PUMPED STORAGE PLANTSeminar

ByNilanjana Sen.

4th Year.B.Power Engg.

Roll - 27

INTRODUCTION Pumped Storage Power Plants are a special type of power- plants, which work as conventional hydropower stations for part of the time.

When the plants are not producing power, they can be used as pumping stations which pump water from tail race side to the high level reservoir.

The working of the power station can be distinguished as the generating phase when the turbines and generators are electrical power and the pumping phase when the pump and motors are in operation.

HOW PUMPED STORAGE WORKS

When there's a sudden demand for power, the "head gates" are opened, and water rushes down the tunnels to drive the turbines, which drive the powerful generators. The water then collects in the bottom reservoir, ready to be pumped back up later.

Water is pumped up to the top reservoir at night, when demand for power across the country is low.

Reversible turbine/generator assemblies act as pump and turbine (usually a Francis turbine design).

Figure:1 Hypothetical Load Curve

LOAD CURVE FOR PUMPED STORAGE PLANT

Figure: 2 Actual Load Curve

HISTORICAL DEVELOPMENT

The history of pumped storage plant can be traced as far back as 1882, in which year the 1st hydroelectric plant making use of pumped storage started functioning at Zurich in Switzerland.

In 1931, the 1st reversible pump-turbine was installed at Baldeneyesee in Germany.

The 1st major reversible diagonal turbine (Deriaz) was installed at Niagara in 1955.

In Europe, in 1962, Ffestiniog (Great Britain) with a total capacity of 360 MW and Provindenza (Italy) with a head of 284 m, were the major landmarks in the progress of pumped storage plants.

CLASSIFICATION

Both the reservoirs on a single river, in a tandem chain manner.

Two reservoirs on two separate rivers close to each other and flowing at different elevations.

Higher reservoir an artificially constructed pool with the help of dykes all around, on a high level plateau or on a leveled hill-top and the lower reservoir on a natural river.

The lower reservoir is a natural lake while the higher reservoir reservoir is artificial.

DAILY – daily cycle of pumping & generation

WEEKLY – weekly cycle where pumping is confined to slack weekend periods.

SEASONAL – pumping done during lean demand & generation during higher demand.

PURE – Closed cycle plant - - Volume of water flowing to the lower reservoir = The water pumped to the higher reservoir in 1 cycle of operation.

MIXED – Total generation in 1 cycle > Total pumping during that period.

HIGH HEAD MEDIUM HEAD

LOW HEAD – not common.

FRANCIS TURBINE – very common because of its high efficiency and high speed.

PELTON TURBINE

KAPLAN TURBINE

HORIZANTAL – pump situated at left end & turbine at right end; generator/motor in between -- generally preferred due to good visibility, favorable conditions of erections & dismantling for repairs & check-up.

VERTICAL – pump situated at lowest & generator/motor unit at top; turbine in intermediate position – more compact.

FOUR UNIT INSTALLATION – four different units viz. pump, motor, generator and turbine; pump & motor coupled together were independent of turbine & generator coupled together.

THREE UNIT INSTALLATION – three units viz. pump, turbine and generator which can function as a motor; pump & turbine were coupled directly to generator/motor unit.

TWO UNIT INSTALLATION – two units viz. generator which can operate as a motor coupled to a turbine which also operates as a pump.

ADVANTAGES Relatively low capital cost; thus economic source of peaking capacity.

Rugged & dependable; can pick up load rapidly in a matter of few minutes.

Readily adaptable to automation as well as remote-control.

Hydel power is free from effects of environmental pollution—thus contributing a part in curbing air & water pollution.

ADVANTAGES (contd..)Allow great deal of flexibility in operational schedules of system.

Power required for pumping is available at a cheaper rate(slack hours’ rate); power produced can be sold at prime rate(peak hours’ rate) - this compensates the low hydraulic efficiency.

They allow entire thermal or nuclear power generation to take up base load; thus load factor improves giving overall greater system efficiency.

Little effect on the landscape.

PROBLEMS OF OPERATION

Once it's used, it can't be used again until the water is pumped back up.

Cavitation problems; powerhouse location has to be so fixed that pump operates under submerged conditions(magnitude depends on specific speed & net head).

Reversing of direction of flow gives rise to runner cracking due to fatigue.

Trash racks vibrate violently during pumping operation.

Flow during pumping mode tends to lift the machine axially causing tensile stresses in bearings; specially guide vanes.

TOPOGRAPHYFor an economic operation, an important criterion is the ratio of the length, L, between the two pools along the water passage to the head difference, h, between them, i.e

Lh

The less the value of L / h , more economic is the prospect of the plant. Some typical ratios :

Vianden 2.9Ludington 4.0Horn berg 4.3

EFFICIENCY OF PUMPED STORAGE PLANTS

ηo =

Now if Q is the discharge and H the gross head,

Then, Eg = ω Q (H - hf ) * 0.736 * ηt75

And Ep = ω Q (H + hf ) * 0.736 75 ηp

Then ηo = Ep

Eg = (H – hf ) * ηt * ηp

( H + hf )

If hf = kH, then ηo = ( 1 – k ) ( 1 + k ) * ηt * ηp

ηt = Overall efficiency of generation ;0.88

ηp = Overall efficiency of pumping operation ;0.85

ω = speed

hf = frictional head loss

k = constant ; 0.02 – 0.03

Overall efficiency comes out to be 72 %

SOME FACTS In 2000 the United States had 19.5 GW of pumped storage capacity, accounting for 2.5% of base load generating capacity. PHS generated (net) - 5.5 GWh of energy because more energy is consumed in pumping than is generated; losses occur due to water evaporation, electric turbine/pump efficiency, and friction. In 1999 the EU had 32 GW capacity of pumped storage out of a total of 188 GW of hydropower and representing 5.5% of total electrical capacity in the EU.

PROJECT EXAMPLES

174 MW, reversible Deriaz turbines, Niagara Falls (1957).

Sir Adam Beck Hydroelectric Power Stations

Ludington The 1872 MW plant houses six vertical Francis-type pump-

generating units which are recognized as some of the largest in the world from the perspectives of physical size and unit rating.

Ffestiniog Pumped Storage Plant The lower power

station has 4 water turbines which generate 360 MW of electricity within 60 seconds of the need arising

Some Pumped Storage Plants

Around The World

Australia Bendeela (1977), 80 MW

Kangaroo Valley (1977), 160 MW

France Grand Maison (1997), 1070 MW

Montézic (1983), 920 MW

Super Bissorte (1978), 720 MW

United States

Castaic Dam (1978), 1566 MW

Bear Swamp (1972), 600 MW

Blenheim-Gilboa (1973), 1200 MW

India Bhira, Maharashtra, 150 MW

Kadamparai, Coimbatore, Tamil Nadu, 400 MW (4 x 100 MW)

Nagarjuna Sagar PH, Andhra Pradesh, 810 MW (1 x 110 MW + 7 x 100 MW)

Purulia Pumped Storage Project, Ayodhya Hills, Purulia, West Bengal, 900 MW

Srisailam Left Bank PH, Andhra Pradesh, 900 MW (6 x 150 MW)

Tehri Dam, Uttranchal (under construction), 1000 MW

THANK YOU!!!