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Showing posts with label CHP. Show all posts
Showing posts with label CHP. Show all posts

Thursday, July 11, 2013

How to control Carbon emissions in coal-fired power plants?

“Over two-thirds of today’s proven reserves of fossil fuels need to still be in the ground in 2050 in order to prevent catastrophic levels of climate change” – a warning by scientists. There is a great deal of debate on climate change due to man-made Carbon emissions and how to control it without any further escalation. The first obvious option will be to completely stop the usage of fossil fuel with immediate effect. But it is practically not feasible unless there is an alternative Non-Carbon fuel readily available to substitute fossil fuels. The second option will be to capture carbon emission and bury them under ground by CCS (Carbon capture and sequestration) method. But this concept is still not proven commercially and there are still currently many uncertainties with this technology, the cost involved and environmental implications etc.The third option will be not to use fresh fossil fuel for combustion or capture and bury the Carbon emissions but convert the Carbon emissions into a synthetic hydrocarbon fuel such as synthetic natural gas (SNG) and recycle them. By this way the level of existing Carbon emission can be maintained at current levels without any further escalation. At least the Carbon emission levels can be reduced substantially and maintained at lower levels to mitigate climate changes. It is technically feasible to implement the third option but it has to be implemented with great urgency. One way of converting Carbon emission is to capture and purify them using conventional methods and then react with Hydrogen to produce synthetic natural gas (SNG) CO2 + 4 H2 ----------> CH4 + 2 H2O The same process will be used by NASA to eliminate carbon built-up in the flights by crew members during their long voyage into the space and also to survive in places like Mars where the atmosphere is predominantly carbon dioxide. But we need Hydrogen which is renewable so that the above process can be sustained in the future .Currently the cost of Hydrogen production using renewal energy sources are expensive due to high initial investment and the large energy consumption. We have now developed a new process to generate syngas using simple coal, which is predominantly Hydrogen to be used as a Carbon sink to convert Carbon emissions into synthetic natural gas (SNG). The same Hydrogen rich syngas can be directly used to generate power using gas turbine in a simple or combined cycle mode. The Carbon emission from the gas turbine can be converted into SNG (synthetic natural gas) using surplus Hydrogen-rich syngas. The SNG thus produced can be distributed for CHP (combined heat and power) applications so that the Carbon emission can be controlled or distributed. By implementing the above process one should be able to maintain Carbon at specific level in the atmosphere. Existing coal fired power plants can retrofit this technology so that they will be able to reduce their Carbon emissions substantially; they can also produce SNG as a by-product using their Carbon emissions and achieve zero Carbon emission at their site while generating revenue by sale of SNG. Coal is the cheapest and widely used fossil fuel for power generation all over the world. Therefore it will be a win situation for everyone to use coal and also to reduce Carbon emissions that can address the problems of climate change. Meanwhile research is going on to generate renewable Hydrogen cheaply directly from water using various technologies. But we believe we are still far away from achieving this goal and we require immediate solution to address our climate change problems. Recently BASF made a press release‎ claiming a break-through technology to generate Hydrogen from natural gas without any CO2 emissions.

Tuesday, July 2, 2013

Australian Carbon tax shows the world a way to a cleaner future

Taxing Carbon pollution is already paying the dividends according to the National Energy Market of Australia. Such a tax will encourage fossil fuel fired power plants to rethink the way they generate power and emit the Carbon into the atmosphere. For example, black and brown coal power plants can switch over to gasification technology from their existing combustion technology which can reduce their Carbon emissions. Coal fired power plants can switch over to gas fired power plants and reduce their emissions by almost 50%. By employing CHP (combined heat and power) the gas fired power plants can reduce their Carbon emission as much as 75%. Taxing Carbon will encourage efficiency and reduce pollution. Australian Carbon tax is a good example which has clearly shown the way to reduce Carbon pollution and to encourage renewable energy. The following is an excerpt from Climate Institute of Australia: “Emissions from electricity are falling: Annual carbon emissions from the National Electricity Market fell by over 12 million tonnes (CO2-e) between June 2012 and May 2013. They fell by only around 1.5 million tonnes over the previous twelve-month period. Carbon pollution per megawatt-hour has also fallen: from 0.86 to 0.81 tonnes per unit of output, or a little over 5 per cent. According to the National Energy Market (NEM) data released in June this year, Australia’s electricity supply is becoming cleaner: electricity from renewable sources has risen by nearly 23 per cent and natural gas power by more than 5 per cent since the previous twelve months to May 2012. At the same time, the use of brown coal has fallen by about 12 per cent and black coal by more than 4 per cent. Generation by Australia’s seven biggest coal-fired power stations has fallen by over 13 per cent. Structural changes driven by the high Australian dollar, rising electricity prices, introduction of energy efficiency measures, increased home installations of solar photovoltaic (PV), and the Renewable Energy Target are key drivers of this change. However, early indications are that the carbon price is playing a supporting role by make renewable energy even more competitive compared to fossil-fuel generation. As the price becomes more embedded in longer-term investment decisions the role of the carbon price will increase. Electricity price-rises—perception and reality: For businesses and consumers alike, electricity prices have been rising sharply for several years—more than 40 per cent in the last few years. On average, more than half of this rise is the result of network upgrades, including the replacement of aging infrastructure. Despite the recent increases, however, when adjusted for inflation, electricity prices are about the same as they were a generation ago. Yet, according to the Australian Industry Group, there is still a false perception amongst many in business that the carbon price is the biggest contributor to rising prices. The biggest of [the] …pressures [on prices] is the rising cost of electricity networks, the poles and wires that deliver power. The high profile of the carbon tax appears to have led to some over-estimation by businesses of the specific impact of the carbon tax on energy prices… For residential retail customers, the carbon price accounted for around 9 per cent of power bills in 2012–13, or between about $2 and $4 extra per week, depending upon the state or territory. It should be noted that the carbon price is unlikely to materially increase bills any further in the next few years, although prices will continue to rise for reasons that have nothing to do with the price on pollution. An upshot of recent price rises—and scare-campaigning by some in politics and industry—may be the spread of a more energy-efficient ethos: in 2012, approximately 90 per cent of Australians did something to minimize their power bills, according to the Australian Bureau of Statistics. Such changes in consumer and business behavior are likely to help cushion the impact of any future price-rises. The cost of living has not skyrocketed: Before 1 July, 2013, the Australian Treasury predicted that the carbon laws would add 0.7 per cent to the Consumer Price Index, while CSIRO and global consulting firm AECOM conservatively predicted inflation at 0.6 per cent, given 100 per cent cost pass-through. This was part of a study for The Climate Institute, Choice, and the Australian Council of Social Service (ACOSS). The impact of the carbon price on particular prices is barely discernible. Indeed, the ABS has said it is unable to discern any impact against normal variability in consumer prices. One estimate, by Westpac Economics, suggests the reality is that the carbon price has added just 0.4 per cent to the Consumer Price Index. For the vast majority of Australian households, the increase their cost of living has been very small and this will be covered by the assistance Package associated with the scheme. According to independent analysis, for a low-income family of four, for instance, assistance is, on average, around $31 per week; for a single pensioner, it’s a little over $19 and for a middle-income family of four, it’s about $13. Federal assistance was projected to leave the large majority of households better off. Looking forward The hyperbole that characterized the twelve months to 1 July 2013 has largely given way to reality. The carbon laws have not undermined Australia’s economic performance nor have they raised the cost of living substantially. What is more, the package of carbon laws is contributing to emissions from electricity falling, the energy mix shifting in favor of renewable and cleaner fuels, and energy use is becoming more efficient. Low-carbon investment is flowing—the carbon price at work using money raised by the price on pollution, over six years, $946 million is committed to maintain stocks of carbon in bush land, and to enhance the resilience of natural systems to climate change. In the first round of the Biodiversity Fund, around $270 million has been allocated to more than 300 landscape rehabilitation and restoration projects around the country. Hundreds of firms are investing in energy efficiency, cleaner manufacturing, and innovative renewable energy projects, such as geothermal and solar-thermal. Many have received grants drawn from monies raised by the carbon price. Federal clean technology funding programs total $1,200 million over the next few years. Already, companies with household names like Arnott’s, Bundaberg Sugar, Bega Cheese, CSR, and Coca-Cola, together with many others, have received public grants leveraging considerably more private investment. Meanwhile, the Carbon Farming Initiative is seeing the big end of town investing new money in regional and rural communities. Between them, BP Australia, CS Energy, CSR, and Energy Australia have purchased more than 322,000 Australian carbon Credit Units, representing more than $7 million in low-carbon projects, such as sustainable forestry, cleaner livestock production, better landfill operations, and savannah management. Overall, Australian Carbon Units and ACCUs purchased by fossil-fuel power stations were worth $39 million in June 2013.” President Obama has recently outlined his policy on climate change and Carbon pollution reduction measures.US and the rest of the world can learn lessons from Australian experience on how low Carbon economy can be achieved without compromising an economic and industrial growth. In fact low Carbon economy can create millions of jobs and a sustainable future. The same polluting Carbon can become a source of cheap Hydrogen by innovative gasification technology. Innovation is the key to achieve a sustainable energy mix between renewable and fossil fuels.

Thursday, August 2, 2012

Solar Hydrogen for homes and cars.

Renewable Hydrogen offers the most potential energy source of the future for the following reasons. Hydrogen has the highest heat value compared to rest of the fossil fuels such as Diesel, petrol or butane. It does not emit any greenhouse gases on combustion. It can readily be generated from water using your roof mounted solar panels. The electrical efficiency of fuel cell using Hydrogen as a fuel is more than 55% compared to 35% with diesel or petrol engine. It is an ideal fuel that can be used for CHP applications. By properly designing a system for a home, one can generate power as well as use the waste heat to heat or air-condition your home. It offers complete independence from the grid and offers complete insulation from fluctuating oil and gas prices. By installing a renewable Hydrogen facility at your home, you can not only generate Electricity for your home but also fuel your Hydrogen car. The system can be easily automated so that it can take care of your complete power requirement as well as your fuel requirement for your Hydrogen car. Unlike Electric cars, you can fill two cylinders of a Hydrogen car which will give a mileage of 270miles.You can also charge your electric car with Fuel cell DC power. Renewable Hydrogen can address all the problems we are currently facing with fossil fuel using centralized power generation and distribution. It will not generate any noise or create any pollution to the environment. It does not require large amount of water. With increasing efficiency of solar panels coming into the market the cost of renewable Hydrogen power will become competitive to grid power. Unlike photovoltaic power, the excess solar power is stored in the form of Hydrogen and there is no need for deep cycle batteries and its maintenance and disposal. It is a one step solution for all the energy problems each one of us is facing. The only drawback with any renewable energy source is its intermittent nature and it can be easily addressed by building enough storage capacity for Hydrogen. Storing large amount of energy is easy compared to battery storage. The attached ‘You Tube’ video footages show how Solar Hydrogen can be used to power your home and fuel your Hydrogen car. Individual homes and business can be specifically designed based on their power and fuel requirements.

Wednesday, August 1, 2012

Global warming and man-made greenhouse gas.

There is a raging debate going on around the world especially in US about the global warming and its causes, among scientists and the public alike. When IPCC released its findings on the connection between greenhouse gas emission and the global warming and its disastrous consequences, there was an overwhelming disbelief and skepticism in many people. In fact many scientists are skeptical even now about these findings and many of them published their own theories and models to prove their skepticism with elaborate ‘scientific explanations’. I am not going into details whether greenhouse gas emission induced by human beings causes the globe to warm or not, but certainly we have emitted billions of tons of Carbon in the form of Carbon dioxide into the atmosphere since industrial revolution. Bulk of these emissions is from power plants fueled by Coal, oil and gas. Why power plants emit so much Carbon into the atmosphere and why Governments around the world allow it in the first place? When the emission of Oxide of Nitrogen and Sulfur are restricted by EPA why they did not restrict Oxides of carbon? The reason is very simple. They did not have a technology to generate heat without combustion and they did not have a technology to generate power without heat. It was the dawn of industrial revolution and steam engines were introduced using coal as a fuel. The discovery of steam engines was so great and nobody was disturbed by the black smoke it emitted. They knew very well that the efficiency of a steam engine was low as shown by Carnot cycle, yet steam engine was a new discovery and Governments were willing to condone Carbon emission. Governments were happy with steam engine because it could transport millions of people and goods in bulk across the country and Carbon emission was not at all an issue. Moreover carbon emission did not cause any problem like emission of oxides of Sulfur because it was odorless, colorless and it was emitted above the ground level away from human sight. However the effect of Carbon is insidious. Similarly, power generation technology was developed by converting thermal energy into electrical energy with a maximum efficiency of 33%.This means only 33% of the thermal energy released by combustion of coal is converted into electricity. When the resulting electricity is transmitted across thousands of kilometers by high tension grids, further 5-10% power is lost in the transmission. When the high tension power is stepped down through sub stations to lower voltage such as 100/200/400V further 5% power is lost. The net power received by a consumer is only 28% of the heat value of the fuel in the form of electricity. The balance 67% of heat along with Greenhouse gases from the combustion of coal is simply vented out into the atmosphere. It is the most inefficient method to generate power. Any environmental pollution is the direct result of inefficiency of the technology. Governments and EPAs around the world ignore this fact.Thanks to President Obama who finally introduced the pollution control bill for power plants after 212 years of industrial revolution. Still this bill did not go far enough to control Carbon emission in its current form. Instead of arguing whether globe is warming due to emission of Carbon by human beings or not, Scientists should focus on improving the science and technology of power generation. For example, the electrical efficiency of a Fuel cell is more than 55% compared to conventional power generation at 33% and emits reduced or no carbon. Recent research by MIT shows that such conversion of heat into electricity can be achieved up to 90% compared to current levels of 35%.Had we developed such a technology earlier, probably we will not be discussing about GHG and global warming now. MIT research group is now focusing on developing new Thermophotovoltaics and according to their press release: “Thermal to electric energy conversion with thermophotovoltaics relies on radiation emitted by a hot body, which limits the power per unit area to that of a blackbody. Micro gap thermophotovoltaics take advantage of evanescent waves to obtain higher throughput, with the power per unit area limited by the internal blackbody, which is n2 higher. We propose that even higher power per unit area can be achieved by taking advantage of thermal fluctuations in the near-surface electric fields. For this, we require a converter that couples to dipoles on the hot side, transferring excitation to promote carriers on the cold side which can be used to drive an electrical load. We analyze the simplest implementation of the scheme, in which excitation transfer occurs between matched quantum dots. Next, we examine thermal to electric conversion with a glossy dielectric (aluminum oxide) hot-side surface layer. We show that the throughput power per unit active area can exceed the n2 blackbody limit with this kind of converter. With the use of small quantum dots, the scheme becomes very efficient theoretically, but will require advances in technology to fabricate.” Ref:J.Appl.Phys. 106,094315c(2009); “Quantum-coupled single-electron thermal to electric conversion scheme”. Power generation and distribution using renewable energy sources and using Hydrogen as an alternative fuel is now emerging. Distributed energy systems may replace centralized power plants in the future due to frequent grid failures as we have seen recently in India. Most of the ‘black outs’ are caused by grid failures due to cyclones, tornadoes and other weather related issues, and localized distribution system with combined heat and power offers a better alternative. For those who are skeptical about global warming caused by man-made greenhouse gases the question still remains, “What happened to billions of tons of Caron dioxide emitted into the atmosphere by power plants and transportation since industrial revolution?”.

Thursday, July 19, 2012

Can Bio-gasification transform our world?

Carbon neutral biomass is becoming a potential alternative energy source for fossil fuels in our Carbon constrained economy. More and more waste –to-energy projects is implemented all over the world due to the availability of biomass on a larger scale; thanks to the increasing population and farming activities. New technological developments are taking place side by side to enhance the quality of Biogas for power generation. Distributed power generation using biogas is an ideal method for rural electrification especially, where grid power is unreliable or unavailable. Countries like India which is predominantly an agricultural country, requires steady power for irrigation as well as domestic power and fuel for her villages. Large quantity of biomass in the form of agriculture waste, animal wastes and domestic effluent from sewage treatment plants are readily available for generation of biogas. However, generation of biogas of specified quality is a critical factor in utilizing such large quantities of biomass. In fact, large quantity of biomass can be sensibly utilized for both power generations as well as for the production of value added chemicals, which are otherwise produced from fossil fuels, by simply integrating suitable technologies and methods depending upon the quantity and quality of biomass available at a specific location. Necessary technology is available to integrate biomass gasification plants with existing coal or oil based power plants as well as with chemical plants such as Methanol and Urea. By such integration, one can gradually change from fossil fuel economy to biofuel economy without incurring very large capital investments and infrastructural changes. For example, a coal or oil fired power plant can be easily integrated with a large scale biomass plant so that our dependency on coal or oil can be gradually eliminated. Generation of biogas using anaerobic digestion is a common method. But this method generates biogas with 60% Methane content only, and it has to be enriched to more than 95% Methane content and free from Sulfur compounds, so that it can substitute piped natural gas with high calorific value or LPG (liquefied petroleum gas). Several methods of biogas purification are available but chemical-free methods such as pressurized water absorption or cryogenic separation or hollow fiber membrane separation are preferred choices. The resulting purified biogas can be stored under pressure in tanks and supplied to each house through underground pipelines for heating and cooking. Small business and commercial establishments can generate their own power from this gas using spark-ignited reciprocating gas engines (lean burnt gas engines) or micro turbines or PAFCs (phosphoric acid fuel cells) and use the waste heat to air-condition their premises using absorption chillers. In tropical countries like India, such method of distributed power generation is absolutely necessary to eliminate blackouts and grid failures. By using this method, the rural population need not depend upon the state owned grid supplies but generate their own power and generate their own gas, and need not depend on the supply of rationed LPG cylinders for cooking. If the volume of Bio-methane gas is large enough, then it can also be liquefied into a liquified bio-methane gas (LBG) similar to LNG and LPG. The volume of bio-methane gas will be reduced by 600 times, on liquefaction. It can be distributed in small cryogenic cylinders and tanks just like a diesel fuel. The rural population can use this liquid bio-methane gas as a fuel for transportation like cars, trucks, buses, and farm equipments like tractors and even scooters and auto-rickshaws. Alternatively, large-scale biomass can be converted into syngas by gasification methods so that resulting biomass can be used as a fuel as well as raw materials to manufacture various chemicals. By gasification methods, the biomass can be converted into a syngas (a mixture of Hydrogen and Carbon monoxide) and free from sulfur and other contaminants. Syngas can be directly used for power generation using engines and gas turbines. Hydrogen rich syngas is a more value added product and serves not only as a fuel for power generation, but also for cooking, heating and cooling. A schematic flow diagram Fig 3, Fig4 and Fig 6 (Ref: Mitsubhisi Heavy Industries Review) shows how gasification of biomass to syngas can compete with existing fossil fuels for various applications such as for power generation, as a raw material for various chemical synthesis and as a fuel for cooking, heating and cooling and finally as a liquid fuel for transportation. Bio-gasification has a potential to transform our fossil fuel dependant world into Carbon-free world and to assist us to mitigate the global warming.

Tuesday, May 8, 2012

Power generation with Ammonia

Majority of current power generation technologies are based on thermodynamic principles of heat and work. Heat is generated by chemical reactions such as combustion of coal, oil or gas with air or pure oxygen. This heat of combustion is then converted into work by a reciprocating engine or steam turbine or gas turbine. The mechanical energy is converted into electrical energy in power generation and as a motive force in transportation. The fundamental principles remain the same irrespective of the efficiencies and sophistications we incorporated as we progressed. The efficiency of these systems hardly exceeds 30-40 of the heat input, while the remaining 60-70 heat is wasted. We were also able to utilize this waste heat and improved the efficiency of the system by way of CHP (combined heat and power) up to 80-85%.But this is possible only in situations where one can utilize both power and heat simultaneously. In a centralized power plant such large heat simply dissipated as a waste heat through cooling towers and in the flue gas. This is a huge loss of heat because a substantial portion of heat of combustion is simply vented into the atmosphere in the form of greenhouse gases. If ‘greenhouse gas’ and ‘Global warming’ were not issues of concern to the world, probably we would have continued our business as usual. Generation of heat by combustion of hydrocarbon is one example of a chemical reaction. In many chemical reactions, heat is either released or absorbed depending upon the type of reaction, whether it is exothermic or endothermic. Sometimes these chemical reactions are reversible. It may release heat while the reaction moves forward and it may absorb heat while it moves backward in the reverse direction. By selecting such reaction one can make use of such energy transformations to our advantages. One need not release the heat and then release the product of reaction into the air like burning fossil fuels. Ammonia is one such reaction. When Hydrogen and Nitrogen is reacted in presence of a catalyst under high temperature and pressure the reaction goes forward releasing a large amount of energy as practiced in industries using Heber’s process. The heat released by this reaction can be converted into steam and we can generate power using steam cycle. The resulting Ammonia can further be heated in presence of a catalyst by external heat due to endothermic nature of the reaction and split into Hydrogen and Nitrogen. However, such heat can be supplied only from external sources. One University in Australia is trying use the above principle by using solar thermal energy as a source of external heat. The advantage of this system is power can be generated without burning any fossil fuel or emitting any greenhouse gas. One can use renewable energy sources such as solar thermal and also use Ammonia as a storage medium. Ammonia is a potential source of energy to substitute fossil fuels. However, such Ammonia is currently synthesized using Hydrocarbon such as oil and gas. The source of Hydrogen is from synthesis gas resulting from steam reformation of a Hydrocarbon. Hydrogen can also be derived from water using electrolysis using renewable energy source. In both the above cases, renewable energy is the key, without which no Hydrogen can be produced without a Hydrocarbon or an external heat is supplied for splitting Ammonia. Ammonia can also be split into Hydrogen and Nitrogen using external heat. The resulting Hydrogen can be used to generate power using a Fuel cell or run a Fuel cell car. Nitrogen also has many industrial applications.Thereoefore Ammonia is a potential chemical that can substitute fossil fuels in the new emerging renewable economy.

Monday, April 9, 2012

Bioethanol fuel for Fuelcell cars

Bioethanol has successfully substituted Gasoline as a fuel for cars both in the form of blends with Gasoline or individually as an Anhydrous Ethanol. This successful demonstration by Brazil opens up new generation of cars called flex-fuel cars that allow usage of various blends of Ethanol and Gasoline.Bioethanol can also be used to generate Hydrogen onsite by steam reformation so that even Fuel cell cars such as Honda FCX can be felled by Bioethanol.This makes Bioethanol unique as an alternative fuel for transportation. It also facilitates onsite power generation using Fuel cell, replacing diesel engines. Substitution of Gasoline by Bioethanol has several advantages over other alternative fuels. The biggest advantage with Bioethanol is, it is renewable and it allows reduction of greenhouse gases from the atmosphere and it will be eligible for Carbon credit. It can be produced by both developing as well as developed countries using locally available agriculture produces such as cane sugar, corn, tapiaco, sorghum etc. Hydrogen generated from Bioethanol is also free from Sulfur compounds normally associated with natural gas, making it an ideal fuel for Fuel cell application in cars, as well as for power generation using SOFC (solid oxide Fuel cell) or PAFC (Phosphoric acid Fuel cell).The resulting high purity Hydrogen 99.99% can be used as fuel for all type of transportation including Fuel cell Buses, scooters and even boats. The stoichometric reaction of steam reformation in presence of catalyst can be represented by the following chemical reaction: C2H5OH + 3 H2O---------- 6H2 + 2 CO2 The Ethanol and water mixture is preheated and the vaporized mixture is fed into a catalytic reactor. The resulting Hydrogen is contaminated with carbon monoxide. This gas mixture is separated using membrane such as Palladium to get Hydrogen with less than 50ppm CO as contaminant. Such purity is acceptable by Fuel cell such as SOFC as well as PAFC.In future a small micro-reactor for on-board reformation may be possible making Fuel cell cars with onboard liquid fuel storage. Commercial reformers consumes about 0.88 lits of Bioethanol of 96% purity to generate 1 Nm3 of Hydrogen with 60% conversion. This translates to $ 5.90 per Kg of Hydrogen. Fuel cell cars offer a mileage of 240 from 1 kg Hydrogen costing only $5.90. For onsite power generation 1 kg Hydrogen generates as much as 15Kw electricity and 20Kw heat .Onsite Hydrogen generation with steam reformation also facilitates using SOFC and PAFC for high temperature power generation applications. They are ideal for CHP (combined heat and power) applications for 24x7 operations like hospitals, hotels and super markets. These fuel cells are silent in operation without any emissions except water vapor. Governments should encourage Bioethanol production and distribution for both transportation and power generation. There is a fear that Ethanol could be diverted for potable purposes illegally depriving Governments of potential reveneues.But this can be solved by denaturing Bioethanol and making it unsuitable for potable purposes. Denaturants such Pyridine has no effect on steam reformation and number of denaturants are available. Such policies will allow transition from fossil fuels to Hydrogen or Bioethanol.This is a simple and straight forward step any Government can take irrespective of the size or type of a nation. But it requires political will, determination and leadership. Developing countries need not wait for big greenhouse emitters such as US, China and India to make a decision on their Carbon emissions but start introducing Bioethanol as fuel locally.

Monday, March 12, 2012

Air-condition your premises with engine exhaust and solar hot water

Do you use a generator that runs on diesel or gas to power your business due to frequent power outage from the grid? Are you running an air-conditioner with the grid power? Then you must look for waste heat recovery system to improve your energy efficiency and save your fuel cost. You can also use roof top solar hot water to supplement waste heat recovery. The savings may be substantial and you may be able to recover your investment in a short period of time and also contribute for the reduction of greenhouse emissions. The diesel or gas engine converts only maximum 30% of fuel input in the form of thermal energy into mechanical energy to run your generator, and the balance heat is wasted in the form of greenhouse gas. You can recover this heat and increase the efficiency of the system. This means for the same amount of diesel used, you will get much higher output in the form of heating or cooling or in the form of additional electricity. The exhaust temperature from a gas engine is about 420C.You can also recover additional heat from jacket cooling. Let us assume that you have a natural gas fired engine to generate 100kw electricity for the premises. The efficiency of such spark ignited reciprocating gas engines are typically about 30%, which means a natural gas input of 1.145 mm Btu/hr. Let us assume the cost of piped natural gas at $10 per mm Btu; the fuel cost will be about $ 11.45/hr. The exhaust heat from the engine will be about 801,500 Btu/hr; with waste heat recovery efficiency at 75%, the heat recovery will be 601,125 Btu/hr.You can air-condition premises with an area of 35-40 square meters using this recovered waste heat. If you use grid power at the rate of $0.10/kwhr, to run the air conditioning system for the above area, you will be spending about 30,000kwhrs of electricity per month, costing about $ 3000 per month. By installing an absorption chiller to air-condition your premises using engine exhaust heat, you will be saving about $36,000 per year towards air-conditioning. The air-conditioning system may cost about $130,000, and with the above savings you will be able to get a return on your investment in less than 3 years. If you have a roof-top solar water heater then you can supplement it with your engine exhaust heat water so that the capacity of the air-conditioning can be increased. It is one of the best methods by which an energy efficiency of a fossil felled engine can be increased. If the capacity of the engine is much higher, there are other methods by which the efficiency can be increased. For example, the hot water from the exhaust system can be used to generate some extra power using an ORC, organic Rankin cycle. It is similar to a steam turbine. An organic liquid with low boiling point will be evaporated into vapor by a low heat source such as hot water from engine exhaust, which runs a turbine, generating some additional power and condensing back into the liquid, and then the cycle continues. You will be able to generate an additional electricity of about 15-18% making the total electrical efficiency of the system to 45-50%, which is similar to a Fuel cell system, but at a much lower cost. Heat recovery system with an absorption chilling and using low heat source to generate additional power using ORC, are best methods to improve energy efficiency of an existing system with little investment. The purpose of such integration is to increase the energy efficiency of the existing system, so that you will be getting more output of energy from the same input of fuel.