Co-Director, Power Textiles Limited and Emeritus Professor of Physics, Heriot-Watt University
John has over 40 years experience in research and development of thin-film materials for photovoltaic solar cells and other engineering applications, especially using plasma processing. He retired as Head of Physics at Heriot-Watt University in 2012 and is a joint Director of Power Textiles Limited, founded in 2007 to develop flexible solar cells on textiles. Currently he is on the Technical Advisory Board of Evince Technology Limited, that develops CVD diamond devices, and gives courses on Photovoltaic Solar Power for the European Energy Centre. Research results have been presented at international meetings and published in over 200 papers and book chapters. Technology was transferred to companies and research institutes in several countries and he has supervised over 30 successful PhD and MSc students. Last year he worked with a small group and the Turing Trust to design and deliver a solar-powered computer laboratory for Malawi. He holds BSc and PhD degrees from Durham University, is a Fellow of the Institute of Physics, and is a Chartered Engineer and a Chartered Physicist.
- Photovoltaic Solar Textiles
- Solar cells are an option for powering active electronics on textiles but should be fully integrated to avoid compromising the flexibility and handle of the basic fabric. Photovoltaic (PV) cells conventionally use rigid silicon wafers but there are thin-film options offering acceptable performance (with cost and fabrication advantages) although some are sensitive to moisture and oxygen, and others require process temperatures outside the range of most flexible materials. Coating on fabrics is also influenced by their texture, elasticity and surface roughness.The demands of a flexible structure affect the choice of the other parts of PV cells, namely their electrical contacts and any encapsulation layers. The two alternative routes to a textile PV design are: (i) coat the fabric with the successive layers needed to make a sandwich device, or (ii) coat individual yarns with these layers and then process them into a fabric, e.g. by weaving. The pros and cons of both will be discussed.
Our own textile PV construction will be explained, for woven polyester using thin-film silicon. This includes methods for ameliorating the electrical discontinuities that a woven fabric presents on flexing. The resulting performance is a trade-off between layer thicknesses and light-to-electricity conversion, stiffness against flexibility.