Design Goals and Challenges for a Photovoltaic-Powered Electrochromic Window Covering

As the technical issues of performance and durability of electrochromic (EC) windows near resolution, more attention is being focused upon the economics of 'smart' window fabrication, installation and operation. A retrofit EC window covering that could be readily applied to existing windows could have several economical advantages, particularly if it were photovoltaic (PV)-powered. Such a windowcovering could be produced on a flexible polymer substrate that would be adhered to the inside surface of a window. It could be conveniently replaced as newer, better coverings were developed and would not have to have as long a proven service lifetime as would a permanent window coating. A PV-EC window covering could also obviate the need for expensive electrical wiring for power and controls.Along with the advantages of a self-powered 'smart' window covering come disadvantages and new technological challenges. In this article, we will describe the design options and challenges associated with this retrofit concept which are presently being studied at NREL.