The crucial factor concerning the application of thermotropic glazing is the switching range. For thermotropic hydrogels, thermotropic polymer blends and thermotropic systems with fixed domains maximum switching ranges of 77%, 52% and 25% are achieved, respectively. According to this for an all polymeric flat-plate collector with twin-wall sheet glazing and black absorber thermotropic hydrogels, thermotropic polymer blends and thermotropic systems with fixed domains would limit maximum absorber temperatures to 75, 90 and 125°C, respectively (assuming 85% solar transmittance in clear state) [1]. This allows for the application of cost-efficient plastics with more or less advanced engineering properties and temperature-stability as absorber materials for solar collectors. However, no product is commercially available today, which exhibits switching temperatures, the switching performance and the long-term stability needed for solar thermal applications. Thus further research and development on thermotropic materials is required to make the systems ready for the solar thermal market.

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