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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 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

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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

  2. 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! Do not copy without permission

  3. 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 Do not copy without permission

  4. The only “political” chart today* Do not copy without permission *New York Times, 03/14/10

  5. 1. Geothermal Do not copy without permission

  6. Intuition • Ever been inside a cave inthe summer? • The cave is cooler than theair 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 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 *7oC (45oF) to 18oC (75oF) depending on latitude Do not copy without permission

  8. Cold puron Hot puron Hot puron Cold puron Winter Summer Basic idea (one example) 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 Do not copy without permission

  10. 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 Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

  11. Closed horizontal loop Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

  12. Closed pond loop Do not copy without permission Courtesy of Prof. Andrew Chiasson, Oregon Instititute of Technology

  13. HDPE pipe Copper pipe Pond loop photos Do not copy without permission

  14. Open loop Do not copy without permission Courtesy popularmechanics.com

  15. How a heat pump works Compressor Low pressureLow boiling point: gasAccepts latent heatLow temperature High pressureHigh boiling point: liquidGives out latent heatHigh temperature Evaporator Condensor Expansion valve Do not copy without permission Courtesy etccreations.com

  16. How a heat pump works, part 2 Do not copy without permission http://www.dimplex.de/animationen/kreislauf.php?lang=en

  17. How a heat pump works, part 3 Do not copy without permission http://www.dimplex.de/animationen/waermepumpe-passiv.php?lang=en

  18. 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 Do not copy without permission

  19. 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 Do not copy without permission

  20. 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 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

  21. Puron vs. freon • Higher pressure, lower mass flow, quieter, 31% higher heat-carrying capacity • For more comparison data, see Appendix 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 1.000 for CFC-11

  22. Enthalpy curves for refrigerants Do not copy without permission

  23. Puron enthalpy curves Do not copy without permission

  24. System in our basement To radiantzones Zone valves Air handler Heat exchangecoils Heat pump Heat pump Heat pump Do not copy without permission

  25. HP1 HP2 HP3 HP4 HP5 HEC1 HEC2 HEC3 HEC4 HEC5 Domestic hotwater tank Tank for househeating/cooling From well tank For topping off To house Return Return Air handlers Radiant zones Well Winter Do not copy without permission

  26. HP1 HP2 HP3 HP4 HP5 HEC1 HEC2 HEC3 HEC4 HEC5 Domestic hotwater tank Tank for househeating/cooling From well tank For topping off To house Return Air handlers Summer Do not copy without permission

  27. Distribution within the house • Forced air works, but radiant is best Do not copy without permission

  28. Sub-floor radiant Do not copy without permission

  29. Well drilling in “emory” land Do not copy without permission

  30. Air source heat pumps Mitsubishi Mr. Slim 26 SEER 9,000 BTU HeatPump INVERTER Mini Split System • Recent breakthroughs allow operation at low temperatures • No wells, no trenches! • The face of the future? Do not copy without permission

  31. 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 Do not copy without permission

  32. Average solar irradiance W/m2 • Fastest growing source of energy • 12,400 MW worldwide by year-end 2007 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! Do not copy without permission

  34. Ideal conditions • South-facing singleroof • Solar south* is 13oWest 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 Do not copy without permission *Solar south is the angle of the sun at solar noon

  35. Stand-offs and mounting Do not copy without permission

  36. Stand-offs Do not copy without permission

  37. Inverter (in garage) From panels Inverter Privatemeter Disconnect 8,871kWhrto date To utilitymeter Do not copy without permission

  38. 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) More explanationcoming Do not copy without permission

  39. DC to AC derating factor Do not copy without permission

  40. Type of arrays Do not copy without permission

  41. Tilt angle and azimuth 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 Do not copy without permission

  43. Energy vs. tilt and azimuth • Assume 5 kW dc, inverter derating 0.77, NYC Do not copy without permission

  44. 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 Do not copy without permission

  45. 3. Other considerations • Insulation • Polar walls R-30 (2x8) • Double-fascia roof R-51 • Windows • Double-pane, low-eargon 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 Do not copy without permission

  46. 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 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 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! 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 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 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 Do not copy without permission

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