The solar power industry has been forced to focus on projects that are either massive power stations, or personal-use toys. There is a standing need for practical Community solar collection technologies. A background in the current state of Solar power helps illustrate why there is such a gap. The solar energy industry has taken two major approaches – distributed and collected generation. Each has advantages and disadvantages.
Distributed generation, such as by photovoltaic panels, involves covering available surface are with electricity-generating technology and allowing all the components to directly generate based on the light they receive. The electricity is collected and modified (stepped in voltage or current) to put it in a useful form. Because the temperature and power of distributed sunlight is low grade heat (Carnot efficiency is low), these devices rely on methods that direct convert light to electricity (such as the photoelectric effect). This requires practically that the entire collection surface be covered with electronic ‘circuit board’ – a fact that cannot be avoided and that will continue to keep this method expensive per square meter for many years to come.
Collected generation involves the use of lensing or (more typically) mirrors or mirror arrays to concentrate sunlight onto a generator. The heat at the receiver is based on solar influx, the temperature is based on concentration factors. The concentrated light is high-grade heat energy, and as such can be used to operate convention engine cycles (Stirling, etc) as well as being useful for residential and commercial heating for water or climate control. Because of the Carnot limit concepts, concentrated solar has potential to be significantly more efficient than distributed solar. However, it has not yet been able to fill the scale gap to be used as ‘community’ solar generation. The two primary categories of concentration are solid-state and controlled-array collection. Solid-state collection is hard to scale up, and controlled array is hard to scale down (economically), making community solar difficult.
Solid-state collection (using dish or Fresnel lens style collector) can provide massive solar concentrations (or of 5000x incident sunlight). However, outside of niche experiments such concentrations are not very useful as the temperatures destroy all but the most exotic materials. So, the solid-state collectors are aimed on a collection surface that reduces the concentration to a more practical 500x or so. This allows more useful heat levels fur use in engine cycles and utilities (A/C and water heating). These dish collectors must be driven to aim at the incident sunlight, and thus must be entirely mounted on a moving platform. While reasonable on a small scale (<10 ft diameter), large dishes become unsightly and unwieldy. No one wants a giant satellite-dish on their roof! So these collectors are limited in scale and unsightly – individually they do not provide enough power for a large scale system, and are not marketable on a small scale.
Controlled-array collection involves the aiming of a large field of discrete mirrors at a common collection site. This technique has been used at some of the world’s largest solar collectors – where hundred of mirrors (each the size of a tennis court!) are aimed at a generation tower. This allows large areas of land to be covered with mirrors and high grade heat to be generated. However, compared to solid-state collection, controlled-array collection is relatively hard to scale down as each individual mirror needs to be aimed and controlled throughout the day. If controlled arrays could have thousands of mirrors on a scale from 1″ to 12″ diameter, then rooftops and community spaces could collect useful energy without unsightly dishes as in solid-state collection, and at much high practical efficiencies than distributed solar. The present invention makes such collection possible.
By linking all mirrors together in a clever fashion, the entire array can be controlled with only a few driving motors. The novel kinematic mechanism distributes the control motion across the array in such a way that every mirror is aimed exactly as need for its position relative to the collector. Of course, such a mechanism has many complex mechanical pieces which must be manufactured – but the inherent design makes such concerns a non-issue. The mechanism is a tessellation – every unit-cell of the machine is identical. This means that a manufacturing method like 3d printing is ideally suited so create the machine using an array of evenly spaced printing heads. Using ~100 print heads on a gantry could produce an entire array in several minutes with no manual intervention or assembly required! The concept easily scales from 1″ to ~4″ mirror diameters – the practical size for community solar projects – and can be shown to produce concentration levels on the order of 500x.
