SIMULINK MODEL OF BIOMASS
Saroj De Sousa
B.E., Goa University, India, 2002
PROJECT
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
ELECTRICAL AND ELECTRONIC ENGINEERING
at
CALIFORNIA STATE UNIVERSITY, SACRAMENTO
SUMMER
2012
SIMULINK MODEL OF BIOMASS
A Project
by
Saroj De Sousa
Approved by:
__________________________________, Committee Chair
Salah Yousif, Ph.D.
__________________________________, Second Reader
Preetham Kumar, Ph.D.
____________________________
Date
ii
Student: Saroj De Sousa
I certify that this student has met the requirements for format contained in the University
format manual, and that this project is suitable for shelving in the Library and credit is to
be awarded for the Project.
__________________________, Graduate Coordinator
Preetham Kumar, Ph.D.
Department of Electrical and Electronic Engineering
iii
___________________
Date
Abstract
of
SIMULINK MODEL FOR BIOMASS
by
Saroj De Sousa
Biomass is a energy from the solar which has a very high potential to replace the fossil
fuel. It is also potential contributor to low greenhouse gas emissions. Since the humans
contribute to one quarter and in fact is left to decay naturally. Biomass energy conversion
uses the raw material from agricultural and forest product residues. The biomass
collected can be combusted, gasified, biologically digested or fermented depending on
the product and the desired carrier product. Research opportunities include improvements
in the photosynthetic efficiency and nutrient requirements of energy crops, biomasstailored thermochemical conversion systems, and genetic engineering of microorganisms
for more efficient biological conversion and the efficient production of hydrogen directly
from sunlight.
, Committee Chair
Salah Yousif, Ph.D.
_______________________
Date
iv
ACKNOWLEDGEMENTS
This space provides me a great honor to thank all the people with whose support this
project and my masters have been a success. I would take this opportunity to convey my
sincere thank you to all.
Firstly, I would like to thank both Dr. Salah Yousif and Dr. Preetham Kumar, for their
help and supportive guide throughout this project in highs and lows has been
commendable. They took extra effort to review the report and kept on giving me pieces
of advice during my course of project completion.
Furthermore, I would like to thank the Department of Electrical and Electronics at
California State University, Sacramento for extending this opportunity for me to pursue
my Masters degree and guiding me all the way to become a successful student.
Last but not the least, I am thankful to my parents for their constant support and belief in
me, their words of wisdom and moral support helped me overcome all the challenges and
through their guidance I was able to successfully complete my project and earn my
Masters Degree.
v
TABLE OF CONTENTS
Page
Acknowledgements ............................................................................................................. v
List of Tables ................................................................................................................... viii
List of Figures .................................................................................................................... ix
Chapter
1. INTRODUCTION……………………………………………………………………...1
1.1 Renewable Energy……………………………...……………………………..1
1.2 Different Forms of Renewable Energy………………….…………...……..…2
1.3 Uses of Renewable Energy……………………………………………………7
1.4 Advantages of Renewable Energy over Nonrenewable Energy…….………...8
1.5 Why Biomass Energy is Important?….………………..………...……………8
2. BIOMASS…………………………………………………………………………..…10
2.1 Definition…………………………………………………………………….10
2.2 Biomass Sources…………………..…..……..……………..……………..…10
2.3 Different Categories of Biomass………………………...……………...……11
2.4 Uses of Biomass…………………………………………………………..….15
2.5 Heating Methods of Biomass………………….……………………………..16
2.6 Biomass Heating Advantages and Disadvantages…………...…………..…..18
3. BIOFUELS…………………..…..……………..…………………………………..…21
3.1 What are Biofuels and Why Use Them?.........….………………………...….21
3.2 First Generation of Biofuels.……………………………………………....…21
4. SOLAR POWER……………………………………………………………………...27
4.1 Why Solar Power?…………...…………..…………………………………..27
4.2 How to Generate Electricity from Solar Energy?..…………..…………..…..29
4.3 Distribution of Solar Power…...……………………………………………..30
5. GENERATION OF ELECTRICITY USING BIOMASS………………………….....32
5.1 Biomass Energy Conversion Overview….…………………………...……...32
vi
5.2 Different Processes Used for Conversion of Biomass into
Electrical Energy…………………………………………………………….34
5.3 Biomass Gasification………...………………………………………………36
5.4 How to Develop Process Control System……………………………………39
6. SIMULINK MODEL WITH BIOMASS………………………………...……………43
6.1 Introduction of Simulink Model………………….………………………….43
6.2 Biochemical Reactor………………………………………………………....43
6.3 Simulink Model Diagram………………………………………..…..............50
7. SIMULINK RESULTS FOR THE BIOMASS MODEL……………………………..52
8. CONCLUSION …………………………………………………………….…………61
9. FUTURE WORK……………………………………………………………………...62
Bibliography……………………………………………………………………………..63
vii
LIST OF TABLES
Page
1. Table 6.1 Steady-State Conditions………………………….……………….………...46
viii
LIST OF FIGURES
Page
1. Figure 1.1 Global Renewable Power Capacity…..………..………...…….…………....1
2. Figure 1.2 A Wind Farm Located in Manji, Iran…..………….……………….……….2
3. Figure 1.3 Grand Coulee Dam on Columbia River…..….…….…………….…………3
4. Figure 1.4 Nellis Solar Power Plant……….………………………………….………...4
5. Figure 1.5 Biomass…………………………………………………………….……….5
6. Figure 1.6 San Paulo Ethanol Pump…....………………………………..…….……….6
7. Figure 1.7 Nesjavellir Geothermal Station in Iceland…….……...……….…….……...7
8. Figure 2.1 An Ocean Food Web Showing a Network of Food Chains…..………...…14
9. Figure 2.2 U.S Energy Consumption for Biomass……………………………….…...16
10.Figure 3.1 U.S Biodiesel Production, Exports and Consumption…………...…….....23
11.Figure 3.2 Schematic of Biodiesel Production Path………………..……...................24
12.Figure 3.3 Average Emissions Impact of Biodiesel for
Heavy-Duty Highway Engines….…………………………………….…..25
13.Figure 4.1 Worldwide Distribution of solar radiation..………………………………31
14.Figure 5.1 Renewable Energy World, 2006……………..……………….…………...33
15.Figure 5.2 Fuelizex Bed Combustion………………….……………………………..36
16.Figure 5.3 Flow Control Diagram for Biomass Gasification…….....………………...38
17.Figure 5.4 Control Representation ……………………….………….………….........42
18. Figure 6.1 Control and Instrumentation Diagram of Biochemical Reactor.…..……..44
19.Figure 6.2 Simulink Model…….…….…………………………………….…...…….50
20.Figure 7.1 Simulink Model with Scope…….…………...…………....…….…….......52
ix
21.Figure 7.2 Small response change at biomass Concentrate x1……………….……....53
22.Figure 7.3 Response change at substrate Concentrate x2…………………….………54
23.Figure 7.4 Response change at x1 with lambda 30 at x1…………………….……….55
24.Figure 7.5 Response change at x2 with lambda 30 at x2…………………….……….56
25.Figure 7.6 Response due to change in setpoint at x1………………………….……...57
26.Figure 7.7 Response due to change in setpoint at x2………………………….……...58
27.Figure 7.8 Response due to change in setpoint at x1………………………….……...59
28.Figure 7.8 Response due to change in setpoint at x2………………………….……...60
x
1
Chapter 1
INTRODUCTION
1.1 Renewable Energy
Energy which is found naturally on Earth is termed as renewable Energy. Renewable
energy is also produced from the processes which are natural and constantly replenished.
There are different forms of renewable energy such as sunlight, wind, rain, Tides and
geothermal heat. Renewable energy support in the consumption 16% globally [1]. Out of
16%, biomass is used 10%, hydroelectricity is used 3.4% and another 3% from newer
forms of renewable energy like modern biomass, solar, wind, biofuels and geothermal
[1]. Now a day’s research is being done on renewable energy.
Figure 1.1: Global renewable power capacity
2
Renewable sources used for electricity generation accounts for 19% globally. Out of this
global electricity 19% is from hydroelectricity and 3% from new renewable energy
sources. The share of wind power is increasing rapidly.
1.2 Different Forms of Renewable Energy
Renewable energy replaces conventional fuels in four distinct areas: electricity
generation, hot water/space heating, motor fuels and rural (off- grid) energy services [1].
The different forms of renewable energy sources are discussed as follows.
i. Wind Power
Figure 1.2: A wind farm located in Manji, Iran
Converting wind energy to a form of energy which we can use is known as wind power.
Wind Turbines convert wind to electricity, windmills for mechanical power, wind pump
for pumping water, sails to propel the ships.
3
In the figure 1.2 you can see that the farm has several hundred of wind turbines. These
turbines are attached to an electric power system to transmit electricity produced. The
wind farms closer to the shore have the advantage of frequent and powerful winds. The
maintenance cost is considerably low however the installation cost is high. Considering
wind power as one of the best alternative to fossil fuel since it is found abundantly,
renewable, clean, distributed throughout the earth, it does not increase the greenhouse
effect. No gases emitted during production and land space need for installation is less. It
has less effect on the atmosphere as compared to the other power sources. In the year
2011, 83 countries have been using and many countries are showing interest [2]. The cost
per unit is similar to cost per unit of electricity from coal and gas. A disadvantage is that
it is not aesthetically approved.
ii. Hydropower
Figure 1.3: Grand Coulee Dam on Columbia River
4
Power which is obtained from the water falling from a height and harnessed so that it can
be used is called hydropower. This is very ancient process to generate power. It has been
used for irrigation, as well mechanical operations. Trompe is another method in which air
gets compressed due to water falling from a height. This compressed air is then used to
pipe power to distant machines from the waterfalls.
When there is a flood the energy is at the maximum and but this can cause erosion,
transport sediments to the rivers at the base.
iii. Solar Energy
Figure 1.4: Nellis Solar Power Plant
Another type of energy captured form the solar is the solar energy. Solar heating, solar
photovoltaic, solar thermal electricity and solar architecture, contribute considerably for
5
the generation of electricity from solar. They are broadly characterized as passive solar or
active solar. It depends on the way it is collected, converted and distributed. In 2011, the
International Energy Agency said that “the development of affordable, inexhaustible and
clean solar energy technologies will have huge longer-term benefits [4]”. This will
increase countries energy security through reliance on as indigenous, inexhaustible and
mostly import-independent resource, enhance sustainability, reduce pollution, lower the
cost of mitigating climate changes, and keep fossil fuel prices lower than otherwise [4].
iv. Biomass
Figure 1.5: Biomass
Any biological material can be used as fuel is called biomass. Mostly biomass fuel is
burned and also can be changed in systems which generated heat, electricity or both heat
or power. Biomass like woodchips, wood pellets and other low graded wood wastes are
6
the major content of biomass fuel. Even farm residue and farm animal wastes are good
source for biomass.
v. Biofuel
Figure 1.6: San Paulo ethanol pump
Fuels derived from biomass which is solid, liquid and other biogases. Biofuels have
gaining their importance due to the hike in oil prices as well as exhaustive nature of the
fossil fuel. Biodiesel are made up of vegetable oil and animal fats. It can be used as a fuel
for vehicles but it is mostly used as an addition to the fuel to reduce the toxic gases like
carbon monoxide and hydrocarbons. Brazil and United States are the top producers for
biofuel.
7
vi. Geothermal energy
Electricity is obtained from geothermal energy. 24 countries generate electricity from
geothermal energy [6]. Geothermal power is considered to be sustainable because the
heat extraction is small compared with the earth’s heat content. The emission intensity of
existence geothermal electric plant is on average 122kg of carbon dioxide per megawatthour (MW-h) of electricity, about one-eighth of a conventional coal-fired plant [6].
Figure 1.7: Nesjavellir Geothermal station in Iceland
1.3 Uses of Renewable Energy
Mostly rural areas take advantage of renewable energy. Energy is used for household
lighting, entertainment, heating, cooking. It increases income as the electricity is in
productive uses of electricity and also developments benefits. Renewable energy have
been growing in productive uses in the areas of agriculture, small scale industries,
services used for commercial and services like drinking water, education and health care.
8
Nonrenewable energy produces air pollution which can aggravate asthama to patients.
Burning coal produces sulfur oxides during burning for the production of electricity.
These cause acid rain which in tern damages land.
1.4 Advantages of Renewable Energy over Nonrenewable Energy
The projects which are built to produce renewable energy are huge and costly. Mostly
people in the rural and remote regions make use of the renewable energy on huge basis.
Due to different climatic changes in various regions there are a huge concern for energy.
Along with huge hike in oil prices, peak oil as well as government supporting the
research in renewable energy, there is huge research and development going on.
According to a 2011 projection by the International Energy Agency, solar power
generators may produce most of the world’s electricity within 50 years [1].
Main advantage of renewable energy is that as it is renewed means it is sustainable and so
will never run out. Since there is less bi-product from renewable energy, the cost of
maintenance and overhead cost reduces. But the nonrenewable means have bi-products as
well as cost increases for the maintenance of the plants. Waste products from renewable
energy plants are carbon dioxide and chemical which have least harm hazard to the
environment. Due to this economic benefits increases.
1.5 Why Biomass Energy is Important?
As any renewable energy biomass is sustainable and benign source of energy. Biomass is
grown for fuel and they can substitute for fossil fuel. Utilization of biomass results in
9
reduction in one of the important factors known as the greenhouse effect. This effect
results in increasing the earth’s temperature. So this effect can be reduced by using the
biomass. The biomass decomposes and produces methane which is twenty times more
active as a greenhouse gas than carbon dioxide.
When this biomass is burned, this results in emission of another greenhouse gas known as
the carbon dioxide. Even the biomass fuels have few content of sulfur which adds to
sulfur dioxide emissions, which in turn causes acid rain. Ash content while burning
biomass is less compared to ash formed by coal burning. The ash obtained from biomass
burning can be used in farm field which is an additive to the soil.
Since it is local to all the regions in all part of the world, the prices do not take part in
fluctuations like the coal or fossil fuel prices. Thus liquid biofuels adds to the economy
and reduces the cost of importing fossil fuel which in turn reduces house hold
expenditures.
Perennial energy crops have lesser earth effects than that agricultural crops.
10
Chapter 2
BIOMASS
2.1 Definition
Biomass, as a renewable energy source, is biological material from living, or recently
living organism [8]. It is used to generate renewable source of energy which can be used
directly or indirectly converting them into biofuels. The energy generated is used for
different purposes. Steam turbines, gasifiers or heat producing machines are used to
obtain electricity. Now a days industry grow biomass like switch grass, hemp, corn,
poplar, willow, sorghum, sugarcane and even eucalyptus to oil palm.
2.2 Biomass Sources
Garbage, landfill gases, wood, waste and alcohol fuels are the commonly found Biomass
sources. Technically, Biomass is contains the commonly found elements. The 3 major
elements are carbon, hydrogen and oxygen based. One of the main sources of Biomass is
the energy from wood and this wood is obtained by pulping liquor or “black liquor,” a
waste product from processes of the pulp, paper and paperboard industry.
Second most commonly Biomass is from waste energy. Waster energy is found from
different waste sites such as municipal solid waste, manufacturing waste and landfill gas.
Biofuels from sugar and oils are the first generation biofuels obtained from sugarcane and
corn, in turn produce bioethanol. These fuels are used as gasoline. Garbage waste releases
11
methane gas which is a type of biogas. Agricultural plants like corn and sugarcane are
used to make engine fuel, ethanol using the process of fermentation.
Such type of waste is mostly found in Mauritius and Southeast Asia (rice husks). United
States have the highest amount of forest waste in the world [8]. UK is one of the leading
countries in poultry farms and these farms give out animal waste which is a good source
of Biomass.
2.3 Different Categories of Biomass
Below are the different categories of Biomasses given.
i.
Terrestrial Biomass [9]
Terrestrial biomass specially found in the forest areas. They contain trees, grasses and
shrubs. As we go higher in the tropical biomass generally decreases in amount. Due to
the carnivorous animals like foxes and eagles the biomass in the area decreases. Biomass
is highly present in the areas where the animals are present that consume the herbivorous
animals such as deer, zebras etc.
Biomass content decreases as with go higher in the inverted pyramid. Grassland falls in
the lower most level of the pyramid. Then the primary consumers fall. The secondary
consumers take the 3rd level above which are the tertiary consumers. The biomass
concentrate at each level decreases as we go higher in the pyramid.
12
Wood waste is used by many industries to generate electricity. Even though electricity is
consumed on a fairly large amount, they need to purchase external electricity too. 49
percent of biomass comes from wood waste such as log, chips, bark and sawdust [10].
Biomass in industries like saw mill and paper mills use much of their waste products to
generate electricity and steam for their own use. This saves the overhead costs like
disposing and buying electricity externally.
Power is generated in wooden companies from wood scrap and sawdust. Such industries
have huge benefits. It not only saves disposal cost and hereby also reduces electricity
bills in the industry. In fact, the pulp and paper industries rely on biomass to meet half of
their energy needs [10]. Other industries that use biomass include lumber producers,
furniture manufacturers, agricultural businesses like nut and rice growers and liquor
producers [10].
i. Ocean Biomass [9]
Ocean also contain food chains and it is as follows
[9] Phytoplankton -> zooplankton -> predatory zooplankton ->filter feeders ->
predatory fish
As Above food chain begins from Phytoplankton. Ocean biomass, in a reversal of
terrestrial biomass, can increase at higher trophic levels [9]. Phytoplankton use
photosynthesis process to change the carbon which is inorganic in nature into protoplasm.
And these are eaten by microscopic animals which are called zooplankton. Zooplankton
13
comprise the second level in the food chain, and include the larva of fish, squid, lobsters
and crabs, small crustaceans such as copepods and krill and many more types [9].
Zooplankton are feed to large carnivorous zooplankters such as krill and by forage fish,
which are small schooling filter feeding fish [9]. This makes up the third level in the food
chain.
The fourth trophic level consists of predatory fish, marine mammals, and seabirds which
consume forage fish. Examples are swordfish, seals and gannets [9]. Apex predators are
on the fifth level of the pyramid and mammals like seals and shortfin live on swordfish.
Biomass in this food chain of the predators is greater than of the producers. This happens
because the ocean primary producers are tiny phytoplankton which grow and reproduce
rapidly on a fast rate [9]. In contrast, terrestrial primary producers grow and reproduce
slowly [9].
Marine cyanobacteria are the smallest known photosynthetic organisms; the smallest of
all, Prochlorococcus, is just 0.5 to 0.8 micrometers across [9]. Prochlorococcus is
possibly the most plentiful species on Earth: a single milliliter of surface seawater may
contain 100,000 cells or more [9]. Worldwide, there are estimated to be several octillion
(~1027) individuals [9]. Prochorococcus is ubiquitous between 40oN and 40oS and
dominates in the ligotrophic (nutrient poor) regions of the oceans [9]. The bacterium
accounts for an estimated 20% of the oxygen in the Earth’s atmosphere and forms part of
the base of the ocean food chain [9].
14
Figure 2.1: An ocean food web showing a network of food chains
ii. Bacterial Biomass [9]
There are typically 40 million bacterial cells in a gram of soil and a million bacteria cells
in a milliliter of fresh water [9]. In all, it has been estimated that there are about five
million trillion trillion bacteria on Earth with a total biomass equaling that of plants.
Some researchers believe the total biomass of bacteria exceeds that of all plants and
animals [9].
iii. Global Biomass [9]
The global biomass has been estimated at about 560 billion tonnes C [9]. Most of this
biomass is found on land, with only 5 to 10 billion tonnes C found in the oceans [9]. On
land there is about 1,000 times more plant biomass (phytomass) than animal biomass
(zoomass) [9]. About 18% of this plant biomass is eaten by the land animals [9].
However in the ocean the animal is nearly 30 times larger than the plant biomass [9].
15
Most ocean plant biomass is eaten by the ocean [9]. Human comprise about 100 million
tonnes of the Earth’s dry biomass, domesticated animals about 700 million tonnes and
crops about 2 billion tonnes [9]. The most successful animal species, in terms of biomass,
may well be Antarctic krill, Euphausia superba, with a fresh biomass approaching 500
million tonnes, although domestic cattle may also reach these immense figures [9].
However as a group, the small aquatic crustaceans called copepods may form the largest
animal biomass on earth [9]. A 2009 paper in Science estimated, for the first time, the
total fish biomass as somewhere between 0.8 and 2.0 billion tonnes [9]. It has been
estimated that about 1% of the global biomass is due to phytoplankton and a staggering
25 % is due to fungi [9].
2.4 Uses of Biomass
Wood gave Americans 90 percent of the energy used in the country [10]. Today, biomass
provides about 4.1 percent of the total energy we consume [10]. Coal, natural gas and
petroleum are used in place of biomass. Biomass is used mainly from burning wood and
wood scraps.
Biomass is used extensively by industries. 51% is consumed in industries. Around 11
percent of biomass is used for power generation [10]. Biomass uses 0.7 percent of the
total electricity. Biggest usage of biomass is in the field of transport; almost 24 percent of
biomass is used for the purpose of transport and produces ethanol and biodiesel [10]. 11
percent is used by homes as electricity. Residential areas use biomass to keep them from
the cold. This is done by burning biomass.
16
Figure 2.2: U.S Energy Consumption for Biomass
2.5 Heating Methods of Biomass
Heat generation is mainly done by the principle of combustion. Biomass heating has been
done for hundreds of years. Due to increase in the value of natural gas, coal and oil,
biomass has been becoming popular among people. Biomass has become competitive
with respect to the prices of energy fossil fuels. A lot of efforts is done to regrow the
farms that are not managed and be a cog in the wheel of a decentralized, multidimensional renewable energy industry [11]. Since 2000 growing such farmland
throughout European countries has been promoted [11]. In different parts of the world,
maintaining forest for biomass has not been very productive and thereby creating
pollution and inefficient means to get heat from biomass.
17
Types of biomass heating systems are
i. Fully automated [11]
These systems use the waste from the forest and farms or anywhere found. As being
transported to the industrial sites, they are put on the conveyor belts from the trucks that
deliver them to the heating boilers. This process is maintained by computer and a beam
which uses the concept of laser keep the track of the waste that the conveyor belt is
bringing in. The boiler temperature and pressure is maintained and also different
temperature and pressure is changed with the help of the software in the computer. This
reduces human error, is more prompt and reduces overhead cost considerably. Operators
are required for the controls only.
ii. Semi-automated or “surge bin” [11]
From the name we come to know that such systems are semi-automated or rather manual
labor is needed to carry out operations. Sometimes more of labor is needed. The systems
consist of small tanks that hold and conveyor system. This is controlled by a controller
which requires personnel to maintain the operations of the system. Efficient boilers are
mostly the wood fire fueled type. They run at the highest capacity. The heat needed
throughout the year is not the maximum heat requirement. The system only work at
highest point few times in the year.
iii. Pellet-fired [11]
Along this other biomass heating system pellet-fired systems is also one of the main
heating systems. The meaning of pellets is that they are processed form of wood, which
18
are consider to be expensive. Even thought they are expensive they are much more
condensed and uniform in nature, and hence much efficient to use. Silo is used to store
the pellets. Due to their condensed nature the cost and area for pellets are much lesser. In
places where area is a factor pellets are used. Even the conveyor systems can be limited
since the conveyor is close to the facility. So due to this even transportation cost reduces.
iv. Combined heat and power [11]
The system combines heat and power is very useful in wood waste. Wood clips are
mostly used in such systems. Heat is the byproduct for the generation of power in the
combined systems. The systems use high pressure for the operations so the cost to
maintain the system also with the installation cost increases. Even manual labor is
needed. To make sure the system operates fine, the manual labor has to be a highly
trained labor. So due to this the cost factor increases along with the operation. Cooling
systems is needed since the output to the systems is heat, if heat is not needed during that
season. All the factor taken into account increase the plant installation, maintaining and
labor cost.
But few places where the CHP is a every good use is in wood manufacturing industry,
hospitals, prisons etc. Heat is used to heat up the water so no addition cooling systems are
needed.
2.6 Biomass Heating Advantageous and Disadvantageous
The major advantages are given below:-
19
a) Noticeable savings over oil or LPG is seen. Also the heating costs. Heat can be
obtained from wood chips by heating to around 2.5 kwh or LPG 6-7p KWH and
electricity at 10p+ kwh.
b) Renewable Incentive Schemes are available. Cash around 7.9 per kwh is paid for
sure for 20 years.
c) Guaranteed payback and return on investment is a major advantage. Return is
around 15% or much better capital is a sure.
d) Carbon dioxide emissions and carbon reduction targets are meet even in the
lowest cost. That is really credible.
e) It proves for going green and helps for a better environment to the local
community and authorities.
f) Local woodlands have been improving and also providing long lasting
environmental benefits. This promotion and facilitates such features.
g) Employment, social and economic benefits are provided in the local rural areas.
This happens due to the development of the wood fuel supply.
h) Assistance is meeting for the building regulation codes during the construction of
structures or refurbishment projects.
Disadvantages are given below:
a) Greenhouse Emissions
Carbon dioxide and other greenhouse gases are produced in case of storage of biomass.
Still research is being done to get solutions to this problem to add it to the use green.
20
b) More Energy
Plantation, cultivation and harvest processes consume more energy then to gain energy
from the biomass. More water content is also needed for farming processes in terms of
growing the crops. Even fertilizers and heavy equipment are needed for farming. It’s a
process which any other crop farming takes. The larger the land more biomass can be
obtained. So area plays a major factor too.
c) Complexity of biomass collection
In search of biomass is needed. So transportation is needed as well as travel is a major
factor.
d) Unstable availability of biomass
Biomasses like corn, wheat, barley are seasonal. There is limited availability all around
the year. This is for other types of crops too. Trees growing are also a slow process even
though they are renewable. Time and season factor plays a major role.
21
Chapter 3
BIOFUELS
3.1 What are Biofuels and Why Use Them?
An increase in demand and prices for different forms of fossil fuels has led into research
for alternative forms of fuels like Biofuels. Biofuels have found place in the momentum
for search of alternative forms of fuels. Biomass, a renewable source of energy, is used to
produce liquid or gaseous fuel called Biofuels. Biofuels are useful as transportation fuel,
an alternative for conventional fossil fuels. Ethanol and Biodiesel are the most commonly
used types of Biofuels. In the United States, Congress had adopted extensive mandates
and subsidies to get a biofuel industry off the ground and other countries have also
adopted renewable fuel policies [14]. Biofuels are clean and can be produced in local
communities. They can be produced from the resources available from the local
communities. Biofuels can be used to power farms, local workshops, in electricity
generation machineries and vehicles.
3.2 First Generation of Biofuels
The fuels that were derived from starch, sugar animal fats and vegetable oils are known
as first generation biofuels. The first generation biofuels are primarily Ethanol, Biodiesel,
vegetable oil, biogas, syngas. Ethanol and Biodiesel are the most common biofuels.
Ethanol is made from corn or sugar cane while biodiesel is made from vegetable oil.
Biofuels are more beneficial compared to fossil fuels. When Biofuels are burned they do
22
not add up to the greenhouse gas to the atmosphere. However since the rise in food prices
led the industry experts started blaming higher prices for food, hunger and instability in
politics to the diversion of crucial crops towards the production of biofuels. One reason
being the use of good farmlands for the production of biofuel crops.
Ethanol:
Ethanol, an alcohol, is a form of biofuel that is made by fermenting carbohydrates rich
biomass. This process of fermenting is very similar to brewing of beer. A common
method of making ethanol is from the starch present in corn grain. Ethanol is a high
performance fuel that is used in vehicles. It increases the octane rating of a petroleum
based fuels when used as additive. Higher the octane rating of a fuel slower it will burn
and thus reducing knocking of the engine. It reduces toxic emissions from exhaust of the
vehicles. Research is being done to make ethanol from cellulose and hemicellulose which
forms the major part of plant matter.
Biodiesel:
Biodiesel is a form of renewable fuel that can be produced domestically. It can be
manufactured from renewable sources like vegetable oils, recycled restaurant greases or
animal fats. It is a cleaner burning alternative to regular petroleum based diesel fuel. It is
not only cleaner form of renewable fuel but it is also biodegradable and nontoxic. The
toxic emissions are reduced by using biodiesel instead of the conventional petroleum
diesel. The energy balance that biodiesel provides is excellent. The amount of energy that
biodiesel contains is 3.2 times more than that is required to produce it. Biodiesel is also
energy efficient and hence it can be used to extend the supply for conventional petroleum
23
based diesel. The most common type of biodiesel blend in USA contains 20% of
biodiesel and 80% of the petroleum diesel. This blend is also known as B20. B20 is
popular because it represents a good balance in cost, emission, cold-weather
performance, materials compatibility, and ability to act as a solvent [14].
Biodiesel is a legally registered fuel and fuel additive with the United States
Environmental Protection Agency (EPA) [16]. The EPA registration is neither dependent
on the type of raw material used nor the process of production used, however it depends
on whether or not the biodiesel produced meets the standards defined.
Figure 3.1: U.S Biodiesel Production, Exports and Consumption
The Figure 3.1 gives a statistics for production, exports and consumption of biodiesel in
USA. The federal Renewable Fuel Standard requires at least 1 billion gallons of biodiesel
consumption in the USA referred to as biomass-based diesel [16].
24
The process of production of biodiesel involves conversion of oils and fats into chemicals
called long chain mono alkyl esters also known as fatty acid methyl esters. This process
of conversion is known as transesterification.
Figure 3.2: Schematic of Biodiesel Production Path
The figure 3.2 shows a schematic for the production of biodiesel. When the raw materials
like vegetable oil or restaurant grease is reacted with an alcohol like Methanol in the
presence of a catalyst like Sodium Hydroxide or Potassium Hydroxide it results in the
production of crude biodiesel. This crude biodiesel undergoes a refining process which
results into biodiesel that can be used as fuel for vehicles. A co-product of this process is
Glycerin which finds its usage in pharmaceuticals, cosmetics and other applications.
Biodiesel is available in retail fuel stations for use.
25
Figure 3.3: Average Emissions Impact of Biodiesel for Heavy-Duty Highway Engines
By using biodiesel there is substantial reduction of emission of unburned Hydrocarbons,
Carbon Monoxide, Particulate Matter and other forms of toxic and harmful emissions.
Biodiesel usage also reduces the greenhouse gas emissions.
Nearly half of the petroleum is imported from foreign companies by the USA. Out of
these, two-thirds is used for fueling of vehicles in the form of gasoline and diesel. This
dependency can result in increase in fuel prices, supply disruptions, trade deficiency and
other issues. Production of biodiesels can provide a solution to this problem. Biodiesel
can be locally produced in USA. It can be used as fuels for traditional diesel engines and
thus being useful as a substitute for petroleum diesel. Biodiesel can thus help in reducing
dependence on foreign supply for petroleum diesel.
26
Biogas:
Biogas is also known as renewable natural gas. Anaerobic digestion of organic matter
results in a gaseous product known as biogas. Biogas can be used to generate electricity,
energy and can also be used as fuel for vehicles. Biogas is called renewable natural gas
when it is produced to the purity standards. It can be used as an alternative fuel for
natural gas vehicles. The main components of biogas are methane, carbon dioxide along
with traces of other gases like hydrogen, carbon monoxide and nitrogen.
Biogas can be produced by decomposition of organic matter. This organic matter can be
sewage, waste available from agriculture and industries, municipal solid waste and
animal waste.
27
Chapter 4
SOLAR POWER
The source of solar power is sunlight. This power is generated by converting sunlight into
electricity. This is done by either using photovoltaic or using concentrated solar power.
Solar systems make use of mirror lenses and concentrate the sunlight to a small beam by
focusing from a large area where sunlight falls. Solar plants were first made in 1980s
[20]. The 354 MW SEGS CSP installed in the largest solar plant in the world, located in
the Mojave Desert of California [20]. Other large CSP plants include the Solnova Solar
power Station (150 MW) and the Andasol solar power station (150 MW) both in Spain.
[20]. The 214 MW Charanka Solar park in India, is the largest photovoltaic plant [20].
4.1 Why Solar Power?
Fossil fuels like coal, natural gas and oil generate majority of world’s electricity supply.
Factors like hike in prices, dependence on imports from a limited number of countries
where there is significant fossil fuel supplies in few countries and environmental
concerns over the climate changes. As a results of these challenges due to the generation
of electricity from fossil fuels, many organizations around the world not only government
but also non-government organizations have moved their focus to renewable energy
sources and new technologies which support this sources. Solar, biomass, geothermal,
hydroelectric and wind power have a great potential in the area of renewable energy.
Compared to non-renewable energy, which not only pricey but also limited in amount.
28
Solar energy generation is one of the fast growing renewable energy sources for
electricity.
Below are listed the several advantages of solar energy over non renewable energy [21].
a) Less Dependence on fossil fuels
There is no involvement of fossil fuel in the generation of fossil fuels. As a result it is less
dependent on fossil fuels and expensive natural resources. There is a disadvantage that
the amount and timing of sunlight over the day, season and year, but this can be
overcome by properly sized and configured system. These systems care highly reliable
and can provide long term, fixed price electricity supply.
b) Effect on environment
Solar power production generates electricity with a limited impact as compared to other
forms of electricity production [21].
c) Demand and supply
Since the demand in summer is more for electricity, solar energy does not have the
limitation since it is renewable energy source. If the demand is more in case of solar
energy, solar energy plays a much better role in terms of supply and price.
d) Modularity and scalability
As the size and generating capacity of a solar system are a function of the number of
solar modules installed, applications of solar technology are readily scalable and versatile
[21].
29
e) Location independent
Solar power production facilities can be installed at home sites or rather customer sites
which reduces investment considerable. Even to add to that there is no transportation and
production infrastructure. The system can be according to the customer needs, so the
system can be tailored to the people’s needs
f) Subsidiaries from government and non-government organizations
Subsidiaries and incentives are given to promote the usage of solar power. The incentive
program are (i) net metering laws that allow on-grid end users to sell electricity back to
the grid at retail prices, (ii) direct subsidies to end users to offset costs of photovoltaic
equipment and installation charges (iii) low interest loans for financing energy power
systems and tax incentives and (iv) government standards that mandate minimum usage
of renewable energy sources [21].
4.2 How to Generate Electricity from Solar Energy?
Different components are required to convert the solar energy to electricity. We use solar
cell or panels that are preferably used to absorb the sun’s energy, so this allows you to
produce electricity through solar energy. Solar panels are made up of semi-conductive
material and the most common material which is used is easily found Silicon.
These semi-conductor materials contain electrons which are naturally immobile at room
temperature. When photons which are contained in the sun’s rays when come in contact
to the solar panels hit the solar cells, the electrons which are in the silicon get energized
30
and due to which they get conductive. If the energy of these photons are much great
enough that the electrons are able to get free from the bond and hence carry electric
charge through a circuit to the destination.
If the energy produced by the photons are not that great then the electrons contained
within the silicon is not enough for the electrons to be mobilized then it lowers the
efficiency of the solar system as the electric current decreases.
4.3 Distribution of Solar Power
The various topics are shown in the [23].
i) The most favorable belt
The belt between latitudes 15o N and 35o N are the most favorable regions for solar
energy applications. It covers around 3000 hours of sunshine per year.
ii) Moderately favorable belt
The belt lies between the 15o N and the next most favorable region for the purpose. It had
humid and cloud cover frequently. There is around 2,500 hours of sunshine per year.
iii) Less favorable belt
35 o N and 45 o N is the belt where the less favorable lies. It consists of winter where the
solar energy is much less than in the rest of the year.
31
iv) Least favorable belt
Above 45 o N of latitude beyond lies another belt of solar energy. Because of frequent and
extensive cloud coverage there is lesser sunlight during the year and hence there is
reduction in the solar energy.
Figure 4.1 Worldwide distribution of the solar radiation
The above figure 4.1 gives an idea of how solar radiation is distributed over the globe.
32
Chapter 5
GENERATION OF ELECTRICITY USING BIOMASS
5.1 Biomass Energy Conversion Overview
Energy may be in different forms like solid, liquid or gaseous. In fact energy from
biomass also exists in the three forms. The fuel which exists in liquid form is used
directly. Such fuel is used vehicles that travel on road, railroad and airway. They are used
in engine and turbines which are used to run electric generator which are intern used to
produce power. Solid and gases are in the same form or changed to a different form. They
are too used for the production of electric power in turbine-equipped power plants. Also
chemical products are also produced since the biomass is organic in nature. Biomass
which are derived from industries, commercial or urban waste or agricultural or forestry
residues give byproducts as power and sometimes chemicals.
Biomass is also divided into primary, secondary and tertiary. The process of
photosynthesis which occurs in plant produces the primary biomass. This biomass is
mainly found on land. Perennial are short – rotation woody crops and herbaceous crops,
the seeds of oil crops and residue which results from the agricultural products and trees
from the forest.
After the primary biomass is processed, the byproduct can be used as biomass and this is
called the secondary biomass resource. The primary biomass undergoes either physically,
33
Figure 5.1: Renewable Energy World, 2006
34
chemically or biologically. The physical process can be sawdust in mills. Simple
chemical process could be liquor from pulping processes. Manure produced by animals is
considered as biological.
Tertiary biomass includes animal fats and greases, even used vegetable oil, waste
obtained from packaging. Construction sites and demolition debris is a heavy resource of
biomass. So it is mainly the residue obtained from post-consumers.
Various technologies are used to convert biomass resources into power, heat and fuels in
UEMOA countries for potential use [24]. Figure 5.1 gives the Renewable energy World.
5.2 Different Processes Used for Conversion of Biomass into Electrical Energy
Biopower or biomass power is generation of electricity from biomass. There are different
biopower technological pathways available. They are pyrolysis, combustion and
gasification
Pyrolysis – transformation of biomass feedstock materials into fuel (often liquid biofuel)
by applying heat in the presence of a catalyst [25].
Combustion – transformation of biomass feedstock materials into energy through the
direct burning of those feed stocks using a variety of burner/boiler technologies also used
to burn materials such as coal, oil and natural gas [25].
35
Gasification – transformation of biomass feedstock materials into synthetic gas through
the partial oxidation and decomposition of those feedstocks in a reactor vessel and
oxidation process [25].
Amongst these technological pathways direct combustion and gasification are used to
generate electricity and energy from biomass.
Approaches in combustion technologies:
Stoker Boiler Combustion, Biomass-Cofiring and Fluidized Bed Combustion are the
general approaches in combustion.
Stoker Boiler Combustions: Combustion of biomass is done by using a technology
similar to coal-fired stoker boilers. Technology improvements have been made in the
biomass combustion, in case of harmful emission reductions and increased combustion
efficiencies.
Biomass-Cofiring:
This method used biomass fuel burned with coal products in current technology. It has
been matured in Europe and is United States is trying to adopt since it can enhance the
use of biomass and reduce net carbon emissions in power generation.
Fluidized Bed Combustion:
Combustion uses a special form of biomass fuel which is a mix of silica and limestone
along with the application of air.
36
Figure 5.2: Fuelized Bed Combustion
5.3 Biomass Gasification
Gasification has a lot of applications even though its unique. This technology has major
advantages
i) Flexible biomass
Due to the CHP the unit uses synthetic gas to trigger the gasifier units. A variety of fuel
feedstocks, also coal to petroleum coke and biomass is used.
37
ii) Emission are low
CHP which uses natural gas to get fired and also solid-fueled coal units are used which in
turn give out low emissions.
iii) Carbon capture
Gasifier is suitable for captures carbon and sequestration, since carbon dioxide is emitter
in different streams and the disposal takes place normally.
Gasifier is used so that the currently used gas turbines can accept and burn low-BTU
content gas streams. The first successful demonstration project for biomass cogasification was in Varnamo Sweden and it used the process of CHP [25].
Biomass gasification is constructed using any of the technologies given below.
a) Atmospheric pressure circulating fluidized bed gasifier
Commercially the gasifier uses derived fuel, biofuel and wood waste as biomass
feedstock. In Lahti Finland 42 MWe is produced using this method since 1998 [25].
b) Pressurized circulating fluidized bed gasifier (PCFB)
Straw, wood and RDF is used as biomass in this process. Varnoma Sweden produces 6
MWe [25].
38
c) Plasma gasifier
As demonstrated in Japan in 2003, produces 8 MWe and uses a downward moving bed
and plasma bottom torch.
d) Draft type
It is the originally created gasifier and mostly does not fit in the gas turbine usage
because of tar carry over.
Figure 5.3: Flow process diagram for Biomass Gasification
Cost drivers for biomass integrated gasification combined-cycle plant technologies are as
follows:
39
1) Biomass fuel type and uniformity
Processing biomass increases due to the caring nature of biomass fuels. Nature can be
moisture content, varying heating value, handling cost etc. As a result it impacts on the
capital cost of the fuel handling systems and the gasifier process trains. Fuel variability in
the gasification process can also alter process properties, and result in changes to the
required gasifier size.
2) Supply curve for biomass fuel, fuel transport and handling costs
The availability of the biomass around 100-mile radius of the plant is a very optimum to
the cost of the biomass, but this is not possible. So biomass is transported by railroad and
roads to get it to the plant and this adds to the cost of the biomass raw material and hence
increases the fuel price.
3) Long-term fuel supply contract availability
Most of the biomass fuel supply is on contract bases that is it is short duration and
sometimes quality varies. If this is taken care then the gasification projects with be less
costly.
Costs: Gasifiers supporting between 25-40 MW class plant cost at an average of
$2,950/KW with a range of between $3,688/KW to $2,655/KW [25].
5.4 How to Develop the Process Control Systems
Since biomass is a chemical process control system are feasible to use as the processes
becomes very crucial and more important. To automate the process it is very crucial and
40
highly important to use measurements of process outputs or disturbance inputs to make
decisions about the proper values of manipulation inputs.
The development consists of the control strategy of formulating or identifying the
following [26].
i) Control objectives
In the controls we first have to formulate the control theoretically. This is a chemical
process which consists of one or more units. Sometimes many units are used to control
operations. If the control is one unit it may have operations and complexity. If it has more
than many units in such a way that different units operation separately, it reduces the
conflict and operational complexity. Even each of the unit may be divided into more
units, so that it is not a trivial process.
ii) Input Variables
Input variables are classified as manipulated or disturbance variables. Manipulated input
as the name suggest can be used to adjust the control system. A disturbance input is the
vary input in the control system. It also affects the process output but has one
shortcoming. It cannot be adjusted by the control system. Inputs can be used to change
the outputs continuously or at discrete interval of time.
iii) Output Variables
Output variables can be classified as measured or unmeasured variables. Measurements
can be continuous or discrete at interval of time.
41
iv) Constraints
Mostly all processes have constraints on which they operate. They can be classified as
difficult or easy constraints. Few examples of the difficult constraint is the minimum or
maximum flow rate, a value operates between the extremes of fully closed or fully open.
Product composition is a easy constraint or rather soft constraint.
v) Operating Characteristics
Operating characteristics are usually classified as continuous, back or semi-continuous.
Continuous processes can be operated for longer time. This can be done under relative
operating conditions before being close down for doing cleaning if necessary. Example
could be oil refining processes which are operated for 18 months before being shutdown.
Batch processes are dynamic in nature that is, they generally operate for a short period of
time. Examples are beer or wine fermentation, as well as many specialty processed.
A semi batch processes may have an initial charge to the reactor, but feed components.
vi) Safety, environmental and economic considerations.
Safety, environmental and economic considerations are all very important. An hazardous
process may cost more to drive it. For many industries its important to minimize the
energy cost, while producing products that meet certain specifications. Better process
automation control allows processes to operate closer to optimum conditions and to
produce products where variability specifications are satisfied.
42
vii) Control Structure
Control types are of two standard types feed forward and feedback. A feed-forward
controller measures the disturbance variable and send this value to a controller, which
adjusts the manipulated variable. A feedback control system measures the output
variables, compares that the value to the desired output value, and used this information
to adjust the manipulated variable. The desired value of the measured process output is
called the setpoint
Controller
Manipulated i/p
Process
Distributed i/p
Figure 5.4 Control Representation
43
Chapter 6
SIMULINK MODEL WITH BIOMASS
The purpose of this chapter is to review the biomass Simulink model. Simulink is part of
Matlab. Matlab is a programming tool for numeric computation and data visualization.
Matlab is mostly used for linear system analysis.
The main purpose of this chapter is to provide a process control and instrumentation for
the biomass model. The main objective of this chapter intern is to design, and tune the
biomass process and automating the operation of the biomass process. The model is then
executed in Simulink matlab and output waveform are also found in matlab.
6.1 Introduction to Simulink Model
Simulink is useful for control system simulation. So block diagrams can be constructed
and simulated easily.
6.2 Biochemical Reactor
Biochemical reactors are used for a variety of processes, especially waste treatment to
alcohol fermentation. Biomasses which contain minute cells consume substrate which has
good content of sugar or waste chemical and produce more cells. A typical control and
instrumentation diagram of a biochemical reactor is shown in figure 6.1.
44
Figure 6.1: Control and Instrumentation Diagram of Biochemical Reactor
Model:
The modeling equation for the bioreactor is
𝑑𝑥₁
𝑑𝑡
= (µ − 𝐷)𝑥₁
𝑑𝑥₂
𝑑𝑡
(Eq 6.1)
µ𝑥₁
= 𝐷(𝑥₂𝑓-x₂)-
𝛾
where the state variables are
x₁ = biomass (cell) concentration = mass of cells/volume, and
x₂ = substrate concentration = mass of substrate/volume
The manipulated input is
D = dilution rate = F/V = volumetric flow rate/reactor volume.
(Eq 6.2)
45
The disturbance input is
x₂𝑓 = substrate feed concentration.
Two possible expressions for the specific growth rate are monod and substrate inhibition
kinetics, which include
Monod
µ =
µ ᵣₐₓ 𝑥₂
𝑘ᵣ + 𝑥₂
Substrate Inhibition
µ =
µ ᵣₐₓ 𝑥₂
𝑘ᵣ + 𝑥₂ + 𝑘₁𝑥₂²
We can notice that the monod growth rate is a subset of the substrate inhibition model
(𝑘₁ = 0)
On working with the dilution rate as the manipulated input is that the resulting dynamic
model is independent of scale. A reactor volume of 1liter with a flow rate of 0.3
liters/hour has the same dynamic behavior as a reactor volume of 1000 liters with a flow
rate of 300 liters/volume. Thus a small-scale (laboratory or pilot plant) reactor can be
used to predict the behavior of a production-scale reactor.
We are using the following parameter for a substrate inhibition model for this control
study:
46
µ ᵣₐₓ = 0.53hrˉˡ
𝑘ᵣ = 0.12𝑔/𝑙𝑖𝑡𝑒𝑟
𝑘₁ = 0.454 𝑙𝑖𝑡𝑒𝑟/𝑔
𝛾 = 0.4
The steady-state dilution rate is Ds = 0.3 hr ˉ1 (and the residence time is 3.33 hours) and
the feed substrate concentration is x₂𝑓𝑠 = 4.0g/liter.
Steady- state Conditions
The nonlinear process has the following three steady-state solutions (operating points) to
the Eq 6.2 for a dilution rate of 0.3 hrˉ1.
Steady state
Biomass Concentration
Equilibrium 1-wash out
Equilibrium 2-nontrivial
Equilibrium 3-nontrivial
x1s = 0
x1s = 0.995103
x1s = 1.530163
Substrate Concentration
Stability
x2s = 4.0
x2s = 1.512243
x2s = 0.174593
stable
unstable
stable
Table 6.1: Steady-State Conditions
We notice that we definitely do not want to operate a equilibrium point 1. Here there is
no reaction recurring because the cells have been washed out of the reactor. The outlet
substrate concentration is the same as the inlet substrate under these conditions.
Linear Model
The state-space model matrices are
47
µ𝑠 − 𝐷𝑠
µ
A=[
𝑠
−𝛾
B = [𝑥₂
𝑥₁𝑠µ𝑠 ′
−𝐷𝑠 −
µ ′ 𝑥1 ]
𝑠
𝑠
𝛾
−𝑥₁𝑠
]
𝑓𝑠 − 𝑥₂𝑠
where the partial derivative of the specific growth rate with respect to the substrate
concentrate is
𝜕µ
µ mₐₓ 𝑘ᵣ
µ𝑠 ′ = 𝜕𝑥 = (𝑘ᵣ+𝑥₂)²
and where dilution rate is the manipulated input. Different control strategies have been
used to control continuous biochemical reactors. One is based on measuring the biomass
concentrate and manipulating the dilution rate. Another is based on measuring the
substrate concentrate and manipulating the dilution rate.
The biomass concentrate is the measured output and the dilution rate is the manipulation
input. Control simulation is performed using the nonlinear process, so the inputs and
outputs from the process are in physical variable form, while the linear controller design
is based on the use of deviation variables. Dilution rate is assumed to be physically
constrained between 0 and 0.6 hrˉ1.
Stable Steady-State Operating Point
Design of a PID controller to control the bioreactor at equilibrium point 3- the stable
nontrivial point. The steady state which also uses the initial condition for your simulation
is
48
1.530163
]
0.174593
x(0) = [
At this operating point, the state space model is
0
0.9056
A=[
]
−0.75 −2.5640
B=[
−1.5301
]
3.8255
C = [1 0]
D = [0]
Eigen values are found that are -0.3 and -2.2630hrˉ1. So the system is stable and the PID
method for stable system can be used.
Process transfer function is found using the equation
−1.5302𝑠−0.4590
gp(s) = 𝑠²+2.564𝑠+0.6792
After placing the process model in gain and time constant form and recognizing pole-zero
cancellation we find that
−0.6758
gp(s) = 0.4417𝑠+1
We notice that time constant of 0.4417 hr is significantly shorter than the residence time.
Unstable Steady-State Operating Point
49
The steady state is
0.995103
]
1.512243
x(0) = [
At this point, the state space model is
0
A=[
−0.7500
B=[
−0.0679
]
−0.1302
−0.9951
]
2.4878
C = [1 0]
D = [0]
Process transfer function for PID method is
−0.9951𝑠−0.2985
gp(s) = 𝑠²+0.1302𝑠−0.0509
After placing the model in gain and time constant form we find the transfer functions as
5.8644
gp(s) = −5.888𝑠+1
This is the transfer function has a RHP pole at 0.1698 hrˉ1 which is consistent with the
state space model.
50
6.3 Simulink Model Diagram
Proportional and integral terms in the PID controller are a function of lambda (λ). Before
any simulation is run, type a new lambda value. The default term in the Simulink PID
block is kc/τ1.
The Simulink model has two extra blocks; the transport delay block can be inserted in the
feedback loop to illustrate the effects of a measurement time delay.
The following must be entered into the Matlab command window: initial conditions, x1i
and x2i; setpoint for biomass concentration, x1sp; final simulation time, tfinal; substrate
concentrate, x2f; and the IMC filter factor, lambda.
Figure 6.2: Simulink Model
The above model is the first – order process PID based design
51
Where the PI tuning parameter is equal to taup/kps*lambda [26]. The proportional gain
taup is inversely proportional to the lambda, which makes sense. If the lambda is small
the controller gain should be large. Similarly if lambda is large then the controller gain is
small.
52
Chapter 7
SIMULINK RESULTS FOR THE BIOMASS MODEL
The Simulink model in Figure 6.1 is used to run in Matlab. Below shows the graphs of
the reponses at the x1 and x2. We can see also pictorial view with the help of the scope to
the two outputs of the bioreactor. The scope1 shows the inputs to the substrate
concentrate x2 and scope1 shows the inputs to the biomass concentrate x1. this can be
seen in the Figure 7.1.
Figure 7.1: Simulink Model with Scope
53
The reponse shows that a small response change varies with lambda. Done by keeping
the values of taups, kps, x1i, x2i and x1sp constant. Vary lambda form 10, 20 and 30.
a)
Observation with lambda 10
The setpoint x1i = 1.53016; x2i = 1.52; x1sp = 5.
taups = 1; kps = 4; lambda = 10.
Figure 7.2: Small response change at biomass Concentrate x1
54
Figure 7.3: Response change at substrate Concentrate x2
55
b)
Observation with lambda 30
The setpoint x1i = 1.53016; x2i = 1.52; x1sp = 5.
taups = 1; kps = 4; lambda = 30.
Figure 7.4: Response change at x1 with lambda 30 at x1
56
Figure 7.5: Response change at x2 with lambda 30 at x2
57
The response to a small setpoint varies with lambda. For a particular value of lambda
below gives the waveform of how the setpoint change affects the response.
a) Observation with x1i = 0.995013 and x2i = 2.0
The x1sp = 5.
taups = 1; kps = 4; lambda = 10.
Figure 7.6: Response due to change in setpoint at x1
58
Figure 7.7: Response due to change in setpoint at x2.
59
b)
Observation with x1i = 2.0 and x2i = 3.0
The x1sp = 5.
taups = 1; kps = 4; lambda = 10.
Figure 7.8: Response due to change in setpoint at x1
60
Figure 7.9: Response due to change in setpoint at x2
61
Chapter 8
CONCLUSION
Expanding biomass energy to a scale capable of impacting the global emissions of
greenhouse gases will require improvements in the growth of feedstock as well as the
efficiency of conversion pathways. The majority of the losses in current biomass energy
systems are due to the relatively inefficient photosynthesis process, the high energy
requirements of plant processes that support the growth and development of plants, and
industrial energy inputs during cultivation and processing. Engineering plants to more
efficiently produce photosynthetic or microorganisms to directly produce other energy
carriers such as hydrogen could relax many of the barriers associated with land, water,
and nutrient requirements. Biological conversion processes promise efficiencies higher
than thermochemical conversion, but require research to improve microorganisms and
molecular level biological processes.
Advances in understanding of genetics and
biological conversion processes at the molecular level will allow more control over the
efficiency and economics of these pathways. Biomass energy has the potential to make a
significant contribution to a carbon constrained energy future, but technological advances
will be required to overcome the low energy densities and conversion efficiencies
characterizing present and historical utilization.
62
Chapter 9
FUTURE WORK
1. Even we can use the energy created from other resources like geothermal, wind
power and other renewable energy.
2. Solar energy is the best form which can be used as the trigger for the biomass
generation.
3. The block of the biomass given in the chapter 6 which gives the secondary source
of biomass can be further used for generation of biomass for the various process
of gasification, combustion, heat generation.
4. Also can be used to generate biofuel.
63
BIBLIOGRAPHY
1. The Wikipedia link for Renewable Energy [Online], Date Accessed 05/4/2012
http://en.wikipedia.org/wiki/Renewable_energy
2. The Wikipedia link for Wind Energy [Online], Date Accessed 05/10/2012
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