Over a year, net zero energy (NZE) houses produce and feed zero net metered electrical energy to the grid. Technical challenges, notably the `duck curve' arise due to the fact that peak solar generation and load demand are seldom coincident. Common approaches to mitigate this limitation include the curtailment of solar power, and the use of storage. Surplus solar energy may be stored in a battery, which can subsequently be discharged to supply the home electricity needs when demand is in excess. In addition to batteries, less expensive electric water heaters, which are ubiquitous, can be modified as energy storage systems, functioning as `uni-directional batteries' by virtue of their high thermal mass. This paper proposes the use of a hybrid energy storage system including both batteries and variable power electric water heaters in NZE residences. It is demonstrated that the hybrid energy storage system along with solar PV generation coordinated and virtual power plant (VPP) controls would reduce the required battery size and ratings while still harvesting the maximum solar energy potential. The proposed control strategy enables the NZE homes to produce dispatchable power or behave like controllable loads, and benefits at the utility level are demonstrated by interconnection of NZE homes with an IEEE 13 node test feeder system. The technology has the potential to mitigate all issues related to solar power variability.

Document Type

Conference Proceeding

Publication Date


Notes/Citation Information

Published in 2018 IEEE Energy Conversion Congress and Exposition (ECCE).

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The document available for download is the authors’ manuscript version that is accepted for publication. The final published version is copyrighted by IEEE and available as: H. Gong, V. Rallabandi, D. M. Ionel, D, Colliver, S.Duerr, and C. Ababei, “Net Zero Energy Houses with Dispatchable Solar PV Power Supported by Electric Water Heater and Battery Energy Storage,” Rec. 2018 IEEE Energy Conversion Congress and Exposition (ECCE), Portland, OR, Sept 2018, pp. 2498-2503. doi: 10.1109/ECCE.2018.8557720.

Digital Object Identifier (DOI)


Funding Information

The support of University of Kentucky, the L. Stanley Pigman endowment and the SPARK program is gratefully acknowledged.