Collaborating to develop sustainable energy in Africa

Mohammed Elshafie
03 July 2017

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Green energy

A collaborative research project addressing challenges to the development of sustainable energy in Africa has the potential to deliver global benefits, says Mohammed Elshafie.

Understanding the mechanical behaviour of different soil types is key to successful and economic construction. There is a wealth of knowledge on saturated soils, such as the UK’s natural soils, that has allowed wonderful feats of underground engineering - London Underground, the Channel Tunnel, Crossrail and the Thames Tideway Tunnel being more recent examples. The UK has pioneered tunnelling achievement and is a world-leader in this area and in geotechnical engineering more generally.

However, there are significant parts of the world where natural soil is partially saturated; less is known about the behaviour of unsaturated soils. This lack of understanding restricts economic growth as the construction of infrastructure on this type of ground can be challenging and prohibitively expensive.

In Africa, more power generation is needed to meet existing and future demand - half a billion people (half of Africa’s population) lack access to electricity - and whilst Africa is rich in renewable energy resources, particularly wind, the areas suitable for turbines contain unsaturated expansive soils. Expansive soils are sensitive to moisture changes; they expand when only a small amount of water is added and shrink as they dry out. 

Climatic conditions that include wet and dry seasons, particularly in Chad, Sudan, Tanzania and South Africa, combined with unsaturated expansive soils result in complex mechanical behaviour affecting the suction mobilised in the soil, shear strength and ability to resist imposed loads. This impacts on foundation piles subjected to the cyclical horizontal loading of wind turbines and means that the application of the principles of saturated soil mechanics in the foundation design - as practised across Europe and much of the developed world - is inadequate in many parts of Africa. 

Foundations that experience highly dynamic and concentrated loading, in areas of unsaturated soil, have to be designed on a project-by-project basis as ground conditions are site specific. This is critical as the complex dynamic loading can cause movements in the foundations that are large enough to trigger problems in the performance of the turbines, which are sensitive to ground movements. These issues are financially unsustainable in developing countries – design of the foundations must be accurate at the start as remedial work is prohibitively expensive. All of these factors point to the value of making an advancement in the understanding of the mechanics of this soil type.

WindAfrica is a new and collaborative research project that aims to make a significant contribution to this understanding. Funded by EPSRC as part of the RCUK Global Challenges Research Fund, this three-year project, led by Durham University, benefits from academic expertise from the Centre for Smart Infrastructure and Construction (CSIC) and the Laing O'Rourke Centre for Construction Engineering and Technology at the University of Cambridge and the University of Pretoria in South Africa, as well as visiting researchers from world-renowned geotechnical engineering experts. 

The project, which is supported by industry project partners including Parsons Brinkerhoff, Jones & Wagener and Gaia-Wind, is uniquely positioned to address geotechnical challenges on this scale. Importantly, the project also has the backing of government and local experts in Sudan. The collaborative design of WindAfrica means all participating countries will have access to and benefit from the resulting knowledge and experience.

Fieldwork, which is scheduled to begin this year, will be conducted in Sudan where the soil is representative of a large part of East Africa. Extensive analysis will be completed on the collected field data, combined with physical modelling and numerical analyses. The combined data will be studied and developed into a simplified semi-analytical tool for foundation deformation and bearing capacity and provide foundation design guidelines for wind turbines in Africa. Guidelines can be applied by designers working in similar ground conditions, considerably simplifying the design and construction of wind turbine foundations on a project-by-project basis. This approach will relieve the current financial burden associated with constructing foundations for wind turbines.

Applying these guidelines will enable the growth of a sustainable energy market in Africa and also provide UK industry with the advantage to become world leaders in this area. 

Dr Mohammed Elshafie is a co-investigator at the Centre for Smart Infrastructure and Construction and the Laing O’Rourke lecturer in construction engineering at the University of Cambridge and will be leading the field-testing in Sudan for WindAfrica. See www.centreforsmartinfrastructure.com