Geothermal Energy Advantages,Disadvantages

Advantages of geothermal energy over other energy forms:

1) Geothermal energy is quite cheaper which means the cost of geothermal power is constant over the lifetime of the facility since no fuel is purchased and facility costs are largely fixed 

2) It is least polluting as compared to other conventional energy sources 

3) Geothermal energy is amenable for multiple uses from a single source 

4) Geothermal power plants have highest annual load factors of 85% to 90% compared to 45%-50% for fossil fuel plants. 

5) It is versatile in it's use 

6) It delivers greater amount of net energy from it's system as compared to other alternative or conventional systems. 

7) Geothermal energy from the earth's interior is almost as inexhaustible as solar or wind energy, so long as it's sources are actively sought and economically tapped. 

Disadvantages: 

1) The efficiency of power generation is less about 15% compared to 35%-40% for fossil fuel plants.

2) Noisy operation due to drilling 

3) Large area is required for the geothermal power generation 

4) The withdrawal of large amounts of steam or water from a hydrothermal reservoir may result in surface subsidence or settlement. 

5) Some geothermal plants do produce toxic solid materials, or sludges, that require disposal in approved sites.

Geothermal Energy introduction

GEOTHERMAL ENERGY:

Geothermal comes from Greek words Geo meaning earth and thermal meaning heat. Geothermal energy is primarily heat energy from earth's own interior. 

INTRODUCTION: It is classified as renewable because it comes from the earth's interior which is almost inexhaustible as like solar and wind energy, so long as its sources are actively sought and economically tapped. As we travel down earth's surface radially, there exists a temperature gradient of 0.03 deg c per meter. Thus a 30 deg c increase in temperature can be obtained per km depth from the earth crust. There are many local hot spots just below the surface where the temperatures are much higher than expected. Ground water, when comes into contact with hot spots, either dry or wet steam is formed. By drilling holes to these locations, hot water and steam can be tapped and these can be used for power generation or space heating. 

Heat transfer from the earth's interior is by three means 1. Direct heat conduction 2. Rapid injection of ballistic magma along natural rifts penetrating deep into earth's mantles. 3. Bubble like magma that buoys upwards towards the surface.

IMPORTANT ASPECTS OF GEOTHERMAL ENERGY 

FORM OF ENERGY Thermal energy in the form of hot water, steam, geothermal brine, mixture of these fluids. 

AVAILABILITY Generally available deep inside the earth at a depth more than about 80 km. Hence, generally not possible to extract. In a few locations in the world, deposits are at depths of 300 to 3000 m. Such locations are called geothermal fields. 

METHOD OF EXTRACTION: Deep production wells are drilled in the geothermal fields. The hot steam/water/brine is extracted from the geothermal deposits by production wells, by pumping or by natural pressure. 

GEOTHERMAL FLUIDS Hot water Hot brine Wet steam Mixture of above 

RANGE OF GEOTHERMAL POWER PLANTS INSTALLED CAPACITY 5 MW to 400 MW 

AVERAGE GEOTHERMAL GRADIENT 30 deg c  per 1000 m length 

GEOTHERMAL ENERGY RELEASED THROUGH EARTH'S CRUST About 0.06 W/m 

TOTAL GEOTHERMAL RESERVES IN THE EARTH 4x(10^15) MJ (estimated) 

RATE AT WHICH THE RENEWABLE ENERGY CAN BE TAPPED FOR PRODUCTION OF ELECTRICITY 2x10^12 to 10x10^12 MJ/year (estimated) 

TYPES OF GEOTHERMAL ENERGY DEPOSITS 

Hydro thermal: hot water and steam, hot brine. 

Petro thermal: hot dry rock (HDR)

Geothermal Energy and the power from the earth

Geothermal Energy: Power from the earth

•Geothermal energy is the energy produced by heat within the Earth.

•In some areas, deposits of water in the Earth’s crust are heated by geothermal energy.

•The United States is the world’s largest producer of geothermal energy.Although geothermal energy is considered a renewable resource, the water that is used must be aged carefully so that it is not depleted. 

•Geothermal power plants generate electricity using the following steps.

1)Steam rises through a well as in the figure the red arrow indicates the flow of steam rising.

2)The raised steam drives turbines which generates electricity and left over liquid is pumped back in to the hot rock as shown in the diagram by blue arrow.

3)The left over liquid water is returned to earth's crust because it can be reheated by geothermal energy and used again.