"For a finite-size (flow) system to persist in time (to live), its configuration must evolve such that it provides easier access to the imposed currents that flow through it."
The above is the statement of Constructal Theory, developed in 1996 by Professor Adrian Bejan.
Why is it important?
Because it describes the evolution of flow!
Flow of what?
The flow of ANYTHING! This ranges from the flow of energy, mass to the flow of heat, goods, people etc.
Let me explain the Constructal Theory to you know, in the context of thermodynamics.
The second law tell us that a system will evolve to a state of maximum entropy.
The minimum work principle tells us that to optimize a process, minimum entropy must be generated during the process.
Constructal Theory tells us that every natural flowing system will want to globally optimize itself. It accepts the imperfections in the process and tells us how the system will evolve such that these imperfections will be minimum.
It says that the maximization of the flow access= minimization of the various global resistances at the scales at which they act.
For instance if we look at a tree and see how it evolves as time, we see that it evolves such that the flow of air in its interstitial spaces (which occurs primarily due to conduction) is maximized by the minimization of the resistance by increasing the interstitial surface area. (This is why when drawing a tree the white is as important as the black)
For the flow of gases/water in the 'black' of the tree, the resistance is less as compared to the high resistance of the flow of air due to conduction, therefore the flow channel area is more. Thus we see how a tree, evolves such that the two flows that occur are maximized, by considering each of the resistances that act on the system globally, and by optimizing each resistance at the scale at which it acts.
Let me give you one more striking example, that is the flow of mass. We shall see how Constructal Theory gives us various allometric relations, already observed in Nature by approximating running, swimming and flying as the flow of mass.
There are two resisitve forces the body has to compete against. One is drag and the other is the gravitational force.
Constructal Theory says that to optimize this flow of mass, the various resistances per scale has to be minimized. That is
W1 of the object against drag/L + W2 of the object against gravitation/L has to be minimized. Or we have to minimize the work being wasted across the scales at which these 2 resistive forces act. Therefore we must minimize the work done per unit length traveled by the object.
Basically, constructal theory accepts, that when an animal ingests food, there is nothing that can be done in the input stage, or in the conversion of food to energy. however, at the output stage we can globally minimize the effects of the two resistances.
With the model given by constructal Theory, we can derive allometric relationships between the mass of the body and the velocity with which it travels according to this model. Thus Constructal Theory seems to generate various scale relationships which had been observed in various fields in various things.
Constructal theory gives us a basis to understand these relations and to actually derive such relations across various fields.
In this post I will not elaborate on further examples. I will only tell you some of the remarkable effects Constructal Theory has predicted.
It has predicted the accurate relationship between the length and width of a block in a city. It predicts the changing dimensions of streets with the faster velocities that are now attainable. It even predicts globalization as a better method for the flow of goods and services.
Lots of papers on this theory can be found on the net on this wonderful theory, and I hope that you, like me will find this theory intriguing! :)
Monday, March 22, 2010
Friday, March 5, 2010
Solar Cells Part 2
Solar cells from Blueberries:
This is essentially a dye sensitized solar cell.
To explain how this works in more detail we need to go back to Nature.
The problem with silicon solar cells is that achieving the optimum band gap is difficult. This was already explained in the last post. But wait, who am I kidding?! :P No one would have gone through that anyways. So let me explain again.
If the band gap is high, high energy photons can be captured. However, if the band gap is low, then more number of photons can be captured. There therefore must be an optimum band gap. Tandem solar cells, quantum dots are two of the ways used to capture all the wavelengths of light.
Also, in solid state devices. Silicon is used as the electron generator and an electric field is produced in it which causes charge transport. A simplistic explanation of this process is:- A photon is incident on n type Si. If it's energy is more than the band gap, it excites an electron which moves towards the bottom of the cell: p junction and then through an electrical wire to the load.
Now the problem is to prevent the recombination of the electron with a hole as it travels from the top negative junction to the bottom positive junction.
Dye sensitized cells solve the fist problem by mimicking photosynthesis. They consist of an electrolyte with two electrodes. Silicon basically acts as a charge transporter and does not generate the electron.
What happens is, a photon falls on the organic dye which excites the dye molecule to an excited state releasing an electron. This electron moves into the TiO2 and exits through the conductive layer into the electrical wires. This is how current flow occurs.
Then the electron returns to the cell via the bottom conductive layer. With the help of a catalyst (usually platinum), the electron enters the electrolyte and interacts with the tri iodide molecule. It reduces it to form an iodide ion. The iodide ion moves towards the activated dye molecule and transfers an electron to the dye. Thus the dye molecule reverts to its previous ground state and the iodide ion reverts back to tri iodide.
What happens in photosynthesis is, an electron is absorbed by a pigment. The energy of the electron is used to synthesize dihydro nicotinamide di hydrogen phosphate (NADPH), a molecule that will eventually produce carbohydrates. To get the pigment back to it's initial state, an electron is donated in the oxidation of water to produce oxygen.
The difference between the two processes is that the storage of energy in the form of starch occurs in leaves, while the storage of energy in a dye sensitized solar cell is still not possible.
The similarities of the two processes is evident. Both are regenerative cycles which involve redox reactions. They use a multi layer structure similar to a thylakoid membrane. (They are the site of the light dependent reactions in leaves)
In DYSC the organic dye replaces the pigment in Nature. The wide band gap semi conductor used replaces the oxidized NADPH and carbon dioxide as the electron acceptor. The electrolyte replaces the water and oxygen as the electron donor.
Now I will talk a little about the materials involved.
Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of light-absorbing material. The dye-sensitized solar cell depends on a mesoporous layer of nanoparticulate titanium dioxide to greatly amplify the surface area (200-300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from the light absorbing dye are passed on to the n-type TiO2, and the holes are passed to an electrolyte on the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows a more flexible use of materials, and is typically manufactured by screen printing and/or use of Ultrasonic Nozzles, with the potential for lower processing costs than those used for bulk solar cells. However, the dyes in these cells also suffer from degradation under heat and UV light, and the cell casing is difficult to seal due to the solvents used in assembly.
The absorption of incident light depends upon the number of dye molecules attached per unit volume of the semi conductor. if the dye is on a flat surface less than 1% of light will be absorbed.
Light absorption is maximized by the use of sintered nano meter size anatase (tetragonal crystal structure) titanium dioxide. The surface are is increased by 200-300%. This surface has pores in the range of 20-500Angstrom. It is advantageous to use TiO2 because it is cheap, easily available, bio compatible and non toxic. The anatase phase is used because it has a wide band gap that is transparent to visible light and thus ensures that the light is absorbed only by the dye molecules.
The thickness of the TiO2 layer is a compromise between maximum surface area and minimum recombination losses.
They dyes used by commercial dye sensitized solar cells generally use ruthenium bi pyridyl based dyes. The wavelengths of light absorbed are 510-570nm and adequate conversion between 450-650nm. This absorption spectrum overlaps well with the diffuse sunlight spectrum. However such dyes are hard to synthesize.
A little about these dyes
Ruthenium bipyridyl complexes have been used as efficient sensitizers for photoelectrochemical cells based on nano-porous films of . It is found that cis-dithiocyanate-bis(2,2-bipyridyl-4,4-dicarboxylate) ruthenium (II) can be used as the sensitizer in a solid-state photovoltaic cell in which a monolayer of the sensitizer is sandwiched between nano-porous n- and p-CuI.
A significant photo current can be obtained using natural anthocyanin dyes which can be extracted from blueberries as natural water based substitutes. The absorption of cyanin on the surface of TiO2 is a rapid reaction and the OH counter ion is displaced from the ti(4) work site that combines with a proton donated by anthocyanin. This strong chemical affinity is the reason blue berries can be used :D.
An Experiment that was conducted: (i found this paper on the net)
A commercially bought titanium dioxide coated glass slide was stained with a berry dye (e.g. raspberries, blueberries, beetroot); the dye was made by crushing the fruit (or leaves) and purifying them in a solution of methanol, acetic acid and water . This slide was washed with water, and dried with propanol, and a transparent conducting glass slide (tin dioxide coated) was secured over it using metal clips.
The electrolyte solution (0.5M potassium iodide and 0.05M iodine in ethylene glycol) was drawn up into the porous titanium dioxide structure . Raspberry, blueberry, beetroot and orange leaf cells were constructed.
All cells produced a photocurrent when a voltage was applied , but its magnitude varied between the dyes; the region of negative current and positive voltage represents photocurrent activity. It was found that blueberries were most efficient –they produced a photocurrent of 0.2mA (~0.02% efficiency) - followed by raspberries, then beetroot. The orange leaf dyed cells produced virtually no current.
Initially the blueberries, raspberries and beetroot showed improvement, whereas there was none in the orange leaf dye. There was significant improvement over the first 9 hours, before degradation began. There was improved photocurrent as the concentration of electrolyte solution was increased for raspberries, blueberries and beetroot, but not for the orange leaf cell.
It is hard to take into account factors like electrolytic degradation and the oxidation of fruit etc.However people feel that the improvement is independent of the degradation process and when this degradation process becomes the dominant process then a decrease in efficiency is noted.
The improvement process can be explained by looking at the energy levels associated with the titanium dioxide, the dye and the electrolyte solution. In the blueberry cell: the ease with which an electron moves through the system is determined by the energy barriers, or band gaps that must be overcome.
The electron must have a significant energy to transfer from the electrolyte to the dye. As the cell is exposed to the light the cell heats up, causing evaporation of the electrolyte solution. This increases the concentration of KI and I2, and the energy level of the valence band is raised, making the transfer of electrons to the dye a far more favourable process. This explains why the photocurrent improved when placed underneath the light.
The conduction band of the blueberry dye lies above that of the titanium dioxide conduction band. Hence it is energetically favourable for the electrons excited from the valence band into the conduction band of the dye to be transferred to the conduction band of the titanium dioxide.
This is not the case in the orange leaves. The conduction band of the orange leaves lies below that of tiO2.
Thus in choosing materials it is important to look at the energy considerations.
A significant short coming of the DYSC model is the leaking of the electrolyte which reduces the life time of the cell. Although we can use sold electrolytes where the dye would eject an electron into the TiO2 and a hole into the solid electrolyte the efficiency is really low due to the poor penetration of the sold into the pores of TiO2.
Currently there is research going on, on the use of polymer gel to quasi solidify the electrolyte. The addition of Poly(viny1idene fluoride co-hexafluoropropylene) to the KI/I2 electrolyte has improved the fill factors and the energy conversion efficiency of the DYSC by about 17 %.
Thus dye sensitized solar cells seem to be a viable option for the future
This is essentially a dye sensitized solar cell.
To explain how this works in more detail we need to go back to Nature.
The problem with silicon solar cells is that achieving the optimum band gap is difficult. This was already explained in the last post. But wait, who am I kidding?! :P No one would have gone through that anyways. So let me explain again.
If the band gap is high, high energy photons can be captured. However, if the band gap is low, then more number of photons can be captured. There therefore must be an optimum band gap. Tandem solar cells, quantum dots are two of the ways used to capture all the wavelengths of light.
Also, in solid state devices. Silicon is used as the electron generator and an electric field is produced in it which causes charge transport. A simplistic explanation of this process is:- A photon is incident on n type Si. If it's energy is more than the band gap, it excites an electron which moves towards the bottom of the cell: p junction and then through an electrical wire to the load.
Now the problem is to prevent the recombination of the electron with a hole as it travels from the top negative junction to the bottom positive junction.
Dye sensitized cells solve the fist problem by mimicking photosynthesis. They consist of an electrolyte with two electrodes. Silicon basically acts as a charge transporter and does not generate the electron.
What happens is, a photon falls on the organic dye which excites the dye molecule to an excited state releasing an electron. This electron moves into the TiO2 and exits through the conductive layer into the electrical wires. This is how current flow occurs.
Then the electron returns to the cell via the bottom conductive layer. With the help of a catalyst (usually platinum), the electron enters the electrolyte and interacts with the tri iodide molecule. It reduces it to form an iodide ion. The iodide ion moves towards the activated dye molecule and transfers an electron to the dye. Thus the dye molecule reverts to its previous ground state and the iodide ion reverts back to tri iodide.
What happens in photosynthesis is, an electron is absorbed by a pigment. The energy of the electron is used to synthesize dihydro nicotinamide di hydrogen phosphate (NADPH), a molecule that will eventually produce carbohydrates. To get the pigment back to it's initial state, an electron is donated in the oxidation of water to produce oxygen.
The difference between the two processes is that the storage of energy in the form of starch occurs in leaves, while the storage of energy in a dye sensitized solar cell is still not possible.
The similarities of the two processes is evident. Both are regenerative cycles which involve redox reactions. They use a multi layer structure similar to a thylakoid membrane. (They are the site of the light dependent reactions in leaves)
In DYSC the organic dye replaces the pigment in Nature. The wide band gap semi conductor used replaces the oxidized NADPH and carbon dioxide as the electron acceptor. The electrolyte replaces the water and oxygen as the electron donor.
Now I will talk a little about the materials involved.
Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of light-absorbing material. The dye-sensitized solar cell depends on a mesoporous layer of nanoparticulate titanium dioxide to greatly amplify the surface area (200-300 m2/g TiO2, as compared to approximately 10 m2/g of flat single crystal). The photogenerated electrons from the light absorbing dye are passed on to the n-type TiO2, and the holes are passed to an electrolyte on the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows a more flexible use of materials, and is typically manufactured by screen printing and/or use of Ultrasonic Nozzles, with the potential for lower processing costs than those used for bulk solar cells. However, the dyes in these cells also suffer from degradation under heat and UV light, and the cell casing is difficult to seal due to the solvents used in assembly.
The absorption of incident light depends upon the number of dye molecules attached per unit volume of the semi conductor. if the dye is on a flat surface less than 1% of light will be absorbed.
Light absorption is maximized by the use of sintered nano meter size anatase (tetragonal crystal structure) titanium dioxide. The surface are is increased by 200-300%. This surface has pores in the range of 20-500Angstrom. It is advantageous to use TiO2 because it is cheap, easily available, bio compatible and non toxic. The anatase phase is used because it has a wide band gap that is transparent to visible light and thus ensures that the light is absorbed only by the dye molecules.
The thickness of the TiO2 layer is a compromise between maximum surface area and minimum recombination losses.
They dyes used by commercial dye sensitized solar cells generally use ruthenium bi pyridyl based dyes. The wavelengths of light absorbed are 510-570nm and adequate conversion between 450-650nm. This absorption spectrum overlaps well with the diffuse sunlight spectrum. However such dyes are hard to synthesize.
A little about these dyes
Ruthenium bipyridyl complexes have been used as efficient sensitizers for photoelectrochemical cells based on nano-porous films of . It is found that cis-dithiocyanate-bis(2,2-bipyridyl-4,4-dicarboxylate) ruthenium (II) can be used as the sensitizer in a solid-state photovoltaic cell in which a monolayer of the sensitizer is sandwiched between nano-porous n- and p-CuI.
A significant photo current can be obtained using natural anthocyanin dyes which can be extracted from blueberries as natural water based substitutes. The absorption of cyanin on the surface of TiO2 is a rapid reaction and the OH counter ion is displaced from the ti(4) work site that combines with a proton donated by anthocyanin. This strong chemical affinity is the reason blue berries can be used :D.
An Experiment that was conducted: (i found this paper on the net)
A commercially bought titanium dioxide coated glass slide was stained with a berry dye (e.g. raspberries, blueberries, beetroot); the dye was made by crushing the fruit (or leaves) and purifying them in a solution of methanol, acetic acid and water . This slide was washed with water, and dried with propanol, and a transparent conducting glass slide (tin dioxide coated) was secured over it using metal clips.
The electrolyte solution (0.5M potassium iodide and 0.05M iodine in ethylene glycol) was drawn up into the porous titanium dioxide structure . Raspberry, blueberry, beetroot and orange leaf cells were constructed.
All cells produced a photocurrent when a voltage was applied , but its magnitude varied between the dyes; the region of negative current and positive voltage represents photocurrent activity. It was found that blueberries were most efficient –they produced a photocurrent of 0.2mA (~0.02% efficiency) - followed by raspberries, then beetroot. The orange leaf dyed cells produced virtually no current.
Initially the blueberries, raspberries and beetroot showed improvement, whereas there was none in the orange leaf dye. There was significant improvement over the first 9 hours, before degradation began. There was improved photocurrent as the concentration of electrolyte solution was increased for raspberries, blueberries and beetroot, but not for the orange leaf cell.
It is hard to take into account factors like electrolytic degradation and the oxidation of fruit etc.However people feel that the improvement is independent of the degradation process and when this degradation process becomes the dominant process then a decrease in efficiency is noted.
The improvement process can be explained by looking at the energy levels associated with the titanium dioxide, the dye and the electrolyte solution. In the blueberry cell: the ease with which an electron moves through the system is determined by the energy barriers, or band gaps that must be overcome.
The electron must have a significant energy to transfer from the electrolyte to the dye. As the cell is exposed to the light the cell heats up, causing evaporation of the electrolyte solution. This increases the concentration of KI and I2, and the energy level of the valence band is raised, making the transfer of electrons to the dye a far more favourable process. This explains why the photocurrent improved when placed underneath the light.
The conduction band of the blueberry dye lies above that of the titanium dioxide conduction band. Hence it is energetically favourable for the electrons excited from the valence band into the conduction band of the dye to be transferred to the conduction band of the titanium dioxide.
This is not the case in the orange leaves. The conduction band of the orange leaves lies below that of tiO2.
Thus in choosing materials it is important to look at the energy considerations.
A significant short coming of the DYSC model is the leaking of the electrolyte which reduces the life time of the cell. Although we can use sold electrolytes where the dye would eject an electron into the TiO2 and a hole into the solid electrolyte the efficiency is really low due to the poor penetration of the sold into the pores of TiO2.
Currently there is research going on, on the use of polymer gel to quasi solidify the electrolyte. The addition of Poly(viny1idene fluoride co-hexafluoropropylene) to the KI/I2 electrolyte has improved the fill factors and the energy conversion efficiency of the DYSC by about 17 %.
Thus dye sensitized solar cells seem to be a viable option for the future
Solar Cells Part 1
OK, so here's the thing, I'm taking part in Padarth, which is the material science fest of IITB in the exposition on materials. My topic is 'Whacky Solar Cells'. The exposition happens to be tomorrow and I'm really nervous. So I'm going to lay down the structure of my talk here.
This post will just have the history of solar cells and the different types.
I have taken most of this post from an article I wrote along with 2 seniors on Solar cells. This article has already appeared in the Meta department's magazine/newsletter.
History of Solar Cells:
Photovolataic devices have become a buzzword now in the times of energy crisis but the history of photovoltaics dates more than 160 years back. The phenomenon of photoconductivity was first discovered in 1839 by a nineteen years old French experimental physicist, Alexandre Edmond Becquerel, who was experimenting with selenium electrodes to be used as high resistance rods for use in submarine applications. He observed that the conductivity of the rods increased with illumination.
In 1873, Willoughby Smith discovered photovoltaic effect in selenium. Later, in 1876, R.E. Day and William G. Adam found that illuminating a junction between selenium and platinum also has a photovoltaic effect. These discoveries led to the construction of the first solar cell based on selenium and gold junction in 1877, which was described in detail by Charles Fritts, an American scientist, in 1883. In 1888, Edward Weston received the first US patent for "solar cell" and later, in 1901, Nikola Tesla received a US patent for "method of utilizing, and apparatus for the utilization of, radiant energy".
From 1900-1949, scientists tried to find the theoretical explanation of Photovoltaic effect and first functional solar cells were made. In 1904, Albert Einstein published a paper explaining the effect, for which he was awarded the Nobel Prize in 1921. Einstein's theoretical explanation was experimentally proved by Robert Millikan in 1916. In 1914, the existence of a barrier layer in PV devices was reported.
The start of silicon based solar cells and devices can be attributed to the discovery of a method of preparing monocrystalline silicon by Jan Czochralski in 1918. The first monocrystalline silicon solar cell was made in 1941 by Russel Ohl.
Solar cell research got a big boast during 1950-1970 due to extensive interest in space research. In early 1950s, extensive laboratory research on solar cells took place. In 1951, the first germanium solar cells were made. In 1954, Rappaport, Loferski and Jenny of the RCA Laboratories published a report on photovoltaic effect in CdS.
In the same year, Bell Labs researchers Pearson, Chapin, and Fuller reported an efficiency of 4.5% in silicon solar cells; this was raised to 6% only a few months later. By the year 1955, the energy cost for PV devices was US$ 1,785 per W and the maximum efficiency achieved out of a device was 2%. By 1960, the efficiency of commercially available solar cells had touched 14%.
The energy crisis and oil embargoes of 1970s increased the interest in renewable sources of energy and development of photovoltaics got a big boast. Large photovoltaic corporations were set up around the world during this time, like the Solar Power Corporation in 1972, the Solarex Corporation in 1973 Solec International and Solar Technology International in 1975. In 1974, Japan formulated “Project Sunshine” to fuel PV research and development. By this time, a silicon solar cell of US$ 30 per W had been produced. This opened up the possibility of using solar cells in small day-to-day applications like pocket calculators, watches, radios, lanterns and other small battery-charging applications. The Solar Energy Research Institute (SERI), later to become the National Renewable Energy Laboratory (NREL), opened in Golden, Colorado in 1977. Total PV manufacturing production exceeded 500 kW by that year.
In 1984, the fist amorphous silicon solar cell was made and in 1986, ARCO Solar introduced the first commercial thin film photovoltaic module. By then University of New South Wales, Australia had made a solar cell with efficiency of 20%. In 1989, a concentrator solar cell was developed in which sunlight is concentrated onto the cell surface by means of lenses. This system achieved an efficiency of 37% due to the increased intensity of the collected energy. New thin film deposition techniques were perfected in 21st century, leading to the development of more efficient and cost-effective novel designs solar cells like amorphous silicon solar cells, organic solar cells and quantum dot solar cells. Recently, a research group at Fraunhofer Institute for Solar Energy Systems ISE, Germany, reported a whopping efficiency of 41% with tandem solar cells. Hopefully, that day is not far when solar cells will become the ultimate energy source with cheap solar panel installations on each and every household in the world!
Novel Types of Solar Cells:-
1. Quantum Dot Solar Cells
Quantum Dots are semiconductor nano crystals composed of periodic groups of II-VI, III-V, or IV-VI materials that exhibit size and compositionally tunable band gaps. This is because the size of such a semiconductor crystal is so small that it approaches the size of the material's Exciton Bohr Radius (An exciton bohr radius is the distance in an electron-hole pair) and the electron energy levels can no longer be treated as continuousi.e that there is a small and finite separation between energy levels. The absorptive and emissive behavior of a quantum dot depends strongly on its size.
The greater the bandgap of a solar cell semiconductor, the more energetic the photons absorbed, and the greater the output voltage. On the other hand, a lower bandgap results in the capture of more photons including those in the red end of the solar spectrum, resulting in a higher output of current but at a lower output voltage.
Thus, there is an optimum bandgap that corresponds to the highest possible solar-electric energy conversion, and this can also be achieved by using a mixture of quantum dots of different sizes for harvesting the maximum proportion of the incident light. Another advantage of quantum dots is they can easily be molded in convenient shapes by combining with organic polymers, dyes, or made into porous films on substrates of various materials like glass, plastics and metal sheets.
2. Organic solar cells
Organic solar cells emerged in the late 1970s, based on conjugated polymers – polymers with alternating double and single carbon-carbon bonds – when it was discovered that doping these materials – i.e. slightly contaminating with appropriate chemical elements - increased conductivity several orders of magnitude . Since then these materials have found applications in the making of solar cells.
Organic photovoltaic solar cells bear an important potential of development in the search for low-cost modules for the production of domestic electricity. One of the main differences between inorganic and organic solar cells is that photo-excitation in these materials does not automatically lead to the generation of free charge carriers, but to bind electron–hole pairs (exciton) with a binding energy of about 0.4 eV.
One of the biggest obstacles to organic solar cells is that it is difficult to control what happens after light is absorbed: whether the desired property is transmitting energy, storing information or emitting light. Experiments, however suggests it is possible to achieve control using quantum effects, even under relatively normal conditions. Organic solar cells — made out of plastic-like polymers — are much cheaper when compared by the conventional inorganic, silicon and metal-based solar cells typically favored by the solar industry. They are also flexible and are very light. Their one main disadvantage, of course, is their relatively low efficiency of just 5.4% as compared to the 20 - 40% efficiencies regularly attained by inorganic crystalline solar cells.
3. Dye sensitized solar cells
A dye sensitized solar cell is a relatively new class of thin film, low-cost solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte which functions like a photochemical system. They are also known as Grätzel cells after their inventor.
Dye-sensitized solar cells separate the two functions provided by silicon in a traditional cell design. Normally the silicon acts as both the source of photoelectrons, as well as providing the electric field to separate the charges and create a current. In the dye-sensitized solar cell, the bulk of the semiconductor is used solely for charge transport, the photoelectrons are provided from a separate photosensitive dye.
Charge separation occurs at the surfaces between the dye, semiconductor and electrolyte. In quantum efficiency (the chance that one photon (of a particular energy) will create one electron) terms, these cells are extremely efficient. Due to their "depth" in the nanostructure there is a very high chance that a photon will be absorbed, and the dyes are very effective at converting them to electrons. DSSc's are currently the most efficient third-generation solar technology available.
4. Tandem solar cells
Multijunction photovoltaic cells are a sub-class of solar cells developed for higher efficiency. These multijunction cells consist of multiple thin films. Each type of semiconductor will have a characteristic band gap energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum. The semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible.
Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge pn junctions, are seeing demand rapidly rise as we can see reflected in the irse in cost of gallium and germanium. These solar cells are currently being utilized in the Mars rover missions. Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time World Solar challenge winners Nuna in 2005 and 2007, and also by the Dutch solar cars Solutra (2005) and Twente One (2007).A Dutch university set the record for thin film solar cell effiency using a single junction GaAs to 25.8% in August 2008 using only 4 µm thick GaAs layer which can be transferred from a wafer base to glass or plastic film.
My next post will cover my topic in more detail which is -Solar Cells from Blueberries
This post will just have the history of solar cells and the different types.
I have taken most of this post from an article I wrote along with 2 seniors on Solar cells. This article has already appeared in the Meta department's magazine/newsletter.
History of Solar Cells:
Photovolataic devices have become a buzzword now in the times of energy crisis but the history of photovoltaics dates more than 160 years back. The phenomenon of photoconductivity was first discovered in 1839 by a nineteen years old French experimental physicist, Alexandre Edmond Becquerel, who was experimenting with selenium electrodes to be used as high resistance rods for use in submarine applications. He observed that the conductivity of the rods increased with illumination.
In 1873, Willoughby Smith discovered photovoltaic effect in selenium. Later, in 1876, R.E. Day and William G. Adam found that illuminating a junction between selenium and platinum also has a photovoltaic effect. These discoveries led to the construction of the first solar cell based on selenium and gold junction in 1877, which was described in detail by Charles Fritts, an American scientist, in 1883. In 1888, Edward Weston received the first US patent for "solar cell" and later, in 1901, Nikola Tesla received a US patent for "method of utilizing, and apparatus for the utilization of, radiant energy".
From 1900-1949, scientists tried to find the theoretical explanation of Photovoltaic effect and first functional solar cells were made. In 1904, Albert Einstein published a paper explaining the effect, for which he was awarded the Nobel Prize in 1921. Einstein's theoretical explanation was experimentally proved by Robert Millikan in 1916. In 1914, the existence of a barrier layer in PV devices was reported.
The start of silicon based solar cells and devices can be attributed to the discovery of a method of preparing monocrystalline silicon by Jan Czochralski in 1918. The first monocrystalline silicon solar cell was made in 1941 by Russel Ohl.
Solar cell research got a big boast during 1950-1970 due to extensive interest in space research. In early 1950s, extensive laboratory research on solar cells took place. In 1951, the first germanium solar cells were made. In 1954, Rappaport, Loferski and Jenny of the RCA Laboratories published a report on photovoltaic effect in CdS.
In the same year, Bell Labs researchers Pearson, Chapin, and Fuller reported an efficiency of 4.5% in silicon solar cells; this was raised to 6% only a few months later. By the year 1955, the energy cost for PV devices was US$ 1,785 per W and the maximum efficiency achieved out of a device was 2%. By 1960, the efficiency of commercially available solar cells had touched 14%.
The energy crisis and oil embargoes of 1970s increased the interest in renewable sources of energy and development of photovoltaics got a big boast. Large photovoltaic corporations were set up around the world during this time, like the Solar Power Corporation in 1972, the Solarex Corporation in 1973 Solec International and Solar Technology International in 1975. In 1974, Japan formulated “Project Sunshine” to fuel PV research and development. By this time, a silicon solar cell of US$ 30 per W had been produced. This opened up the possibility of using solar cells in small day-to-day applications like pocket calculators, watches, radios, lanterns and other small battery-charging applications. The Solar Energy Research Institute (SERI), later to become the National Renewable Energy Laboratory (NREL), opened in Golden, Colorado in 1977. Total PV manufacturing production exceeded 500 kW by that year.
In 1984, the fist amorphous silicon solar cell was made and in 1986, ARCO Solar introduced the first commercial thin film photovoltaic module. By then University of New South Wales, Australia had made a solar cell with efficiency of 20%. In 1989, a concentrator solar cell was developed in which sunlight is concentrated onto the cell surface by means of lenses. This system achieved an efficiency of 37% due to the increased intensity of the collected energy. New thin film deposition techniques were perfected in 21st century, leading to the development of more efficient and cost-effective novel designs solar cells like amorphous silicon solar cells, organic solar cells and quantum dot solar cells. Recently, a research group at Fraunhofer Institute for Solar Energy Systems ISE, Germany, reported a whopping efficiency of 41% with tandem solar cells. Hopefully, that day is not far when solar cells will become the ultimate energy source with cheap solar panel installations on each and every household in the world!
Novel Types of Solar Cells:-
1. Quantum Dot Solar Cells
Quantum Dots are semiconductor nano crystals composed of periodic groups of II-VI, III-V, or IV-VI materials that exhibit size and compositionally tunable band gaps. This is because the size of such a semiconductor crystal is so small that it approaches the size of the material's Exciton Bohr Radius (An exciton bohr radius is the distance in an electron-hole pair) and the electron energy levels can no longer be treated as continuousi.e that there is a small and finite separation between energy levels. The absorptive and emissive behavior of a quantum dot depends strongly on its size.
The greater the bandgap of a solar cell semiconductor, the more energetic the photons absorbed, and the greater the output voltage. On the other hand, a lower bandgap results in the capture of more photons including those in the red end of the solar spectrum, resulting in a higher output of current but at a lower output voltage.
Thus, there is an optimum bandgap that corresponds to the highest possible solar-electric energy conversion, and this can also be achieved by using a mixture of quantum dots of different sizes for harvesting the maximum proportion of the incident light. Another advantage of quantum dots is they can easily be molded in convenient shapes by combining with organic polymers, dyes, or made into porous films on substrates of various materials like glass, plastics and metal sheets.
2. Organic solar cells
Organic solar cells emerged in the late 1970s, based on conjugated polymers – polymers with alternating double and single carbon-carbon bonds – when it was discovered that doping these materials – i.e. slightly contaminating with appropriate chemical elements - increased conductivity several orders of magnitude . Since then these materials have found applications in the making of solar cells.
Organic photovoltaic solar cells bear an important potential of development in the search for low-cost modules for the production of domestic electricity. One of the main differences between inorganic and organic solar cells is that photo-excitation in these materials does not automatically lead to the generation of free charge carriers, but to bind electron–hole pairs (exciton) with a binding energy of about 0.4 eV.
One of the biggest obstacles to organic solar cells is that it is difficult to control what happens after light is absorbed: whether the desired property is transmitting energy, storing information or emitting light. Experiments, however suggests it is possible to achieve control using quantum effects, even under relatively normal conditions. Organic solar cells — made out of plastic-like polymers — are much cheaper when compared by the conventional inorganic, silicon and metal-based solar cells typically favored by the solar industry. They are also flexible and are very light. Their one main disadvantage, of course, is their relatively low efficiency of just 5.4% as compared to the 20 - 40% efficiencies regularly attained by inorganic crystalline solar cells.
3. Dye sensitized solar cells
A dye sensitized solar cell is a relatively new class of thin film, low-cost solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte which functions like a photochemical system. They are also known as Grätzel cells after their inventor.
Dye-sensitized solar cells separate the two functions provided by silicon in a traditional cell design. Normally the silicon acts as both the source of photoelectrons, as well as providing the electric field to separate the charges and create a current. In the dye-sensitized solar cell, the bulk of the semiconductor is used solely for charge transport, the photoelectrons are provided from a separate photosensitive dye.
Charge separation occurs at the surfaces between the dye, semiconductor and electrolyte. In quantum efficiency (the chance that one photon (of a particular energy) will create one electron) terms, these cells are extremely efficient. Due to their "depth" in the nanostructure there is a very high chance that a photon will be absorbed, and the dyes are very effective at converting them to electrons. DSSc's are currently the most efficient third-generation solar technology available.
4. Tandem solar cells
Multijunction photovoltaic cells are a sub-class of solar cells developed for higher efficiency. These multijunction cells consist of multiple thin films. Each type of semiconductor will have a characteristic band gap energy which, loosely speaking, causes it to absorb light most efficiently at a certain color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum. The semiconductors are carefully chosen to absorb nearly all of the solar spectrum, thus generating electricity from as much of the solar energy as possible.
Tandem solar cells based on monolithic, series connected, gallium indium phosphide (GaInP), gallium arsenide GaAs, and germanium Ge pn junctions, are seeing demand rapidly rise as we can see reflected in the irse in cost of gallium and germanium. These solar cells are currently being utilized in the Mars rover missions. Triple-junction GaAs solar cells were also being used as the power source of the Dutch four-time World Solar challenge winners Nuna in 2005 and 2007, and also by the Dutch solar cars Solutra (2005) and Twente One (2007).A Dutch university set the record for thin film solar cell effiency using a single junction GaAs to 25.8% in August 2008 using only 4 µm thick GaAs layer which can be transferred from a wafer base to glass or plastic film.
My next post will cover my topic in more detail which is -Solar Cells from Blueberries
Thursday, February 25, 2010
Chocolates, Soap and Life in general
Class got over and as usual my mind was in utter turmoil! I kept on wondering whether it would be worth it! In old Shakespeare's words the question was still, "To be or Not To Be."
Though unlike Hamlet's case, the issue at hand was not really the 'apprehend-my-father's-murderer-IF-it-indeed-was-a-murder', but
whether i should Be at the candy store in the next five minutes or not. :P
The funny thing about memories is that you can never really catch one and bottle it up forever. Perhaps you'll remember an incident, but you'll never feel the same way as when the thing was really happening. You can never truly feel the same thousands of sensory impulses that raced down your spine at THAT time.
Now that is a good thing most of the time. I can tell you at least ten incidents i would never want to recall right off the cuff (yeah, but i won't!..well not right now at least :P)
But the thing is, when I try and relive the last time I ate a delicious hunk of dark chocolate, I sort of feel the same DEEP emotions. But it's never quite the same as actually being there. My memory is a sort of shadow of the actual thing. And that makes it all the more tantalizing!
So as I sat in my seat, wondering whether I should Be or Not To Be, I recalled the last time I had opened that absolutely fabulous Dairy Milk Crackle (it's my all time favorite!). And all at once, the decision was really easy. Just as easy as the fact that Vixen, Vikings and Vegetarians are all party to a secret Vendetta to overthrow the Broccoli King. (I was just kidding! i LOVE broccoli)
Anyways, I had made up my mind. I was going to buy chocolate. :D
As I entered the big general store and started looking around for 'My Chocolate of the Day' (and i'm not talking about the fb quiz)i realized that each candy bar is such a teeny weeny thing! I mean what on earth was I thinking! there was no way anyone could ever get fat by eating such a tiny piece of chocolate. It weighed far less than all of those brinjal things my mom makes me eat. And hadn't my mom heard of mass balance? You couldn't possibly gain more weight than the food you ate! A simple conservation law!
What on earth were all those dieticians, trying to reduce the fat content and all the good things in food, when all they really had to worry about was the WEIGHT of the food stuff itself! Why is that so difficult?
And why on earth do people who want to lose weight eat a big fat pumpkin instead of a tiny bar of chocolate for gods sake!
I was becoming more and more red in the face as the simplicity of things became more apparent as well as the false duplicity all those food guys were hiding behind! x-( I decided to pick up a cadbury fruit and nut and head over to the counter to pay for it.
There was a rather long line of people waiting at the counter to pay for whatever they had picked up. Just in front of me were two guys. One of them was holding a dove soap in his hand and talking about how good Dove was and how it DEFINITELY trumped Lux. I listened to the argument with amusement. I sort of felt really bad for guys in general.
Not only can they not wear things like earrings and stuff(which make life worth living <3)BUT, if you think about it, all the soap advertisements that come on TV, all have these beautiful women running around trees with water droplets glistening on their skin and talking about how whatever soap they were advertising for, worked wonders on them, made their skin soft and radiant and got all the guys after them!
I mean why on earth would a heterosexual guy want guys after him? (I know this smacks of heteronormativity, but lets play along, yeah? Edit: 1/9/2013. I am indeed much older and wiser)
And if you actually think about it, those advertisement guys were then really targeting women. They obviously wanted to send a message to all their women purchasers saying that you could be like this if you just used our soap! They obviously then assume that it is the women who buy the soap in the family and obviously assume that it is the women who get the choice of soap in the family or else why would they target their women purchasers through their advertisements. Does this mean, that they also assume that women have nothing better to do with their time, and hence have more time to buy soap than men?
This is only because, in India, women still do not have as good opportunities as men in most things. Thus as soon as soap adverts change from beautiful women running around trees to handsome men doing the same, can we really say that women are being given the same level of education as men etc etc?
:P
Anyways, I paid my bill and left. Musing and sighing about chocolates, soap and life.It's a funny world!
Though unlike Hamlet's case, the issue at hand was not really the 'apprehend-my-father's-murderer-IF-it-indeed-was-a-murder', but
whether i should Be at the candy store in the next five minutes or not. :P
The funny thing about memories is that you can never really catch one and bottle it up forever. Perhaps you'll remember an incident, but you'll never feel the same way as when the thing was really happening. You can never truly feel the same thousands of sensory impulses that raced down your spine at THAT time.
Now that is a good thing most of the time. I can tell you at least ten incidents i would never want to recall right off the cuff (yeah, but i won't!..well not right now at least :P)
But the thing is, when I try and relive the last time I ate a delicious hunk of dark chocolate, I sort of feel the same DEEP emotions. But it's never quite the same as actually being there. My memory is a sort of shadow of the actual thing. And that makes it all the more tantalizing!
So as I sat in my seat, wondering whether I should Be or Not To Be, I recalled the last time I had opened that absolutely fabulous Dairy Milk Crackle (it's my all time favorite!). And all at once, the decision was really easy. Just as easy as the fact that Vixen, Vikings and Vegetarians are all party to a secret Vendetta to overthrow the Broccoli King. (I was just kidding! i LOVE broccoli)
Anyways, I had made up my mind. I was going to buy chocolate. :D
As I entered the big general store and started looking around for 'My Chocolate of the Day' (and i'm not talking about the fb quiz)i realized that each candy bar is such a teeny weeny thing! I mean what on earth was I thinking! there was no way anyone could ever get fat by eating such a tiny piece of chocolate. It weighed far less than all of those brinjal things my mom makes me eat. And hadn't my mom heard of mass balance? You couldn't possibly gain more weight than the food you ate! A simple conservation law!
What on earth were all those dieticians, trying to reduce the fat content and all the good things in food, when all they really had to worry about was the WEIGHT of the food stuff itself! Why is that so difficult?
And why on earth do people who want to lose weight eat a big fat pumpkin instead of a tiny bar of chocolate for gods sake!
I was becoming more and more red in the face as the simplicity of things became more apparent as well as the false duplicity all those food guys were hiding behind! x-( I decided to pick up a cadbury fruit and nut and head over to the counter to pay for it.
There was a rather long line of people waiting at the counter to pay for whatever they had picked up. Just in front of me were two guys. One of them was holding a dove soap in his hand and talking about how good Dove was and how it DEFINITELY trumped Lux. I listened to the argument with amusement. I sort of felt really bad for guys in general.
Not only can they not wear things like earrings and stuff(which make life worth living <3)BUT, if you think about it, all the soap advertisements that come on TV, all have these beautiful women running around trees with water droplets glistening on their skin and talking about how whatever soap they were advertising for, worked wonders on them, made their skin soft and radiant and got all the guys after them!
I mean why on earth would a heterosexual guy want guys after him? (I know this smacks of heteronormativity, but lets play along, yeah? Edit: 1/9/2013. I am indeed much older and wiser)
And if you actually think about it, those advertisement guys were then really targeting women. They obviously wanted to send a message to all their women purchasers saying that you could be like this if you just used our soap! They obviously then assume that it is the women who buy the soap in the family and obviously assume that it is the women who get the choice of soap in the family or else why would they target their women purchasers through their advertisements. Does this mean, that they also assume that women have nothing better to do with their time, and hence have more time to buy soap than men?
This is only because, in India, women still do not have as good opportunities as men in most things. Thus as soon as soap adverts change from beautiful women running around trees to handsome men doing the same, can we really say that women are being given the same level of education as men etc etc?
:P
Anyways, I paid my bill and left. Musing and sighing about chocolates, soap and life.It's a funny world!
Monday, February 22, 2010
i'm-really-bad-at-thinking-of-titles
OK, I finally know what my goddam problem is with everything.
I've just finished reading 'The Catcher in the Rye'. Now, with most books, when you reach the end, well you know you've reached the end. You sort of see fireworks and neon signs saying, 'THE END' loud and clear, with a glowing red sunset in the background.
But when I finished this book, I had this really empty feeling in me. Like I had missed out on the point of the book. That I had not really got a word of what the writer was trying to tell me.
And then today I suddenly got into one of my 'moods', and sort of understood something. I understood the difference between characters in a play and people.
The difference is that we don't have goddam ideals!!
We're so caught up in our stupid, petty lives. We're so intent on getting enmeshed in those short term things, the things that directly affect us like getting a good job, a car, a house, in getting 'settled' that we lose the larger picture entirely! We let go off our ideals! We let go of who we can be, and take the more comfortable road. We kid ourselves by saying, "hey, this is the REAL world." Or, "Let's be practical."
We become trapped in this web of fear. We force on ourselves a list of rules and regulations, telling ourselves that the end justifies the means, until we become too goddam 'man of the world' to really go back to being that kid who used to watch disney movies, dreaming about becoming someone strong and true and basically someone who understood that life isn't a full time pain in the neck, but a soaring gift, snatched from eternity.
And that's exactly what the catcher in the rye told me. He wanted to prevent those little kids from falling off the edge into the world of adults with jobs and important things. He was shielding their dreams. He was preventing them from losing faith in their ideals by coming in contact with the world.
Once you lose yourself in the flow, there is no coming back.
OK. The reason I'm writing this, is not to say, "hey! Look at me! I'm an idealist" or "hey you goddam practical, real people, you suck!" That would be wrong, because firstly, people in glass houses are pretty vulnerable. Secondly, I guess that you can't survive on dreams. Dreams ain't manna from the sky. All i'm saying is, that if you have to make an important decision, please don't do it because hey! everybody else thinks its cool. Make it because you want to make it, alright?
I've just finished reading 'The Catcher in the Rye'. Now, with most books, when you reach the end, well you know you've reached the end. You sort of see fireworks and neon signs saying, 'THE END' loud and clear, with a glowing red sunset in the background.
But when I finished this book, I had this really empty feeling in me. Like I had missed out on the point of the book. That I had not really got a word of what the writer was trying to tell me.
And then today I suddenly got into one of my 'moods', and sort of understood something. I understood the difference between characters in a play and people.
The difference is that we don't have goddam ideals!!
We're so caught up in our stupid, petty lives. We're so intent on getting enmeshed in those short term things, the things that directly affect us like getting a good job, a car, a house, in getting 'settled' that we lose the larger picture entirely! We let go off our ideals! We let go of who we can be, and take the more comfortable road. We kid ourselves by saying, "hey, this is the REAL world." Or, "Let's be practical."
We become trapped in this web of fear. We force on ourselves a list of rules and regulations, telling ourselves that the end justifies the means, until we become too goddam 'man of the world' to really go back to being that kid who used to watch disney movies, dreaming about becoming someone strong and true and basically someone who understood that life isn't a full time pain in the neck, but a soaring gift, snatched from eternity.
And that's exactly what the catcher in the rye told me. He wanted to prevent those little kids from falling off the edge into the world of adults with jobs and important things. He was shielding their dreams. He was preventing them from losing faith in their ideals by coming in contact with the world.
Once you lose yourself in the flow, there is no coming back.
OK. The reason I'm writing this, is not to say, "hey! Look at me! I'm an idealist" or "hey you goddam practical, real people, you suck!" That would be wrong, because firstly, people in glass houses are pretty vulnerable. Secondly, I guess that you can't survive on dreams. Dreams ain't manna from the sky. All i'm saying is, that if you have to make an important decision, please don't do it because hey! everybody else thinks its cool. Make it because you want to make it, alright?
Monday, January 11, 2010
The Razor's Edge
I've just finished re-reading my favorite book, 'The Razor's Edge' by Somerset Maugham.
There are some books which leave an elusive, exotic fragrance behind ,after you regretfully turn over the last page. It is better not to discuss the enchanting secret that you were granted a glimpse of while reading that book with anyone.
It is much, much better to lie in a grassy meadow and dream instead trying to explain away the magic.
However, Somerset Maugham lies in a different class altogether. He tells you things that you've always known but never knew you knew. And the magic of his stories only increases as you think about and discuss them.
The gem of all his books is, 'The Razor's Edge'.
The book follows Larry Darrell's quest for Meaning.
Larry is a young American guy. There's nothing particularly extraordinary about him. He served in the war and it was then that he realized the futility of our lives as we jump from one goal to another, completely forgetting the larger scheme of things.
We study hard to get a job. We work to earn. We work to make our country progress and become prosperous. We work because it is the right thing to do.
But what is right? This life is so short. Eternity lies before us. Is it not better to try and understand, to try and think, instead of just doing because society deems something to be right and proper?
Is it not better to focus on ourselves and our relationship with that Eternity?
Maugham, without being pedantic at all, draws these questions to light.
The only problem is, he does not provide us with the answers.
We know that our lives would be peaceful and happy if we could actually pluck up the courage to give up our material position in the world and try to search for Meaning. But we also know that we'd be fools to do it.
Larry is the main character in the book, but there is another character who intrigues me. Her name is Sophie. Sophie is a young charming American friend of Larry's. She was happily married to a poor lawyer. They were very deeply in love. But Sophie's life falls apart when her husband and baby die in a car crash.
Sophie then wallows in drink and debauchery and drugs. She throws herself into sin to forget her grief. Her old friends cast her off.
I wonder. Suppose today, someone loses their family, we would all say how brave and stoic they are, as they shoulder their loss and gradually slip back into their old ways after the expected mourning period. They will start coming back for various luncheons and dinners and we will applaud their ability to bear hardship.
But Sophie's grief is so much more touching. Society condemns her, but perhaps she is closer to the Infinity than any of us. Her love scourges her of any true wickedness. No reader of the 'Razor's Edge', can ever call Sophie wicked. Weak, yes, but evil, no.
"The sharp edge of a razor is difficult to pass over; thus the wise say the path to Salvation is hard."
There are some books which leave an elusive, exotic fragrance behind ,after you regretfully turn over the last page. It is better not to discuss the enchanting secret that you were granted a glimpse of while reading that book with anyone.
It is much, much better to lie in a grassy meadow and dream instead trying to explain away the magic.
However, Somerset Maugham lies in a different class altogether. He tells you things that you've always known but never knew you knew. And the magic of his stories only increases as you think about and discuss them.
The gem of all his books is, 'The Razor's Edge'.
The book follows Larry Darrell's quest for Meaning.
Larry is a young American guy. There's nothing particularly extraordinary about him. He served in the war and it was then that he realized the futility of our lives as we jump from one goal to another, completely forgetting the larger scheme of things.
We study hard to get a job. We work to earn. We work to make our country progress and become prosperous. We work because it is the right thing to do.
But what is right? This life is so short. Eternity lies before us. Is it not better to try and understand, to try and think, instead of just doing because society deems something to be right and proper?
Is it not better to focus on ourselves and our relationship with that Eternity?
Maugham, without being pedantic at all, draws these questions to light.
The only problem is, he does not provide us with the answers.
We know that our lives would be peaceful and happy if we could actually pluck up the courage to give up our material position in the world and try to search for Meaning. But we also know that we'd be fools to do it.
Larry is the main character in the book, but there is another character who intrigues me. Her name is Sophie. Sophie is a young charming American friend of Larry's. She was happily married to a poor lawyer. They were very deeply in love. But Sophie's life falls apart when her husband and baby die in a car crash.
Sophie then wallows in drink and debauchery and drugs. She throws herself into sin to forget her grief. Her old friends cast her off.
I wonder. Suppose today, someone loses their family, we would all say how brave and stoic they are, as they shoulder their loss and gradually slip back into their old ways after the expected mourning period. They will start coming back for various luncheons and dinners and we will applaud their ability to bear hardship.
But Sophie's grief is so much more touching. Society condemns her, but perhaps she is closer to the Infinity than any of us. Her love scourges her of any true wickedness. No reader of the 'Razor's Edge', can ever call Sophie wicked. Weak, yes, but evil, no.
"The sharp edge of a razor is difficult to pass over; thus the wise say the path to Salvation is hard."
Wednesday, January 6, 2010
Reflections
The History of Science is strewn with revolutions, revelations and violent brain storms. Today it seems so intuitive that the earth rotates on it's own axis and revolves around the sun. But for hundreds of years the view that the sun revolves around the earth was upheld.
Why is it that people thought so?
Well, you might say because it looks as if the sun is revolving around the earth!
Oh? Well what would it have looked like had the earth rotated about it's own axis instead!?!
So, then why was this thought was introduced so late?
We humans tread in our 'middle sized' world. Our intuitions and faculties are developed so that we can navigate this 'middle earth' :P. Our brains are designed to process what we perceive in a certain way. Does that mean that however superior a brain is, there are certain ideas that it will never be able to grasp?
I have read that rocks, especially crystals, have a lot of tiny open spaces inside them. But to us, when we hold a crystal in our hand, it seems massive and 'solid'. But neutrinos would perceive these rocks differently. They see these same rocks as full of massive spaces filled with air molecules.
Thus, the scope of our perceptions and ideas seem to have a limit. Will this affect our understanding of topics like quantum physics? (As this is on a totally different scale)
Will concepts like wave and particle duality be forever beyond our understanding? Will we ever get the 'feel' of such topics? Are we limited by our perceptions?
I really wonder. . .
The points that I have mentioned above are crucial to understanding the point I am now about to make.
Many theories most notably 'string theory' are accepted and are being furthered because even if we do not have conclusive experimental evidence to support these theories. They seem 'aesthetically beautiful' and have a harmonious structure. 'Symmetry', 'Gauge invariance' etc. are at the heart of these theories.
We perceive symmetry to be beautiful. We perceive the symmetries in our surroundings and note their significance. But then again, this is 'our perception'. What if this root is wrong?
What if we live in a world where another quantity lies at the heart of all our physical laws. Will we ever find it out? Will it ever be intuitively obvious to anyone?
And if we find this quantity. How will we know if it really is the right one?
Why is it that people thought so?
Well, you might say because it looks as if the sun is revolving around the earth!
Oh? Well what would it have looked like had the earth rotated about it's own axis instead!?!
So, then why was this thought was introduced so late?
We humans tread in our 'middle sized' world. Our intuitions and faculties are developed so that we can navigate this 'middle earth' :P. Our brains are designed to process what we perceive in a certain way. Does that mean that however superior a brain is, there are certain ideas that it will never be able to grasp?
I have read that rocks, especially crystals, have a lot of tiny open spaces inside them. But to us, when we hold a crystal in our hand, it seems massive and 'solid'. But neutrinos would perceive these rocks differently. They see these same rocks as full of massive spaces filled with air molecules.
Thus, the scope of our perceptions and ideas seem to have a limit. Will this affect our understanding of topics like quantum physics? (As this is on a totally different scale)
Will concepts like wave and particle duality be forever beyond our understanding? Will we ever get the 'feel' of such topics? Are we limited by our perceptions?
I really wonder. . .
The points that I have mentioned above are crucial to understanding the point I am now about to make.
Many theories most notably 'string theory' are accepted and are being furthered because even if we do not have conclusive experimental evidence to support these theories. They seem 'aesthetically beautiful' and have a harmonious structure. 'Symmetry', 'Gauge invariance' etc. are at the heart of these theories.
We perceive symmetry to be beautiful. We perceive the symmetries in our surroundings and note their significance. But then again, this is 'our perception'. What if this root is wrong?
What if we live in a world where another quantity lies at the heart of all our physical laws. Will we ever find it out? Will it ever be intuitively obvious to anyone?
And if we find this quantity. How will we know if it really is the right one?
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