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Solar & Alternative Energy

Patent review: Plucking energy from sunshine

This month's featured patent review by analysts from Nerac.
26 September 2007, SPIE Newsroom. DOI: 10.1117/2.2200709.0002

With the exception of certain types of extremophiles such as alvinella pompejana, which thrive near hydrothermal vents in the deep ocean, almost every living organism on Earth is solar powered. Through photosynthesis, plants capture the energy of sunlight which sustains almost all life on our planet. The energy of photosynthesis is partitioned among the individual organisms in the food chain.

This remarkable circumstance is deeply mirrored in our technological world. As with life on Earth, most of the energy consumed by modern technology ultimately traces its origin to sunlight. Only a small fraction of the energy that powers our machines is extracted from nuclear and geothermal sources.

The fossilized remains of plants and animals are the fuel for the fires that electrify buildings and propel transportation systems. We literally pump or dig the stored energy of ancient sunshine from the ground. The wonderful convenience of harvesting ancient sunshine to power our technological world has, unfortunately, unleashed some rather frightening demons that manifest themselves as global warming, dependence on imported oil, and economic destabilization caused by diminishing supplies and rising prices.

The resulting hardships have prompted alternative pursuits for more benign methods of extracting energy from the environment. With so much energy streaming from the sun, it is difficult to abandon sunshine as a source of energy. After all, every square meter of the Earth is bathed with an average of 1,366 Joules every second. The trick is to pluck as much of that energy as possible while keeping expenses to a minimum. This translates into an engineering problem whose solution is to develop very efficient, inexpensive sun-energy capturing devices.

Currently, the best of these devices, photovoltaic cells, do not match the efficiency of photosynthesis, which is one reason solar energy is not yet competitive with energy derived from fossil fuels. In addition, the manufacturing processes for photovoltaic cells are expensive. Consequently, the drive toward higher efficiency and better economics is the impetus behind ongoing research related to solar energy. This is particularly true for research on photovoltaic cells. We selected a few recent patent publications on photovoltaic cells and solar energy systems to convey some of the latest research efforts on solar energy.

2007/0095391 A1: Tandem Photovoltaic Devices Based on a Novel Block Copolymer
This patent application published on May 3, 2007 may be important for the development of lightweight thin flexible solar cells. Solar cells with these attributes may become a reality due to "tertiary supramolecular nanophase separated structures" as discussed in this patent application. High-power conversion efficiency is also possible because these structures reduce exciton, carrier, and photon losses.

ABSTRACT: A -donor(D)-bridge(B)-acceptor(A)-bridge(B)- or derivative type block copolymer system used in a tandem device of multiple sub-cells, where donor (D) is an organic conjugated donor (p-type) block, acceptor (A) is an organic conjugated acceptor (n-type) block, and bridge (B) is a non-conjugated and flexible chain, has been designed and preliminarily tested for potential lightweight, flexible shape, cost-effective and high efficiency plastic thin film solar cell or photo detector applications. A 'tertiary supramolecular nanophase separated structure' derived from this -DBAB- block copolymer is expected to improve opto-electronic (photovoltaic) power conversion efficiency significantly in comparison to all existing reported organic or polymeric donor/acceptor binary photovoltaic systems due to the reduction of exciton loss, the carrier loss, as well as the photon loss via three-dimensional space (morphology) and energy level optimizations. The tandem stacking of block copolymer sub-cells further enables optical excitation energy gap grading to improve photon capture of solar spectrum and device efficiency.
PDF of full U.S. Patent application

WO 2007/055931 A2: Organic Photovoltaic Cells Utilizing Ultrathin Sensitizing Layer
This patent application was filed by Princeton University on October 26, 2006 and published on April 18, 2007. The device disclosed in this patent has several photoactive layers, with each layer characterized by different absorption spectra. This allows the device to extract a larger amount of energy from the solar spectrum. According to Claim 27, "The device may comprise a stack of photoactive cells disposed between the first electrode and the second electrode. In such a stack, the series of organic photoactive layers may be part of a first cell in the stack of photoactive cells. The stack also includes at least a second photoactive cell comprising another doner-accepter heterojunction." The claims in the patent elaborate further on the spectral absorption ranges of the different cells.

ABSTRACT: A photosensitive device includes a series of organic photoactive layers disposed between two electrodes. Each layer in the series is in direct contact with a next layer in the series. The series is arranged to form at least one donor-acceptor heterojunction, and includes a first organic photoactive layer comprising a first host material serving as a donor, a thin second organic photoactive layer comprising a second host material disposed between the first and a third organic photoactive layer, and the third organic photoactive layer comprising a third host material serving as an acceptor. The first, second, and third host materials are different. The thin second layer serves as an acceptor relative to the first layer or as a donor relative to the third layer.
PDF of full U.S. Patent application

2007/0119718 A1: Optimizing Photovoltaic-Electrolyzer Efficiency
Hydrogen-powered vehicles offer some hope of reducing our dependence on fossil fuels if the hydrogen is derived from non-fossilized energy sources. This patent application discloses an invention that uses solar energy to extract hydrogen from water via electrolysis. A photovoltaic system and electrolyzer are combined into a single unit in order to maximize the operating efficiency.

ABSTRACT: An array of photovoltaic (PV) module(s) is arranged in series and/or parallel electrical connection to deliver direct current electrical power to an electrolyzer to produce hydrogen. The electric power is delivered by the array at its maximum power point (V mpp ) to deliver I oper at V oper for the electrolyzer. The arrangement of the PV modules in the array, or the arrangement of cells in the electrolyzer, is continually monitored and controlled by an automatic controller system to operate the PV and electrolyzer systems at or near their respective maximum efficiencies. A DC-DC converter may be used to adjust the V mpp to the operating voltage of the electrolyzer.
PDF of full U.S. Patent application

2007/0131271 A1: Integrated Thin-Film Solar Cell and Method of Manufacturing the Same
This patent application claims an inexpensive thin film solar cell that can be mass produced. The integrated solar cell contains several unit cells connected in series on a glass or transparent plastic substrate. The patent application primarily elaborates on the manufacturing details.

ABSTRACT: Provided are an integrated thin-film solar cell and a method of manufacturing the same. The method comprises forming and patterning a conductive material to be adjacently spaced a predetermined distance apart from each other on a substrate forming a solar cell (semiconductor) layer on the resultant substrate obliquely depositing a first transparent conductive material on the solar cell layer etching the solar cell layer using the first transparent conductive material as a mask and obliquely depositing a second transparent conductive material on the resultant substrate, and electrically connecting the conductive material with the first transparent conductive material.
PDF of full U.S. Patent application

WO 2007/066098 A1: Organic Solar Cell
The solar cell described in this patent employs an organic acid to absorb electromagnetic radiation within a wavelength range from 400 to 3000 nm. An organic ionic-crystalline photoelectric layer is placed between two electrodes. The resistivity of the organic ionic-crystalline layer is approximately equal to the resistivity of crystalline or amorphous silicon. The solar cell may contain up to one thousand monolayers.

ABSTRACT: The present invention relates to an organic solar cell based on an organic ionic-crystalline photoelectric layer. In a preferred embodiment, the present invention provides an organic acid of general structure: Formula (I) wherein said acid absorbs electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm, and aqueous solution of its water- soluble salt is capable of forming a photoelectric layer of rodlike supramolecules on a substrate. In another preferred aspect, the present invention provides an organic solar cell comprising two electrodes facing each other, an organic ionic-crystalline photoelectric layer situated between two electrodes and contacting with the first electrode and an electrolyte which is situated between the organic ionic-crystalline photoelectric layer and the second electrode and impregnates the organic ionic-crystalline photoelectric layer. The organic ionic-crystalline photoelectric layer is capable of absorbing electromagnetic radiation in at least one predetermined spectral subrange within a wavelength range from 400 to 3000 nm. This layer consists of rodlike supramolecules, which are comprised of the molecules of at least one organic compound of the general structural Formula (II).
PDF of full U.S. Patent application

James J. Marie is a Nerac Patent Analyst. Nerac's Intellectual Property Solutions provide a practical understanding of the IP landscape, helping organizations to make informed decisions about R&D planning and business strategy development. Nerac analysts work with clients in the following critical areas:
  • Patentability and Invalidity
  • Patent Portfolio Analysis
  • Commercialization Strategy
  • White Space Analysis