Harnessing solar power to provide clean energy

Zebib Yenus Nuru is an Associate Professor in the Department of Physics, Adigrat University in Addis Ababa, Ethiopia. Zebib is also a fellow of the Future Leaders - African Independent Research (FLAIR) programme. FLAIR is a partnership between the Alliance for Accelerating Excellence in Science in Africa (AESA) and the Royal Society of London, supported by the Global Challenges Research Fund (GCRF). FLAIR supports talented early-career African researchers who have the potential to become leaders in their field.

FLAIR is implemented through the AESA Platform. AESA (The Alliance for Accelerating Excellence in Science in Africa) is a funding, agenda-setting, programme management initiative of  the African Academy of Sciences (AAS) in partnership with the African Union Development Agency (AUDA-NEPAD) and with the support of Wellcome, Bill and Melinda Gates Foundation and the United Kingdom Department for International Development (DFID).

The fellowship provides the researchers with an opportunity to build an independent research career in an African institution and to undertake cutting-edge scientific research that addresses global challenges facing developing countries. In this blog, Zebib discusses her research project, which seeks to harness solar radiation to provide access to clean energy for the community.

Seeking a cost-effective renewable energy source

Non-renewable energy from fossil fuels such as coal, gas and oil are used widely across the globe and particularly in Africa. Fossil fuels generate greenhouse gases responsible for global warming. This environmental problem and the ever-increasing demand for energy, has motivated researchers to look for alternative renewable energy sources.

Africa’s local renewable energy resource from solar radiation is one of the highest in the world. The average annual solar radiation in Africa is about 9000 W/m2 for Africa compared with about 150 W/m2 for USA, and about 100 W/m2 for Europe and the United Kingdom.

Zebib and her team conducted some field work in the rural areas of Tigray region, Ethiopia, to understand the source and use of energy among households. They found that most households use wood and cow dung as sources of energy for cooking. There are no alternative energy sources like electric stove or solar power and people have no awareness about alternative clean energy sources. Households are also overcrowded and are prone to health risks because of the indoor smoke, a leading cause of avoidable deaths in rural areas. Women are most affected because they often cook for their families and spend a lot of time in smoky kitchens.

Thus, it is important to look for alternative clean energy sources. To harness solar energy, solar-thermal systems are the most important candidates. The critical part of these systems is the solar absorber surface. To increase the solar-thermal conversion efficiency, the solar absorber surface should capture maximum solar radiation in the solar region while emitting low in the infrared region.

The future is green

My project is geared towards preparing a cost-effective solar absorber material, which can be able to harness maximum solar radiation in the solar spectrum region while re-radiating low in the infrared region and should be thermally stable up to 100oC. This will enable people to heat water, to cook and pasteurize milk in rural areas of Africa.

Currently, several solar absorber materials are prepared by different methods such as sputtering, E-beam evaporation, electroplating, and anodization. However, these methods involve expensive and sophisticated equipment, which makes it difficult to scale up the prepared material for further production and possible application. Thus, for the first time, this project uses a simple cost-effective and environmentally friendly ‘’green synthesis’’ method to prepare the nanocoatings, which will provide access to clean energy for the community. Green synthesis is a method that uses only plant extracts instead of chemicals to prepare nanoparticles and it does not require high energy, high temperature, pressure, or toxic chemicals unlike the methods mentioned above.  

The aim of Zebib’s study is to provide a new family of solar absorber material prepared by green technology that can absorb high solar radiation while re-radiating low. As such, we have used cactus plant extract to prepare two (out of four) components of the proposed solar absorber material. We successfully prepared nanoparticles of the two components of the solar absorber materials. The solar absorber materials were then optimized in terms of size, surface roughness, and thickness to achieve good performance (high solar absorptance and low emittance). Preliminary result showed the prepared solar absorber materials achieved high solar absorptance above 93% while re-radiating less than 18%. This indicates that the prepared materials can be a potential candidate to convert solar energy into heat.

What we have learnt is that this method is sufficient to prepare a solar absorber material easily with lower contamination, easy control of parameters and better reproducibility. Currently we are working on how to improve the performance of the prepared materials by incorporating the already prepared materials with the other two components to decrease the re-radiating value to less than 10%, and also parallelly we have started investigating durability (stability). If it can be tailored to operate at temperatures up to 100°C, it will be compliant with milk pasteurization, cooking, and heating water. The study of durability is very critical in order to evaluate whether the material can be applicable under harsh weather conditions or not.

Making an impact

By providing the rural population with access to clean and low-cost energy source, this project will directly contribute to efforts in addressing the global health and environmental challenges in Africa and other developing countries.

This research project is realized because of the generous financial support of the AAS, Royal Society and GCRF through the FLAIR fellowship. As an early-career researcher, this fellowship changed my career path substantially. It financially supported me to pursue my area of expertise and enabled me to access some of the world’s finest experimental facilities in different parts of the world. It also helped me establish national and international collaboration within Africa (Research & Technology centre – Tunisia,  & UWC, UNISA & iThemba LABs -South Africa),  UK (University of Nottingham), Canada ( University of Alberta & National Institute of Nanotechnology) and USA (University of Texas &  Arizona State University) and also to contribute towards capacity building of my colleagues at Adigrat University. It also helped me to acquire additional funding from the world Academy of Science (TWAS) to purchase additional research facilities, and also student mobility grant from the National Science Foundation (NSF) at Arizona state university- USA. I have also become an AAS Affiliate, which helps me to access professional and career development opportunities. All these and other upcoming opportunities will ultimately direct me towards becoming an independent researcher who contributes substantially to the community, continent, and world.