It is widely agreed that the average energetic input from solar irradiation on the planetary surface is 1000 W/m² and that a PV panel, depending on it's efficiency ratio, transforms a part of this electro-magnetic energy into electric energy. The question is what happens to the difference between the harvested and the transformed energy?
A part of it is transformed into heat energy obviously, but is this effect strong enough to explain the difference or could there otherwise be "hidden“ and "yet untouched“ forms of energy?
Dear Axel,
Your questions are meaningful and rise important issues in science and engineering.
Manuel gives insight full answers and comments. But let me add some additions to that of Manuel.
If you follow the evolution of the solar cell efficiency you find appreciable enhancements. According to the given link http://www.extremetech.com/extreme/184977-new-material-could-provide-massive-boost-to-solar-cell-efficiency
the efficiency reached 43% in practice for expensive multijunction solar cells and 22 percent for cheap silicon solar cells.
The Multijunction cells that capture a larger section of the sun’s spectrum can reach up to 87% efficiency.
From these data, it is clear that that there exit scientific and technical plans and solutions to boost the solar cell conversion efficiency to very appreciable values.
We see also that there is a long way to go to reach the phyical limit of the solar conversion efficiency. The question is how far these converters will be economical?
The scientists and engineers know where the the incident solar radiation go. The useful part and the lost part. They know the loss mechanisms. They are busy with finding the ways to illuminate or at least reduce these losses keeping the cost affordable.
-The two main loss mechanism are:
The not complete absorption of the wide spectrum of the sun black body radiation
and the recombination and ohmic losses in the internal of the cell.
Wish that i shed some light on your question.
It explains for most of it. If you look at Schockley and Queisser's paper on the detailed balance for solar cells from 1963 they show quite clearly that most losses are either heating or transmission losses (i.e. cell simply doesn't absorb certain parts of the solar spectrum). There are also some thermodynamic losses (because the cell is a black body at temperature T that radiates energy), and obviously the losses that account for the difference between a real cell efficiency and the detailed balance limit, but these are mainly different types of non-radiative recombination that also leads to heating (and non-zero reflection of incoming light). So no, most of it really is heat, and lack of absorption (either by reflection or by transmission of light).
Thank you Mr. Sudhakar and Mr. Schnabel - that was valuable input for me. I am heading towards a slightly different theory than Schockley and Queisser which is under evaluation by me and my team at the moment under reality testing (not lab) conditions, at least as soon as the bad weather stops.
Dear Axel,
Your questions are meaningful and rise important issues in science and engineering.
Manuel gives insight full answers and comments. But let me add some additions to that of Manuel.
If you follow the evolution of the solar cell efficiency you find appreciable enhancements. According to the given link http://www.extremetech.com/extreme/184977-new-material-could-provide-massive-boost-to-solar-cell-efficiency
the efficiency reached 43% in practice for expensive multijunction solar cells and 22 percent for cheap silicon solar cells.
The Multijunction cells that capture a larger section of the sun’s spectrum can reach up to 87% efficiency.
From these data, it is clear that that there exit scientific and technical plans and solutions to boost the solar cell conversion efficiency to very appreciable values.
We see also that there is a long way to go to reach the phyical limit of the solar conversion efficiency. The question is how far these converters will be economical?
The scientists and engineers know where the the incident solar radiation go. The useful part and the lost part. They know the loss mechanisms. They are busy with finding the ways to illuminate or at least reduce these losses keeping the cost affordable.
-The two main loss mechanism are:
The not complete absorption of the wide spectrum of the sun black body radiation
and the recombination and ohmic losses in the internal of the cell.
Wish that i shed some light on your question.
Thank you Axel.
I say Toll! Toll! The energy problems will be solved forever and Noble will be little for you. Do not forget the Land of Pyramids and SUN SHINE. IT WAITS YOU!
wish you success
i dont have anything more than what @Manuel Schnabel said. But i definitely want to wish you luck. Schockley and Queisser's limit is well explained in their paper, but challenging a theory like that is what science will always admire.
Good luck
chittesh vc
Dr. Prof. Zekry, Dear Chittesh,
thank you for your supportive words. So far I can only say that we charged from PV panels and thermo-electric generators without current. It is now up to us to fully understand the underlaying processes and energy transformations.
If anybody has input for me especially in the area of ionic charging of rechargeable batteries I'd be glad to read.
Dear Axel,
I know that there is a combined photo voltaic generator and solar heating. In this way one can increase the conversion efficiency of the system. If you please can you describe your system in more details such that we can share the ideas with you?
wish you success.
One of the area in which you can find energy reserves in PV systems is in the energy efficiency. Current development of the PV systems is focused on improving existing modules and system components by increasing their energy efficiency and reducing material usage. Technologies like PV thin film (using alternative semiconductor materials) or dye sensitive solar cells are developing quickly and present a huge potential for cost reduction. The mature technology crystalline silicon, with a proven lifetime of 30 years, is continually increasing its cell and module efficiency (by 0.5% annually), whereas the cell thickness is rapidly decreasing (from 230 to 180 microns over the last five years). Commercial module efficiency varies from 14 to 21%, depending on silicon quality and fabrication process. With a deepened understanding of the fundamental photovoltaic processes and the development of tailored materials and device architectures, we have seen a rapid increase in the efficiency of PV devices to over 10%, which attracts tremendous commercial interests for further development and manufacturing. There is recent progress in the field of photovoltaics, particularly on various innovative device architectures and optical designs to maximize the power conversion efficiency of PV cells. Currently, PV research focuses on boosting solar cell conversion efficiencies, lowering the cost of solar cells, modules, and systems, and improving the reliability of PV components and systems.
Driven by advances in technology and increases in manufacturing scale and sophistication, the cost of photovoltaics is declining continuously and the installed capacity of PV systems is growing exponentially. There are several million PV systems distributed all over the world, mostly in Europe, with 1.4 million systems in Germany alone as well as North America with 440,000 systems in the United States, China and Japan, the world's fastest growing regions. The energy conversion efficiency of a conventional solar module increased from 15 to 20 percent over the last 10 years and a PV system recoups the energy needed for its manufacture in about 2 years. In exceptionally irradiated locations, or when thin-film technology is used, the so-called energy payback time decreases to one year or less. Net metering and financial incentives, such as preferential feed-in tariffs for solar-generated electricity, have also greatly supported installations of PV systems in many countries. The levelised cost of electricity (LCOE) from PV systems has become competitive with conventional electricity sources in an expanding list of geographic regions, as grid parity has been achieved in many different markets.
I wish to thank you all for your answers to Axel's questions. I work in the PV area too and I have been enriched by your answers. Thank you so much.
Thanks all for the contributions, Jorge Morales Pedraza as usual with dense and intense input.
I d like to add another point - in a nutshell:
Inefficiency means heat. What if the same PV panel could transform this heat into electricity as well as the "electrons" flow.
Dear George and all,
I am aware of the combination of two technologies which is not what I meant. And obviously the o&m costs can be increased depending on the quality of the installations where heat and pressure can open other problem fields from thermosolar harvesting. In Austria for example a combination of both technologies would mean that you require for installation purposes an electrician as well as a plumber.
So the installation costs are quite higher. Not taken into consideration if the roofs can withold the added weight. Obviously in countries with temperatures below the freezing level this closed pipesystem needs to be filled with brine which increases the input energy on the circulation pump side.
I am referring to another point where the energy transport is beeing conducted with an exisiting infrastructure consisting of PV-panel - wiring - batteries where we still can use the anergetic (or entropic) components and charge them into the batteries together with the exergy.
This should push the limitations from "efficiency ratios" beyond ... and this is the exciting question.
The next effect is that it seems that we do not need direct visible light - the effect is working even at far lower levels like 200 - 500 W/m² where the regular loading procedures from PV to Batteries according to the low A levels would not be working anymore.
Certainly the efficiency of the PV drops with the heat in the system but the efficiency of the system could be improved if that heat is extracted. Converting that heat to electricity could be done using a thermoelectric module placed at the underside of the PV cell. This extracts the heat and converts it directly to electricity. However, the cost of such a system is not so wonderful when compered with the overall efficiency of the system. But using the thermoelectric module as a cooler for the PV system seems to be a better idea. I am currently working on them. I hope to confirm these assertions.
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