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How I Built a Carbon-Neutral House

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1 How I Built a Carbon-Neutral House
Chandu Visweswariah March 15, 2010 Good afternoon. Long journey that started at 2 a.m. Pacific Time Compliment to Jaijeet Seriously, Jaijeet, thank you for inviting me to the “high temple” of EECS, Cory Hall at UC Berkeley Let’s have some fun with this topic

2 Do not copy without permission
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! LEEDS certification is beyond my pay grade – I will leave that to actors, actresses, wall streeters and sports stars who are clearly the highest contributors to our society! How I built a carbon-neutral house Do not copy without permission

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Agenda and purpose Geothermal heating, cooling and domestic hot water Photovoltaic solar panels Other considerations $$$ (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 2 main sections: geothermal and solar This is not a political talk, and I won’t do an Al Gore on you But with your permission, I will show just 1 political chart How I built a carbon-neutral house Do not copy without permission

4 The only “political” chart today*
This is from yesterday’s New York Times and I think it speaks for itself. I am a member of the Union of Concerned Scientists that does wonderful work in informing the Government and public about environmental issues. At the risk of being politically incorrect, I would accuse those who spread FUD about global warming of retarding our response to this crisis – and I feel relatively free to say something like this at UC Berkeley. If you agree, let’s hear a round of applause. How I built a carbon-neutral house Do not copy without permission *New York Times, 03/14/10

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1. Geothermal Goal: avoid burners, furnaces, oil tanks, propane, natural gas How I built a carbon-neutral house Do not copy without permission

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

7 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 Air source heat pumps are often used in the Southern parts of the United States *7oC (45oF) to 18oC (75oF) depending on latitude How I built a carbon-neutral house Do not copy without permission

8 Basic idea (one example)
Summer Winter Hot puron Cold puron Cold puron Hot puron Use animation to explain How I built a carbon-neutral house Do not copy without permission Drawing courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

9 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 loop means that the energy exchange fluid goes round and round in a closed system How I built a carbon-neutral house Do not copy without permission

10 Closed vertical loop Cannot put the wells closer than 20’ apart because they compete for the same heat or coolness; there are also systems that use oblique drilling so as to have a single well-head for easy maintenance 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 Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

11 Closed horizontal loop
Need a larger backyard How I built a carbon-neutral house Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

12 Closed pond loop Need a pond or lake on your property; we have a 130-foot deep lake on our property, but the Town would never allow any excavation close to it due to wetlands provisions How I built a carbon-neutral house Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

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Pond loop photos Copper pipe HDPE pipe Again both DX and indirect exchange are possible How I built a carbon-neutral house Do not copy without permission

14 Open loop Pull water at 53 degrees F from the earth, and discharge it into a nearby stream or aquifer after you are done extracting energy or adding energy from/to the water. How I built a carbon-neutral house Do not copy without permission Courtesy popularmechanics.com

15 How a heat pump works Compressor
Low pressure Low boiling point: gas Accepts latent heat Low temperature High pressure High boiling point: liquid Gives out latent heat High temperature Evaporator Condensor Start the explanation at the compressor: Compress the refrigerant At high pressure, its boiling point is higher, so it becomes a liquid; gas->liquid transition gives out heat Let out the pressure At low pressure, its boiling point is lower; so it becomes a gas; liquid->gas transition absorbs heat. Cycle is: high pressure+liquid -> low pressure+gas over and over. The photograph shows a heat pump with my toolbox in the foreground to give you a sense of size. Expansion valve How I built a carbon-neutral house Do not copy without permission Courtesy etccreations.com

16 How a heat pump works, part 2
Basic cycle assuming indirect exchange (click on web page): Absorb heat from the earth Transfer this heat to the refrigerant when it evaporates Put out the heat when the refrigerant condenses How I built a carbon-neutral house Do not copy without permission

17 How a heat pump works, part 3
Note 4 different modes assuming indirect exchange (see web site), explain in this order: Heating (as shown on this chart) with a fan convector (forced air) or radiant heat; Domestic hot water (same as (a), but upper right loop on the right hand side); Passive cooling with heat pump off; Cooling with separate water heating function (heat pump on). How I built a carbon-neutral house Do not copy without permission

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

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

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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 Does anyone know what an azeotropic blend means? Azeotropic mixture: A mixture of two substances that has a constant boiling point and cannot be separated by fractional distillation. A liquid mixture of two or more substances that retains the same composition in the vapor state as in the liquid state when distilled or partially evaporated under a certain pressure. Temperature Glide - the temperature difference that occurs between the vapor state and liquid state during evaporation or condensation at constant pressure, i.e. the temperature in the evaporator and condenser is not constant. Temperature glide occurs in near-azeotropic and zeotropic mixtures. Montreal protocol: get rid of R-11 and R-12 (CFCs) by 1995 Congress passed the 1990 Clean Air Act Amendments As a result of these two, CFCs were replaced by HCFCs (R-22, freon) in 1995 How I built a carbon-neutral house Do not copy without permission *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. 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) 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 ASHRAE = American society of Heating, Refrigeration and Air-Conditioning Engineers Puron use requires synthetic lubricants Higher pressure, lower mass flow, quieter, 31% higher heat-carrying capacity For more comparison data, see Appendix How I built a carbon-neutral house Do not copy without permission *ODP: a normalized indicator of the ability of a refrigerant to destroy stratospheric ozone molecules referenced to a value of for CFC-11

22 Enthalpy curves for refrigerants
Start at F and work your way around the cycle for explanation purposes. Regions: Superheated (compress, boiling point goes up) Wet (condenses to liquid, gives out heat, enthalpy goes down) Expands (lower pressure) Evaporates (lower boiling point, becomes gas, absorbs heat, enthalpy goes up) Subcooled region is not entered. How I built a carbon-neutral house Do not copy without permission

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Puron enthalpy curves The “real” curves How I built a carbon-neutral house Do not copy without permission

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System in our basement To radiant zones Zone valves Air handler Heat exchange coils Point out the components Heat pump Heat pump Heat pump How I built a carbon-neutral house Do not copy without permission

25 Winter HP1 HEC1 HP2 HEC2 HP3 HEC3 HP4 HEC4 Domestic hot water tank HP5
From well tank HP5 HEC5 To house Well Winter Tank for house heating/cooling Radiant zones Return For topping off Air handlers Return How I built a carbon-neutral house Do not copy without permission

26 Summer HP1 HEC1 HP2 HEC2 HP3 HEC3 HP4 HEC4 Domestic hot water tank HP5
From well tank HP5 HEC5 To house Tank for house heating/cooling Return Air handlers For topping off Summer How I built a carbon-neutral house Do not copy without permission

27 Distribution within the house
Forced air works, but radiant is best How I built a carbon-neutral house Do not copy without permission

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Sub-floor radiant How I built a carbon-neutral house Do not copy without permission

29 Well drilling in “emory” land
Our property is the site of an abandoned emory mine which is great for geothermal, but lousy for drilling How I built a carbon-neutral house Do not copy without permission

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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? How I built a carbon-neutral house Do not copy without permission

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Agenda and purpose Geothermal heating, cooling and domestic hot water Photovoltaic solar panels Other considerations $$$ (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 How I built a carbon-neutral house Do not copy without permission

32 Average solar irradiance W/m2
Fastest growing source of energy 12,400 MW worldwide by year-end 2007 How I built a carbon-neutral house Do not copy without permission

33 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! How I built a carbon-neutral house Do not copy without permission

34 Ideal conditions South-facing single roof A 9/12 pitch is ideal
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 How I built a carbon-neutral house Do not copy without permission *Solar south is the angle of the sun at solar noon

35 Stand-offs and mounting
How I built a carbon-neutral house Do not copy without permission

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Stand-offs How I built a carbon-neutral house Do not copy without permission

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Inverter (in garage) From panels Inverter Private meter Disconnect 8,871 kWhr to date To utility meter How I built a carbon-neutral house Do not copy without permission

38 PVWATTS Performance calculator for grid-connected PV systems
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) More explanation coming How I built a carbon-neutral house Do not copy without permission

39 DC to AC derating factor
Component Derate Factors PVWATTS Default Range PV module nameplate DC rating 0.95 Inverter and Transformer 0.92 Mismatch 0.98 Diodes and connections 0.995 DC wiring AC wiring 0.99 Soiling System availability Shading 1.00 Sun-tracking Age Overall DC-to-AC derate factor 0.77 How I built a carbon-neutral house Do not copy without permission

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Type of arrays How I built a carbon-neutral house Do not copy without permission

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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 Heading Azimuth Angle (°) N 0 or 360 NE 45 E 90 SE 135 S 180 SW 225 W 270 NW 315 How I built a carbon-neutral house Do not copy without permission

42 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 How I built a carbon-neutral house Do not copy without permission

43 Energy vs. tilt and azimuth
Assume 5 kW dc, inverter derating 0.77, NYC Conclusions: If you are facing S, pitch does not matter If you are not facing S, your sensitivity to pitch increases If you are not facing S, shallower is better! How I built a carbon-neutral house Do not copy without permission

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Agenda and purpose Geothermal heating, cooling and domestic hot water Photovoltaic solar panels Other considerations $$$ (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 How I built a carbon-neutral house Do not copy without permission

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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 Consider foam for insulation – but you need active air exchange to avoid condensation problems. Consider an energy audit! Instrumentation is a powerful way to modify human habits How I built a carbon-neutral house Do not copy without permission

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Agenda and purpose Geothermal heating, cooling and domestic hot water Photovoltaic solar panels Other considerations $$$ (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 Needs to be sustainable both environmentally and economically! How I built a carbon-neutral house Do not copy without permission

47 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 How I built a carbon-neutral house Do not copy without permission

48 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! In our case, 15 tons of heat, 11 tons of A/C How I built a carbon-neutral house Do not copy without permission *R. Nevin and G. Watson, Appraisal Journal, October 1998, pp. 401—409

49 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 Hint: claim 2 years in a row! I will not ask you to consult your accountant; I am a do-it-yourself kind of guy. Rather, I would ask you to “trust but verify.” How I built a carbon-neutral house Do not copy without permission

50 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 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 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 How I built a carbon-neutral house Do not copy without permission

51 California information
Expected Performance-Based Buy-Down Performance-Based Incentive How I built a carbon-neutral house Do not copy without permission

52 Berkeley has special financing
How I built a carbon-neutral house Do not copy without permission

53 LA funds solar by electric premiums
Most interesting sentence of this article has nothing to do with solar panels. The article is memorable only because of this sentence: “It seems as though environmentalists outnumber rattlesnakes in many parts of the sprawling city.” How I built a carbon-neutral house Do not copy without permission

54 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 Do not copy without permission Information courtesy of Paul Villarrubia

55 Energy from photosynthesis?
How I built a carbon-neutral house Do not copy without permission

56 Do not copy without permission
Thank you! How I built a carbon-neutral house Do not copy without permission

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Appendix Properties of puron vs. freon Basic physics: electricity  light How I built a carbon-neutral house Do not copy without permission

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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) 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 ASHRAE = American society of Heating, Refrigeration and Air-Conditioning Engineers How I built a carbon-neutral house Do not copy without permission

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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 ANSI/ASHRAE Standard Safety Group Classification A1 Ozone depletion potential (ODP)* 0.00 0.05 Global warming potential (GWP)**, 100 yr. 1,997 1,780 Montreal Protocol phase out date 2030 Lower TEWI*** (Total Equivalent Warming Impact) Higher pressure, lower mass flow, quieter, higher efficiency, synthetic lubricants Over 1,000,000 units ODP: a normalized indicator of the ability of a refrigerant to destroy stratospheric ozone molecules referenced to a value of for CFC-11. GWP: a mass-weighted average indicator of the ability to trap radiant energy as a greenhouse gas relative to carbon dioxide (CO2) for a 100-year integration period. TEWI: takes into account direct effects (refrigerant leaks into the atmosphere: 7.5%) and indirect effects (effects from electricity production used to run the system: 92.5%). *ODP: a normalized indicator of the ability of a refrigerant to destroy stratospheric ozone molecules referenced to a value of 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%). How I built a carbon-neutral house Do not copy without permission

60 Basic physics: electricity  light
How I built a carbon-neutral house Do not copy without permission Courtesy Wikipedia and HowStuffWorks.com


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