the energy/comfort nexus · 2017-04-06 · demonstrated energy savings and comfort § field testing...
TRANSCRIPT
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Clif Bar Headquarters, Emeryville, CA. Zero Net Energy retrofit & winner of Living Building Award
MIT – Energy Initiatives Series
The Energy/Comfort Nexus: making buildings work for people and the planet
Gail BragerCenter for the Built EnvironmentUniversity of California, Berkeley
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Why energy ?
Cartoon by Joel Pett, USA Today, Dec 2009
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Why comfort?
Source: www.cartoonaday.com
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Why buildings?
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Trends - U.S. CO2 Emissions by Sector
Source: Energy Information Administration Statistics
Buildings are responsible for nearly ½ of CO2 emissions in the U.S.
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Energy use in buildings– a significant % goes to thermal conditioning
US DOE Quadrennial Technology Review, http://energy.gov/sites/prod/files/ReportOnTheFirstQTR.pdf
42.4%
38.0 %
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But doesn’t it cost a lot to reduce energy & greenhouse gases?
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Costs of Reducing Global Warming40
% of
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!
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Improved lighting and building envelopes!
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The Architecture 2030 ChallengeAll new buildings, developments, and major renovations shall be carbon-neutral by 2030.Tiered % reduction below average for that bldg type
http://architecture2030.org/2030_challenges/2030-challenge/
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Meeting the Architecture 2030 Challenge
http://architecture2030.org/2030_challenges/2030-challenge/
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Zero Net Energy Buildings (ZNE)Over a year …. The building generates
at least as much as it uses
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Zero Net Energy Buildings (ZNE)Over a year …. The building generates
at least as much as it usesThe Name GameNet zero energyNet zero site energyNet zero source energyNet zero energy emissionsNet zero energy costsZero net readyUltra-low energy (*)Zero net energy• Verified• Emerging
* similar to ZNE in energy use reduction, but haven’t invested in on-site renewables
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Zero Net Energy Buildings (ZNE)
P. Torcellini et al., Zero energy buildings: a critical look at the definition, www.nrel.gov/docs/fy06osti/39833.pdf
Definitions DescriptionsNet zero site energy building
Building produces as much energy as it consumes when measured on site
Net zero source energy building
Building produces the same amount of energy as the amount of source (primary) energy it consumes.
Net zero energy cost Cost of the energy added to the grid by the building is same as the cost of the energy consumed by it.
Net zero emission Net emission due to building energy consumption is zero.
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Zero Net Energy Buildings - Setting priorities
Source: Two Degrees, Chap 6, McGregor, Roberts & Cousins
• Mechanical systems• Electrical systems
Use renewables after you’ve done everything else!
• Shading• Daylighting• Climate-
response architecture
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Zero Net Energy Buildings – Setting priorities
Source: Two Degrees, Chap 6, McGregor, Roberts & Cousins
• Mechanical systems• Electrical systems
Use renewables after you’ve done everything else!
• Shading• Daylighting• Climate-
response architecture
Leaky bucket analogy
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Trends in Zero Net Energy Buildings
New Buildings Institute reports
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Trends in ZNE (& ultra-low energy) – EUI?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
ZNE are usually
20 EUI or less!!
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New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
Trends in ZNE (& ultra-low energy) – how many?
# ZNE: 60 à 160 à 332
more than doubledduring last 2-year periods
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Trends in ZNE (& ultra-low energy) – how many?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
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Trends in ZNE – where?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
Nearly all climate zones
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Trends in ZNE (& ultra-low energy) – where?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
Massachusetts in top 5 states of ZNE
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Trends in ZNE (& ultra-low energy) – how big?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
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Trends in ZNE – growth by size
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
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Trends in ZNE (& ultra-low energy) – who owns?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
2/3 are public buildings
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Trends in ZNE (& ultra-low energy) – what types?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
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Trends in ZNE (& ultra-low energy) – who owns?
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
2/3 are public buildings
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Trends in ZNE (& ultra-low energy)- new vs. existing
New Buildings Institute, Getting to zero status update, 2016, newbuildings.org
1/4 are renovations
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Trends in ZNE (& ultra-low energy) – HVAC type?
ASRHAE High Performance Magazine, Fall 2016
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New Buildings Institute © 2016
New Buildings Institute © 2016
SPACE CONDITIONING
CEILING FANS Radiant
• Ground Source Heat Pumps• Radiant Heating/Cooling &
Chilled Beams• Energy Recovery Systems – air
and water • Ventilation– Natural– Dedicated Outdoor Air Systems (DOAS)– Demand Control Ventilation (DCV)
Forced Air
CHILLED BEAMS
Passive Solutions 1st
then
HVAC
Trends in ZNE (& ultra-low energy) – HVAC type?
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The Energy/Comfort Nexus
Illustration by David Lehrer
Illustration by Viktor Koen
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Energy vs. comfort is a false dichotomyWe are overcooling buildings in summer, wasting energy and making people uncomfortable.
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Comfort zones (ASHRAE Standard 55)
In practice: 71 – 75ºF
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Energy savings with wider dead band
conventional
adaptivepersonal comfort systems
, CA
, FL
, MN
60 65 70 75 80 85
Temperature (°F)
Saving (significant!) energy with a wider dead bandWider dead band reduces HVAC energy 7-15% per ºCHow can we make people comfortable at the same time?
Hoyt, T., E. Arens, H. Zhang, 2105, “Extending air temperature setpoints.” Building and Environment
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Energy vs. Rent vs. People costs are 1:10:100
Source: Terrapin Bright Green 2012
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Indoor Environmental Quality (IEQ)
Thermal comfort Lighting / visual comfort
Indoor air quality Acoustics
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Are people comfortable in existing buildings?
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§ Standardized method for studying building performance from occupants’ point of view
§ Rich database for evaluation of new technologies §1000+ buildings§100,000+ responses
§ Uses§Commissioning §Diagnostics§Benchmarking§Research
CBE web-based occupant satisfaction surveys
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CBE occupant satisfaction survey, office buildings– > 50% are dissatisfied with temperature
§ Frontczak M, Schiavon S, et al. 2011. Indoor Air Journal
N = 53,000 occupants, 351 buildings
When Median < 0,> 50% are dissatisfied
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Paradigm shifts in the energy/comfort nexus
Artificial/active à Natural/passive/hybrid
Centralized à Personal control
Air à Water (radiant)
Thermal neutrality à Thermal delight
Packard Foundation. Source: EHDD
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meh yay!
Artificial / Active
Natural / Passive (& Hybrid)
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Adaptive comfort standardfor naturally ventilated buildings
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Adaptive comfort standardfor naturally ventilated buildings§ 21,000 observations (indoor climate & surveys)- 160 buildings- 4 continents- broad range of climate zones.
§ Separate analysis for :- centrally-controlled air-conditioned (HVAC) - naturally ventilated (NV)
§ Statistical models produced an adaptivecomfort standard for ASHRAE Std. 55
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Conventional vs. adaptive approaches
§ Conventional standards§ Based on laboratory studies
(Laboratory ¹ Real buildings)
§ One-size-fits all:Universally applied to all climates, cultures, and building types
§ Adaptive comfort theory§ Based on field data
§ 3 types of adaptation:- physiological- behavioral- psychological
§ Satisfaction influenced by expectations & context
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Selected results: field studies
Centrally-controlled HVAC bldgs Naturally ventilated bldgs
Lines are weighted linear regresssionsthrough the data points (not shown)
Predicted: Lab-based heat-balance modelObserved: Field-based adaptive model
deDear and Brager
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Adaptive Comfort Standard in ASHRAE Std. 55
14
16
18
20
22
24
26
28
30
32
5 10 15 20 25 30 35mean monthly outdoor air temperature (oC)
indoor operative temperature (oC)
80% acceptability limits
50 F 59 F 68 F 77 F 86 F 95 F
86.0 F
82.4 F
78.8 F
75.2 F
71.6 F
68.0 F
64.4 F
60.8 F
90% acceptability limits
Replaced ET* as climate index Also replaced monthly with running mean
Replaced optimum temperature with a range
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Mixed-mode buildings – a hybrid approach
§ Operable windows + mechanical cooling
§ Different configurations
Concurrent• same space• same time
Change-over• same space• different times
Zoned• different spaces• same time
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Comfort and energy performance with NV and MM
§ Adaptive comfort model developmentSimulation and field study studies identified appropriate comfort model for NV buildings
§ Occupant satisfaction in mixed-mode (MM) buildingsImproved thermal, air quality and overall satisfaction using occupant survey results
§ Window control signaling systemsInsights on design, occupants responses and behaviors from 16 buildings
§ Feasibility of MM buildings in CaliforniaComfort exceedance using low-energy cooling strategies (radiant + MM)
§ High-performance facade case studiesDocumenting performance, comfort and lessons learned
§ Comfort tool developmentCBE developed SolarCal calculator adopted by ASHRAE
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MM Climate Feasibility
Assess climatic feasibility using metrics of comfort and energy across CA’s 16 climate zones
3 basic systems:
– High energy baseline: Conventional forced air VAV system with chiller
– Low energy baseline: Natural ventilation with night flush
– Mixed-mode system: Radiant cooling with natural ventilation
1-9 Coastal10-13 Central14-16 Eastern
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Simulation: case study building
§ Simplified model§ 6 zones, 39 windows§ Designed for parametric studies
§ Case study building Kirsch Center at DeAnza College
§ Van der Ryn Architect
§ Air tight, low gains, well shaded§ Air flow network
§ Pressure coefficients calculated with Cp Generator§ Radiant floors
§ Cooling tower charges slab overnight (free running during the day)§ Autosized VAV system
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NV, MM & VAV: comparing performance
Natural Ventilation Only: Night Vent with day vent for Tout < 25C
Mixed-Mode, Radiant Slab w/ NV: Same as above with night cooling of slab via cooling tower
Sealed VAV: Reference case;; standard VAV with DX units
Hypothetical comparison (to explain graph)
(% occupant-hrs) (kBtu/sq.ft-yr)
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Mixed-mode: nutshell of our results
North Coast
Bay Area
Central Coast
South East
NV Only: Night Vent with day vent for Tout < 25C
MM: Rad Slab w/ NV: Same as above with night cooling of slab via cooling tower
Sealed VAV: Reference case;; standard VAV with DX units
01020304050607080910111213141516
Central Valley
Southern Coast
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Natural ventilation vs. Mixed mode% occupied hours above warm adaptive comfort limit(green is good)
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meh yay!
Centralized control
Personal control
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Personal comfort systems (PCS)
• “Task/ambient” approach has been widely adopted for lighting
• Paradigm shift:
• From space-based to person-based conditioning
• From using static indoor environmental parameters to dynamic, variable and occupant-selected modes
• Multi-year research using simulations, laboratory, and field studies
• Development and testing of numerous devices
Traditional mixing overhead system
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1st generation PCS: desktop fan & footwamer
Provides control and monitoring of:
§ User settings for fan and foot warmer
§ Ambient air temperature
§ Occupancy
Connection to internet via USB to computer to collect and send research data
Fan and control unit
Foot warmer
4W
average 30W
Optional user interface
occupancy sensing pressure plate
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2nd generation PCS: heated & cooled chair
Pasut,W., H. Zhang, E. Arens, Y. Zhai 2014, Energy efficient comfort with a heated/cooled chair, Proceedings of the 13thInternational Conference Indoor Air 2014, July 7 – 11.
Touchscreen Phone app
Resistance heating strips
Convectively cooled plenums
Battery -‐1 week typical use
Controller, Touchscreen,
Bluetooth & wireless
§ Low power use, max:• 14 W for heating • 3.6W for cooling
§ User controls for cooling and heating§ Saves energy by allowing wider HVAC
temperature setpoints§ Rechargeable battery§ WiFi and Bluetooth communication
with BMS§ Collects temp, humidity, occupancy &
usage data§ 50 built for
research
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Demonstrated energy savings and comfort
§ Field testing prototypes in multiple siteso Summer/wintero NV, VAV, radianto With and without PCS (chairs, fans, food
warmers, legwarmers)
§ Comfort:At 64-84ºF more than 90% of subjects were comfortable with the chair and a desk fan
§ Energy:Field tests have demonstrated energy savings of 60% with improved comfort
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How can technology improve our personal control and experience? Occupant-in-the-loop controls
Comfy on a mobile device
§ “Comfy” founded byformer UC Berkeley students (EECS, Architecture, CBE)
§ Occupants make comfort requests, with social functions for shared environments
§ Integrates with HVAC controls
§ Based on principles from “sMAP” building information framework
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Occupant control of HVAC
Heated/cooled PCS chairs
Occupants HVAC
sMAP
AHU control
Zone control
Selectively distribute chairs
• Critical zones
• Conflicting comfort needs
• Single zone, multiple rooms
Occupant-in-the-loop controls
(*) Simple Measurement and Actuation Profile (sMAP) software, developed at UC Berkeley EECS Dept, connects to bldg’s BACneet and allows rapid access and visualization of data from different sources
*
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meh yay!
Air Radiant
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Heat capacity of air vs. water
Source: Peter Rumsey
Heat Capacity of this much air
=
Heat Capacity of this much water
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Air vs radiant: decoupling of thermal & ventilation
Image credit: Caroline Karmann
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Air systems vs. Radiant systems
Air systems• Ventilation + space conditioning• Design to meet a single peak
cooling load value• Remove heat using convection
Radiant systems• Decoupled ventilation and
space conditioning• Allow pre-conditioning the
radiant layer• Remove heat using convection
+ radiation• à Traditional cooling load
calculations don’t account for complexities of radiant systems
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Radiant system types (high/low mass)
Images source: Caroline Karmann
Embedded Surface System (ESS)
Thermally Activated Building System (TABS)
Radiant Panels (RP)
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Cooling load differences: Laboratory tests
Feng Bauman Schiavon 2014 Experimental comparison Energy and Buildings
Concrete pavers in floor as the non-active massConstant heat gain applied in both settings, using thin electric resistance heating mat, loose mesh design to ceiling panels interact directly with with pavers belowConstant operative temperature maintained to represent equivalent comfort (and it is prescribed as the control temperature for radiant systems)For each, 12-hour tests:
– Heater on for 6 hours– Heater off for 6 hours
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Cooling load differences: Laboratory results• Radiant system has a higher cooling rate than the air system,
up to 18% higher during peak cooling load
• Lower floor temperatures in radiant system shows that more heat was removed compared to air system
Feng Bauman Schiavon 2014 Experimental comparison Energy and Buildings
Instantaneous cooling rateTemperature of concrete pavers in floor
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New/ongoing tests at LBNL’s FlexLab
SIDE-BY-SIDE COMPARISON OF COOLING RATESFOR RADIANT AND FORCED AIR SYSTEMS
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40°C
35
30
25
20
15
RADIANT COOLING (CEILING)OPERATIVE TEMP = 26°C
FORCED AIR COOLINGOPERATIVE TEMP = 26°C
Infrared comparison
J. WOOLLEY
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meh yay!
Thermal neutrality
Thermal delight
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Rich, variable, multi-sensory environments
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Experiential Monotony
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Source: www.terrapinbrightgreen.com
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www.terrapinbrightgreen.com
Benefits of Biophilic Design
• Psychological & physiological stress reduction
• Lowered blood pressure and heart rate
• Improved mental engagement / attentiveness
• Reduced attentional fatigue• Increased physical / mental
health• Shift to positive emotional states• Mental restoration, cognitive
function• Improved rates of healing• Entrainment of circadian rhythms• NO evidence of negative effects
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Winners: CBE Living Building Award
Occupant wellbeingHow can we reward GOOD buildings?
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Awarded for exceptional performance in terms of occupant satisfaction, resource efficiency, and overall design
Qualifying criteria § Scores for all survey categories
above 50th percentile§ Overall building score above 75th
percentileSelection§ Submission of design, operation,
and survey § Jury review
CBE Livable Buildings Awardsdesign + occupant experience + energy performanc
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www.cbe.berkeley.edu
Papers and publicationswww.escholarship.org/uc/cedr_cbe
Clif Bar Headquarters, Emeryville, CA. Zero Net Energy retrofit & winner of Living Building Award