1. SYSTEM DESCRIPTION Jay Schmuecker and David Toyne

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1 SOLAR HYDROGEN FUELED TRACTOR SYSTEM DESCRIPTION Jay Schmuecker and David Toyne Sun tracking solar panels generate electricity that is used to power an electrolyzer that separates deionized water into oxygen and hydrogen. The hydrogen is pressurized using compressed air driven pumps and stored in composite storage tanks. The hydrogen is bleed/pumped into the tractor tanks. The tractor contains an internal combustion engine that is fueled by hydrogen or a combination of hydrogen and ammonia. A control and instrumentation assembly automates the control of the major components. A functional system schematic, not including the control and instrumentation assembly, is shown in Figure SOLAR ARRAYS Three (3), sun tracking, two-degree-of-freedom solar trackers, carrying 12 solar panels each, are contained in the fenced area. The combined output is rated at 8.1 kw. Over a year the average daily power available from solar panels is roughly equivalent to that available during a clear midday 5 hour time period. Each solar panel array feeds its DC power to an inverter in the equipment room where it converted to 240/60/1 (240 volts Alternating Current at 60 Hz. Single phase.) 1.2 POWER FUNCTIONS AND PERFORMANCE When a predetermined minimum preset level of solar power is available, the hydrogen related components are automatically powered by solar power alone (2,500 Solar Watts), or a mixture of solar and grid power (1,250 Solar Watts). We did not include storage batteries in the design because of the initial cost and maintenance. When the hydrogen related components are turned off, or if there is insufficient solar energy to operate the equipment, the unused generated solar power is fed to the grid. 1.3 FACILITY The east end of a farm building, that was once a hog barn, has been modified to contain three rooms. The west room, which is continuously ventilated, houses the tractor when not in use. An instrumentation cable can be connected to the tractor to remotely measure the tractor hydrogen tank pressure. An air compressor and compressed air after cooler is also located in the storage room. The south-east room, the equipment room, houses the air conditioning unit, air humidifier, the power inverters and power instrumentation, the Hydrogen Control 1

2 Figure 1. System Schematic 2

3 and Instrumentation Assembly, the water deionizer, a second air compressor, and compressed air drying equipment. The third room contains the electrolyzer. The electrolyzer room exhaust opening at the peak of the ceiling contains a hydrogen sensor, and a similar sensor in the attic space above room. These sensors are monitored by the Instrumentation and Control Computer and will shut down the system if a leak is sensed. A separate fenced area contains the 1,000 gallon staging tank, eight high pressure storage tanks, the raised platform and dispenser for tractor refueling. Also within the fenced area is a small vented metal hut containing the hydrogen pumps with isolation valve and an air surge tank. As a safety precaution, there is no electrical devices that could generate a spark within the enclosed fenced area. Low voltage instrumentation and control wiring is provided to monitor and control pumping activities. The solar arrays are located in a second separate fenced area. 1.4 WATER DEIONIZER A water deionizer located in the equipment room takes about a quart of water per hour water from a nearby well and treats it for use when the electrolyzer is operating. The deionizer contains a water pump that continuously circulates treated water. 1.5 ELECTROLYZER The hydrogen generation unit is rated to provide about 0.2 lb/hr of gaseous hydrogen until a maximum pressure of 200 psi is reached. This rate is about a pound of hydrogen (194 standard cubic feet) over the average 5 hour/day array power generation time. We have the ability to adjust the electrolyzer hydrogen output so that it is closely related to the power available from the solar arrays. We use power from the grid during the electrolyzer startup, because it requires 7 kw for the first 2 minutes, which is may be higher than the array output. We can also use power from the grid to make up for short periods of solar power short fall. To minimize the problem of clouds varying the solar power from the arrays significantly for short periods during the day, and causing excessive electrolyzer cycling; we use a rolling average of the last 16 minutes of solar power. The electrolyzer can generate hydrogen and oxygen gases when there is sufficient solar power output, and the hydrogen staging tank contains less than 200 psi. The hydrogen gas is sent to the low pressure staging tank and the oxygen is vented. 3

4 There are several interlocks in the hydrogen generation unit that assure safe operation. Figure 2 is the Hydrogen Gas Flow Schematic. 1.6 STAGING TANK The hydrogen generated is routed underground to the 1000 gallon steel staging tank that holds about 9.4 lbs (1,824 standard cubic feet) of hydrogen gas at 200 psi. 1.7 AIR COMPRESSORS AND AIR DRYERS Two air compressors, one in the equipment room and the second in the tractor storage room, provide 14 SCFM of air up to 125 psi. Air compressor #1 is used as a priority to drive the hydrogen storage pump that moves hydrogen from the staging tank into the storage tanks, or drives the tractor fill pump to move hydrogen from the storage tanks to the tractor tanks. At the operator s discretion both compressors may be used to drive the Storage or Tractor pump to reduce the tank fill time. The two compressors are piped together and share a single air tank. An after cooler reduces the compressed air temperature before it goes into the air receiver tank. The air is then routed through a refrigerated dryer and can be switched through a desiccant dryer. The compressed air is routed to a surge tank in the pump hut and provides the power to operate either of the two hydrogen transfer pumps. 1.8 HYDROGEN PUMPS The hydrogen pump assembly contains the storage pump and tractor pump that are driven by compressor air. After the manual valves on the assembly are set, all pump functions are controlled by the Instrumentation and Control Computer. The pump assembly also contains pressure relief valves that will be activated if the storage tank or the tractor tank pressures exceed 105% of 3,600 psi. 1.9 CONTROL AND INSTRUMENTATION The Instrumentation and Control computers, capable of being monitored via the internet, measure solar power output, hydrogen tank pressures, and ambient temperature and controls the electrolyzer, deionizer, air compressor, air drying, and hydrogen pump operations. The rack control panel is used to manually set the subsystem control functions to Manual, Auto or Off. 4

5 Figure 2 Hydrogen Gas Flow Schematic 5

6 - Off: When neither Manual nor Auto functions are selected the component is turned off or not allowed to operate. - Manual: The system operates at full capacity using available solar power augmented by grid power, regardless of the amount of solar power available. The electrolyzer will produce hydrogen gas until the storage tank pressure reaches 200 psi. In the manual function the air compressor(s) and the storage pump will operate until the storage tank pressure is reaches 3,600 psi or the staging tank pressure is below 100 psi. The air compressor(s) and either the hydrogen storage pump, or tractor pump may be operated when the tank pressures indicate transferring hydrogen can be done. In the manual function the air compressor(s) and the tractor pump operate until the tractor tank pressures reach 3,000 psi or the storage tank(s) pressure falls below 200 psi. - Auto: Operation is dependant on adequate solar power availability. It requires a minimum level of solar power to begin the start up procedure and we vary the hydrogen production output based on the available solar power. The electrolyzer is operated to fill the staging tank. The electrolyzer is shut down when the staging tank pressure is above 185 psi. The electrolyzer is turned back on when the air compressors are turned off. When in the auto function, when the staging tank pressure reaches above 185 psi, the controls will shut down the electrolyzer and use the solar power to run the air compressor(s) and the air-driven hydrogen storage pump to transfer hydrogen from the staging tank into the storage tanks. The air compressor and the transfer pump are turned off when the pressure in the storage tanks reaches 3600 psi or the staging tank pressure is below 100 psi. When in the auto function if hydrogen gas is to be pumped from the storage tanks or to the tractor, the controls will shut down the electrolyzer to power the air compressors and the air-driven hydrogen transfer pump. The air compressors and the transfer pump are turned off when the pressure in the tractor tanks reaches 3000 psi or the storage tanks pressure is below 200 psi. When in the auto function there are two power modes that can be manually selected on the Control Panel: - Solar Only. The Instrumentation and Control Computer measures the power from each of the three power inverters. When the power generated 6

7 by the arrays is above a specified level, (that set by the program in the computer), solar power alone is used to power the hydrogen related components. If the power is below the required level for a predetermined period of time the electrolyzer is placed in standby and then after a time period is turned off; or if the power is below the required level for a predetermined period of time the air compressor(s) and hydrogen pump(s) is/are turned off. - Mixed Power: The control system will power the hydrogen related components using solar power supplemented by grid power. The normal setting uses a ratio of 50% solar power. Minimum levels of solar power are still required to operate the equipment. The Instrumentation and Control Computer adjusts electrolyzer output automatically based on available solar power. It also controls the air compressors, drying equipment, and hydrogen pumps using a mixture of solar and grid power 1.10 STORAGE TANKS Hydrogen is stored in a bank of graphite composite wrapped storage tanks, holding about 125 pounds (24,250 standard cubic feet) of hydrogen at 3,600 psi. There are 7 16 inch diameter X 10 ft long and 1 21 inch diameter X 10 ft long tanks. The latter tank is identical to each of the four tractor hydrogen fuel tanks TRACTOR The modified John Deere 7810 Tractor is powered by a Hydrogen Engine Center 9.4 Liter Ox Power Engine. It based on a Ford 460 cu-in, V-8 design (rated at about 150 hp) and runs on gaseous hydrogen or a mixture of hydrogen and gaseous ammonia. From the cab the operator can monitor the hydrogen tank pressure and ammonia tank fluid level as well as select which fuel is used. Four 21 inch diameter X 10 ft long graphite composite fuel tanks are mounted over the cab of the tractor to carry the hydrogen fuel at 3,000 psi. About 80 pounds (570 gallons, 15,520 standard cubic feet) of hydrogen gas can be carried on the tractor. A pressure relief valve is installed on the tractor to activate if the tractor tank pressures exceed 105% of 3,000 psi. A 60 gallon ammonia tank carrying up to 50 gallons of liquid ammonia is mounted in front of the hydrogen tanks for use as an alternate fuel supply TRACTOR FUELING A hydrogen dispenser mounted on a raised platform is used to fill the tractor tanks. A commercial nozzle, rated to fuel tanks to 3,600 psi, is connected to the tractor for 7

8 hydrogen fueling. Although the fueling nozzle automatically grounds the tractor, a separate grounding strap is connected to the tractor before the nozzle is connected. When the tractor fueling nozzle is connected to the tractor, flow valves in the dispenser enclosure must be opened so the hydrogen in the storage tanks can be bled into the tractor fuel tanks. When the pressure has equalized, a switch located at the base of the platform stairs on the fence must be activated to turn on the air driven tractor hydrogen pump. The tractor tanks are filled until, either the tractor tanks reach 3,000 psi, the storage tank pressure has dropped to below 200 psi, or the fill nozzle is turned off. As an option the tractor can be parked at the fueling location and the storage hydrogen pump will pump directly into both the storage tanks and the tractor tanks. This increases the overall gas storage capacity of the final installation. The selector switch at the base of the stairs on the fence is used to allow the output of the hydrogen storage pump to fill the tractor tank to a maximum 3,000 psi, the tractor tank maximum desired pressure. (This is less than the identical 21 inch tank farm storage tanks, which are designed and used to hold 3,600 psi hydrogen.) 1.13 ISOLATION VALVES A separate air system is used to control the hydrogen isolation valves. A small air storage tank, located in the equipment room ceiling, is supplied from the air compressors with a diverter valve and its own pressure control switch. This air is used to open the isolation valves in the hydrogen pump assembly. These pneumatic-operated valves are in each of the lines that lead to tanks or the tractor fill dispenser. They are opened when hydrogen is to be pumped or dispensed. They close when pumping or dispensing is stopped, if an emergency stop switch is activated, or if there is a power failure EMERGENCY STOPS Electrolyzer and hydrogen pumping emergency stop provisions are provided: - On the electrolyzer to shut off the electrolyzer, - On the control console left side to shut off the electrolyzer, and another on the right side to shut off the air compressor and hydrogen pumps stopping hydrogen flow, - On the Tractor Fueling Control Panel near the base of the platform stairs to shut off the air compressors and hydrogen pumps. 8