Renewable Energy Resources - Dissertation Example

Harris Kamran Renewable Energy Resources 27 August 2007 Renewable Biomass Energy for Domestic Utilisation Introduction: Biomass is a collective name for fuels with organic sources. Renewable biomass fuels include wood and bark of trees, which is the most common source, wood chips, crops, grasses, plant waste material, animal waste material such as cow dung, and the by-products and refined products from biomass treatment and utilisation. Fossil fuels, though having organic origin, are not included in the list as they are not renewable. All the organic material constituting biomass can be used to produce energy. The fuel could be in solid state, or in liquid or gaseous form, and the resulting energy could be electricity, heat or a combination of the two, depending upon the nature of the fuel and the energy needs. Utilisation of biomass for harnessing energy is a common trend that is growing as new methods for energy extraction are developing. In UK, the supply of biomass is limited. With the growth of the building industry, the demand of biomass energy is increasing, and hence, there is a need for an import of biomass in accordance with certain regulatory clauses. Constant effort is being made for a high quality and cost-effective import and utilization. Nevertheless, UK is the leading country in the sector of biomass consumption for the production of energy, especially for use in the building sector, in Europe. The Two-Stage Process: Harnessing the biomass energy is a two stage process. The first stage is the conversion of solar energy into chemical energy that is stored in the various fuels used to produce biomass energy. This conversion takes place during photosynthesis. 1/10 of the solar energy incident on earth is stored as bio-energy, and out of this, 90% is stored in the wood of the trees, hence, making it the most common biofuel in the building sector. The key point here is to note that this stage removes carbon dioxide from the atmosphere, hence decreasing the amount of the greenhouse gas. No other renewable energy source has this feature to it. The second stage is the utilisation of this stored chemical energy. There are various methods to do so (described later), but the key point to be noted here is that at this stage, carbon dioxide is released back into the environment. Although some other renewable sources do not release the greenhouse gas and so might seem as “cleaner” sources for the production of energy in the building sector, it should be appreciated that this release is neutralised by the consumption of carbon dioxide in the first stage, and so the net production of the gas is zero. Infact, if the harnessing of biomass energy is schematically carried out, and the sources outnumber the consumption figure, there can actually be a net decrease in the greenhouse gas_ a feature not enjoyed by any other renewable energy source. Feasibility and Benefits: 60% of the total bioenergy present is in the form of biomass which is used most commonly in combustion to release the stored energy (other forms of bioenergy include plants customised to produce other forms of energy sources, such as hydrogen, that are highly valuable in the building and the industrial sector). One of the most feasible forms of renewable energy sources, especially for domestic and small-scale use, biomass has widespread utilisation in domestic and industrial energy supplies. Biogenic fuel sources are excellent stores of solar energy, and the only form of renewable energy that, when used on a domestic level, meet the supply-demand ratio, and more than often exceed the demand of a particular residential or industrial setup, resulting in a surplus of energy that can be used elsewhere on location and so actually cut down the cost of energy consumption (wood, for example, stores 90% of the incident solar energy). These fuel sources have the advantage of local, on-location harnessing; they can be grown locally and then utilised locally through on the spot combustion and treatment plants. This means that there is no need for heavy, long-distance transportation, hence being cost effective, and no hassle of remote energy supplies and the ensuing energy losses. In cases of transportation, the low density and durable nature of biomass and its bioproducts means a reduction in the transportation cost and an ease of conveyance. Local disposal of organic waste thus carried out releases the pressure on landfills and commercial incineration plants, cutting down on atmospheric pollution and providing an economical and energy-rich method of waste disposal. Coal, a non-renewable biofuel, is widely used in thermal power stations for the production of electricity for domestic and industrial purposes. However, it results in great emissions of the greenhouse gases, including carbon dioxide and methane, and pollutants such as nitrogen and sulphur compounds. To counter this menace, a method has been developed in which coal is cofired with biomass and natural gas (a by-product of biomass treatment). This not only cuts down heavily on the emission of greenhouse gasses, but also reduces the production of nitrogenous and sulphuric pollutants to within the limit set by the Koyoto Protocol, especially when using modern furnaces and combustion units, hence making thermal power production both safe and clean. That is the reason that UK endeavors to raise the amount of biomass energy for domestic heating and utilisation, which forms 30% of the total energy consumption, to 10% of the total demand by 2010 . Also, with the improvement in the treatment units, the benefits of biomass are expected to triple by 2010 (Juniper 2007). Comparison with other Non-Renewable Energy Sources: Biomass energy has many advantages over other non-renewable energy sources. The most glaring one is that it is the most cost effective and the most efficient energy source that meets the energy demands in the most effective way. The determining factor in installing any environment friendly energy source is its feasibility to install it on a micro setup (that is, domestically and in the building sector). Whereas all non- renewable energy sources are sufficiently “clean”, not all of them are suitable to be established on small scale. This could be due to reasons varying from high installation costs to considerable environmental damage. Solar water heating systems, for instance, if used on a domestic scale, are not cost effective and do not completely meet the energy demands for heating in the UK. Same is the case with ground source heat pumps. Although these pumps remove heat from the ground to provide heating for the house, they themselves run on electricity, and hence, the total cost of installation overshadows the savings. Another factor to be considered is the percentage of efficiency for various non-renewable energy sources. These percentages, in turn, determine if the net benefits of a source outweigh its cons. Photovoltaic cells, for one, have been under a lot of research and development, especially since the prices of oil have risen sharply in recent years. They are extensively used for satellites and other outer space crafts for their reliability and light weight. However, when used domestically, they never turn out to be cost effective and almost never meet the energy demands, for instance in UK, where the incident solar energy that is harnessed in these cells is only sufficient enough in summers for these cells to function at their maximum capacity, a time when the domestic heating demands are at their lowest. Apart from this, these cells have only recently improved their efficiency, working now at a percentage of 24% (Juniper 2007) that is far from feasible for domestic purposes. Generally, all the non-renewable energy sources, other than biomass, are just used for the production of electricity. However, this is not an ideal case as electricity demand forms only one-quarter of the total domestic energy demands in the UK. The other demands include energy for water heating and space heating which are not carried out by the use of electricity, but these energy sources either do not provide for these demands at all, or provide very unfeasible and inefficient alternatives which rarely meet the total demands. Electricity in itself, if used for these other purposes, is not a very efficient source, as, when produced through commercial methods, such as thermal power production, it is only a little more efficient than the photovoltaic cells themselves. On the other hand, its production through these methods produces far more environmental pollutants than balanced by its effectiveness. Also, their are considerable transmission losses when electricity through these plants is supplied to remote areas, letting alone the high costs of installing and maintaining these supply lines. Electricity production through nuclear power is an alternative for electricity production in thermal plants, but this alternative is not cost effective as the construction and installation costs of nuclear power plants are very high, and considering all the other regulations that have to be abided by for running these plants, their utilisation in the domestic sector remains almost non-existent as compared to the conventional methods of electricity production. Biomass energy, on the other hand, provides solutions to many of the problems faced by other sources of non-renewable energy. To begin with, it is the only source of energy which can be most cost effectively set up at micro levels in the building sector and be used for domestic purposes. The installation costs are very low and it provided more than sufficient energy to meet domestic demands, at all times. As biomass, such as biofuel crops and organic wastes are produced on the location, and treated for energy extraction on the same location, there are no long distance supply problems associated with it as are with the transmission of electricity. This solves the problem of transmission losses and cuts down heavily on unnecessary transportation expenses. Energy loss is also minimised through its very high percentage of efficiency, which rises well above even that of electricity production. This not only makes it a clean and environment friendly energy source, which can be safely used in buildings and domestically (excess release of heat energy into the environment, as by heat energy losses, is considered to be environmental pollution), but hence, also makes it a very economical source of energy as well. Biomass energy can perform a dual function; it can be used for the production of electricity either alone, or in combination with the conventional fuels, and it can also be used directly in the residential areas to provide for other energy uses that are not provided by electricity. When co-used with coal and natural gas, it not only improves the efficiency of the thermal power plants, but also cuts down on the production of air pollutants. This electricity is used to meet a fraction of the total energy demands in the building sector in UK. The rest of the energy demands are for heating purposes, and here too, biomass energy is and can be used successfully. Local boilers and heaters, and private energy producing units can be easily setup domestically, which run on wood pellets or cow dung. The modern units are very efficient and clean. This is year-round source of energy that does not depend on weather conditions or other external factors to meet demands. By setting up local units of energy production (even local units for the production of electricity can be set up with minimal costs), a lot of pressure is relieved from the central grid stations that supply electricity to vast areas and remote locations. This independence results not only in improved production and efficient supply, but also cuts down on supply costs and environmental damage. Biomass energy can be used in so many alternative ways to meet domestic needs. There are suggestions to use biomass as fuel in oil refineries instead of coal. The refined oil and its products find multiple uses domestically and in the building sector, along with reducing the costs of oil refining and the production of special car engines that are designed to run on liquid biofuels. Also, biomass, especially trees and crops, are being designed to produce hydrogen gas that can the be used in hydrogen cells to produce electricity for domestic purposes, with a manifold increase in supply and zero pollution. Biomass is the only energy source that can actually be used to reduce the existent pollution levels and bring them down through a positive feedback mechanism. For that, however, a proper framework for harvesting this energy is required, and generally, the production of biofuel crops should be much more in amount than the utilisation. Methods of Extraction: as described before, biomass is a store of chemical energy, and this energy needs to be extracted and converted to more useful forms of energies if it is to be used for domestic purposes and in the building sector. There are many different methods for this extraction, depending upon the nature of the demand, and the cost of treatment, and result in the production of different by-products and biofules. Combustion: the most widely used method of energy extraction is through direct combustion of biomass. This involves simply burning the stock in the presence of oxygen to release heat energy that is used in domestic boilers to warm water. This warm water could then be directly utilised or be used for space heating. Logs, wood pellets, cow dung, and dry stocks of grasses are the most common fuels used in combustion process. This method is the most cost effective method, as it involves no refinement or sub-processes, and the fuels can directly be used wherever they are grown or produced, therefore, cutting down on transportation costs. The improved boilers and combustion units have increased its efficiency and have resulted in less release of greenhouse gases. Dual Production: if the above mentioned fuels are used not just for the production of heat, as in boilers, but in units designed to produce heat and electricity together, this method is know as dual production or cogeneration. This is, obviously, a better utilisation of biomass, and hence is also very economical. Although the installation costs of dual units is higher than the simple boilers, in the long run, these units cut down on domestic bills, as they not only provide space heating, but also fulfill some demands of electricity. It should be noted that this method can only be fully harnessed on a macro level setup, such as local electricity production plants, or thermal power stations, where electricity is produced on a commercial scale, and which can be dually used for the production of hot water that can then be transported over to the residential area for heating and utilisaton, albeit the transmission costs and losses. On a domestic scale, it has only limited use as regards the production of electricity. Anaerobic Digestion: it is the mechanical and natural degradation of biomass in the absence of oxygen in tanks called digesters. These tanks can be set up domestically with low expenses, and are simple to operate and run as no additional procedures have to be carried out. Biomass such as sewage, organic wastes from the kitchen, and animal wastes are mixed with water and left standing in the digesters for a few weeks. This results in the production of methane and carbon dioxide. Both are greenhouse gases. Carbon dioxide is released into the atmosphere where it is reused in the first stage of biomass production, as described above. Methane is piped from the digesters into cylinders where it is stored and used for cooking, heating and also in boilers for getting warm water. As methane is a major component of natural gas, this method of extraction results in the production of natural gas, a gaseous biofuel. Syngas, a mixture of carbon monoxide and hydrogen might also be produced as a by- product, but has minimal domestic use. Alcoholic Fermentation: biomass containing carbohydrates, such as starch, cellulose or other sugars, can be degenerated in specially designed digesters to produce a liquid biofuel called alcohol. Stock such as grasses, vegetables like potatoes, kitchen organic waste, waste paper, wood, wheat and straw are mixed with enzymes from yeast, and stored in the digesters over weeks to allow the enzymes to convert the carbohydrates into simple sugars, and the sugars into alcohol. This, too, is an anaerobic process. Carbon dioxide is given off as a by- product that is released into the atmosphere. The alcohol so produced has to be first separated from the water produced in the process before it can be used. This is achieved by distillation, a process that requires the use of heat to boil off alcohol. The vaporised alcohol is cooled, stored in tanks and used as fuel for burning and heating, and may also be used in special boilers to produce hot water. This method involves higher installation costs and more effort for its operation, but results in the production of a liquid biofuel that has multiple uses. Pyrolysis: it involves heating biomass anaerobically over high temperatures to convert it into more useful biofuels. Wood pellets, plant remains and wood products are subjected to high temperatures in the absence of oxygen in special thermal units. This results in the formation of methane, liquid fuels and charcoal. These fuels are then separated and used for many various purposes domestically, with minimal by products that need to be given off into the atmosphere as waste. Although it is relatively a little expensive, as high temperatures have to be provided and the products separated from each other, it comes to be very cost effective in the long run, as the many different fuels that are produced find many different uses domestically, and fulfill energy demands in many ways. As very little waste gases or solid or liquid waste is produced, it is also relatively much cleaner process, and more environment friendly. Landfills: if domestic units are not set up, the organic waste can be collected and buried in sites away from the residential area, known as landfill sites. There, the buried garbage is naturally degenerated to produce gaseous biofuels such as methane. This gas is then collected and transmitted through pipes to the residential area where it is used for cooking, heating and for running the water boilers. This method is not very cost effective as there are many expenses involved, such as those for collection of garbage, transportation, maintenance of the landfills, collection of the gas and its transmission. The landfills also become saturated and so have to be closed, and new sites have to be searched for and developed which involved further costs. Domestic Applications and Case Study: the utilisation of biomass and its applications vary greatly, and depend upon many factors such as the nature of the demand, the appliances, the location, the type and availability of fuel and the financial investment, to name a few. These factors not only determine the degree of biomass usefulness, but also the nature and amount of products that need to be extracted from it. These products may be in the form of direct energy for residential or industrial usage, or the further processing of the released energy to produce goods and services, such as in farms and thermal power plants. The aim of this case study is to examine the possibilities of the utilisation of biomass at domestic level. A 3 bedroom house/apartment has been selected for this investigation, and the following discussion would determine the figurative energy needs of the house, and the use of appropriate bioenergy appliances and fuels for the selected location. Before proceeding, however, there needs to be an appraisal of certain general factors that have to be taken into consideration whenever biomass based appliances have to be installed in a building, regardless of the size and the type of the building, the appliance, and the fuel. Biomass based appliances require to be externally heated, hence, the user must abide by all the safety regulations concerning the pertinent building and the usage of these appliances as determined by the fire safety regulation authorities. Likewise, the appliances used must be listed as exempted appliances; this means that the usage of direct flame in those machines should be allowed by the law. The rooms where these machines are kept should be properly aerated and ventilated, and the vent or the chimney should be lined by flue to reduce any air pollution caused by their usage. Proper aeration is also beneficial in the optimum functioning of these appliances. To further cut down on any waste generation, it is advisable to use upgraded, improved versions of these machines. As concerning the fuel, there should be a proper storage space for it and a local supplier or supply of the fuel. For refueling the appliances, proper and easy access should be available to the appliances, which in turn should be installed at appropriate locations in the building. It should be borne in mind that bioenergy is the only form of renewable energy that requires the user to pay for the fuel, unlike other forms of renewable energy resources that can be used on a domestic level. The fuel type that is available depends upon the location of the building. The most common fuel used is derived from willow trees. However, in the temperate regions of UK, grasses, rye, barley, straw and even weeds are in great demand. It is important to know the average energy demands of the building in order to install appropriate sized biomass based appliances to meet those demands. This is because generally the size of these machines is linked with their maximum energy generation capacity, or in other words, their output per kilowatt of energy produced. This in turn determines their net cost, including their installation expenses and the costs of the fuel that they require. For this purpose, certain softwares have been developed that calculate the total energy demands of the building when certain data is entered, and hence, the type and size of the appliance can then be determined. One such software is the On-Line Calculator v2.4 developed by SolarScript©. This calculator enables the user to calculate energy demands in terms of solar power, which can then be changed into the amount of energy generation required by the bioenergy using machine. It has several options for calculations depending upon the voltage required by the household appliances. The following data needs to be entered: a) the quantity of the appliances b) power required in terms of watts c) the number of hours that they are used in the timeframe that the energy is being calculated for d) the watt-hours per appliance Upon automatic calculation, the following data would be made available by the software: a) total connected watts b) total watt-hours c) peak dc current draw d) total dc amp-hours (SolarScript© 2007) By using these calculations, it has been estimated that a 3 bedroom house/apartment would require a biomass based appliance that has an energy output of 15-20 kW to fully furnish the energy demands of the building. Two kinds of appliances can be used for the given location, namely stoves (also called stand alone stoves) and boilers. Stoves have an energy output of less than 15kW, and hence, are suitable for a one room setup, such as cooking. Slightly bigger stoves can have a boiler attached to them. This is a miniature boiler called a back boiler, that is used to utilise the extra energy produce by the stove for water heating and space heating. The fuels used for stoves come as logs or pellets. Log fed stoves have to be refueled manually and so are cheaper than pellet fed stoves that usually have an automatic system for refueling, and although easier to use, are more expensive than the former kinds of stoves. However, stoves, if used for the entire house cannot fully provide for the energy demands, and so are mostly used for one room setups. Boilers, on the other hand, are larger machines that have an energy output greater than the stoves. The boilers that should be used for the pertinent location should be medium sized boilers which have an energy output of more than 15kW. These boilers come in many makings, and are generally characterised by the kind of fuel being used. The wood-fed boilers, also known as wood gasifier boilers, may be run on logs, chips or pellets. Log-fed boilers are cheaper than the other two types because they have to refueled manually. However, chips-fed and pellet-fed boilers are easier to use. Wood-fed boilers are used where there is a relatively less energy demand. They are easy to use, cost effective and clean. Moreover, they produce wood ash as a by-product that serves as an excellent fertiliser for plants. The water cooled metal walled wood boilers need good wood for fueling that is more expensive than poor quality wood that can be used as a fuel in the boilers whose walls are ceramic-lined. On the other hand, the straw gas heated units, straw whole-bale units, and straw steam engines, that run on straw as their fuel, are used where energy demands are relatively higher. For all kinds of biomass based appliances, the over all efficiency and hence, the amount of fuel used also depends upon the system of ventilation of the room. Works Cited Biomass. Energy Saving Trust. 29 August 2007. http://www.energysavingtrust.org.uk/generate_your_own_energy/types_of_renewables/biomass/ Biomass. The National Energy Foundation. 27 August 2007. Biomass and its Applications. German Biomass Energy Solutions. 27 August 2007. Biomass and Renewable Fuels. 30 August 2002. Science Direct. 26 August 2007. Biomass Heating-FAQ. June 2006. Sundance. 27 August 2007. Biomass Renewables. Juniper. 27 August 2007. Gerhard Faninger. 28 November 2000. Science Direct. 28 August 2007. HERLT HSV: the whole-bale gasifiers. HERLT HSV. 28 August 2007. I.M. Smith. ACTA Press. 30 August 2007. On-line Calculator v2.4. 28 August 2007. Solar Mike’s Web Site. 30 August 2007. Other Renewable Technologies: debunking the myths. Organic Energy. 29 August 2007. Renewable Energy: Biomass Energy. June 2001. Young People’s Trust for the Environment. 30 August 2007. Whole Strawable Gasifiers. HERLT HSV. 28 August 2007. Why heat With Wood Gasifier Boilers. HERLT HSV. 28 August 2007. Wood Gasifier Heating Boilers. HERLT HSV. 28 August 2207. Read More