How I Built a Carbon-Neutral House Chandu Visweswariah March 15, 2010.

How I Built a Carbon-Neutral House

Chandu VisweswariahMarch 15, 2010

How I built a carbon-neutral house Do not copy without permission 2 of 56

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!


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


The only “political” chart today*

*New York Times, 03/14/10


1. Geothermal


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


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


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


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


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


Closed horizontal loop



Closed pond loop



Pond loop photos

Copper pipe

HDPE pipe


Open loop

Courtesy popularmechanics.com


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


How a heat pump works, part 2

http://www.dimplex.de/animationen/kreislauf.php?lang=en


How a heat pump works, part 3

http://www.dimplex.de/animationen/waermepumpe-passiv.php?lang=en


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


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


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


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


Enthalpy curves for refrigerants


Puron enthalpy curves


System in our basement

Heat pump Heat pump Heat pump

Zone valves

Air handler Heat exchange

coils

To

radi

ant

zone

s


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


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


Distribution within the house

Forced air works, but radiant is best


Sub-floor radiant


Well drilling in “emory” land


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


Agenda and purpose







Average solar irradiance W/m2

Fastest growing source of energy 12,400 MW worldwide by year-end 2007


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!


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


Stand-offs and mounting


Stand-offs


Inverter (in garage)From panels

Dis

conn

ect

Inverter

Privatemeter

To utilitymeter

8,871kWhr

to date


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


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


Type of arrays


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


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


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


Agenda and purpose







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


Agenda and purpose







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


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


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


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


California information

Expected Performance-Based Buy-Down

Performance-Based Incentive


Berkeley has special financing


LA funds solar by electric premiums


Imagine? Floating wind turbines

The first units in production will be 4 kWresidential units that will cost $10,000

Information courtesy of Paul Villarrubia


Energy from photosynthesis?

http://www.popsci.com/technology/article/2010-03/video-artificial-photosynthesis-produces-enough-energy-power-house-one-bottle-water


Thank you!


Appendix

Properties of puron vs. freon Basic physics: electricity light



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



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%).


Basic physics: electricity light

Courtesy Wikipedia and HowStuffWorks.com

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How I Built a Carbon-Neutral House Chandu Visweswariah March 15, 2010.

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