Emerging Technology: DC Power in Commercial Buildings December 9, 2014

Presenter: Suzanne Foster Porter, Director, Research and Technical Services, with Ecova

Dave Denkenberger, PhD Ecova

2014 ACEEE Summer Study

Suzanne Foster Porter, Ecova

Catherine Mercier, Ecova

Peter Turnbull, PG&E

Peter May-Ostendorp, PhD Xergy Consulting

Literature Review: Hypothetical Savings Estimates

Authors Year Application Savings Range

LBNL 2011 Data centers 5 – 28%

EPRI 2006 Data centers 20 – 25%

Vossos (MS thesis) 2011 Residential 5 – 35%

LBNL 2011 Residential 30 – 33%

Opportunities in data centers and residential sector analyzed

Lack of analysis of commercial opportunities (namely office space) despite development of EMerge Alliance standards

DC Distribution as an Opportunity?

Migrating to DC Already dominantly DC

Data source: EIA Annual Energy Outlook 2008

50% Office Electricity Use is Lighting & Plug Loads

DC Alternatives Exist...

Appliance Function

Standard Technology

DC Replacement Technology

Lighting Incandescent or fluorescent lamps* Solid-state lighting

Heating Resistive heating element*

Heat pump driven by variable speed drive

Cooling, refrigeration

Induction motor, single-speed compressor

Variable-speed compressor w/brushless DC motor, VFD

Ventilation, pumps Induction motor Brushless DC motor with VFD

Source: Garbesi, Vossos and Shen, 2011. *Indicates standard tech, can run on DC power; replacement not imperative.

Barriers vs. Benefits

Benefits Barriers

Reduction in electronic waste

Easily reconfigurable overhead lighting

Improved power quality

Legacy AC distribution

Lack of DC-ready products

High cost associated with new technology in low volume

Safety

DC wiring losses

System level outages

Analyzing the DC Distribution Opportunity

Electrical Systems Modeling Approach

Capturing energy flows, conversions, distribution and end-uses

Energy Sources Conversion Local Distribution

Load-Level Conversion Loads

AC Grid Power

PV

Met

er

Inverter

Comm Bldg Transformer Wire loss

Wire loss

Wire loss

Wire loss

Power supply

Ballast/ Driver

VFD

Electronics

Lighting

Resistive

DC Motor Equipment

Building Distribution Losses are about 10% of Building Energy Use

DC Distribution Can Reduce ZNE Energy-Use by 8%

Optimize the wiring for cost (shorter runs/lower gauge)

Why DC in ZNE?

Conclusion

ZNE office buildings are a good candidate for DC distribution – Native DC sources (PV) and native DC loads

– Coincidence of PV and loads

– Optimize the wiring for cost (shorter run lengths, bigger gauge)

A single DC distribution system does not save energy in code compliant buildings

– Could consider a parallel dc system for a subset of loads (such as electronics and lighting together)

Significant barriers exist to moving toward DC distribution

Q & A

Thank you!