INTRODUCTION

Geothermal comes from Greek word,Geo(earth)+thermal(heat).

originates from the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface.

The first attempt to generate electricity from this energy source did not occur until the 20th century.

Prince Piero Ginori Conti tested the first geothermal generator on 4th July 1904.

INTRODUCTION contd..Heat from the earth crust used as natural and constant source as any other renewable sources.

Outer crust of earth has average thickness of 32 Km and below that is magma.

As we go deeper, the temperature increase by 1◦c for every 35 to 40m depth.

Taping heat is clean and sustainable way to reduce fossil fuel use.

Worldwide, geothermal plants have the capacity to generate about 10 GW as of 2007, and in practice generate 0.3% of global electricity demand

8000 MW installed capacity in 20 countries (2800 MW in USA).

In California – 5% of electricity from geothermal.

Yellow spotted are some of the GPPs found around world

SITE SELECTION

Slope limitations(less than 15%).

Location of site near the river is not suitable.

Absence of fault(cracks) in the earth’s crust.

Faraway from population Center.

Road accessibility.

Availability of advanced technologist.

Availability of hot springs and geysers.

The fluid temperature(180 degree Celsius) should

be available at depths not exceeding 3 Kms.

Principle of operation

GPP use steam produced from reservoir of hot

water found a couple of miles below the earth’s

surface to rotate the turbine that activate generator.

Various type of cycles have been suggested .

Two most important cycles, which are being used

in practice are:

1)Indirect condensing cycle.

2)Direct non-condensing cycle.

Indirect condensing cycleInvolves the use of heat exchanger.

About 15% to 20 % of stream power potential had to

be sacrifice in exchanger.

This cycle was considered economical, because of the

recovery of minerals and non-condensable gases.

Through advancement in technology and declining

attraction of mineral extraction, this cycle has been

rendered obsolete.

The steam after striking the turbine is condensed back

into water and injected back into the ground.

Direct non-condensing cycleSimplest, cheapest and most widely used geothermal cycle.

Bore steam either from direct bores or after separation from wet bores is passed to the turbine and exhausted to the atmosphere.

Water should be pumped into artificial volcanic crater s and then turned into useful stream.

Geothermal power plant are unattended and don't need full time supervision.

Stream temperature and stream line drains should be closely monitored, for any indication of water.

Direct non-condensing cycle contd..

Rated turbine throttle pressure is maintained by connecting sufficient number of wells to the supply line of unit.

Unit should be inspected for every three years.

It can be operated at high annual load plant load factor of order of 90%or more with proper maintenance.

Types of Geothermal Power Plants

Geothermal technology has three varied ways of taking geothermal energy, they are;

1)Dry Steam Power Plant;Simplest.Use steam directly as it comes out.Suitable when geothermal steam is not mixed with water.Efficiency – 30 %.Efficiency effected by presence of CO and hydrogen sulphide.Generates about 35 – 120 MW.

Fig. Dry steam power plant

2)Flash Steam Power Plant

Use very hot steam (300° F) and hot water resources.

Geothermal resource in liquid form.

Liquid changes into steam in flash tank.

Most common type.

Minute amounts of carbon dioxide, nitric oxide, and sulfur are emitted, but almost 50 times less than at traditional, fossil-fuel power plants.

Generates about 5 – 100 MW.

Fig. Flash steam power plant

3)Binary Cycle Power Plant

Geothermal resource not hot enough to produce steam.

Or contains too many chemical impurities.

Hot water is passed through a heat exchanger.

Secondary fluid vaporizes, turns the turbines, which drives the generator.

Remaining fluid is condensed and returned to the reservoir.

More expensive and has higher efficiency.

Generates about few hundred KW to 5 MW typically.

Fig. Binary steam power plant

Complete layout of typical GPP

Combined operation of GPPComposite power system can be supplied more economically by combination of:

Base load plant characterized by high fixed cost and low variable cost.

Peak load plant characterized by low fixed cost and high variable cost.

In GPP all production cost are fixed cost, with zero variable cost.

They are ideally rated as base load plants.

They can achieve annual plant load factor of 90% or more, more than thermal and nuclear.

It is the least objectionable form of power generation available at present.

Advantages of using Geothermal Energy

Less area is required

Clean source of power

No fuel is required

Unhindered production of power

Additional capacity

Electrification of the remote places

Saving money

Disadvantages of using Geothermal Energy

Unavailability of large/grouped geysers and hot spring

Require of experts and expensive drilling equipments

Construction of roads to faraway sites

Disruption of ground water level

Has environmental impact

Makes the area uninhabitable

Not truly renewable resources

Poor overall efficiency

Questions and Recommendations

??Presented by:

Sangchu

Pema Dorji

Sangay Dorji

Karma Dugyel

Tshewang Dorji