GEOTHERMAL GENERATION TECHNOLOGY - CHOOSING THE BEST TECHNOLOGY FOR YOUR

CIRCUMSTANCES

BY Albert Mugo

Business Development & Strategy Director -KENGEN

WHAT IS GEOTHERMAL?WHAT IS GEOTHERMAL?

Geothermal is energy from the EarthGeothermal is energy from the Earth ’’s interior!s interior!

Benefits of Geothermal Energy

� Provides clean and safe energy using little land

� Is renewable and sustainable

� Generates continuous, reliable “base load” power

� Conserves fossil fuels and contributes to diversity in

energy sources

� Indigenous resource

� Offers modular, incremental development and

village power to remote sites – wellhead generators

Geothermal Development in Kenya

Introduction

� Total installed capacity

2010 = 202 Mwe�KenGen = 150 MWe

�Orpower 4 = 48 Mwe

�ODC = 4 Mwe

� Capacity under

construction�KenGen = 280 MWe at

Olkaria

�KenGen = 2.5 MWe at

Eburru

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Kenya’s Geothermal Potential

� Geothermal potential areas (>20 fields ≥ 7,000 MW) within Kenya Rift.

� Current installed geothermal power: KenGen 150 MW

� IPP’s 52 MW.

� Only a small fraction of the estimated resource has been harnessed.

Geothermal Systems - Classification

� High temperature > 180 deg C�Used mainly for power generation –

single flash and binary

� Medium temperature <180 – 80deg

C�Mainly binary systems

� Low temperature < 80 deg�Binary systems and direct uses

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Geothermal Indicators - Temperature

SulfurSulfur

Hot Springs

Hot GroundHot Ground

Geysers

FumarolesFumaroles

Generation Technologies

Generation technologies

� Current Technologies �Steam Flash cycle

�Binary cycle

�Combined cycle

�Wellheads

�Back pressure

� Emerging technologies�Hydrothermal

�Enhanced geothermal systems (EGS)

�Hot dry rock (HDR)

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� Based on geothermal system

� Basic Considerations�Temperature

�Pressure

�Fluid Chemistry

�Permeability *

� Other Considerations�Efficiency of conversion

�Environment

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CHOICE OF GENERATION TECHNOLOGY

Type of Plants 1:Condensing Dry Steam Power Plant

� Most commonly used

� Utilizes pressure�High temperature systems

where the temperature is

above 180 deg C

�Use dry steam or two phase

i.e. water and steam

�Best efficiency of conversion

≈ 1,800 mUSD/MW

�Large amounts of water and

heat lost to the atmosphere

Generator

CondensedSteam (Water)

Electricity

TurbineGenerator

SteamCondensedSteam (Water)

ElectricitySteam

Separated Water

Steam

CondensedSteam (Water

HotWater

TurbineGeneratorFlashTank Electricity

Condensing Flash Steam Plant (Olkaria I & II)

PRODUCTIONWELL

GA

S E

XTR

AC

TO

R

COOLING TOWERS

CHF

IntermediateTemperature

Cold Surface Water

Surface Rock

High TemperatureReservoir

GASES

CONDENSER

HOT CONDENSATE

PUMP

PUMPTURBINE GENERATOR

SEPARATOR

WATER

STEAM

MAIN STEAM

COOLEDCCONDENSATE

STEAM FROMOTHER WELLS

FLOW DIAGRAM

POWER TRANSMISSION(TO NATIONAL GRID)

GENERATED ELECTRICITY

CHF

IntermediateTemperature

Cold Surface Water

Surface Rock

High TemperatureReservoir

CHF

IntermediateTemperature

Cold Surface Water

Surface Rock

High TemperatureReservoir

RE-INJECTIONWELL

RE-INJECTIONWELL

STATIONTRANSFORMER

14

Olkaria II Power Plant Olkaria II Power Plant 105 MW

Olkaria I Power station (45MW) – Oldest Geothermal plant in Africa

Types of Plant 2:Binary Cycle Power Plant

� Used in both high and low

pressure

� Utilizes temperature�Maximizes power out put

�Lower efficiency of

conversion

�Maximum conservation of

water

�Can also use separated brine

� Limitation�Chemistry - Heat exchanger

can be clogged by scaling

Binary Vapor

TurbineGeneratorElectricity

Binary LiquidHeat Exchanger

CooledWater

HotWater

Binary vapor outto turbine

Hot geothermalwater in fromproduction well

Geothermal water out to injection well

Binary liquid infrom condenser

Binary Cycle Power Plant:Heat Exchanger

Binary Cycle Power Plant: Aluto Langano –Ethiopia (8MW) & Olkaria III –

Kenya (13MW)

COOLINGWATER / AIR

PRODUCTION

INJECTION

BINARYTURBINE

Isopentane

Steam and water

HEAT EXCHANGER

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Oserian Power Plant 2MW� Binary plant owned

by Oserian Flower Farm

� Commissioned July 2004

� Steam well leased from KenGen.

Type of Plant 3; Combined cycle plant

� Uses both flashing and binary cycles�Eliminates use of condenser in flash cycle = back

pressure

�Efficient in energy conversion and conservation of

geothermal fluids – Best on Environment

�Most efficient of all plants – maximum power

output

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Conventional Geothermal Steam Power Plant Combined Cycle Geothermal Power Plant

Type of plant 4: Back Pressure

� Used in high temperature systems for reservoir testing

during development for early generation as well head

generator�The earliest geothermal plant type

�Easy to install

�Less efficient than the condensing type

�Can be more efficient than the binary type

�Can be combined with a binary

�Wastes both heat and water

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Other geothermal Systems

� Enhanced geothermal systems – The most abundant

and uses natural geothermal gradient �Plant type – mainly binary

� Hot Dry rock (HDR) systems – in low permeability; �mainly binary plants

�Scaling is a major problem

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� These use either; Steam flash, binary or combined

cycle

� Wellhead generators – used on a single well for

early generation or reservoir testing

Early Generation Strategy: Installation of Wellhead Generators

� Concept; to utilize existing wells before

construction of main plants–Use makeup wells for early generation

–Use of wells that cannot be connected to main steam

system

� KenGen intends to install 15 wellhead generators

= 75 MW

� Pilot plant already under construction

� Installation of all generators to be completed by

June 2011

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5 MW WELL HEAD GENERATING PLANT

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PRODUCTION WELL

Separator

Turbine and Generator

Condenser Cooling tower

Reinjection Well

Silencer

Electrical system

Plant efficiency

Geothermal turbine technologies

Efficiency

THANK YOU