EGEE 101 Unit 8: Lesson 20

What is one way around shortage of wind energy electricity generation?

Pumped hydro storage - water in low-lying lakes can be pumped uphill during periods of excess power generation, creating potential mechanical energy. The water can be released through hydro turbines just like a dam to make up the difference.

What does installed capacity refer to?

Refers to the theoretical maximum power output of the turbine. A typical turbine has 2 MW installed, nameplate capacity.

What was wind energy used for in 200 BC?

Simple windmills in China were pumping water.

What was wind energy used for in 1000 AD?

Spread across the European countries -the Dutch refined the windmill and adapted it for draining lakes and marshes in the Rhine River Delta.

If wind produces more electricity than is demanded, the excess goes unused. This is called...

Storage

Which region of the US has the most installed capacity? Major electricity markets?

The Midwest The coasts *Creates a mismatch between where the wind blows and where the electricity is needed.*

What are the role of turbine blades?

To slow the wind down by reducing its kinetic energy.

True or false: Wind is caused by the uneven heating of the earth's atmosphere. Warmer air rises and cooler air moves in.

True.

We don't know when the wind will blow. This consideration is called...

Unpredictability

Is wind energy predictable or unpredictable?

Unpredictable

What was wind energy used for in 900 to 500 BC?

Vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East.

What does intermittent mean?

We can only generate electricity with wind turbines when the wind is blowing.

What would happen if we exploited at all available sites?

We would move wind penetration from 2% to perhaps 20%.

What happens if a utility cannot supply enough electricity to meet a surge in demand?

Whole blocks of the grid lose power

What was the first form of kinetic energy?

Wind energy

What was wind energy used for in 5000 BC?

Wind energy propelled boats along the Nile River.

How many states exceed 10% wind energy as a percentage of in-state electricity generation? 20%? 30%?

10 North Dakota, South Dakota, and Maine have 20% in-state Kansas, Iowa, and Oklahoma have 30% in-state

How much does wind energy account for global electricity generation?

16% of global electricity generated by renewables. In 2016, wind became the largest renewable energy sources in the US by installed capacity at 81 GW, overtaking hydroelectricity at 80 GW installed.

What is the theoretical maximum amount of wind energy that can be extracted?

16/27 of incoming wind energy, or 59.3%. Known as the Betz limit.

How much does wind energy contribute in the US?

24% of renewable energy installation. Comprised 28% of total capacity additions nationwide, and a much higher proportion in some regions of the country.

What is capacity factor?

Because the wind blows at different strengths throughout the week, only a portion of a wind turbine's nameplate capacity is utilized.

What is the Betz limit used for?

Betz's coefficient set the limit on how much energy can be extracted from the wind, utility-scale wind turbines are only ever able to achieve 70%-90% of the theoretical maximum.

How much has wind power installation increased in the last 20 years?

By 7500% - 7.5 GW installed in 1997 and 564 GW in 2018.

What is wind caused by?

By the uneven heating in the earth's surface. Warmer air rises and cooler air moves in, creating wind blowing.

How do modern wind turbines collect energy?

Capture kinetic energy of the wind and extract a portion of it to generate electricity. Each wind turbine acts as a mini-power plant with wind replacing superheated steam.

Which country has the most wind energy consumption? Who is the next?

China - at over 200 GW. US is the next with over 100 GW installed capacity.

How quickly can a coal-fired power plant be ramped up? Natural Gas turbine?

Coal-fired power plant can be ramped up in an hour, while Natural Gas turbines can do so within minutes.

How can we solve 80% of unpredictability problems?

Geographic differences in wind energy The more participants in the energy sharing agreement, the more fluctuations can be smoothed out.

How can compressed air storage be utilized in the subsurface?

Hydrogen gas can be pumped into large salt caverns during periods of wind energy surplus and released during periods of wind energy storage.

What was wind energy used for in the 1800s?

Immigrants from Europe eventually took the wind energy technology to the Western Hemisphere.

The wind doesn't always blow. This consideration is called...

Intermittency

Difference between intermittency and unpredictability?

Intermittency means that the wind is not always blowing, but we know exactly when it will blow (we do not know when it will blow, we just know that it will blow.) It's not that the wind doesn't always blow, but that we don't know exactly when the wind will blow that creates the mismatch between supply and demand.

What is thermal storage used for?

Involves transferring heat to a storage fluid during periods of excess wind power generation and then transferring it to a working fluid during periods of wind power shortages to create steam.

What is the main problem with worldwide wind energy?

It is highly variable in location and intensity.

Why can a wind turbine only extract a portion of the wind's energy?

It would mean if 100% of the kinetic energy could be extracted, the wind velocity would be 0 mph, which would be logically impossibility.

Which energy conversion do you think wind turbines take advantage of?

Kinetic to mechanical to electric

The wind doesn't always blow close to electricity markets. This consideration is called...

Location

What are limitations to wind energy?

Location: There can be a mismatch between where the wind blows and where the electricity demand exists. Intermittency: The wind does not always blow. Unpredictability: We don't know when the wind is going to blow. Storage: Batteries are too small for a 2 MW wind turbine.

What does dispatchable mean?

Meaning a utility company can decide when to turn them on or off.

Do wind turbines operate at their full nameplate capacity?

NO

Can wind power replace coal for US electric generation?

No, exploiting all available sites would move from 2% to perhaps 20%.

How much does excess electricity generation cost during surplus?

$0/kWh