Solar Cell Power Generation Boosted by Hologram
PV Arrays with Holographic Film Increase 'Green' Energy Output
Jun 23, 2009
A new type of photovoltaic (PV) solar cell array using holographic film has been shown in tests to be able to produce 45 to 65% more electrical energy than conventional solar modules having the same number of cells.
The array consists of strips of cells alternating with strips of film imprinted with holographic patterns. The film, termed Holographic Planar Concentrator (HPC) by its developer, Prism Solar Products, refracts sunlight on to both sides of the PV cells.
The strips of cells and film are sandwiched between sheets of glass in frames that can be mounted on roofs or walls. When mounted at a distance from a roof or wall, sunlight reflected from the roof or wall surface strikes the underside or rear side of the cells, adding to the incident energy.
Energy Benefits of Holographic Solar Cells
The array has three energy-generation benefits, according to a paper in the journal Laser Focus World by Glen Rosenberg and Mike Zecchino of Prism Solar and Raymond Kostuk, professor in the Electrical and Computer Engineering Department and the College of Optical Sciences, University of Arizona:
- The HPC film refracts sunlight from different angles on to the PV cells so that light energy strikes both sides of the cells regardless of the angle of the sun, from high in summer to low in winter.
- By collecting light over a wide angle, the film directs a larger quantity of energy on to the cells than is collected over a narrower angle by a conventional PV array. As a result, the array produces electricity during reduced-light conditions, for longer each day, including dawn and dusk, and when the sky is overcast.
- The HPC film diffracts light at only those wavelengths of sunlight at which PV cells convert light to electricity (400 to 1100 nm). Infra-red (IR) energy is blocked. PV cells, like all semiconductor devices, lose power as they heat. The ability of the HPC to pass energy only at convertible wavelengths means the PV cells remain close to optimum operating temperature and require no external cooling.
PV Solar Array Energy Output
Graphs of the results of on-going tests by Enphase Microinverter System (a manufacturer of solar technology) show that over a 24-hour period in June in Arizona, a test array produced 328 kWh, equivalent of the power needed for:
- 994 light bulbs
- 328 computers
- 10 homes.
It achieved the same carbon offset as:
- Planting seven trees
- Not driving 17 cars for one day
- Not consuming 29 (US) gallons of gasoline.
Advantages of Holograph Solar Arrays
The technology has manufacturing and installation advantages also:
- The HPC film replaces 50 to 75% of the silicon PV material required for a given output.
- It increases the power generated per gram of silicon by up to 300%, Prism says.
- Because of the greater power output and other factors, a solar installation costs less than conventional PV arrays.
- The film is much less expensive than PV silicon. An array of alternating strips of cells and film is less costly to manufacture, and consumes less energy in manufacture, than conventional PV arrays.
- The film can be combined with various types of PV cell and is available for use by other PV array manufacturers, who require only to add a few processing steps to produce arrays.
Alternative Energy for Buildings
Photocell arrays can be combined with wind-power and light-shelves as energy-saving, environmentally-responsible techniques for buildings.
HPC film, invented by Mr Rosenberg, Prism’s chief technology officer, enhances the environmental benefits of PV cell arrays in several ways. The arrays reduce the cost of solar power installations, have a greater power output than conventional arrays, and consume less semiconductor material and energy in manufacture.
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