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

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