RAPHAEL SCHMUECKER MEMORIAL SOLAR-HYDROGEN SYSTEM...

Copyright 2010-2015 Schmuecker Pinehurst Farm LLC. ALL RIGHTS RESERVED

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RAPHAEL SCHMUECKER MEMORIAL SOLAR-HYDROGEN SYSTEM 1. SYSTEM DESCRIPTION

Sun tracking solar panels generate electricity, used to power an electrolyzer that separates deionized water into oxygen and hydrogen, and to power the air compressors, and a control system. The hydrogen is stored and then pressurized using compressed air driven pumps and held in composite storage tanks. Compressed air is routed through a nitrogen generator that produces pure nitrogen which is stored and then metered along with pressurized hydrogen and any residual ammonia generation gases, into the pump that compresses the three gas mixtures into the inlet cylinders. When the inlet cylinders are pressurized the mixture flows through an ammonia reactor and into outlet cylinders in which the gases are allowed to cool and the ammonia condenses. The residual generation gases are compressed for another pass through the reactor. The collected ammonia flows to an ammonia storage tank for use on corn cropland or use as a tractor fuel. . The tractor contains a 150 hp internal combustion engine that is fueled by hydrogen or a combination of hydrogen and ammonia. The hydrogen is bled/pumped into the four tractor composite tanks above the tractor cab. The ammonia is pumped into a tank in front of the hydrogen tanks. A control and instrumentation assembly automates the control of the components. A system schematic, not including the control and instrumentation assembly, is shown in Figure 1. 2. FACILITY Personnel and equipment safety has been a prime factor in the design and operation of the 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 tractor storage room.

The south-east room, the equipment room, houses the air conditioning unit, air humidifier, the power inverters and power instrumentation, the control and instrumentation assembly, the water deionizer, a second air compressor, and compressed air drying equipment.


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Figure 1. System Schematic


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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 fenced area contains the hydrogen staging and storage tanks, a nitrogen storage tank, an ammonia storage tank, and the raised platform carrying the dispenser for tractor refueling. Also within the fenced area are two small vented metal buildings:

- The hut containing the hydrogen pumps and an air surge tank. - The shed containing the remote control box and ammonia generation subsystem: shed pump assembly, nitrogen generator, surge tanks, inlet cylinders, the ammonia reactor, outlet cylinders, and ammonia collector tanks.

As a safety precaution, there are 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 and ammonia generation activities. Electrical power is provided to the remote control box and an immersed-in-oil electrical heater in the ammonia reactor. The solar arrays are located in a second separate fenced area. 3. SOLAR ARRAYS Three, 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 volt single phase power. 4. POWER PERFORMANCE To minimize the problem of clouds varying the solar power from the arrays for short periods during the day, and causing excessive electrolyzer and air compressor cycling; a rolling average of the last 16 minutes of solar power is used. If the power falls below the threshold, the air compressors are turned off or the electrolyzer placed on stand-by. Storage batteries are not used because of the initial cost and maintenance. When additional power is needed the grid is used. When the hydrogen and ammonia 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.


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5. 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 by the electrolyzer. The deionizer contains a water pump that continuously circulates treated water. 6. ELECTROLYZER The hydrogen generator provides about .2 lb/hr of gaseous hydrogen. This is a pound of hydrogen (194 standard cubic feet) over the annual average of 5 hours/day array power generation time. We have the ability to adjust the electrolyzer hydrogen output so it is closely related to the power available from the solar arrays. Power from the grid may be used during the electrolyzer startup, because it requires 7 kw for the first 2 minutes, which is may be higher than the array output The electrolyzer generates hydrogen and oxygen gases when there is sufficient solar power output, and the hydrogen staging tank contains less than 200 psi. The hydrogen gas flows to the staging tank and the oxygen is vented. There are several interlocks in the hydrogen electrolyzer that assure safe operation. Figure 2 is the Hydrogen Gas Flow Schematic. 7. LARGE TANKS The hydrogen, nitrogen, and ammonia are stored in the following large tanks:

- Hydrogen Staging Tank: The hydrogen generated is routed underground to the 1000 gallon steel staging tank that holds about 9.4 lbs (1,818.7 standard cubic feet) of hydrogen gas at 200 psi.

- Hydrogen 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.

- Nitrogen Storage Tank: Nitrogen is stored in a 1000 gallon steel tank that

holds about 132lbs. (1818.7 standard cubic feet) of the gas at 200 psi.

- Ammonia Storage Tank: About 100 gallons of ammonia is stored in a 120 gallon tank mounted on tires for field application of ammonia and for fueling the tractor.


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Figure 2 Hydrogen Gas Flow Schematic


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- Tractor Hydrogen Tanks: Four 21 inch diameter X 10 ft. long composite storage tanks, mounted above the cab, contain a total of 80 pounds of hydrogen at 3000 psi. The tractor will operate at full power for about four hours before refueling.

- Tractor Ammonia Tank: A 60 gallon tank holding 50 gallons of ammonia is

mounted in front of the hydrogen tanks. The ammonia tank contains 50% of the energy contained in the four hydrogen tanks.

8. AIR COMPRESSORS AND AIR DRYERS Two air compressors, one in the equipment room and the second in the tractor storage room, each provide 14 SCFM of air up to 125 psi. One of the two compressors is used to drive either of the hydrogen storage pumps and either the air-nitrogen pump or the gas mixture pump. Both compressors can be used together to reduce the tank/cylinder 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. Because the pumps can become inoperative and the nitrogen generator damaged by moisture at low temperatures, the air is then routed through a refrigerated dryer and at low temperatures is switched through a desiccant dryer. 9. HYDROGEN PUMPS The hydrogen pump assembly contains the storage pump and tractor pump. 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. 10. ISOLATION VALVES The control air system is used to control the two hydrogen, air-nitrogen, gas mixture pumps, and ammonia reactor isolation valves. They are opened when hydrogen is to be pumped or dispensed, when nitrogen is to be generated, when the mixed gases are to be pumped, or when ammonia is to be made. They close when pumping or dispensing is stopped, if an emergency stop switch is activated, or if there is a power failure. 11. AMMONIA GENERATION The components in the shed used to generate the ammonia are:

- Shed pump assembly: This contains the air-nitrogen pump, the gas mixture pump, isolation valves and pressure transducers. The air-nitrogen


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pump provides compressed air to the nitrogen generator and compressed nitrogen to the nitrogen storage tank. The gas mixture pump receives residual gases from the outlet cylinders after a pass, followed by nitrogen from the nitrogen storage tank, then hydrogen from the hydrogen storage tanks, and pumps them into the inlet cylinders until the pressure reaches 3500 psi.

- Nitrogen Generator: The assembly consists of a hallow membrane unit

that generates 99.5% pure nitrogen and exhausts the other gases.

- Surge Tanks: Three small tanks installed at the inlet to the shed pumps and the inlet to and outlet from the nitrogen generator buffer the compressed gases for downstream components.

- Inlet Cylinders: Six inverted high pressure compressed gas cylinders are

manifolded to hold the compressed nitrogen, hydrogen and residual gases at 3500 psi until the ammonia reactor is activated.

- Ammonia Reactor: A sealed unit containing about 15 pounds of catalyst

generates the ammonia. At the start a small electrical heater is used to initiate the reaction, but once started, the power is turned off. A control valve throttles the gases exiting the unit.

- Outlet Cylinders: Four inverted high pressure compressed gas cylinders

receive the gases at 350 degrees C temperature and contain them until they cool to room temperature. During this time 4 to 5 gallons of ammonia is condensed. The residual pressure in the cylinders is about 800 psi, and the gases are recycled by the gas mixture pump.

- Collector Tanks: A collector tank is located under the inlet cylinders to

catch any additional ammonia that may be condensed. When it is full a valve is opened allowing the ammonia to flow into a second collector tank that receives the ammonia that condenses in the outlet cylinders. When the second collector tank is full, a valve is opened and the ammonia flows into the ammonia storage tank.

12. CONTROL AND INSTRUMENTATION The instrumentation and control computer, measures solar power output, hydrogen tank pressures, ambient temperature, nitrogen tank pressure, inlet cylinder and outlet cylinder temperatures and pressures, and collector tank ammonia levels. The computer controls the electrolyzer, deionizer, air compressors, air drying, hydrogen pumps, shed pumps, ammonia reactor operations, and ammonia collector tank emptying. The system status and key indicators are capable of being monitored via the internet.


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The rack control panel is used to set the subsystem control functions to Auto, Manual or Off, and if in the Auto function, whether power will be collected in the Solar Only or Solar & Grid mode.

- Auto: When in the auto function: Operation is dependant on adequate

solar power availability, and being within the established pressure and temperature limits.

o Either the electrolyzer is powered or one or both air compressors

will be driving one of the hydrogen pumps. o When one or both of the air compressors are on, either the air-

nitrogen pump or the gas mixture pump can also be driven.

There are two power modes, Solar Only and Solar & Grid. When a predetermined minimum preset level of solar power is available, the hydrogen and ammonia related components are automatically powered by Solar Only power (2,500 Solar Watts or greater), or a mixture of Solar & Grid power (1,250 Solar Watts or greater). The instrumentation and control computer measures the power from each of the three solar power inverters and provides a rolling average to the programmable logic controller (PLC) to control the equipment.

If the solar power falls below the threshold watt required level for 20 minutes, the electrolyzer is placed in standby and then after a time period is turned off. If the threshold is below the minimum requirement the air compressor(s), hydrogen, and shed pumps are turned off. This is how the system is turned off at the end of the day.

- Manual: The system operates at full capacity using available solar power

augmented by grid power, regardless of the amount of solar power available. The same pressure and temperature limits are used as in Auto.

- Off: When neither Manual or Auto functions are selected, the

components are turned off or not allowed to operate. 13. TRACTOR The modified John Deere 7810 Tractor is powered by a Hydrogen Engine Center 12.5 to 1 compression ration 9.4 Liter Ox Power Engine. It based on a Ford 460 cu-in, V-8 design (is rated at 150 hp at about 2340 rpm) 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.


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14. 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 hydrogen fueling. Hydrogen is first bled into the tractor tanks, and then the tractor pump used. As an option the tractor can be parked and connected to 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. A commercial ammonia pump with hoses connects the ammonia storage tank to the tractor ammonia tank for ammonia fueling. 15. EMERGENCY STOPS Emergency stop provisions are provided for the electrolyzer, hydrogen, and ammonia pumping or generation:

- On the electrolyzer to shut off the electrolyzer, - Two switches on the rack control panel and on the north exterior shed wall:

one shuts off the electrolyzer, and any related the air compressors, hydrogen pumps, the other shuts off all ammonia generation components, air compressors and pumps.

- On the tractor fueling control panel near the base of the platform stairs to shut off the air compressors and hydrogen pumps.

RAPHAEL SCHMUECKER MEMORIAL SOLAR-HYDROGEN SYSTEM...

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