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Energy in Buildings Prof. Tânia Sousa

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1 Energy in Buildings Prof. Tânia Sousa taniasousa@ist.utl.pt
Energy Management: 2014/2015 Energy in Buildings Prof. Tânia Sousa

2 Energy Consumption in Buildings
Buildings account for 31% of global final energy consumption (20 to 40%) Energy Services? 66.96GJ 34.70GJ 16.45GJ 1MWh=3.6GJ

3 Energy Consumption in Buildings
Buildings account for 31% of global final energy consumption (20 to 40%) Energy use in buildings: thermal confort, refrigeration, hygiene, nutrition, illumination, etc 66.96GJ 34.70GJ 16.45GJ 1MWh=3.6GJ

4 Energy Consumption in Buildings
Final Energy use in buildings by fuel in 2007 in EJ Differences? Residential Commercial & Public

5 Energy Consumption in Buildings
Final Energy use in buildings by fuel in 2007 in EJ Combustible and renewables is the most important fuel in residential buildings while electricity dominates comercial buildings Residential Commercial & Public

6 Energy Consumption in Buildings
What about Portugal? In 2007 the final consumption of services + domestic sector represented 29% of the final energy consumption In 2007 the final consumption per capita was GJ which is 61.5% of the EU-27 Electricity is 49% of the final energy used by buildings (68% in comercial and 36% in residential)

7 Energy Consumption in Buildings
What about Portugal? In 2007 the final consumption of services + domestic sector represented 29% of the final energy consumption In 2007 the final consumption per capita was GJ which is 61.5% of the EU-27 Electricity is 49% of the final energy used by buildings (68% in comercial and 36% in residential) Do you think that the fraction of primary energy would be higher or lower? Electricity is 22% of total final energy

8 Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010): Reduce heating and cooling loads through a high-performance envelope

9 Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010): Reduce heating and cooling loads through a high-performance envelope Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight

10 Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010): Reduce heating and cooling loads through a high-performance envelope Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight Use the most efficient mechanical equipment to meet the remaining loads

11 Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010): Reduce heating and cooling loads through a high-performance envelope Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight Use the most efficient mechanical equipment to meet the remaining loads Ensure that individual energy-using devices are as efficient as possible and properly sized Efficiency label Annual power consumption (kWh/year)

12 Energy Consumption in Buildings
How much energy reduction can we achieve? Passive house standard: heating  15kWh/m2 per year cooling  15 kWh/m2 per year TPE  120 kWh/m2 per year n50 ≤ 0.6 / hour

13 Energy Consumption in Buildings
How much energy reduction can we achieve? Triple-glazed windows with internal venetian blinds & mechanical ventilation with 82% heat recovery

14 Energy Consumption in Buildings
How much energy reduction can we achieve? Heating needs decreased from 220 kWh/m2/year to 30 kWh/m2/year Triple-glazed windows with internal venetian blinds & mechanical ventilation with 82% heat recovery

15 Energy Consumption in Buildings
How much energy reduction can we achieve?

16 Energy Consumption in Buildings
How much does it cost?

17 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement Insulation levels control the heat flow by conduction & convection through the exterior and the interior

18 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement Insulation levels control the heat flow by conduction & convection through the exterior and the interior

19 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement Insulation levels control the heat flow by conduction & convection through the exterior and the interior U value (W/m2/K), the heat transfer coefficient, is equal to the heat flow per unit area and per degree of inside to outside temperature difference The U value of a layer of insulation depends on its thickness l and type of material (conductivity – C)

20 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement The most highly insulated houses have a heat transfer coefficient of U= W/m2/K Blown-in cellulose insulation (fills the gaps) Foam insulation Vaccum insulation panels Cork W/m/K

21 Evolution for the heat transfer coefficients in new buildings in Portugal
The most highly insulated houses have a heat transfer coefficient of U= W/m2/K

22 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the insulation levels of windows Windows offer substantially less resistance to the loss of heat than insulated walls Single glazed windows have a typical U-value of 5W/m2/K which can be reduced to to 2.5 and 1.65W/m2/K with double and triple glazing because of the additional layers of air The U-value of 2.5W/m2/K of double glazed windows can be reduced to 2.4W/m2/K and 2.3W/m2/K with Argon and krypton Double and triple glazing vaccum windows can reduce the U value to 1.2 and 0.2W/m2/K

23 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the gain/loss energy by radiation Windows permit solar energy to enter and loss of infrared radiation The solar heat gain coefficient, SHGC, is the fraction of solar radiation inicident on a window that passes through the window Low emissivity coatings reduce the absorption of long-wave radiation, i.e., they can reduce loss of heat by infrared radiation in winter

24 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage The net heat flow due to an air exchange at rate r is:

25 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage The internal energy change due to an air exchange at rate r is: The stack effect promotes air leakage Warm air is lighter Stack effect can account for up to 40% of heating requirements on cold climates The wind effect

26 Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage Careful application of a continuous air barrier can reduces rates of air leakage by a factor of 5 to 10 compared to standard practice (enforcement of careful workmanship during construction) Buildings with very low air leakage require mechanical ventilation (95% of the available heat in the warm exhaust air can be transfered to the incoming cold air) to keep indoor air quality

27 Energy Balance in Open Systems
Heat Exchangers: Transfer energy between fluids at different temperatures Nos três acetatos seguintes coloquei bonecos para poderes explicar melhor as leis da ternodinâmica Counter-flow Heat exchanger

28 Buildings – The role of shape, form, orientation and glazed %
Building shape & form Have significant impacts on heating and cooling loads and daylight because of the relation between surface area and volume Which one minimizes heat transfer by conduction and convection?

29 Buildings – The role of shape, form, orientation and glazed %
Building orientation For rectangular buildings the optimal orientation is with the long axis facing south Why?

30 Buildings – The role of shape, form, orientation and glazed %
Glazing fractions High glazing fractions increase energy requirements for heating and cooling There is little additional daylighting benefit once the glazed fraction increases beyond 30-50% of the total façade area

31 Buildings – The role of house size
The living area per family member increased by a factor of 3 between 1950 and 2000 in the US

32 Buildings –Passive (almost) solar heating, ventilation & cooling
Evaporative Cooling:

33 Buildings –Passive (almost) solar heating, ventilation & cooling
Evaporative Cooling:

34 Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling: Earth Pipe cooling

35 Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling: Large Atria

36 Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling:

37 Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling: Wind catcher

38 Buildings – Passive (almost) solar heating, ventilation & cooling
Passive Solar Heating & Lighting Shading Light tubes

39 Buildings – Passive (almost) solar heating, ventilation & cooling
Passive Solar Heating & Lighting Trombe Wall

40

41 Buildings: Mechanical Equipment
In evaluating the energy efficiency of Mechanical Equipment the overall efficiency from primary to useful energy should be taken into account This is particularly important in the case of using Mechanical Equipments that use electricity (produced from fossil fuels)

42 Buildings: Mechanical Equipment for heating
Furnaces heat air and 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)

43 Buildings: Mechanical Equipment for heating & cooling
Electrical-resistance heating Overall efficiency can be quite low (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

44 Buildings: Mechanical Equipment for cooling
Chillers Produce cold water which is circulated through the building Electric Chillers: use electricity, COP = (larger units have a higher COP) Absorption chillers: use heat (can be waste heat from cogeneration) , COP =

45 Buildings: HVAC Systems
Ventilate and heat or cool big buildings All air systems: air at a sufficient low (high) T and in sufficient volumes is circulated through the building to remove (add) heat loads CAV: constant air volumes VAV: variable air volumes Air that is circulated in the supply ducts may be taken entirely from the outside and exhausted to the outside by the return ducts or a portion of the return air may be mixed with fresh air Incoming air needs to be cooled and dehumidified in summer and heated and (sometimes) humidified in winter Restrict air flow to ventilation needs and use additional systems for additional heating/cooling Heat exchangers that transfer heat between outgoing and incoming air flows

46 Buildings: Mechanical Equipment for water heating
Electrical and natural gas heaters Efficiency of natural gas heaters is 76-85% Efficiency of oil heaters is 75-83% There is heat loss from storage tanks Point-of-use tankless heaters have losses associated with the pilot light There are systems that recover heat from the warm wastewater with % efficiencies

47 European Directives European Directives on the Energy Performance of Buildings Directive 2002/91/EC of the European Parliament and Council (on the energy performance of buildings): This was implemented by the Portuguese Legislation RCCTE and RCESE Directive 2010/31/EU of the European Parliament and Council (on the energy performance of buildings) This is implemented by the Portuguese Legislation DL 118/2013

48 Directive 2010/31/EU: Aims Reduction of energy consumption
Use of energy from renewable sources Reduce greenhouse gas emissions Reduce energy dependence Promote security of energy supplies Promote technological developments Create opportunities for employment & regional development

49 Directive 2010/31/EU: Aims Reduction of energy consumption
Use of energy from renewable sources Reduce greenhouse gas emissions Reduce energy dependence Promote security of energy supplies Promote technological developments Create opportunities for employment & regional development Links with aims of SGCIE?

50 Directive 2010/31/EU: Principles
The establishment of a common methodology to compute Energy Performace including thermal characteristics, heating and air conditioning instalations, renewable energies, passive heating and cooling, shading, natural light and design

51 Directive 2010/31/EU: Principles
Set Minimum Energy Performance Requirements Requirements should take into account climatic and local conditions and cost-effectiveness

52 Directive 2010/31/EU: Principles
Energy Performance Requirements should be applied to new buildings & buildings going through major renovations

53 Directive 2010/31/EU: Principles
Set System Requirements for: energy performance, appropriate dimensioning, control and adjustment for Technical Building Systems in existing and new buildings

54 Directive 2010/31/EU: Principles
Increase the number of nearly zero energy buildings

55 https://www.youtube.com/watch?v=pQFJr5E7_R0

56 Directive 2010/31/EU: Principles
Establish a system of Energy performace certificates. Energy Performance certificates must be issued for constructed, sold or rented to new tenants Buildings occupied by public authorities should set na example (ECO.AP in 300 public buildings in Portugal)

57 Directive 2010/31/EU: Principles
Regular maintenance of air conditioning and heating systems Independent experts

58 Implementation of the directives
Directive 2002/91/EC was implemented with: Directive 2010/31/EU was implemented with: DL 118/2013 (SCE, REH e RECS) 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).

59 Legislative Framework
Decreto-Lei n.º 118/2013 SCE – Buildings Energy Certificate System REH – Residential Buildings Energy Performance Regulation RECS – Commerce and Services Buildings Energy Performance Regulation Lei n.º 58/2013 Defines rules for SCE technicians Legislative framework is complemented by: 5 portarias 10 despachos Despachos 15793-C/2013 Pre-certificates and Certificates templates 15793-D/2013 Conversion factors 15793-E/2013 Computation simplification rules 15793-F/2013 Climatic data 15793-G/2013 Testing and maintenance plan 15793-H/2013 Renewable energies 15793-I/2013 Energy demand calculation 15793-J/2013 Energy classification rules 15793-K/2013 Thermal parameters 15793-L/2013 Economic analysis methodology of energy efficiency measures Portarias 349-A/2013 Role of SCE managing entity 349-B/2013 Methodology and requirements to classify residential buildings’ energy performance (REH) 349-C/2013 Permitting procedures and usage authorization of urban buildings 349-D/2013 Methodology and requirements to classify commerce and service buildings’ energy performance (RECS) 353-A/2013 Indoor air quality 1/17/2014 Doctoral Program and Executive Master in Sustainable Energy Systems Energy Management – 4th Group Work

60 SCE – Domain of Application
RCCTE – Domain of application Buildings that SCE applies to: Edifícios ou fracções novos ou sujeitos a grande intervenção Edifícios área útil > 1000m2 ou > 500m2 Edifícios ou fracções a partir do momento da sua venda 60

61 SCE – Fiscalização e Gestão
Obrigações Proprietários

62 SCE – Edifícios ZEB

63 REH Objectivos: Requisitos mínimos para edifícios de habitação novos ou sujeitos a grandes alterações Metodologia de caracterização do desempenho energético em condições nominais Metodologia de desempenho dos sistemas técnicos

64 REH and RECS RCCTE - Outdoor conditions Reference Indoor conditions
I3 (higher heating needs) and V3 (higher colling needs) 18ºC in heating season 25ºC in the cooling season Consumption of 40 liters of water at T+35ºC/occupant . day Reference Outdoor conditions: Portugal is divided in winter and summer climatic zones 64

65 REH and RECS RCCTE - Outdoor conditions
Reference Winter Outdoor conditions: 65

66 Heating Degree Days Climate Heating Degree-days are: Where:
Tb is the desired indoor temperature (18ºC) Tj is the temperature outside the hours j The Degree-days are calculated for an entire year For example, to Lisbon, for Tb = 18 º C, heating degree days are 1071 º C. day. Knowing the heating season is 5.3 months (160 days), the average daily GD (GDI) will be 6.7 º C. 66

67 Heating Degree Days – a comparison

68 REH and RECS RCCTE - Outdoor conditions
Reference Summer Outdoor conditions: 68

69 REH – Minimum requirements
RCCTE – Indices e parameters Heat transfer coefficient: Factores solares more demanding for harsher winters U Heat transfer coefficients of walls Umax The corresponding maximum permissible more demanding for harsher summers Solar factor of fenestration (for windows not facing NE-NW with area > 5%) Fs Fsmax The corresponding maximum permissible 69

70 REH – Thermal Behaviour
RCCTE – Indices e parameters Annual useful energy needs for cooling and heating in new buildings: Annual total primary energy in new buildings: Nic Nominal Annual Needs of Useful Energy for Heating Ni The corresponding maximum permissible Nic ≤ Ni Nvc Nominal Annual Needs of Useful Energy for Cooling Nv The corresponding maximum permissible Nvc ≤ Nv 70

71 REH - Heating Heating Nic < Ni
Heating: Maximum Useful Nominal Needs (Ni) [kWh / (m2.year)] Nic < Ni Heating: Useful Nominal Needs (Nic) [kWh / (m2.year)] 71

72 REH - Heating Heating Nic < Ni Corrected if there is heat recovery
Heating: Maximum Useful Nominal Needs (Ni) [kWh / (m2.year)] Nic < Ni Heating: Useful Nominal Needs (Nic) [kWh / (m2.year)] Nic = (Qtr,i + Qve,i – Qgu,i) / Ap Qt = x GD x  (A x U) Qv = 0,024 (0,34 x R x Ap x Pd) x GD Qt: heat loss by conduction & convection through the surrounding Qv: heat losses resulting from air exchange Qgu: solar gain and internal load Corrected if there is heat recovery 72

73 Current average residential heating energy use (Harvey, 2010)
kWh/m2/yr for new residential buildings in Switzerland and Germany 220 kWh/m2/yr average of existing buildings in Germany kWh/m2/yr for existing buildings in central and eastern Europe Passive house standard: 15 kWh/m2/yr

74 REH: Cooling Cooling Nvc < Nv
Cooling: Maximum Useful Nominal Needs (Nv) [kWh/(m2.year)] Nvc < Nv Cooling: Useful Nominal Needs (Nvc) [kWh / (m2.year)] Nvc = Qg * (1 - ) / Ap (kWh/m2year) Qg : Total gross load (internal + walls + solar + air renewal)  : Load Factor 74

75 REH: Total Primary Energy
Cooling TPE: Maximum Nominal Needs (Nt) [kgep/(m2.year)] Ntc < Nt TPE: Nominal Needs (Nvc) (Ntc) [kgep/(m2.year)] 75

76 REH: Conversion to Primary Energy
Comparação com SGCIE - 1MWh needs toe?

77 REH – Equipment Energy Efficieny
Os equipamentos de aquecimento e arrefecimento ambiente e de aquecimento de águas devem cumprir requisitos de eficiência A instalação de equipamento solar térmico para AQS (ou de outras renováveis) é obrigatória desde que a exposição solar seja adequada

78 REH – Thermal Behaviour
RCCTE – Indices e parameters Valor mínimo de renovação de ar de 0.4 por hora 78

79 Energy Performance Certificate
Energy label Energy Performance Certificate Energy Labelling: R = Ntc / Nt R A A+ New buildings B B 1 C D 2 E F 3 G 79

80 https://meocloud.pt/link/34d44317-19bb-467b-915e-78588c145383/Novo_CE_720p.mp4/


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