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  (C) Daniel FriedmanRenewable Energy: Films to Increase Solar Collector Efficiency?

Do light-transmitting, heat reflecting films offer efficiency gains for solar collectors? Use of widow films such as Heat Mirror, 3-M's Scotchtint, or Sungain to boost solar collector efficiency.

This article discusses the question of whether or not thin window films designed to control heat and solar gain can improve the efficiency of solar collectors. Text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Photo a rooftop mounted site-built solar collector at page top courtesy of Bob Cheney.

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Light-Transmitting, Heat-Reflecting Films: Should I Use on Solar Collectors?

The question-and-answer article about the indoor use of heat-reflecting window films to increase the efficiency of a solar collector, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Question: Could low-transmission films such as 3M's Scotchtint™ or Heat Mirror™ be used to increase the efficiency of Solar Collectors?

I have heard a lot about light-transmitting, heat-reflecting widow films, such as Heat Mirror™ and 3-M's Scotchtint™. These would seem to be ideal materials for use in solar collector glazings to reduce heat loss. Could these be used in addition to black chrome to improve solar collector efficiency? Are there any solar collector manufacturers using such films in their collectors? - H.M., Bowie MD

Answer:

Low-transmission films such as Scotchtint™ were developed to block solar transmission through window glass into the building interior, avoiding un-wanted heat gain in some buildings. Low-transmission, heat reflecting films would not help solar collector efficiency.

The high-transmission, low-emissivity films such as Heat Mirror™ or 3-M's Sungain™ might boost solar collector efficiencies in some applications, particularly high-temperature collectors in cold climates. In this case, the added insulation value of the film might offset the transmission losses. The actual efficiency gains for the solar collector may still not justify the added expense.

As these products were developed for building glazings (windows), their durability in solar collector applications is in question. The effects of high temperatures, thermal cycling, and high UV exposure on the window glazing film had (in the 1980's) only been studied in a preliminary way. 3M informed us that its Sungain film will become brittle at temperatures above 250 degF., prohibiting its use in some solar collector applications.

While we know of no manufacturer using such films in their solar collectors, we have heard of some experiments in this direction.

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

Original article: Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices.


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Continue reading at SUNGAIN, FILMS, LOW-E GLASS or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Sunspace & Solar Glazing & Shading Articles

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SOLAR COLLECTOR FILMS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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INDEX to RELATED ARTICLES: ARTICLE INDEX to SOLAR ENERGY

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