DE20021870U1 - Inexpensive, large, three-dimensional, solid solar cells with high effectiveness - Google Patents

Description

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2. Title: Cost-effective, large, three-dimensional, solid solar cells with high efficiency

3. Description: Cost-effective, large, three-dimensional, solid solar cells with high efficiency

4. State of the art: Classic solar cells are two-dimensional, have the shape of panels ("boards"), a nominal output (nominal efficiency) that is achieved under certain, usually optimal conditions during a mostly short period of the day (optimal position of the sun, optimal incidence). The nominal efficiency is usually 5 to 17%, and even more for prototypes. Outside of this period (i.e. in the morning, early afternoon, and evening), the efficiency drops drastically. Panel-like solar cells, if they are not mounted on roofs, which is also expensive, also require support structures that must be very stable so that wind coming "from behind" does not blow the panels away. To increase efficiency, tandem systems (two layers one below the other) were also used, systems that move the panels ("boards") towards the sun (costly), mirrors mounted in front of the panels or small prisms mounted directly above the panels, appropriately "roughened" glass, etc., whereby the two-dimensional "board-like" construction and the resulting efficiency losses in the morning, early morning, afternoon and evening remained. All two-dimensional solar cells (panels, "boards") have the disadvantages mentioned, regardless of the solar-active material (polycrystalline, amorphous, nano-crystalline ¹² , semi-organic, organic ³ ). The resulting high costs of photovoltaic electricity are also largely due to the disadvantages mentioned, since, in contrast to other energy systems, the already low nominal output has NOT been achieved for a large part of the operating time and thus the CUMULATIVE amount of energy generated in one day is low given the existing production costs. In order to compete with other forms of energy, it is not necessary to use short-term (e.g.

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It is not the ideal conditions (e.g. around midday) that determine the effectiveness achieved, but rather the relationship between costs and the CUMULATIVE amount of energy generated during the entire day. This is increased several times over by the new concept of the three-dimensional, physical solar cell at a similar cost.

5. Problem (statement of the effects to be achieved with the invention):

The invention specified in the protection claim is based on the problem of creating a solar cell which operates with the nominal efficiency almost independently of the position of the sun, in particular during the entire daytime (in the sense of the presence of daylight), and thus achieves a CUMULATIVE energy yield per day that is several times higher at production costs comparable to or lower than those of previously existing two-dimensional solar cells.

6. Solution

This problem (5) is solved by solar cells with the following features:

6.1. Three-dimensional pyramid-shaped bodies of great height (i.e. usually higher than approx. 1.30 metres) whose

6.2. Base plate is a mirror coated with a transparent solar active layer (thin polycrystalline, amorphous, nanocrystalline, semi-organic or organic) whose

6.3. Side surfaces consist of SEMI-transparent mirrors which are translucent from the outside and reflective from the inside, whose

6.4. INTERNAL SURFACES are coated with TRANSPARENT solar active material (thin polycrystalline, amorphous, nano-crystalline, semi-organic, organic), which thus

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6.5. Generate multiple reflections (and thus have a higher energy yield in transparent solar-active materials and highly transparent, semi-transparent mirrors compared to two-dimensional, "board-like" cells), which

6.6. Due to their physical nature, they can be irradiated from all sides at any time of day without a tracking system, thus achieving the nominal effectiveness almost throughout the day (in the sense of the presence of daylight) and thus, given the effectiveness of the solar active layer, achieving a CUMULATIVE energy yield over the day that is usually several times higher than that of two-dimensional panels ("boards").

7. Rating:

1.) Inventive development step / level of development: A gain of several 100% of cumulative energy yield per day is a considerable advance.

2.) Since solar cells available on the market and in literature are TWO-DIMENSIONAL, the development of the three-dimensional solar cell was not obvious to the "expert".

8. Differentiation from other solar cells:

The utility model relates to solar cells in which at least one of the surfaces ABOVE the base plate (in the sense of: away from the base plate) is coated with transparent solar-active material, but not to panels in which there is only a prism or mirror ABOVE the solar-active layer on the base, which has no solar-active layer on the inside. Constructions in which the height of the top of the pyramid is approximately less than a third of the edge length of the smaller side above

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the base plate (in the sense of: away from the base plate) are also not included (criterion of "corporeality").

9. Further explanations (see figure)

In order to produce photovoltaic electricity with the nominal efficiency throughout the day (in the sense of the presence of daylight), the concept of (1.) large (greater than 1 meter in height) and (2.) three-dimensional solar cells (see drawing) was developed.

The development consists of:

1.) A base plate (figure: side (a), base plate: (B)), which is usually rectangular or square. This base plate consists of a mirror, ideally with high reflectivity. The reflective side is on top. ON the mirror there is a layer of transparent solar-active material (C). This material can be, for example, thin polycrystalline, amorphous, semi-organic, organic or even polycrystalline, as long as it is transparent. All available solar-active materials can be used, as long as they are transparent . In the drawing, the solar-active layer is shown in dashed lines.

2.) Above the base plate there is a three- or four-sided pyramid made of transparent mirrors (Figure: sides (b), (c), (d) and possibly (e)). These are arranged so that the reflective side (A) is on the INSIDE of the pyramid and the transparent side is on the outside. Incident light thus enters the construction, but to a large extent does not leave (see beam path (D), Figure: numbers (1) to (6)).

3.) On the INSIDE of the mirrors there is a thin layer of transparent solar active material (C). This can be thin, polycrystalline, amorphous, nanocrystalline, semi-organic or organic. The important thing is that it is transparent.

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4.) In order to achieve the nominal effectiveness over a LARGE part of the day (in the sense of the presence of daylight), the body is LARGE (minimum height (figure: hmin) approx. 1.30 m). The tip of the pyramid is therefore at a distance of at least one third of the edge length of the smallest side of the base plate ABOVE the base plate; for a square base plate with an edge length of one meter, this means at least thirty centimeters above the base plate. As a rule, the tip should be 1.60 to 1.90 m above the base plate for a base plate with an edge length of 1.50 meters. The solar cell is therefore a BODY (and not a panel (board)).

This means that the sun can shine into this body at any time and so the nominal efficiency is achieved without a tracking system not only at midday but also (almost) in the morning and evening (result, inventiveness: high cumulative energy yield). The multiple reflections compensate for the larger surface area. The physical nature of the construction means that the solar cell can be easily set up anywhere, is easy to transport (in parts), is almost not susceptible to wind and, above all, does not shade itself but, as already mentioned, delivers the nominal efficiency (nominal power) almost all day (in the sense of the presence of daylight). This means that the costs of generating solar power should fall to a third compared to two-dimensional solar cells. Furthermore, the three-dimensional solar cell can be manufactured using available technologies (float glass, vapor deposition for semi-transparent mirrors / solar-active layer, or, if nanocrystalline layers are used, from liquids). The need to use THIN layers not only reduces costs by saving material, but also contributes to environmental protection. Further future advantages: Developments in the field of nanotechnology mean that new transparent solar-active materials can be expected. The recently discovered possibility of storing light opens up the possibility of filling the interior with a corresponding gas and thus increasing the yield. The same applies to the applicability of new materials,

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which, for example, change their transparency / reflectivity depending on, for example, applied voltages

Numerical example (figure): A solar active material with 10% efficiency is used, a semi-transparent mirror with a reflectivity of 95%.

Step 1, primary effectiveness: Due to the multiple reflections, an energy yield of approx. 40% is achieved (already corrected downwards due to refraction losses not visible in the drawing), so the larger area is compensated.

Step 2, secondary effectiveness: The actual contribution to the increase in efficiency is secondary effectiveness: This is achieved by the fact that the nominal output (nominal effectiveness), see beam path, is achieved almost all day (in the sense of the presence of daylight), i.e. almost INDEPENDENT of the position of the sun. The CUMULATIVE ENERGY YIELD is therefore several times higher than that of classic two-dimensional solar cells (several 100 percent). This is achieved, see beam path, by carrying out the same number of multiple reflections with appropriately large bodies, regardless of whether the sun is on the right, in the middle, on the left, high or low.

Further advantages: (1) A tracking system is not necessary; (2) neither are roofs for fastening or stable structures (supports). (3) In principle, any material can be used as a solar-active layer, provided it is transparent. (4) The entire construction can be made from float glass, for example; other support materials are also conceivable, provided they are transparent. (5) Since the solar-active layer is INSIDE, weather protection is not necessary. In principle, another transparent solar-active layer can also be attached outside. (6) The bodies can be transported in panels and easily set up anywhere without personnel (e.g. on unused farmland, fallow land, etc.).

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Further perspectives: Future development work can therefore focus on increasing the transparency of solar-active materials as well as on increasing the reflectivity of semi-transparent mirrors. Future developments will therefore be characterized by ever lower material consumption (thin layers) and thus contribute to further conservation of resources. There is still considerable potential here.

10. Literature (selection)

1. Bach, U., Lupo, D., Comte, P., Moder, JE, Weissö, F., Salbeck, J., Spreitzer, H. & Graetzel, M. Solid-state dye-sensitized mesoporous TiO ₂ solar cells with high, proton-to-electron conversion efficiencies. Nature 395, 583-585 (1998).

2. Tennakone, K., Kumara, GRRA, Kottegota, IRM, Wiljayantha, KGU & Perera, VPS A solid-state photovoltaic cell sensitized with a ruthenium bipyridye complex. J. Phys. D: Appl. Phys. 31, 1492-1496 (1998)

3. Schön, H., Kloc, Ch. & Buttlog B. Efficient photovoltaic energy conversion in pentacene-based heterojunctions. Applied Physics Letters 77, 2473-2475 (2000).

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Figure: Concept drawing of large three-dimensional solar cells with high efficiency. Three- or four-sided (sides (a) to (d) or (a) to (e)) pyramid, height (hmin) approximately greater than 1.30 m. Reflective base plate (B), side surfaces as semi-transparent mirrors (A), reflective side inside, transparent from the outside, transparent solar-active layer, dashed inside (C), beam path (example, (D)), multiple reflections (selection: (1-6), refractions not shown).

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Claims (1)

Solar cells which are characterized by the fact that they are three-dimensional, solid and pyramid-shaped, in which the construction height is at least approx. 1/3 of the edge length of the base plate (usually from approx. 1.30 to 2.20 METERS), which have SEMI-transparent mirrors as outer surfaces (transparent side outside, reflective side inside), whose INNER surfaces are coated with transparent solar-active material (thin polycrystalline, amorphous, nanocrystalline, semi-organic, organic), whose base plate is a mirror coated with transparent solar-active (thin polycrystalline, amorphous, nanocrystalline, semi-organic, organic) material, which achieve the nominal efficiency for almost the entire day (in the sense of the presence of daylight) due to multiple reflections AND solidity (resulting in almost complete independence from the position of the sun during the day, in the sense of the presence of daylight).