It's unbelievable but the current research and understanding of the fuel mechanism enables us to see beyond the conventional sources of energy especially non renewable ones such as coal,Natural Gas,crude oil etc.
Using sunlight to extract hydrogen from water has been the dream of generations of scientists and engineers, and remains the goal of researchers in the 21st century.
Hydrogen is the simplest element. An atom of hydrogen consists of only one proton and one electron. It's also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn't occur naturally as a gas on the Earth—it's always combined with other elements. Water, for example, is a combination of hydrogen and oxygen (H2O). Hydrogen is also found in many organic compounds, notably the hydrocarbons that make up many of our fuels, such as gasoline, natural gas, methanol, and propane. Hydrogen enjoys a long tradition as an energy carrier as well as a chemical resource. Its high energy content — 1 kg corresponding to 3.5 liter of petroleum or 1kg of hydrogen containsthe same amount of energy as 2.1 kg of natural gas or 2.8 kg of gasoline quickly led to its recognition as an ideal fuel in applications where weight rather than volume was the important factor: applications such as providing the lift for Balloons or Zeppelins and more recently as a fuel for spacecraft. That is why Hydrogen is the most suited alternate fuel as it produces water upon its combustion with oxygen in air. The idea of using Hydrogen as a fuel is not new, but interest in it has grown in recent years in view of the increasing pollution levels globally by the use of hydrocarbons as well as the fast depletion of the fossil fuel reserves of our planet. The move to a large scale hydrogen based energy sector will also be seen as an important option when the contribution by fluctuating generation electricity producers (Wind, Solar) reaches such a level that the electricity supply and demand can only be matched with the aid of a storage mechanism (this is a other very important aspect ). Hydrogen presently has the most attractive properties as a "Storage Medium" of electricity: Compared with the storage of electricity in batteries, the material costs are many times lower. This application is used on a small scale in the energy-autonomous solar house of the Fraunhofer Institute for Solar Energy Systems. Excess electricity is stored in a 5 m3 hydrogen tank and then used as required for heating support, cooking or regeneration of electricity at times of low solar radiation. If the same amount of energy were to be stored in batteries, a lead-acid battery installation weighing 40 t and consuming an area of 100 m3 would be needed. Independent of this long-term option, hydrogen can be used as a pollution free fuel for traffic applications. In the short term, this could best be applied to urban vehicles in order to reduce emissions in city centers, in long term however every form of transport vehicle could be effected, be it ships, trains or aeroplanes. The advantages of no pollution and reduced fuel weight are however coupled with an increase in the volume and weight of the required fuel tank, which for small vehicles would lead to a reduction in range and payload.
Both developed and developing countries (USA, Canada, Germany, Japan, China, India etc.) are conducting Research and Development in the area of hydrogen production, storage, transportation, safety, generating standards and application. The table given below shows the different facts related to hydrogen in comparison with other source of energy.
Hydrogen cannot be produced directly by drilling a well or mining. It must be extracted chemically from hydrogen rich materials such as natural gas / naphtha, water or plant matters. A number of technologies being studied include production of hydrogen from water or biomass using solar or other forms of renewable energy. In the currenet
Project approach here is to check and comparative study of mechanism and technologies involved with respect to efficiency( cost of source ,availibilty,amount,energy–content).Situation here is more complex when I encounter with different methods of extraction from same source water.
Problems in storage of Hydrogen:-
1. Hydrogen is a difficult fuel to store. It is difficult and costly to liquefy. There has been increasing success in storing hydrogen gas in metal hydrides and carbon compounds but many of these techniques require either pressure or temperature swings during storage and extraction. Many require cryogenic refrigeration.Which is of course costly.
2. Handling of hydrogen requires extra care due to The explosive regions for hydrogen and methane lie in the ranges 13% - 59% and 6.3% - 14% respectively. The explosive range for hydrogen is clearly much greater, whereas methane is already explosive at a much lower concentration. The diffusion coefficient for hydrogen at 0.61 cm3/s is 4 times as high as that for methane. Hydrogen therefore mixes in air considerably faster than methane or petrol vapor, which is advantageous in the open but represents a potential disadvantage in badly ventilated interiors. Since both hydrogen and natural gas are lighter than air they rise quickly.
Problems in extracting hydrogen from water by existing methods:-
Hydrogen Production by Electrolysis of Water
Electrolysis of water is the method that has been commonly applied and comparably ripe in technologies, with higher efficiency (75%-85%), heavy consumption in power. The hydrogen production by conventional electrolysis can obtain fewer gains in the respect of utilization of energy. Therefore, only if the cost of solar power generation can be reduced greatly, does the mass-scale hydrogen production by electrolysis be realized.
Hydrogen Production by Thermolysis of Water
When water or steam is heated to 3000K, hydrogen and oxygen in the water can be decomposed. This method can produce hydrogen in high efficiency of which high temperature is obtained by concentrator. Normally this method is not applied to producing the hydrogen.
3. Hydrogen Production by Thermochemical Cycles
In order to mitigate the high temperature required by direct thermolysis, thermochemical cycles are developed. This method is to input one or several intermediate into the water, which is heated to lower temperature. After experiencing variable reaction stage, the water is finally decomposed to hydrogen and oxygen with the consumption of intermediate for recycle use. The temperature for thermochemical cycles is ranging from 900 to 1200K, which is easily obtained by normal rotating parabolic concentrator. The decomposing efficiency is ranging from 17.5% to 75.5%. The existing main problem lies in the deoxidizing of the intermediate, even if deoxidizing by 99.9% to 99.99%, 0.1% to 0.01% complement should be made which may affect the price of hydrogen and result in environmental pollution.
4. Hydrogen Production by Photochemical Decomposing of Water
The process of hydrogen production is similar to that of thermochemical cycles, which is to add a kind of photosensitive matter as activator to increase the absorption on wave energy in sunlight. The hydrogen is produced by use of photochemical reaction. In Japan, a set of comprehensive hydrogen production flow including photochemical and thermoelectricity reaction was once designed by use of iodine¡¯s sensitiveness upon light. It can produce hydrogen 97L per hour and in an efficiency of 10%.
5. Hydrogen Production by Photoelectrical Chemical Cells
In 1972, photoelectrical chemical cells were developed in Japan by use of electrode of n-model titanium dioxide semiconductor as anode and platinum black as cathode. Under the radiation of sunlight, the cathode produced hydrogen while the anode produced oxygen. If two end of electrode were connected by conducting wire, current could be passing through which resulted that the hydrogen and oxygen production and electricity energy obtained can be simultaneously realized by photoelectrical chemical cells under the radiation of sunlight. This experiment result aroused high attention in the scientists in each country, and was regarded as a breakthrough in solar energy technologies. But the efficiency was very lower, only 0.4%. It can only absorb the ultraviolet light among the sunlight, and the electrode is subject to be corrosive with unsteady performance. Therefore, the photoelectrical chemical cells have not yet satisfied the application needs.
6. Hydrogen Production by Complication Catalysis
Since 1972, scientists have found that the excited state of tri link pyridine ruthenium complex compound is capable to transfer the electron, catalyze the transfer of electric charge. They proposed to utilize such process to produce hydrogen. This complex compound was a kind of catalyzer, functioned as absorption of light energy, producing the separation of electric charge, transfer and concentrating of electric charge. Through a serial of process, the water will finally be decomposed to hydrogen and oxygen. This technology has not been ripe and the research is undergoing.
Due to various kinds of constraints and very low efficiency as above lines state .we have to take different approach. The solution of problem is nowhere else but in nature. The approach here is based on “photosynthesis” , principles of photochemistry, photobiological processes.
Towards the ever lasting solution: -
Basics of photosynthesis and correlation with approach taken in this project:-
It is a very complex process carried out by green plants, blue-green algae, and certain bacteria. These organisms are able to harness the energy contained in sunlight, and via a series of oxidation-reduction reactions, produce oxygen and sugar, as well as other compounds which may be utilized for energy as well as the synthesis of other compounds. The sun transmits solar energy to the plant in the form of light. When combined with the intake of CO2 and H2O, CO2 and H are given off to form glucose. Oxygen is also given off and released into the atmosphere. This is actually a two part process involving both a light and a dark phase. One process involves the splitting of water. This process is really an oxidative process that requires light, and is often referred to as the "light reaction". This reaction may be written as:
chlorophyll 12 H2O -----------------------> 6 O2 + 24 H+ + 24e- step 1(very crucial step with respect to hydrogen generation ) light or radiant energy
The energy contained in both NADPH and ATP is then used to reduce carbon dioxide to glucose, a type of sugar (C6H12O6). This reaction, shown below, does not require light, and it is often referred to as the "dark reaction". 6 CO2 + 24 H+ + 24 e- ------> C6H12O6 + 6 H2O step 2 The step 2 is essential for life support(as it is giving glucose a form of carbohydrates ) .If we look on step 1 which is giving H+ which can be converted into 1/2H2.
The problem is this, the moment H+ is taken out ,step 2 will not occur which is crucial for life support. So it is very difficult to carry out this procedure on higher(in losse sense on common) plants.Now there is two approach fisrt one is like this(of course various researches are going on this approach but I want to add something,let me first discuss it )
1. However if in step 1 the amount of hydrogen yielded is greater than amount required in step 2. Then the plant will survive as well as produce hydrogen ion and oxygen in the process of photosynthesis. Plant researchers have found such plants(specialy microorb like green-blue alage) which gives hydrogen as by product the constraint is it should happen in no oxygen envirnoment. The internal reaction involved is somewhat similar to step1 of photosynthesis.The process is described below.
Production of hydrogen through photobiological methods from water:-
Algal Hydrogen Production:-Green algae can produce hydrogen by splitting water through a process called "biophotolysis" or "photobiological hydrogen production." The process of photosynthesis, of course, produces oxygen and this normally stops hydrogen production very quickly in green algae(The problem will be discussed later). The name of that green alga is Chlamydomonas reinhardtii. Chlamydomonas reinhardtii possesses an enzyme called hydrogenase that is capable of splitting water into its component parts of hydrogen and oxygen. The researchers have determined the mechanism for starting and stopping this process, which could lead to an almost limitless method for producing clean, renewable hydrogen. The algae need sulfur to grow and photosynthesize. Scientists found that when they starved the algae of sulfur, in an oxygen-free environment, the algae reverted to a hydrogenase-utilizing mode .This means it starts producing Hydrogen. Which may be taken out or collected .To prevent this algae’s death we periodically supply the sulphure to switch from photosynthesis to hydrogenase-utilizing mode.Hydrogenase: -
Hydrogenases are a class of enzymes that catalyze the reversible reduction of protons (H+) to molecular hydrogen (H2).
2H+ + 2e- + (enzymes)---------------------> H2
Hydrogenates are divided into three classes based on the metal composition of their catalytic center: [NiFe]-hydrogenates, [Fe]-hydrogenates and metal-free hydrogenates. [Fe]-hydrogenates have a unique prosthetic group named the H-cluster in their catalytic site, and thus have 100-fold higher activity than hydrogenates in the other two groups.That’s my concern will be only with [Fe]-hydrogenates. [Fe]-hydrogenates are further divided into three families based upon the number and type of prosthetic [Fe-S] clusters, called F-clusters, and upon the type of natural electron donor. All the three [Fe]-hydrogen's families share three highly conserved domains containing the four cysteines that coordinate the active center. The first family of [Fe]-hydrogenates consists exclusively of enzymes found in green algae. In green algae, ferridoxin (PetF) serves as the physiological electron donor to HydA, transferring electrons from the photosynthetic electron transport chain to the chloroplastic HydA enzyme under anaerobic conditions. HydA genes have been identified in Chlorococcum littorale, Chlorella fusca, S. obliquus and Chlamydomonas Reinhardt. However, HydA is not universally present in all green algae.Thus there is two way to do this thing.
one pathway under dark conditions and the other under light conditions. The algal [Fe]-hydrogenases has its main role during fermentation that occurs in the light, resulting in the production of large quantities of H2, formate and carbon dioxide while reducing the production of ethanol and eliminating totally the production of acetate. Thus, hydrogenase participates in reorganization of reducing equivalents and photosynthetically generated electrons from fermentation by reduction of protons. H2 gas ultimately acts as the major electron sink under these conditions.The fermentative pathways in green algae are more efficient than in higher plants. Even higher plant species known for their tolerance to oxygen deprivation have limited survival capacity, indicating that anaerobic metabolism is a suitable substitute for aerobic metabolism for only a short period of time in higher plants. Maize roots, for example, survive only for three days in an oxygen deficient environment.It has been demonstrated that under conditions of oxygen shortage, Chlamydomonas reinhardtii cells switch to fermentative metabolism within minutes. C. reinhardtii cultures produce large amounts of H2 gas when experiencing sulfur deprivation.what
I am suggesting here followings:-
1. To increase the hydrogenase level(hydrogen producing mode) in algal cells ,there is need to increase the concentration of above enzymes. How it can be done? The advancement in genetic engineering will do the job.By creating changes in genetic patterns(after identifying corresponding genes ) of cells will give new strain of this.which will be more rich in mentioned enzyme.
2. Further survival period(by depriving them from general photosynthesis) will be increased by doing gene-modifications in corresponding genes.
3. External induction of corresponding chemicals substance(which is equivalent to enzyme) may give positive impact on kinetics of hydrogen producing stage.
4. Since mentioned enzyme is highly sensitive to the oxygen hence there is need to reduce the oxygen sensitivity of this by either through chemical inhibition or through genetic engineering in the genes of cells of above algae.
5. There is need to increase the photosynthetic efficiency.It can be done by genetic modifications in gene pattern as well as chemical induction.
Benefits of this approach:-
1. However lot to be done to increase the efficiency level to even close to 10%(the amount of solar energy absorbed by algae).But if it will be done the definitely there will be no crisis of energy,pollution etc.
2nd approach( through creating step1of photosynthesis in laboratory described as above):-
Basics of this approach are followings:-
a. First of all it is required to synthesize the chlorophyll as chemical substance or equivalent chemical substance which will do the same job as chlorophyll does in step1.Some light on the chlorophyll role in photosynthesis and equivalent model.
In nature, when sunlight contacts each assembly of some 300 chlorophyll molecules, only a single pair of pigment molecules, called the “reaction centre,” donates excited electrons to an acceptor. The other molecules only transfer energy to the reaction centre, and are called “antennae. Daniels, who had pointed out that the chloroplasts ‘have alternate layers of materials that are wet by water and that repel water and the chlorophyll molecules are probably located at the interfaces in such a way that the products of the photochemical reaction scan be kept separate’. Further, research efforts should be directed toward the photochemical behavior of chlorophyll outside the chloroplast under radically different conditions, and this might lead to a method of artificial photosynthesis. Clearly,what Rabinowitch and Daniels had in mind was that a study of natural photosynthesis might point the way toward research in the quest for new photochemical reactions that can use and store solar energy. Concurrently, advances in solid state physics, photoelectrochemistry, and membrane biophysics have made crucial contributions to the understanding of the phenomena at the interfaces. Pigment molecules embedded in the thylakoid membrane mediate the reactions. Structurally,the principal construct of the thylakoid membrane is a lipid bilayer. On one side of the membrane/solution interface, water is oxidized to its basic components (electron, proton and oxygen).On the other side, light-generated electrons and protons reduce carbon dioxide to energy-rich products such as carbohydrates. These reactions take place in plants, algae and some types of bacteria. Through photosynthesis, the trapped free energy is then used to drive the formation of organic compounds. In green plants and algae, the photosynthetic process depends on complex protein molecules embedded in the lipid bilayer of thylakoid membrane. The protein complexes embedded in the lipid bilayer, separating two aqueous phases,have a unique orientation with respect to the inner and outer phase (stroma). The asymmetrical arrangement of the protein complexes allows some of the energy released during electron transport to create an electrochemical gradient of protons across the thylakoid membrane. In photosynthesis,there are the so-called ‘light reactions’, which consist of electron and proton transfer reactions and the ‘dark reactions’(as described above).More specifically, the light reactions occur in a complex bilayer lipid membrane system. The first step is the conversion of a photon to an excited electronic state of a pigment molecule located in the antenna system. The antenna system consists of hundreds of pigment molecules (mainly chlorophyll and carotenoids) that are anchored to proteins within the thylakoid membrane and serve a specialized protein complex known as a reaction center. The electronic excited state is transferred over the antenna molecules as an exciton. Some excitons are converted back into photons and emitted as fluorescence, some are converted to heat, and some are trapped by a reaction center protein. Excitons trapped by a reaction center provide the energy for the primary photochemical reaction of photosynthesis: the transfer of an electron from a donor molecule to an acceptor molecule. In terms of time scale, the photosynthetic process is initiated by the absorption of a photon by a pigment molecule, which occurs in about a femtosecond (10–15 s) and causes a transition from the electronic ground state to an excited state. Within 10–13 s the excited state decays by vibrational relaxation to the first excited singlet state. The fate of the excited state energy is guided by the structure of the protein. Exciton energy transfer between antenna molecules is due to the interaction of the transition dipole moment of the molecules. The probability of transfer is dependent on the distance between the transition dipoles of the donor and acceptor molecules (1/R6), the relative orientation of the transition dipoles, and the overlap of the emission spectrum of the donor molecule with the absorption spectrum of the acceptor molecule. These molecules are located in the so-called photosystem I (PS I) and photosystem II (PS II) reaction centers. In more details, PSII, made of more than fifteen polypeptides and at least nine different redox components, uses the photon energy to drive two chemical reactions: the reduction of plastoquinone and the oxidation of water. Further, the PS-II complex undergoes a light-induced electron transfer and is initiated by charge separation between P680 and pheophytin (Pheo), creating P680 +/Pheo–. Primary charge separation occurs in a few picoseconds (10–12 s). The presence of the lipid bilayer prevents the primary charge separation from recombining. PS-II contains the only known protein complex that can oxidize water, resulting in the release of O2 into the atmosphere. At present, however, little is known concerning the molecular events resultingin water oxidation, despite years of research. Energetically, water is an indigent electron donor.The oxidation-reduction midpoint potential of water is +0.82 V (pH 7). In PS-II, this reaction is driven by the oxidized reaction center, P680 + (the midpoint potential of P680/P680 + is estimated to be +1.2 V at pH 7). How electrons are transferred from water to P680 + is still obscure. It is known that P680 + oxidizes a tyrosine on a certain membrane protein and that Mn plays a key role in water oxidation. Four Mn ions are present in the wateroxidizing complex. X-ray absorption spectroscopy shows that Mn undergoes light-induced oxidation. Water oxidation requires two molecules of water and entails four sequential turnovers of the reaction center as evidenced by flash excitation experiments. Each photochemical reaction creates an oxidant that removes one electron. The net reaction results in the release of one O2 molecule, the deposition of four H+ into the inner water phase, and the transfer of four electrons (producing two reduced plastoquinone molecules). Thus, as a result of electron transfer and proton translocation, a proton electro potential gradient is created, which results from two types of reactions: (a) the release of protons during the oxidation of water by PS-II and the translocation of protons from the outer aqueous phase to the inner aqueous phase by the coupled reactions of PS-II and the cytochrome bf complex in reducing and oxidizing PQ on opposite sides of the bilayer lipid membrane, and (b) the primary charge separation at the reaction center drives an electron across the lipid bilayer, which creates an electric potential across the thylakoid membrane. For example, during photosynthesis, the outer pH is typically near 8 and the inner pH is typically near 6, giving a pH difference of 2 (~120 mV) across the membrane.
Some important points from above paragraph:-
1. The behavior of chlorophyll is like a ordinary battery in which the thylakoid membrane behaves like cathod and anode ,electrolyte is water,voltage developed across is 120 mV,catalyst is sun light ,In the process H2 generated out.
2. The time scale of the reaction involved is in femtosecond.
Equivalent to role of chloroplast in photosynthesis:-
A semiconducter surface has dual purpose. It absorb solar energy and act as an electrode for dissociation of water Hydrogen can be and has been produced directly from aqueous solutions, including seawater, in a semiconductor septum electrochemical
photovoltaic SC-SEP cell. The origin of the SC-SEP cell is traceable to early studies of membrane biophysicsaspects of photosynthesis, which goes back more than 30 years to the time when it was found that an BLMs (p-BLM) have been extensively investigated as models of photoactive biomembranes . The heart of this novel solar or SC-SEP cell is a semiconductor septum bipolar electrode, taking the place of the pigmented BLM, separating two aqueous solutions. An example of this type of electrode is a n-type polycrystalline cadmium selenide (CdSe) deposited on metal (e.g., nickel foil) separating two compartments filled with electrolytes. Shining light on the CdSe septum induces electron and hole separation within the semiconductor depletion layer. The contacting electrodes immersed in the front and back compartments complete the circuit. For a workable SCSEP cell, light induced voltage and current over 1V and tens of mA/cm2, respectively, have been obtained. This is in sharp contrast with conventional photoelectrochemical cells (PECs) whose reported photovoltage rarely exceed 800 mV and operate as a battery in the dark. The fundamental process of natural photosynthesis involves the light-driven charge separation and translocation across an ultra-thin pigmented lipid membrane separating two aqueous phases, in which oxidation and reduction take place on opposite sides of the membrane. Through the redox reactions water is split into its basic components (electron, proton and oxygen), which allow the green plant to convert solar energy into stored chemical energy. This insight is the main idea of the SC-SEP cells which have been taken from the modeling of the photosynthetic thylakoid membrane using pigmented BLMs. The simplicity of the SC-SEP cell, makes it suitable for the generation of electricity, for the process-scalephotoelectrolysis of water to hydrogen, and possiblyfor pollution control.
Benefits of this methods:-
1. It is now became more realizable due to advances in solid state physics,nanotechnology,biotechnology(to create same memebrane like structure and equivalent chemicals) and better understanding of photosynthesis.
2. Efficiency is much higher than any other method known .
Comparision between two approaches described above:-
1. The first method works irrespective of light presence (of course amount of H2 obtained in dark is greater than in presence of light) .While in second approach presence of light is required,but efficiency is much higher.
2. The success of first approach depends upon advancement in genetic engineering.while second approach is completely materialistic which is realizable.
3. The generation of hydrogen by first approach will be cheaper than latter one.
4. On large scale the second approach is still experimental.
5. First approach required a large amount of culture of strain and space .
Combination of two will solve the problems:-
I am proposing a model through which we can create a continuous source of hydrogen generator.In day suppose a plant based on idea of SC-SEP cells is generating as much hydrogen which is required. Simultaneously we have as much cluture(a preparation of mentioned strain in water having certain concentration ) of mentioned strain of green –blue alage which will be responsible for night production of required hydrogen.The problem here is variation in intensity of sunlight during day (due to clouds and other changes).That is what this combination gives solution for above.It is like chemical equilibrium, moment one ‘s productivity goes down other’s productivity increases(that is what I have discussed above with respect to first approach) .Thus it solves our intensity- sensitiveness in production of hydrogen in day.In normal days production of hydrogen through this strain of green blue alage(definitely less than dark) can be used as reserved hydrogen.( Success in storage of hydrogen in recent years makes this job simpler ,economical and efficient specially through the liquid ammonia methods.)This hydrogen in day by mentioned strain of green blue alage is like bonus.
The approach here(in this project idea ) is to check the comparative study of existing or modified(as I have suggested in two approaches) mechanism and technologies involved in extraction of hydrogen from water with respect to efficiency( cost of source , availability,amount,energy –content).As far as figures are concerned, I think you will be agree to this fact that only extensive research on my suggested points can give this. This report can be treated as developing a concept or mechanism , which could do a better job of communicating or understanding of a concept than other existing solutions.It can be treated as a marginal change in an existing solution or strategies(as I have mentioned here and there in discussion of approaches) which could result in a dramatic change/impact) a product for a particular problem(as discussed above paragraph) that services a specific need . This project is based on understandings of problems faced in due course of time and not mere dreaming.I have been sensitive(throughout report) towards the side problems arises with respect to two approaches.


This work is licensed under a Creative Commons Attribution 3.0 Unported License,Author,2009.