Hydropower

Question 1

What are the main characteristics of HP?

Answer 1

• Renewable
• Sustainable
• Flexible (storage and fast response)
• Economic

Question 2

How long have dams existed for?

Answer 2

5000 years

Question 3

What allowed HP to become a key component of the energy grid?

Answer 3

Industrial revolution 100 years ago

Question 4

What allowed electricity to be deployed along long distances?

Answer 4

Alternating current

Question 5

When was there major dam development?

Answer 5

1960s-1980s

Question 6

How many large dams are there in the world?

Answer 6

60,000

Question 7

How many of the 60,000 large dams are in China?

Answer 7

Half

Question 8

What is the role of hydropower in the share of renewable energy capacity?

Answer 8

Hydropower is a major player within the top 3 sources of renewable energy capacity, known for being dispatchable but experiencing declining growth

Question 9

When it comes to renewable energy generation, how does hydropower compare in productivity?

Answer 9

Hydropower is more productive compared to other forms of renewable energy generation

Question 10

Historically, why has hydropower been able to compete with fossil fuels?

Answer 10

Hydropower has traditionally been the only top renewable energy source able to compete in price and scale with fossil fuels due to its low cost

Question 11

What factors have made hydropower more expensive in recent times?

Answer 11

Hydropower has become more expensive because most of the most productive projects have already been built, leaving less profitable sites, facing small sites, and more environmental regulations

Question 12

What is hydropower’s role in energy storage as of 2017?

Answer 12

Hydropower was dominating the share of energy storage in 2017

Question 13

What is the status of hydropower in the UK?

Answer 13

Hydropower in the UK is marginal, contributing to 1.7% of electricity generated, largely due to the requirement of specific conditions such as topography and gradient

Question 14

What are features of a run-of-the-river dam?

Answer 14

• Weir
• Spillway
• Settling tank
• inlet canal

Question 15

How can power be calculated?

Answer 15

P=𝜂𝛾QH

Question 16

How does run-of-the-river hydro projects work?

Answer 16

Use the natural downward flow of rivers and microturbine generators to capture the kinetic energy carried by water

Question 17

What are the characteristics of an impoundment hydropower system like the Aldeadávila Dam?

Answer 17

Impoundment systems stir water, have significant storage, and allow control over both the flow rate (Q) and the head (H)

Question 18

How does the volume of water elevation (V) relate to the height of a dam (H)?

Answer 18

The volume of water elevation is proportional to a certain power of the height of the dam (V ~ H^a)

Question 19

What is the purpose of pump-storage in hydropower?

Answer 19

Pump-storage systems use excess electricity production to pump water to a high elevation for later use, especially when electricity is needed

Question 20

What is the efficiency of the turbine section in a pump-storage system?

Answer 20

90%

Question 21

What are the drawbacks of hydropower regarding land use?

Answer 21

Hydropower requires a lot of land, which means obtaining permits can be a complex process

Question 22

What is the energy production capacity of hydrokinetic turbines and where are they well suited?

Answer 22

Hydrokinetic turbines have low energy production but are well suited for small, isolated communities with low environmental impact, such as those in the Amazon

Question 23

How does hydropower production affect the climate?

Answer 23

Through evaporation, which is proportional to the surface area of the water

Question 24

Hydropower

What is energy generation affected by?

Answer 24

• Highly seasonal, for instance: subject to snow/glaciers or dry periods.
• Droughts (annual and interannual).
• Floods

Question 25

What competing interests must be balanced with hydropower during droughts?

Answer 25

During droughts, the competing interests include environmental flows, water supply, flood storage, and irrigation

Question 26

How are dams designed in terms of flood protection?

Answer 26

Dams are designed to survive floods that happen, on average terms, once every 1,000 years

Question 27

How can past floods be used in relation to hydropower dams?

Answer 27

By examining floods in the past 30 years and their respective discharges, one can estimate the potential for future floods

Question 28

What are the stages of the dam life-cycle?

Answer 28

1. Planning: 3-30 years 2. Design: 1-2 years 3. Construction: 2-10 years 4. Operation → monitoring & maintenance → Refurbishment, uprating or decommissioning : +50-150 years

Question 29

List the multi-purpose functions of dams.

Answer 29

Dams serve purposes such as irrigation, hydroelectric power generation, water supply, recreation/river regulation/navigation, and flood control

Question 30

What are the two main types of dams according to the material, and what is their prevalence?

Answer 30

There are embankment dams (80%), which use materials available on-site, and concrete dams (20%), which need materials to be transported

Question 31

What are the components of dam infrastructure?

Answer 31

- water management - flood safety - hydropower generation - environmental impact reduction facilities

Question 32

Identify the key parts of a hydropower dam.

Answer 32

The key parts include the reservoir, control gate, penstock, powerhouse, spillway, and fish ladder

Question 33

What principle is energy extraction based on in a hydropower dam?

Answer 33

Energy extraction is based on the net head and the conversion of mechanical energy into electrical energy, taking into account losses of energy

Question 34

What is the function of the penstock as indicated in the diagram?

Answer 34

The penstock is a pipe that carries water from the reservoir to the turbines in the powerhouse

Question 35

What are the three main types of hydropower turbines?

Answer 35

Francis turbines for heads over 10 meters, Pelton turbines good for high heads, and Kaplan turbines good for low heads

Question 36

What does the term "per cent of full load" mean for turbines?

Answer 36

"Per cent of full load" refers to the operating capacity of a turbine compared to its maximum potential capacity

Question 37

According to the graph, which turbine shows the highest efficiency at full load?

Answer 37

The Kaplan turbine shows the highest efficiency at full load

Question 38

What are the common impacts of hydropower systems?

Answer 38

- Everyday water losses due to evaporation and infiltration - Alteration of the hydrological regime downstream - Hydropeaking/residual flow impacts - Sediment and nutrient disruptions

Question 39

How does the lack of sediments downstream affect the environment and infrastructure?

Answer 39

- lead to the scouring of bridges - lead to nutrient depletion in water - lead to loss of dam storage capacity - lead to loss of sediment discontinuity

Question 40

What is the impact of a lack of dissolved oxygen (DO) in water bodies?

Answer 40

A lack of dissolved oxygen can negatively affect aquatic organisms and water quality

Question 41

Why can excess of gases be a problem in hydropower systems?

Answer 41

Excess gases, particularly total dissolved gas (TDG), can become supersaturated under high pressures and lead to fish mortality

Question 42

What greenhouse gases are emitted by hydropower dams during construction and operation?

Answer 42

CO2 is emitted during construction due to cement use and transport, while CH4 is emitted during operation, which can be mitigated by reducing organic material in the reservoir

Question 43

What is the frequency of dam collapses mentioned?

Answer 43

It is mentioned that on average, 3 dams collapse per year

Question 44

What design principle is recommended to mitigate the hazards associated with dam failures?

Answer 44

Dams should be designed with a low probability of failure, as it is noted that 0.1% of dams fail