CLOUD GEL is made of long chain polymer molecules and water. The polymer chains have parts that attract water molecules and parts that repel them. When they are dissolved in water, the separated chains are too small for light to see, so it passes through undeflected, and the Cloud Gel is transparent. (Figure below, on left) But when this solution is heated, the polymer chains vibrate until their water attracting parts can no longer hold onto water molecules. This makes the polymer chains and water repel each other, so the chains curl up into balls, like spaghetti on a fork. These balls are large enough to deflect light, so the glazing looks white and reflects solar heat. (below, right; see also Section 14, Figure 2)

When Cloud Gel is used for illumination rather than collecting heat, a dye is added to make it warm up under direct sunlight and turn reflective. In cloudlight, the Gel cools below its clouding temperature and clears, admitting a constant level of diffuse illumination; all day, all year. (see Section 14, Figure 3)

LOW-E works like a mirror to invisible heat radiation, reflecting it back to its source. But the heat reflecting silver layer in Low-E is only 50-150 atoms thick, so it is penetrated by more energetic light, making it transparent. (see Section 14, Figure 1)

When I (Day Chahroudi) invented Low-E, the literature consistently reported that it is impossible to make an optical quality silver coating less than 5000 atoms thick. My colleagues at MIT concurred for good reasons. But I fooled the first silver atoms arriving to start a coating into thinking they are landing onto silver, so they have no reason to ball up with other arriving silver atoms, like mercury. Actually, the silver atoms land on a thin layer of a material carefully designed to mimic silver, but be transparent. The completed silver layer is then coated with a protective layer of this material. These three layers have a continuous crystal structure across their interfaces, so the silver resists corrosion and lasts for 40 years.

This transparent pseudo silver material is designed to also greatly increase the light transmission of the silver layer by doubling as an anti-reflection coating -- as on eyeglasses and camera lenses. Light transmission is further increased because, in a silver layer this thin, its electrons can't move as quickly as the vibrations of light, and so can't reflect it.

When I had just started in solar, Harold Hay told me that three times as much energy falls on a building's surface, in the form of sunlight, as is used inside it. As a materials scientist, I said to myself, "Then it's easy; just make the building's surface from materials that gather this energy." The only hard part was that these materials did not exist.

Inspired by the work of Maria Telkes and Harold Hay, I invented: the field of transparent insulations in general, and Low-E in particular in 1971 (1); its manufacturing machinery in 1976 (2); optical shutters for solar heating and illumination (Cloud Gel) in 1971 (1); its manufacturing machinery in 1988 (3); building envelopes made of transparent insulation and optical shutter (Climate Envelope) in 1971 (1,4); and conventional building designs which are efficiently solar heated in cloudy winters (Weather Panel) in 1981 (4).


Because the Low-E window coating is only 400 atoms thick, it is invisible and costs only $0.03 per square foot to manufacture. Its thin film of electrons vibrate from heat radiation, thus reflecting it, but they have been placed in an environment where they can't keep up with light's faster vibrations, and thus transmit it.Developed and brought to market for only $6 million, enough of this next-to-nothing coating of electrons has been made to cover Rhode Island, save 14 million lives from pollution, and triple window sales to $100 billion. But few people know they are using it.

A wheel or pot is useful
From the hole at its center.
The most useful thing is emptiness.

Letting the river reveal its internal currents,
Seeing a small place where a small change
Changes the whole river flow,
A true leader is invisible.

- Lao Tzu

Similarly, the Cloud Gel glazing appears to be merely clever and cheap, but with Low-E it can redirect the flow of one sixth of world energy use from under the ground to the sun. This ability comes from molecules choreographed to do just the right job: liking water when cool, but preferring each other when warm, and thus separating out of a clear water solution into microscopic particles of like-minded molecules that reflect sunlight; but only when they are warm enough to congregate. In this way, Cloud Gel molecules, by changing their associations, prevent overheating from the sunlight photons that Low-E electrons capture by changing their vibrations. Molecules associating, electrons vibrating; what could be more simple or cheaper?

Outside the clean energy box, fundamental innovation in exactly the right place creates new markets with explosive growth.

(1) e.g. U.S. patent 3,935,110, Sections 29 and 33
(2) e,g. U.S. patent 4,204,942
(3) e.g. U.S. patent 5,377,042, Section 31
(4) e.g. U.S. patent 5, 524,381, Section 30