Primus Energy Storage Tech Goes with the Flow


Primus Power is a Hayward, California, startup that makes flow batteries for grid-scale energy storage.  A flow battery is a type of rechargeable battery that works by the flow of electrolytes through an electrochemical cell, which converts the chemical energy to electricity. 

Unlike typical batteries, in which the active chemical species are stored inside the battery, the dissolution of active species in the electrolyte of a flow battery permits external storage of reactants.  For this reason, flow batteries are not limited in the amount of active material that can be used and have the ability to scale up power and energy density.

Primus owns a family of at least three pending patent applications relating to its flow battery technology, including U.S. Patent Applications Publication Nos. 2009/0239131 (‘131 Application), 2010/0021805 (‘805 Application) and 2011/0070468 (‘468 Application). 

The ‘131 and ‘468 Applications are entitled “Electrochemical energy cell system,” and are directed to energy generation systems including a cell stack assembly (12) made up of a plurality of cells (13).  Each cell (13) includes a positive porous electrode and a negative metal electrode.  

Pressurized halogen reactant enters the system through feed pipe (15) and flows through a metering valve (17) to mixing venturi (18).  Circulation pump (16) circulates the electrolyte from reservoir (19) through the mixing venturi (18), to the positive electrodes in the stack assembly (12) and then back to the reservoir (19).

According to the  ‘131 and ‘468 Applications, the metal electrode includes zinc, the halogen includes chlorine, the electrolyte includes an aqueous zinc-chloride electrolyte, and the halogen reactant includes a chlorine reactant (though this Greentech Media article says the Primus technology is based on a zinc-bromine system, not chlorine).

The ‘805 Application adds the concept of maintaining the system’s inner pressure above the liquefication pressure of the halogen reactant.

Primus’s battery flow technology has received some high level attention and funding, including $14 million from the U.S. Department of Energy and $11 million in venture capital, according to the Greentech Media piece.

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Eric Lane

Eric Lane, the founder and principal of Green Patent Law, is an intellectual property lawyer and registered U.S. patent attorney in New York and is a member of the bar in New York and California. Eric has more than two decades of experience working with wind, solar PV, CSP, biofuels, and geothermal, energy storage technologies, carbon capture and sequestration, medical devices, data communications, mechanical, chemical, internet and software.