BASIC ELECTRICAL ENGINEERING

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Lecture slides by

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MR. A BHUYAN

ASST. PROFESSOR

GIET, BBSR

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Hydro Power

How Hydropower Works!

• Hydrologic cycle

How Hydropower Works! (ctd…)

• 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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POTENTIAL

Potential

• THEORETICAL- The maximum potential that exists.
• TECHNICAL- It takes into account the cost involved in exploiting a source (including the environmental and engineering restrictions)
• ECONOMIC- Calculated after detailed environmental, geological, and other economic constraints.

Continent Wide distribution

Top ten countries (in terms of capacity)

UNDP estimates

• Theoretical potential is about 40,500 TWh per year.
• The technical potential is about 14,300 TWh per year.
• The economic potential is about 8100 TWh per year.
• The world installed hydro capacity currently stands at 694 GW.
• In the 1980s the percentage of contribution by hydroelectric power was about 8 to 9%.
• The total power generation in 2000 was 2675 Billion KWh or close to 20% of the total energy generation.

Continued…

• Most of the undeveloped potential lies in the erstwhile USSR and the developing countries.
• Worldwide about 125 GW of power is under construction.
• The largest project under construction is the Three Gorges at the Yangtze river in China. Proposed potential is 18.2 GW and the proposed power output is 85 TWh per year.

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Global Installed Capacity

Under Construction…

The Indian Scenario

• The potential is about 84000 MW at 60% load factor spread across six major basins in the country.
• Pumped storage sites have been found recently which leads to a further addition of a maximum of 94000 MW.
• Annual yield is assessed to be about 420 billion units per year though with seasonal energy the value crosses600 billion mark.
• The possible installed capacity is around 150000 MW (Based on the report submitted by CEA to the Ministry of Power)

Continued …

• The proportion of hydro power increased from 35% from the first five year plan to 46% in the third five year plan but has since then decreased continuously to 25% in 2001.
• The theoretical potential of small hydro power is 10071 MW.
• Currently about 17% of the potential is being harnessed
• About 6.3% is still under construction.

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India’s Basin wise potential

Region wise status of hydro development

Major Hydropower generating units

Installed Capacity

Region wise contribution of Hydropower

Annual gross generation (GWh)

Potential of Small Hydropower

• Total estimated potential of 180000 MW.
• Total potential developed in the late 1990s was about 47000 MW with China contributing as much as one-third total potentials.
• 570 TWh per year from plants less than 2 MW capacity.
• The technical potential of micro, mini and small hydro in India is placed at 6800 MW.

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Small Hydro in India

Sites (up to 3 MW) identified by UNDP

Small Hydro in other countries

• China has 43000 small hydro-electric power stations nationwide to produce 23 million KWh a year. It has 100 million kilowatts of explorable small hydro-electric power resources in mountainous areas of which only 29% has been tapped.
• Philippines has a total identified mini-hydropower resource potential is about 1132.476 megawatts (MW) of which only 7.2% has been utilized.
• There is about 3000 MW of small hydro capacity in operation in the USA. A further 40 MW is planned.

TECHNOLOGY

Technology

Impoundment facility

Dam Types

• Arch
• Gravity
• Buttress
• Embankment or Earth

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Arch Dams

• Arch shape gives strength
• Less material (cheaper)
• Narrow sites
• Need strong abutments

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Concrete Gravity Dams

• Weight holds dam in place
• Lots of concrete (expensive)

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Buttress Dams

• Face is held up by a series of supports
• Flat or curved face

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Embankment Dams

• Earth or rock
• Weight resists flow of water

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Dams Construction

Diversion Facility

• Doesn’t require dam
• Facility channels portion of river through canal or penstock

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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.

Pumped Storage

• Operation : Two pools of Water
• Upper pool – impoundment
• Lower pool – natural lake, river or storage reservoir
• Advantages :
• Production of peak power
• Can be built anywhere with reliable supply of water

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The Raccoon Mountain project

Sizes of Hydropower Plants

• 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

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Large Scale Hydropower plant

Small Scale Hydropower Plant

Micro Hydropower Plant

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

Generating Technologies

• Types of Hydro Turbines:
• Impulse turbines
• Pelton Wheel
• Cross Flow Turbines
• Reaction turbines
• Propeller Turbines : Bulb turbine, Straflo, Tube Turbine,

Kaplan Turbine

• Francis Turbines
• Kinetic 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

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 (continued…)

• 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

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Cross Flow Turbines (continued…)

• 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

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.

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Francis Turbines (continued…)

• 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.

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.

Hydroelectric Power Plants in India

Baspa II Binwa

Continued …

Gaj

Nathpa Jakri

Continued…

Rangit

Sardar Sarovar

ENVIRONMENTAL IMPACT

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.

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• 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.

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• 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.

• Disappropriating and resettlement represents a mammoth political and management challenge. Related costs can increase project costs by as much as 10% if planned poorly.

Interference with Sediment transport

• Rivers carry a lot of sediments.
• Creation of a dam results in the deposition of sediments on the bottom of the reservoir.
• Land erosion on the edges of the reservoir due to deforestation also leads to deposition of sediments.

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Effects

• Capture of sediment decreases the fertility downstream as a long term effect.
• It also leads to deprivation of sand to beaches in coastal areas.
• If the water is diverted out of the basin, there might be salt water intrusion into the inland from the ocean, as the previous balance between this salt water and upstream fresh water in altered.
• It may lead to changes in the ecology of the estuary area and lead to decrease in agricultural productivity.

Climatic and Seismic effects

• It is believed that large reservoirs induce have the potential to induce earthquakes.

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• In tropics, existence of man-made lakes decreases the convective activity and reduces cloud cover. In temperate regions, fog forms over the lake and along the shores when the temperature falls to zero and thus increases humidity in the nearby area.

Some major/minor induced earthquakes

Eutrophication

• In tropical regions due to decomposition of the vegetation, there is increased demand for biological oxygen in the reservoir.
• The relatively constant temperatures inhibit the thermally induced mixing that occurs in temperate latitudes.
• In this anaerobic layer, there is formation of methane which is a potential green house gas.
• This water, when released kills the fishes downstream and creates an unattractive odor. The only advantage is that all these activities are not permanent.

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.

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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.

Case Study- Volta Lake, Ghana

• Volta lake was formed as a result of the construction of the Akosombo Dam.
• It was aimed at providing much needed power needs for domestic consumption and for the production of Aluminium.
• Even though much study was conducted prior to the construction, many favorable and adverse environmental changes took place.

Favorable impact

• Enhanced fishing upstream.
• Opportunities for irrigated farming downstream.
• With the flooding of the forest habitat of the Tsetse fly, the vector of this disease, the problem of Sleeping Sickness has been substantially reduced.

Negative Impact

• Diminished fishing downstream.
• Growth of long lasting weeds like Pistia, Vossia spp. Ceratophyllum.
• Ceratophyllum’s submerged beds house large populations of Bulinus snails the vector of Schistosomiasis.
• Growth of dangerous water weeds like water hyacinth.
• Prevalence of river blindness (Snchocerchiasis), bilharzia (Schistosomiasis), malaria and Sleeping Sickness (Trypanosomiasis

Technological advancements

• Technology to mitigate the negative environmental impact.
• Construction of fish ways for the passage of fish through, over, or around the project works of a hydro power project, such as fish ladders, fish locks, fish lifts and elevators, and similar physical contrivances
• Building of screens, barriers, and similar devices that operate to guide fish to a fish way

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Continued…

• Evaluating a new generation of large turbines
• Capable of balancing environmental, technical, operational, and cost considerations
• Developing and demonstrating new tools
• to generate more electricity with less water and greater environmental benefits
• tools to improve how available water is used within hydropower units, plants, and river systems
• Studying the benefits, costs, and overall effectiveness of environmental mitigation practices

ECONOMICS OF HYDRO POWER

Global HP Economics

• 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

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Local HP Economics

• Development, operating, and maintenance costs, and electricity generation

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• First check if site is developed or not.

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• 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.

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

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Construction Costs

• Hydro costs are highly site specific
• Dams are very expensive
• Civil works form two-thirds of total cost

– Varies 25 to 80%

• Large Western schemes: $ 1200/kW
• Developing nations: $ 800 to $ 2000/kW
• Compare with CCGT: $ 600 to $800/kW

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Production Costs

• Compared with fossil-fuelled plant

– No fuel costs

– Low O&M cost

– Long lifetime

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Cost and Revenue of HP

Comparison with CCGT

Parameters

• Payback-HP has higher payback time(25 years)
• Net present value (NPV)
• Unit cost
• Discounting

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Payback

Effect of discounting payback

Effect of discounting payback: CCGT

Discounting and NPV

• Effect of discounting

– Hydro’s high capital cost at near full value

– Its additional revenue far in future less

valuable

– CCGT has higher NPV

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Unit cost

• Unit cost

– Cost per kWh produced

– Discount costs and production

• HP has greater cost

– 2 to 7 p/kWh typical range for HP

– 1.5 to 2.5 p/kWh for CCGT

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Conclusion

• Overall CCGT appears to be the better investment
• Environmental or operational benefits not considered
• Overall HP is still a better investment for future

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Small HP costs

• Machinery-includes turbine, gearbox or drive belts, generator, water inlet control valve.
• Civil Works-includes intake and screen to collect the water, the pipeline or channel, turbine house and machinery foundations, and the channel to return the water back to the river-site specific��

Small HP costs

• Electrical Works-control panel and control system, wiring.
• External Costs-includes the services of someone to design the installation, costs of obtaining a water license, planning costs and cost of connection to the electricity network

-these two depend on maximum power output�

Typical costs of 100KW plant

Sardar Sarovar Dam

• Project planning started as early as 1946.
• Project still under construction with a part of the dam in operation.
• A concrete gravity dam, 1210 meters (3970 feet) in length and with a maximum height of 163 meters

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• The gross storage capacity of the reservoir is 0.95 M. ha.m. (7.7 MAF) while live storage capacity is 0.58 M.ha.m. (4.75 MAF).
• The total project cost was estimated at Rs. 49 billion at 1987 price levels.
• There are two power houses project- 1200 MW River Bed Power House and 250 MW Canal Head Power House. Power benefits are shared among Madhya Pradesh, Maharashtra and Gujarat in the ratio of 57:27:16 respectively.

Environmental Protection measures

• About 14000 ha of land has been afforested to compensate for the submergence of 4523 ha of land.

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• Formation of co-operatives, extensive training to the fisherman, providing infrastructure such as fish landing sites, cold storage and transportation etc.

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• Surveillance & Control of Water related diseases and communicable diseases.
• Extension of Shoolpaneshwar sanctuary to cover an area of 607 sq.km.

Rehabilitation & Resettlement

• Individual benefits like grant of minimum 2 ha. of land for agricultural purpose of the size equal to the area of land acquired.

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• Civil and other amenities such as approach road, internal roads, primary school building, health, centre, Panchayat ghar, Seeds store, Children's park, Village pond, Drinking water wells, platform for community meetings, Street light electrification, Religious place, Crematorium ground etc. are provided at resettled site.�  

The Three Gorges Project

• Being built on the Yangtze river.
• Still under construction to supply energy and provide inland transportation.
• Project expected to complete in 2009.

Some Facts….

• Dam to provide 18.2 GW of power using 26 Francis generators of 700 MW each.
• 630 Km long and 1.3 Km wide capable of allowing 10,000-ton ocean-going freighters to sail directly into the nation's interior for six months of each year.
• More than 2 million people are to be resettled.
• The amount of concrete totals 26.43 million cubic meters, twice that of the Itaipu project in Brazil, currently the world's largest hydroelectric dam.

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Environmental and Other Concerns

• There have been little to no attempts made toward removing accumulations of toxic materials and other potential pollutants from industrial sites that will be inundated. They number more than 1600 in all.

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• The dam will disrupt heavy silt flows in the river. It could cause rapid silt build-up in the reservoir, creating an imbalance upstream, and depriving agricultural land and fish downstream of essential nutrients. However, sufficient studies have not been conducted.

• Potential Hazard also exists. For example, In an annual report [1] to the United States Congress, the Department of Defense cited that Taiwanese "proponents of strikes against the mainland apparently hope that merely presenting credible threats to China's urban population or high-value targets, such as the Three Gorges Dam, will deter Chinese military coercion."

• Independent reports suggest residents are convinced their compensation is miserly even though China claims its plans will improve the life of those affected.

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• Archaeologists and historians have estimated nearly 1,300 important sites will disappear under the reservoir's waters including remnants of the homeland of the Ba civilization.

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