EBOOK - Solar Thermal and Biomass Energy (G. Lorenzini)

'EBOOK - Năng lượng sinh học và nhiệt mặt trời - Tác giả: G. Lorenzini

Conventional energy sources based on oil, coal and natural gas are damaging economic and social progress, the environment and human life. Many people are concerned about these problems and wish to address the symptoms as a matter of urgency, but not all understand the basic causes and consequently do not realize that not only technological, but also social changes are required.
It is now widely acknowledged that renewable energy capacity has to be increased by exploiting its enormous potential. During the last few years the ‘energy issue’ has been assuming a more and more important role among any other choice, strategy and policy concerning human survival and development.
Nowadays the energy model is almost totally centred (for the 80%) on the exploitation of fossil fuels such as petrol, natural gas and coal. To the industrial–economic costs connected with these fuels, social and environment costs, which cannot be overlooked, have to be added.
First of all, fossil fuels are exhaustible energy sources; their formation time is infinitely lower than the one which refers to their exploitation and for this reason are also defined as ‘non-renewable resources’. Although the level of the world’s fossil fuel supply cannot be considered as worrying in the short term, the increased difficulties in reaching the fields have made the cost–benefit ratio of the extraction processes less and less favourable.
Secondly, the political, social and economic instability, deriving from the world consumption distribution (only 20% of world population consumes the 80% of available resources) and the increasing number of wars connected with the geopolitics of fossil resources and with the control of international supplies, represents a risk for the security and the possible normal development of nations.

Eventually it is necessary to consider the environmental impact caused by the exploitation of fossil energy sources; actually their combustion process brings on the emission of noxious substances such as sulphurous anhydride, nitrogen monoxide and carbon anhydride (15 billion tons of CO2 are poured out into the atmosphere every year). Sulphurous anhydride and nitrogen monoxide contribute to the formation of acid rains while carbon anhydride is the main greenhouse gas which causes global warming (greenhouse effect).
So behind fossil fuel exploitation is hidden the risk of worrying consequences regarding both the Earth (desertification, arctic ice melt, sea level rise...) and indirectly human health (rise in respiratory diseases, decrease of drinkable water...) .
The analyzed context brought us to review in a critical way the concepts and models of development which have been taken into consideration to date and which have centred on the massive exploitation of fossil sources.
During the last few years this review has led to elaborate the concept of sustainable development, which is based on energy consumption reduction and optimization, and also on the use of renewable energy sources (the Sun, the Wind, hydraulic energy, geothermic resources, tides and wave motion; this definition is completed by the biomasses, although these resources can only be considered as renewable if run with the purpose to make their exploitation time consistent with their renewal time).
In comparison to fossil fuels, renewable sources could contribute to the development of a sustainable energy system and to environment and territorial protection; they could also provide new economic growth opportunities.
Recently, the European Union passed new legislative measures to delineate in a binding manner the plan, from now to 2020, to decrease the climate effects caused by present energy consumption levels; that is to say that at least 20% of primary energy will have to be produced by renewable sources, greenhouse gas emission will have to be reduced of 20% and another 20% will have to be an energy saving which the EU means to reach by a wide energy efficiency recovery.
The importance placed upon renewable energy sources now and in the future inside the world energy panorama led us to focus this study on what can be defined as the most relevant renewable source: the Sun. A policy of energy sustainability can’t leave solar energy exploitation out of consideration. Actually its incident quota on the terrestrial surface is 10,000 times greater than the yearly energy requirement of the world’s population. Besides being the origin of almost all the other energy sources, renewable and conventional, excluding geothermic, nuclear and gravitational (tides) ones, the energy provided by the Sun is free, endless and clean (the devices used to exploit solar energy are characterized by very low emissions while running). Moreover solar energy is easy to harness and distribute (it is particularly abundant in many world areas with depressed and difficult economic situation).
The first chapter of this study is dedicated to the analysis and calculation of solar radiation incident on an inclined surface at an instantaneous, hourlyand daily level.
The second chapter offers a summary and an analysis of all technologies available today to use solar energy: the solar thermal (technologies which exploit solar radiation in order to produce thermal energy that can be used in domestic, civil and productive fields; the differences between low, medium and high temperature solar thermal energy will be identified).
In the last part of the book we judge through a deeper investigation the opportunities offered by the exploitation of biomass energy. Renewable energy education is a relatively new field and previously it formed a minor part of traditional university courses. However, over the past decade, several new approaches have emerged: we see these in the new literature and, even more clearly, in new books. The present treatise, in the authors’ auspices, represents a contribution to this new ‘incoming science’. The book is highly recommended to professors, students and professionals in mechanical, civil, environmental, chemical and agricultural engineering. It is also recommended to all the readers interested in the aims, philosophy, structure, design, strategies and overcomes in the use of energy from ‘solar thermal and biomasses’.

Chapter 1
The solar radiation ........................................................................................  3
1  The solar physics...................................................................................... 3
2  The solar constant ....................................................................................  5
3  The extraterrestrial radiation.................................................................... 6
4  The position of the Sun in the celestial vault ...........................................  6
5  The solar radiation on the Earth’s soil during clear sky days...................  9
6  Instantaneous direct radiation received ona surface................................  12
7  Instantaneous global radiation received on a surface...............................  15
8  Calculation of direct energy received ona surface ..................................  15
9  The true solar time ...................................................................................  16
10  The diagram of solar trajectories..............................................................  18
11  The monthly average solar radiation on inclined surfaces .......................  19
12  Daily radiation on aninclined surface .....................................................  20
13  Hourly solar radiation on inclined surfaces..............................................  20
14  The local radiation data retrieval..............................................................  21
15  Variation in the energy which can be intercepted by the
position of the surfaces ............................................................................ 22
Chapter 2
Solar energy utilization ................................................................................. 25
1  Introduction..............................................................................................  25
2  Low-temperature solar thermal technology .............................................  26
2.1 The advantages................................................................................. 26
2.2 Low-temperature solar thermal system ............................................  27
2.2.1 The collector ..........................................................................  28
2.2.2  Typologies of solar systems...................................................  54
2.2.3  The solar circuit .....................................................................  69
2.2.4  The storage tank.....................................................................  75
2.3  Passive solar heating systems...........................................................  80
2.3.1 Direct gain systems ................................................................  81
2.3.2 Indirect gain systems..............................................................  82
2.3.3 Solar greenhouse.................................................................... 85
2.3.4  Isolated gain systems .............................................................  86
3  Medium-temperature solar thermal technology .......................................  87
4  High-temperature solar thermal technology.............................................  90
4.1  Concentrating solar power technology: clean energy for
power tenability................................................................................  90
4.2  Prospects of CSP technologies ......................................................... 93
4.3  The Italian position and interest in CSP technologies ......................  93
4.4 CSP technology................................................................................ 94
4.4.1 Linear parabolic collector systems.........................................  95
4.4.2 Tower system with a central receiver..................................... 99
4.4.3  Parabolic dish collector systems ............................................ 104
4.4.4  The use of CSP technology for electricity production ........... 105
4.4.5  The future: the direct production of solar hydrogen............... 106
4.5  The ENEA technological proposal for solar electricity:
the use of molten salts in parabolic collector systems...................... 106
4.5.1 The advantages of molten salts .............................................. 108
4.5.2  The solar collectorused by ENEA......................................... 110
4.5.3 The Archimedes Project......................................................... 115
4.6 Conclusions ...................................................................................... 118
4.7  Solar technologies for electricity generation without
light concentration............................................................................ 119
4.7.1 Solar chimneys/towers ........................................................... 119
4.7.2 Solar ponds ............................................................................ 123
General bibliography and consulted websites – Part I............................... 127
PARTII: BIOMASSES ENERGY
Chapter 3
Biomasses identities ....................................................................................... 133
1  Introduction.............................................................................................. 133
2  Definition and classification .................................................................... 134
3  Origin and nature ..................................................................................... 135
3.1  The forest and agro-forest behaviour ............................................... 135
3.2  The agricultural compartment .......................................................... 137
3.2.1 Agricultural residuals............................................................. 138
3.2.2 Dedicated cultures.................................................................. 139
3.3  The zoo technique compartment ...................................................... 143
3.4 Industrial activities........................................................................... 145
3.4.1 The wood industry ................................................................. 145
3.4.2  The cellulose and paper industry............................................ 145
3.4.3 The agro-alimentary industry................................................. 146
3.5 Urban residuals................................................................................. 146
4  Commercial forms ................................................................................... 147
4.1  Liquid state combustible biomasses ................................................. 147
4.1.1 Firewood ................................................................................ 147
4.1.2 Chips ...................................................................................... 147
4.1.3 Densified forms: pellets ......................................................... 150
4.1.4  Densified forms: the briquette................................................ 153
4.1.5  Lignocellulose biomass fitness for the transformation
into commercial forms ........................................................... 155
4.2  Fuel biomass in the liquid state ........................................................ 156
4.2.1 Vegetable oils ........................................................................ 156
4.2.2 Bio-diesel............................................................................... 156
4.2.3 Bio-ethanol............................................................................. 159
4.3  Combustible biomasses in the gaseous state .................................... 162
4.3.1 Bio-gas ................................................................................... 162
Chapter 4
Energy from biomasses ................................................................................. 167
1  Biomass energy conversion ..................................................................... 167
2  Biochemical conversion........................................................................... 168
2.1 Anaerobic digestion.......................................................................... 169
2.1.1  Plant typologies applicable to liquid or
effluent manures..................................................................... 170
2.1.2 Co-digestion........................................................................... 173
2.1.3  Bio-gas in solid rejections dumps .......................................... 174
2.2 Aerobic digestion ............................................................................. 175
2.3 Alcohol fermentation........................................................................ 176
2.3.1  The sacchariferous section of the bio-ethanol
production spinneret............................................................... 176
2.3.2  The starchy section of the bio-ethanol
production spinneret............................................................... 177
2.3.3  The cellulosic section of the bio-ethanol
production spinneret............................................................... 178
2.4  Oil extraction and bio-diesel production .......................................... 179
2.4.1 Vegetable oil extraction ......................................................... 179
2.4.2 Vegetable oil regeneration ..................................................... 180
2.4.3 Transesterification.................................................................. 181
3  Thermochemicalconversion .................................................................... 182
3.1 Direct combustion ............................................................................ 181
3.2 Gasification ...................................................................................... 190
3.2.1 Fixed-bed gasificators............................................................ 191
3.2.2 Fluid-bed gasificators............................................................. 194
3.2.3  Producer gas applications....................................................... 197
3.3 Pyrolysis........................................................................................... 198
Chapter 5
Environmental aspects .................................................................................. 203
1  Reduction of emissions into the atmosphere............................................ 203
1.1  The carbon dioxide emissions balance............................................. 203
1.2  Comparison between the polluting emissions of
the main vegetable and fossil origin fuels ........................................ 204
1.2.1 Bio-ethanol............................................................................. 204
1.2.2 Bio-diesel............................................................................... 205
1.2.3 Bio-gas ................................................................................... 206

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'EBOOK - Năng lượng sinh học và nhiệt mặt trời - Tác giả: G. Lorenzini

Conventional energy sources based on oil, coal and natural gas are damaging economic and social progress, the environment and human life. Many people are concerned about these problems and wish to address the symptoms as a matter of urgency, but not all understand the basic causes and consequently do not realize that not only technological, but also social changes are required.
It is now widely acknowledged that renewable energy capacity has to be increased by exploiting its enormous potential. During the last few years the ‘energy issue’ has been assuming a more and more important role among any other choice, strategy and policy concerning human survival and development.
Nowadays the energy model is almost totally centred (for the 80%) on the exploitation of fossil fuels such as petrol, natural gas and coal. To the industrial–economic costs connected with these fuels, social and environment costs, which cannot be overlooked, have to be added.
First of all, fossil fuels are exhaustible energy sources; their formation time is infinitely lower than the one which refers to their exploitation and for this reason are also defined as ‘non-renewable resources’. Although the level of the world’s fossil fuel supply cannot be considered as worrying in the short term, the increased difficulties in reaching the fields have made the cost–benefit ratio of the extraction processes less and less favourable.
Secondly, the political, social and economic instability, deriving from the world consumption distribution (only 20% of world population consumes the 80% of available resources) and the increasing number of wars connected with the geopolitics of fossil resources and with the control of international supplies, represents a risk for the security and the possible normal development of nations.

Eventually it is necessary to consider the environmental impact caused by the exploitation of fossil energy sources; actually their combustion process brings on the emission of noxious substances such as sulphurous anhydride, nitrogen monoxide and carbon anhydride (15 billion tons of CO2 are poured out into the atmosphere every year). Sulphurous anhydride and nitrogen monoxide contribute to the formation of acid rains while carbon anhydride is the main greenhouse gas which causes global warming (greenhouse effect).
So behind fossil fuel exploitation is hidden the risk of worrying consequences regarding both the Earth (desertification, arctic ice melt, sea level rise...) and indirectly human health (rise in respiratory diseases, decrease of drinkable water...) .
The analyzed context brought us to review in a critical way the concepts and models of development which have been taken into consideration to date and which have centred on the massive exploitation of fossil sources.
During the last few years this review has led to elaborate the concept of sustainable development, which is based on energy consumption reduction and optimization, and also on the use of renewable energy sources (the Sun, the Wind, hydraulic energy, geothermic resources, tides and wave motion; this definition is completed by the biomasses, although these resources can only be considered as renewable if run with the purpose to make their exploitation time consistent with their renewal time).
In comparison to fossil fuels, renewable sources could contribute to the development of a sustainable energy system and to environment and territorial protection; they could also provide new economic growth opportunities.
Recently, the European Union passed new legislative measures to delineate in a binding manner the plan, from now to 2020, to decrease the climate effects caused by present energy consumption levels; that is to say that at least 20% of primary energy will have to be produced by renewable sources, greenhouse gas emission will have to be reduced of 20% and another 20% will have to be an energy saving which the EU means to reach by a wide energy efficiency recovery.
The importance placed upon renewable energy sources now and in the future inside the world energy panorama led us to focus this study on what can be defined as the most relevant renewable source: the Sun. A policy of energy sustainability can’t leave solar energy exploitation out of consideration. Actually its incident quota on the terrestrial surface is 10,000 times greater than the yearly energy requirement of the world’s population. Besides being the origin of almost all the other energy sources, renewable and conventional, excluding geothermic, nuclear and gravitational (tides) ones, the energy provided by the Sun is free, endless and clean (the devices used to exploit solar energy are characterized by very low emissions while running). Moreover solar energy is easy to harness and distribute (it is particularly abundant in many world areas with depressed and difficult economic situation).
The first chapter of this study is dedicated to the analysis and calculation of solar radiation incident on an inclined surface at an instantaneous, hourlyand daily level.
The second chapter offers a summary and an analysis of all technologies available today to use solar energy: the solar thermal (technologies which exploit solar radiation in order to produce thermal energy that can be used in domestic, civil and productive fields; the differences between low, medium and high temperature solar thermal energy will be identified).
In the last part of the book we judge through a deeper investigation the opportunities offered by the exploitation of biomass energy. Renewable energy education is a relatively new field and previously it formed a minor part of traditional university courses. However, over the past decade, several new approaches have emerged: we see these in the new literature and, even more clearly, in new books. The present treatise, in the authors’ auspices, represents a contribution to this new ‘incoming science’. The book is highly recommended to professors, students and professionals in mechanical, civil, environmental, chemical and agricultural engineering. It is also recommended to all the readers interested in the aims, philosophy, structure, design, strategies and overcomes in the use of energy from ‘solar thermal and biomasses’.

Chapter 1
The solar radiation ........................................................................................  3
1  The solar physics...................................................................................... 3
2  The solar constant ....................................................................................  5
3  The extraterrestrial radiation.................................................................... 6
4  The position of the Sun in the celestial vault ...........................................  6
5  The solar radiation on the Earth’s soil during clear sky days...................  9
6  Instantaneous direct radiation received ona surface................................  12
7  Instantaneous global radiation received on a surface...............................  15
8  Calculation of direct energy received ona surface ..................................  15
9  The true solar time ...................................................................................  16
10  The diagram of solar trajectories..............................................................  18
11  The monthly average solar radiation on inclined surfaces .......................  19
12  Daily radiation on aninclined surface .....................................................  20
13  Hourly solar radiation on inclined surfaces..............................................  20
14  The local radiation data retrieval..............................................................  21
15  Variation in the energy which can be intercepted by the
position of the surfaces ............................................................................ 22
Chapter 2
Solar energy utilization ................................................................................. 25
1  Introduction..............................................................................................  25
2  Low-temperature solar thermal technology .............................................  26
2.1 The advantages................................................................................. 26
2.2 Low-temperature solar thermal system ............................................  27
2.2.1 The collector ..........................................................................  28
2.2.2  Typologies of solar systems...................................................  54
2.2.3  The solar circuit .....................................................................  69
2.2.4  The storage tank.....................................................................  75
2.3  Passive solar heating systems...........................................................  80
2.3.1 Direct gain systems ................................................................  81
2.3.2 Indirect gain systems..............................................................  82
2.3.3 Solar greenhouse.................................................................... 85
2.3.4  Isolated gain systems .............................................................  86
3  Medium-temperature solar thermal technology .......................................  87
4  High-temperature solar thermal technology.............................................  90
4.1  Concentrating solar power technology: clean energy for
power tenability................................................................................  90
4.2  Prospects of CSP technologies ......................................................... 93
4.3  The Italian position and interest in CSP technologies ......................  93
4.4 CSP technology................................................................................ 94
4.4.1 Linear parabolic collector systems.........................................  95
4.4.2 Tower system with a central receiver..................................... 99
4.4.3  Parabolic dish collector systems ............................................ 104
4.4.4  The use of CSP technology for electricity production ........... 105
4.4.5  The future: the direct production of solar hydrogen............... 106
4.5  The ENEA technological proposal for solar electricity:
the use of molten salts in parabolic collector systems...................... 106
4.5.1 The advantages of molten salts .............................................. 108
4.5.2  The solar collectorused by ENEA......................................... 110
4.5.3 The Archimedes Project......................................................... 115
4.6 Conclusions ...................................................................................... 118
4.7  Solar technologies for electricity generation without
light concentration............................................................................ 119
4.7.1 Solar chimneys/towers ........................................................... 119
4.7.2 Solar ponds ............................................................................ 123
General bibliography and consulted websites – Part I............................... 127
PARTII: BIOMASSES ENERGY
Chapter 3
Biomasses identities ....................................................................................... 133
1  Introduction.............................................................................................. 133
2  Definition and classification .................................................................... 134
3  Origin and nature ..................................................................................... 135
3.1  The forest and agro-forest behaviour ............................................... 135
3.2  The agricultural compartment .......................................................... 137
3.2.1 Agricultural residuals............................................................. 138
3.2.2 Dedicated cultures.................................................................. 139
3.3  The zoo technique compartment ...................................................... 143
3.4 Industrial activities........................................................................... 145
3.4.1 The wood industry ................................................................. 145
3.4.2  The cellulose and paper industry............................................ 145
3.4.3 The agro-alimentary industry................................................. 146
3.5 Urban residuals................................................................................. 146
4  Commercial forms ................................................................................... 147
4.1  Liquid state combustible biomasses ................................................. 147
4.1.1 Firewood ................................................................................ 147
4.1.2 Chips ...................................................................................... 147
4.1.3 Densified forms: pellets ......................................................... 150
4.1.4  Densified forms: the briquette................................................ 153
4.1.5  Lignocellulose biomass fitness for the transformation
into commercial forms ........................................................... 155
4.2  Fuel biomass in the liquid state ........................................................ 156
4.2.1 Vegetable oils ........................................................................ 156
4.2.2 Bio-diesel............................................................................... 156
4.2.3 Bio-ethanol............................................................................. 159
4.3  Combustible biomasses in the gaseous state .................................... 162
4.3.1 Bio-gas ................................................................................... 162
Chapter 4
Energy from biomasses ................................................................................. 167
1  Biomass energy conversion ..................................................................... 167
2  Biochemical conversion........................................................................... 168
2.1 Anaerobic digestion.......................................................................... 169
2.1.1  Plant typologies applicable to liquid or
effluent manures..................................................................... 170
2.1.2 Co-digestion........................................................................... 173
2.1.3  Bio-gas in solid rejections dumps .......................................... 174
2.2 Aerobic digestion ............................................................................. 175
2.3 Alcohol fermentation........................................................................ 176
2.3.1  The sacchariferous section of the bio-ethanol
production spinneret............................................................... 176
2.3.2  The starchy section of the bio-ethanol
production spinneret............................................................... 177
2.3.3  The cellulosic section of the bio-ethanol
production spinneret............................................................... 178
2.4  Oil extraction and bio-diesel production .......................................... 179
2.4.1 Vegetable oil extraction ......................................................... 179
2.4.2 Vegetable oil regeneration ..................................................... 180
2.4.3 Transesterification.................................................................. 181
3  Thermochemicalconversion .................................................................... 182
3.1 Direct combustion ............................................................................ 181
3.2 Gasification ...................................................................................... 190
3.2.1 Fixed-bed gasificators............................................................ 191
3.2.2 Fluid-bed gasificators............................................................. 194
3.2.3  Producer gas applications....................................................... 197
3.3 Pyrolysis........................................................................................... 198
Chapter 5
Environmental aspects .................................................................................. 203
1  Reduction of emissions into the atmosphere............................................ 203
1.1  The carbon dioxide emissions balance............................................. 203
1.2  Comparison between the polluting emissions of
the main vegetable and fossil origin fuels ........................................ 204
1.2.1 Bio-ethanol............................................................................. 204
1.2.2 Bio-diesel............................................................................... 205
1.2.3 Bio-gas ................................................................................... 206

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Chuyên mục: C. Bài giảng C. Bài giảng chuyên ngành Nhiệt Lạnh (Heat and Refrigeration) C. Bài giảng kỹ thuật