Important terms used in air compressors

An air compressor is a machine used to compress the air and raise its pressure. The compressed air is used for many purposes such as for operating pneumatic drills, riveters, road drills, paint spaying, in starting and supercharging of internal combustion engines, in gas turbine plants, jet engines and air motors etc. It is also utilised in the operation of lifts , rams, pumps and a variety of other devices. In industry, compressed air is used for producing blast of air in blast furnaces and bessemer converters.

Important terms used in air compressors frequently 

The following important terms are frequently used in air compressors: 

Inlet Pressure: It is the absolute pressure of air at the inlet of a compressor. 

Discharge Pressure: It is the absolute pressure of air at the outlet of a compressor. 

Compression Ratio or Pressure Ratio: It is the ratio of discharge pressure to the inlet pressure. Since the discharge pressure is always more than the inlet pressure, therefore the compression ratio is more than unity. 

Compressor capacity: it is the volume of air delivered by a compressor and is expressed in cubic meter per minute or cubic meter per second. 

Free air delivery: It is the actual volume delivered by a compressor when reduced to the normal temperature and pressure conditions. The capacity if a compressor is generally given in terms of free air delivery. 

Swept volume: It is the volume of air sucked by the compressor during its suction stroke.

Mean Effective pressure: It is the ratio if the work done per cycle to the stroke volume of the compressor  

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Impact of Renewable Energy Sources on Global Warming in India

 A brief story of global warming- global warming skepticism 

Of all the forecasts of global environmental disasters made from time to time, the one which aroused the most widespread skepticism was about global warming. Even as several well-meaning people took it seriously- some rather too seriously- a whole lot of other scientists and policy-makers dismissed it as over-exaggeration. During 1970s through 1990s, those who believed in global warming talked of it as soon as they felt a day was hotter than the previous one. Others believed that even if the world continued to produce gases which cause greenhouse effect, our oceans would keep assimilating them and no long-term global warming will ensue. They dismissed episodes of extreme climate as the usual fluctuations that occur in nature. Indeed during the late 1960s and early 1970s, it was the forecast of global cooling that had captured public imagination (Gribbin, 1975; Thompson, 1975; Peterson et al, 2008).

Global Warming A Scientifically Accepted Fact  

During the last 20 years, the balance of evidence has gradually and decisively shifted towards global warming. It is now a scientifically accepted fact that global warming is indeed occurring and that it will have long-ranging impacts on the earth’s ecosystems. There is no longer a disagreement on the existence of global warming; if there are disagreements, they are on the extent of harm global warming will cause. There is also near-complete consensus that use of fossil fuels is the principal cause of global warming and unless the emissions to atmosphere of CO₂ and other greenhouse gases are drastically reduced, global warming will progressively increase and lead us to our doom.

Adverse Effects of Global Warming 

      So, global warming has already hit us, and it is beginning to hit us harder. It has also produced another monster which may me even more destructive than temperature rise and ocean acidification .Given that 70% of the world is covered by oceans, any disturbances in oceans can have bigger and ‘deeper’ effects on earth than the disturbances in the rest of the 30% of the world!

Global Warming and Renewable Energy Source: India and the world 

Once again, there is a groundswell of demand for ‘alternative energy sources’, particularly the ‘renewable’. Even before global warming became an accepted reality in the post-modern era, fossil fuels were almost universally perceived as highly ‘unclean’ fuels responsible for numerous forms of gross pollution, including acid rain. On the other hand, non-conventional energy sources, especially the renewable energy sources, have created a ‘clean’ image regarding environment impacts. But obviously there is exception, one of the major exceptions is the large hydropower projects. Past experience showed us that they can be catastrophic for the environment. Now it is believed that mini-hydel and micro-hydel projects can be proved harmless for alternatives.

• Hydroelectric Power Facts - Advantages and Disadvantages 

The tide has turned so strongly in favour of renewable that for the first time ever since the dawn of the fossil fuel era over two hundred years ago, renewable energy technologies have attracted more investment globally, ($140 billion) in 2008, compared with $110 billion for fossil fuel-based technologies according to figures released by the United Nations, June 2009 (Macalister, 2009). Wind energy has attracted the highest new worldwide investment, $51.8 billion, followed by solar at $33.5 billion. Biofuels are the next popular investment, winning $16.9 billion. There is as much as a 27% rise to $36.6 billion in developing countries led by China, which pumped in $ 15.6 billion, mostly in wind and biomass plants. India’s overall spending on renewable energy has risen to $4.1 billion 2008, 12% up on 2007 levels.

India has started Spending on Renewables to reduce global warming and pollution 

         According to India’s Ministry for New and Renewable Energy (MNRE, 2009), India has a potential of generating over 82000 MW (8.2 GW) of power from just wind, small hydro and biomass (Table 1.1). Of this, only 6100 MW, i.e., a mere 7.4% of the potential is presently being realized. There is a similarly vast potential for dispersed units, but only a small fraction has been realized (Table 1.2). Which is why India has stepped up its spending on renewable, just as the rest of the world has. It as if the world is preparing to stake it’s all on renewable in the hope that renewable will save it from the looming disaster of global warming and irreversible pollution.

Table 1.1 : Potential of Power Obtainable from wind, small hydro and biomass in India vs its actual realization at present (MNRE, 2014)

Table 1.2 : Potential utilization of biogas and dispersed solar energy, biomass and wind energy systems in India and the present state of its realization (MNRE, 2014)

These links gives glimpses of the renewable energy sources. It also addresses these tricky questions: are renewable energy sources really as benign as is widely believed? Are they really a sure answer to the problem of global warming?

• Renewable Energy: the great green hope for clean environment
• What are the cheapest sources of non-conventional energy - Biomass  

Is there any major proof that Renewables are environment friendly ? 

One may say that for thousands of years when humankind was dependent almost totally on renewable, the world was much less polluted and there was no global warming. Is this itself not a major proof that renewable are environment-friendly?

Sadly, it isn’t!

The reason is that till the mid-18^th century the global population and the per capita energy consumption, hence the total global energy consumption, were small fractions of what they are today. Had we used fossil fuels at the rate renewable sources were being used till 1850, we would not have experienced global warming. But at the present rate of population growth and per capita consumption no source of energy, however, clean it may be, can bail us out of rapidly increasing global warming and other forms of pollution. 

India, in its National Electricity Policy 2005 (MNRE, 2009), has set for itself the goals of, among other things: (a) access to electricity for all and (b) increase in per capita availability to over 1000 units by 2012. In other words, we want to greatly enhance energy consumption. In doing it, we will have to face the inevitable consequence of more serious pollution. And, as we will bring out in the next articles that renewable aren’t as squeaky clean as are popularly believed. Nor is the use of renewable energy sources on a large scale an insignificant burden on the environment.

• Solar Air Heater Classification and Advantages
• Solar pond pump-features of solar fountain pump

   

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Solar Concentrator Classification: Advantages of Solar Concentrator

Introduction: Definition of Solar Concentrators:

Solar Concentrator is a device which concentrates the solar energy incident over a large surface onto a smaller surface. The concentration is achieved by the use of suitable reflecting or refracting elements, which results in a increased flux density on the absorber surface compared to that existing on the concentrator aperture. In order to get a maximum concentration an arrangement for tracking the sun’s virtual motion is required.  An accurate focusing device is also required. Thus a solar concentrator consists of a focusing device, a receiver system and a tracking arrangement. Temperature as high as 3000 degrees Celsius can be got from a solar concentrator. So they have potential applications in both thermal and photovoltaic utilization of solar power at high temperatures.

Solar concentrating devices have been used for a long time. In Florence as early as 1695, a diamond could be melted by solar energy. Lavoisier carried out a number of experiments with his double-lens concentrator. The knowledge concentrator dates back even time of Archimedes, whose book "On Burning Mirrors" is an evidence of this fact. Many uses of concentrators were reported in the eighteenth and nineteenth centuries, particularly in heat engines and steam production. The advantages of concentrator are as follows: 

The advantages of solar concentrator

1. It increases the intensity by concentrating the energy available over a large surface onto a smaller surface (absorber)

2. Due to concentration on a smaller area, the heat loss area is reduced. Further, the thermal mass us much smaller than that of a flat plate collector and hence transient effects are small.

3. The delivery temperatures being high, a thermodynamic match between the temperature level the task occurs.

4. It helps in reducing the cost by replacing an expensive large receiver by a less expensive reflecting or refracting area.

Disadvantages of Solar Concentrator

However, concentrator is a optical system and hence the optical loss terms become significant. Further it works on beam component of solar radiation, resulting in loss of diffuse component. Although the basic concepts of flat plate collectors are applicable to concentrating systems, a number of complications arise because of non-uniform flux on absorbers, wide variations in shape, temperature and heat loss behavior of absorbers and finally the optical considerations in the energy balance conditions. It may be noted that higher the concentration of the collector, higher is the precision of optics and more is the cost of the unit. In addition to the complexity of the system, the maintenance requirements are also increased.

Classification of solar concentrator

Solar concentrators may be classified as (i) tracking type and (ii) non-tracking type. Tracking may be continuous or intermittent and may be one-axis or two -axes. As the sun may be followed by moving either the focusing part or receiver or both; concentrators can be classified accordingly. Further the system may have distributed receiver or central receiver.

The concentrators may also be classified on the basis of optical components. 

They may be 

1. Reflecting or refractory type

2. Imaging or non-imaging type

3. Line focusing or point focusing type

The reflecting or refracting surface may be one piece or a composite surface, it may be a single stage or two stage type system and may be symmetric or asymmetric. In practice however hybrid and multistage systems, incorporating various levels of the features, occur frequently.

Types of solar concentrators

There are a number of methods by which the flux radiation on receivers can be increased. Some of them have been discussed here:

• Tracking Concentrators
• Non-tracking Concentrators 

   Tracking Concentrators classification: 

   Tracking Concentrators can be further classified as

• One-axis tracking concentrators (Follow the link for the description)
• Two-axes tracking concentrators (Follow the link and know about all types of two-axes tracking concentrators) 

    Concentrators with one axis tracking 

    These are used to achieve moderate concentration. A few of them have been described below.

i.    Fixed Mirror Solar Concentrator (FMSC)

ii.  Cylindrical Parabolic Concentrator

iii.  Linear Fresnel Lens/reflector
         (Follow the link of one axis tracking concentrator for getting the description of all three concentrators)

Concentrators with two-axes tracking 

           In order to achieve a high concentrators for high temperatures solar processes, concentrators with double curvatures are used. These requires two axes tracking of the sun. Some of these have been described below: 

i. Paraboloidal dish concentrators 

ii. Central Tower Receivers 

iii. Circular Fresnel Lens 

iv. Hemispherical bowl mirror

Non-tracking concentrators classification 

These are classified as follows: 

i. Flat Receiver with booster mirror 

ii. Tabor- Zeimer Circular Cylinder 

iii. Compound Parabolic Concentrator 

iv. V- tough  

Please Read: 

• Solar Pond Pump Features
• Renewable Energy The Next Green Hope 
• Renewable Energy: Graphical Representation 
• Geothermal Energy Pros and Cons 
• Hydroelectric Power Plants Advantages and Disadvantages 
• Solar Air Heater Classification and Advantages 
• Cheapest Source of Renewable energy - Biomass 
• Fixed Dome type Janata Power plant construction 

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Renewable Energy Sources: The Great Green Hope for clean environment

Fossil fuel use is the prime cause of global warming and ocean acidification. Then the obvious solution to that problem is that:

• Either some way is found out to use fossil fuels, but not let the resulting CO₂ escape to the atmosphere, in other words to sequester (catch/lock up) the CO₂ , or
• To find other fuels which do not release CO₂ (or other greenhouse gases) 

Renewable Energy Sources: The Great Green Hope 

The world is trying both the options. The sequestration of CO₂ is very much possible theoretically, it is as of now uneconomical. Moreover, quantities of CO₂ that must be sequestered is so huge that there is no way to store it without serious risks to environment and public safety.

Realizing the limitations of sequestering fossil fuel CO_2, great hope has been pinned on the renewable energy sources. The year 2008 has seen more funds to be allocated globally to renewable – based power generation than ever before. The year also witnessed renewables getting higher share of funds than conventional energy sources for the first time ever.

How tough it is to find replacement which will be as efficient as petrol and diesel, and yet be non-polluting, can be gauged from figure below. It show s that the volumetric energy density, in other words energy packed in each liter of diesel is as much as double of that of ethanol and three times higher than liquid hydrogen. Petrol is more energy-dense than bio-diesel; also ethanol, hydrogen, etc. This means that if vehicles are to be run on liquid hydrogen- which is ultimate aim of most of the R&D- they have to have their tanks three times larger than what they were for the diesel engine. To put in other words, even if we succeed in finding fuels which are cleaner than petrol and diesel, we have little hope of finding fuels which are as efficient as the twoRenewable Energy Sources: The Great Green Hope

Fossil fuel use is the prime cause of global warming and ocean acidification. Then the obvious solution to that problem is that:

Either some way is found out to use fossil fuels, but not let the resulting CO₂ escape to the atmosphere, in other words to sequester (catch/lock up) the CO₂ , or

To find other fuels which do not release CO₂ (or other greenhouse gases) 

The world is trying both the options. The sequestration of CO₂ is very much possible theoretically, it is as of now uneconomical. Moreover, quantities of CO₂ that must be sequestered is so huge that there is no way to store it without serious risks to environment and public safety.

Realizing the limitations of sequestering fossil fuel CO_2, great hope has been pinned on the renewable energy sources. The year 2008 has seen more funds to be allocated globally to renewable – based power generation than ever before. The year also witnessed renewables getting higher share of funds than conventional energy sources for the first time ever.

How tough it is to find replacement which will be as efficient as petrol and diesel, and yet be non-polluting, can be gauged from figure below. It show s that the volumetric energy density, in other words energy packed in each liter of diesel is as much as double of that of ethanol and three times higher than liquid hydrogen. Petrol is more energy-dense than bio-diesel; also ethanol, hydrogen, etc. This means that if vehicles are to be run on liquid hydrogen- which is ultimate aim of most of the R&D- they have to have their tanks three times larger than what they were for the diesel engine. To put in other words, even if we succeed in finding fuels which are cleaner than petrol and diesel, we have little hope of finding fuels which are as efficient as the two. 

Figure: Fuel and Power Sources

Please Read the following articles : 

• Solar Pond fountain Pump - Features 
• Geothermal Energy Pros and Cons 
• Biogas Plant construction 
• Cheapest Renewable Energy-Biomass  
• Flash Steam Type Geothermal energy plant 
• Different Types of Nuclear Reactors 
• Advantages and Disadvantages of Hydroelectric Power 
• Biomass - pros and cons 

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Solar Air Heater Classification and Advantages

This post provides the description and analysis of different types of solar air heaters used in space heating and drying purposes. The Solar air heaters have the following advantages over other solar heat collectors.

Solar Air Heater Advantages 

• The need to transfer heat from working fluids to another fluid is eliminated as air is being used directly as the working substance. The system is compact and less complicated.
•  Corrosion is a great problem in solar water heater. And this problem is not experienced in solar air heaters.
•  Leakage of air from the duct does not create any problem.
• Freezing of working fluid virtually does not exist.
• The pressure inside the collector does not become very high. 
• Thus air heater can be designed using cheaper as well as lesser amount of material and it is simpler to use than the solar water heaters.

Solar Air Heater Disadvantages 

• Air heaters have certain disadvantages also the first and foremost is the poor heat transfer properties of air. Special care is required to improve the heat transfer. 
• Another disadvantage is the need for handling large volume of air due to its low density. 
• Air cannot be used as a storage fluid because of its low thermal capacity. 
• In the absence of proper design the cost of solar air heaters can be very high. 

Solar Air Heater Applications  

The applicability of the solar air heater depends on various factors like high efficiency, low fabrication cost, low installation and operational cost and some other specific factors regarding specific uses. Extensive work in solar air heaters has been done. Various geometries have been proposed and their theoretical investigation is carried out. But it needs commercial exploitation.
 

Solar Air Heater Classification

A conventional solar air heater is essentially a flat plate collector with absorber plate, a transparent cover system at the top and insulation at the bottom and on the sides. The whole assembly is encased in a sheet metal container. The working fluid is air, though the passage for its flow varies according to the type of air heater.
Material for construction of air heaters are similar to those of liquid flat plate collectors. The transmission of solar radiation through the cover system and its subsequent absorption in the absorber plate can be given by expressions identical to that of liquid flat plate collectors. Selective coating on the absorber plate can be used to improve the collection efficiency but cost effectiveness criterion should be kept in mind.
 

Non-porous Type solar air heater

In non-porous type, air stream does not flow through below the absorber plate but air may flow above and/or behind the plate.

In first type, no separate passage is required and the air can flows between the transparent cover system and the absorber plate. ( see the figure). In this heater as the hot air flows above the absorber, the cover receives much of the heat and in turn, loses it to the ambient. Thus a substantial amount of heat is lost to the ambient and hence this air heater is not recommended.
The non-porous type with air passage below the absorber is most commonly used. A plate parallel to the absorber plate is provided in between the absorber and the insulation, thus forming a passage of high aspect ratio.
In another variety of non-porous type air heater, the absorber plate is cooled by air stream flowing on both sides of the plate.  

Depending on the type of the absorber plate, the air heater can be non-porous and porous. Figure below shows the non-porous absorber type air heaters.

It may be noted that the heat transfer between the absorber plate and the flowing air being low, the efficiency of air heaters is less. The performance, however, can be improved by roughening the absorber surface or by using a vee-corrugated plate as the absorber plate. Turbulence induced to the air flow helps increase the convective heat transfer.
The radiative loss from the absorber plate are significant, unless selective coatings are used, decreasing the collector efficiency. Also, the uses of fin may result in a prohibitive pressure drop, thus limiting the applicability of non-porous type.
 

Porous type solar air heater    

The second type of air heaters has porous absorber which may include slit and expanded metal, overlapped glass plat absorber and transpired honeycomb.

The sir heater with porous type of absorber has the following advantages: 

Advantages of porous solar air heater 

• Solar radiation penetrates to a great depth and is absorbed along its path. Thus the radiation loss decreases. Air stream heats up as it passes through the matrix. 

• The pressure drop is usually lower than the non-porous type. 

It may be noted however, that an improper choice of matrix porosity and thickness may cause reduction in efficiencies as beyond an optimum thickness, matrix may not be hot enough to transfer the heat to air stream.

Wire mesh porous bed formed by broken bottles and overlapped glass plate are some examples of porous type absorbers used in Solar air heaters. 

Read these articles for further studies:

• Solar Pond fountain Pump - Features 
• Geothermal Energy Pros and Cons 
• Biogas Plant construction 
• Cheapest Renewable Energy-Biomass  
• Flash Steam Type Geothermal energy plant 

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Solar pond pump-features of solar fountain pump

What is a solar pond pump?

A solar pond pump takes the solar energy from a PV or Photovoltaic panel. Sometimes these pumps are designed as a fountain and sometimes called the solar fountain pump.

A solar powered pond pump can be a great alternative to the conventional pumps. And eventually in the long run it will save the expenses. For the perfect functioning of solar pumps the solar panel should be placed in a location which gets decent sun light.

The size and standard of the solar panel defines the power collected from the solar powered pond pumps. In most cases the power output is moderates and not suitable for big projects. And these devices will not work after sunset. But sometimes they have batteries which keep them running for some hours. 
These are some links where you will find some good solar pumps:

• Solar Pond Pump and Fountains Prices 

The conventional pumps are very much cheap compared to the solar pumps and solar panels. So if you have electricity then conventional mains pumps are the best choice. But I must say if you make the perfect calculations then you will find that solar powered fountain pump is an affordable option. So is it possible to get cheap pond pumps? The answer is yes and no! If you consider the initial cost of the solar pump and solar panel then you will find it very expensive. But when you will compare this cost with the cost of wiring, power lines and most importantly time spent then you will find that solar powered fountain pump is quite affordable with a reasonable price. Solar pond pump works better when the sun is shining the most and certainly you need more water flow when the sun is very hot. So it is reasonable to use solar pumps. 

Features of a solar pond pump

Advantages

• No running cost
• Easy setup procedure
• Great for use in remote areas.
• Perfect for fountains.
• Very little noise.
• No environmental pollution.
• This setup can be used as a dehumidifier when used in indoors.
• Very little maintenance needed.
• Solar pond pump has a relatively long life.

Disadvantages

• Power output is low. Water flow rate is also low in solar pond pumps. 
• Solar pond fountain is not suitable for large projects.
• Cloudy days can cause less power output.
• Expensive.
• Very few companies produce solar pond pump. So the options are limited.
• Cannot be used during night time without battery support.

Features of solar fountain pump

Sometimes the solar panel includes the design of the fountain. So the fountain must be placed in a sunny place. It ensures enough sunlight to fall on the panel.

In some cases the panel and fountain is in separate locations. A cord is used to join the two. As long as the panel is getting enough sunlight the fountain can be place anywhere.

Finally I can say that this fountain pumps have their pros and cons. But in the long run these can be proved very beneficial. Here’s a demo of solar pond pump. 

Please read these article for further study: 

Geothermal Energy Pros and Cons 

Fixed Dome Type Biogas plant construction 

What is the cheapest source of renewable energy ? 

Advantages and disadvantaged of hydroelectric power

Renewable Energy Sources - Graphical Presentation

Different types of nuclear reactors 

Different energy sources - units and conversions 

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Every type of energy has its own advantages and limitations. In this article I will discuss about the pros and cons of geothermal energy.

What is Geothermal Energy?

The earth is a heat reservoir of heat energy in the form of molten interior. Surface manifestation of this heat energy is indicated by hot water springs and geysers discovered at several places. Heat can be experienced from the temperature rise of the earth’s crust with increasing depth below the surface. Radial temperature gradient increases proportionally to depth at a rate of 30 degree Celsius per kilometer. At a rate of 3-4 kilometers water bubbles up; while at a depth of 10-15 kilometers the earth’s interior is as hot as 1000 to 1200 degrees. The core of the earth consists of a liquid rock known as Magma having a temperature about 4000 degrees.

The geothermal heat is transferred to the underground reservoir of water which also circulates under the earth’s crust. Its heat dissipates into the atmosphere as warm water and steam vents up through the fissures in the ground as hot springs and geysers. Limitless heat generation by the magma and by radioactive decay of unstable elements like K40, Th232 and U235 which are abundant in the earth’s crust are forms of geothermal energy and considered as renewable energy resource. 

Before analyzing geothermal energy pros and cons one must have knowledge about structure of the earth’s interior. The earth consists of a series of concentric shells. Its internal structure can be divided into three parts – Crust, Mantle and Core. 

The crust

The solid crust of earth is 70-100km thick and can be divided into continental crust, 20-65 km under the continents and oceans crust 7 km under the ocean basins. The study of the seismic waves has indicated that the earth’s crust underneath continents is thicker than that of that underneath the oceans as seismic waves travels faster in oceanic crust than in continental. The oceanic crust consists of low density rocks (basalts) whereas the continental crusts largely contain the granite. Enormous amount of geothermal energy can be got from the cracks in the earth’s crust. Whenever a geothermal site is drilled. Steam, hot water gush out through the drilled hole and become a source of geothermal energy. 

The mantle 

 For the utilization of geothermal energy we must gain some basic knowledge about the layer underneath the crust. It is called the mantle. The upper rigid part of the mantle extends up to 100km below the separating crust and contains mainly iron and magnesium. The crust and upper mantle form ‘lithosphere’. The lower mantle extending up to 2900 km below the earth’s surface is less rigid and is hotter. This is known as ‘asthenosphere’ and is capable of being deformed. The phenomena of plate tectonics i.e. the movement of the earth’s crust is caused by the movement of the lithosphere over the asthenosphere. 

The core 

It forms about 35% of the earth’s mass and has a radius of 3500km. The outer core is molten or liquid while the inner core (radius 1170 km) is believed to contain nickel-iron alloy. The hot molten rock of the mantle is called magma. The outer core being in the molten state behaves like a liquid responsible for all the earthquakes and volcanic activities. A thermal gradient is created from core to mantle and earth crust. The outward of heat energy from molten hot interior of the earth to the cooler surface makes the earth to operate like a heat engine. That’s one of the advantages of geothermal energy. 

Geothermal Energy Pros and Cons

Actually geothermal energy is a great source of heat found under the earth’s crust. It has its own advantages and disadvantages. Already fossil fuels have started to diminish. And in the future geothermal energy is expected to produce a great amount of power with a relatively cheap rate. Despite all this pros geothermal energy is not used widely because of this problems. 

Geothermal energy disadvantages 

 Geothermal energy is not wide spread source of energy because to utilize geothermal energy perfect equipment and infrastructure is needed. So world wide installation of geothermal plants is not possible. For a efficient geothermal plant thousands of skilled manpower is needed. 
The production of electricity from geothermal plant needs high installation cost because of setting up miles long pipe underneath the earth's crust. To get geothermal energy from a plant high skilled staff in needed which yields high cost. 
Initial research is needed to be done before a setting up a geothermal plant because the natural steam production can be reduced in course of time. Geothermal fields can die and can cause a great deal of loss to the company. 
All the countries cannot use geothermal energy because all countries fall in the geothermal field region. It is a great geothermal disadvantage. 
While digging a geothermal field poisonous gas can come out from the site. This can cause great harm to the life of people and animal. This can also pollute the atmosphere. 
geothermal disadvantages include the problem of transportation. It cannot be transported easily. Once the geothermal energy is extracted from the field it can only be used in the plants of its surroundings.  

 This were the major geothermal energy disadvantages. 

Geothermal energy advantages

• The reliance on the fossil fuel will be drastically reduced if the proper utilization of geothermal energy is ensured. This will help the countries which have to bought a great amount of fossil fuel every year. 
• The less the use of the fossil fuels the less the pollution of the environment. It is the most important advantage of geothermal energy. 
• The running cost of geothermal energy is very low. The price is 80% less than the running cost of plant run by fossil fuels. 
• Geothermal energy can used directly. From an ancient time people are relying on the geothermal energy for heating, bathing and washing. 
• If geothermal energy is properly utilized it will create a great impact on the world economy and creat job opportunities for thousands of people. 

Finally we can say that the world energy consumption is rising. The demand for different energy sources are also increasing. In this situation the use of renewable energy with innovation can solve all the problems. So all the scientists and engineers try to know about geothermal energy pros and cons and make the world a better place.

For more information read :

• Geothermal Energy Pros and Cons 
• Renewable energy sources 
• Flash Steam power plant run by geothermal energy 
• Energy sources and unit conversions 
• Nuclear Power plant : Nuclear reactors 
• Biogas plant construction 
• What is the cheapest source of renewable energy ? 
• Advantages and Disadvantages of hydroelectric power 
• Solar pond pump and fountain features 
• Biomass - pros and cons 

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Fixed Dome type – Janata Model Biogas Plant Construction

Biogas can be a great alternative of fossil fuels. It is already in use in many rural areas. Biogas plants use animal waste, plant waste and human waste. All this wastes have great combustible property. Biogas is an excellent renewable energy source. It is produced by the digestion of waste materials by the means of anaerobic reaction. Anaerobic means the absence of Oxygen. In most of the rural areas cow and buffalo dungs is used as biomass fuel for producing gas. The typical composition of biogas is

Methane - CH₄  (55 - 65 %)
Carbon dioxide CO₂  (30-40%) 

H_{2 ,} H₂S , N₂      (< 10%) 

Biogas Technology involves the bacterial breakdown of the waste materials to produce Methane, Carbon Dioxide and Water . The process involves the following three steps - 

Hydrolysis 

Organics materials contains mainly carbohydrate mainly in the form of cellulose, hemicellulose and lignin. These have very complex structure which is not suitable for absorption. So these matters are converted into simple soluble materials by the action of celluolytic or hydrolytic bacteria. Concentration of bacteria in the organic materials, temperature and pH controls the rate of hydrolysis. pH between 6 to 7 and temperature between 30-40 degree Celsius is good for bacteria to work. 

Acid Formation 

Simple organic materials are turned into acid by acetogenic bacteria. 

Methane Formation 

Methanogenic bacteria turns the acid into methane, carbon dioxide, hydrogen, nitrogen and oxygen. The methane content is 60%. It has high calorific value. Very good for combustion and producing energy. 

Biogas plants 

Biogas plant converts the organic wastes like dung, human waste and plant wastes into a inflammable and it also produces a high quality organic manure as a by product. Most popular two designs of biogas plant is 

1. Fixed Dome Type Biogas plant (Janata Model) (Operates in constant volume)

2. Floating Drum type Biogas plant. (Operates in constant pressure)

In this article I will discuss about the first one - The Fixed Dome type or Janata Model biogas plant. 

Fixed Dome Type Biogas Plant - Janata Model 

This type of biogas plant is very economical is design. It works with the constant volume principle. The main structure is made up of brick and cement masonry. This type of plant doesn't have any moving parts so it is safe from wear and tear. The operating pressure varies from 0 to 100 cm of water column. It is also known as Janata model.  

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What is the cheapest source of renewable energy ? - Biomass

The conventional energy sources are rapidly depleting because of their excessive use in the modern world. And that's why energy or power generation sectors are very much interested in the utilization of renewable energy sources. The conventional energy source includes Natural Gas, Coal, Nuclear Energy, Crude oil etc. The price of these non-renewable fuels is almost touching the sky and getting closer every day. But the price of utilization of non-conventional energy source is not very cheap either. Cheap renewable energy source promises a greater power generation with a cleaner environment.

Please Read : Different Renewable Energy Sources 

Expensive Conventional Energy Sources

Crude Oil

According to Brent Crude Oil the price of one barrel oil was $116! Yeah that’s right and yet oil is expected to remain the predominant source of energy production! The demand of oil will increase by 1.7% in the year of 2025 because of the energy consumption in USA and developing Asia. So it is high time we should look forward for a cheap reliable energy source. 

Natural Gas

Another very attractive non-renewable fuel is Natural Gas. According to the estimation the use of natural gas will be increased by 67% by the year 2025. And therefore the consumption of Natural Gas will be 151 trillion cft. If the consumption increases in that rate then it can be predicted that the life of Natural Gas will be very short on The Earth. 

Coal 

70% Steel production companies uses coal as fuel. 38% of the world’s electricity generation comes from coal. It has high calorific value but at the same time very detrimental to the environment. The high quality coal comes in exchange of a high price!

Nuclear Energy

Uranium is the main fuel for producing energy by nuclear fission reaction.  U₂₃₅ is the primary fuel for nuclear power generation. According to World Nuclear Association the price of 1 kg Uranium stands US $2360 (After conversion enrichment, fabrication)! And it is only the operating cost!

Capital cost + Plant operating cost + External cost = $5300/kW!

Please Read: Different Types of Nuclear Reactors with their Working Principles

Expensive Non-conventional or Renewable Energy Sources

Solar Energy

Sun is the source of energy. The energy from the sun in 19 trillion toe (Ton of Oil Equivalent)/year. And the world’s energy consumption is only 9 billion toe. So a fraction of sun’s energy can fulfill the energy needs. Sun’s energy is extracted mainly by solar collectors. Photovoltaic Cells (PV) are used to store the energy from sun. A single solar panel for household use can cost up to $35000 according to the power output. And this cost does not account the taxes, battery and installation cost! So clearly it is not the cheapest source.

Wind Energy

We get wind because of the pressure difference on the different areas of the earth. The air moves from high pressure to low pressure area and it causes the wind. Wind energy is actually derived from solar energy because Sun heats the earth and creates temperature differences. Hot air expands and rises up and cool air near the oceans rushes and fill that space. That’s how air is circulated. Wind energy potential is not available for use in all the places. Energy density and normality depends on geographical locations. Wind energy is very erratic and irregular. Wind turbine design is very complex and needs a good investment. To create a large plant based on wind turbines, capital intensive technology is needed.

Geothermal Energy

The interior of the earth is full of molten materials. The inner core has solid materials and the outer core is filled up liquid rock named Magma (4000 degree Celsius). Geothermal resources can be divided into this two parts –

•      Liquid dominant resource, which involves

1.        Flash steam power plant 
2.        Binary Cycle Power Plant

•      Vapor dominated resource.

Though geothermal energy is a very good potential source, it has some limitations. Geothermal energy is available in the geothermal sites only.

Ocean Energy

It is kind of hydro energy but it is mainly derived from Thermal radiation of the sun. The surface water of the ocean is heated but the deep ocean water still remains cool. These temperature difference can be used to get OTEC (Ocean Thermal Energy Conversion). From the 19^th century scientists are trying to make this plant work but it is not that popular because of the high cost of the plant. It needs very large diameter pipe which is needed to be submerged a kilometer or more than that to get the cool water.

Cheap Non-Conventional Energy Source

Hydropower source – Tidal Energy

Hydro power can be got from tides and waves. Tidal power plant needs mechanical equipment. This energy is mainly due to the pull of moon.

It can be

•          Single basin single tide
•          Double basin single tide
•          Double basin with the power house in the separating dam.

 It can be proved very useful for the countries having large water reservoirs. The fuel cost is absolutely nil. But the erection of this type of plant can take years. And the rate of return is very low. So the plant owners or government can suffer, running this type of power plant. But it is one of the cheapest source of renewable energy.

Please Read : Advantages and Disadvantages of Hydroelectric Power 

Biomass

According to my studies I think Biomass is the most potential source for energy production. It can be got from forest areas, agricultural residues, Urban wastes, Industrial wastes and natural vegetation.

Biomass – The Cheapest source of Renewable Energy

Yes, I would say biomass because it can use aquatic crops, vegetable oil crops, and animal wastes even human wastes for fuel production. Every day almost 42 million tons of solid waste and 6000 million cubic meters of liquid waste are generated in urban areas. What you will do with all these huge waste materials? If these are utilized to produce power than it would be much better for our environment. And these waste materials are not expensive for sure. Biomass can provide us with biofuels and biogas.

Biofuels

Charcoal – These possess high energy density and can be burned at temperatures high as 600 degrees. Very good for household, commercial and industrial uses.

Briquetting – It can be produced from coconut shells, saw dust, wood chips etc. This are made into high density fuel element.

Vegetable oils – Palm, coconut, cotton, rapeseed and soybean oils can be used as bio fuels. These can mixed with diesel to form premium grade fuel.

Biogas –

Biogas can be produced from digestion of the waste materials like human waste, animal waste and plant waste.  Biogas is mixture of Methane, Carbon dioxide, Hydrogen, Hydrogen Sulfide and Nitrogen. Here Methane CH₄ is predominant (55 -65%). Methane is very clean burner.

Biogas Plants are also very cheap to fabricate. There are two very popular designs to produce biogas

       

•         Floating Drum Biogas Plant (KVIC model) or Chinese Biogas Plant
•         Fixed Dome Type Biogas Plant (Indian Biogas plant design, Janata Model)

Biodiesel

Biodiesel can be produced by mixing organic oil with diesel. Non-edible oil seeds are much preferred for the production of the oil. These produces very small amount of CO₂ and zero sulfur. These fuels have very high flash points so they are easily transported without any danger of self-ignition and combustion. This fuels give high octane ratings. Biodiesel can be produced from Jatropha Curcus, Jojoba, Sunflower, and Soybean and also from peanut. Amongst them Jatropha is the cheapest. It is economically favorable and it costs $0.08/kg of seeds! Where Jojoba seeds costs $3.39/kg.

So Biomass derivatives – biofuels, biogas and biodiesels are the cheapest source of renewable energy.

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