Renewable Hydrogen Power System for Isolated Communities
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by Anna Chulaki, National Hydrogen Association

The Desert Research Institute (DRI) in Nevada is developing a user-friendly hybrid energy system employing renewable (wind and solar) energy sources along with hydrogen energy storage and a fuel cell, for use in remote areas with abundant but intermittent wind and/or solar energy. According to researchers at DRI, such remote off-grid communities, with the value of electricity several times higher than the electricity price in large power grid markets, are an important potential entry market for renewables and fuel cells.

In isolated regions, intermittent renewable power systems integrated with adequate energy storage will provide a steady supply of electricity to a community, and be competitive with a diesel fuel supply currently required by almost all remote locations. The energy storage component will provide power to the load when the renewable sources are inadequate, e.g., low wind, night time. Hydrogen storage seems to show the most promise where compressed air and pumped hydroelectric are not practical.

The System
prototype of such a stand-alone hydrogen-fuel-cell power utility system, using wind and solar energy sources, has been developed at DRI during the last two years in a cooperative effort with the University of Nevada-Reno (UNR) and Stuart Energy. This hybrid system currently employs two wind turbines (1.5KW each), two solar photovoltaic arrays (1KW each), a 2KW proton exchange membrane (PEM) fuel cell, an electrolyzer producing up to one normal cubic meter of hydrogen per hour, a hydrogen storage tank and four deep cycle batteries. It also includes a fully programmable data acquisition and control system using software and computer interfaces developed by the UNR team. This control module operates to automatically meet load demand by matching power output from solar, wind or the fuel cell, so that the system operates without the need for a technician to run it.

The system is designed around a 24-volt DC bus bar. Electricity from multiple sources (solar arrays, wind turbines, batteries and fuel cell) goes to multiple uses from one electrical node. Residential electric load is being simulated by a programmable 120vac resistance load which draws electricity off the bus bar via an inverter. If the power produced is greater than the load, the computer control system turns on the electrolyzer. The electrolyzer draws electricity from the bus bar and produces hydrogen and oxygen. The oxygen is vented to the atmosphere, while the hydrogen is compressed to 100 psig and stored in a tank. If the power produced is less than the load, the computer control system turns off the electrolyzer and turns on the fuel cell stack. Hydrogen flows from the storage tank to the fuel cell stack, which then produces electricity which goes to the bus bar. The relatively small battery storage is connected directly to the bus bar to help regulate the bus bar’s voltage and to provide “peak power” during the short instances while the fuel cell is adjusting to transients. Thus, the load is always supplied with renewable electricity.

Project Goals
In the course of this research project the team has built a user-friendly residential-scale system to use intermittent wind and solar sources to produce continuous power. Although off-grid sites in remote areas are expected to be the main beneficiary of such hybrid power systems, the results of this research might be applicable to on-grid sites as well, for example, in ensuring power stabilization and reducing expensive (>$2.50/kWh) peak energy costs for buildings.

Eventually, the key benefits that are expected to result from the implementation of such a prototypical, uninterruptable renewable power system demonstration are:

For more information, contact Dr. Roger Jacobson via email at roger@dri.edu or by phone at +1-775-673-7364. ©2002. All Rights Reserved. A Publication of the National Hydrogen Association.
This material may not be reproduced in any form without permission.

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