Our Approach

 

The main new features of our technology include:

The essence of our tracker technology is based on the Suntenna™ element shown in Fig. 3.4A. The Suntenna™ is a refractive steering surface that is embedded in a transparent dielectric to improve the area efficiency of the array. Sunlight incident on an upper optical stator of the Suntenna™ is refracted into an optical rotor of the same refractive index through a thin layer of index matched oil. Hence, there is ideally no refraction or reflection as sunlight passes from the stator into the rotor, but there is refraction as it leaves the rotor via its lower flat boundary. The reflection losses from the various internal surfaces are kept low by using anti reflection coatings at all interfaces between the air and stator and rotor material.

Figure 3.4B shows a representative geometry for conducting electrodes used to digitally drive the Suntenna™optics. The optical rotor has a very low surface conductivity and the optical stator typically about 10x-100x more surface conductivity. The electrodes are arranged to induce forces on the optical rotor by the application of voltages---electrodes on the internal surfaces or the flat surfaces of the optical stator are possible. Highly conducting and transparent electrodes are located near the inside surface of the optical stator and juxtaposed to the optical rotor. The optical rotor and optical stator are separated by a very thin air (or vacuum) gap. The oil index-matching gap is on the order of 50 μm and is always present, even when the optical rotor and optical stator are in “contact” with each other, due to small surface imperfections. The optical rotor essentially rides on an electric force-field located in the gap region. There are no electrodes on the optical rotor, however, a virtual electrode is induced on the optical rotor by electrical means---the same as static cling found in clothes after they are pulled form a hot dryer on a cold day.

 

FIG 3.4 A-G eTracker Principles. In Fig. 3.4 (A) the basic idea behind the optics of an eTracker is shown. By using transparent media having a matched refractive index between adjacent rotors and stators then only the flat boundary within the optical rotor is capable of refracting light. Because the optical boundary is within a media having a refractive index greater than unity it is possible to avoid shadowing of one optical rotor by its neighbor. This allows the trackers to have a more efficient packing than current trackers that operate in air. Fig 3.4 (B) shows one a schematic of this idea for two-axis tracking of the sun---here we see that air can be used as the second medium. Fig. 3.4 (C) shows the relation of the eTracking layers to an optical concentrator, which is located below the eTracker. Fig 3.4 (D-G) shows the digital nature of step actuation the optical rotor. Electric fields are established by means of electrodes and transistors that are embedded in the glass stator. Then by properly sequencing the voltages on the fast (high-conductivity) electrodes of the stator it becomes possible to inducing opposite charges on the slow (low-conductivity) optical rotor---these are virtual electrodes. The difference in the characteristic time of the fast and slow electrodes is effectively a memory effect and allows electrode to be stepped through a series of angular positions to redirect sunlight into a concentrator. Note, the conductive electrodes (inside of yellow region) have three voltages (−V, 0, +V ) that cause fast E-field changes. Note, these images are only schematic in nature as many more details go into the packaging and robust engineering.