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STANDALONE “GREEN” COMMUNITY-CENTER BUILDINGS: HYDROGEN GENERATION/STORAGE/DELIVERY SYSTEM FOR WHEN PRIMARY ENERGY STORAGE IS AT CAPACITY
Impact/Purpose:
Challenge Area: EPA-G2007-P3-Z3 – Energy
The multi-disciplinary initiative “Standalone ‘Green’-power for (International) Village Settings” at Elizabethtown College has the primary goal of designing and providing highly-reliable, low-maintenance, long-lifetime (>30 years), low-environmental-impact community-center buildings powered entirely by a renewable energy source. The primary technical challenge related to sustainability in standalone wind or solar-powered buildings is the realization of a moderate-scale energy storage system with very long lifetime, high system efficiency, and reasonable cost. In this application, we seek to maximize energy storage and minimize waste by capturing power generation potential that is typically wasted in standalone installations.
Description:
Overall, the implementation of a computer-controlled hydrogen generation system and subsequent conversion of small engine equipment for hydrogen use has been surprisingly straightforward from an engineering and technology standpoint. More testing is required to get a better grasp on a longer-term installation of the hydrogen generation system especially in an infrequently monitored facility. This EPA P3 Phase I hydrogen project, which is a component of this larger initiative, has been surprisingly trouble-free in its implementation and thus we currently plan to implement as a part of the initial full-scale community center implementation in the Kwa-Zulu Natal region of South Africa. This actual field implementation will be a true test of the usefulness and durability of the hydrogen system. We are skeptical of the durability and long-term usage of the hydrogen system in a challenging infrequently-monitored environment, but have been pleasantly surprised by the ease of conversion of small engine equipment and cooking equipment.
Specific products from the 2007-08 EPA P3 Phase I project include 1) simulation software for the supplementary storage system, 2) a prototype hydrogen generation system, 3) two small engine conversions, and 4) a grill conversion.
1) A LabView simulation was developed to have inputs of hourly solar data, solar array size and efficiency, battery capacity, power usage, and hydrogen generator average power and flow rate. The simulation processes archived solar insolation data to determine current power levels and uses time of day, current battery level (kWhr remaining), and power levels to decide when the lights are on, when hydrogen is generated, and so forth. The simulation allows us to modify our designs based on solar array size, location of installation, battery sizing, hydrogen generator sizing and hydrogen storage capacity. For example, for the current parameters for the Elizabethtown College Solar Cabin, the simulation provides an estimate of 55 of our Ovonics metal hydride 900 standard liter containers would be filled per year. The simulation provides a plethora of information for analysis, including times when the battery level is dangerously low, when there is substantial excess power even with the hydrogen system running, and the effects of changing any number of design parameters.
2) The hydrogen generation and control system is the centerpiece of this EPA Phase I project. The workhorse is a Distributed Energy HoGEN 300 Hydrogen Generator ($9,900) with storage provided by three 900 Liter Ovonics metal hydride containers ($633 x 3). The generation of hydrogen is turned on/off by computer controlled relay based on inputs of battery voltage and solar irradiance. The setup is sufficient to operate lawn equipment or cooking equipment approximately two hours per week. Meaningful data from the hydrogen generation and control system are not yet available. The hydrogen generation system has not been operated outside of the laboratory, where only preliminary testing has taken place. While the portable hydrogen system will be demonstrated at the April 2008 EPA P3 Expo, data from operation at the Solar Cabin will not be available until late 2008.
3) Conversion of small 4-cycle engines to run on hydrogen is relatively straightforward. In both the lawnmower and weed trimmer conversion, the design goal was to bring the hydrogen as close as possible to the engine intake. For our primary test bed – a set of Tecumseh TVS-90 lawnmower engines – conversion was as simple as drilling the fuel intake line to admit a hydrogen line. For the lawnmower, engine starting remains an issue, but once running the lawnmower operates well. A Craftsman 4-cycle 29 cc convertible gas weed-trimmer was also “converted” for hydrogen use. The intake manifold is quite small and plastic, so modification of the weed trimmer was accomplished by removing the gas tank, plugging the fuel return line and attaching the hydrogen supply to the fuel intake line. Carrying the hydrogen cylinder remains a challenge and is currently designed to be carried on the back with a flexible plastic tubing in place of the stainless steel tubing of the lawnmower prototype. Data for the small engine equipment on fuel consumption and emissions data (from a standard automobile 5 gas analyzer) has yet to have been acquired, but will be available for the April 2008 EPA P3 Expo.
4) Grill conversion is also relatively straightforward, with the primary modifications related to connecting the hydrogen containers to the propane lines and replacement of the original propane burners. We use a Kenmore gas grill and replace the burners with shaped stainless steel pipes welded shut at one end and drilled with a series of small holes (#68 drill). The gas grill conversion is not complete at the time of this writing.