How I built a carbon-neutral house.

How I Built a Carbon-Neutral House
Chandu Visweswariah
March 15, 2010
Summary
 We built a carbon-neutral house in Crotonon-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!
How I built a carbon-neutral house
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Agenda and purpose
1. Geothermal heating, cooling and
domestic hot water
2. Photovoltaic solar panels
3. Other considerations
4. $$$ (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*
How I built a carbon-neutral house
*New York Times, 03/14/10
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1. Geothermal
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Intuition
 Ever been inside a cave in
the 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
Summer
How I built a carbon-neutral house
Hot puron
Cold puron
Cold puron
Hot puron
Basic idea (one example)
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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
How I built a carbon-neutral house
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Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Closed horizontal loop
How I built a carbon-neutral house
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Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Closed pond loop
How I built a carbon-neutral house
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Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology
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Pond loop photos
HDPE pipe
Copper pipe
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Open loop
How I built a carbon-neutral house
Courtesy popularmechanics.com
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How a heat pump works
Low pressure
Low boiling point: gas
Accepts latent heat
Low temperature
Condensor
Evaporator
Compressor
High pressure
High boiling point: liquid
Gives out latent heat
High temperature
Expansion valve
How I built a carbon-neutral house
Courtesy etccreations.com
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How a heat pump works, part 2
How I built a carbon-neutral house
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http://www.dimplex.de/animationen/kreislauf.php?lang=en
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How a heat pump works, part 3
How I built a carbon-neutral house
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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
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*Same boiling point, so cannot be separated by fractional distillation; same composition in liquid and vapor states when distilled or partially evaporated
Puron vs. freon
ASHRAE 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)
Chlorodifluo
romethane
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
 Higher pressure, lower mass flow, quieter, 31%
higher heat-carrying capacity
 For more comparison data, see Appendix
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*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
Enthalpy curves for refrigerants
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Puron enthalpy curves
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To radiant
zones
System in our basement
Zone valves
Air handler
Heat exchange
coils
Heat pump
How I built a carbon-neutral house
Heat pump
Heat pump
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Winter
HP1
HP2
HP3
HP4
HP5
HEC1
HEC2
HEC3
HEC4
HEC5
Tank for house
heating/cooling
Domestic hot
water tank
For topping off
From well tank
Well
To house
Return
Radiant zones
How I built a carbon-neutral house
Return
Air handlers
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HP2
HP3
HP4
HP5
HEC1
HEC2
HEC3
HEC4
HEC5
Domestic hot
water tank
Tank for house
For topping off
heating/cooling
From well tank
HP1
To house
Summer
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
How I built a carbon-neutral house
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Air source heat pumps
Mitsubishi Mr. Slim 26 SEER 9,000 BTU Heat
Pump INVERTER Mini Split System
 Recent breakthroughs allow operation at
low temperatures
 No wells, no trenches!
 The face of the future?
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Agenda and purpose
1. Geothermal heating, cooling and
domestic hot water
2. Photovoltaic solar panels
3. Other considerations
4. $$$ (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
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 12,400 MW worldwide
by year-end 2007
How I built a carbon-neutral house
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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 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
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*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
Disconnect
Inverter
How I built a carbon-neutral house
Private
meter
8,871
kWhr
to date
To utility
meter
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PVWATTS
 Performance calculator for grid-connected
PV systems
 http://rredc.nrel.gov/solar/codes_algs/PVWATTS
More explanation
coming
 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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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
4/12
Tilt Angle (°)
18.4
5/12
6/12
7/12
22.6
26.6
30.3
8/12
9/12
10/12
11/12
33.7
36.9
39.8
42.5
12/12
45.0
How I built a carbon-neutral house
N
Azimuth
Angle (°)
0 or 360
NE
E
SE
S
45
90
135
180
SW
W
NW
225
270
315
Heading
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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
Solar radiation
100Wh/m^2/day
kWh fixed
900
800
700
600
kWh 1D
kWh 2D
500
400
300
200
100
0
Jan
Feb
Mar
Apr
How I built a carbon-neutral house
May
Jun
Jul
Aug
Sep
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Oct
Nov
Dec
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Energy vs. tilt and azimuth
 Assume 5 kW dc, inverter derating 0.77, NYC
6000
5500
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
5000
4500
4000
3500
3000
2500
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360 (N)
337.5 (NNW)
315 (NW)
292.5 (WNW)
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270 (W)
247.5 (WSW)
225 (SW)
202.5 (SSW)
180 (S)
157.5 (SSE)
135 (SE)
112.5 (ESE)
90 (E)
67.5 (ENE)
45 (NE)
22.5 (NNE)
0 (N)
How I built a carbon-neutral house
Agenda and purpose
1. Geothermal heating, cooling and
domestic hot water
2. Photovoltaic solar panels
3. Other considerations
4. $$$ (costs, incentives, pay back
periods)
 Outside the scope of this discussion
 Global warming and its effects
 Energy policy and “dependence on
foreign oil”
 The travails of building a house
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3. Other considerations
 Insulation
 Polar walls R-30 (2x8)
 Double-fascia roof R-51
 Windows
 Double-pane, low-e
argon coating
 100% compact fluorescent lamps (CFLs)
 Think “passage lighting” during design
 Can now use with dimmers!
 Transportation alternatives
 Use bicycles, carpool, hybrids, electric cars, public
transportation…
 “Passive power” reduction/instrumentation
 Instrumentation is a powerful way to change habits
 Reduce, recycle, reuse
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Agenda and purpose
1. Geothermal heating, cooling and
domestic hot water
2. Photovoltaic solar panels
3. Other considerations
4. $$$ (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!
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*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

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

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: $1.75/W for the first 5 kW

See CA web site at http://www.cpuc.ca.gov/PUC/energy/solar
NY state
VT state
CA state

California Solar Initiative: see next page, rebates diminish with popularity

On each anniversary of installation, excess generation is paid at “wholesale rate”
Utility must buy back excess power at supply cost
“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
How I built a carbon-neutral house
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LA funds solar by electric premiums
How I built a carbon-neutral house
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Imagine? Floating wind turbines
The first units in production will be 4 kW
residential units that will cost $10,000
How I built a carbon-neutral house
Information courtesy of Paul Villarrubia
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Energy from photosynthesis?
How I built a carbon-neutral house
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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. freon
ASHRAE 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)
Chlorodifluo
romethane
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. freon
ASHRAE 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.
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59integration
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**GWP: a mass-weighted
indicator of the ability
to trap radiant
energy
a greenhouse
relative to carbon dioxide for a 100-year
***TEWI: takes into account direct (refrigerant leaks into the atmosphere: 7.5%) + indirect effects (effects from electricity production used to run system: 92.5%).
Basic physics: electricity  light
How I built a carbon-neutral house
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