Zero Energy Penalty Hydrogen Injection into Natural Gas Pipelines via Asynchronous Electrolysis and Venturi Valve Integration

The objective of this SBIR topic (27A) is to “reduce the energy penalty of traditional compression methods when applied to hydrogen” to improve the cost effectiveness of utilizing the natural gas grid to transport and deliver hydrogen to end users. BST will demonstrate that the compression energy penalty of hydrogen injection into the gas grid can be eliminated completely via integration of asynchronous electrolysis with Venturi valve expansion. Eliminating the compression energy penalty is not possible using existing electrolysis methods, i.e., hydrogen generation from PEM electrolyzers. Therefore, asynchronous electrolysis is a game changing technology that enables affordable hydrogen delivery. The natural gas grid consists of transmission lines (upstream storage and transport) and distribution lines (downstream delivery to end users). The technical problems of upstream hydrogen injection include hydrogen embrittlement of the steel pipes, the high capital expense and energy penalty associated with compressing hydrogen to the high transmission pressure, and limitations on the allowable hydrogen content in natural gas (< 5%) due to constraints of upstream in-line equipment (boost compressors and natural gas fired electric generators). Existing electrolysis technologies cannot practically and affordably support hydrogen injection at downstream distribution facilities, which would circumvent all of the upstream problems, because costly compression, storage, and delivery subsystems would be required. Asynchronous electrolysis accomplishes water electrolysis with the necessary oxygen and hydrogen generation reactions occurring in two distinct, separate periods. During the charge half-cycle (off peak, inexpensive and mostly renewable electricity), oxygen is generated and vented, and the energy required for electrolysis is stored. When the discharge half-cycle is initiated (on peak), the stored energy is released, generating hydrogen gas spontaneously from water in the electrolyte without external energy input. Thereby, asynchronous electrolysis eliminates the requirement of compression and storage, allowing for hydrogen generation at time-of-use. The ambient pressure hydrogen spontaneously generated by asynchronous electrolysis during discharge is mixed with natural gas via integration with Venturi expansion and the high pressure natural gas feed to the distribution facility. Thereby, hydrogen fuel is delivered to end-users through the gas distribution grid with no compression energy penalty and no electrolysis energy penalty. Under Phase I, BST will fabricate an asynchronous electrolysis prototype string (100 gram H2 delivery capacity) and integrate it with an engineered Venturi valve to match hydrogen discharge rates with natural gas flow rates to achieve desired output pressures and mix proportion. BST projects that a cycle life greater than 5,000 is required for an asynchronous electrolysis device to achieve the target cost of less than $2.00/kg H2. The objective is to demonstrate that scale up at distribution facilities will be practical and affordable under Phase II. The commercial opportunity is enormous as there exists approximately 60,000 “city gate” natural gas distribution facilities in the US that could be integrated with this technology. The public benefit is a clean, renewable fuel (hydrogen) that is cost competitive with fossil fuels.