US: innovative technologies to reduce air conditioning costs

Two articles present innovative windows to reduce air conditioning costs.
 . A team of researchers at MIT has developed a new way of making windows that can switch from transparent to opaque, potentially saving energy by blocking sunlight on hot days and thus reducing air-conditioning costs. While other systems for causing glass to darken do exist, the new method combines rapid response times and low power needs. Once the glass is switched from clear to dark, or vice versa, the new system requires little to no power to maintain its new state; unlike other materials, it only needs electricity when it’s time to switch back again.
The new discovery uses electrochromic materials, which change their colour and transparency in response to an applied voltage. These are quite different from photochromic materials which tend to have much slower response times and to undergo a smaller change in their levels of opacity. The MIT team overcame that by using sponge-like materials called metal-organic frameworks (MOFs), which can conduct both electrons and ions at very high speeds. Besides preventing glare, these new windows could lead to pretty significant energy savings by drastically reducing the need for air conditioning in buildings with many windows in hot climates.
More information on the MIT website.

. A small Michigan-based company has developed a plastic pane that inserts into existing window frames and is designed to provide the same insulation value as walls but be fully transparent.
The transparent polymer panes are bordered by foam frames that fit into windows. A single pane of the prototype has an R-value (thermal resistance) of 5 and can go up to R-13, based on the number of panes. Windows are the biggest cause of energy loss. According to the company, this product can reduce heating and cooling energy loss by 50-60% and reduce a building’s total energy demand by 10%.
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