This Small Business Innovation Research Phase I project addresses current limitations in hydrogen compression and enables reduction in hydrogen requirements for several applications through recycling of exhaust hydrogen containing water and other benign impurities. This project will demonstrate the feasibility of operating a proton exchange membrane (PEM)-based device as a high efficiency electrochemical compressor/purifier. Advantages over previous research in PEM-based hydrogen pumps include use of a microporous plate for improved water distribution, which will enable more uniform fluid distribution and high current densities. The objectives of this phase include demonstration of a prototype cell, determining the separation efficiency of a prototype device as a function of output pressure, and developing design boundaries for optimization in Phase 2 and integration into a system. Cell stack design experience along with the improved plate technology will be utilized in order to address current limitations due to local membrane dryout. The anticipated result will be an improved hydrogen recycler which will enable substantial reduction in hydrogen production cost and new market opportunities.
The broader impact/commercial potential of this project includes applications ranging from power plants to heat treating to backup power and fueling. For example, over 16,000 power plants worldwide use hydrogen as a cooling fluid in the turbine windings. Currently, increases in dew point cause significant decreases in cooling efficiency and increase windage losses by several percent, requiring purging of the hydrogen chamber and increased production to backfill. Thus, significant energy waste is generated. Current solutions for hydrogen compression are also noisy, bulky, and inefficient. In applications where hydrogen is being evaluated as an alternative fuel, high pressure storage is needed. Having a mechanical compressor that represents half of the size and material cost of a home fueling or backup power device is not commercially feasible. The device proposed has the opportunity to decrease the energy required to produce pure hydrogen by 75% over generating additional hydrogen from water, and to compress the hydrogen with as little as 100 mV of overpotential even at high current density. Advances in these areas would find immediate commercial interest, and address key strategic areas on the government agenda related to energy savings and green technology.
In this Phase I SBIR project, Proton Energy Systems, Inc. d/b/a Proton OnSite ("Proton") demonstrated feasibility of recycling and compressing waste hydrogen for high purity applications via an electrochemical pump. The enabling feature of the cell is the proton exchange membrane, which separates the two chambers of a cell. Hydrogen mixed with impurities can be oxidized on one side of the membrane to protons, which selectively cross the membrane. The protons are then recombined to form pure hydrogen gas on the other side of the membrane. The outlet stream can be pressurized by putting a back pressure regulator on the outlet port so that the electrochemically generated hydrogen pressure builds up to the regulator value. Thus, pure hydrogen is formed and compressed from impure hydrogen, leaving the impurities on the opposite side of the membrane. This technology has many potential applications, ranging from hydrogen recapture for power plant generator cooling, heat treating furnaces with reducing atmospheres, and semiconductor processing, purification of hydrogen from reformate streams, and compression of hydrogen to high pressure for vehicle fueling or energy storage. The Phase 1 goals were to demonstrate proof of principle of gas output purity and pressure, improve efficiency/energy loss over existing solutions, and develop the high level system concept to fabricate a relevant test system. Three significant advancements were achieved in the course of the 6 month project. First, a hydrogen generation test system was modified in order to enable testing of the cell stack hardware in a compression/purification mode. The system was designed to take a low pressure input gas stream of hydrogen or hydrogen mixture and convert it to 200 psi high purity hydrogen. Second, a membrane electrode assembly (MEA) was developed which enables much higher current densities than the baseline. Previous cell designs had used thick membranes which added significant resistance to the cell and caused high efficiency losses. The new configurations used membranes which were over 50% thinner yet maintained high durability to the 200 psi conditions. Finally, the cell stack design was modified to incorporate a newly designed humidification plate and manifold into the stack for separate cooling water. A key parameter in membrane conductivity is the water content; the membrane needs some humidity in order to rapidly conduct protons. However, too much liquid water can cause flooding at the membrane surface, preventing hydrogen access. The purpose of the humidification plate was to enable dry hydrogen to take up water vapor and ensure sufficient water in the membrane, while removing any liquid water from the chamber to prevent flooding. A humidity stress test established that the humidification plate served its intended function, enabling a wider tolerance to input feed stream conditions. The new plate also improved voltage performance vs. the baseline cell. This advanced alternative cell configuration represents a factor of three improvement in throughput of hydrogen while operating at the same cell potential (250 mV). Stated another way, the advanced configuration represents an increase in cell efficiency to about 92 percent at 1.0 A/cm2 compared to 80 percent with the baseline cell. This technology represents an alternative to current solutions for hydrogen compression, which are noisy, bulky, and inefficient. In applications where hydrogen is being evaluated as an alternative fuel, high pressure storage is needed. Having a mechanical compressor that represents half of the size and material cost of a home fueling or backup power device is not commercially feasible. The device proposed has the opportunity to decrease the energy required to produce pure hydrogen by 75% over generating additional hydrogen from water, and to compress the hydrogen with as little as 100 mV of overpotential even at high current density. Advances in these areas have immediate commercial interest, and address key strategic areas on the government agenda related to energy savings and green technology.