HYDROGEN PROGRAM
Fuel cell hybrid vehicle program	Hydrogen fueling stations	Hydrogen generation research	Education and outreach

Electrolyzer and Reversible Fuel Cell

Overview

One of the drawbacks of renewable energy sources is that their availability is not always coincident with real world electrical loads.  For example, a photovoltaic system installed at a single residence will not provide any power for that residence at night or in the early morning.  A potential solution to this problem is the reversible fuel cell.  The reversible fuel cell acts as an electrolyzer to generate hydrogen gas when excess electricity is generated with the renewable resource.  The hydrogen gas is stored for times when the renewable energy is not available. The reversible fuel cell then acts as a traditional fuel cell, using the stored hydrogen to generate electricity.

PV Power Availability and Residential Power Demand

Concept

The first figure shows the electrical generation from a photovoltaic (PV) roof mounted power supply. The generation follows the daily availability of the sun's solar energy for each of the seven days of a typical week. The plot also presents the electrical load demand by a typical residence in southern California. Note that the spikes in load demand occur in the late afternoon and early evening, out of phase with the PV power supply. On one day (Thursday) the demand is especially heavy reflecting the weekly laundry schedule. These data suggest that a means of energy storage would be valuable in order to caputre the power produced during the day, and to utilize the captured energy to produce power at night.

The NFCRC is evaluating this concept through research with a reversible fuel cell as shown in the second figure. During the day, electricity is supplied to the fuel cell to drive the energy flow from right to left and produce hydrogen and oxygen from a supply of water. At night, the hydrogen and oxygen can then be used to produce electricity by driving the fuel cell from left to right.

A schematic showing the integration of the PV and reversible fuel cell into a home is shown in the third figure where:

Reversible Fuel Cell Concept

Reversible Fuel Cell System Integrated into the Home

The NFCRC has tested and demonstrated a reversible fuel cell system and integrated this system with a photovoltaic power supply.  The heart of the experimental system was the Proton Energy Systems Hogen RE-40, which can generate up to 40 standard cubic feet per hour of hydrogen. 

5 kW PV Array at NFCRC

Reversible Fuel Cell Setup with Electrolyzer and Fuel Cell

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