1 / 64

Gestão de energia : 2012/2013

Gestão de energia : 2012/2013. Energy in Buildings Prof. Tânia Sousa taniasousa@ist.utl.pt. Energy Consumption in Buildings. Buildings account for 40% of total energy consumption in the European union What about Portugal?

gil
Download Presentation

Gestão de energia : 2012/2013

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Gestão de energia: 2012/2013 EnergyinBuildings Prof. Tânia Sousa taniasousa@ist.utl.pt

  2. EnergyConsumption in Buildings • Buildingsaccount for 40% of total energyconsumption in theEuropeanunion • Whatabout Portugal? • In 2010 the final consumptionofservices + domestic sector represented 55% ofthe final energyconsumption • Do youthinkthatthefractionofprimaryenergywouldbehigherorlower? Why?

  3. Energy Consumption in Buildings • Mosteffectivestrategy to reduceenergy use in buildings (Harvey, 2010): • Reduceheatingandcoolingloadsthrough a high-performance envelope • highdegreeofinsulation, windowswithlow U values in coldclimatesandlow solar heatgain in hot climates, externalshadingandlowairleakage • Meetthereducedload as much as possibleusingpassive solar heating, ventilationandcoolingtechniqueswhileoptimizingthe use ofdaylight • Use themostefficientmechanicalequipmentto meettheremainingloads • Ensure that individual energy-using devices are as efficient as possible and properly sized

  4. Energy Consumption in Buildings • Howmuchenergyreduction can weachieve? • Passive house standard: heating 15kWh/m2 per yearcooling 15 kWh/m2 per yearTPE  120 kWh/m2 per yearn50 ≤ 0.6 / hour From 220 kWh/m2/year to 20-40 kWh/m2/year Triple-glazedwindowswithinternalvenetianblinds & mechanicalventilationwith 82% heatrecovery

  5. Energy Consumption in Buildings • Howmuchdoes itcost?

  6. Buildings – High Performance Envelope • Theeffectivenessofthethermal envelope dependsofinsulationlevels in thewalls, ceilingandbasement • Insulationlevelscontroltheheatflowbyconduction & convectionthroughthe exterior andthe interior • U value (W/m2/K), theheattrasnfercoefficient, isequal to theheatflow per unitareaand per degreeofinside to outsidetemperaturedifference • The U valueof a layerofinsulationdependsonitslengthandtypeof material

  7. Buildings – High Performance Envelope • Theeffectivenessofthethermal envelope dependsofinsulationlevels in thewalls, ceilingandbasement Themosthighlyinsulatedhouseshave U=0.1-0.2 W/m2/K Blown-in celluloseinsulation (fillsthe gaps) Foaminsulation Vaccuminsulationpanels

  8. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheinsulationlevelsofwindows • Windows offersubstantiallylessresistance to thelossofheatthaninsulatedwalls • Single glazedwindowshave a typical U-valueof 5W/m2/K which can bereduced to to 2.5 and 1.65W/m2/K withdoubleand triple glazingbecauseoftheadditionallayersofair • The U-valueof 2.5W/m2/K ofdoubleglazedwindowscan bereducedto 2.4W/m2/K and2.3W/m2/K withArgonandkrypton • Doubleand triple glazingvaccumwindows can reducethe U value to 1.2 and0.2W/m2/K

  9. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsonthegain/lossenergybyradiation • Windows permit solar energy to enterandlossofinfraredradiation • Lowemissivitycoatingsreflect more (reduce SHGC), i.e., reduceheatgains in summerandwinter • Lowemissivitycoatingscan reducelossofheatbyinfraredradiation • Thesolar heatgaincoefficient, SHGC, isthefractionof solar radiationinicidenton a windowthatpasses throughthewindow

  10. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheairleakage • The net heatflowdue to anairexchangeat rate ris: • Thestackeffectpromotesairleakage • Coldairissuckedintothelowerpartandwarmairexits throughtheupperpartthroughcraksandopeningsbecauseitislighter. • Stackeffectcan account for up to40% ofheatingrequirementsoncoldclimates • Thewindeffect

  11. Buildings – High Performance Envelope • Theeffectivenessofthethermalenvelope dependsontheairleakage • Carefulapplicationof a continuousairbarrier can reduces rates ofairleakageby a factor of 5 to 10 compared to standard practice (enforcementofcarefulworkmanshipduringconstruction) • Buildingswithverylowairleakagerequiremechanicalventilation(95% oftheavailableheatin thewarmexhaustaircan betransfered to theincomingcoldair) to keep indoor airquality

  12. Energy Balance in Open Systems • Heat Exchangers: • Used in power plants, air conditioners, fridges, liquefication of natural gas, etc • Transfer energy between fluids at different temperatures Direct Contact Heat Exchanger Counter-flow Heat exchanger Direct Flow Heat Exchanger

  13. Buildings – The role ofshape, form, orientationandglazed % • Buildingshape & form • Havesignificantimpactsonheatingandcoolingloadsanddaylightbecauseoftherelationbetweensurfaceareaand volume • Whichone minimizes heattransferbyconductionandconvection? • Buildingorientation • For rectangular buildingstheoptimalorientationiswiththelongaxisfacingsouth • Why?

  14. Buildings – The role ofshape, form, orientationandglazed % • Glazingfractions • Highglazingfractionsincreaseenergyrequirements for heatingandcooling • Thereislittleadditionaldaylightingbenefitoncetheglazedfractionincreasesbeyond 30-50% ofthe total façadearea • Housesize • Thelivingarea per familymemberincreasedby a factor of 3 between1950 and 2000 in the US

  15. Buildings – (almost) Passive solar heating, ventilation & cooling • EvaporativeCooling:

  16. Buildings – Passive (almost) solar heating, ventilation & cooling • Thermalinducedventilation & cooling: EarthPipecooling LargeAtria

  17. Buildings – Passive (almost) solar heating, ventilation & cooling • Windinducedventilation & cooling: Windcatcher

  18. Buildings – Passive (almost) solar heating, ventilation & cooling • Passive Solar Heating & Lighting Shading Light tubes Light shelves

  19. Buildings: MechanicalEquipment • In evaluatingtheenergyefficiencyofMechanicalEquipmenttheoverallefficiencyfromprimary to usefulenergyshouldbetakenintoaccount • Thisisparticularlyimportant in the case ofusingMechanicalEquipmentsthat use electricity (producedfromfossilfuels)

  20. Buildings: MechanicalEquipment for heating • Furnaces • heatairand distribute the heated air through the house using ducts; • are electric, gas-fired (including propane or natural gas), or oil-fired. • Efficiencies range from 60 to 92%(highest for condensing furnaces) • Boilers • heat water, and provide either hot water or steam for heating; • heat is produced from the combustion of such fuels as natural gas, fuel oil, coal or pellets. • Efficiencies range from 75% to 95%(highest for condensing boilers)

  21. Buildings: MechanicalEquipment for heating & cooling • Electrical-resistance heating • Overall efficiency can be quitelow (primary -> useful) • Heat-Pumps • Overall efficiency can be quite good • It decreases with T • Air-source and ground-source • For cooling & heating • District Heating/Colling • For heating & cooling • Users don’t need mechanical equipment

  22. Buildings: MechanicalEquipmentfor cooling • Chillers • Produce cold water which is circulated through the building • Electric Chillers: use electricity • Absorption chillers: use heat (can be waste heat from cogeneration) • Electric chillers, COP = 4.0-7.5 (larger units have a higher COP) • Absorption chillers, COP = 0.6-1.2

  23. Buildings: HVAC Systems • Ventilateandheator cool bigbuildings • Allairsystems: airat a sufficientlow (high) T and in sufficient volumes iscirculatedthroughthebuilding to remove (add) heatloads • CAV: constantair volumes • VAV: variableair volumes • Airthatiscirculated in thesupplyductsmaybetakenentirelyfromtheoutsideandexhausted to theoutsidebythereturnductsor a portionofthereturnairmaybemixedwithfreshair • Incomingairneeds to becooledanddehumidified in summerandheatedand (sometimes) humidified in winter • Restrictairflow to ventilationneedsand use additionalsystems for additionalheating/cooling • Heatexchangersthattransferheatbetweenoutgoingandincomingairflows

  24. Buildings: MechanicalEquipment for waterheating • Electricaland natural gasheaters • Efficiencyof natural gasheatersis 76-85% • Efficiencyofoilheatersis75-83% • Thereisheatlossfromstoragetanks • Point-of-use tanklessheatershavelossesassociatedwiththepilot light • There are systemsthatrecoverheatfromthewarmwastewaterwith45-65 % efficiencies

  25. EuropeanDirectives • EuropeanDirectivesontheEnergy Performance ofBuildings • Directive 2002/91/EC of the European Parliament and Council (on the energy performance of buildings): • http://ec.europa.eu/avservices/video/videoplayer.cfm?ref=I048425&videolang=en&sitelang=en • This is implemented by the Portuguese Legislation RCCTE and RCESE • Directive 2010/31/EU of the European Parliament and Council (on the energy performance of buildings)

  26. Directive 2010/31/EU: Aims • Reductionofenergyconsumption • Use ofenergyfromrenewablesources • Reducegreenhousegasemissions • Reduceenergydependence • Promotesecurityofenergysupplies • Promotetechnologicaldevelopments • Createopportunities for employment & regional development • Links withaimsof SGCIE?

  27. Directive 2010/31/EU: Principles • The establishment of a commonmethodology to compute EnergyPerformace • includingthermalcharacteristics, heatingandairconditioninginstalations, renewableenergies, passive heatingandcooling, shading, natural light and design

  28. Directive 2010/31/EU: Principles • Set MinimumEnergy Performance Requirements • Requirementsshouldtake intoaccountclimaticand local conditionsandcost-effectiveness

  29. Directive 2010/31/EU: Principles • Energy Performance Requirementsshouldbeapplied to newbuildings & buildingsgoingthrough major renovations

  30. Directive 2010/31/EU: Principles • Set SystemRequirements for: energy performance, appropriatedimensioning, controlandadjustment for TechnicalBuildingSystems in existingandnewbuiildings

  31. Directive 2010/31/EU: Principles • Increasethenumberofnearly zero energybuildings

  32. Directive 2010/31/EU: Principles • Establish a systemofEnergyperformacecertificates. • Energy Performance certificates must beissued for constructed, soldorrented to newtenants • Buildingsoccupiedbypublicauthoritiesshould set na example (ECO.AP in 300 publicbuildings in Portugal)

  33. Directive 2010/31/EU: Principles • Regular maintenanceofairconditioningandheatingsystems • Independent experts

  34. Implementationofthedirectives • Directive 2002/91/EC was implemented with: • Directive 2010/31/EU was not yet implemented • DL 78/2006, the National Energy Certification and Indoor Air Quality in Buildings (SCE). • DL 79/2006, Regulation of HVAC Systems of Buildings (RSECE). • DL 80/2006, Regulation of the Characteristics of Thermal Performance of Buildings (RCCTE).

  35. RCCTE - Aims RCCTE – Aim • General aims: • Methodology for computingenergyperformaceofbuildings • Set minimumenergy performance standards • ImplementEnergyCertificationofbuildings • SpecificAims: • Limitation of annual energy needs for heating, cooling, domestic hot water and primary energy • Limitation of heat transfer coefficients • Limiting of solar factors • Installation of solar panels

  36. RCCTE – DomainofApplication RCCTE – Domain of application • Buildingsthat RCCTE applies to:

  37. RCCTE – Indoor & Outdoor Conditions RCCTE - Outdoor conditions Reference Indoor conditions • 20ºC in heating season • 25ºC and 50% relative humidity in the cooling season • Consumption of 40 liters of water at 60ºC/occupant . day Reference Outdoor conditions: • Portugal is divided in winter and summer climatic zones

  38. RCCTE – Outdoor Conditions RCCTE - Outdoor conditions Reference Outdoor conditions:

  39. RCCTE – Outdoor Conditions Climate • HeatingDegree-days are: • Where: • Tb is the desired indoor temperature (20ºC) • Tj is the temperature outside the hours j • The Degree-days are calculated for an entire year • For example, to Lisbon, for Tb = 20 º C, heating degree days are 1190 º C.day. Knowing the heating season is 6 months (180 days), the average daily GD (GDI) will be 6.6 º C.

  40. HeatingDegreeDays – a comparison

  41. RCCTE – Outdoor Conditions Climate • Outdoor projecttemperature • The outside project temperature is calculated on a cumulative probability of occurrence of 99%, 97.5%, 95% and 90%. • A cumulative probability of occurrence of 99% means that in summer the temperature indicated is exceeded only in probabilistic terms, 1% of the time, ie, 30 hours per year (e.g. Lisbon).

  42. Nominal Annual Needs of Useful Energy for Heating Nic Nic≤Ni Ni Thecorrespondingmaximumpermissible Nominal Annual Needs of Useful Energy for Cooling Nvc Nvc≤Nv Nv Thecorrespondingmaximumpermissible Nac Nominal Annual Energy needs for Domestic Hot Water Nac≤ Na Na Thecorrespondingmaximumpermissible Nominal Annual Energy needs for Primary Energy Ntc Ntc≤Nt Nt Thecorrespondingmaximumpermissible RCCTE – Fundamental thermalIndices RCCTE – Indices e parameters • Thethermalbehaviorofbuildingsischaracterizedusingthefollowing fundamental thermalindices:

  43. RCCTE – Additionalparameters RCCTE – Indices e parameters • Thethermalbehaviorofbuildingsischaracterizedusingtheparameters: more demanding for harsherwinters more demanding for harshersummers Additionalparameters Heattransfercoefficientsofwalls U Umax Thecorrespondingmaximumpermissible Heat Transfer Coefficients of Thermal Bridges 2 x Umax Solar factor offenestration (for windowsnotfacing NE-NW witharea > 5%) Fs Fsmax Thecorrespondingmaximumpermissible

  44. RCCTE – Fundamental thermalIndices: Heating Heating Heating: Maximum Allowable Needs (Ni) [kWh / (m2.year)] FF ≤ 0.5 :: Ni = 4,5 + 0,0395 GD 0,5 < FF ≤ 1 :: Ni = 4,5 + (0,021+ 0,037FF) GD 1 < FF ≤ 1,5 :: Ni = [4,5 +(0,021+ 0,037FF) GD] (1,2 – 0,2 FF) FF > 1,5 :: Ni = 4,05 + 0,06885 GD Form factor: FF = ( (Aext) +  ( Aint))/V GD :: Degreeday (ºC * day) more demanding for smaller FF Nic < Ni Heating: Nominal Needs (Nic) [kWh / (m2.year)] Nic= (Qt + Qv – Qgu) / Ap Qt = 0.024 x GD x  (A x U) Qv = 0,024 (0,34 x R x Ap x Pd) x GD to keeptheTint = 20ºC duringtheheatingseason Qt: heat loss by conduction & convection through the surrounding Qv: heat losses resulting from air exchange Qgu: solar gain and internal load

  45. Current average residential heating energy use (Harvey, 2010) • 60-100 kWh/m2/yr for new residential buildings in Switzerland and Germany • 220 kWh/m2/yr average of existing buildings in Germany • 250-400 kWh/m2/yr for existing buildings in central and eastern Europe • For Lisbon the maximum heating allowable needs are: • Passive house standard: 15 kWh/m2/yr

  46. RCCTE – Fundamental thermalIndices: Cooling Cooling Cooling: Maximum Allowable Needs (Nv) [kWh/(m2.year)] V1 (North) : Nv = 16 V1 (South) : Nv = 22 V2 (North) : Nv = 18 V2 (South) : Nv = 32 V3 (North) : Nv = 26 V3 (South) : Nv = 32 Açores : Nv = 21 Madeira : Nv = 23 Cooling: Nominal Needs (Nvc) [kWh / (m2.year)] Nvc = Qg * (1 - ) / Ap (kWh/m2year) Qg : Total gross load (internal + walls + solar + air renewal) : Load Factor Nvc < Nv to keeptheTint = 25ºC duringthecoolingseason

  47. RCCTE – Fundamental thermalIndices: Hot Water DomesticHotWater Domestic Hot Water: Maximum Allowable Needs (Na) [kWh / (m2.year)] Na= 0,081 MAQSnd/Ap MAQS : Reference consumption (40 liters per occupant) nd : Reference n. of days with DHW (residential:365) N. of occupants: T0=2; TN=n+1 1 m2 solar panel collector per occupant or 50% of available area if solar exposition is adequate Domestic Hot Water: Nominal Needs (Nac) [kWh / (m2.year)] Nac = (Qa/ηa – Esolar – Eren)/Ap Qa: Conventional useful energy requirements ηa: Efficiency of the conventional systems ESolar: Contribution of solar thermal panels for DHW Eren: Contribution to other renewable for DHW Qa : (MAQS * 4187 * T * nd) / (3 600 000) (kWh/year) Maqs = 40 l /occupant . Day*nº occupants T : 45º (15ºc  60ºc) Nac < Na

  48. RCCTE – Fundamental thermalIndices: PrimaryEnergy Primaryenergy Primary energy: Maximum Allowable Needs (Nt) [kgep/(m2.year)] Nt= 0,9 (0,01Ni + 0,01 Nv + 0,15 Na) Primary energy : Nominal Needs (Ntc) [kgep/(m2.year)] Ntc= 0,1 (Nic/ηi)Fpui + 0,1 (Nvc/ηv)Fpuv + NacFpua Fpu : Conversion factor from final energy to primary energy Electricity: Fpu = 0.290 kgep / kWh Fuels: Fpu = 0.086 kgep / kWh In the absence of more precise data consider, eg: Electrical resistance = 1 Boiler fuel gas = 0.87 Heat Pump = 3 (cooling) and 4 (heating) Ntc < Nt

  49. Energy Performance Certificate Energylabel • EnergyLabelling: R = Ntc / Nt R A A+ Newbuildings (licensedafter 2006) B- B 1 C D 2 Oldbuildings E F 3 G

  50. RCESE - Aims RCCTE – Aim • General aims: • Methodology for computingenergyperformaceofbuildings • Set minimumenergy performance standards • ImplementEnergyCertificationofbuildings • Regular inspection of boilers and air conditioning in buildings • SpecificAims: • Limitation of annual energy needs for heating, cooling, and primary energy • Limitation of heat transfer coefficients • Limiting of solar factors • Maintenance of HVAC systems • Monitoring and energy audits

More Related