Zero Energy Buildings: Building a Sustainable Future Chen Jia, Shubham Duttagupta, Martin Heinrich, Ankit Khanna, Yeo Boon Khee MT 5009 Analyzing Hi-Technology Opportunities Class project
The definition of a Zero Energy Building
Def: ZEBs generate equal or more energy than they consume annually
ZEB is a 3 fold concept:
Local use of green energy sources (our focus: BIPV)
Energy efficiency: passive design and efficient technologies
Optimal grid connections
2010 US end-use emissions from fossil fuel combustion
Adapted from: U.S. Greenhouse Gas Inventory Report (US Environmental Protection Agency), 2012
Emis
sio
n in
Tg
(CO
2 e
q. )
A qualitative look at ZEB costs ZEB’s advantage over the lifecycle
Conventional
Cu
mu
lati
ve c
ost
s
Years
Regular buildings ZEBs Future ZEBs
High construction cost offset by low operating costs
Construction cost ZEBs higher than conventional buildings
Lowering initial and operating cost by improvements in ZEB technologies
(Cumulative cost = construction cost + operation costs)
ZEBs are energy efficient Technologies and design to reduce energy usage
Reduction of energy demand is central to the ZEB concept
Energy efficiency is attained through:
High efficiency HVAC
Energy-efficient artificial lighting
Passive solar design
Maximizing day lighting
BCA Academy building, Singapore
Photovoltaics: Technology and Integration
Rapid growth in PV market, average annual growth rate of 40%
Sources: International Energy Agency (IEA) 2008
World cumulative PV installation
Grid parity in Singapore
a scenario under the assumption of net metering
PV cost
Utility price
+5%/a
0%/a
-7%/a
-13%/a
Calendar year
Elec
tric
ity
cost
s/p
rice
s in
[S$
/kW
h]
0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00
2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
Source: Luther et. al., ICMAT, 2011
Source: S. Glunz, Fraunhofer ISE; Data Photon Magazine 2011
100%
80%
60%
40%
20%
0%
Other
a-Si ClS
CdTe
Ribbon c-Si
Multi c-Si
Mono c-Si
Currently, silicon dominates the PV market
Thin film materials (CIS, CdTe, etc.) growing slowly
Market shares of PV technologies
PV Technologies
Best efficient in lab using different technology Source:Multi-Junction Solar Cells, ICMAT Yamaguchi 2011
Thin film
Dye-Sensitized
Organic
PV materials replace conventional building materials
Integration
Addition to existing building (e.g. roof-top PV installation)
Replacing building envelopes (e.g. PV façade or window)
Aesthetically pleasing
Connecting to utility/grid
Building Integrated Photovoltaics (BIPV) Concept, key aspects
Source: Lux research, BIPV, 2010 transparent windows
facades
roofing
BIPV installation Split by application (worldwide estimation)
Vertical scaling for ZEBs Façade and window integration becomes more prominent
Modern ZEBs need to be several stories high
This would improve natural ventilation and allow more daylight
Trade-off: roof PV no longer sufficient for energy demand
Façade and window integration become more prominent
An artistic impression of the Pearl River Tower in China
Source: International Energy Agency, PV report, 2004
Learning curve of BIPV Experience for 20 years
Drivers:
Decrease in BIPV cost driven by reduced PV cost and increased efficiency
Special BIPV feed-in-tariffs
Architects and BIPV R&D Source: K.Sopian et al , ISESCO Science and Technology Vision - Volume 1, 2005
The need for grid connected ZEBs PV electricity output varies with time
Daytime surplus energy can be fed back to the grid
Grid connections are necessary
Daily electricity supply (PV) and demand, averaged over one year
Source: Data from the BCA academy building, Singapore’s first ZEB
Energy efficient technologies for buildings
Residential sector Commercial sector
Major usage: 1. Air conditioning/ Refrigerator 2. Lighting
Source: Office Building Energy Saving Potential in Singapore, Cui Qi, 2006; E2 Singapore, NEA, 2010
Air-conditioner
30%
Refrigerator 17%
Lighting 10%
Water Heater
9%
Fans 4%
Video Equipment
10%
Kitchen Appliance
6%
Washing 6%
Others 8% Air-
conditioning 52%
Lighting 12%
Ventilation 4%
Trans- portation
7%
Office Equipment &
Others 25%
Energy consumption in Singapore By end-use
Air-conditioning /Refrigerator Working principle
1. Compressor: Gas compression and heating
2. Condenser: Condensation of hot gas to liquid
3. Valve: sudden expansion of liquid => partly evaporation and cooling
4. Evaporator: Full evaporation of mist and cooling
Compressor Condenser
Evaporator
outside
inside
Valve
Possible improvements for AC Identified, selected technologies for AC with high potential
Source: Energy Savings Potential and R&D Opportunities for Commercial Building HVAC Systems, U.S. Department of Energy 2011
Air conditioning
Improvements for air-conditioning Example: Liquid desiccant
Source: Energy Savings Potential and R&D Opportunities for Commercial Building HVAC Systems, U.S. Department of Energy 2011
Singapore: Over cooling and reheating air to reduce humidity
Solution: Liquid desiccant (like silica gel, but liquid)
Liquid desiccant: High affinity for water, attracts moisture in conditioner
Regenerator heats liquid desiccant to release moisture
Outlook AC efficiency AC efficiency (Energy Efficiency Ratio, EER) projection
Source: Energy efficiency of air conditioners in developing countries …, OECD/IEA, 2007
Average efficiency of all AC unit for sale MEPS: minimum energy efficiency requirements, target set by Chinese government
Energy efficient lighting outlook Current and projected advances in lighting (section 8 by Prof. Funk)
Source: Solid State Lighting, U.S. Department of Energy (2010)
Light bulb
CFL LED
projection
In summary: • Recent advances in CFLs • Future advances in LEDs projected
Energy consumption of lighting will become less
Passive design
Thermal insulation Reducing overall HVAC usage
Insulation prevents heat transmission, therefore overall HVAC usage
Past 20 years: only incremental improvements in insulating material
Recently, aerogels explored as new insulating technology
Aerogels consist of network of bubbles, with very thin cell walls
Insulation prevents heat transmission into building (summer) and from buildings (winter)
Aerogels cost and performance Commercially available building insulation materials
Insulating Material Thermal conductance [W/m²·K]
Cost per ft3 (US$)
Polystrene Foam 0.20 8.04
Rock Wool 0.36 1.64
Fiber Glass 0.32 1.63
Cellulose 0.29 1.81
Pure Silica Aerogel 0.05 2500
Clay Polymer Aerogel (Aeroclay) 0.05 8
Source: Evacuated Panels Utilizing Clay-Polymer Aerogel Composites for Improved Housing Insulation, Dalton et. al., 2010
Aerogels commercially available and used mainly in clothing and for
scientific applications (because of higher costs)
New startup Aeroclay (2010) is commercializing cheap aerogels made
of clay; scale up from R&D to manufacturing underway
Aerogels cost and performance Improvements in performance of building insulation materials
Source: Vacuum promises a thinner future, A.Birch, 2009
Thickness of insulation reduces while thermal conductivity falls
Improvements in Aerogels Use of aerogels in many industries is driving improvements
Wide applications across various industries
Source: J. Non-Crystalline Solids, Schmidt et al, 1998
Aerogels for Building Insulation Potential Aerogel usage for Window insulation
Thermal transmittance for different insulations types of windows
Source: Aerogels Handbook, Springer, 2011
Insulation glass unit:
Clear Aerogel
Ther
mal
Co
nd
uct
ance
, U v
alu
e (
W/m
2K
)
Source: Solar Energy Vol. 73, No. 2, pp. 123–135, 2002)
Maximizing day lighting Using light ducts for lighting in offices
Solar chimney Solar assisted stack ventilation
Source: BCA academy building, Singapore’s first ZEB
Use of natural convection to supply fresh air:
Under PV panels on rooftop hot air accumulates
Hot air is rising in chimney (buoyance effect)
Rising air generates suction, removing old air in offices
New (fresh) air introduced from sidewalls
ZEB: State of the art and outlook
Case Study: BCA Academy, Singapore Singapore’s first ZEB (retrofitted to existing building)
Insulation
(1,2,3)
• Low-absorption glass
• Green walls/roofs
BIPV
(4,5,6)
• Meets annual energy demand
• PV on roof, facade, car park
• c-Si and thin film
Lighting
(7)
• LEDs, motion sensors (6)
• Light ducts, reflecting panels (maximising day lighting)
4
6
5
7 1
3
2
PV, closer look
Source: BCA Academy ZEB website, virtual tour
Roof PV
Thin film PV on car park shelter
Roof PV
Facade PV
Solar chimney
Passive design, closer look
Source: BCA Academy ZEB website, virtual tour
Green Roof
Green Walls
Insulation on glass
Sun shades with PV
Light duct Motion sensors
Reflecting panels
LED
454958 kWh
424830 kWh
879350 kWh
Cumulative energyproduction
Cumulative energyconsumption
Cumulative energyconsumption
Case Study: BCA Academy, Singapore Energy production, consumption and cost saving (Oct 09 – Jan 12)
ZEB, BCA Academy
Typical office of similar layout
Cost saving due to energy efficiency S$ 118,410
Cost saving due to onsite energy generation S$ 112,237
Source: BCA Academy ZEB website, Energy Production and Consumption, 2012
Customer needs The ZEB approach and drivers for improvement
Economy
• Approach: Upfront cost offset by low operating cost
• Drivers: Advances in energy generating/saving components
Comfort
• Approach: Energy efficient HVAC, smart lighting etc
• Drivers: reduction in cost, more widespread information
Functionality
• Approach: Smart design
• Drivers: Architectural expertise specific to ZEBs
Aesthetics
• Approach: Alternative building materials
• Drivers: Architectural expertise specific to ZEBs
ZEBs
Market prediction for ZEBs
Pike Research: ZEBs market $690 billion by 2020
Market share for:
Architecture, engineering and construction firms (“zero energy design”)
PV and other renewable energies
HVAC, lighting and others
Building materials
Source: Pike Research Report on ZEBs, 2011 and Green outlook, McGraw-Hill Construction, 2011
Analysis of US construction market
Thank you for your attention
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