energy systems & climate change thursday 21 jan. 2010 ch.10: wind, water, biomass indirect from...

Energy Systems &Climate Change

Thursday 21 Jan. 2010

Ch.10: Wind, Water, BiomassIndirect from the Sun

Dr. E.J. Zitazita@evergreen.edu

http://academic.evergreen.edu/curricular/energy/0910

Overview

Questions? Announcements? Logistics …

Wind, Water, Biomass (Wolfson Ch.10 & Gore Ch.4, 6)

2:30: Brief Reports: Laura, Crystal, Torie

3:15: Seminar on 1st half of Laboratory Earth (upstairs)

Wind, Water, Biomass

• Hydropower and hydrologic cycle

• Wind power– How the sun drives winds– Coriolus force– Theoretical maxiumum

• Biomass and biofuels

US net energy production

Hydrologic cycle

Hydro systems

212E mv

U=mgh

Hydropower

23% of incoming solar energy goes to evaporating water on Earth

Hydropower is up to 90% efficient, very high energy quality – essentially no thermodynamic limit

Hydropower is nearly fully developed in industrialized nations

Potential for development x 5 worldwide – but it produces more GHG in tropical areas.

+ Clean, quiet, “non-polluting”

+ Pump water up high to store energy

- DISCUSS environmental and human impacts

Power from Niagara falls3. The average flow rate in the Niagara River is 6.0×106 kg/s, and the water drops 50 m over the Falls.If all this energy could be harnessed to generate hydro- electric power at 90 percent efficiency (e), what would be the electric power output?

Solution: Power = e • Energy/time and Energy = mgh:

Wind power

1% of solar energy drives global winds via

Temperature and pressure gradients

Surface directions steered by Coriolus force

Uneven insolation causes…

→ Warmer tropics …

Warmer tropics → lower pressure air

by Sanjay Limaye and Rosalyn Pertzborn, University of Wisconsin (http://www.earthscape.org/t1/lis01/lis01aa.html)

Low pressure → rising air cools →

condensation → precipitation

Hadley cells – atmospheric circulation

Coriolus force – winds deflect over rotating Earth

Total circulation pattern (play ≥)

Power in wind

2 31 12 2

3 31 12 2

2 2 3

3

3132 1

23

1

dE dx dE mv mvPower v

dt dt dx s s

Power Power mv mv

area s s s smass m

densityvolume s

Power mvv

area s

Windpower across the US

Wind Speed and Power

31300 2 1

023

mvPPowerv

area area s

6. By what factor must the wind speed increase in order for the power carried in the wind to double?

Let the initial

What happens to the velocity v if you double the power P? Solve for v/v0:

0

3 31 102 2

2

2

P P

v v

Optimal turbine speed

10. (a) Estimate the total energy produced by a wind turbine with the power curve shown in Fig.10.15 during a day when the wind blows at 2 m/s for six hours, at 10m/s for six hours, at 15 m/s for six hours, and at 25 m/s for six hours.

(b) What’s the turbine’s average power output over this day?

Wind power is rapidly growing

Discuss other considerations regarding windpower…

Energy payback time

• Solar PV: 2 years

• Wind: 2-3 months

Biomass and biofuelsBiomass: wood, waste, plant-derived fuel …

Photosynthesis:

6 H2O + 6 CO2 + energy → glucose + 6 O2

• less than 0.1% efficient, but stores 133 TW solar power in plant growth

• Plants use half of gross: net primary productivity• Humans use 40% of net pp – too much already.

Carbon neutrality requires: • Sustainable production/ harvest• No fossil fuel use (equivalent)

Environmental impacts of biofuels WVO?

Brief Reports

Laura

Crystal

Torie

Ch. 10 HW for next week

Questions 1, 2, 3, 5

Exercises 1, 2, 5, 6, 10, 12, 14

Research Problems: 1, 3

Please do Q and RP with your team, and turn in online in WinterWolfson forum.

Turn in individual hardcopy exercises before class.

Office hours next Wednesday: 3:15 in 3270 Lab II as usual

Break time

See you at 3:15 upstairs

Wolfson Research Problems