Patent Publication Number: US-2022228270-A1

Title: Device and method for large scale harvesting of solar energy through hydrogen production

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/959,957 filed Jan. 11, 2020. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     Large scale and cost effective harvesting and storage of solar energy is still an open problem. A number of approaches are being attempted with the ultimate objective of supporting large scale industrially and commercially viable solar energy harvesting technologies which could enable a massive shift away from hydrocarbon fuels. This in turn would reduce the production of greenhouse gas, and thus combat global warming. 
     Adoption of solar power for transportation and industrial usage requires addressing the lower energy density and the inherent unreliability of solar power, which make it less suitable for transportation and industrial usage, unless storage can smooth out the unavailability caused by intermittent nature of incoming solar energy. The low energy density of sunlight requires a large collection area. If large geographical areas are used for solar energy production, then there is a problem of transporting the energy to where it is needed. Transporting the harvested solar energy to the point of consumption additionally expends energy. Thus the effective yield of harvested energy is reduced. Improving the efficiency of storage and transportation is therefore of paramount importance in solar energy harvesting. 
     Among the upcoming non-carbon based fuels, hydrogen is well matched to the existing transportation infrastructure. Given a cost-effective and large scale supply of compressed hydrogen fuel, it is feasible to rapidly migrate out of gasoline and diesel in a non-disruptive manner. Among the recent attempts at extracting oceanic solar energy, extracting hydrogen from water for energy usage, the following are salient: 
     U.S. Pat. No. 9,315,397B2 by Samuel Sivret proposes electrolysis of sea water at depth to create hydrogen and oxygen. A stationary system of pumps and turbines is used to generate hydrogen and oxygen by electrolysis of water. Having a fixed infrastructure approach limits the total energy one can gather from the invention unless a cheap and abundant power supply source is assumed. 
     International patent WO2015163932A1 by Joseph P. BOWER proposes electrolysis of water under pressure within a fixed chamber to generate hydrogen by electrolysis of water. Again a fixed infrastructure approach makes it unsuitable for application in solar energy harvesting. 
     U.S. Ser. No. 01/041,1643 by Smadja et. al. describes floating solar arrays with ability to orient the solar cells to improve the efficiency of photovoltaic generation of electricity. Having moving parts that need continuous solar tracking makes the approach less pragmatic for large ocean environment, which would be required if significant amount of hydrogen has to be generated. 
     U.S. Ser. No. 01/084,0572 by Denis Luz addresses the storage aspect by converting solar energy into compressed hydrogen for later use. However the approach is one of a fixed infrastructure making it cumbersome to gather solar energy from over a large geographical area. 
     OBJECTS OF THE INVENTION 
     Support compressed hydrogen based harvesting of solar energy, thereby making solar energy accessible for industrial and transportation usages. 
     Collect solar energy over large areas by harvesting solar energy falling over the oceans. Use ocean currents in order to minimize the transportation cost. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention, in general terms, provides solar powered hydrogen from the ocean or other convenient water body. A hydrogen generation device floats on the water body surface and has attached solar panels generating electricity. The device is designed to withstand rough ocean conditions and is expected to be away for several months at a time when it generates the solar energy and stores it as compressed hydrogen. 
     The hydrogen production device, has a floating platform with positive buoyancy so that it can carry load of the other constituent parts. The device also has onboard array of sea worthy solar panels. These panels can be retracted into a tucked-away position where they will remain mechanically closed and submerged under the water surface in order to protect them from rough weather conditions. The solar panels directly convert the solar energy into electricity to be used by rest of the device. Optionally, the panels are reflective and have a focusing saw mirror pattern so as to collect the unused reflected solar energy for additional harvesting light energy through a solar panel and harvesting heat energy through high temperature electrolysis. 
     The electricity harvested by the solar panel is routed to an electrolytic cell that operates at a considerable depth under the ocean surface in order to produce the hydrogen compressed at the ambient water pressure present at the depth of operation. The electricity is also optionally used for high pressure high temperature electrolysis in a sealed electrolytic cell. 
     The compressed hydrogen produced by the electrolytic cell(s) is collected in compressed hydrogen storage tanks which also provide buoyancy to the device. The device also has an on-board computer system and electrical motors to do various operational tasks. Tasks include actions like folding up and submerging the solar panels for bad weather or dark conditions, or navigating on the sea surface by operating propellers. These operate either by drawing some power from the on-board solar panels, or by using batteries during dark conditions. The on-board computer will have visual and other sensors and will be designed to both remote control the system as well as to operate it autonomously without human intervention for long periods of time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting embodiments of the present invention are described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale. In the figures each identical or approximately identical component is represented by a numeral. For purposes of clarity not every component is labeled in every figure, nor is every component of every embodiment of the invention shown where illustration is not necessary to allow a person of ordinary skill in the art to understand and build the invention. The figures are the following: 
         FIGS. 1 and 2  show the different side views of the device converting solar energy into compressed hydrogen.  FIG. 3  shows the top view of the same. 
         FIG. 4  shows the top view and the side view of the sealed high pressure electrolytic cell. 
         FIG. 5  shows the open electrolytic cell which operates under hydrostatic pressure. 
         FIG. 6  outlines the hydrocarbon pathway that uses the heated compressed hydrogen for converting waste into useful fuel gases. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The sketch in  FIG. 1  shows an exemplary arrangement of the preferred embodiment for the invention. The device has one or more cylindrical buoys which also serve as Gas Tank [ 10 ] and are referred as such in the remaining discussion. The Gas Tank [ 10 ] stores the hydrogen produced by the device. There is an attachment on one side for the submerged payload which is attached to the buoy. The platform has an upright pole on the other end which rises above the water level and serve as a mount point for the Sealed Electrolytic Cell [ 8 ] (see  FIG. 4 ) as well as commercially sourced radio antennae, sensors, and cameras. 
     One potential embodiment of the platform is in the form of a cylindrical buoy with a buoyancy of 5000 kg. The volume of such a buoy is approximated below by using a cylinder instead of the spherical end of the buoy. Similarly, density of 1.0 kg 1 −1  is used instead of the density of sea water which can vary with temperature and salinity. 
     
       
         
           
             
               
                 
                   V 
                   = 
                   
                     
                       
                         5000 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         kg 
                       
                       
                         10 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         kg 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         
                           1 
                           
                             - 
                             1 
                           
                         
                       
                     
                     = 
                     
                       5 
                       ⁢ 
                       0 
                       ⁢ 
                       0 
                       ⁢ 
                       0 
                       ⁢ 
                       l 
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
     The cylinder can have a radius of 0.8 m which gives the height of cylinder to be 2.486 m. Construction of ocean-worthy buoys is a well developed standardized industrial process. This embodiment proposes to use a buoy made with 10 mm stainless steel sheet with standard processes. 
     The weight of such a buoy is approximated using the surface area of the cylinder and using 8000 kg m −3  as the density of steel. The buoy weighs approximately 1160 kg, and has sufficient buoyancy to carry a payload of 3839 kg, as shown in 
                     TABLE 1                  Steel buoy design (representative)                                 Component   Description with units (SI)   Value                                             Buoy   Volume (liters)   5000.000               Radius (m)   0.800               Height (m)   2.487               Curved area (square meter)   12.500               Flat area (square meter)   2.011               Total surface area (square meter)   14.511               Thickness of steel (m)   0.010               Volume of steel skin (cubic meter)   0.145               Density of steel (kg/cubic meter)   8000.000               Weight of buoy (kg)   1160.849               Carrying capacity (kg)   3839.151                        
Table 1. Positive buoyancy is achievable with a number of combinations of buoy parameters and payload weight.
 
     The entire device is expected to float on the ocean surface while at the same time being dragged in ocean currents by virtue of the drag felt on the Cable [ 11 ] and the Gas Tank [ 10 ]. These devices shall be placed in those areas of the ocean where the ocean currents naturally form a loop. Fortunately, many such ocean current systems exist. Using the ocean current allows one to collect solar power from over a large area as well as to transfer it cost-free to a convenient collection location. 
     In order to keep the device on its desired trajectory, the floating platform also has navigational capability. This is effected either through commercially available on-board computer control, or through commercially available remote control by human operators. This requires propulsion and control, GPS capability, cameras, and other standard navigation and communication devices. Since these are well developed technologies, we will use existing prior art to add these capabilities to the device. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Physical Properties of Compressed Hydrogen 
               
            
           
           
               
               
               
               
            
               
                   
                 Component 
                 Description with units (SI) 
                 Value 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Quantity of 
                 1 atmosphere in N per sq m. 
                 101325 
               
               
                   
                 Hydrogen 
                 Pressure of hydrogen in 
                 400 
               
               
                   
                   
                 atmospheres 
               
               
                   
                   
                 Pressure (N per sq m) 
                 40530000 
               
               
                   
                   
                 Volume of Tank (cubic m) 
                 0.1 
               
               
                   
                   
                 Absolute temp of deep sea (K) 
                 275 
               
               
                   
                   
                 Molar gas constant R (J/kg K) 
                 0.167 
               
               
                   
                   
                 Number of moles of gas in 
                 88133.316 
               
               
                   
                   
                 the cylinder i.e. Volume of 
               
               
                   
                   
                 tank above, as per the gas 
               
               
                   
                   
                 law: n = PV/RT 
               
               
                   
                   
                 Mass of one mole of H2 (kg) 
                 0.002 
               
               
                   
                   
                 Mass in kg of compressed H2 
                 177.666 
               
               
                   
                   
                 in the cylinder 
               
               
                   
                 Buoyancy of 
                 Volume of water displaced by 
                 0.100 
               
               
                   
                 the tank 
                 tank (cubic meter) 
               
               
                   
                   
                 Density of deep sea water 
                 1055.000 
               
               
                   
                   
                 (kg per cubic meter) 
               
               
                   
                   
                 Weight of water displaced 
                 105.500 
               
               
                   
                   
                 The weight already provided 
                 177.666 
               
               
                   
                   
                 by compressed hydrogen 
               
               
                   
                   
                 Effective weight H2 contained 
                 72.166 
               
               
                   
                   
                 in the cylinder (kg) 
               
               
                   
                 Energy 
                 Hydrogen combustion energy 
                 141.800 
               
               
                   
                 content 
                 (MJ/kg) 
               
               
                   
                   
                 Mass of hydrogen in tank (kg) 
                 177.666 
               
               
                   
                   
                 Total energy from 100 L tank 
                 25193.065 
               
               
                   
                   
                 (MJ) 
               
               
                   
                   
               
            
           
         
       
     
     The electrolysis of sea water is done at the ambient deep sea pressure as shown in  FIG. 5 . This allows one to create and store compressed hydrogen without having to expend energy for compressing it. Considering electrolysis at a depth of approximately 4 km, i.e. approximately 400 atmospheres pressure, the Hydrogen created through electrolysis of sea water would be emitted through the Solenoid-Valve [ 6 ] which opens when the hydrogen bubble reaches the bottom of the Gas Separation Ridge [ 3 ]. The valve would close when the water level reaches to the top. The solenoid valve as well as the sensors and control for closing and opening the valve at appropriate levels are commercially available. The released hydrogen has the physical properties as described in Table 2, and is at a compression level suitable for use in transportation or industry. 
     An alternative embodiment allows the electrolytic cell to build up additional internal pressure by forcing electrolysis within a sealed space. As shown in  FIG. 4 , the electrolysis is within a constrained volume. Converting the entire water into hydrogen would compress the hydrogen at approximately 1240 atmospheres pressure as per the ideal gas law at 273K. Using a Pressure Relief Valve [ 2 ], the produced hydrogen is harvested at 700 atmospheres. The sealed electrolytic cell is constructed in such a way that the two Spiral Electrode [ 1 ] spiral around each other, thereby providing increased surface area for electrolysis. Opposite polarity electrodes are separated by a spiral ridge like shape, the Gas Separation Ridge [ 3 ] on the bottom surface of the top lid of the electrolytic cell. Water level is prevented from falling below the ridge line in order to prevent mixing of the gases. When water reaches this threshold, additional water is pumped in through a separate inlet at 700 atmospheres, the opening pressure of the relief valve. This causes the hydrogen to flow out at the same 700 atmospheres pressure through the relief valve until the water level rises to a top threshold level which is chosen so as not to overflow at the normal closing rate of the pumped in water. The pumping of water at high pressure is done with commercially available hydraulic systems, and the high level, low level transitions to drive the water pumping are also done through commercially available control systems. 
     The electrolysis of sea water and brackish water produces chlorine at the positive electrode. Chlorine liquefies at the operating pressure of the cell. Being heavier than water it shall sink and be discharged through the Cleanout [ 5 ]. Continuous depletion of chloride ions makes the remaining solution alkaline thereby suppressing the production of corrosive chlorine at the positive electrode. 
     Yet another alternative embodiment works by harvesting hydrogen at a pressure of 1000 atmospheres and then transferring it into a waste reducing chamber containing ocean plastics or household waste or other carbon rich waste, as shown in  FIG. 6 . The hydrogen is heated, approximately to 700K (430 C or 800 F) by the Inline Gas Heater [ 9 ]. The mixture is turned, exposed to ultra-violet light to encourage reduction reactions which are endothermic and perform better under catalysis and high pressure. The resulting gas is a mixture of Hydrogen, Methane, Methyl alcohol, Water vapor etc along with some inorganic compounds. This mixture is cooled to 300K and then expanded to 700 atmospheres. By the ideal gas laws, the resulting adiabatic cooling results in the gas being cooled to 210K. This cool gas mixture at −63 C and 700 atmospheres pressure is distilled to extract out the methane which ceases to be gaseous under those conditions. This pathway and embodiment would allow the conversion of oceanic plastic and oil spills, mixed domestic trash and other carbon rich waste into methane gas that can be used in place of natural gas for heating and power. 
     The various preferred embodiments described previously for the electrolysis cell assembly can be made further energy efficient by using the waste heat of traditional nuclear or thermal power plants to reduce the need for electrical energy required for electrolysis as well as that required for the thermal formation of methane from organic and plastic waste matter. 
     The Retractable Solar Panel [ 13 ] is attached to the device as shown in  FIG. 1 . The solar panels can be folded and then with a hinge can be turned downwards to go under the water surface when not it use or to protect them from rough seas. This requires the solar panel to have neutral buoyancy, which can be achieved by traditional design methods. The arc of the circle away from the maximum opened state of the solar panels is used to attach Bumper [ 12 ] which will protect the solar panels when they are in a closed downward position. 
     Considering the solar panels of 1000 m 2 , the energy produced and the cost of solar panels are estimated in Table 3 based on specifications of commercially available products. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Energy and Cost of Solar Panels 
               
            
           
           
               
               
               
            
               
                 Component 
                 Description with units (SI) 
                 Value 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Energy Produced 
                 Area of solar panel (sq m) 
                 1000 
               
               
                   
                 Watts per square meter of solar 
                 220 
               
               
                   
                 panel surface (market value) 
               
               
                   
                 Convert to KW/sq m 
                 0.22 
               
               
                   
                 Peak kilowatts at noon sun above 
                 220 
               
               
                   
                 Efficiency correction for non 
                 0.3 
               
               
                   
                 noon and latitude (estimated) 
               
               
                   
                 Average power (KW) 
                 66 
               
               
                   
                 Total evergy per day kWH 
                 1584 
               
               
                   
                 KwH to MJ 
                 3.6 
               
               
                   
                 Total MJ per day 
                 5702.400 
               
               
                   
                 Days to fill cylinder 
                 4.418 
               
               
                   
                 Total cylinders per year 
                 82.674 
               
               
                 Cost 
                 Cost of solar panel household 
                 3.05 
               
               
                   
                 (Dollar per watt peak) 
               
               
                   
                 Cost projected for marine solar 
                 3.75 
               
               
                   
                 panel (Dollar per peak watt) 
               
               
                   
                 Total peak power we have (Kw) 
                 220 
               
               
                   
                 Cost of the solar panels 
                 825000 
               
               
                   
                 (DOLLARS) 
               
               
                   
                 Life of solar panel (years) 
                 15 
               
               
                   
                 (from market values) 
               
               
                   
                 Cost amortized per year ($) 
                 55,000.00 
               
               
                   
               
            
           
         
       
     
     The Retractable Solar Panel [ 13 ] is designed with focusing reflective backing, the Focusing Mirror Surface [ 16 ] so that some of the sunlight falling on the solar panel is reflected back towards the suspended Sealed Electrolytic Cell [ 8 ]. Some of this radiation is converted to electricity by the Overhead Solar Panel [ 15 ] which moves to do approximate solar tracking as indicated from  FIGS. 1 and 2  This allows the use of solar heat as well as photovoltaic electrical power to perform electrolysis of water. An additional benefit of the reflection is that solar heat instead of falling on the absorbing sea water is reflected away, additionally reducing to a miniscule degree the warming of the ocean. The electrical power generated by the solar cells is also transmitted down to the Open Electrolytic Cell [ 14 ] which collects Hydrogen through the Cable [ 11 ] but allows Oxygen to bubble away into the sea water. 
     The device uses currently available electrolytic cell technology for the electrolysis of sea water. Similarly, the transmission of electrical power over 4 km long wires and conversion of voltages to meet electrolytic requirements are also built using standard well known engineering methods. Using 66% as the overall efficiency of electrolysis and power transmission, we arrive at the estimates of Hydrogen production as shown in Table 4. 
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Production of Compressed Hydrogen 
               
            
           
           
               
               
               
               
            
               
                   
                 Component 
                 Description with units (SI) 
                 Value 
               
               
                   
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Electrolytic 
                 Energy efficiency of cell 
                 0.666 
               
               
                   
                 Cell 
                 and electrical transmission 
               
               
                   
                   
                 (assumption) 
               
               
                   
                   
                 Power being used for 
                 43.956 
               
               
                   
                   
                 electrolysis (kW) 
               
               
                   
                   
                 Voltage of electrolysis 
                 2 
               
               
                   
                   
                 Amperes 
                 21,978.000 
               
               
                   
                   
                 Faraday constant C per mol 
                 96,485.333 
               
               
                   
                   
                 moles generated per second 
                 0.228 
               
               
                   
                   
                 Seconds to fill cylinder 
                 386,912.926 
               
               
                   
                   
                 Days to fill cylinder 
                 4.478 
               
               
                   
                   
               
            
           
         
       
     
     Using the data in Table 4 and Table 2, it follows that the given embodiment produces over 12000 kg of compressed Hydrogen per year. Solar panels are expected to be the main cost driver of the device. Given the amortized cost estimated in Table 3, it follows that the Hydrogen production cost is projected to close to be $4/kg, which is the ultimate cost target of the US Department of Energy for Hydrogen economy. 
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 Load Carrying Capacity of Suspension Cable 
               
            
           
           
               
               
               
            
               
                 Component 
                 Description with units (SI) 
                 Value 
               
               
                   
               
            
           
           
               
               
               
            
               
                 Cable 
                 Diameter per cable (mm) 
                 3.5 
               
               
                 Specification 
                 Redudancy number of cables 
                 1 
               
               
                   
                 Radius (mm2) 
                 38.488 
               
               
                   
                 Strength of wire as per spec in PSI 
                 45,000.000 
               
               
                   
                 Pounds per square mm 
                 69.750 
               
               
                   
                 Total strength of wire in pounds 
                 2,684.563 
               
               
                 Weight 
                 Lenght of wire = Depth of operation 
                 4,000.000 
               
               
                   
                 (m) 
               
               
                   
                 Volume of aluminium (cubic meter) 
                 0.154 
               
               
                   
                 Density of Al kg/m3 
                 2,700.000 
               
               
                   
                 Weight of Al wire (kg) 
                 415.620 
               
               
                   
                 Weight in pounds 
                 916.027 
               
               
                   
                 Carrying capacity per wire (lb) 
                 1,768.535 
               
               
                   
                 Carrying capacity per 3.5 mm kg 
                 802.421 
               
               
                   
                 Weight of electrolytic cell, 
                 50.000 
               
               
                   
                 assembly to change cylinder and 
               
               
                   
                 close cylinder when full 
               
               
                   
                 Weight of empty cylider (kg) 
                 60.000 
               
               
                   
                 Weight of hydrogen at 400 atm (kg) 
                 177.666 
               
               
                   
                 Total payload weight at depth (kg) 
                 287.666 
               
               
                   
                 Residual strength/carrying capacity 
                 514.754 
               
               
                   
                 (kg) 
               
               
                   
               
            
           
         
       
     
     The Cable [ 11 ] ( FIG. 1 ) is designed to carry the weight of the Open Electrolytic Cell [ 14 ] as well as the electrical wires and gas carrying pipes which are attached to the cable with ties at regular intervals as is done in similar under water applications. The material used in the table is marine anodized aluminum wire/cable alloy T6061, which is an aluminum alloy used for marine applications. The structural feasibility of the solution can be examined by calculating the load on the wire as shown in Table 5. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, because certain changes may be made in carrying out the above method and in the construction(s) set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall there between.