from Algeria, Togo, Romania, Germany and Finland is gathering the needed expertise for the project implementation and for reaching the objectives set up in the proposal.
We have explored the experiments performed and described in litarture for a wide variety of germs in order to establish the functional requirements of the UV/LED module of the LEDSOL system. Based on our findings, we have identified various issues that may arise in the design or operation of the system. We have designed solutions to the identified problems and have compiled a list of components for the future LEDSOL prototype which were then designed in Activity 1.3.
We have analysed in this activity the existing solutions on the market which we can use for the develop of the UV/LED disinfection module. Specifications for both individual LEDs from various manufacturers and integrated LED modules were analysed. These were divided into 3 categories: UV-A, UV-B and UV-C. Based on the performance and price analysis, we have defined the components for the development of the UV disinfection module.
Based on the results obtained as part of the Activities 1.1 and 1.2, we have developed a first model of the LEDSOL, namely the UV/LED disinfection module. We have designed the components using VariCAD, a computer program for 3D/2D CAD and mechanical engineering. We are presenting here several views of the components such as the main body of the module, the caps with quartz windows, the water circulation pipes, the PCBs for the electronics, etc.
We have analysed several water disinfection, filtration and purification systems availableon the market. Their most important specifications are presented, focusing on size and capacity, flow rate, price, water disinfection and filtration methods and power supply (solar/vehicle/plug-in). Finally, a brief comparison with the LEDSOL system is made in order to identify the advantages of the LEDSOL solution for the particular application area targeted in the project.
The project and the results achieved during the first implementation phase were presented as follows: a conference paper accompanied by a presentation at the ICERI 2022 conference; the project website; Linkedin and Twitter pages; the project presentation at the LEAP-RE 2022 Stakeholder Forum held in Preotria; the annual seminar of the Finnish Academy's DEVELOP programme held on 27 October in Helsinki.
Different types of solar panels have been identified that can be considered for powering the LEDSOL system. The main characteristics are that they should be light and flexible. Solar panels were chosen because of their: high efficiency (for those made of monocrystalline material), reliability, reduction of shading effect by parallel arrangement of the constituent sub-panels, weather resistance. Portability is enhanced by their simple packaging and reasonable weight. When travelling, they can be easily and efficiently placed on a backpack. In order to optimise solar panels for the LEDSOL system, we should take into account that their performance depends on several factors, including geographical location and weather conditions. Furthermore, the LEDSOL system is not static and is conditioned by constantly changing environmental variables. Also, because the system has to be portable, the overall weight and size of the components (battery, charge controller and photovoltaic module) are important parameters to consider, along with user safety.
In order to perform the UV disinfection treatment, initially the water must be filtered from impurities so that its turbidity is as low as possible. For this purpose, mechanical filters will be used to remove solid particles and impurities. The choice for these filters depends on the quality of the filtration and the weight of the filters. Two pumps are needed to pump the water: one will pump water from the surface source into the backpack and the second will pump water through the backpack circuit. The operating parameters of the two pumps are dictated by the performance we want the system to achieve. In addition, for the laboratory prototype, it is necessary to use pumps that allow repeated disinfection of its components using aggressive chemical reagents. For this purpose, peristaltic pumps were selected that avoid contamination of the pumped liquids by contact with the mechanical parts of the pump. These are self-priming positive displacement pumps, which can safely run dry.
In order to elaborate the economic documentation, the methods that can be used have been identified and analyzed. SWOT analysis is a method used to project an overview of the company that wants to exploit the results of the project. It works as an X-ray of the company or business idea and assesses at the same time the internal and external influencing factors of an organization, as well as its position on the market or in relation to other competitors with the aim of highlighting the strengths and weaknesses of a company in relation to the opportunities and threats existing at a given time on the market. Alternatively, the initial analysis can be based on canvas models. The Business Model Canvas (BMC) is one of the main tools used to assess the viability of an idea. It is a quick and effective way of summarizing the main ideas of a business case and visualizing the assumptions and hypotheses made. The Lean Canvas Model (MLC) is derived from the BMC and uses a 9-block concept. The Agile methodology can be used to describe to the target users how the final product will be used and what problem it will solve. Agile has a high level of user involvement and includes frequent reviews.
Three types of experiments were carried out: (i) experiments to measure the power distribution of the UV-C and UV-A emitting LEDs as a function of the current injected into each; (ii) experiments to measure the radiation dose as a function of the current through the UV-C LEDs; (iii) experiments to measure the flow rate of water pumped by the peristaltic pump. (i) The power emitted by the UV-A and UV-C LEDs was measured using a Thorlabs S405C power meter with thermal sensor. Measurements showed that the quartz window positioned above the LEDs did not significantly attenuate either the 275 nm or 365 nm radiation. Measurements made with a Teflon tube of different thicknesses (10 mm and 2 mm) did not show a dramatic increase in intensity. (ii) Measurements of the dose obtained at different points along the height of the Teflon tube were made. UVC-LED cards were used for this purpose. These provide a simple and reliable way to validate the UV-C doses delivered by devices producing germicidal radiation in the 260-280 nm range. Small pieces cut from the UVC-LED cards were placed along the Teflon tube at three distances from the UV-C LEDs (1, 10 and 24 cm, respectively) and irradiation was carried out for time durations of 2, 10 and 100 s The current through the UV-C LEDs was kept constant at a value of 350 mA. (iii) The time required to transfer 2 l of water through the peristaltic pump was measured. The flow rate thus determined was 1 l/min for a supply voltage of 24 V and 1.2 l/min for 25 V. The pump head speed under load was determined both visually and by analysis with a Rohde & Schwarz RTE 1054, 500 MHz oscilloscope. The signal on the oscilloscope was obtained using a 1 Ω resistor placed in series with the peristaltic pump. The speed was estimated at 120 rpm.
Dissemination of the project was done by engaging in various activities that contribute to increasing the visibility of the project, the results of the option and their impact. These include events organised by related authorities in the consortium countries, synergies with relevant projects, presentations to students and pupils, publications in conferences and journals (2 ISI and BDI conferences, 2 ISI journals), social media (Linkedin and Twitter), project webpage.
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