Lecture 11 Conservation

Fall 2011

Assignments

Energy Audit 2Prepare a summary report of the energy usage of your building extracted from the ITRON web site. This should include data from different periods of the year to cover times with heating and air conditioning, and varying building occupancy; an analysis of daytime vs. night time usage (which may be very useful in helping to identify energy savings), and weekday vs. weekend. Length: ~two pages of text plus figures. Upload to ELMS. Due Date: Tonight

New Reading Assigment - Chapter 5 Wolfson

EXAM – Likely November 1

What year was the PC (IBM Personal Computer) Introduced

1. 19702. 19753. 19804. 19825. 19846. 19867. 1990

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Steve Jobs

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http://www.youtube.com/watch?v=OYecfV3ubP8

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Production vs. Conservation

ANWR

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Production vs. Conservation

ANWR - total reserves estimated at 5-10 billion barrels of oil

US annual oil consumption: 7 billion barrels per year

- If we increase mileage from 27(current) to 30 mpg, this saves an ANWR every 6-12 yrs…

What could go wrong?

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http://www.mckinsey.com/clientservice/electricpowernaturalgas/downloads/US_energy_efficiency_full_report.pdf

The width of each column represents the amount of efficiency potential (in trillions of BTUs), while the height represents to annualized cost in dollars per million BTUs

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McKinsey Study:

By 2020:

• invest $520 Billion

• save $1200 Billion

• reduce US energy by 9 quads

Energy Conservation vs. Conservation of Energy First Law of Thermodynamics- Energy is conserved

Energy Conservation- Reduce usage of energy- More efficient production- More efficient distribution- More efficient products- Changing our usage patterns- Personal choices

“The cleanest power plant is the one never built.”

Global Energy Usage - Selected Countries Australia 5700 Bangladesh 161 Brazil 1067 China 1138 France 4518 Germany 4203 Ghana 400 India 512 Japan 4040 Kenya 481 Mexico 1533 Russia 4423 South Africa 2596 US 7794

2003 Energy per capita in kg oil equivalent

Why are we such energy hogs?

1. The US is a large country2. Our standard of living is

much higher3. Oil companies have too

much political influence4. We don’t care about

conservation5. We are not hogs - the rest

of the world is just catching up.

Energy Star rated appliances

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Energy Star

- Joint program of EPA and DoE- Started in 1992- certifies products as energy efficient- now expanded to buildings- > 95% of computer monitors are ES rated- 20% heating systems- 20% washers/dryers

- Program has saved ~5% of total US electricity demand in 2006

Energy Saved

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Standby power

1 W on for a year is ~3.15x107 W sec- ~3.15x107 W sec / 3600 sec/hr = 8750Wh = 8.750kWh- At $0.15/kWh -> $1.31 per year/kWh

http://standby.lbl.gov/summary-chart.html

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Lighting - Incandescent vs. Compact Fluorescent

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Incandescent Spectrum

Compact Fluorescent Spectrum

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Incandescent Spectrum

HalogenSpectrum

Lighting

Light output measured in lumens- Amount of visible light per solid angle- Lights with equal lumens have equal brightness

Maximum possible efficiency = 684 lm/W(all energy converted to visible light)

Incandescent bulb : ~ 1700 lm for 100 W Compact Fluorescent Lights (CFL) ~1700 lm for 23W- Sold as 100 W equivalent , i.e. same lumen output as 100

W incandescent bulb- Typically 4X more efficient!

Say goodbye to incandescent bulbs…

Do they save me money?

100 W CFL ~ $3.00 100 W Incandescent ~ $0.75

Calculate payback time

- Assume I use light ~ 3 hrs. per day- In one year incandescent consumes 3h X 0.1 kW X 365 = 110

kWh- I pay $ 0.15 /kWh to PEPCO- My cost per year = $16.50- The CFL only uses 24 W, so cost is (24/100) $16.50 = $3.96- I save a difference of $12.50/year- I invested $2.25, so it pays back in 2.25/12.5 = .18 years = 2

months!!

Should I replace a working incandescent bulb?

What happens to the heat incandescent bulbs produce?

In the summer they add to your air-conditioning bill - it takes ~3 times less energy to remove the heat – - still that adds 30%

In the winter – it adds heat so your electric bill is reduced- normal heating costs about half as much as electric

resistance heat so you save about 50% in the winter

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A bathroom decision

My wife wanted to renovate our bathroom

The designer said “what about a heated floor?

I wanted to know what it was going to cost to operate

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How much was a heated floor going to cost to use?

The floor heater uses 400W (when on)- Using the calculation from above:- At $0.15/kWh -> $1.31 per year/kWh

- So this would be about $520/year But the heater only runs at most 5 hours/day so about 1/5th

of the time- So $520-> $100/yr

But I only use it in the winter (say 1/2 of the year) - So now it’s $50/yr

But I only use it when we would be using heat so it adds heat to the house- This is about a factor of 2 less efficient than my heat

pump - So now it’s $25/yr

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So what did we do?

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Fluorescent Lamps

Low pressure mercury discharge gives off UV UV hits a fluorescent coating that emits a white light

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What about mercury?

CFLs typically have 3-5 mg of Hg (as do all fluorescents)

About 1/3 of all Hg emissions come from coal power plants

According to EPA about 50 tons Hg are emitted each year by coal plants

They generate 2 X 1012 kWh of electricity per year- Coal produces 50 X 109 mg/2X1012 kWh = 2.5 X 10-2 mg/kWh

- A 100 W incandescent bulb lasts about 2000 hrs., using a total of 200 kWh of electricity.

- If all from coal this would be lead to 5 mg of Hg

- Bottom line: mercury is about the same (assuming we do NOT recycle CFLs)

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LEDs - Light emitting diodes

Even more efficient than CFLs Different colors Now used in traffic lights, car tail lights Still too expensive for straight replacement

The New Year’s ball in Times Square

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Stopping Heat Loss at Home

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http://www.iranalyzers.com/home/

Insulation

Heat transfer:-Radiation-Convection-Conduction

Eliminating radiation losses - use layers(Note: infrared doesn’t go through glass)

Stefan-Boltzmann Law: Power radiated = A T4

T1 T2

A T14

A T24 P1 = A T1

4 - T24 )

P1 = A T14 - Ti

4 ) =

= A T14 - (1/2)(T1

4 + T24))

= A (1/2) (T14 - T2

4)

-> 2X less power lost!

T1 T2

A T14

A T24

Ti

A Ti4

A Ti4

Balance: T14 + T2

4 = 2 Ti4

Ti4 =(1/2)(T1

4 + T24)

Add intermediate layer:

Double pane window

Outside(cold)Inside

(warm)

Convection loss

Easy: seal up any cracks, block drafts

Problem:- If your house is too tightly sealed, may have problems

with indoor air quality

- Average US house - changes air 1 - 1.5X per hour- Can be reduced to ~ 0.2X per hour safely- But depends on building materials- Formaldehyde in FEMA trailers!

Conduction loss

Use insulation

- Measured with R value- Rate of heat transfer = A T/R- R-1 about 1 inch of still air

- R-values add

- In MD we should have R-30 in our attics

Windows

Can be responsible for up to 40% of heat loss Single pane -> double pane ->triple pane

As good as R-10

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UMD's 'WaterShed' Wins Solar Decathlon 2011

Home's Innovative Sustainablity Inspired by the Chesapeake Bay

UMD's WaterShed combines energy efficiency and water conservation

Click all images for hi-res.

COLLEGE PARK, Md. - The University of Maryland's innovative WaterShed House has won the highly competitive U.S. Department of Energy Solar Decathlon 2011.

http://newsdesk.umd.edu/engaged/release.cfm?ArticleID=2529

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LEED Certification

Leadership in Energy & Environmental Design (LEED)- Defines a “Green Building standard”

Points are distributed across in categories such as: - Sustainable Sites, - Water Efficiency, - Energy and Atmosphere, - Materials and Resources, - Indoor Environmental Quality

Rating- Certified - 40 - 49 points- Silver - 50 - 59 points- Gold - 60 - 79 points- Platinum - 80 points and above

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First Platinum Re-Developed Building

1225 Connecticut Avenue, N.W., located in the Dupont Circle neighborhood

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Passive Solar

Passive Solar

Home heating - First Law vs. Second Law

First Law Efficiency:- Energy out/energy in Example: resistive electric heat ~ 100% efficient (1st

Law) Heating requires relatively low temperatures

(don’t want 500 deg air blowing out of ducts)- Need to go from Toutside

~ 273 K to Tinside ~ 300 K- Wouldn’t we be better off moving heat around, especially since the indoor and outdoor temperatures are not too different?

- Second Law Efficiency:- Energy of absolute best process (Carnot)/(energy in)- Tinside

/(Tinside-Toutside)=300 K/27k= 11

- Now electric heat is 9% efficient (2nd law) : We have lots of room for improvements!

My (parents) home is heated with…

1. Natural gas2. Propane3. Oil4. Electric (resistive) heat5. Heat Pump6. Solar7. I have no clue.

FurnacesOil -popular in New EnglandNatural gasPropane

Very efficient (1st Law)>90%

Not a lot of room for improvements

Home heating

Heat Pumps

Move heat from outside to inside ( a refrigerator run backwards - cooling the outdoors)

Heat Pumps

Rated with SEER rating (Seasonal Energy Efficiency rating)

SEER = ratio of seasonally averaged cooling power in BTU/h compared to Watts of electricity used (measured when used as air conditioner)

e.g. SEER of 16 produces almost 5X more cooling power than it uses in electricity

-remember - we are moving heat so we can have a 1st Law efficiency > 1!

-Why don’t we all have heat pumps?

A Cool Idea

Dig down 20 ft. and the ground temperature is about 55 F Why not use this as a source of heat in the winter, and as a

place to dispose of heat in the summer?