TY - Generic
T1 - Energy and Cost Benefits of DC Power in ZNE Buildings
T2 - American Council for an Energy-Efficient Economy (ACEEE) 2018 Summer Study, Pacific Grove, CA
Y1 - 2019/08//
A1 - Daniel L. Gerber
A1 - Vagelis Vossos
A1 - Richard E. Brown
A1 - Wei Feng
A1 - Chris Marnay
AB - Improvements in building end-use efficiency have significantly reduced the energy intensity of new buildings, but diminishing returns make costeffective zero-net energy (ZNE) buildings a challenge. A largely untapped efficiency strategy is to improve the efficiency of power distribution within buildings. Direct current (DC) distribution with modern power electronics has the potential to eliminate much of the power conversion loss in alternating current (AC) building distribution networks. Previous literature suggests up to 15% energy savings in DC ZNE buildings with onsite generation and battery storage. Nonetheless, DC faces a market disadvantage against AC, and the benefits of DC distribution must be compellingly demonstrated before wide adoption. This paper presents recent modeling of DC vs. AC distribution in buildings, based on detailed load and generation profiles, wire losses, and power conversion efficiency curves. Our analysis shows that annual energy savings can range from approximately 8% of baseline electricity use in an office with PV and no battery, to approximately 15% in a building with a large PV array and battery. This paper also presents a techno-economic analysis framework that evaluates the cost-effectiveness of DC systems in several commercial buildings based on commercially available products. Based on a Monte Carlo analysis, we find that DC systems can be cost effective in all scenarios that include battery storage and onsite solar, whereas for systems without storage, DC distribution is not cost effective.
JF - American Council for an Energy-Efficient Economy (ACEEE) 2018 Summer Study, Pacific Grove, CA
ER -
TY - JOUR
T1 - A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings
JF - Applied Energy
Y1 - 2018/01//
SP - 1167
EP - 1187
A1 - Daniel L. Gerber
A1 - Vagelis Vossos
A1 - Wei Feng
A1 - Chris Marnay
A1 - Bruce Nordman
A1 - Richard E. Brown
KW - commercial buildings
KW - direct current
KW - efficiency
KW - modelica
KW - simulation
AB - Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage, and an increasing prevalence of internal DC loads. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. The buildings are all modeled with solar generation, battery storage, and loads that are representative of the most efficient building technology. A variety of parametric simulations determine how and when DC distribution proves advantageous. These simulations also validate previous studies that use simpler approaches and arithmetic efficiency models.This work shows that using DC distribution can be considerably more efficient: a medium sized office building using DC distribution has an expected baseline of 12% savings, but may also save up to 18%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building that can island as a microgrid. DC is most advantageous in buildings with large solar capacity, large battery capacity, and high voltage distribution.
VL - 210
U2 - LBNL-2001160
JO - Applied Energy
DO - 10.1016/j.apenergy.2017.05.179
ER -
TY - JOUR
T1 - Techno-economic analysis of DC power distribution in commercial buildings
JF - Applied Energy
Y1 - 2018/11//
SP - 663
EP - 678
A1 - Vagelis Vossos
A1 - Daniel L. Gerber
A1 - Youness Bennani Smires
A1 - Richard E. Brown
A1 - Chris Marnay
KW - commercial building
KW - DC distribution
KW - DC microgrid
KW - direct current
KW - Techno-Economic Analysis
AB - Improvements in building end-use efficiency have significantly reduced the energy intensity of new buildings, but diminishing returns make it a challenge to build very-low energy buildings cost-effectively. A largely untapped efficiency strategy is to improve the efficiency of power distribution within buildings. Direct current (DC) distribution with modern power electronics has the potential to eliminate much of the power conversion loss in alternating current (AC) building distribution networks that include photovoltaics and DC end uses. Previous literature suggests up to 15% energy savings from DC power distribution in very energy efficient buildings with onsite generation and battery storage. This paper extends prior energy modeling of DC versus AC distribution in buildings, to consider the cost of implementing DC systems on a life-cycle basis. A techno-economic analysis framework based on commercially available products that evaluates the cost-effectiveness of DC systems is presented. The analysis is conducted for three commercial building types in two California climate zones and for various PV and battery storage capacities. Monte Carlo simulation is used to compute the payback period and lifecycle cost savings of DC versus AC distribution systems. A future-market scenario is also examined, which evaluates how future efficiency improvements in power converters and changes in electricity tariffs may affect cost savings. This analysis shows that DC systems can be cost-effective in all scenarios that include large capacities of battery storage and onsite solar, whereas for systems without storage, DC distribution is generally not cost-effective.
VL - 230
JO - Applied Energy
DO - 10.1016/j.apenergy.2018.08.069
ER -
TY - CONF
T1 - A simulation-based efficiency comparison of AC and DC power distribution networks in commercial buildings
T2 - Second International Conference on DC Microgrids
Y1 - 2017/06//
A1 - Daniel L. Gerber
A1 - Vagelis Vossos
A1 - Wei Feng
A1 - Aditya Khandekar
A1 - Chris Marnay
A1 - Bruce Nordman
AB - Direct current (DC) power distribution has recently gained traction in buildings research due to the proliferation of on-site electricity generation and battery storage and an increasing prevalence of end uses operating internally on DC. The research discussed in this paper uses Modelica-based simulation to compare the efficiency of DC building power distribution with an equivalent alternating current (AC) distribution. A variety of parametric simulations determine how and when DC distribution proves advantageous. This work shows that using DC distribution can be considerably more efficient than AC: a medium office building using DC distribution has an expected baseline of 11% savings, but may save up to 17%. In these results, the baseline simulation parameters are for a zero net energy (ZNE) building with enough battery storage to act as an islanding microgrid. DC is generally most advantageous in buildings with large solar capacity, large battery capacity, and high voltage DC distribution. In addition, based on the efficiency modeling results, a comparison of the economic performance of DC vs. AC distribution systems in commercial buildings is conducted. The results for the baseline scenario show that DC distribution systems in buildings can be cost effective when PV generation and battery storage are included in the building.
JF - Second International Conference on DC Microgrids
ER -