Post on 09-May-2015
description
Federation of European Heating, Ventilation and Air-conditioning Associations
nZEB Buildings: experiences and
case studies from Central and North
Europe
Jarek Kurnitski
SITRA
Jarek.Kurnitski@sitra.fi
REHVA – AICARR Seminar on
Zero Energy Buildings
Milan, 28 March 2012
© Sitra
nZEB buildings
• Many pilot projects across Europe which may be called as nZEB buildings
• Variation in the definitions and performance levels
• Primary energy (simulated) typically between 50-100 kWh/(m2 a) if all energy use included (plug loads/user electricity incl.)
• Some buildings with measured data
• Buildings may be extremely complicated which may have implications in operation and maintenance
• Simple and reliable solutions based on high performance components and careful system design another nZEB trend
28.3.2012 Jarek Kurnitski
© Sitra
nZEB case studies
• nZEB office buildings in France, Netherlands, Switzerland and Finland
• Reported in REHVA Journal (3/2011 and 2/2012)
28.3.2012 Jarek Kurnitski
© Sitra
nZEB case studies – presentation outline
• Two buildings in more detail
- One from Central Europe, another North Europe
- Some technical concepts similar – suit for both climate
- Some different – depending on climate
- Simulated and measured energy performance
- nZEB extra cost
• Some key technical concepts based on nother buildings
• Can common features of nZEB office buildings be identified?
• Performance specification recommendations for nZEB
28.3.2012 Jarek Kurnitski
Federation of European Heating, Ventilation and Air-conditioning Associations
System boundary – REHVA nZEB definition
• Electricity use of cooling, ventilation, lighting and appliances is 39.8 kWh/(m2 a)
• Solar electricity of 15.0 kWh/(m2 a) reduces the net delivered electricity to 24.8 kWh/(m2 a)
• Net delivered fuel energy (caloric value of delivered natural gas) is 4.2 kWh/(m2 a) and primary
energy is 66 kWh/(m2 a)
System boundary of delivered energy
3.8 heating
11.9 cooling
10.0 lighting
BUILDING TECHNICAL SYSTEMS
15.0 PV electricity,from which 6.0 used in the building and 9.0 exported
Fuel 4.2
Electricity 33.8
Solar and internal heat gains/loads
Heat exchange through the building envelope
NET ENERGY NEED (47.2 kWh/(m2 a))
DELIVERED ENERGYBoiler3.8/0.9 = 4.2
Free cooling 4.0/10 = 0.4 Compressor cooling 7.9/3.5 = 2.3
Lighting 10.0
Ventilation 5.6
Appliances 21.5
Primary energy: 4.2*1.0 + (33.8-9.0)*2.5 = 66 kWh/(m2 a)
EXPORTED ENERGY
System boundary of net delivered energy
Ne
t de
live
red
en
erg
y
Electricity 9.0
21.5 appliances
(Sum of electricity 39.8)
21,5
10
3,2
0,61,1
10,8
NET ENERGY NEED (47.2 kWh/(m2 a))
Appliances (users')Lighting
Space
heatingHeating of air in AHUCooling in room unitsCooling of air in AHU
© Sitra
Paris, Elithis Tower (Hernandez REHVA Journal 3/2011)
© Sitra
© Sitra
Key solutions
• Rounded shape (-10% envelope reduction) + external solar shading shield
• Mechanical balanced ventilation with heat recovery
• Room conditioning with chilled beams
• Night ventilative cooling with mechanical exhaust ventilation from atrium
• Adiabatic + compressor cooling
• Large windows for max daylight, 2 W/m2 installed lighting power + task lighting, occupancy and daylight control
28.3.2012 Jarek Kurnitski
© Sitra
Mechanical ventilation + ventilative cooling
28.3.2012 Jarek Kurnitski
Three operation modes:
1. In the heating season the heat recovery ventilation, i.e. air handling units are operated.
2. Ventilative cooling: boost with façade intakes and low pressure atrium exhaust fans. Used in midseasons, when air handling units are operated together with atrium low pressure exhaust fans.
3. Night time ventilative cooling. Air handling units are stopped and only atrium low pressure fans are operated.
Façade intake
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Simulated and measured energy performance
• Office appliances are the major component in the energy balance…
28.3.2012 Jarek Kurnitski
© Sitra
Helsinki, Environmental Centre Ympäristötalo (Kurnitski REHVA Journal 2/2012)
© Sitra
General data
• Gross floor area 6791 m2
• Construction cost:
- 16.5 M€ (2430 €/m2)
• nZEB extra cost:
- 0.5-0.7 M€
- 3-4% of construction cost
28.3.2012 Jarek Kurnitski
© Sitra
Key solutions
• Compact massing
• Window to wall ratio 23 %
• South facing double facade with integrated PV (60 kW/570 m2 providing 17% of electricity use)
• District heating
• Air conditioning with balanced ventilation, heat recovery and chilled beams
• Cooling is 100% free cooling from boreholes: - 25 boreholes each 250 m depth
- 15/20C cooling water dimensioning for AHUs and chilled beams
28.3.2012 Jarek Kurnitski
© Sitra
Key solutions • Large mechanical rooms on the top floor and low pressure ductwork
• Specific fan power of main AHUs 1.4…1.6 kW/(m3/s)
• Heat recovery (wheels) temperature ratio 78…80 %
28.3.2012 Jarek Kurnitski
© Sitra
Integrated ventilation and AC with free cooling
• CAV for cellular and open plan offices, DCV for other rooms
• Active chilled beams in offices and passive chilled beams for other rooms for 24 h cooling (max cooling need 40 W/m2)
Air handling unit
Chilled beam
ME TE
TE
TE
TC
TC
TC
TE
a)
Supply
Return
District heat substation
a)
Cooling water from boreholes
Thermostat
Room
controller
Supply
Return
Room
28.3.2012 Jarek Kurnitski
© Sitra
Heat recovery from toilets – no separated exhausts
• Separated exhaust fans replaced with a small 0.5 m³/s air handling unit with rotary heat exchanger
• Supply air to toilets, heat recovery of 80%
28.3.2012 Jarek Kurnitski
© Sitra
Room conditioning and lighting
• Active chilled beams (CAV) in offices
• Lighting fittings of T5 fluorescent lamps with 7 W/m² installed power.
• Daylight, occupancy and time control is used in larger rooms, and occupancy and time control in cellular offices
28.3.2012 Jarek Kurnitski
© Sitra
Energy performance (simulated)
Major differences compared to Central Europe:
• much more heating (almost by factor 10)
• only slightly less cooling
• more lighting electricity
28.3.2012 Jarek Kurnitski
Net energy Delivered Energy Primary
need energy carrier energy
kWh/(m2 a) kWh/(m2 a) factor, - kWh/(m2 a)
Space and ventilation heating 26,6 32,2 0,7 22,6
Hot water heating 4,7 6,1 0,7 4,3
Cooling 10,6 0,3 1,7 0,5
Fans and pumps 9,4 9,4 1,7 16,0
Lighting 12,5 12,5 1,7 21,3
Appliances (plug loads) 19,3 19,3 1,7 32,7
PV -7,1 1,7 -12,0
Total 83 73 85
© Sitra
Simple or complex ventilation systems?
• Hybrid systems tend to be highly complicated (many actuators + complicated control) or are to be controlled by user – simulations provide often optimistic results compared to real operation
• Mechanical systems centralized (as in two case studies) or decentralized
• Centralized systems may be complex or not
28.3.2012 Jarek Kurnitski
© Sitra
Example of decentralized ventilation (Achermann, IUCN building, REHVA J 3/2011)
28.3.2012 Jarek Kurnitski
• Air intakes from facade, a filter unit, a fan and a heating/cooling coil
• CO2 sensor located at the exhaust damper integrated into a panel mounted on the ceiling
• No supply air ductwork
© Sitra
Constant pressure nZEB compliant simple ventilation
(Gräslund REHVA Journal 3/2011)
• 1-2 step larger ducts and AHUs
• No need for silencers and most of dampers
28.3.2012 Jarek Kurnitski
Federation of European Heating, Ventilation and Air-conditioning Associations
nZEB solutions: Natural lighting and solar shading, (Scartezzini and Lamy REHVA AM 2011)
3.5 W/m2 installed lighting power achieved!
Federation of European Heating, Ventilation and Air-conditioning Associations
nZEB solutions: Solar fired absorption chiller (Virta et al. REHVA GB 16 HVAC in sustainable office buildings)
• An example of a free cooling solution – many possible solutions
• The solar fired absorption chiller operates with hot water from
the roof mounted concentrating solar collector and the wall
mounted coil solar collectors
© Sitra
nZEB case studies: common solutions
• nZEB = demand reduction + effective systems + on site renewables
• Energy sources used: heat pumps, DH, bio-CHP, solar PV and thermal
• Heat recovery ventilation, often demand controlled, by centralized or decentralized systems sometimes combined with natural stack effect ventilation for ventilative cooling purposes
• Free cooling solutions combined with mechanical cooling via boreholes, water to water HP, evaporative or ventilative cooling etc.
• Optimized building envelope and effective external solar protection
• Utilization of natural light + effective demand controlled lighting
• High efficiency heat recovery and low specific fan power, CO2, presence and temperature control typical in nZEB
• Water based distribution systems and VRV heat pumps
• Utilization of thermal mass and other passive measures
• Office appliances have become major component in energy balance…
28.3.2012 Jarek Kurnitski
© Sitra
Key performance specification for nZEB (Virta et al. REHVA GB 16 HVAC in sustainable office buildings)
• Some indicative values for key low and nZEB energy design criteria in cold and temperate climates
28.3.2012 Jarek Kurnitski
Unit Low energy Nearly zero energy
SFP of air handling unit kW/m3/s < 2.0 < 1.5
Heat recovery efficiency % > 60 > 80
Demand controlled ventilation meeting rooms all spaces
Installed lighting power W/m2 < 10 < 5
Lighting control time, daylight time, daylight, occupancy
U-value of window W/K,m2 < 1.2 < 1.0
g-value of window < 0.7 adaptable (seasons)
Solar shading yes automated
Infiltration (q50) m3/h,m2 < 1.5 < 0.6
Share of renewable energy % > 10 >20
© Sitra
Central Europe vs. North Europe
• Large windows for max daylight to save lighting electricity
• Moderate insulation (Uwindow=1.1 , Uwall=0.30)
• More cooling need than heating need
• External solar shading
• “Glass” buildings with external shading possible
• Free cooling combined with compressor cooling or solar cooling
• Water based distribution system for cooling (or VRV)
• Heat recovery ventilation
• Demand controlled ventilation and lighting
• PV panels
• Small windows for lowest acceptable average daylight factor
• Highly insulated envelope (Uwindow =0.6…0.8, Uwall=0,15)
• Slightly less cooling but a lot of heating
• External shading for low solar angle
• Double façade to be used for “glass” buildings
• 100% free cooling possible with borehole water
• Water based distribution systems for heating and cooling (or VRV)
• Heat recovery ventilation
• Demand controlled ventilation and lighting
• PV panels
28.3.2012 Jarek Kurnitski
© Sitra
Experience from nZEB design process
• Energy simulations needed in very early stage to compare massing alternatives (starting from scoping)
• Reserving enough space for mechanical rooms and risers – 1-2 step larger AHUs and ductwork – this space may be difficult to find in a later stage
• Simulations of a typical floor often enough for decision making of basic solutions (concept stage)
• Facades to be optimized (concept stage) for a relevant combination of daylight, solar protection cooling and heating needs
• To achieve targets, careful verification and commissioning needed
• Sometimes official monthly based calculated methods may provide too optimistic results not achieved in practice
28.3.2012 Jarek Kurnitski