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Design and off design pipe network geothermal power plant analysis with power pipe simulator
07
Alternative
energy
sources
(solar
energy)
The energy balance and COz mitigating effect of a liquid fuel production process from microalgae using thermochemical liquefaction were studied. Thermochemical liqufaction does not require a drying process, therefore, it is far better at treating wet materials in comparison to direct combustion, pyrolysis and gasification. The yield of liquid fuel produced from Borryococcus braunii and its lower heating value were high compared with those of Dunaliella tertiolecta; therefore, the energy inputs for cultivation and separation of B. braunii were calculated to be smaller than those of D. fertiolecta. The energy input for fertilizers of B. braunii was also smaller than that of D. rertio[ecra. Based on these differences, the liquefaction process using E. braunii was suggested to produce net renewable energy, but not that with D. tertiofecta. If a 100 MW thermal plant, using coal would be replaced by liquid fuel produced from B. braunii, the quantity of COz mitigation could be 1.5~10’ tons/yr and 8.4~10~ ha of microalgal cultivation area could be necessary.
OOlOO366 Prediction of the behaviour of biomass ash in fluidized bed combustors and gasifiers Arvelakis, S. et al. J. Therm. Anal. Calorim., 1999, 56, (3), 1271-1278. Two types of agricultural residues, wheat straw and olive residue in an untreated and pretreated form were investigated because of concerns about their ash melting behaviour during fluidized bed combustion and gasification by thermal analytical techniques. The techniques employed included differential scanning calorimetry, simultaneous differential scanning calorimetry /thermogravimetric analysis, and thermogravimetric analysis-mass spectroscopy for the detection of low-temperature ash melts and losses caused by the volatilization of alkali material. In combination with ash elemental analyses on the materials, the applied techniques seemed to provide valuable information for prediction of the ash behavior in fluidized bed reactors.
00100369 Studies of the Brazilian sugarcane bagasse carbonisation process and products properties Zandersons, J. er al. Biomass Bioenergy, 1999, 17, (3), 209.-219. Laboratory-scale experiments performed in an enlarged scale thermoreactor have demonstrated that the pyrolysis of the bagasse bulk in a mechanical loosened layer yields 23-28% charcoal measured on an oven dry basis. The charcoal is ideal for producing fuel briquettes and granules for household and industry uses. To implement an energy selfsufficient production process, yields of condensable matter and gas components were detected. It is shown that their combined heat of combustion exceeds the upper limit of the heat necessary to carbonize the biomass by 1.6-1.8 times. To overcome the difficulties caused by a high fine particles content and the fibrous structure of bagasse, the use of a rotary drum apparatus is suggested. Owing to technological considerations, it was recommended to use a two-stage process: a heating and pyrolysis stage up to 350°C and a charcoal glowing stage with the peak temperature 475-500°C. Such a reactor unit with a joint furnace and closed pyroligneous vapour and heat carrier flow system greatly reduces the emission of carbon monoxide (CO) and dust particles. Bagasse can be used as an alternative source of traditional wood for the production of charcoal. Consequently, the deforestation of native forests could be prevented.
00100370
The Evritania (Greece) demonstration plant of biomass pyrolysis
Zabaniotou, A. A. and Karabelas, A. J. Biomass Bioenergy, 1999, 16, (6) 431-445. This paper is focused on describing the Evritania demonstration plant for pyrolysis of forestry biomass. This plant was constructed in the village of Voulpi, district of Evritania, in Central Greece, in 1995, with a threefold purpose; development of know-how, forest fire prevention and rural development. The products are charcoal and bio-oil. The plant capacity is 1200-1450 kg/h of wet biomass and the pyrolysis temperature is approximately 400”. The raw material used is Arbutus unedo, which is an evergreen broad-leaf tree that covers the area. Other agricultural waste could also be used, such as olive pits and cuttings, almond shells and cotton kernels. The paper includes the conceptual process flow sheet, the changes and improvements made during the trial phase, data from the start-up phase and product characteristics. Comparison of the process with the Alten process is presented. In addition, comparisons are made of product characteristics with those from other pyrolysis processes. In general, the results obtained are encouraging even though several improvements of the pilot plant are required. 36
Fuel and Energy Abstracts
January 2001
Geothermal energy 00100371 Design and off design pipe network geothermal power plant analysis with power pipe simulator Di Maria, F. Energy Convers. Manage., 2000, 41, (12) 1223-1235. One of the biggest problems when analysing pipe network behaviour is the difficulty in accounting for the actual components features, as some conditions change in relation to the designed one. This problem occurs, for example, when some power machines, like turbines or pumps, are connected to the pipes. In fact, for these devices, one flow rate value corresponds to each pressure value and vice versa. For this reason, the pipe network operating points depend on both pipe geometry and the physical behaviour of the other components. Furthermore, when hot and multi-component fluids are considered, thermal loss and composition calculations are required to correctly evaluate pipe behaviour. In the following, a simulation code developed by the author (Power Pipe) has been applied to a real geothermal power plant in which the wells can be considered as expanders and the power unit is a steam turbine plant. Design and off design analyses have been performed by accounting for the exergetic loss of the system components.
Solar energy 00100372 A CFD heat transfer analysis of the transpired solar collector under no-wind conditions Arulanandam, S. J. et al. Solar Energy, 1999, 67, (l-3), 93-100. The unglazed transpired solar collector is now a well-recognised solar air heater for heating outside air directly. Example applications include pre-heating ventilation air and heating air for crop drying. The outside air in question is sucked straight from ambient, uniformly through the whole surface of a perforated blackened plate (the absorber plate) exposed to the sun. An important parameter fixing the collector’s efficiency is the heat exchange effectiveness, e. Once e is known, finding the collector efficiency is straight-forward. The effectiveness depends on the wind speed, the suction velocity and the plate geometry. This paper is about determining this effectiveness by computational fluid mechanics (CFD), for conditions of no wind. Because of symmetry, the computational domain needed only to extend over a representative element, which included one hole and the region immediately adjacent to it extending to half the distance between holes. Simulations were carried out over a wide range of conditions, and the results are incorporated into a correlation model. Because of the no-wind assumptions, the model is of limited direct use, but when combined with experimental data, the model can permit a wider-ranging correlation equation to be obtained. 00100373
A multistage solar receiver: the route to high
temperature Kribus, A. er al. Solar Energy, 1999, 67, (l-3). 3-11. A high-temperature solar thermal recetver is subject to temperaturedependent emission and convection losses. Minimizing these losses is essential to realization of high temperature, high efficiency systems. Dividing the aperture into separate stages according to the irradiance distribution has been shown theoretically to significantly reduce these losses. In such a partitioned system, the working fluid is gradually heated as it passes through a sequence of receiver elements with increasing irradiance levels. An experiment to demonstrate this principle using two heating stages has been constructed at the Weizmann Institute’s Solar Tower. The high-temperature receiver stage is the Directly Irradiated Annular Pressurized Receiver (DIAPR). The low-temperature stage is implemented as a partial ring of intermediate-temperature cavity tubular receivers (Preheaters) surrounding the central high-temperature stage. Following initial concentration by a part of the Weizmann Institute heliostat field, the light enters the receivers via secondary concentrators constructed as approximate CPCs. We present recent test results with the two-stage system. Air exit temperatures of up to 1000°C were obtained, with the low-temperature stage supplying up to 750°C. The power output was up to 55 kW,t,. Heat transfer in the high-temperature receiver, losses due to the partitioning and future plans for partitioned receivers are discussed.
Accelerated life testing of solar absorber coatings: testing procedure and results
00100374
Brunold, S. et al. Solar Energy, 2000, 68, (4), 313-323. A procedure for accelerated life testing of solar absorber surfaces was developed within the framework of the working group MSTC (materials in solar thermal collecrors) of the IEA-SHCP (International Energy Agency-solar heating and cooling programme). The intensive
Alternative
energy
sources
(solar
energy)
The energy balance and COz mitigating effect of a liquid fuel production process from microalgae using thermochemical liquefaction were studied. Thermochemical liqufaction does not require a drying process, therefore, it is far better at treating wet materials in comparison to direct combustion, pyrolysis and gasification. The yield of liquid fuel produced from Borryococcus braunii and its lower heating value were high compared with those of Dunaliella tertiolecta; therefore, the energy inputs for cultivation and separation of B. braunii were calculated to be smaller than those of D. fertiolecta. The energy input for fertilizers of B. braunii was also smaller than that of D. rertio[ecra. Based on these differences, the liquefaction process using E. braunii was suggested to produce net renewable energy, but not that with D. tertiofecta. If a 100 MW thermal plant, using coal would be replaced by liquid fuel produced from B. braunii, the quantity of COz mitigation could be 1.5~10’ tons/yr and 8.4~10~ ha of microalgal cultivation area could be necessary.
OOlOO366 Prediction of the behaviour of biomass ash in fluidized bed combustors and gasifiers Arvelakis, S. et al. J. Therm. Anal. Calorim., 1999, 56, (3), 1271-1278. Two types of agricultural residues, wheat straw and olive residue in an untreated and pretreated form were investigated because of concerns about their ash melting behaviour during fluidized bed combustion and gasification by thermal analytical techniques. The techniques employed included differential scanning calorimetry, simultaneous differential scanning calorimetry /thermogravimetric analysis, and thermogravimetric analysis-mass spectroscopy for the detection of low-temperature ash melts and losses caused by the volatilization of alkali material. In combination with ash elemental analyses on the materials, the applied techniques seemed to provide valuable information for prediction of the ash behavior in fluidized bed reactors.
00100369 Studies of the Brazilian sugarcane bagasse carbonisation process and products properties Zandersons, J. er al. Biomass Bioenergy, 1999, 17, (3), 209.-219. Laboratory-scale experiments performed in an enlarged scale thermoreactor have demonstrated that the pyrolysis of the bagasse bulk in a mechanical loosened layer yields 23-28% charcoal measured on an oven dry basis. The charcoal is ideal for producing fuel briquettes and granules for household and industry uses. To implement an energy selfsufficient production process, yields of condensable matter and gas components were detected. It is shown that their combined heat of combustion exceeds the upper limit of the heat necessary to carbonize the biomass by 1.6-1.8 times. To overcome the difficulties caused by a high fine particles content and the fibrous structure of bagasse, the use of a rotary drum apparatus is suggested. Owing to technological considerations, it was recommended to use a two-stage process: a heating and pyrolysis stage up to 350°C and a charcoal glowing stage with the peak temperature 475-500°C. Such a reactor unit with a joint furnace and closed pyroligneous vapour and heat carrier flow system greatly reduces the emission of carbon monoxide (CO) and dust particles. Bagasse can be used as an alternative source of traditional wood for the production of charcoal. Consequently, the deforestation of native forests could be prevented.
00100370
The Evritania (Greece) demonstration plant of biomass pyrolysis
Zabaniotou, A. A. and Karabelas, A. J. Biomass Bioenergy, 1999, 16, (6) 431-445. This paper is focused on describing the Evritania demonstration plant for pyrolysis of forestry biomass. This plant was constructed in the village of Voulpi, district of Evritania, in Central Greece, in 1995, with a threefold purpose; development of know-how, forest fire prevention and rural development. The products are charcoal and bio-oil. The plant capacity is 1200-1450 kg/h of wet biomass and the pyrolysis temperature is approximately 400”. The raw material used is Arbutus unedo, which is an evergreen broad-leaf tree that covers the area. Other agricultural waste could also be used, such as olive pits and cuttings, almond shells and cotton kernels. The paper includes the conceptual process flow sheet, the changes and improvements made during the trial phase, data from the start-up phase and product characteristics. Comparison of the process with the Alten process is presented. In addition, comparisons are made of product characteristics with those from other pyrolysis processes. In general, the results obtained are encouraging even though several improvements of the pilot plant are required. 36
Fuel and Energy Abstracts
January 2001
Geothermal energy 00100371 Design and off design pipe network geothermal power plant analysis with power pipe simulator Di Maria, F. Energy Convers. Manage., 2000, 41, (12) 1223-1235. One of the biggest problems when analysing pipe network behaviour is the difficulty in accounting for the actual components features, as some conditions change in relation to the designed one. This problem occurs, for example, when some power machines, like turbines or pumps, are connected to the pipes. In fact, for these devices, one flow rate value corresponds to each pressure value and vice versa. For this reason, the pipe network operating points depend on both pipe geometry and the physical behaviour of the other components. Furthermore, when hot and multi-component fluids are considered, thermal loss and composition calculations are required to correctly evaluate pipe behaviour. In the following, a simulation code developed by the author (Power Pipe) has been applied to a real geothermal power plant in which the wells can be considered as expanders and the power unit is a steam turbine plant. Design and off design analyses have been performed by accounting for the exergetic loss of the system components.
Solar energy 00100372 A CFD heat transfer analysis of the transpired solar collector under no-wind conditions Arulanandam, S. J. et al. Solar Energy, 1999, 67, (l-3), 93-100. The unglazed transpired solar collector is now a well-recognised solar air heater for heating outside air directly. Example applications include pre-heating ventilation air and heating air for crop drying. The outside air in question is sucked straight from ambient, uniformly through the whole surface of a perforated blackened plate (the absorber plate) exposed to the sun. An important parameter fixing the collector’s efficiency is the heat exchange effectiveness, e. Once e is known, finding the collector efficiency is straight-forward. The effectiveness depends on the wind speed, the suction velocity and the plate geometry. This paper is about determining this effectiveness by computational fluid mechanics (CFD), for conditions of no wind. Because of symmetry, the computational domain needed only to extend over a representative element, which included one hole and the region immediately adjacent to it extending to half the distance between holes. Simulations were carried out over a wide range of conditions, and the results are incorporated into a correlation model. Because of the no-wind assumptions, the model is of limited direct use, but when combined with experimental data, the model can permit a wider-ranging correlation equation to be obtained. 00100373
A multistage solar receiver: the route to high
temperature Kribus, A. er al. Solar Energy, 1999, 67, (l-3). 3-11. A high-temperature solar thermal recetver is subject to temperaturedependent emission and convection losses. Minimizing these losses is essential to realization of high temperature, high efficiency systems. Dividing the aperture into separate stages according to the irradiance distribution has been shown theoretically to significantly reduce these losses. In such a partitioned system, the working fluid is gradually heated as it passes through a sequence of receiver elements with increasing irradiance levels. An experiment to demonstrate this principle using two heating stages has been constructed at the Weizmann Institute’s Solar Tower. The high-temperature receiver stage is the Directly Irradiated Annular Pressurized Receiver (DIAPR). The low-temperature stage is implemented as a partial ring of intermediate-temperature cavity tubular receivers (Preheaters) surrounding the central high-temperature stage. Following initial concentration by a part of the Weizmann Institute heliostat field, the light enters the receivers via secondary concentrators constructed as approximate CPCs. We present recent test results with the two-stage system. Air exit temperatures of up to 1000°C were obtained, with the low-temperature stage supplying up to 750°C. The power output was up to 55 kW,t,. Heat transfer in the high-temperature receiver, losses due to the partitioning and future plans for partitioned receivers are discussed.
Accelerated life testing of solar absorber coatings: testing procedure and results
00100374
Brunold, S. et al. Solar Energy, 2000, 68, (4), 313-323. A procedure for accelerated life testing of solar absorber surfaces was developed within the framework of the working group MSTC (materials in solar thermal collecrors) of the IEA-SHCP (International Energy Agency-solar heating and cooling programme). The intensive