Zero Carbon Building, Hong Kong, October 2015

Decarbonising High Rise Buildings: US experience

Godfried Augenbroe

Two main talking points

1. How to target ZCB (operational energy: ZEB)

2. Managing energy performance: challenges and risks

1. ZEB: definition and trends

http://energy.gov/sites/prod/files/2015/09/f26/bto_common_definition_zero_energy_buildings_093015.pdf

A new definition was needed to accommodate the collections of buildings where renewable energy resources were shared. Zero Energy Building (ZEB) An energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy. Zero Energy Campus An energy-efficient campus where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy. Zero Energy Portfolio An energy-efficient portfolio where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy. Zero Energy Community An energy-efficient community where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy. Delivered energy: Any type of energy that could be bought or sold for use as building energy , including electricity, steam, hot water or chilled water, natural gas, biogas, landfill gas, coal, coke, propane, petroleum and its derivatives, residual fuel oil, alcohol based fuels, wood, biomass and any other material consumed as fuel

Definitions

Site Boundary of Energy Transfer to Zero Energy Accounting

Scope

Example combined heat and power (CHP)

What if an owner cannot meet the ZEB requirement?

Use Renewable Energy Certificates (REC) Renewable Energy Certificate - Zero Energy Building (REC-ZEB) An energy-efficient building where, on a source energy basis, the actual annual delivered energy is less than or equal to the on-site renewable exported energy plus acquired Renewable Energy Certificates (RECs).

Trending in the US: Zero energy at the urban scale: Micro-grids Distributed generation with (grid scale) storage

US trend: Towards zero energy at the larger scale!

Rationale: Why invest in Local RE when investing elsewhere is more profitable

Urban energy modeling

The grid perspective: The problem is power (kW) not energy (kWh)

US trend: “energy efficiency is no longer efficient”

Problem: what is the marginal contribution of a single building? The utility answer: you pay based upon your last month peak power usage Demand Response: Open Automated Demand Response (OpenADR™), a standards for power demand management. Typically, OpenADR is used to communicate data and signals that turn off powered devices when electrical demand is high.

Power optimization Energy co-ops Urban energy network

Challenge: better models and risk analysis to increase confidence

Energy Efficiency: Total light/energy management Monochromatic windows Operable shading, blinds Light shelves Controlled ventilation

Intelligent HVAC control Distributed intelligence; occupancy analytics

Sensors: Occupancy, air quality, Humidity

HVAC monitoring&Cntrl

Heat recovery, PCM, Ice storage Heat storage components Heat pumps, Geothermal

BEMS: Integrated controls, real time modeling FDD, Predictive control

Renewable Energy (Shared)

2. The challenges of high performance buildings

Technology perspective

Source: ASHRAE Tall Buildings design guide

Challenge: find winners and losers through RoI assessment

Legacy of bad buildings

Retrofit challenges of large proportions, but investors reluctant

Design targets

• Minimization of solar energy gain through the façade/envelope • Use of daylight to minimize lighting, and reduction of lighting when levels rise

above the required level • Maximizing re-use of 60% or more of the building energy use • Minimize fan and pump energy use, possibly by floor-by-floor service • Utilization of wind-driven ventilation and cooling, as well as passive

technologies. • Low-energy terminal devices on occupied floors • Better comfort control: chilled beam, VRF, personal control • Allowing indoor temperature and humidity to fluctuate within comfort limits Generation systems for ZEB (off-setting emissions and water use): • Fuel cells (Bloom boxes) • Micro turbine • CCHP (microturbine-adsorption chiller, waste heat, electricity)

Increasing attention: Water consumption (but water credits are lagging)*

*James, Jean-Ann, PhD dissertation Georgia Tech, 2015

Tall building modeling challenges

Every floor deals with different micro climate conditions

V(z) Θ(z) Qsolar (z) Turbulence (z) Urban Heat Island

Example: Wind rose at higher levels

Stack effect

Not a big issue in hot climates

Natural ventilation: a big issue, even in hot climates

Reverse stack effect

The thermal comfort conundrum

Thermal Comfort for all is an elusive target

Adaptive comfort models are reliable predictors

Yet, studies* and empirical data show: due to variability within a space and variability of occupants, 30-50% of all occupants minus one are uncomfortable

*Augenbroe and Park (2007). Normative thermal comfort assessment. Indoor and Built environment, 2008; 17; 4:324-333

The Building as mediator

Occupancy

Control HVAC Reactivity Spatial and temporal control

Actions Behavior

Thermal comfort IAQ

Building

Direct Electricity Use (LP)

Indirect: HVAC

Breakdown of consumers

The true breakthrough is coming by new connections between the nodes: New engineering solutions and occupant centric control Direct electricity becomes major target for ZEB!

Final words

• ZEB agenda needs to move beyond the building unit ▫ ZE at the building unit level can be counterproductive

• The costs of power and consumption need to be treated in parallel ▫ Distributed generation and storage considerations

• Breakthroughs in ZEB design: ▫ New engineering solutions that mediate the nodes of the triangle ▫ Managing the performance gap through uncertainty and risk

analysis (still predominantly in research domain)

Thank you for your attention!

Questions? fried@gatech.edu

Acknowledgement: PhD students, HPB lab College of Architecture, Georgia Tech