Hydropower n Geothermal

Question 1

What are the three types of hydropower?

Answer 1

• Run of the river
• Storage
• Pumped storage

Question 2

What are the three impulse turbines and describe them?

Answer 2

Pelton
- jet is split symmetrically by blades on the wheel, wheel can have up to 6 jets if mounted on a vertical shaft
- uses double cups

Turgo
- jet passes through wheel from left to right, may have a larger diameter than the jet for a pelton wheel of the same size
- single cups which are more shallow
- can handle higher water flow rates, allowing for efficient operation in lower head ranges
- water exits from the bottom of the wheel and does not interfere with jet inlet (can have therefore have higher rotational speed)

Cross-flow
- has a cylindrical runner and water passes through the blade ring twice, runner may have several segments on the same axis to deliver high efficiency for a wide range of flow rates

Question 3

What are two reaction turbines and describe them?

Answer 3

Francis
- fed by water from a spiral casing with ring of guide vanes immediately upstream of the runner, water exits through gently expanding draft tube

Propeller
- water flow regulated by adjustable guide vanes, vanes move water into the runner to transfer the energy to the blades
- if has adjustable pitch blades then known as Kaplan Turbine
- may also be installed with its shaft vertical

Question 4

What are some of the differences between impulse and reaction turbines?

Answer 4

• All reaction turbines would operate efficiently as pumps
• Reaction turbines are completely submerged and require a pressure casing to operate while impulse operate at atmospheric pressure
• There is a pressure drop across the reaction turbine blades
• Impulse are simpler and easier to control

Question 5

What type of turbine would be used for micro hydro?

Answer 5

Impulse turbine would be more suitable since there would be smaller flow rates and is simpler and easier to control

Question 6

What is the difference between high and low enthalpy sites?

Answer 6

• High enth has higher temperatures (roughly 200 degrees compared to 80-150 degrees)
• High enth used for production of electricity while low enth used for district heating

Question 7

Hot dry rock?

Answer 7

• Requires drilling injection and bore-holes into impermeable rock and then fractures it deep underground
• Cold water is injected and hot water is recovered
• Boreholes need to be 4-6kms deep

Question 8

Heat pump types and issues?

Answer 8

GSHP - ground source
WSHP - water source
ASHP - air source
Issues:
- increased strain on electricity network
- poor performance if incorrectly installed
- poor performance of ASHP in low temps and humid conditions