Net Zero Energy Buildings:The Next Wave of High Performance Buildings?

Charles J. Kibert, Ph.D., P.E.Powell Center for Construction & Environment

Rinker School of Building Construction, University of

Florida

To start…Net-Zero-Energy Buildings

1. Net Zero Energy Buildings,

on an annual basis, use no more energy than is provided by on-site renewable energy sources (US Department of Energy)

Three additional NZE Definitions

2. Net Zero Source Energy: A source ZEB produces at least as much energy as it uses in a year, when accounted for at the source. Source energy refers to the primary energy used to generate and deliver the energy to the site. To calculate a building’s total source energy, imported and exported energy is multiplied by the appropriate site-to-source conversion multipliers.

3. Net Zero Energy Costs: For zero cost, the amount of money the utility pays the building owner for the energy the building exports to the grid is at least equal to the amount the owner pays the utility for the energy services and energy used over the year.

4. Net Zero Energy Emissions: A net-zero emissions building produces at least as much emissions-free renewable energy as it uses from emissions-producing energy sources.

And possible new ones….

• Net Zero Total Energy: site energy or source energy plus embodied energy allocated over the building service life

• Net Zero Energy Plus: site or source energy plus the equivalent energy for transportation

And a confusing one….

• Near Net Zero Energy Buildings

• Energy Performance of Building Directive (EPBD) Revised April 2010

• In 2020, all new buildings, including offices and residences, will be required to operate annually as near zero energy buildings.

• Consequently, it will be necessary to achieve energy reduction for the more than 80% of the energy that is consumed in buildings for heating, cooling, hot water supply, ventilation, and lighting systems.

All NZE buildings?

ConsumptionKwh/m2/a

ProductionKwh/m2/a

100 200 300

100

200

300

A poor performer, not NZE, ample site

A good performer, not NZE except with site

Excellent performer, NZE, building roof only

Note: Two story office buildings, all are NZE by definition?

Why NZE is important

• Addresses the most important sector of energy consumption: buildings

• Reinforces passive design as a key element in building design

• Accelerates shift to renewable energy systems• Drives development of more efficient energy

technologies• Requires consideration of energy consumption

patterns and behavior• Induces a fuller consideration of planetary limitations,

faithful to true meaning of sustainability

NZE Buildings

Circumstantial

• Higher energy prices

• ARRA 2009 (Stimulus Package)

• Lower construction costs

• Climate change

Technical

• Improved PV, lighting, controls, HVAC , appliances

• Lower PV manufacturing costs

• ASHRAE and AIA involvement

• Commercial investment

Political

• Government incentives

• NZE as national policy

• State/local legislation

• The “smart grid” and decentralization

• RPS requirements

Forces driving NZE development

Making NZE feasible

• The building must be designed to consume the minimum energy possible.

• The occupants must be willing to conserve energy in the operation of the building (system scheduling, setpoints, maintenance, re-commissioning)

• A feedback and control system designed to inform occupants and assist in reducing energy consumption must be provided.

• Adequate site and building roof area must be available for installation of a renewable energy system, most often PV system.

300

200

150

100

50

250

0

266

231

133

105

73

Existing commercial buildings (2003 CBECS)

Models of Existing Building Stock (2007)

Energy efficient building

Target for ASHRAE 90.1-2010

CBF: 117Big Horn: 117Cambria: 108Oberlin: 88TTF: 85Zion: 79

Site Energy, Kwh/m2/yr

The trajectory of energy consumption for NZE feasibility in the U.S.

188 ASHRAE Advanced Energy Design Guide 30% reductions

ASHRAE Advanced Energy Design Guide 50% reductions

Lewis Center, Oberlin College, Ohio

Net Zero Energy Now?YES!!!

Net Zero Energy Then?NO!!!

MASDAR HeadquartersMASDAR City, Abu Dhabi

ADRIAN SMITH +GORDON GILL

World’s first “Net Positive Energy” mixed-use building 125,000 m2

Lowest energy consumer per SF (modern Class A office building)

World’s largest building – integrated PV

Largest solar thermal driven cooling and dehumidification system

Consume 70% less water

Solar potential in the U.S. is quite high…

Florida 5.5 kWh/m2/day = 2008 Kwh/m2/yr (Spain/N. Africa/S. PortugalMinnesota 4.0 kWh/m2/day = 1460 Kwh/m2/yr (N. Italy/S. France)

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1500 2000 2500 3000 3500

5%

10%

15%

20%

25%

30%

40%

50%

Solar Insolation Kwh/m2/yr

PV

Eff

icie

ncy

PV

Ou

tpu

t, K

wh

/m2

/yr

3

2

4

1

No. of Stories at 100 Kwh/m2

Insolation vs. Efficiency vs. Output

CIGS semiconductor printed on low-cost conductive metal foil,

Nanosolar Inc.

Glitter size crystalline silicon PV cells Sandia National Laboratory

Extending the Net Zero Concept (NZ8)

1. Energy

2. Water

3. Carbon

4. Emissions

5. Materials

6. Land

7. Air

8. Ecosystems

Conclusions

• A wide range of factors are converging to make NZE buildings a reality in the U.S.

• NZE refocuses the issue of building environmental impact on energy

• Technological developments are providing further impetus to implementing NZE building approaches

• Importantly, NZE forces consideration of the available energy available from nature.

• The NZ concept is extendable to other resources

And one announcement

• The iiSBE Net Zero Built Environment Working Group is being organized

• First meeting: Spring 2011

• Net Zero: energy, emissions, carbon, water, materials, land, air, ecology…etc

• Contact Charles Kibert for info

ckibert@ufl.edu

+1 352 273 1189