Heating Systems & Approaches for Energy Efficient Homes

Size: px

Start display at page:

Download "Heating Systems & Approaches for Energy Efficient Homes"

Hilary Ward
6 years ago
Views:

1 Heating Systems & Approaches for Energy Efficient Homes Skip Hayden Renewables & Integrated Energy Systems Better Buildings by Design 10 Burlington VT February 2010 Natural Resources Canada Ressources naturelles Canada

4 ?? What are you looking for????

5 What do you mean by a low heat load home?

7 CCHT Mid-to-Low-Load Research Houses Located in Ottawa Two identical research houses Townhouse-type demo/mtg centre Houses are run under Simulated Occupancy Protocol (virtual family + dog)

8 Fuel Properties

9 Ultimate Analysis & HHV for Different Fuels (Dry Basis) Property Wood No.2 Oil Propane Natural Gas Carbon Hydrogen Sulphur Trace Nitrogen Ash 0.3 Oxygen Moisture 5-60 HHV, MJ/kg HHV, MJ/vol 38.2/L 25.3/L 37.5/m 3

10 Carbon & Hydrogen in Fuels % by Wt Hydrogen Carbon Wood No.2 Oil Propane Natural Gas

11 Hydrogen Losses for Different Fuels Lignite Wood No.6 Oil No.2 Oil Propane Nat Gas 0

12 Gas-Fired Systems

13 Dewpoints for Gaseous Fuels o F Natural Gas Propane Excess Air, %

14 High Efficiency Condensing Furnaces (90%+) Now the minimum requirement in Canada

15 High-Efficiency Gas Furnace Powered exhaust Electronic ignition No dilution air High resistance to depressurization Excellent side-wall vent - plastic! Should be well above 90% Efficiency improves with slight oversizing Units are available at Btu/h, suiting lower energy housing

16 What about two-stage condensing furnaces? Compared to condensing furnace with PSC circ fan motor, 2-stage furnace with ECM (brushless DC) gave increased gas use to replace electrical heat Increased operation time (~ doubled) may lead to sig. increase in electrical use, unless ID fan is also ECM-type Loss of heat to distribution system may give less heat to some registers and result in homeowner upping the thermostat May give increased comfort Low firing rate may be more suitable for EE homes May be only way of getting ECM fan motor

17 Gas Boilers

18 Antique Conventional Boilers (natural draft) are still available! (at low real efficiencies and subject to depressurization) Dilution Air Combustion Air

19 Recent Major Advances in Gas Boilers

20 With boilers, it s a New Gas Burner World Power burners (mainly forced draft) Metal matrix or ceramic (cylinder, cone, plate) Low excess air (EA) High modulation with 10:1 turndown under excellent EA control, suitable for a range of house heat load demands (eg 60k to 6k btu) Ultra-Low NOx

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

22 Air Requirements of Conventional Gas Boilers & High Efficiency Condensing Gas Boilers Air Changes/hour Conv Gas Boiler Conv Gas Blr + Dilution Condensing Gas Boiler

23 Can a condensing boiler condense in low energy housing? Yes, if radiant floor Likely, if fan coil Difficult but possible if conventional hydronic, by integrating outdoor reset, reduced flowrate/increased heat exchange, service water preheat, preheat ventilation air, as with...

Condensing Boiler Condensing Boiler Preheat service water Hot Water Heater Ventilation air Preheat

24 Enhancing Condensing Boiler Operation Increased heat exchange Increase Heat Exchange Preheat Ventilation Air Lower circ flow rate Outdoor reset lowers supply temp. Condensing Boiler Condensing Boiler Preheat service water Hot Water Heater Ventilation air Preheat preheat Service Water Preheat with Service boiler Water return Return Get return water water below below dewpoint flue gas dewpoint!

25 Combined Space-Water Heating Systems

140 120 100 80 60 40 20 0 Inefficient, Tankless, Segregated, Non-Condensing Boiler with Modulation SU02, Mixed Flue Gas Analysis 70 60

26 Inefficient, Tankless, Segregated, Non-Condensing Boiler with Modulation SU02, Mixed Flue Gas Analysis Flue Gas T O2 CO2 13:47 13:53 13:58 14:03 14:07 14:12 14:17 14:22 14:27 14:32 14:37 14:42 14:47 Time Temp [C] Conc [% ]

Temp [C] 160 140 120 100 80 60 40 20 0 AT01-2, 6hr WH 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

27 Temp [C] AT01-2, 6hr WH 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 Time Conc [%] Flue Gas O2 CO2 Cycling & Post-Purging 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%

28 Efficient Low Mass Condensing Boilers with Segregated Tap water and Highly-Modulating Burners

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

highly modulating,integrated space-water-ventilating

31 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

32 Testing at CCHT showed a 10% energy savings over three state-of-the-art individual units

33 Oil-Fired Systems

34 Most crucial element to achieve good performance and high efficiency is the oil burner

36 High Static Burners

37 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 lower with ultra-low S fuel Efficiency should be % Minimal sooting/degradation Should be burner of choice for low energy homes

38 Oil in an Energy-Efficient Home?

39 Problems with Oil Nozzles at Low Firing Rates

40 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 Canadian houses are now being designed at a Heat Load of Btu/h and below Means over-design of 1.7 and more! Becomes more/less significant depending on how heating load is distributed re design temperature (Flat vs triangle)

41 Other Possibilities Nozzles of 0.4 gph, although they often clog or their spray pattern deteriorates quickly, leading to sooting, coking, failure Using a lighter fuel might help this problem, as might a very low S fuel I have a difficult time recommending keosene. Another possibility is...

42 Combined Space-Water Heating Systems

gas temperature Reduced life Inefficient Much lower AFUE

43 Relatively cheap However, this does not mean: Combo Conventional Tank Water Heater with Fan Coil High flue gas temperature Reduced life Inefficient Much lower AFUE than furnaces, because standard does not apply Not recommended!

44 Tankless Coil Boiler or Tank-within-Tank Boilers Very inefficient summer and overall operation Large number of cycles with inherent inefficiency and sooting Not recommended!!

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

46 Oil-Fired Technologies That Can Work in Low Energy Homes Must be able to divert load, rather than just short cycle Must be able to withstand depressurization, or operate as sealed combustion Typically will use an external, wellinsulated, storage tank and water-towater exchanger for service water

47 Efficient Oil-Fired Space/Water Heating Systems

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

49 Condensing Oil Boiler + External Storage Combined Space-Water Heating

50 What about renewable energy? Let s think about renewable liquid fuels

51 Renewable Liquid Fuels Bio-oils Biodiesel Blends Alcohols...

52 Biodiesel a renewable energy resource Vegetable Oil Transesterification Methanol + Catalysts Crude Biodiesel Byproduct - Crude Glycerin

Biodiesel Properties Biodiesel is a diesel-like fuel Available from vendors now to ASTM D 6751-02 Biodiesel is completely miscible with diesel or home heating

53 Biodiesel Properties Biodiesel is a diesel-like fuel Available from vendors now to ASTM D Biodiesel is completely miscible with diesel or home heating oil (ASTM #2) Some Differences from #2 Fuel Oxygenated by ~10% by weight 8-10% higher density About 10% lower heating value Very low sulfur and nitrogen content

54 What about re-thinking oil as renewably-derived ethanol? Ethanol has only 50% the energy content of oil per unit volume! The minimum heat output is now less than 25k Btu, well suited to EE homes Ethanol burns very cleanly (transparent flame) with no particles which could clog a nozzle, so low-end nozzle limitation can be reduced still further Because of its high hydrogen content, latent heat loss is >14%, so it lends itself to condensing heat recovery If derived from cellulosic materials, such as switchgrass, it could truly be seen as a renewable fuel which does not impact the food supply

55 Alcohol-Fired Retrofitted- Condensing Furnace 95% efficient, 25k Btu output

56 For future energy solutions, flexibility can be a key ingredient

57 What is the most desired combustion system in North American homes?

58 A Fireplace!

59 Since people always seem to want a fireplace, let s take the fireplace as the centre of our integrated space-water system

60 Next Generation Integrated System: Condensing Fireplace-Based

61 Characteristics of High Efficiency Condensing Integrated Gas Fireplace Efficiency > 90% Heats space & tap water + ventilation Radiant heat from flame in winter by fire Central house heating No radiation in summer, but still hot water Pleasure of a fire!!

62 Integrating Solar Thermal with the EKoComfort Platform

63 Advanced Technologies to supply both Heat and Electricity

64 Micro-cogeneration Generating both heat and power on site to serve the thermal load 5-15 kw th and electrical load of 1-3 kw el plus the grid May employ any combination of electrical generation and storage technologies that are on or off grid Technologies Stirling Engines, IC Engines, Fuel cells, microturbines, thermophotovoltaics, thermoelectrics, solar

65 Micro-Cogen Concept

66 Micro-Cogeneration Units for EE Housing in the Lab

67 External Combustion Stirling Engine Cogeneration in EE Housing with Hot Water Phase Change Storage

68 Cogeneration in Energy Efficient Housing with Borehole Storage Micro-cogen engine with 6 kw electric & 10:1 turndown 40% efficient gen.; 90% overall Heat not use for space or hot water is put down into boreholes, for seasonal storage & utilization; brought back up thru GSHP at COP 3 Heat & electricity can also be moved back and forth across boundaries

69 For more on this subject, come to my session after lunch entitled Is there a KW in your future?

70 Now for a real integrated solution

71 Drake Landing Solar Community

provided by Solar District Energy System with energy storage Short term: 2 hot

72 Energy-Efficient, Low GHG: Drake Landing Solar Community 52 two-storey, R-2000 detached homes in Alberta 1 st in world with high (~90% solar heating) Heat provided by Solar District Energy System with energy storage Short term: 2 hot water storage tanks Long term: 144 borehole thermal energy storage backup: natural gas boiler

73 Other Alternatives for EE homes Local space heating and cooling with highly energy-efficient and renewablysourced energy Come to the session tomorrow afternoon entitled Ductless and Pipeless

75 Summary For low heat load houses: With gas, the new, highly-modulating burners in combined condensing boilers allow the satisfaction of any heat load. Efforts in installation and control must be made to ensure condensing Consideration should be given to ekocomfort-type systems, which can supply space and water heating, along with heat recovered ventilation, through a fan coil-based warm air system Oil boilers, equipped with high static burners, for space and water heating, and having external, segregated hot water storage, and the ability to limit cycling through utilization of that storage, can satisfy low heat loads and comfort at high efficiency In the near future, if ethanol can be made bio-fashion, condensing alcohol oil furnaces and boilers offer a renewable alternative Intelligent, flexible integrated systems, allowing for renewable energy inflows, appear the most promising systems for EE, low GHG homes Further integration, such as micro-cogeneration systems, and/or local space conditioning merit further consideration

76 Review of Objectives Determine which oil- and gas-fired heating technologies are well-suited to low heat load homes Assess the pros and cons of different systems Examine the next generation of integrated systems See how many of these lead towards net-zero homes

77 Heating Publications nrcan.gc.ca/index_e.cfm under Consumers: Heating, Cooling & Ventilation

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

Micro-Cogeneration: Is There a KW in Your Future?

Micro-Cogeneration: Is There a KW in Your Future? Skip Hayden Renewable and Integrated Energy Systems Better Buildings by Design 2010 Burlington, February 2010 Natural Resources Canada Ressources naturelles