Post on 28-Mar-2015
How I Built a Carbon-Neutral House
Chandu VisweswariahMarch 15, 2010
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Summary We built a carbon-neutral house in Croton-
on-Hudson, NY We have been living in the house since May,
2009 including one tough winter No carbon products involved or burned for
our house’s energy needs No oil, no propane, no natural gas, no electricity
produced from coal (or nuclear plants) Carbon-neutral house == Carbon-neutral
home No compromises on comfort
No attempt to construct the house in a sustainable manner/sustainable materials Adds too much to the cost!
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Agenda and purpose
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. $$$ (costs, incentives, pay back
periods) 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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The only “political” chart today*
*New York Times, 03/14/10
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1. Geothermal
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Intuition
Ever been inside a cave inthe summer? The cave is cooler than the
air outside During the winter, that same constant cave
temperature is warmer than the air outside Same principle behind ground source heat
pumps (GHPs) In the winter, they move heat from the
earth into your house; in the summer, they pull heat from your home and discharge it into the ground
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Geothermal principles
The earth is at a constant 12.6oC (53oF) year-round after about 2 m (6’) of depth* Depends on soil, rocky earth is better
Geothermal heating and cooling takes advantage of this abundant reservoir of heat in the winter and “coolness” in the summer
We will discuss three main parts Energy exchange with the earth Heat pump and refrigerant Distribution in the house
*7oC (45oF) to 18oC (75oF) depending on latitude
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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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Energy exchange with the earth Closed loop
Vertical loop Horizontal loop Pond loop
Open loop With underground water aquifer
Energy exchange material Direct exchange (DX): Puron under
pressure in copper pipes Indirect exchange: Glycol+water mixture
(also called “anti-freeze” or “brine”) in PEX tubing
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Closed vertical loop
6 m (20’) bore spacing (7.5 m (25’) in our case),91 m (300’) deep
Each well or set of wells used for one zone
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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How a heat pump works, part 2
http://www.dimplex.de/animationen/kreislauf.php?lang=en
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How a heat pump works, part 3
http://www.dimplex.de/animationen/waermepumpe-passiv.php?lang=en
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Domestic hot water
Desuperheater In summer, take heat that is extracted
from the house to heat hot water Heat water for free!
In winter, utilize the same mechanism used to heat water for house heating to heat water for domestic use
Reduce water-heating costs by ½ Can also heat water directly by solar
power
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Refrigerant
Direct exchange 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 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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Enthalpy curves for refrigerants
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Puron enthalpy curves
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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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Winter
Tank for househeating/cooling
Radiant zones
Return
Air handlers
Return
HP1
HEC1
HP2
HEC2
HP3
HEC3
HP4
HEC4
Domestic hotwater tank
Fro
m w
ell t
ank
HP5
HEC5
To house
Well
For topping off
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Summer
HP1
HEC1
HP2
HEC2
HP3
HEC3
HP4
HEC4
Domestic hotwater tank
Fro
m w
ell t
ank
HP5
HEC5
To house
For topping offTank for househeating/cooling
Return
Air handlers
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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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Well drilling in “emory” land
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Air source heat pumps
Recent breakthroughs allow operation at low temperatures
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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Agenda and purpose
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. $$$ (costs, incentives, pay back
periods) 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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Ideal conditions
South-facing singleroof 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
*Solar south is the angle of the sun at solar noon
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Stand-offs and mounting
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Stand-offs
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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)
Mor
e ex
plan
atio
nco
min
g
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DC to AC derating factor
Component Derate Factors
PVWATTS Default
Range
PV module nameplate DC rating 0.95 0.80 - 1.05
Inverter and Transformer 0.92 0.88 - 0.96
Mismatch 0.98 0.97 - 0.995
Diodes and connections 0.995 0.99 - 0.997
DC wiring 0.98 0.97 - 0.99
AC wiring 0.99 0.98 - 0.993
Soiling 0.95 0.30 - 0.995
System availability 0.98 0.00 - 0.995
Shading 1.00 0.00 - 1.00
Sun-tracking 1.00 0.95 - 1.00
Age 1.00 0.70 - 1.00
Overall DC-to-AC derate factor 0.77
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Type of arrays
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Tilt angle and azimuth
Roof Pitch Tilt Angle (°)
4/12 18.4
5/12 22.6
6/12 26.6
7/12 30.3
8/12 33.7
9/12 36.9
10/12 39.8
11/12 42.5
12/12 45.0
HeadingAzimuth Angle (°)
N 0 or 360
NE 45
E 90
SE 135
S 180
SW 225
W 270
NW 315
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Energy production by month
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
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
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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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Agenda and purpose
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. $$$ (costs, incentives, pay back
periods) Outside the scope of this discussion
Global warming and its effects Energy policy and “dependence on
foreign oil” The travails of building a house
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3. Other considerations Insulation
Polar walls R-30 (2x8) Double-fascia roof R-51
Windows Double-pane, low-e
argon coating 100% compact fluorescent lamps (CFLs)
Think “passage lighting” during design Can now use with dimmers!
Transportation alternatives Use bicycles, carpool, hybrids, electric cars, public
transportation… “Passive power” reduction/instrumentation
Instrumentation is a powerful way to change habits Reduce, recycle, reuse
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Agenda and purpose
1. Geothermal heating, cooling and domestic hot water
2. Photovoltaic solar panels3. Other considerations4. $$$ (costs, incentives, pay back
periods) 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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Rule of thumb for geothermal
1600 sq. ft. requires one 3 ton unit, one 300’ vertical well, and costs ~$10K
Add one unit/well for domestic hot water
Federal Gov’t will kick back $3K (30%) per heat pump as a tax credit
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Payback time: geothermal Federal income tax credit of 30% of the cost with no
limit till 2016 (undiminished by AMT) For everything up to the heat pump, including
labor/install; need to fill form 5695 Requires COP >= 3.5, EER >= 15 for DX systems
Different ways of looking at it HVAC system doubles in cost Provides heating at equivalent of $1.25/gallon of oil Additional monthly mortgage cost is less than the
monthly energy savings Pays for itself from day one!
$1 per year energy savings = $20.73 of house value* Our payback analysis indicates a 9 year payback
period We have no backup system for heat, A/C, hot water!
*R. Nevin and G. Watson, Appraisal Journal, October 1998, pp. 401—409
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Insulation, doors, windows
Federal income tax credit of 30% of qualified insulation, furnace, doors, windows, storm door and storm window material costs only Capped at $1,500 Must fill form 5695 Must be the first user This is a post-AMT tax credit
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Payback time: solar panels Solar panel prices are falling! Federal income tax credit of 30% of “system cost” with no limit till 2016
Survives AMT Includes labor, installation Must fill form 5695
NY state See NYSERDA web site at http://www.nyserda.com/ NY prior to 10/13/09: $4/W for the first 5 kW, $3/W for the next 5 kW NY prior to 01/11/10: $2.50/W for the first 4 kW, $1.50/W for the next 4 kW NY now: $1.75/W for the first 5 kW Incentives are higher for EnergyStar labeled homes and Built-in Photovoltaics
(BIPVs) Additional $5K tax credit; additional 8.75% property tax credit (now 5%)
VT state VT: $1.75/W for the first 5 kW
CA state See CA web site at http://www.cpuc.ca.gov/PUC/energy/solar California Solar Initiative: see next page, rebates diminish with popularity
Utility must buy back excess power at supply cost On each anniversary of installation, excess generation is paid at “wholesale
rate” “Time-of-day” billing is very advantageous for solar customers Payback period in our case is ~9 years
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California information
Expected Performance-Based Buy-Down
Performance-Based Incentive
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Berkeley has special financing
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LA funds solar by electric premiums
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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!
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Appendix
Properties of puron vs. freon Basic physics: electricity light
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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),CHF2CF3 (R-125)
CHClF2
Composition (by mass) R-32: 50%, R-125: 50% N/A
Molecular weight 72.6 86.5
Boiling point (at 1.0 atm), oF -62.9 -41.4
Freezing point (at 1.0 atm), oF -247 -256
Critical temperature, oF 163 205
Critical pressure, psia 720 722
Saturated liquid density (at 86oF), lb/ft3
64.64 73.09
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Puron vs. freonASHRAE number R-410A R-22
Specific heat of liquid (at 86oF), Btu/lb-oF 0.42 0.31
Specific heat of vapor at constant pressure CP (at 86oF, 1.0 atm), Btu/lb-oF
0.21 0.16
Flammable range (% volume in air) None None
ANSI/ASHRAE Standard 34-1992 Safety Group Classification
A1 A1
Ozone depletion potential (ODP)* 0.00 0.05
Global warming potential (GWP)**, 100 yr. 1,997 1,780
Montreal Protocol phase out date None 2030
Lower TEWI*** (Total Equivalent Warming Impact)
Higher pressure, lower mass flow, quieter, higher efficiency, synthetic lubricants
Over 1,000,000 units 1995-2004*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.
**GWP: a mass-weighted average indicator of the ability to trap radiant energy as a greenhouse gas relative to carbon dioxide for a 100-year integration period.
***TEWI: takes into account direct (refrigerant leaks into the atmosphere: 7.5%) + indirect effects (effects from electricity production used to run system: 92.5%).
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Basic physics: electricity light
Courtesy Wikipedia and HowStuffWorks.com