Hand made solar cells from chlorophyll for teaching in high school energy education (original) (raw)
Related papers
On the current generated by a galvanic cell driven by photosynthetic electron transport
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1979
Photosynthetic electron transport of isolated chloroplasts was used to convert light energy to a potential difference of a galvanic cell. A current through an external circuit of the cell requires a transfer of electrons between the endogenous electron carriers and a redox mediator, and a subsequent transfer between the mediator and the electrode in each of the joined half-cells. With 2,3,5,6-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethyl-p-phenylenediamine as mediator the second electron transfer step was found to be limiting. To increase the current through the external circuit we increased the concentration of salt and mediator as well as the surface area of the electrodes. Upon illumination the system generated a short-circuit current of up to 800 ~A at a current density of 16 ~zA/cm 2. The results are discussed with respect to the interdependence of the successive electron transfer steps and the properties of components for effective energy conversion by the cell.
Chlorophylls - natural solar cells
2011
A molecular modeling study was conducted on a series of six natural occurring chlorophylls. Quantum chemistry calculated orbital energies were used to estimate frequency of transitions between occupied molecular orbital and unoccupied molecular orbital energy levels of chlorophyll molecules in vivo conditions in standard (ASTMG173) environmental conditions. Obtained results are in good agreement with energies necessary to fix the Magnesium atom by chlorophyll molecules and with occurrence of chlorophylls in living vegetal organisms.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1974
Light induces the generation of an electrochemical potential difference across the functional membrane of photosynthesis of green plants. Experimental results on the electrochemical phenomena have been largely interpreted in terms of a vectorial alternating electron hydrogen transport system as originally hypothesized by Mitchell. We asked whether or not the reaction coordinate of the electron transport crosses the membrane, and whether or not the protolytic reactions at either side of the membrane can be understood from the protolytic properties of the redox components involved. For this we studied the flashlight induced protolytic reactions in the outer and the inner aqueous phase of the chloroplast inner disk membranes. Four sites of protolytic reactions were identified, two at either side of the membrane. One of these sites had to be attributed to the reduction of the terminal electron acceptor at the outer side of the membrane. Evidence is presented for the coupling of the other sites to the oxidation of water at the inner side of the membrane, to the reduction of plastoquinone at the outer side and its oxidation at the inner side, respectively. These results support Mitchell's hypothesis for the generation of an electrochemical potential difference by a vectorial electron transport system.
Components of Natural Photosynthetic Apparatus in Solar Cells
Applied Photosynthesis - New Progress, 2016
Oxygenic photosynthesis is a process of light energy conversion into the chemical energy using water and carbon dioxide. The efficiency of energy conversion in the primary processes of photosynthesis is close to 100%. Therefore, for many years, photosynthesis has attracted the attention of researchers as the most efficient and ecofriendly pathway of solar energy conversion for alternative energy systems. The recent advances in the design of optimal solar cells include the creation of converters, in which thylakoid membranes, photosystems and whole cells of cyanobacteria immobilized on nanostructured electrode are used. As the mechanism of solar energy conversion in photosynthesis is sustainable and environmentally safe, it has a great potential as an example of renewable energy device. Application of pigments such as Chl f and Chl d will extend the spectral diapason of light transforming systems allow to absorb the farred and near infra-red photons of the spectrum (in the range 700-750 nm). This article presents the recent achievements and challenges in the area of solar cells based on photosynthetic systems.
Education and Solar conversion
A simplified solar cell fabrication procedure is presented that uses natural anthocyanin or chlorophyll dyes extracted from plants. This procedure illustrates how interdisciplinary science can be taught at lower division university and upper division high school levels for an understanding of renewable energy as well as basic science concepts. Electron transfer occurs on the Earth in the mitochondrial membranes found in living cells, and in the thylakoid membranes found in the photosynthetic cells of green plants. Since we depend on the results of this electron and energy transfer, e.g. in our use of petroleum and agricultural products, it is desirable to understand and communicate how the electron transfer works. The simplified solar cell fabrication procedure, based on nanocrystalline dye-sensitized solar cells, has therefore been developed so that it can be inexpensively reproduced and utilized in the teaching of basic principles in biology, chemistry, physics, and environmental science. A water-based solution of commercial nanocrystalline titanium dioxide (TiO ) powder is used to deposit a highly porous semiconductor electron acceptor. This acceptor couples the light-driven processes occurring at an organic dye to the macroscopic world and an external electrical circuit. Materials science and semiconductor physics are emphasized during the deposition of the sintered TiO nanocrystalline ceramic film. Chelation, complexation and molecular self-assembly are demonstrated during the attachment of the dye molecule to the surface of the TiO semiconductor particles. Environmental chemistry and energy conversion can be linked to these concepts via the regenerative oxidation and reduction cycle found in the cell. The resulting device, made in under 3 h, can be used as a light detector or power generator that produces 0.4-0.5 V at open circuit, and 1-2 mA per square cm under solar illumination.
Behavior of Electrical Properties of Synthetic Chlorophyll Pigment Solution by using the T.E-Model
Objective: Our purpose is to propose a new method for studying the electrical activity of chlorophyll pigment solution. Methods/Statistical Analysis: The technic and method employed consisted of modeling the chlorophyll as an electrical circuit, which made up of two parallel branches; where R represents the extra chlorophyll space resistance, R' the intra chlorophyll space resistance and C the chlorophyll capacitance. Then at low frequency, measure R according to the variation of light intensity. Chlorophyll fluorescence is generally used to study chlorophyll pigment solution; but it does not directly show us the electrical activity that occurs as the proposed method. Findings: Our study has shown that electric behavior of synthetic solution of pigment depends of the solution concentration. There is a consensus between the behavior of synthetic chlorophyll and the existing behavior of natural pigments for some concentrations; for example, for 5.1 g/L and 10.2 g/L the extra-chlorophyll resistance of the synthetic pigments, just like that of the natural pigments, decreases according to the intensity of light until it reaches a certain threshold. On the other hand, for concentrations of 4.25 g/L and 2.55 g/L we observe a different electric behavior. Moreover, it is noted that for concentrations reproducing the same electric behavior as for the natural pigments, the decrease of extra chlorophyll resistance is all the more marked that the concentration is high. These results are helpful because we can directly have the electrical behavior of chlorophyll than fluorescence, where we need first to determine parameters like: primary fluorescence (F0), maximal fluorescence (Fm), variable fluorescence (Fv), the photochemical quantic yield (ΦPSII) of the photosystem II and the assimilation quantic yield of CO 2 (ΦCO 2) before having an information about the electrical behavior of chlorophyll. Application/Improvements: This method of study can be applied in phototherapy about drugs made from chlorophyll to avoid side effects of chlorophyll solution.
A Photovoltaic Device Using an Electrolyte Containing Photosynthetic Reaction Centers
Energies, 2010
The performance of bio-photovoltaic devices with a monolayer of the immobilized photosynthetic reaction center (RC) is generally low because of weak light absorption and poor charge transfer between the RC and the electrode. In this paper, a new bio-photovoltaic device is described in which the RC is dissolved in the electrolyte of an electrochemical cell. The charges generated by the illuminated RC are transferred to electrodes via mediators. The difference between the reaction rates of two types of mediator at the electrode surfaces determines the direction of the photocurrent in the device. Experimental results show that the magnitude of the photocurrent is proportional to the incident light intensity, and the current increases nonlinearly with an increase in the RC concentration in the electrolyte. With further optimization this approach should lead to devices with improved light absorption.
Stochastic Electrical Behavior of Splina Liquid Chlorophyll Drink
Objective: Our purpose is to study the stochastic electrical behavior of Splina liquid chlorophyll by using the T. E.-model and to compare it with the natural one. Methods/Statistical Analysis: The technic and method employed consisted of modeling the chlorophyll as an electrical circuit, to make a statistical analysis of the extra chlorophyll space resistance process of Splina solution in light and in darkness by evaluating, the statistical average and statistical autocorrelation function, and make a temporal analysis by evaluating, the temporal average and temporal autocorrelation function. Findings: It comes out from our study that, for a suitable lighting angle, and repartition of Splina solution component, after adding of purified water, RO-EDI (Reverse Osomosis-Electrode Ionization) water and sodium copper chlorophyll in to the natural chlorophyll, the electric behavior of Splina chlorophyll solution is like the natural one. For the three different disposition of liquid chlorophyll glass, the Spectral Density of Power (DSP) of the extra-chlorophyll space resistance process R(ω,t) when the splina solution is under light is up to the DSP of the signal when the splina solution is under darkness for the whole value of the reduced normalized frequency; the process is non-statistics in the broad sense (SSL) and non ergotic. The resemblance of the flow charge with him for different value of the shift parameter is high in light than in darkness. Application/Improvements: This study provided an additional tool to verify if after the addition of new substances, that the photoelectric, statistical and temporal behavior of the resulting product is identical to that of the initial natural one.