How I Built a Zero CarbonFootprint House
Chandu VisweswariahDistinguished Engineer and Senior ManagerTiming and Circuit AnalysisIBM Systems and Technology GroupEast Fishkill, NY, USA
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SummaryZero carbon footprint house built in May 2009; no oil, gas, propane, coal, nuclear
energy
IBM ResearchYorktown Heights, NY
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Outline
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. Conclusions Outside the scope of this discussion
Global warming and its effects Energy policy and “dependence on
foreign oil” The frustrations of building a house
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Geothermal intuition
Ever been inside a cavein the summer? The cave is cool!
During the winter, that same constant cave temperature is warmer than the air outside
The earth is an abundant source of energy at a constant temperature year-round*
In the winter, ground source heat pumps move heat from the earth into your house; in the summer, they pull heat from your home and discharge it into the ground
*7oC (45oF) to 18oC (75oF) depending on latitude; 12.6oC (53oF) in New York
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Winter
Basic idea (one example)
Summer
Hot
pur
on
Col
d pu
ron
Col
d pu
ron
Hot
pur
on
Drawing courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Closed vertical loop
6 m (20’) bore spacing (7.5 m (25’) in our case),91 m (300’) deep
Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Closed horizontal loop
Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Closed pond loop
Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Pond loop photos
Copper pipe
HDPE pipe
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Open loop
Courtesy popularmechanics.com
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How a heat pump works
Low pressureLow boiling point: gas
Accepts latent heatLow temperature
Compressor
High pressureHigh boiling point: liquidGives out latent heatHigh temperature
Expansion valve
Courtesy etccreations.com
Con
dens
or
Eva
pora
tor
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Enthalpy curves for refrigerants
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System in our basement
Heat pump Heat pump Heat pump
Zone valves
Air handler Heat exchange
coils
To
radi
ant
zone
s
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Refrigerant
Direct exchange (DX) Copper pipes with puron under pressure More efficient Allows for domestic hot water
Indirect exchange Glycol + water mixture (also known as
“anti-freeze” or “brine”) PEX piping Less efficient
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Properties of Puron Puron is R-410A, a non-proprietary 50/50
blend of 2 non-chlorinated refrigerants Azeotropic blend* with negligible glide
temperature (0.3oF) History
1987 Montreal Protocol 1990 U.S. Clean Air Act Amendments R-11 and R-12 (CFCs) phased out 1995
HCFCs have lower ozone-depleting potential R-22 (freon) production stopped Jan 1, 2010,
phase-out date for existing units 2030 AlliedSignal/Honeywell invented Genetron AZ-20
(HFC) which was given a generic name R-410A, brand name Puron
*Same boiling point, so cannot be separated by fractional distillation; same composition in liquid and vapor states when distilled or partially evaporated
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Puron vs. freonASHRAE number R-410A R-22
Type of refrigerant HFC azeotropic mixture of HFC-32 and HFC-125
HCFC
Chemical name Difluoromethane (R-32)Pentafluoroethane (R-125)
Chlorodifluoromethane
Chemical formula CH2F2 (R-32) 50% by mass,CHF2CF3 (R-125) 50%
CHClF2
Molecular weight 72.6 86.5
Specific heat of liquid (at 86oF) 0.42 Btu/lb-oF 0.31
Specific heat of vapor at constant pressure CP (at 86oF, 1.0 atm)
0.21 Btu/lb-oF 0.16
Ozone depletion potential (ODP)* 0.00 0.05
Montreal Protocol phase out date None 2030
*ODP: a normalized indicator of the ability of a refrigerant to destroy stratospheric ozone molecules referenced to a value of 1.000 for CFC-11
Higher pressure, lower mass flow, quieter, 31% higher heat-carrying capacity
For more comparison data, see Appendix
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Puron enthalpy curves
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Distribution within the house
Forced air works, but radiant is best
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Sub-floor radiant
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Air source heat pumps
Recent breakthroughs allow operation at low temperatures, but with lower COPs
No wells, no trenches! The face of the future?
Mitsubishi Mr. Slim 26 SEER 9,000 BTU Heat
Pump INVERTER Mini Split System
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Outline
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. Conclusions Outside the scope of this discussion
Global warming and its effects Energy policy and “dependence on
foreign oil” The travails of building a house
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Average solar irradiance W/m2
Fastest growing source of energy 12,400 MW worldwide by year-end 2007
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Basic physics: light electricity
Photons from sunlight hit silicon Some pass through (lower energy), some reflect,
some are absorbed (energy > band gap) These create electron/hole pairs Pairs that don’t recombine form a DC current An inverter is used to produce AC current No easy way to store this energy!
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Stand-offs/mounting
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Inverter (in garage)From panels
Dis
conn
ect
Inverter
Privatemeter
To utilitymeter
8,871kWhr
to date
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PVWATTS
Performance calculator for grid-connected PV systems http://rredc.nrel.gov/solar/codes_algs/PVWATTS
Inputs to the program Location (latitude, longitude, elevation) DC rating of panels (e.g., 5 kW) DC to AC derate factor (e.g., 0.77) Array type (fixed, 1-axis tracking, 2-axis
tracking) Array tilt (e.g., 37o for a 9/12 roof) Array azimuth (e.g., 180o for a South facing roof)
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Type of arrays
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Energy production by month
Assume dc rating=5 kW, inverter derating=0.77, azimuth=180o, pitch=36.9o (9/12), total annual kWh=6,121/7,615/7,840
0
100
200
300
400
500
600
700
800
900
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Solar radiation100Wh/m^2/daykWh fixed
kWh 1D
kWh 2D
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Energy vs. tilt and azimuth
Assume 5 kW dc, inverter derating 0.77, NYC
2500
3000
3500
4000
4500
5000
5500
6000
0 (N)
22.5 (NN
E)
45 (NE
)
67.5 (EN
E)
90 (E)
112.5 (ES
E)
135 (SE
)
157.5 (SS
E)
180 (S)
202.5 (SS
W)
225 (SW
)
247.5 (WS
W)
270 (W)
292.5 (WN
W)
315 (NW
)
337.5 (NN
W)
360 (N)
4/12 pitch
5/12 pitch
6/12 pitch
7/12 pitch
8/12 pitch
9/12 pitch
10/12 pitch
11/12 pitch
12/12 pitch
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Ideal conditions South-facing single
roof Solar south* is 13o
West of South A 9/12 pitch is ideal No chimneys, poles, trees in the way In our case
7.6 KW system 8,100 kWhr per year average
Eliminates 14,000 lbs of CO2 per year We have net metering and time-of-day
billing
*Solar south is the angle of the sun at solar noon
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Outline
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. Conclusions Outside the scope of this discussion
Global warming and its effects Energy policy and “dependence on
foreign oil” The travails of building a house
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3. Other considerations Insulation
Polar walls R-30 (2x8) Double-fascia roof R-51
Windows Double-pane, low-e
argon coating 100% compact fluorescent lamps (CFLs)
Think “passage lighting” during design Can now use with dimmers!
Transportation alternatives Use bicycles, carpool, hybrids, electric cars, public
transportation… “Passive power” reduction/instrumentation
Instrumentation is a powerful way to change habits Reduce, recycle, reuse
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Outline
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. Conclusions Outside the scope of this discussion
Global warming and its effects Energy policy and “dependence on
foreign oil” The travails of building a house
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Conclusions We use our geothermal system for heating,
cooling and hot water We use our photovoltaic solar panels for
our electricity needs Net metered, time-of-day billing
Good insulation Energy-efficient bulbs and appliances Our investment will be recovered in ~9
years Technology is available; investment is the issue
We are treading a little softer on this earth Who knows what the future has in store?
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Imagine? Floating wind turbines
The first units in production will be 4 kWresidential units that will cost $10,000
Information courtesy of Paul Villarrubia
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Energy from photosynthesis?
http://www.popsci.com/technology/article/2010-03/video-artificial-photosynthesis-produces-enough-energy-power-house-one-bottle-water
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Thank you!