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Sunday, December 2, 2012
The share of renewable energy is steadily increasing around the world. But storing such intermittent energy source and utilizing it when needed has been a challenge. In fact energy storage constitutes a significant portion of the cost in any renewable energy technology. Many storage technologies are currently available in the commercial market, but choosing a right type of technology has always been a difficult choice. In this article we will consider four types of storage technologies. The California Energy Commission conducted economic and environmental analyses of four energy storage options for a wind energy project: (1) lead acid batteries, (2) zinc bromine (flow) batteries, (3) a hydrogen electrolyzer and fuel cell storage system, and (4) a hydrogen storage option where the hydrogen was used for fueling hydrogen powered vehicle. Their conclusions were: ”Analysis with NREL’s (National Renewable Energy laboratory) HOMER model showed that, in most cases, energy storage systems were not well utilized until higher levels of wind penetration were modeled (i.e., 18% penetration in Southern California in 2020). In our scenarios, hydrogen storage became more cost-effective than battery storage at higher levels of wind power production, and using the hydrogen to refuel vehicles was more economically attractive than reconverting the hydrogen to electricity. The overall value proposition for energy storage used in conjunction with intermittent renewable power sources depends on multiple factors. Our initial qualitative assessment found the various energy storage systems to be environmentally benign, except for emissions from the manufacture of some battery materials. However, energy storage entails varying economic costs and environmental impacts depending on the specific location and type of generation involved, the energy storage technology used, and the other potential benefits that energy storage systems can provide (e.g., helping to optimize Transmission and distribution systems, local power quality support, potential provision of spinning reserves and grid frequency regulation, etc.)”. Key Assumptions Key assumptions guiding this analysis include the following: • Wind power will expand in California under the statewide RPS program to a level of approximately 10% of total energy provided in 2010 and 20% by 2020, with most of this expansion in Southern California. • Costs of flow battery systems are assumed to decline somewhat through 2020 and costs of hydrogen technologies (electrolyzers, fuel cell systems, and storage systems) are assumed to decline significantly through 2020. • In the case where hydrogen is produced, stored, and then reconverted to electricity using fuel cell systems, we assume that the hydrogen can be safely stored in modified wind turbine towers at relatively low pressure at lower costs than more conventional and higher-pressure storage. • In the case where hydrogen is produced and sold into transportation markets, we assume that there is demand for hydrogen for vehicles in 2010 and 2020, and that the Hydrogen is produced at the refueling station using the electricity produced from wind farms (in other words, we assume that transmission capacity is available for this when needed)? Key Project Findings Key findings from the HOMER model projections and analysis include the following: • Energy storage systems deployed in the context of greater wind power development were not particularly well utilized (based on the availability of “excess” off-peak electricity from wind power), especially in the 2010 time frame (which assumed 10% wind penetration statewide), but were better utilized–up to 1,600 hours of operation per year in some cases–with the greater (20%) wind penetration levels assumed for 2020. • The levelized costs of electricity from these energy storage systems ranged from a low of $0.41 per kWh—or near the marginal cost of generation during peak demand times—to many dollars per kWh (in cases where the storage was not well utilized). This suggests that in order for these systems to be economically attractive, it may be necessary to optimize their output to coincide with peak demand periods, and to identify additional value streams from their use (e.g., transmission and distribution system optimization, provision of power quality and grid ancillary services, etc.) • At low levels of wind penetration (1%–2%), the electrolyzer/fuel cell system was either inoperable or uneconomical (i.e., either no electricity was supplied by the energy storage system or the electricity provided carried a high cost per MWh). • In the 2010 scenarios, the flow battery system delivered the lowest cost per energy stored and delivered. • At higher levels of wind penetration, the hydrogen storage systems became more economical such that with the wind penetration levels in 2020 (18% from Southern California), the hydrogen systems delivered the least costly energy storage. • Projected decreases in capital costs and maintenance requirements along with a more durable fuel cell allowed the electrolyzer/fuel cell to gain a significant cost advantage over the battery systems in 2020. • Sizing the electrolyzer/fuel cell system to match the flow battery system’s relatively high instantaneous power output was found to increase the competitiveness of this system in low energy storage scenarios (2010 and Northern California in 2020), but in scenarios with higher levels of energy storage (Southern California in 2020), the Electrolyzer/fuel cell system sized to match the flow battery output became less competitive. • In our scenarios, the hydrogen production case was more economical than the Electrolyzer/fuel cell case with the same amount of electricity consumed (i.e., hydrogen production delivered greater revenue from hydrogen sales than the electrolyzer/fuel cell avoided the cost of electricity, once the process efficiencies are considered). • Furthermore, the hydrogen production system with a higher-capacity power converter and electrolyzer (sized to match the flow battery converter) was more cost-effective than the lower-capacity system that was sized to match the output of the solid-state battery. This is due to economies of scale found to produce lower-cost hydrogen in all cases. • In general, the energy storage systems themselves are fairly benign from an environmental perspective, with the exception of emissions from the manufacture of certain components (such as nickel, lead, cadmium, and vanadium for batteries). This is particularly true outside of the U.S., where battery plant emissions are less tightly controlled and potential contamination from improper disposal of these and other materials are more likely. The overall value proposition for energy storage systems used in conjunction with intermittent renewable energy systems depends on diverse factors. • The interaction of generation and storage system characteristics and grid and energy resource conditions at a particular location. • The potential use of energy storage for multiple purposes in addition to improving the dependability of intermittent renewable (e.g., peak/off-peak power price arbitrage, helping to optimize the transmission and distribution infrastructure, load-leveling the grid in general, helping to mitigate power quality issues, etc.) • The degree of future progress in improving forecasting techniques and reducing prediction errors for intermittent renewable energy systems • Electricity market design and rules for compensating renewable energy systems for their output Conclusions “This study was intended to compare the characteristics of several technologies for providing Energy storage for utility grids—in a general sense and also specifically for battery and Hydrogen storage systems—in the context of greater wind power development in California. While more detailed site-specific studies will be required to draw firm conclusions, we believe those energy storage systems have relatively limited application potential at present but may become of greater interest over the next several years, particularly for California and other areas that is experiencing significant growth in wind power and other intermittent renewable. Based on this study and others in the technical literature, we see a larger potential need for energy storage system services in the 2015–2020 time frames, when growth in renewable produced electricity is expected to reach levels of 20%–30% of electrical energy supplied. Depending on the success in improved wind forecasting techniques and electricity market designs, the role for energy storage in the modern electricity grids of the future may be significant. We suggest further and more comprehensive assessments of multiple energy storage technologies for comparison purposes, and additional site- and technology-specific project assessments to gain a better sense of the actual value propositions for these technologies in the California energy system. This project has helped to meet program objectives and to benefit California in the Following ways: • Providing environmentally sound electricity. Energy storage systems have the Potential to make environmentally attractive renewable energy systems more competitive by improving their performance and mitigating some of the technical issues associated with renewable energy/utility grid integration. This project has identified the potential costs associated with the use of various energy storage technologies as a step toward understanding the overall value proposition for energy storage as a means to help enable further development of wind power (and potentially other intermittent renewable resources as well). • Providing reliable electricity. The integration of energy storage with renewable energy esources can help to maintain grid stability and adequate reserve margins, thereby contributing to the overall reliability of the electricity grid. This study identified the potential costs of integrating various types of energy storage with wind power, against which the value of greater reliability can be assessed along with other potential benefits. • Providing affordable electricity. Upward pressure on natural gas prices, partly as a function of increased demand, has significantly contributed to higher electricity prices in California and other states. Diversification of electricity supplies with relatively low-cost sources, such as wind power, can provide a hedge against further natural gas price increases. Higher penetration of these other (non-natural-gas-based) electricity sources, Potentially enabled by the use of energy storage, can reduce the risks of future electricity.” (Source: California Energy Commission prepared by University of Berkeley).
Thursday, August 2, 2012
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Tuesday, March 20, 2012
It is amazing that highly combustible Hydrogen is a constituent of cool water. As long as it remains a part of a water molecule we are able to handle it easily. Water is always in a state of ionization with H+ and OH- ions in a dynamic equilibrium. The electrical conductivity of pure water which is completely free from any other ions is almost zero. In a solid polymer electrolyzer, which is the reverse of Fuel cell, water is decomposed into Hydrogen and Oxygen while passing a Direct current. Electrolyzer is an electrolytic cell similar to battery, containing an Anode, Cathode and Electrolyte. In a solid polymer Electrolyzer, the electrolyte is a polymer membrane. Water is decomposed as shown in the following reaction: At Anode of electrolyzer: H2O-------- 0.5 O2 + 2e + 2H† At Cathode of electrolyzer: 2H† + 2e ------ H2 The purity of water is critical in the above process of electrolysis. In conventional electrolysis, water with addition of potash lye (KOH) acts as an electrolyte. But in the above process there is no need for any addition of lye. Moreover, Hydrogen can be generated at high pressure so that further compression becomes easier. In cases of power generation using Fuel cell, the Hydrogen pressure from Electrolyzer is sufficiently high, obviating the usage of an additional compressor. The electrical conductivity of water increases as the concentration of dissolved salts increases. That is why the conductivity of seawater is much higher than your tapwater.But this salt can be removed by the process of desalination using ‘reverse osmosis’ systems. When you separate pure water and salt water using a semi permeable membrane there is natural tendency for pure water to pass across the membrane to pure water side. This process is called ‘Osmosis’. The process continues till the concentration of water on both side of the membrane becomes equal. Nature does not like disparities between strong and weak and always tend to make both equal. By reversing this principle of osmosis, we can separate salt water into pure water and highly concentrated salt water known as brine. This process is called ‘Reverse osmosis’. We will discuss about this process later. If your tap water is not very hard, say for example, total dissolved solids TDS is around 500ppm (Part per million), then the osmotic pressure is not high, which means you do not need to use a high pressure pump. Higher the TDS level, higher the osmotic pressure and higher the power consumption will be. You can install a reverse osmosis system based on your water analysis. You have to use a pure water with low electrical conductivity less than 1 micro Siemens/cm.The reverse osmosis system can be connected to your tap and store pure water while draining the salt water into the drain. You can use this pure water into an Electrolyzer to generate Hydrogen. The Hydrogen can be stored in a tank made up of Carbon composite materials that can withstand high pressure and approved by regulatory authorities. This article is only to understand how Hydrogen can be generated using your tap water. The actual implementation of the system requires knowledge and experience in installing such a system. But we will release an eBook, a step by step guide to set up your power generation system as well fuelling your Fuel cell car, using Hydrogen. An independent power generation and fuelling system using only solar power and water will soon become a commercial reality because, it is a clean and sustainable solution for all our energy problems. The PV solar industries are already expanding at a faster rate and solar Hydrogen will soon become an ultimate solution.
Sunday, March 11, 2012
There are many ways to increase the energy efficiency of an existing system which also helps invariably to reduce your carbon footprint. The inefficiencies breed pollution. Such inefficiencies can emanate from power generation methods or from power distribution methods. Energy cannot be stored but has to be utilized. That is one of the main reasons why the power companies look for large consumers and offer them the lowest tariff. Some industries like Caustic soda plants and Aluminum smelters, consume large power. If you are using power from the grid then you can discuss with your service provider and check whether you can switch over to green power. The tariff may be slightly higher than a standard tariff but certainly helps you to reduce your carbon footprint. Some service providers indicate your carbon foot print by way a chart in their monthly energy bill. Most of the energy providers supply green power such as solar and wind as part of their energy mix to ensure that they don’t lose customers who may insist on green power. You can check various power tariffs in your location such a peak tariff and off-peak tariffs and you will be surprised at the difference. The peak tariff is when everybody use power , normally 9am to 5pm.The usage of air-conditioners during peak hours in tropical countries is high They can use rooftop solar panels with batteries and inverters because many counties in Asia do not have feed-in tariff method by which you can export your surplus solar power to the grid. Moreover they do not have a choice in selecting a service provider because power generation and distribution are mostly runs by Governments or by very few service providers. The best method for such users is to store the solar energy in batteries and use them whenever they want. Even consumers who use grid power can store electricity during off-peak period using batteries and then use them during peak period using an inverter. This is an ideal solution for Asian countries where the power outage is frequent and unexpected. The best method will be to use an Electrolyzer to generate Hydrogen using off-peak power and tape water and store them under pressure. You can generate your own electricity using small Fuel cell .This electricity can be a Direct current that can be readily connected to a host of Direct current operated appliances including your air-conditioners and refrigerators. If your electricity load is relatively high then you can integrate both solar panels and grid power in such a way that you can store enough electricity by way of Hydrogen or in a battery and use them during peak period. By this method you can be certain of an uninterrupted power supply and at the same time a reasonable power tariff. You can reduce your carbon foot print substantially by utilizing solar power with Hydrogen storage. You can choose energy efficient appliances by looking at their star ratings.A star rating of 6 and above is considered very energy efficient. You can choose LED bulbs for lighting and I would suggest using Direct current for LED bulbs directly from Fuel cell or battery rather than from grid supply using an inverter. You can also check the type of refrigerants used in air conditioners and Refrigerators and their star ratings. If you have a roof top solar panel as part of electricity supply then I will recommend to use Direct current operated Air-conditioners and regfigerators.When you choose these appliances you can look for the type of motor, compressor and fans used, because these are the main parts that use electricity. An energy efficient motor and the type of compressor used are critical components in determining the capacity, airflow and noise levels. The energy ratings are based on these factors only. You can save energy and reduce your carbon footprint in every step of the way if you are keen to do it. The most important factor in achieving energy efficiency is an understanding of your contribution to the environment and the prudence with which you can accomplish these goals.
Saturday, March 3, 2012
In a regenerative fuel cell the results of redox reaction between Hydrogen and Oxygen, are power and water; the above reaction can be reversed in the same electrochemical process to regenerate hydrogen and oxygen. Such a system is called ‘regenerative fuel cell’. It is a perfect example of a closed circuit system. In ancient Hindu mythology there were citations that claim water came from fire and fire came from water. Two gaseous elements Hydrogen and oxygen reacts violently rather explosively resulting in cool water. Perhaps Hindu mythology terms this reaction as fire which results in water. Similarly by passing a direct current into water, it splits water into oxygen and renegenerates Hydrogen, which is a symbolic representation of Fire. Many would have watched a number of ‘you tube video footings’ on water gas. The water gas or Brown’s gas is a mixture of Hydrogen and oxygen along with undissociated water molecules liberated during the process of electrolysis. It can be lit into a flame similar to Oxy-acetylene flame and can be used even to cut metal plates. That is the power of brown’s gas, which I call Oxy-Hydrogen gas. This torch is commercially marketed for metal cuttings applications. But production of pure Hydrogen completely free from Oxygen is a matter of great commercial importance. Hydrogen is one of the lightest gases and it has a strong bondage with noble metals like Platinum and Palladium. Platinum as a catalyst with carbon as a carrier has a wider industrial applications such as Hydrogenations in fine chemicals and pharmaceuticals. The author has experience in such applications in bulk drug manufacturing such as Ephedrine and Paracetamol. In a PEM (proton exchange membrane fuel cell) MEA (membrane electrode assembly) is the heart. The Platinum catalyst coated on the surface of the ‘Nafion’ membrane reacts with gaseous Hydrogen gas. It strips the electron from hydrogen atom while the polymer membrane allows only proton to pass through. The expelled electron flows around the circuit. Flow of electron is nothing but current or electricity. The proton crosses the membrane and reacts with incoming Oxygen through cathode forming water. It is an exothermic reaction and generates heat similar to any combustion reaction, that has to be dissipated.In larger installation we can use this waste heat for a typical CHP (combined heat and power applications) such as power and steam or chilled water or for space cooling. Fuel cell (based on Hydrogen fuel) operates quietly with absolutely no emission except water, and of course, there is no smoke. It is an ideal power source for 24x7 applications such as hospitals, call centers, departmental stores and continues process industries. In the reverse process of a Fuel cell, the electrochemical devise becomes an Electrolyzer splitting water into Hydrogen and oxygen. The electrolyzer works the same way as Fuel cell but in reverse;the feed is de-ionized water and the products are Hydrogen and Oxygen. In bipolar alkaline electrolyzer, a catalyst such as potash lye is added whereas in solid polymer electrolyzers platinum acts as a catalyst similar to a Fuelcell. The generated Hydrogen comes under pressure obviating the use of an additional compressor. The Hydrogen is stored in cylinders for further usage. As I mentioned in my previous articles the power required to split water into Hydrogen and Oxygen is more than the power generated from the resulting Hydrogen by a Fuelcell.That means an input of excess energy is necessary for a regenerative fuel cell to operate successfully .Where this energy will come from depends on the cost benefit analysis to be made. Surplus Hydro power is ideal for such regenerative fuel cell applications. But we can also use various other renewable energy sources such as wind, solar, geothermal, OTEC depending upon the location and applications. The biggest advantage with regenerative fuel cell is there is no other input except the excess power to be supplied. When renewable energy is deployed on large commercial scales then regenerative fuel cell will become a clean solution of the future. I have no doubt in my mind that this will become a commercial reality. Of course the top policy makers should understand the potential and make a right decision and encourage more business and industries to deploy such systems. The energy costing model cannot be based on fossil fuel model because fossil fuel is not renewable. This is the crux of the problem. In our future articles we will present case studies of various clean energy systems that are already in commercial operation. I also welcome articles from clean energy professionals with real life project experience and problems they face. I welcome comments and feedback from business, industries and individuals.
Wednesday, February 29, 2012
Hydrogen is the cleanest source of energy that can power your homes and fuel your cars. It can potentially substitute diesel and petrol or coal and clean up our environment. Hydrogen has been manufactured industrially for the past several decades and transported across thousand of kilometers by pipelines in Europe. The science and technology of Hydrogen is well known but its application to generate power and fuel a car is relatively new. The gasoline internal combustion engines that drive our gasoline cars can be modified to suit Hydrogen fuel. But the physical and chemical properties of Hydrogen gas created a necessity to alter existing gasoline engines for commercialization. But such conversion has been painfully slow for couple of reasons. There is a stiff resistance from gasoline cars to switch over to Hydrogen because they have a well established infrastructure to manufacture gasoline cars and to supply gasoline through well established distribution network. But Hydrogen cars lack both of them. Even if the cars can be modified for Hydrogen, there are no sales or distribution network for the fuel Hydrogen, similar to Gasoline. Even consumers need to be educated that Hydrogen is safe, environmentally friendly and we need not depend on import of oil and so on. It is a blessing in disguise that Hydrogen can be generated by individual homes, business and industries for their captive use from their tap water. Recently Hydrogen fuelled scooters have been introduced in the market. There are number of advertisements in the media too; that you can fit a Hydrogen generator at your car that will reduce your gasoline bills substantially and also reduce your emissions.But these Electrolyzers can generate only water gas and not a pure Hydrogen. Yet such simple devices can help reduce your petrol bills to an extend .If things are so simple why are we still struggling with high crude oil prices and increasing electricity bills? Let us examine this in detail. Water (H2O) can be split into Hydrogen (H2) and Oxygen (O2) by simply passing an electric current through water using a battery. The water disassociates as follows: 2H2O ------------- 2H2 + O2 Stochiometrically, it means 36 lits of water will generate 4 Kgs of Hydrogen and 32 kgs of Oygygen.The current PEM (Proton exchange membrane) Fuel cell car (Honda FCX clarity) can drive 100 miles with just 0.105 kgs of Hydrogen from 5000 psi Hydrogen tank. Similarly 4kgs of hydrogen can generate about 100 kws of electricity using PEM Fuel cell, based on a conservative estimate; but 4Kgs of gasoline can generate only 15 kW electricity. The gasoline engine offers only 100km mileage from 13 kgs (16lits) of gasoline. In other words, 0.105 kgs of Hydrogen at 5000 psi gives the same mileage as 16 lits of Gasoline. This is the amazing power of water, yet to be unleashed! The tap water is suitable to generate Hydrogen by adding a little amount of potash lye to improve the electrical conductivity. An Alkaline water electrolyzer can be attached to the water tank to generate required amount of Hydrogen based on the above calculation. The resulting Hydrogen has to be compressed to a required level. The power consumption to electrolyze water will be about 75-80 kwhrs per Kg of Hydrogen generated at 5000 psi.Therefore 4Kgs of Hydrogen will require a power of 300kwhrs costing about $30 for a total mileage of 3800 miles. You will require a small reverse osmosis unit to be attached to your water tap so that the water is de-ionized so that there is no precipitation in the Electrolyzer or reduction in the efficiency of electrolysis. Recently, Suzuki Bargeman introduced Hydrogen Fuel cell scooter which claims to offer a mileage of 200km from 12 lits Hydrogen (carbon composite material) tank at an elevated pressure of 10,000psi.The future of Hydrogen car is very promising and finally the world can hope to get rid of smoke and noise from our roads and cities.