Dr. Hugh Donahue reached out to me late last week and discussed the projects he has under way re: generating small amounts of electricity in wearable fabrics. The projects invoke photovoltaics in the form of thread, and also piezoelectricity, i.e., converting the mechanical energy of putting stress on an object (in this case a thread) into electricity.
Below is a paper Hugh just send me; the entire piece with extensive end notes can be downloaded here.
DEVELOPMENT OF ENERGY GENERATING TEXTILES & FABRICS
BY HUGH CARTER DONAHUE & CHRISTOPHER PASTORE
We’re researching and evaluating the engineering of piezoelectric and photovoltaic threads, circuits and interconnections to create energy generating textiles and fabrics for vertical applications across technical textile and specialty fabrics and smart fabrics.
Research outcomes will yield findings clarifying how piezoelectric and photovoltaic fabrics and textiles could be integrated into textile switches, flexible keypads, iPod & iPhone controls, mobile phone interfaces, garment heating systems, fabric sensors and wearable lighting systems, OEM markets, soldier fighting ensemble and equipment, and workplace and residential drapes, among other applications, we anticipate.
Piezoelectric elements can be produced as thin ceramic threads for energy generation and harvesting.
Photovoltaic elements can be produced in fibrous forms generating 2.79% to 3.27% efficiency values with stainless steel threads or wires exposed to incident light.
Circuits and interconnections remain challenges and technical barriers to engineering energy generating fabrics or textiles with photovoltaic and piezoelectric threads.
Proof of Concept Approaches
We are designing and engineering energy producing textiles and fabrics using these threads.
For piezoelectric (PZT) threads, research and development focus on automated methods to engineer small diameter PZT fibers in a fabric generator and ranges of textile operations to convert PZT yarn into a generator preform, among other form factors.
For photovoltaic threads, we are evaluating woven fabric or textiles, formed as a series of inter-connected PV filaments and creating electrical circuits, which will be interwoven with other non-PV fibers and threads, for distinct, specific energy generating yields and applications.
We are evaluating knitting as well as weaving.
Economic viability over existing technology
Woven photovoltaic fabrics and textiles constitute manufacturing innovations and technologies to compete in global, photovoltaic markets, currently characterized by national champion, state subsidies to the detriment of U.S. manufacturing, to complement photovoltaic arrays with fabrics and textiles at competitive yields and price points, ideally at $0.50/kW in time, and to create wide varieties of new energy generating textiles and fabrics generating low cost, renewable energy.
Manufacturing productivity improvement
The energy generating fabrics and textiles, which we propose to create, engineer and evaluate, would constitute vertical technologies with applications for technical textile and specialty fabrics, smart fabrics and across many, potential markets in civilian and military sectors.
Technical textiles, defined as “use(s) of fibers, often engineered in fiber, yarn and fabric form, to provide specific technical performance characteristics to meet the final customer/market requirements, either as a final product in themselves or as a component in another product,” constitute $31B US and $120B world wide markets.
Specialty fabrics include awnings and canopies, safety and technical fabrics (including smart fabrics for battlefield, medical monitoring and interactive textiles), industrial and agricultural tarps, fabric structures, fabric graphics (e.g., signage), marine fabrics and geosynthetic materials and narrow fabrics; that is, textiles that are “no more than 12 inches (300mm) in width and are made by weaving, knitting or braiding fibers or yarns with an edge to prevent unraveling.” Specialty fabrics constitute a $18.4B market and are projected to grow to $18.9B by 2015.
Smart fabrics, often defined as textiles with radio frequency capabilities principally for medical and battlefield monitoring applications, constitute a category of specialty fabrics and are valued at $700M. Their definition can extend to fabrics incorporating mechanical, thermal, chemical and magnetic stimuli, currently estimated at $300M annual markets with 36% growth rates.