lec 12- hydropower

Chemical Engineering Department | University of Jordan | Amman 11942, Jordan

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Dr.-Eng. Zayed Al-Hamamre

Fuel and Energy

Hydro-power


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Content

Introduction

Historical Overview

Hydro-Power Plants

Environmental Impacts

Economics consideration


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Hydrologic cycle

Introduction


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Ancient romans used water mills

to produce flour from grain

Ancient India

Ancient Rome

Introduction


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Historically… • Pumped hydro was first used in Italy and Switzerland in the 1890's.

• By 1933 reversible pump-turbines with motor-generators were available

• Adjustable speed machines now used to improve efficiency

– Pumped hydro is available at almost any scale with discharge times ranging from several hours to a few days.

– Efficiency = 70 – 85%


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Early Irrigation Waterwheel


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Early Roman Water Mill


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Early Norse Water Mill


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Fourneyron’s Turbine


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DAM TURBINE

POWER HOUSE

INTAKE

GENERATOR

PENSTOCK RE

SE

VO

IR

POWER LINE

TRANSFORMER

Hydropower Plant


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Hydropower plants harness the potential energy within falling water and use classical

mechanics to convert that energy into electricity.

Operating Principle

Water from the reservoir flows

due to gravity to drive the

turbine.

Turbine is connected to a

generator.

Power generated is transmitted

over power lines.


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Hydropower Technology

Hydropower Technology

Impoundment Diversion Pumped

Storage


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An impoundment hydroelectric

power plant consists of a dam

and reservoir.

This type of facility works best

in hilly or mountainous terrain

where high dams can be built

and deep reservoirs can be

maintained.

The potential energy available

in a reservoir depends on the

mass of water contained in it, as

well as on the overall depth of

the water.

Hydropower Impoundment


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Conventional Impoundment Dam


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Schematic of Impound Hydropower


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In a diversion hydroelectric power plant, a portion of the river is channeled through a canal or

pipeline, and the current through this medium is used to drive a turbine

Diversion hydroelectric

Doesn’t require dam

Facility channels portion of river

through canal or penstock


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Diversion (Run-of-River) Hydropower


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Micro Run-of-River Hydropower


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Operation : Two pools of Water

Upper pool – impoundment

Lower pool – natural lake, river

or storage reservoir

Advantages :

o Production of peak power

o Can be built anywhere with

reliable supply of water

The Raccoon Mountain project

Pumped Storage


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Pumped Storage

During Storage, water pumped

from lower reservoir to higher

one.

Water released back to lower

reservoir to generate electricity.


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Pumped Storage System


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Potential

Energy

Kinetic

Energy

Electrical

Energy

Mechanical

Energy

Electricity

Hydropower to Electric Power


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Major Hydropower Producers


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Itaipú Dam (Brazil & Paraguay)


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Guri Dam (Venezuela)


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The theoretical water power PWa,th between two specific points on a river can be calculated

according to

HP Design: Terminology


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HP Design: Terminology

• Head – Water must fall from a higher elevation to a lower one to release its

stored energy.

– The difference between these elevations (the water levels in the forebay and the tailbay) is called head

• Dams: three categories – high-head (800 or more feet)

– medium-head (100 to 800 feet)

– low-head (less than 100 feet)

• Power is proportional to the product of head x flow


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Scale of Hydropower Projects

• Large-hydro – More than 100 MW feeding into a large electricity grid

• Medium-hydro – 15 - 100 MW usually feeding a grid

• Small-hydro – 1 - 15 MW - usually feeding into a grid

• Mini-hydro – Above 100 kW, but below 1 MW – Either stand alone schemes or more often feeding into the grid

• Micro-hydro – From 5kW up to 100 kW – Usually provided power for a small community or rural industry in remote areas away

from the grid.

• Pico-hydro – From a few hundred watts up to 5kW – Remote areas away from the grid.


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Types of Hydroelectric Installation


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Meeting Peak Demands

• Hydroelectric plants:

– Start easily and quickly and change power output rapidly

– Complement large thermal plants (coal and nuclear), which are most efficient in serving base power loads.

– Save millions of barrels of oil

Definitions may vary.

Large plants : capacity >30 MW

Small Plants : capacity b/w 100 kW to 30 MW

Micro Plants : capacity up to 100 kW

Sizes of Hydropower Plants


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Large Scale Hydropower plant


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Small Scale Hydropower Plant


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Micro Hydro Example


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Micro Hydropower Systems

Many creeks and rivers are permanent, i.e., they never dry up, and these are the most

suitable for micro-hydro power production

Micro hydro turbine could be a waterwheel

Newer turbines : Pelton wheel (most common)

Others : Turgo, Crossflow and various axial flow turbines


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Generating Technologies

Types of Hydro Turbines:

Impulse turbines

o Pelton Wheel

o Cross Flow Turbines

Reaction turbines

o Propeller Turbines : Bulb turbine, Straflo, Tube Turbine,

Kaplan Turbine

o Francis Turbines

o Kinetic Turbines


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Classification of Hydro Turbines

• Reaction Turbines

– Derive power from pressure drop across turbine

– Totally immersed in water

– Angular & linear motion converted to shaft power

– Propeller, Francis, and Kaplan turbines

• Impulse Turbines

– Convert kinetic energy of water jet hitting buckets

– No pressure drop across turbines

– Pelton, Turgo, and crossflow turbines


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Types of Hydropower Turbines


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Impulse Turbines

• Uses the velocity of the water to move the runner and discharges to

atmospheric pressure.

• The water stream hits each bucket on the runner. • No suction downside, water flows out through turbine housing after

hitting.

• High head, low flow applications.

• Types : Pelton wheel, Cross Flow


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Pelton Wheels

• Nozzles direct forceful streams of water against a series of spoon-shaped buckets mounted around the edge of a wheel.

• Each bucket reverses the flow of water and this impulse spins the turbine.


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Pelton Wheels

• Suited for high head, low flow sites.

• The largest units can be up to 200 MW.

• Can operate with heads as small as 15 meters and as high as 1,800 meters.


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Cross Flow Turbines

• drum-shaped

• elongated, rectangular-section nozzle directed against curved vanes on a cylindrically shaped runner

• “squirrel cage” blower

• water flows through the blades twice

First pass : water flows from the outside of the blades to the inside

Second pass : from the inside back out

Larger water flows and lower heads than the Pelton.


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Reaction Turbines

• Combined action of pressure and moving water.

• Runner placed directly in the water stream flowing over the blades rather than striking each individually.

• lower head and higher flows than compared with the impulse turbines.

Propeller Hydropower Turbine

Runner with three to six blades. Water contacts all of the blades constantly. Through the pipe, the pressure is constant Pitch of the blades - fixed or adjustable Scroll case, wicket gates, and a draft tube Types: Bulb turbine, Straflo, Tube turbine,

Kaplan


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Bulb Turbine

• The turbine and generator are a sealed unit placed directly in the water stream.

Others…

Straflo : The generator is attached directly to the perimeter of the turbine.

Tube Turbine : The penstock bends just before or after the runner, allowing

a straight line connection to the generator

Kaplan : Both the blades and the wicket gates are adjustable, allowing for a

wider range of operation


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Kaplan Turbine

• The inlet is a scroll-shaped tube that wraps around the turbine's wicket gate.

• Water is directed tangentially, through the wicket gate, and spirals on to a propeller shaped runner, causing it to spin.

• The outlet is a specially shaped draft tube that helps decelerate the water and recover kinetic energy.


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Francis Turbines

• The inlet is spiral shaped.

• Guide vanes direct the water tangentially to the runner.

• This radial flow acts on the runner vanes, causing the runner to spin.

• The guide vanes (or wicket gate) may be adjustable to allow efficient turbine operation for a range of water flow conditions.

Best suited for sites with high flows and low to medium head.

Efficiency of 90%.

expensive to design, manufacture and install, but operate for decades.


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Kinetic Energy Turbines

• Also called free-flow turbines. • Kinetic energy of flowing water used rather than potential

from the head. • Operate in rivers, man-made channels, tidal waters, or ocean

currents. • Do not require the diversion of water. • Kinetic systems do not require large civil works. • Can use existing structures such as bridges, tailraces and

channels.


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Turbine Design Ranges

• Kaplan

• Francis

• Pelton

• Turgo

2 < H < 40

10 < H < 350

50 < H < 1300

50 < H < 250

(H = head in meters)


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The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades.

Turbine and Generator


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Inside the Generator:- The heart of the hydroelectric power plant is the generator. The basic process of generating electricity in this manner is to rotate a series of magnets inside coils of wire. This process moves electrons, which produces electrical current.

Turbine and Generator


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Turbine Ranges of Application


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Turbine Design Recommendations

Head Pressure

High Medium Low

Impulse Pelton Turgo

Multi-jet Pelton

Crossflow Turgo

Multi-jet Pelton

Crossflow

Reaction Francis Pump-as-Turbine

Propeller Kaplan


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Efficiency of Hydropower Plants

• Hydropower is very efficient – Efficiency = (electrical power delivered to the “busbar”)

÷ (potential energy of head water)

• Typical losses are due to – Frictional drag and turbulence of flow

– Friction and magnetic losses in turbine & generator

• Overall efficiency ranges from 75-95%


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Hydropower Calculations

P = power in kilowatts (kW)

g = gravitational acceleration (9.81 m/s2) = turbo-generator efficiency (0<n<1)

Q = quantity of water flowing (m3/sec)

H = effective head (m)

HQP

HQgP

10


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Example 1a

Consider a mountain stream with an effective head of 25 meters (m) and a flow rate of 600 liters (ℓ) per minute. How much power could a hydro plant generate? Assume plant efficiency () of 83%.

• H = 25 m

• Q = 600 ℓ/min × 1 m3/1000 ℓ × 1 min/60sec Q = 0.01 m3/sec

• = 0.83

• P 10QH = 10(0.83)(0.01)(25) = 2.075 P 2.1 kW


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Example 1b

How much energy (E) will the hydro plant generate each year?

• E = P×t E = 2.1 kW × 24 hrs/day × 365 days/yr E = 18,396 kWh annually

About how many people will this energy support (assume approximately 3,000 kWh / person)?

• People = E÷3000 = 18396/3000 = 6.13

• About 6 people


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Example 2

Consider a second site with an effective head of 100 m and a flow rate of 6,000 cubic meters per second (about that of Niagara Falls). Answer the same questions.

• P 10QH = 10(0.83)(6000)(100) P 4.98 million kW = 4.98 GW (gigawatts)

• E = P×t = 4.98GW × 24 hrs/day × 365 days/yr E = 43,625 GWh = 43.6 TWh (terrawatt hours)

• People = E÷3000 = 43.6 TWh / 3,000 kWh People = 1.45 million people

• (This assumes maximum power production 24x7)


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Economics of Hydropower

Cost of HP is affected by oil prices; when oil prices are low, the demand for HP is low.

Thesis was tested in the 1970s when the oil embargo was in place

More plants built, greater demand for HP

Reduces dependency on other countries for conventional fuels

Development, operating, and maintenance costs, and electricity generation

First check if site is developed or not.

If a dam does not exist, several things to consider are: land/land rights, structures and improvements, equipment, reservoirs, dams, waterways, roads, railroads, and bridges.

Development costs include recreation, preserving historical and archeological sites, maintaining water quality, protecting fish and wildlife.

Global Factors

Local Factors


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Hydro costs are highly site specific

Dams are very expensive

Civil works form two-thirds of total cost

– Varies 25 to 80%

Compared with fossil-fuelled plant

– No fuel costs

– Low O&M cost

– Long lifetime

HP has greater cost

– 2 to 7 p/kWh typical range for HP

– 1.5 to 2.5 p/kWh for CCGT

Economics of Hydropower


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Production Expense Comparison


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Capital Costs of Several Hydro Plants

Note that these are for countries where costs are bound to be lower than for fully industrialized countries


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Impacts of Hydroelectric Dams


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Ecological Impacts

Loss of forests, wildlife habitat, species

Degradation of upstream catchment areas due to inundation of reservoir area

Rotting vegetation also emits greenhouse gases

Loss of aquatic biodiversity, fisheries, other downstream services

Cumulative impacts on water quality, natural flooding

Disrupt transfer of energy, sediment, nutrients

Sedimentation reduces reservoir life, erodes turbines Creation of new wetland habitat

Fishing and recreational opportunities provided by new reservoirs


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Environmental and Social Issues

• Land use – inundation and displacement of people

• Impacts on natural hydrology – Increase evaporative losses

– Altering river flows and natural flooding cycles

– Sedimentation/silting

• Impacts on biodiversity – Aquatic ecology, fish, plants, mammals

• Water chemistry changes – Mercury, nitrates, oxygen

– Bacterial and viral infections • Tropics

• Seismic Risks

• Structural dam failure risks


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Benefits…

• Environmental Benefits of Hydro • No operational greenhouse gas emissions • Savings (kg of CO2 per MWh of electricity): – Coal 1000 kg – Oil 800 kg – Gas 400 kg • No SO2 or NOX • Non-environmental benefits – flood control, irrigation, transportation, fisheries and – tourism.


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Disadvantages

The loss of land under the reservoir.

Interference with the transport of sediment by the dam.

Problems associated with the reservoir.

– Climatic and seismic effects.

– Impact on aquatic ecosystems, flora and fauna.

Loss of land A large area is taken up in the form of a reservoir in case of large dams.

This leads to inundation of fertile alluvial rich soil in the flood plains, forests and even

mineral deposits and the potential drowning of archeological sites.

Power per area ratio is evaluated to quantify this impact. Usually ratios lesser than 5 KW per hectare implies that the plant needs more land area than competing renewable resources. However this is only an empirical relation.


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Other problems

Many fishes require flowing water for reproduction and cannot adapt to stagnant resulting in

the reduction in its population.

Heating of the reservoirs may lead to decrease in the dissolved oxygen levels.

The point of confluence of fresh water with salt water is a breeding ground for several aquatic

life forms. The reduction in run-off to the sea results in reduction in their life forms.

Other water-borne diseases like malaria, river-blindness become prevalent.

Methods to alleviate the negative impact

Creation of ecological reserves.

Limiting dam construction to allow substantial free flowing water.

Building sluice gates and passes that help prevent fishes getting trapped.


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Hydropower – Adv. And Disadv.

Positive Negative Emissions-free, with virtually no CO2, NOX, SOX, hydrocarbons, or particulates

Frequently involves impoundment of large amounts of water with loss of habitat due to land inundation

Renewable resource with high conversion efficiency to electricity (80+%)

Variable output – dependent on rainfall and snowfall

Dispatchable with storage capacity Impacts on river flows and aquatic ecology, including fish migration and oxygen depletion

Usable for base load, peaking and pumped storage applications

Social impacts of displacing indigenous people

Scalable from 10 KW to 20,000 MW Health impacts in developing countries

Low operating and maintenance costs High initial capital costs

Long lifetimes Long lead time in construction of large projects


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Hydrologic Cycle


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World Hydropower


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Schematic of Impound Hydropower


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Turbine Application Ranges

lec 12- hydropower

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