Solar Hydrogen Proyect

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Solar Hydrogen Project atNeunburg vorm Wald, Germany

Toward the futureThe Solar Hydrogen Project at Neunburg vorm Wald, Germany

The future of energy supply


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Energy means life and prosperity

Energy is vital to every sphere of human activity. About a third of all the energy consumed bythe world's population is used in the private sector. With their need for heat and light anddesire for mobility, people have come to regard electric power as a matter-of-factconvenience. Transportation and industry account for the other two-thirds of energy used.The more industrialized a region is, the bigger is its per capita energy consumption, leading

to the highly industrialized countries - home to barely 20 percent of the world's population -today spending some 80 percent of the world's total energy input. As the developing

countries grow economically, energy consumption will increase there, too.

Danger for the environment

At the present time, around 90 percent of the world's energy demands is met by fossil fuels,meaning coal, oil and natural gas. Combustion of these fuels generates vast quantities ofcarbon dioxide, CO2, which is now known to contribute to warming of the earth's atmosphere.Reducing the rate of CO2 emissions is desirable in order to diminish the serious impact ofglobal warming, commonly known as the greenhouse effect. Nuclear and water power, bothof which are "clean" as regards CO2, supply about ten percent of the energy used worldwide.

Responsible management of natural resources

Another problem to be faced is the finite availability of fossil resources. If we are to satisfy therising demand for energy in an environmentally acceptable manner and ensure a supply forfuture generations, we must explore new reserves. One direction to be followed is that ofrenewable energy sources, above all solar power. The amount of energy reaching the earthfrom the sun in just half an hour equals an entire year's primary energy converted by maninto heat or electricity. By finding ways to harness this solar energy, we can conserve fossil

fuel resources and protect the environment at the same time.

The sun shines only at times

Meanwhile a whole number of technologies have been developed for utilizing the sun's heatand light. But there is a fundamental drawback to this supply of energy. The sun shines onlyduring the daytime, longer in the summer than in winter and stronger in southern than innorthern latitudes.

Insolation levels in Germany


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Fig. 1

Precisely when and where energy is needed most - at night time, in winter and in the coldnorth - there simply isn't enough direct solar energy to answer the requirements. Moreover,the density of solar energy is lower by comparison with familiar fossil sources. Accordingly away is needed of storing solar energy so that variations in its availability can be balanced outand the supply of energy can be better matched to demand. One possible storage medium ishydrogen, which can be produced using solar energy for subsequent utilization as anartificially generated secondary form of energy.

Supply of insolation energy compared with final energy requirement

Annual trend in Germany


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Fig. 2

Daily variation of global insolationMeasurements at Neunburg vorm Wald, Germany


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Fig. 3

Gas of many virtues

Hydrogen is by far the most common element in nature. It is extremely light and is aconstituent of water and many organic compounds. Being a natural part of the biologicalcycle, it is neutral to the environment. On the technical side, hydrogen possesses a numberof advantageous properties. It can be stored and transported in the form of a gas or liquid orchemical compounds. It burns with a good energy yield, producing water unaccompanied bycarbon dioxide or global warming potential. For several decades hydrogen has been widelyused as a feedstock in industry, where it is manufactured by various methods, mostly fromnatural gas or crude oil. It is also obtained as a byproduct from numerous chemicalprocesses. Hydrogen can otherwise be produced by the electrolysis of water, which involvespassing an electric current through water to dissociate it into its elements.

The Solar Hydrogen Project atNeunburg vorm Wald

Origins

It always takes time for new technologies to establish themselves. Conversion from wood to

coal, from coal to oil, from oil to natural gas and the introduction of electricity have taught usthat such a cycle spans a period of 50 to 60 years. Work on building a solar hydrogen worldmust therefore start today if it is to be in running order by the time fossil fuel supplies neartheir end. Politicians are generally not so inclined to think in terms of such long periods of


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time. Major business companies on the other hand, and particularly members of the energyindustry, are accustomed to planning decades ahead. As a result, the Bayernwerk, BMW,Dasa, Linde and Siemens companies joined forces in 1986 to form the solar hydrogencompany Solar-Wasserstoff-Bayern GmbH (SWB). Dasa left the joint venture at the end of

September 1994 to pursue the idea on its own.

Concept

SWB set itself the task of building, operating and testing a solar hydrogen energy system in ademonstration project which remains unique in the world for completeness and size. Theconcept represents the ideal case of an environmentally compatible energy cycle. Sunlight isemployed to generate electric power in solar cells, the current then being used inelectrolyzers to separate water into its constituents hydrogen and oxygen. Both productgases are stored on site. The hydrogen supply is either burned to produce heat, fed to fuelcell plants to generate electricity and heat, or liquefied for use as motor fuel. Each reactionresults in reconversion of hydrogen to water.

Objective

In a solar hydrogen energy scheme, as elsewhere, it is a long way from the technicalinception to market readiness. The objective defined for the Neunburg vorm Wald projectwas accordingly to improve the system components, test them in interaction with one another

and among other things reduce conversion losses, advance their suitability for practicalimplementation, and develop optimized overall concepts. First and foremost, the aim is tolower the first cost and operating expense, because the system can only compete withconventional energy supplies if it has prospects of being introduced on a major scale. All

Fig. 4 from source: Daimler Benz AG


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these aims are not to be attained by laboratory work alone. Actual field experience isnecessary to promote further development of components and the complete system. SWBtherefore set about installing and linking up the principal components of a solar hydrogenenergy scheme at the Neunburg vorm Wald site.

Organization

Shares in SWB are now distributed among Bayernwerk, which holds the majority of 70

percent, and the three companies BMW, Linde and Siemens, each holding ten percent. Theproject got underway in 1985 with the preliminary planning and is due to terminate after 13years at the end of 1999. The total budget amounts to DM 128 million with the GermanFederal Ministry of Education, Science, Research and Technology contributing 35 percent ofthe costs qualifying for public sponsorship and the Bavarian State Ministry of Economics,Transport and Technology funding 15 percent.

Location

The SWB plant(Fig.5) is situated about two kilometres south of the small town of Neunburgvorm Wald in eastern Bavaria. Grounds of five hectares were purchased to accommodatethe solar generators, the operating building and workshop, a liquid hydrogen vehiclerefuelling station and a multi -purpose building incorporating an information center(Fig. 6).

Public interest in the project is substantial, as reflected in the average of 1,000 visitors to thefacility every month, among them numerous experts from all parts of the world.

Fig. 5


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Fig. 6

Outlook

The project is scheduled to close on December 31, 1999. A final report will be prepareddetailing the valuable experience gained from it to the end. One thing certain even now isthat the project has broken the ground for utilization of hydrogen as an energy medium. Theknow-how accumulated to date has already been put to use in other projects, for instance theMunich Airport Hydrogen project, the megawatt Solar Roof on the exhibition buildings ofNeue Messe Mnchen, fuel cell propulsion for municipal vehicles and Coordination of theBavarian Hydrogen Initiative (WIBA).

Electricity and hydrogen -generated with solar energy

Electric power from sunlight

Solar cells are used to convert sunlight directly into electrical energy, a process known as thephotovoltaic effect. The cells are made from various semiconductor materials, mostly silicon

up to now. They have been a customary source of power in satellites and space stations formany decades. Commonly shimmering in a graphite to blue tone, the panels of cells areassembled into modules mounted on suitable frames which are ideally aligned southward formaximum exposure to the sun. Different types of solar cells have been tested at the SWBproject: monocrystalline cells consisting of thin wafers of silicon monocrystal, polycrystallinecells in which the crystals are variously oriented, and amorphous cells marked by anoncrystalline structure. Advanced solar cell designs of each type have been investigated. Alltold, the cells installed have a capacity of 360 kilowatts, sufficient to supply the electric powerneeds of about 70 households.


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Fig. 7 Outline diagram of the plant

Dissociation of water

The direct current delivered by the solar cells(Fig. 8) - as long as the sun shines - isconverted to be fed into a 220-volt power grid or to be used directly for generation ofhydrogen. This is done in electrolyzers, in which water, which is a compound of hydrogenand oxygen, is dissociated into these two elements by passing an electric current through it.

Fig. 8

Three electrolyzers, each of about 100 kilowatts capacity (Fig. 9), have been tested inoperation. Working to different principles, they are each capable of generating about 25 cubic


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metres of hydrogen per hour. The hydrogen produced by two of the units, and also some ofthe oxygen, is compressed, treated and stored in vessels at a pressure of up to 30 bar (about15 times that of an inflated car tyre). Two large outdoor storage vessels at the site hold 5,000cubic metres of gas. Other storage facilities installed for testing are liquid hydrogen tanks andmetal hydrides, in which hydrogen is bonded to a metallic powder.

Fig. 9

Safety first

Like many other gases, for instance natural gas, hydrogen will readily ignite under certainconditions. Having no color or odor, it is imperceptible to the human senses. A variety ofsafety precautions is needed to prevent formation of ignitable gas mixtures, all of which havebeen duly implemented in the SWB project along with the technical and structural measuresnecessary to exclude ignition sources and prescribed for that purpose. The storage vesselsare sited outdoors, as is the liquid hydrogen refuelling station(Fig. 10).


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Fig. 10

Efficient ventilation is installed in parts of the buildings where gas might accumulate. Allpotential hazard areas are monitored by instruments and controls(Fig. 11) that give earlywarning of any escaping gas. Equipment containing gas is thoroughly purged with nitrogenbefore commencing repairs or maintenance work. Also, all staff have been instructed inappropriate safety procedures. Adequate steps have of course been taken for fire preventionand controlling any possible outbreak of fire. In sum all these precautions have helped toavert any serious incident throughout the projectss twelve-year lifetime to date.

Fig.11


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The versatile uses of hydrogen

Heating and cooling

Hydrogen can be used as a space heating fuel, either on its own or blended with natural gas.In the past, some mixtures of gas including hydrogen (some 50 percent by volume) andmethane (some 25 percent) were commonly known as town gas. Various types of heating

equipment are undergoing tests within the SWB project. A modified calorific-value heatingboiler(Fig. 12, right) has proved reliable in operation, performing excellently especially asregards reduction of atmospheric emissions. Steam generated in the boiler is condensed toyield a further source of energy. Capacity of the boiler is 20 kilowatts, sufficient to heat asingle-family house.

Fig. 12

Long-term tests were also successful with a catalytic heater(Fig. 12, left), in which a blendof natural gas and hydrogen is converted over a catalyst without forming a flame, resulting inrelatively low reaction temperatures below 900 degrees Celsius. The flue gas contains lessnitrogen oxides than that from conventional burners. Flameless catalytic combustion ofhydrogen can also be employed for cooling. An absorption -type refrigeration system(Fig. 13)with a capacity of 17 kilowatts was constructed by converting a conventional air-conditioningrefrigeration unit to work on hydrogen and is successfully used to support on-site coolingrequirements.


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Fig. 13

Generation of electricity

As well as heat and cold, electricity can be generated from hydrogen. The equipment thatdoes the job is a fuel cell plant, in which hydrogen is reacted electrochemically with oxygen toform water, yielding electric energy and heat in the process. This is the reverse to waterelectrolysis. Stated simply, a fuel cell may be likened to a battery that is continuouslyrecharged. The cells of a normal electric battery are discharged when the chemical energy

combined in their "fuel" has been spent. If fresh chemical energy is supplied continuously,the battery can keep on delivering electric energy. This is what happens in a fuel cell byfeeding in hydrogen and oxygen. In principle a fuel cell plant can operate with a variety offuels, for instance hydrogen, natural gas, methanol, propane, butane or gasoline. Except with


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Fig. 15

Motor fuel

Hydrogen can also be used directly as motor fuel in internal-combustion engines, making itan alternative for example to virtually eliminate car exhaust emissions in inner-city traffic.Hydrogen-fuelled experimental vehicles, cars and buses, are already on the road. Beforehydrogen power can generally spread to motor transport, however, automobilemanufacturers have to build production vehicles with the necessary fuel system and

refuelling stations have to be available that are both easy and safe to operate. A filling stationfor liquid hydrogen has been constructed and optimized by SWB at Neunburg vorm Wald. Asan outcome of tests conducted primarily with different fuel-hosecoupling and vehicle tank


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systems(Fig. 16), time for filling a car fuel tank has been cut to less than three minutes.

Fig. 16

Important results of the Solar Hydrogen Project

Technical evaluation

As of the present time, such systems and units as exist for the production and use ofhydrogen as an energy medium are mostly still in the prototype stage. Extensivedevelopment work is accordingly called for from here on. The SWB project is contributing tothe practical groundwork essential for further progress in the components. Numerousworkable recommendations have already been relayed to the manufacturers and users, mostof which have since been put into effect. For example, knowledge of internal electricaldefects occurring in the polycrystalline type of solar generator has prompted themanufacturer to revise the modules. Suggestions have also been brought forward to improvethe assembly and insulation of some models. Following modification, the solar generatorsconcerned generally proved reliable in operation. Revamping of the pressure type of waterelectrolyzer was found to be necessary. Modifications are currently in the process of beingtested. Experience acquired with continuous operation of the alkaline low-pressure

electrolyzer has been good after making a number of early changes. Useful results havecome out of investigating the gas treatment and storage systems. Problems on theseconcerned the compressors and components of the decentralized process control system forthe most part. By and large, work with two of the three heating units tested, the absorption -type refrigeration system and the phosphoric acid fuel cell plant may be termed positive sincethey have been upgraded. Experience is highly promising above all with regard to gradualtransition from the current fossil fuel natural gas to the future energy form hydrogen. Testoperation of the forklift truck powered byan air-oxidized solid polymer fuel cell plant(Fig. 17)has just commenced. Although its capacity is on the short side, the truck is fully usable bothfor experimental purposes and as a working machine. Practical testing of the liquid hydrogenfuelling station for motor vehicles, in the course of which advanced fuel coupling and tanksystems were developed, was marked by success.


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'Fig. 17

Safety issues

Operating and safety considerations, as well as plain economics, make it advisable toconstruct solar hydrogen plants for energy supply schemes as centralized facilities. Likenatural gas or propane for example, the production and storage(Fig. 18) of hydrogenand its

use as energy demand proven safety engineering and optimum attendance by fully trainedpersonnel. Nothing fundamentally opposes the handling of hydrogen by end-consumers on abroad basis.

Fig. 18


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Energy scenarios for the future

Owing to its favorable environmental properties, hydrogen is exceedingly desirable as anenergy medium. Conversion to hydrogen is nevertheless only meaningful in theenvironmental context, if it can be produced using renewable energy sources such as solarpower. In addition to serving as an energy storage medium for balancing the supply ofenergy at appropriate times and places, hydrogen can help to reduce local emission levels

by being used for example as fuel for space heating in densely populated areas and to powerautomobiles. With conditions as they are today, solar-generated hydrogen is still veryexpensive by comparison with conventional energy systems and therefore far removed frombeing economical. There will presumably be no change in this assessment in the immediatefuture. Energy supply for the world's population must be expected to remain rooted in abalanced mix of energy forms for the medium term. To assist the commercial introduction ofhydrogen technology it will be meaningful to make stepwise transition from natural gas as thefossil fuel in use at present to hydrogen. On the technical side this is possible both withstationary fuel cell plants and vehicle power plants. In this way sensible use could be madeof the know-how already available in this field during the gradual build-up of a solar hydrogenenergy world.

Solar-Wasserstoff -Bayern GmbHNymphenburger Strae 3980335 MnchenGermanyPhone +49-89-12 54-40 81Fax +49-89-12 54-40 82


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Information Center ofSolar-Wasserstoff -Bayern GmbHBrnhof 192431 Neunburg vorm WaldGermany

OpenTuesday to Friday10 am to 12 pm1 pm to 4 pm

Arrangements may be made forgroup visits at other times.Phone +49-9672-1882Fax +49-9672-4155

Issue: March 1999

Solar Hydrogen Proyect

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