Objectives

• Responding to TDRs

• Evaluating renewable source of energy

• Designing for renewables

• Field Trip 5/2 City Hall – meet in entranceway at 12:45 pm

TDR responses

• Read them through once• Put them aside• No point getting defensive about them• Use them to inform your presentation and prepare

your final draft• Do not worry too much about grades

• Peer evaluations count for a relatively small part of your draft grade

• Even my evaluation only counts for 10% of final project grade

Responding to TDRs

• You do not need to provide a response to small changes in the text

• You do need to respond to every numbered comment (and all other major comments) stating:• Either how you addressed the concern• Or why you don’t need to address the concern

• The reviewer is always “right”

TDR response example

• Figure 4 is not integrated into the text of the paper. A further description and definition of key terms in the figure would make the paper stronger.

• A longer caption explaining the figure has been added as has an additional sentence in the body of the paper elaborating the conclusions from this figure.

TDR responses

• 1 per reviewer (including me)

• Due 5/4 when final reports are due.

• TDR responses are worth 5% of project grade

• Final report is worth 30% of project grade

Defining renewables

• Difference from earlier discussions• Discussing global, rather than just US

• Solar• Wind• Biomass• Tidal• Geothermal• Small hydro

Solar

• Solar thermal

Solar PV

Analysis of solar potential

• 1350 W/m2 from the sun (annual average)

• 300 – 400 W/m2 on the surface of the Earth

• Efficiency to conversion to electricity 1 – 10%• Transmission losses• Inversion losses• Storage losses

• Efficiency for thermal systems 20 - 35 %• Pump losses, standby losses

Wind turbines

Analysis of wind potential

• E = ½ m v2

• W = ½ Q ρ v2 v3

• Wind speed is most important parameter• Area of blades also a factor

• Losses• Regulating speed/inversion• Variable direction/speed

• Efficiency not as meaningful as output

Biomass

• Combustion (not generally considered renewable)

• Digestion to produce methane for burning

Tidal power

Geothermal power

Why small hydro and not big hydro?

• Much smaller effect on streams/rivers

• No damming required• Silting• Sedimentation• Dam failure

Potential (with current technology)Resource Potential

(TWh/year)

Output

(TWh/year)

Wind 20-40K 50

Solar 12-40K 1.2

Geothermal 4-40K 44

Biomass 8-25K 185

Wave/Tidal 2-7.5K ~0

Small Hydro ? 15

Reference: Gross et al. (2003) Environment International

State of the art

• Currently ~356 TWh/year with renewables

• ~15,000 TWh/year of electricity generation

• Not reaching our full potential

• Reasons?

Costs of renewable electricity

• What are average costs for nuclear, coal, gas electricity?

Fuel Cost US¢/kWh

Solar 30

Wave 9

Biomass 6

Wind 5

Successes

• Wind• Since 1990 annual energy output/turbine has

increased two orders of magnitude• Maximum capacity has increased by factor of 20

(up to ~1 MW)• Weight/capacity has decreased by factor of ~2• Sound levels have decreased by factor of ~2• Installed capacity has increased order of magnitude

Reference: Gross et al. (2003) Environment International

Future for wind

• Offshore installations

• Why is this desirable?

Solar PV

• Capacity has increased by factor of ~5 since 1990

• Price/peak watt has decreased over an order of magnitude over the last 25 years

• Efficiency has increased by a factor ~2 over 25 years

What are the downsides of renewables

• Intermittency• Strain on grid

• Local problem

• Peak power issues• Energy storage

• Additional transmission for offshore capabilties

What is the situation in the US?

• “Renewable energy consumption for 2001 dropped to its lowest level in over 12 years, accounting for just 6 percent of total U.S. energy consumption.” http://www.eia.doe.gov/cneaf/solar.renewables/page/rea_data/chapter1.html

• Why?

• What is included?

More about renewables in the US

• Usage by fuel and sector (1997-2001)• http://www.eia.doe.gov/cneaf/solar.renewables/pag

e/rea_data/table2.html

• Solar shipments• http://www.eia.doe.gov/cneaf/solar.renewables/pag

e/rea_data/table10.html

• Renewable consumption by state• http://www.eia.doe.gov/cneaf/solar.renewables/pag

e/rea_data/appendixc.html

Central question is one of cost and political will

• Populations are often willing to pay for renewable power

• Captures imagination more than energy conservation

• Detractors include• Entrenched energy interests• Operation and maintenance experts• Economists

Designing for Renewables

• Match renewable to load

• Educate clients• Make conservation more exciting

• Plan for energy storage