renewable energy course#06

Hydel Power

Types of Hydro TurbinesReaction, Impulse, Mixed Flow

Axial for Low Head (3-33 meters)

Radial or Combined Flow

Kaplan – Variable pitch blades – High efficiency at off load conditions

Francis – radial, mixed flow – 5-500 meter heads – poor at off load conditions

Pelton Wheel – Impulse turbine > 50 meter head – high efficiency over wide range

Fixed Bladed Propeller ~ High efficiency at design conditions

Poor at low flow rates

Three Gorges Dam – Yangtze River - ChinaInstalled capacity 22.5 GW - 32 Main Turbines of 700 MW Capacity factor 0.45Height 181 m Length 2,335 m Crest width 40 mBase width 115 mSpillway capacity 16,000 m3/s Reservoir Capacity 39.3 km3

Catchment Area 1,000,000 km2 Surface area 1,045 km2 Normal elevation 175 mReservoir length 600 kmMax. reservoir width 1.1 km

Pelton Wheel – Impulse Turbine

Francis – Reaction Turbine

Kaplan – Reaction Turbine

Principle Po = ρQgH (Watts)

Rain fall > 40 cm/y desired

Ha = Ht - Hf

Q = ⌠ u dA

u ≈ 0.8 us (for rectangular cross section)

Pelton Wheel

F = 2ρQj (uj – uc) Force experienced by the cup

Pj = F uc = 2ρQj (uj – uc) uc Power transferred to one cup

Maximum for uc/ uj = 0.5

Hence Pj = ρ Qj uj2 / 2 100% efficiency

Uj2 = 2g Ha Bernoulli’s Principle

Pm = ηm ρ Qj (2gHa) / 2 = ηm ρ (a uj) (2gHa ) /2

= ηm ρ a (2gHa)3/2 / 2 Power from one nozzle

= ηm ρ a n (2gHa)3/2 / 2 for n nozzles

2 ≤ n ≤ 4

Angular Velocity and Turbine Size

Since uc = Rω R = 0.5 uj / ω

R = 0.5 (2gHa)1/2 / ω

Radius of the nozzle

r2 = Pm / (ηmρnπ(gHa)3/2(2)1/2)

Hence r / R = 0.68 (ηmn) -1/2 δ

Where δ = Pm1/2 ω / [ ρ1/2 (gHa)5/4 ] Shape Number

Peak Efficiencies of Various Turbines w.r.t. Shape Number

Banki Turbine – Cross flow

η = 0.9, δ = 0.11

Hence ω1 = δ ρ1/2 (gHa)5/4 / Pm1/2

= 0.11 x (1000)1/2 (9.8 x 81)5/4 / (160000)1/2

= 36 Rad/s

Further, R = uj / 2ω = (2gHa)1/2 / 2ω = 40 / 2ω = 0.55 m

Similarly, ω2 = 1.1 Rad/s, R = 4.5 m

Therefore, Pelton wheels rotate slowly with low heads – Suitable only with low heads and small flows

World Hydro Electricity Generation (Twh/year)

Hydro Power Capacity by Region

Hydraulic Ramp Pump

Social & Environmental Aspects Multiple applications – Water storage, fishing, recreation, bird sanctuaries, river flow control, flood mitigation

Debt burden – high capital investment, public displacement, destruction of eco-systems, loss of historical and cultural heritage, inequitable sharing of costs and benefits

Small reservoirs and Run-of-River projects considered having less environmental impacts – China having large numbers

S. No

Power Station

Installed Capacity (MW)

1. Tarbela 3,578

2. Ghazi Barotha

1,450

3. Mangla 1,000

4. Warsak 243

5. Chashma 184

6. Khan Khwar

72

7. Duber Khwar

130

8. Allai Khwar

121

9. Others 178

Total Capacity

6,956

Currently Installed Hydel Power Capacity in Pakistan

S. No.

Power Station

Capacity (MW)

Expected Completion

1. Jinnah Hydropower

96 Dec. 2012

2. Gomal Zam Dam

17.4 Feb. 2013

3. Golen-Gol 106 Feb. 2015

4. Neelum Jhelum

969 Oct. 2015

Total 1188.4

Near completion hydel power projects in Pakistan

S. No.

Project River Water Storage (MAF)

Power Capacity (MW)

1. Diamer Basha Indus 8.1 4500

2. Kurram-Tangi Kurram 1.2 84

3. Tarbela-4th Extetnsion

Indus 1410

4. Munda Swat 1.3 740

5. Kohala Jhelum RoR* 1100

6. Bunji Indus RoR* 7100

7. Dasu Indus 1.15 4320

8. Lower Spat Gah Indus RoR* 496

9. Lower Palas Valley

Indus RoR* 665

10. Mahl Jhelum RoR* 600

Total Capacity 11.75 21015

Identified Sites whose Feasibility Study is Complete

Current National News

7 – Wind Projects of 450 MW in the pipeline

50 MW by FFC erected one – 25 out of 33 towers manufactured in Pakistan

Blades will be locally manufactured in the next phase

220 MW of Solar Grid applications in the pipeline @ 25c/kWh

14000 Biogas plants under installation by Dutch Govt.

What Choices Do We Have ?

The shift in the energy sources is viewed as both a challenge and an enormous opportunity

The choice we face is either prosperity or decline

We can either remain an importer of oil at increasingly higher costs or to become an exporter of clean energy

We can allow the climate change to wreck unnatural havoc across the landscape or we can create jobs working to prevent its worst effects

The nations that will lead the world in creating new energy sources will be the nations that lead the 21st century global economy