Energy Storage & Hot Topics in Renewable Energy

Technical Symposium

Demystifying the differences between Distributed Energy Storage and Central Energy Storage in PV-Systems

Wednesday, September 26
12:15 PM - 12:30 PM
Location: 203AB

This presentation recognizes the amazingly fast growth of "Distributed Energy Storage" in recent solar installations which integrate PV generation, + energy storage, and, + active power quality control; making them "Smart Energy Technologies". Central Energy Storage (typically used in Utility substations) has been deployed effectively for over 20 years. This presentation explores why new-DER's have a high growth rate because they represent solutions to newly emerging and more localized problems in Utility networks.

In this presentation we will see the obvious differences between distributed and centralized energy storage and discuss the intersection (which can be rather broad) between where optimum deployment of energy storage needs to be Centralized versus Distributed.
Because the introduction of energy storage in a PV system enables many advantageous power quality treatments - the subject of Power Quality Control must be introduced as a primary driver of the usefulness of energy storage in PV systems, large or small.

By observation - I can report that the appearance of "distributed energy storage" is a relatively new phenomenon which began appearing at SPI vendor's displays around 2010 (in it's present "packaging") albeit batteries and solar panels have been married for as long as PV systems have been used. Central Energy Storage (the use of Sodium-Sulphur "station batteries" for example) has been in use for over 25 years - and in their early days were not often associated with solar-PV systems. With the advent of new, higher power and greater energy cell technologies (lithium and NiMH for example) both central storage and distributed energy storage devices have adopted these new secondary-battery (meaning rechargeable batteries) cell types.

The emergence of these new cell chemistries is intrinsically related to the $Billions of research dollars invested (since 1990) in energy storage media urged by the need for electrification of our transportation fleet with a "happy fallout" leading to a uniform adoption by the Renewable Energy Industry to advance the performance of intermittent generation technologies, particularly wind and solar.
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The results of the adoption of energy storage are documented by the evolution of nearly a dozen Central Battery suppliers - and at last count over 25 distributed-energy storage systems suppliers, and approximately 80 inverter-vendor's products now compliant with UL1741SA topology (necessary for local power quality control in front of or behind the meter). Such inverters are now offered from 1KW package inverters to 2.5MW station-inverters: all UL1741SA compliant and offered for use with energy storage.

As you can see from my slides - there are a great diversity of products offered - and very little competition between Central vs Distributed energy systems - except possibly on the total energy handled by each technology. In fact most modern power systems need both.

James F. Wolter

Managing Partner
Energy Partners LLC

Professor Emeritus Grand Valley State University. Founder of the University's Renewable Energy Research Center. Clean Energy inventor with 7 patents and patent applications on clean generation, energy storage, and smart power systems

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