1. Renewable Energy Part 4 Professor Mohamed A. El-Sharkawi

2. Hydrokinetic Energy

3. Types Small hydroelectric system Barrage System Water stream System
Wave System

4. Types of small hydro systems
Reservoir-Type
Diversion-Type

5. Reservoir-Type Small Hydro System
Generator
Turbine
Reservoir
Penstock
Discharge
Head (H)
H is the physical head

6. Potential Energy in Reservoir
Generator
Turbine
Reservoir
Penstock
Discharge
Head
PEr
Weight of water in reservoir
Water head
For variable head
N:number of hours in one year
Hi: head during ni hours

7. Potential Energy of Water Exiting Penstock
Generator
Turbine
Reservoir
Penstock
Discharge
PEp-out
mass of water leaving
penstock
Effective water head

8. Potential Energy of Water Exiting Penstock
Generator
Turbine
Reservoir
Penstock
Discharge
PEp-out
Water flow in penstock
: water density, 1000kg/m3

9. When water is blocked When water flows Theoretical Head
Generator
Turbine
Reservoir
Penstock
Discharge
PEp-out
When water flows
Pr is the pressure at the end of the penstock in N/m2.
vol is the volume of water passing through the pipe (m3)
When water is blocked

10. Effective Head
Generator
Turbine
Reservoir
Penstock
Discharge
PEp-out

11. Evaluation
The amount of electric power generated by a small hydroelectric system depends on three parameters:
1) Effective head h
2) Water flow rate
3) The efficiency

12. System Efficiency Power at the end of penstock Pp-out Blade Power
Pblade
Input power to Generator Pm
Output electric power Pg
Hydro losses
Turbine losses
Generator losses
Penstock losses
Power at the entrance of penstock
Pp-in

13. Example
A small hydroelectric site has a reservoir with 80 meter effective head. The penstock passes water at the rate of 100 kg/s. The hydro efficiency is 95%, the turbine efficiency is 85% and the efficiency of the generator is 90%. Assume that the owner of this small hydroelectric system sells the generated energy to the local utility at $0.15/kWh. Compute his income in 1 month.

14. Solution

15. Diversion-Type Small Hydro System (Water Stream System)
Generator
Turbine
Discharge

16. Water Stream System

17. Water Stream System

18. Water Stream System
The technology required to convert tidal energy into electricity is very similar to the technology used in either wind energy or hydroelectric power plants
For the same blade size, the tidal mills produce much more power than wind turbines
Water density is times the air density

19. Water Stream System
As is the sweep area of the blades of the turbine in one revolution.
Assuming a water density of 1000 kg/m3

20. Coefficient of Performance

21. Example
A diversion-type small hydroelectric system is installed across a small river with current speed of 5 m/s. The diameter of the swept area of the turbine is 1.2 m. Assume that the coefficient of performance is 50%, the turbine efficiency is 90%, and the efficiency of the generator is 90%. Compute the output power of the plant and the energy generated in one year. If the price of the energy is $0.05/kWh, compute the income from this small hydroelectric plant in one year

22. Solution

23. Barrage System at High Tide
Shore
Dam
Sea Side
Turbine
Water Flow
Lagoon Side

24. Barrage System at Low TideH
Water Flow

25. Barrage

26. Barrage System A is the area of the base of the lagoon
H is the maximum hydraulic heads.

27. Barrage System PE: Potential energy of Barrage System
m: the mass of water moving from the high to low head side
g: the acceleration of gravity
H: the average of the difference in heads between the waters on the two sides of the dam

28. Barrage System: Semidiurnal tide

29. Barrage System: Semidiurnal tide

30. Issues
Dams can slow the flow of water, thus potentially stimulate the growth of the red tide organism.
Tidal energy is expensive method.
Most of the energy is generated when the current is strong around peak or the slack of the tied.

31. Wave Energy

32. Wave Energy
Hinges
Hydraulic Motor
Pistons
Generator
Wave

34. Wave Energy

35. Wave Characteristics Power/m of costal line Period of wave Trough
Height (h)
Wavelength (l)
Crest
Amplitude (a)
Seawater Level
Wave Characteristics
Power/m of costal line
Period of wave

36. Geothermal Energy

39. Cross Section of Earth

40. Earth Temperatures Depth Temperature 40km 100-200 km 5o-20o 500o-600o
Mantle
Depth

42. Heat Pump Pump and Heat Exchangers Hot water Tank Ground
Warm air to house
Hot water Tank
Pump
and Heat Exchangers
Return cool air
Geo-exchanger
Ground

43. G Heat Magma Geothermal Reservoir Steam Turbine Reservoir
Cooling Tower
Mist eliminator
Reservoir
Heat
Magma

44. Hot Dry Rock

45. The first geothermal power plants in the US (The Geysers) in northern California

47. Types of Geothermal Power Plants
Dry Steam Power Plants:
Steam temperature is very high (300oC)
Flash Steam Power Plants:
When the reservoir temperature is above 200oC and below 300oC
the reservoir fluid is drawn into an expansion tank that lowers the pressure of the fluid. This causes some of the fluid to rapidly vaporize (flash) into steam.
Binary-Cycle Power Plants:
At moderate-temperature (below 200oC)
the energy in the reservoir water is extracted by exchanging its heat with another fluid (called binary)
The binary fluid has a much lower boiling point thus it is flashed into steam

48. Geothermal Energy
Geothermal site must have the magma close enough to the surface to heat reservoirs accessible by current drilling technology..
Underground reservoirs are often surrounded by very hard rock; hard to reach
The geothermal fluid can cause water pollution due to the presence of some gases and metals in the reservoirs.
Geothermal fields could also produce carbon dioxide.
Processing the reservoir fluid can produce objectionable odors.

49. Biomass Energy

50. Landfills Housings are being expanded closer to landfills
Landfills and the trucks are considered sight pollution and safety hazards.
Landfills produce unpleasant odors.
Leachate, which is the fluid resulting from water mixed with garbage contaminates underground water.
Ethanol (alcohol) and Methanol can be generated in landfills increasing the fire hazards

51. G Water pipes Stack Furnace Storage Turbine Condenser Steam Filter
Light ash
To landfills
Heavy ash
to landfills

53. Biomass Burning Biomass incineration produce heavy metal and Dioxins
Heavy metal is mixed with ash posing serious pollution to water.
Dioxin is the most dangerous element. It is highly carcinogenic and can cause cancer and genetic defects.