Downsizing after Retrofit

Transcription

1 Downsizing after Retrofit Natural Resources Resourcesnatureles Canada Canada Skip Hayden Renewables & Integrated Energy Systems BBD 2011 Burlington, Feb 2011

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5 ?? What are you looking for???

6 Renewables & Integrated Energy Systems

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9 Heat Distribution?

10 Conventional Hydronic Heating

11 Radiant Floor?

12 Furnace Fan Coil (Hydro-Air) Warm Air System

13 LOCAL SPACE HEATING?

14 A mix of heating types?

15 What do I mean by heat load & oversizing? Most homes have always had a larger-thanrequired heating system The design heat load is the amount of heat required to heat the home to the desired level at either the 1% or the 2.5% coldest day of the year, while running continuously Retrofitting a house by insulating and tightening the envelope can increase the degree of oversize to dramatic levels.

16 What is the degree of downsizing req d? What is the new design heat load? 60,000 Btu/h? 40,000 Btu/h? 20,000 Btu/h?...?

17 Efficiency What are some operational factors which affect heating system efficiency & what are the implications of significant retrofit?

18 Flue Gas Dilution Air Combustion Air Combustion Air Dilution Air Dilution Air

19 Transient Operation Off-Cycle Cyclic / Transient Operation

20 9:50 10:05 10:20 10:35 10:50 11:05 11:21 11:36 11:51 12:06 12:21 12:37 12:52 13:07 13:22 13:37 13:52 14:07 14:23 14:38 14:53 15:08 15:23 15:39 Temp [C] Conc [%] AT01-2, 6hr WH Flue Gas O2 CO2 Post-Purging Time with Cycling Operates on a fixed time length (say 30 sec) each time after the burner shuts off, to ensure combustion gases are evacuated from the system Removes fixed am t of heat from unit each cycle Loss is about 1.5% for a typical number of cycles per year (~2000 for normal furnace) If purge length is doubled, loss is doubled; similarly if no. of cycles doubles, loss doubles If unit short-cycles and number of cycles increases to (not uncommon) loss goes up 5x to 7.5%; to 20,000 means loss up to 15%

21 Energy Sources No. 2 oil Natural gas Propane Wood Electricity + electricity for fans, blowers, pumps,

22 FUEL PROPERTIES (Ultimate Analysis) Carbon Hydrogen Sulphur Nitrogen Oxygen Ash (Na, K, Fe, heavy metals ) Heating Value

23 Ultimate Analysis for Different Fuels Property No. 2 Oil Nat Gas Propane Wood Pellets Carbon 86.4% Hydrogen 13.3% Sulphur <0.3% trace Nitrogen Ash Oxygen Moisture

24 Fuel Energy Contents Heating Oil 140 kbtu/gal Natural Gas Btu/ft Btu/therm Propane Electricity 92.7 kbtu/gal 3413 Btu/kwh Mixed Hardwood 22 Mbtu/fullcord Wood Pellets 336 kbtu/bag or 16.8 MBtu / ton

25 Carbon & Hydrogen in Fuels % by Wt 90 Natural Gas has high hydrogen & a very low level of sulphur Oil can have significant sulphur + particulate emissions Hydrogen Carbon Wood No.2 Oil Propane Natural Gas

26 The hydrogen in the fuel combines with oxygen during burning, producing water, which is then boiled in the flame taking energy in the form of latent heat to change its state from liquid to vapour. For a particular fuel, this is effectively a fixed energy loss, which is called the Hydrogen Loss. It is proportional to the hydrogen in the fuel the more the hydrogen, the greater the energy loss.

27 Heat Loss, % Hydrogen Losses for Different Fuels Wood No.2 Oil Propane Nat Gas 2 0

28 Oil-Fired Systems

29 Retention Head Burner

30 With oil-fired systems, it is relatively easy to downsize the furnace/boiler, at least to a certain level, by simply reducing nozzle size, while maintaining good excess air control, provided that acceptable flue gas temperature is maintained in the venting system, especially with...

31 High Static Burners

32 High-Static Oil Burner Excellent fuel-air mixing (ExcessAir - 25%) Stable under stack (exhaust) pressure fluctuations due to wind/turbulence High resistance to house depressurization, which can be a char of low energy housing More suited to sealed combustion operation Zero off-cycle flow loss (ex post-purge) Firing rate down to 70kBtu with good excess air control; perhaps much lower with ultra-low S fuel Efficiency should be % Minimal sooting/degradation Should be burner of choice for low energy homes

33 Oil in a house made Energy-Efficient?

34 Oil House Demand vs Heat Output Potential problem with oil and energy-efficient housing, with minimum firing rate ~ 70k Btu/h This results in a minimum heat output = Btu/h; many in industry feel more comfortable at Btu/h Many houses are now being designed at a Heat Load of Btu/h and below Means over-design of 1.7 and more! Advanced burners and very low S fuel can lower this Becomes more/less significant depending on how heating load is distributed re design temperature (Flat vs triangle)

35 Combined Space-Tap Water Heating

36 NOT: Tankless Coil Boiler Very inefficient summer and overall operation Large number of cycles with inherent inefficiency and sooting

37 However, well-conceived combined systems for space and water heating can be an effective way around the technical limitation of oversizing with oil-fired equipment in energy efficient housing.

38 Efficient Oil-Fired Space/Water Heating

39 What about an Oil-Fired Condensing System?

40 Dewpoints for Different Fuels o F Excess Air, % Natural Gas Propane No. 2 Oil

41 Condensing Oil Furnace Can sidewall vent with approved plastic pipe Less energy tied up in latent heat than gas Dewpoint is low, but return air such that condensing occurs Condensate is very acidic Heat exchanger must be VERY hi grade Al-29-4C Use good high-static burner New very low S oil more suitable

42 Condensing Oil-fired Boiler High efficiency possible by recovering latent heat from water vapour in flue gas. Similar issue to condensing furnaces re potential for latent heat recovery, and corrosion potential; again, low S oil better much better Typical return water temperature (except for radiant floors) is above dewpoint, so make every effort to lower it: outdoor reset, lower flow rates In Europe, available at two stage firing, with low output of 40 kbtu (very low S fuel) Can work well (or not) with combined service water

43 Gas-Fired Systems

44 Conventional Naturally-Aspirating Gas Furnace Dilution Air Combustion Air

45 Conventional Gas Furnace Naturally aspirating Highly susceptible to depress & spillage Draft hood (extra heated air loss) Continuous pilot (energy waste) Large off-cycle loss Low seasonal efficiency ( ~ 60% ) Now an antique! Don t even think about downsizing this technology

46 Mid-Efficiency Gas Furnace Powered exhaust Electronic ignition No dilution air So-so resistance to depressurization Should NOT be efficient Loses efficiency and can give short-cycle condensation/corrosion problems in furnace or vent Now an antique in Canada Don t think of downsizing!

47 Condensing Gas Furnace Powerful powered exhaust Condenses flue gas and recovers latent heat Electronic ignition No dilution air High resistance to depressurization Excellent side-wall vent approved plastic Should be well above 90% Modulating or staged, for lower energy requirements Best have brushless DC motor Now a requirement in Canada!

48 Gas Boilers Natural Gas & Propane

49 Antique Conventional Boilers (natural draft) are still available! (at low real efficiencies) Dilution Air Combustion Air

50 Major Advances in Gas Burners - Power radiant burners - High modulation - High efficiency - Low output

51 Major Advances in Gas Boilers with these burners Condensing Gas Boilers

52 Dewpoints for Different Fuels o F Excess Air, % Natural Gas Propane No. 2 Oil

53 Condensing boilers with high modulation ideally suited to fan coils, radiant floors and low energy housing

54 Can a condensing boiler condense in lowered energy housing? Yes, if radiant floor Likely, if fan coil to warm air Possible in conventional hydronic, by integrating outdoor reset; reducing flowrate; now oversized heat exchange, service water preheat, preheat ventilation air, as with...

55 Ensuring Condensing Boiler Operation Increased heat exchange Oversized Heat Exchange Preheat Ventilation Air Lower circ flow rate Outdoor reset lowers supply temp. Condensing Boiler Condensing Boiler ** Control imp t if condensing boiler heating service water tank ** Preheat service water Hot Water Heater Ventilation air Preheat preheat Service Preheat Water with Service boiler Water return Get return water below flue gas dewpoint! Return water below dewpoint

56 In new and renovated housing: - Space Heating falling - Water Htg very inefficient - Need for fresh air - Ventilation

57 ekocomfort Advanced Integrated Mechanical Systems A major Canadian initiative to develop and market high efficiency, highly modulating,integrated space-water-ventilating systems Now includes an efficiency performance standard CSA P10

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59 When the house energy demand becomes very low with significant retrofit, it may be time to rethink the heating (and cooling) system

60 An interesting option is local space conditioning

61 Types of Local Space Heaters

62 Electric Baseboard Cheap Easy to install Allows local thermostatcontrolled zoning 100% efficient?

63 Electric Baseboard Does this really happen? Heat goes up against point of major heat loss Stays on house periphery or ceiling Needs some forced circulation High cost of electricity

64 What do I mean by local space heating? Really zoned but not trying to have all parts get equal service

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67 Characteristics of Suitable Advanced Combustion Woodstove Effective infrared heating source Ceramic glass door transparent to R radiation EPA 1990 < 4.0 g/h Preheated prim & sec air Insulated comb. chamber & baffle Air wash for door Air shield on side and back Extremely attractive, chaotic fire SMALL!

68 Pellet Stove

69 Characteristics of Good Pellet Stove Tested to EPA low emissions potential is realized high efficiency due to low excess air (up to 80%) Wide firing range (often 5:1) with low output & good air control over range Air wash for fire viewing Small diameter flue (3-4 ) Can be side-walled (& DV d) with care

70 What about a gas fireplace?

71 Characteristics of Efficient, Safe Gas Fireplace or Stove Direct vent (sealed combustion) Ceramic viewing glass front Good input/output modulation IID or easily shut-off / relit pilot Effective circulating fan with DC motor Free-standing or iinsulated outer casing High P.4 seasonal efficiency Properly sized & well-located in major living area

72 Locate these radiant space heaters in a major living area, yet where they can see a significant portion of the rest of the house

73 Advanced combustion stove or fireplace

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75 Who air-conditions now? Who would like to air-condition? Sometimes, when we ve retrofitted, cooling becomes more of an issue A/C : Invention is the mother of necessity

76 To heat local areas of the retrofitted house and to provide efficient & effective cooling consider a cold-climate mini-split heat pump

77 Mini-Split Heat Pumps for Efficient Local Heating and Cooling Mini-Split Heat Pump

78 Mini-Split Advanced Technology Inverter technology to control/vary compressor speed to load Scroll compressor Efficient DC motors with better fan design Very high SEER >20; good COP at cold temp.

79 Mini-Splits in Scandanavia

80 Shoulder-Season Performance Outdoor Temperature COP 40 o F 4.3

81 Winter Performance COP of 2 at 5 o F

82 Heating

83 Cooling

84 Energy Systems Performance & Op. Cost Property No. 2 Oil Nat Gas Propane Wood Pellets Electr Energy Content Btu/unit 140k/gal / therm 92.7/gal 22M/cord 16.4M/t 3.4/kwh Cost/Unit $ 2.49 $1.36 $2.32 $170 $ Efficiency Low Med High (-) 225 Cost/MBtu Low effic Med High $23.4 $21.0 $19.1 $17.7 $16.0 $14.3 $31.7 $29.8 $26.9 $12.9 $16.4 $38.1(+) $16.9

85 Summary In general, if you presently have a lower technology heating system, will lead to inefficiencies, discomfort, and even performance problems when you have made a major house retrofit With oil, reduced firing rate, using high static burners while eliminating the barometric damper in efficient boiler generators, connected to either hydronic or fan-coil supplied warm air systems, while putting the overflow heat into a well-insulated external tank for later space or water use permits adjusted outputs for a range of reduced heat loads With gas, highly modulating condensing boilers with advanced control strategies offer means of flexible sizing while reducing load Integrated systems, coupling space heating, water heating and heat recovery ventilation with intelligent control strategies can be an effective replacement for retrofitted homes Local space conditioning, using Vermont-tradition advanced wood stoves and the new, high-technology mini-split heat pumps can be efficient, friendly, comfortable and cost-effective ways to heat and even cool a retrofitted (or new) home.

86 Review of Objectives Understand why oversizing of heating and cooling equipment is a result of successful retrofit of homes Discuss instances and for what type of equipment this is a liability Learn if it is possible to downsize or retrofit existing equipment Know when it is best to replace or rethink heating or cooling systems

87 If further questions, contact me (Skip Hayden) Integrated Energy Systems, tel: (613) fax: (613)

88 Effect of Downsizing on Fuel Consumption (non-condensing furnace) (energy consumption vs degree days) Energy/DD 1 We generally get a straight-line increasing relationship for energy consumption as it gets colder 0 Increasing Degree Days (C) 0 30C Original

89 Effect of Downsizing on Fuel Consumption (non-condensing furnace) Energy/DD Increasing Degree Days (C) 30C Original Downsized 40% For a furnace downsizing of 40%, while maintaining the same steady state boiler efficiency, we achieved an energy savings of only ~10%