Hydrogen Homestead concept from 2005

Design Considerations for the Full Independent Solar Hydrogen Home System

The people of the planet Earth are entering a new era, to be known in history as the “Transition”. This refers to the time in the 21st Century when the worlds endowment of cheap and easy to use fossil fuel, in the form of oil and coal and Natural gas, reached its half utilized point and ever after became more expensive. The people who wanted to survive started the transition to utilizing Hydrogen as fuel and kept the remaining fossil fuel as a material utilized only for critical uses, not for burning.

The following discussion details what it takes to create a Home that is still modern and powered, yet as independent as the old homesteaders were when six hundred and forty acres a mule and a lot of hard work, were what it took to live an independent and free life.

How much energy do you need to be energy independent?

Electric Power

In Japan the utilities are introducing one kilowatt systems. Several studies in the US have shown that a small house can function on 3 kW, a medium one on 5 kW and a large one on 7-10 kW. A typical US house utility service is 220 Volts @ 100 Amps or 22 kW. That is a lot of power but you would have to turn on every appliance in the house at once to use it all.

Your local utility usually provides a planning chart so you can list all your required loads and create an accurate demand picture for your life style.

The following pages show the basic calculations and pictures of samples of available equipment. The energy users in a home are ranked by power consumption.

1. Space Heat

Check your Utility bills and determine the Natural gas therms required during the coldest months. Ie. November, December, January, February. Turn this into BTUs and convert to kilowatts.

Refer to the Thermal house pages for information on how to minimize the required winter heating power. Hydrogen gas heaters are available.

			HYDROGEN GAS HEATER FROM THE FUEL CELL STORE
				www.fuelcellstore.com

PRODUCT OVERVIEW

Hydrogen Fueled

1. Save on heating costs. The 99.9% heating efficient designs require no outside venting, so all the heat stays in the room.

2. Humidifies dry air adding to the heating effect so you use less fuel.

3. Provide Easy, economical installation, with no vent or chimney required, and a built in pressure regulator, installation is an easy job*. (*Professional installation recommended)

4. Safe and clean burning, Vent Free Gas Space Heaters are design certified by the American Gas Association and meet or exceed all government safety performance standards.

5. A dual purpose safety pilot system protects against oxygen depletion and any interruption in the fuel supply. If either occurs, the gas is shut off to the burner, turning the heater off.

6. Provides heat during power outages. No electricity required, making them ideal as back up emergency heat.

7. Clean, quite odorless operation

8. Easy to use top mounted controls, push button ignition. No matches required.

9. Decorative safety grill and tinted glass

10. Low heat 4,400 BTU's

11. High heat 6,000 BTU's

12. Heater Dimensions 21.5" H x 13.5" W x 7" D

13. 9 ft3 hydrogen per hour

2. Hot Water Heat

NOTE: there are no hydrogen hot water peaking units available yet. The below picture is of an electric type which can be powered by the fuel cell, at lower efficiency.

			www.seisco.com

FOUR CHAMBER RESIDENTIAL MODEL

SEISCO RA-28

(For Potable Hot Water Application)

The RA-28 is the most popular residential model for the whole house and for commercial applications, such as specialty restaurants, convenience stores, hotels, pet grooming shops. A perfect back-up to Solar and Geothermal passive heat recovery systems.

Cost of RA-28 $665.00*Shipping & Handling $15.00

SIZE: 15 1/4"x15 1/4"x6 1/4"
WEIGHT: 23 lbs
CONTENTS: 1 gal of water
HTG ELEMENTS: 4 x 7000w

3. Dryer

Typically 60 Amp service at 220 Volts equals 13,200 watts or 13.2 kW. (During summer months cloths lines are going to come back into fashion). (If gas fired the dryer can be replaced with a Hydrogen gas model (not yet invented)). Use 1 hour per day X 13.2 X 7 equals 92.4 kW-Hr per week

NOTE: dryers built to heat with hydrogen gas are not yet available. The construction is simple enough. A hydrogen pipe with micro holes or a hydrogen pipe with a catalytic tube and an igniter, built inside a heat exchange finned tube, can replace the electric heating element in a typical dryer. Converting the hydrogen to electricity to use in the dryer to heat the element will cause efficiency losses of 30% in the fuel cell and 10% more in the inverter. Better to burn the hydrogen directly to obtain the heat and transfer it to an air flow through a heat exchanger for drying the clothes.

4. Stove Top

Typically 60 Amp service at 220 Volts equals 13,200 Watts or 13.2 kW. If gas fired the stove can be replaced with a hydrogen gas catalytic burner model, (invented by Fraunhofer Solar institute)

Use 1 hr/day X 7 days X 13.2 equals 92.4 kW-hr / wk.

				HYDROGEN CATALYTIC BURNER (FRAUNHOFER SOLAR INSTITUTE)

5. Oven

Typically 60 Amp service at 220 Volts equals 13,200 Watts or 13.2 kW. If gas fired the oven can be replaced with a hydrogen catalytic burner model. Use 2 hr/wk X 13.2 equals 26.4 kW-hr/wk

NOTE: Again, efficiency. Rather than suffer the forty percent loses that converting the hydrogen to electricity and again the efficiency losses of the electric heat in imparting the heat to the food we can achieve the same cooking by direct hydrogen conversion. The oven can use either a pipe with micro holes or a catalytic ceramic coated pipe. Generally the catalytic ceramic coated pipe will be safer as the hydrogen cannot escape the pipe without combining with Oxygen from the air and turning to high temperature steam.

A properly designed oven will have a circulation fan. The high temperature (800 degrees C) dry steam created by the hydrogen catalytic conversion will be impinged directly onto the food being cooked. This direct impingment will transfer the heat at an efficiency several times that of the typical radiated cooking, thus shortening the cooking time by four to ten times and saving both time and hydrogen.

6. Small Appliances

Such items as the toaster, coffee pot, microwave oven, cloths iron, etc.: these items are all heaters and consume approximately 6 Amps at 120 Volts equals 720 Watts. Assume 1 kW each. Use, assume three X ½ hr X 7equals 10.5 kW-hr / wk.

NOTE: These items could all be converted to use some form of hydrogen catalytic heater. However, since their power draw is relatively small and they are primarily portable it seems better to leave them as electrical plug ins. Just choose the most efficient, energy star rated appliances you can find.

7. Electronics

A modern house is full of televisions, surround sound stereos, computers, networks, etc. Each of these information appliances consumes approximately 100 watts, assume a total of one kW. Use ½ hr in morning 5 hrs gives 5.5X 1 X 7 equals 38.5 kW-hr/wk.

NOTE: All modern electronics are built for efficiency in their use of electricity. Especially the portable ones, which have to utilize batteries or micro fuel cells for their power source.

The main thing that you should do is buy Energy Star rated electronics. Also get versions that have wall power conversion modules that can be turned off. Approximately one third of electrical demand growth over the last twenty years has been due to those power conversion modules (wall warts) that are always on. Models with a sleep mode or an off switch will save you a lot of hydrogen over time.

Also the simple thing to do is to have your house wired with a base line turn off switch. When you leave the room, turn off the switch and all your electronics is disconnected, including the wall warts.

A more modern approach is to do like a modern business and install sound activiated switches in every room. If there is no activity in a room for a settable period of time, the wall switch will automatically be switched off, saving the electricity.

8. Lighting

A modern house uses fluorescent bulbs which are approximately four times more energy to light efficient than the older incandescent bulbs. Assuming at least four lights in every room, times three bedrooms , two bath, kitchen, family room. (bedrooms may have two, but kitchens and bathrooms typically have multi bulb fixtures. At 27 Watts power for 100 Watt equivalent light the requirement would be 3 X 2 + 4 X 2 + 5 X 2 equals 24 X 27 or 648 Watts. Add garage and outside lighting for a kilowatt of total lighting requirements. Assuming that all bulbs are fluorescent, if they are still some form of incandescent assume four kilowatts. Use 1kW X one hour in morning and 5 hours at night X 7 equals 35 kW-hr/wk.

NOTE: Lighting technology efficiency has improved dramatically since artificial lighting was invented. The first artificial light was the camp fire, with a directed efficiency of a fraction of one percent. ( the fire lit up the whole cave, providing very little to help a person sew a deer skin tunic or chip a new spear point. Candles, whale oil lamps, and kerosene lanterns were not much better in lighting efficiency.

When Thomas Edison, after ten thousand trials, invented a workable light bulb, the efficiency jumped dramatically, but only to about 15 %. An incandescent bulb puts out seven times as much heat as it does light.

Fluorescent light bulbs, of the long slim tube type, that have been used in business building for the last fifty years were another great improvement in efficiency, up to approximately 50%. In the last ten years the miniature twisted florescent bulbs have become widely available for the home owner.

The next generation in lighting is starting to become available and that is the LED light bulb and strip. These are 20 to 30 % efficient , and are making rapid inroads into the automotive and portable lamp markets, due to their inherent ruggedness, long life, and low heat generation.

		EDISON E27 LED SPOT LAMPS

They are even being built wall size for vast entertainment and commercial displays.

The future generation of lighting is being demonstrated in the development laboratories now. It is the flat LED panel. The promise of this technology is large flat, thin and very efficient panels of almost any size that will glow with light and operate very efficiently.

In the not too distant future lamps and light fixtures and all the hazard and clutter they represent will disappear. The ceiling and walls and literally any surface imaginable will simply glow, providing light where it is needed, when it is needed and at very low power consumption.

		www.dnlabs.com

BENEFITS OF SOLID STATE FLAT LIGHT PANELS  SYSTEMS

1. VERY LONG LIFE (UP TO 50000 HOURS)

2. VIRTUALLY MAINTENANCE -FREE OPERATION (reduced infrastructure, inventory and storage) LABOR-SAVING

3. HIGHER EFFICIENCY (LUMINOUS FLUX/POWER INPUT) COMPARED TO INCANDESCENT AND HALOGEN LIGHT SOURCES

4. HIGHER LIGHT OUTPUT THAT RESULTS FROM USING PROPRIETARY SPECTRA-FLUX 99% REFLECTANCE MATERIAL

5. NO ULTRAVIOLET (UV) RADIATION

6. VERY LOW INFRARED (IR)

7. NO MERCURY ---ENVIRONMENT FRIENDLY

8. LOW VOLTAGE OPERATION (4 TO 24 VOLTS DC) --PERSONNEL SAFE

9. LOW POWER CONSUMPTION AND REDUCED POWER SYSTEM REQUIREMENTS

10. COOL LIGHT BEAM ,SAFE TO TOUCH --PERSONNEL SAFE

11. FULLY DIMMABLE --LOW ELECTRICAL CONSUMPTION

12. BATTERY POWER BACKUP IN CASE OF POWER FAILURE

13. FULLY ENCAPSULATE LIGHT MODULES FOR EXPLOSIVE ENVIRONMENTS

14. FLICKER-FREE --INSTANT LIGHT (ON-OFF) NO DELAY

15. SILENT OPERATION --NO EMI , RF (RADIO FREQ.) OR AUDIO NOISE

16. VIBRATION AND SHOCK RESISTANCE --no glass or moving parts

17. ULTRA COMPACT LIGHT FIXTURE (FLEXIBLE SHAPE DESIGN)

18. MULTIPLE COLORS IN ONE LIGHT FIXTURE --WHITE , RED ,BLUE , GREEN , AMBER.

19. RETROFIT SOLID STATE LIGHTING MODULES IN EXISTING CONVENTIONAL LIGHTING SYSTEMS

20. HIGH POWER PULSE , SCANNING , DIMMING , FLASHING AND AUTO PROPORTIONAL DIMMING (APD) USING PHOTO DETECTORS CIRCUITS ARE AVAILABLE FOR ALL SYSTEMS. (VISUAL SIGNALING TECHNOLOGY (VST))

House Total

House power if every thing is turned on to maximum load at the same time. 13.2 + 13.2 +13.2 +3.0 + 1.0 + 1.0 equals 43.6 kW.

Transportation

Large Car or Truck

The modern world requires that an urban home has vehicular transportation. The new GM Sequel fuel cell car, which is the size of a Cadillac SRX crossover or a Chryslers 300 C and heavier at 4,774 pounds, carries 8 kilograms of hydrogen for a three hundred mile range . This is equal to 148.2 kW-Hr. Use, one fill up per wk.

									www.gm.com/company/gmability/adv_tech/index.html

Small Car or Truck

The smaller Honda FCX, the size of a Chevrolet Vibe or a Toyota Matrix, carries four kilograms of hydrogen or 74.1 kW-hr, for a 200 mile range. There are currently a dozen HONDA FCX vehicles leased out to government entities in three states, and it is a stated goal to lease Honda FCX vehicles to individual drivers by the end of 2005.

Neighborhood Electrical Vehicle

NEV requires 5 kW, Use estimate at 165 kilometers (100 miles) per week at 60 kilometers (35 miles) per hour, equals 2.75 hrs X 5 kW equals 13.75 kW-hr. An example is the Astris Energi, Inc. fuel cell powered golf cart. These are effective for the same reasons that a fuel cell lift truck is, quick five minute hydrogen gas refueling time, instead of overnight battery charging.

			www.astrisfuelcell.com/PR/PR50.php

Automobile Total

148.2 + 74.1 + 13.75 equals 236 kilowatt- hr, required.per week, for one fill up per vehicle per week

Light Transportation (Motorcycle, Scooter, Electric Bicycle)

Motorcycle

15 kW (minimum power rating for driving on California freeways and expressways). Use est. 165 kilometers, (100 miles), per week at 65 mph equals 2.54 hours X 15 kW equals 38.1 kW-hr per week.

Honda and Yamaha are both working on fuel cell motorcycles.

Scooter

3 kW, limited to interior roads at no more than 65 kph (40 mph). Estimates use 65 kilometers per week or 1 hr times 3 kW equals 3 kW-hr per week.

			world.honda.com/news/2004/2040824_03.html
					www.vectrixusa.com

Electric Bicycle

300 Watts. Estimated use 30 km per week at 30 km per hour equals one hour at .3 kW equals .3 kW-hr per week.

A fuel cell bicycle using Italian bike maker Aprilia's frame is displayed at the International Fuel Cell Expo in Tokyo January 21, 2005. Fuel cell by W.L Gore and Company

Shown above: A version of the Manhattan Scientifics' Hydrocycle™ unveiled by Aprilia at the Bologna Motor Show in Italy in December 2000. The bicycle uses the NovArs fuel cell.

www.fuelcelltoday.com

Yard Appliances

Lawn Mower

Rider style, 7.5 kW, (10 hp), Estimated use one hour per week for mowing. Requirement equals 7.5 kW-hr per week.

Hedge Trimmer and Hand Power Tools

These need to be run off a portable hydrogen fuel cell generator of approximately one kilowatt. Requirement estimated at five hours per week equals five kW-hr.

Pool Pump

Typically a .6 kW (1 hp) electric motor is required to c1rculate the pool water to keep it clean. Additionally a 0.3 kW (1/2 hp) motor is required to power the pool sweep. The efficiency assumption is that a solar heat trapping blanket is utilized to heat the pool and it is an outdoor pool and mostly utilized in the summer time. Requirement is .6 kW + 0.3 kW X 4 hrs/day X 7 days equals 25.2 kW-hr /wk.

Hydrogen Powered Lifestyle Summary

Summary	Use	Max kW	kW-hr/wk
HOME	Space heat	20.0 kw	10 X 7 days= 70.0
	Dryer	13.2	1 X 7X13.2= 92.4
	Stove	13.2	1X7X13.2 = 92.4
	Oven	13.2	1 X2 X13.2= 26.4
	Small appliances	03.0	3X1/2X7 = 10.4
	Electronics	01.0	1X6X7 = 42.0
	Lighting (fluorescent)	01.0	1X6X7 = 42.0
Home total		64.6 kW	=375.6 kW-hr/wk
VEHICLES	Large car (GM Sequel)		+ 148.20 kW-hr
	Small car (Honda FCX)		+ 71.40 kW-hr
	Neighborhood EV		+ 13.75 kW-hr
Light Vehicles	Motorcycle		+ 31.85 kW-hr
	Scooter		+ 3.00 kW-hr
	Bicycle		+ 0.30 kW-hr
Total Transportation			+268.5 kW-hr
Yard Appliances			+ 5.0 kW-hr
Pool			+ 25.2 kW-hr
Total hydrogen powered lifestyle			= 674.3 kW-hr/wk

That’s a lot of energy, all which has come from relatively cheap coal and oil and natural gas that nature has saved up for us for the last four hundred million years. But now the cheap fossil fuels are gone and fossil fuel in the future will get ever more expensive. If we want to utilize energy to do the work for us and make home life physically easier, we will have to utilize a new technology to capture energy from nature, store it and make it available when we need it. This new system is the Solar Hydrogen Energy System.

Sunlight

The natural energy available to the individual home owner, in the northern hemisphere, above the tropic of Cancer is approximately 1 kW per square meter, on a sunny day.

EFFICIENCY

If we need 650 kW-hr total per week of point of use delivered energy we must consider the efficiency of the transformations than can make it available to us.

Passive Heat

The first consideration should be to add into the home all of the passive thermal containment that the property allows. Current building codes require R 32 insulation in the walls and R 90 above the ceilings. Also required are double pane windows and leak sealing around all openings. What has not been required has been architecture that provides for natural convection heat traps, such as Tromb , Sun energy absorbing, walls, or basement rock thermal storage, or the many other forms of utilizing the natural convection heat of the Sunlight to both heat and cool the structure. A properly built home can maintain a 72 degree temperature year around, with only a minimum of additional heating and cooling required. Unfortunately only a small fraction of homes were built in the past with passive thermal considerations in mind.

They were built with the assumption that cheap fossil fuel energy would always be available to heat and cool them with brute force power. Times change!

THE PRIMARY FUTURE ENERGY REQUIREMENT: EFFICIENCY!

High Efficiency Heat

If hydrogen is catalytically converted to high temperature steam, such as in heaters or ovens or dryers or stove tops, its conversion efficiency can be 100 percent. We will assume that the appliances are well built and insulated and the utility of the heat energy in cooking food, or heating water or drying clothes or creating space heat, approaches ninety percent.

High Efficiency Electricity

Many tasks are most easily done with energy in the form of electricity. The theoretical maximum efficiency of converting hydrogen and oxygen to electricity and heat is 82%.

The highest practical efficiency of a low pressure, adiabatic, proton exchange (PEM) fuel cell, run at half of its maximum rated power level, is 70%.

Co-Generation Efficiency

Converting our hydrogen to electricity at 70% efficiency means that 30% of the energy in the hydrogen is wasted as heat. In the future expensive energy world, wasting 30% of the hydrogen fuel energy would be completely foolish. With proper heat exchangers built in as an extension of the fuel cell cooling system we can capture most of that heat and bring our total efficiency up to 85-90%. At the same time as we are making electricity to run our lights and turn our motors, we can be heating the bath water and the air in the house.

Re-Generation Efficiency

All hydrogen fuel cell electric hybrid vehicles will be built with re-generation capability built into the motor system. The greatest energy usage in a vehicle is used in getting it up to speed. Where competitive acceleration requires 75 kW (100 hp), cruising down the highway , in an aerodynamic vehicle, only requires 11 kW (15 hp). Accelerating the weight of the vehicle is the energy waster, but once that energy is stored in the moving vehicle, re-generation, on slowing down, can recapture approximately 75% of the energy and store it into battery or Ultracapacitor packs, ready to power the next acceleration.

Solar Conversion Efficiency

Current production solar cell arrays, at best, capture approximately 15% of the incident solar radiation and convert it into electricity. Nano technology based improvements are announced almost weekly in improving the technology of solar array conversion. Potential efficiencies of 30, 40, even 70 % are claimed. However none of these new technologies are yet in production. Currently a Solar Hydrogen Energy System will have to be based on a solar conversion efficiency of 15%, with good maintenance.

Electrolysis Efficiency

The current best home based technology for hydrogen production, utilizing the electrical energy captured and converted from Sunlight by solar arrays, is electrolysis of water. A proton exchange membrane (PEM) electrolyser can convert approximately 85% of the electricity, (future developments are aiming for up to 94% efficiency), into hydrogen.

A functional and efficient PEM electrolysis system must also include efficient filtering and de-ionizing so that the water electrolysed in the system is pure and doesn’t contaminate the electrolyser.

The PEM electrolyser is most efficient at low power loading (1 Amp per square centimeter) and high cooling, (not allowed to exceed 50 degrees C).

Since hydrogen must normally be pressurized for effective storage, either at high pressure of 350 Bar (5,000 psi) or 700 Bar (10,000 psi) or at low pressure 13 Bar (200 psi) for hydride storage, it is most efficient if most of the volume compression is accomplished directly within the electrolyser. This compression adds to the energy required to produce the hydrogen so our total efficiency of the electrolyser system is approximately 80% .

Storage Efficiency

Storing hydrogen is difficult as the gas is so light that a STP cubic meter of it only contains 3 kw-hr of energy. PEM electrolysers are in production that have output pressures of 200 psi, 400 psi, 2000 psi, and under development all the way to 700 Bar (10,000 psi). The system needs the highest electrolyser pressure it can deliver because the mass efficiency of mechanical compression is lowest at the lower pressures and higher volumes. It is more efficient to compress from 5,000 psi to 10,000 psi as the ratio is only two to one, than to compress from STP to 5,000 psi a ration of 333 to one.

Once the hydrogen gas is compressed into the storage tank the pressure energy is available to deliver the gas to its point of use so there is no further loss of efficiency.

Planning the Most Efficient Use of our Solar Hydrogen Energy System

Assuming that we have already done all the standard energy saving improvements to the house, we then start on affordable energy enhancements.

1. Efficient Water Heating

Install a solar water heater. There are several types of Solar water heaters, all of which work by capturing the Sunlight and concentrating the heat energy into water flowing through the system. A passive system capable of providing 80% of the water warming requirement can be installed on the roof and will last as long as the roof itself. The hot water from this system will loop through or utilize an under heater to reinforce the existing electric or natural gas powered hot water system. Heating the water from the water utility delivered temperature, normally about 40F to 50F, depending on the time of the year, up to about 100 F will be accomplished by the solar energy. Only the peak heat, to bring it up to 125 F will require additional energy. Currently it is simplest to just reinforce your current system.

Within a few years, as natural gas and electricity get ever more expensive, water heaters will be made with built in heat exchangers that will capture the extra heat from the Solar heater during the day and from the fuel cell excess during the night, when electricity is being generated. These new design water heaters will also have a built in catalytic hydrogen burner for peak heating, to ensure that the hot water tank is always full of 125 F water.

NOTE: the efficiency of the hot water installation also requires that all hot water delivery piping, running under the house, is fully insulated. The height of foolishness is to struggle to acquire sufficient water heat and then throw the heat away through un-insulated piping, right before it is delivered to the washer or sink or bathtub.

2. Efficient Space Heating

After all the maximum wall and ceiling insulation is installed and every window and door and electrical plate sealed and heavy blinds and drapes are installed, then we add peak hydrogen heat.

Hydrogen catalytic room heaters are available, These systems can be installed directly in the room as their only exhaust is high temperature steam, as are hydrogen systems for forced air heating.

NOTE: safety demands that wherever a hydrogen appliance is installed, especially in any kind of interior space where leaking hydrogen can accumulate against a ceiling, that hydrogen alarms be installed above the appliance. Ideally a venting path will also be installed. See page on hydrogen safety.

3. Electrical Grid Intertie

Since all homes, except the most remote, are tied into the electrical grids and mostly into the natural gas pipe lines, we want to take advantage of that fact and utilize the grid for efficiency enhancements. Most current Solar installations come with an inverter/connector which automatically switches the power generated from the solar installation to feeding the grid. The electric meter runs backwards. This is very advantageous for the electric utility. The utility essentially gets your roof top as free land and you pay for the solar installation.. During the highest electrical demand time of day, from noon to 4 pm, when air conditioning is utilized, your solar installation feeds back to the grid. If sufficient roof top solar installations have been installed, then the utility does not need to build additional peaking power plants. The sum of home solar installations acts as a peaking power plant.

In the morning and at night, when the home solar installation is cooking breakfast or dinner and entertaining itself, the sub peak times, the home is drawing from the grid and the utility is charging high rates and making lots of money. Only a large solar installation of seven to ten kilowatts will provide sufficient power to reverse the meter sufficiently to net zero the home electrical requirement.

Once we have a Solar Hydrogen Energy system of sufficient size installed, the cost equations can be reversed. During the high sun parts of the day our home system is powering the home air conditioning and storing any excess solar energy as hydrogen. During the morning and night the home gets its power through the fuel cell. In this way the home makes its own power at the peak rate time and also makes its own power at the sub peak times. The grid is still available for back up, in the case of long term cloudy weather, but the home powers itself during all the peak times and keeps the grid power cost as low as possible.

In the past, in the era of cheap fossil energy, such a solar system consideration was too expensive and not required. In the future of ever higher fossil energy costs, a solar system to reduce peak power rates will be an absolute requirement to keep a home or business building energy competitive.

Efficiency: Basic System Power Requirements

Hydrogen power will always be expensive and must always be utilized in its most efficient form. The requirements to utilize hydrogen, through catalytic transformation to high temperature steam, for peak heat, from our initial requirements list, are summarized in the following table.

Space heat	70.0 kw-hr/wk
Hot water (bathing, dish and cloth washing)
Dryer	92.4
Stove	92.4
Oven	26.4
Total	281.7

We will include our vehicles in this list. Hydrogen has to be delivered to them in gas form. The fact that they convert the hydrogen to electricity with their on board fuel cells before they use it doesn’t count against the house requirement.

Large car	148.20
Small car	71.40
Neighborhood EV	13.75
Motorcycle	31.85
Scooter	3.00
Ev bicycle	0.30
Yard appliances	5.00
Total vehicles	241.65 kW-hr/wk
Total (all)	554.7 kW-hr/wk is most efficiently delivered as hydrogen gas.

Delivered as electricity

Small appliances	10.4
Electronics	42.0
Lighting (fluorescent)	42.0
Pool pumps	25.2
Total	119.6 kW-hr/wk most efficiently delivered as electricity.

We assumed that the efficiency of our fuel cell conversion was 70%. The second requirement is to determine our peak load requirement. 119.6 / 7 equals 17.085 kW-hr /day. If we assume its party time and all of the electrical load is running at the same time we must summarize the dynamic electrical power requirement.

Small appliances	3.0 kW
Electronics	1.0 kW
Lighting (fluorescent)	1.0 kW
Pool pumps	1.0 kW
Total dynamic requirement	6.0 kW

Therefore our fuel cell must be sized at 6/0 kW/0.7 (conversion efficiency) equals 8.57kW to deliver 6 kW of electricity and 2.57 kilowatts of low grade heat, ( 80 deg C or 176 deg F). If we assume an 80% efficient transfer through the fuel cell heat exchangers we can add 2 kW of heat to the hot water supply.

Since the fuel cell has to send its power through an electrical inverter (DC to AC) to get it to the home in a standard useful form we must also divide our 8.57 kW by 0.9 (inverter efficiency) to get 9.5 kW as the minimum size for our fuel cell.

We want to run the fuel cell at approximately half of full load for maximum efficiency so we need at least a 20 kW output fuel cell.

This oversized fuel cell will also allow for some future expansion as homes have historically added additional power requirements.

Size of the Electrolyser

Our estimated requirement for hydrogen can be summed up.

Space heat, water heat, and major home appliances	281.7 kW-hr/wk
Small appliances and electronics	170.85
Vehicles	241.65
Yard and shop tools	10.00
Total	704.2 KW-hr / wk of H2

The electrolyser is ideally only going to be powered when the Sun is shining so that we are living off of nature’s bounty. In the northern hemisphere, at the latitude of San Francisco we benefit from a year round average of Sunlight or approximately five hours per day. Therefore the electrolyser must be big enough to produce 704 kW-hr of H2 in five hours X seven days or 35 hours equals 20.12 kilowatts of electrolyser function.

The electrolyser, including water filtering and H2 compression will at best be approximately 80% efficient.

Any sunlight power generated in excess of the five hour average, like during the summer months, can just be pumped back into the grid. Eventually the utilities will have to pay for the excess power.

Sizing the Solar Array

The solar array must be large enough to power the electrolyser at its peak power of 20.12 kilowatts adding it’s 80% efficiency requirement or 20.12 / 0.8 equals 25.15 kW of Solar Array output required.

Since the Solar incidence at the latitude of San Francisco is approximately 1 kW/Meter squared and the efficiency of the current Solar panels is at best 15%, we will need 25 meters square / 0.15 equals 166.66 meters square of solar array or an area of 10X10 meters plus an additional array of 10 X 6.6 meters.

There are two easy places to place a Solar Array. Either on the roof top on a south facing roof slope or against a fence line in the back yard.

Designing and Sizing the Electronic Controls

Choosing the Solar array system voltage has many ramifications. There are four main system components that need to be designed for the same voltage.

1. The solar array itself. (A typical solar panel is organized for 12 V with a 17V open peak voltage). So a typical array can be organized for 24 V or 48 V.
2. The control of the electrolyser. If the electrolyser is organized as a serial stack then approximately 2 Volts will be needed per layer to drive the electrolysis reaction. If the Solar Array input to the system is at 48 Volts, then the PEM electrolyser stack would be 24 layers high. A high stack can be advantages as the area requirement for efficient electrolysis, approximately 0.8 Amps per square centimeter ( 5 amps per square inch), would result in active layer areas of approximately 671 centimeters square (104 inches square).
3. The grid inverter of 25 kW capacity so that the entire Solar Array output can feed back to the grid and make the electric meter dance in reverse.
4. The 25 kW switch, which can switch the power flow from the grid intertie inverter and feed it to the electrolyser whenever the hydrogen storage tanks show a preset depletion percentage. Once the tanks are full the switch immediately returns any excess power generated to the grid intertie inverter and feeds it back to the grid.

Determining the Volume of Hydrogen to be Stored

We determined that the hydrogen usage requirement was 704 kW-hr / week. Divided by seven equals 100.6 Kilowatt hours per day. However to be safe we need to have sufficient storage to last for a whole week without Sunlight. After that we will need to tap the grid for our electrolysis requirement to create hydrogen.

Hydrogen gas contains approximately 3 kw-hr per cubic meter, therefore 704 kW-hr divided by 3 equals 235.67 cubic meters of hydrogen storage required. A tank of 235,67 cubic meters would be very large, but a one meter cubed tank that could hold all 235.67 meters cubed would be quite feasible.

Designing and Sizing the Hydrogen Storage Tanks

The main criteria for the hydrogen storage system are cost and safety.

Hydride

The safest system is to store the hydrogen in tanks filled with hydrogen hydride. Hydrogen hydride is a material that reversibly bonds the hydrogen atoms to itself electrochemically. Typically hydrides have to be cooled as they are absorbing hydrogen and heated to drive it off again. The biggest virtue of hydride is that it can be operated at low pressure. Even if the hydride tanks were ruptured, by an earthquake or an act of terrorism, the hydrogen would not escape, unless the hydride material was heated. A hydride tank has to have secondary systems which will automatically cool it when charging and heat it for discharging. The most commonly utilized hydrides are Iron-Titanium hydride and Nickel-Lanthanum hydride both of which can charge and discharge close to room temperature. A hot and cold water circulation system, or a reversible heat pump system will work.

The Iron-Titanium hydride will hold hydrogen equal to nearly 900 times its volume at a rate of approximately 2% by weight. Therefore 235.67 cubic meters of hydrogen gas could be contained in 0.262 cubic meters divided by 0.02 equals 13.1 meters cubed of Iron titanium in a tank.

Pressure Tanks

The second method of storing the hydrogen is in strongly constructed tanks, typically made of a ultra high density poly-ethylene liner, wrapped with many layers of epoxy impregnated carbon and Kevlar fibers and further protected by a resilient covering. The best pressure tanks today have been certified to operate at 700 BAR (10,000 psi ) for use in automobiles.

One cubic meter of hydrogen at STP (standard temperature and pressure) fills one cubic meter at 1 Bar (14.7 psi). In order to shrink the required gas hydrogen into the preferred one meter cubed tank we must compress it 237.65 times or 237.65 Bar (3493.5 psi).

If our electrolyser can deliver the hydrogen gas at that the net pressure of 3500 psi then we just need a single cubic meter tank or an array of smaller tanks that sum up to a capacity of 1 meter cube.

The pressure tanks require several safety devices, such as one way loading valves, step down pressure regulators, blow out diaphragms, and leak proof piping.

Which storage system is safest and most cost effective has yet to be determined, Both types are making rapid progress in development as the requirement for hydrogen storage on board vehicles gets ever more critical.

Summary

We have the outline of a Solar Hydrogen Energy System of twenty five kilowatts, that can power a home, vehicles, and all the toys imaginable and have all of them operating at once.

The core determination is the cost. None of the components of the Solar Hydrogen Energy System, except for Solar Arrays, are currently in production. We will keep compiling this information until it is possible to buy all of the components required to build your own SOLAR HYDROGEN ENERGY SYSTEM.

John Gotthold - Feb 2005