Hydrogen economy
The hydrogen economy is the concept of energy is in the traded and gewirtschaftet at all levels with hydrogen. It is a concept that should lead to the replacement of traditional structures and is currently the world never realized.
- 3.2.1 High -temperature electrolysis
- 4.1 hydrogen in pipelines
- 5.1 use in the house
- 5.2 use in transport
- 6.1 Definition of Terms
- 6.2 efficiencies in a hydrogen economy
- 6.3 For comparison, efficiencies in the fossil energy
- 6.4 For comparison, efficiencies in electric vehicles
History
For hydrogen
Hydrogen is a secondary energy source, which must be produced from other energy sources. The theory of the hydrogen economy assumes that hydrogen at all levels displaces the current energy sources fully and / or replaced.
The energy levels of a
The ideas go from enforcing the hydrogen at all levels of energy from:
Each of these levels is technically investigated for hydrogen and partially realized in practice.
Producing hydrogen
The world produced quantity of hydrogen from natural gas and heavy oil is about 310 billion m³ STP and about 9 billion cubic meters i.n. in Germany (1999 ). Natural gas and heavy oil are fossil primary energy sources. In the production of hydrogen by means of these substances harmful carbon dioxide is released accordingly. This is contrary to the request by the European Parliament uptake of green hydrogen economy.
A portion of the hydrogen generated as a by-product in the chemical industry, for example in the gasoline reform and the ethylene production. However, it is also produced by-product hydrogen in chlor -alkali electrolysis and the production of coke oven gas by coal gasification. In 1999, the chemical industry worldwide 190 billion m³ STP and in Germany 10 bcm i.n. produced. Most of the resulting by-product hydrogen is used directly by burning on site energy.
The production of hydrogen from the primary biomass energy sources, apart from the effort to produce ( for example, fertilizers, pesticides, etc.), transport and processing / preparation of the biomass, carbon-neutral, because the liberated in the production of carbon dioxide to the atmosphere previously removed by photosynthesis been. This corresponds to the request by the European Parliament uptake of green hydrogen economy.
Hydrogen can be produced from biomass by fermentation or thermo- chemically, eg by steam reforming ( → See also Main article: hydrogen production ).
A large- scale production of hydrogen from biomass does not exist with status 2011. The procedures are mostly still in the stage of development. One example is the project " Blue Tower " in Herten. The proposed plant should produce 150 cubic meters of hydrogen per hour, the majority holder, the company Solar Millennium AG went into bankruptcy in late 2011.
Potential and demand for land for energy crops
→ See also article: Potentials and land use and biomass potential
After the energy scenarios of the Federal Government used to produce biomass surface may 2050 about 4 million ha (2011: 1.8 million ha ) amount, without getting into competition with uses in food production. These are only 24% of today's agricultural land. From this, a primary energy potential of 740 PJ ( 18.5 MJ / kg at 10 t / ha) is calculated.
The example of the yield values of Miscanthus ( 18.5 MJ / kg for up to 20 t / ha) yield a primary energy potential of 1480 PJ / year. Depending on the assumed parameters, the value can fluctuate widely.
Potential of biogenic residues
Biogenic residues from agriculture, landscaping wood, wood residues and unpolluted industrial wood can also be used to produce hydrogen. The potential of biogenic residues is estimated by the Federal Ministry of the Environment to 900 PJ.
Electrolysis
Another possibility is the production of hydrogen from wind and solar power, resulting in favorable weather conditions, but is not accepted by the consumer and elsewhere is not storable ( power-to - gas). This energy would expire, that is, the wind turbines would have to be removed from the network, if it were not converted to hydrogen. Thus, the efficiency in this particular case plays a subordinate role.
This method has been used since 2011 in a pilot project at Enertrag in Prenzlau. Any power not required is converted with a 500 kW electrolyser into hydrogen and thus stands for Berlin's hydrogen filling stations available or is converted into electricity in a hybrid power plant when needed.
Greenpeace Energy delivered since October 2011 also hydrogen from excess wind power is fed in pure form or converted to methane in the natural gas grid.
The Audi AG plans to produce in 2013, in Lower Saxony Werlte hydrogen from wind power. The hydrogen produced is first converted to CNG, to serve as fuel for natural gas vehicles. However, the hydrogen produced can also be used directly in fuel cell vehicles.
High-temperature electrolysis
→ See also the article: The high temperature electrolyzer.
Good efficiency promises Hochtemperaturektrolyse because the consumption of electrical energy decreases with increasing temperature. The high-temperature electrolysis is particularly interesting when waste heat from other processes can be used, eg for solar- thermal power plants. The case is in 2011 but still in the development stage.
Storage and distribution of hydrogen
Hydrogen in pipelines
In a fully developed infrastructure with corresponding quantities but a distribution pipelines will be significantly more energy efficient and cost effective. To this end, much of the existing natural gas network could be used. The natural gas system is suitable for the absorption of hydrogen. Before switching to natural gas, the German gas grids were operated with city gas consisting predominantly of hydrogen.
The storage capacity of the German natural gas network is more than 200,000 GWh and can temporarily store the energy needs of several months. For comparison, the capacity of all German pumped storage plants is, however, only 40 GWh.
There is also sufficient practical experience with hydrogen lines:
- In the Ruhr area via a 240-kilometer hydrogen network is operated for decades.
- In Saxony -Anhalt is a 90 km long, well-developed hydrogen pipeline system of the Linde Gas AG in a region with strong industrial gas demand between Rodleben - Bitterfeld- Leuna- Zeitz.
- Worldwide, there were in 2010 more than a thousand kilometers of water fuel lines. Air Liquide operates 12 pipeline network with a total length of 1200 km
The energy transfer through a gas is done with much less network losses ( <0.1%) than that of a power supply unit ( 8%).
The Ministry for the Environment, Nature Conservation and Transport Baden- Württemberg wants future (2011 level ) support the development of a hydrogen infrastructure.
Energetic use of hydrogen
The most important element is the use of hydrogen fuel cells. It converts the energy contained in the hydrogen in the heat and electricity.
Use in the house
→ See also Article: Stationary use.
In the domestic power generation using fuel cells can be realized as the cogeneration technology, a combined heat and power, which increases the overall efficiency. Since in this mode, the heat production is at the forefront, these systems are controlled by the heat demand, the electrical power generated is fed into the public power grid.
Vaillant has developed a fuel cell heater which can be operated via a reformer with natural gas.
The theoretically achievable energy- related efficiency is about 83%. Refers to the efficiency, as in thermal power plants and combustion engines, common to the heating value, resulting in a theoretical maximum efficiency of about 98%. The system efficiencies, depending on the type of fuel cell is between 40% and 65 %, which is unclear if these are worth burning or heating value related.
Use in transport
→ See also articles: Fuel cell vehicle
In the fuel cell vehicle is generated by the fuel cell electric power, with which an electric motor is driven. The hydrogen supply is done via a pressure tank (eg 700 bar ) can be refueled at a hydrogen filling station. Even in buses, the hydrogen will be tested in practice. The current generation of hydrogen buses (2009) reached 35 kg of hydrogen has a range of around 250 km.
Hydrogen cars are ten times more expensive than an electric car. A hydrogen vehicle is, according to Fritz Henderson ( CEO of General Motors) cost around $ 400,000. Vehicle manufacturers Toyota, Nissan, Mercedes -Benz and Honda have been reduced drastically by its own account production costs for hydrogen-powered vehicles.
With the Mercedes B -Class F- Cell, and two pre-production on the Hyundai ix35 Fuel Cell Electric Vehicle ( FCEV ) ranges from 500 km at maximum speeds of 80 km / h was reached .. In order to prove the everyday suitability of hydrogen drive, Daimler has a " world tour " with several cell vehicles of the B-Class successfully completed. 200 series vehicles of this type were delivered to customers in 2010.
In addition, the rail vehicles have come into the angle of the hydrogen economy with the technique of Hydrail since 2005. As one of the first companies in the Japanese East Railroad Company took for test purposes a hydride locomotive in operation.
Efficiency of the energy chain
Definition of Terms
Cost does not automatically lead to energy efficiency. So, for example, has a coal power plant in the generation of electricity with an efficiency of 30-40 % a poor energy efficiency, it is very cost effective and therefore economically due to the low price of coal.
For example, the conversion chain, well to tank without piping network:
Is not particularly energy efficient from the technical efficiency ago. 1 kg hydrogen costs but in May 2011, only 8 euros. This is the hydrogen price the customer has to pay at the pump, ie inclusive of investments for construction and operation of the hydrogen filling station, but without consideration of the state subsidy and the higher cost of purchasing the vehicle. Should also be noted that mineral oil and hydrogen is currently (2012 ) are treated differently for tax. In hydrogen not petroleum or energy tax is levied.
Thus, the fuel cell vehicle in terms of fuel consumption, despite moderate energy efficiency economical to operate than the vehicle with a gasoline engine, but less economical than the direct electric drive with traction battery.
Even under the Hart report the Nutzenergiekosten when using conventionally produced by steam reforming, untaxed hydrogen relative to gasoline are quite competitive. The expected tax would be offset by higher prices for gasoline. The cited study starts from constant prices for hydrogen production.
Efficiencies in a hydrogen economy
In determining the efficiency of a hydrogen economy the whole conversion chain, from the production of hydrogen must be considered to produce the final energy to the consumer.
The assessment of the efficiency of the sources are very different in part because many procedures are still in the development and practical production experience are still missing. A large-scale application currently does not take place, so that in particular the efficiency figures for hydrogen production (2012: almost exclusively from fossil sources ) must be interpreted as the theoretical maximum values.
The assumed values for the efficiencies were averaged from the fluctuation and may vary up or down in reality quite. The calculated total efficiencies can therefore be only approximate.
In a hydrogen economy speaking, therefore, the energy chain
An efficiency of 0.75 × 0.99 × 0.95 = 0.70.
For fuel cell vehicles, the energy chain results
With an efficiency of 0.75 × 0.99 × 0.88 × 0.6 × 0.95 = 0.37
For comparison, efficiencies in the fossil energy
For electricity from a coal-fired power plant is available with the energy chain
An efficiency of 0.38 × 0.92 = 0.35.
For a fuel cell vehicle with fossil hydrogen production by electrolysis is obtained for the energy chain
An efficiency of 0.38 × 0.92 × 0.8 × 0.88 × 0.6 × 0.95 = 0.14.
For a fuel cell vehicle with fossil hydrogen production by natural gas reformation (currently the default) results in the energy chain
An efficiency of 0.75 × 0.88 × 0.6 × 0.94 × 0.95 = 0.35.
For a battery- powered electric vehicle charging by pure coal - flow results with the energy chain
An efficiency of 0.38 × 0.92 × 0.94 × 0.95 = 0.31. The real power mix in Germany increases the efficiency depending on the proportion of the electricity generators.
For a vehicle with a gasoline engine is available with the energy chain
An efficiency of 0.85 × 0.24 = 0.20.
The comparison shows that the overall efficiencies of a hydrogen economy can be far above those of incumbent fossil energy industry.
For comparison, efficiencies in electric vehicles
When charging with green electricity from own generation results for battery electric vehicles with the energy chain
An efficiency of 0.9 × 0.94 × 0.94 × 0.95 = 0.75, and for electric vehicles with fuel cell with the energy chain
An efficiency of 0.9 × 0.94 × 0.8 × 0.88 × 0.6 × 0.95 = 0.34.
The comparison shows that battery-powered vehicles have the better efficiency. If additional heating / cooling energy for heat / cold generation is needed. This may reduce battery weight and the range of temperature depending on up to 50 %. Also occur during fuel cell vehicle as in vehicles with internal combustion engine in winter mode significantly higher consumption. Due to the higher amount of energy carried, these additional consumption, however, may not work as much on the range like the electric car.
Overall, it is anticipated that both technologies can not compete, but complement each other ( electric car ) and " long distance " ( BSZ- cars) in their specific fields of application " close range ".
Environmental and climate protection
The use of renewable energy is carbon-neutral and zero-emission itself. With the use of biomass is also true in a hydrogen economy. It incurring any air pollutant neither in the gasification to hydrogen even in the use of hydrogen. However, the effort for the cultivation, production and processing of biomass must be considered in an environmental consideration. The use of biomass even includes two options to make the greenhouse effect reversed.
- The storage of CO2 in the subsurface, which inevitably occurs in the production of hydrogen in a concentrated form.
- The incorporation of bio- coke in the field, if you control the gasification accordingly. This makes the fertile farmland and is known as Terra preta.
The elimination of emissions account for the social costs of energy production. These are of the same order of magnitude as the right to be paid energy costs.
2003 feared Scientists at the California Institute of Technology in Pasadena could be due to simulations that release a comprehensive hydrogen economy about 100 million tons of hydrogen into the atmosphere and thereby damage the ozone layer.
According to recent scientific studies of the Forschungszentrum Jülich in 2010, but this effect will be negligible under realistic assumptions. The positive effect by forgoing fossil fuels predominates. Originally, it was assumed that about 20% of the hydrogen from escaping into the atmosphere. Due to technological development, however, now expected to be less than 2% escape. On top of that of its full hydrogen, ozone -damaging effect develops only in the presence of CFCs. With the decline of the CFCs in the next few years, the reconstruction of the ozone layer will prevail.
Accident risk in a hydrogen economy
Is hydrogen, such as gasoline or natural gas, flammable. For technical equipment, the specific properties of hydrogen must be considered. The chemical industry uses hydrogen for over a hundred years in large quantities, so that sufficient experience in dealing with hydrogen exist.
Hydrogen is a very volatile gas due to the low density. Outdoors it can evaporate very quickly. However, real accidents are known in which flammable hydrogen mixtures accumulated at the bottom, because oxygen / hydrogen mixtures with a share of less than 10.5 percent by volume hydrogen are heavier than air and will sink to the bottom. The segregation is not instantaneous, so that up to below the 4- volume percent limit, the ignition remains. When dealing with hydrogen safety and ventilation systems must take into account this behavior.
The pressure tanks in use today hold (as opposed to gasoline tanks) also serious accidents unscathed from. Hydrogen vehicles with pressure tanks can be easily parked in car parks and underground garages. There is no statutory provision which restricts the. In contrast, vehicles with liquid hydrogen may not be parked in an enclosed space, as can form explosive gas accumulations by outgassing.
Criticism
Depending on the selected output requirements and adopted individual efficiencies, energy efficiency is considered more optimistic or more pessimistic. A hydrogen economy is currently implemented anywhere in a big way and the feasibility is controversial. The following statements are disputed: The hydrogen economy is presented as an alternative to the current economy. Proponents of a hydrogen economy highlight the alleged better storability of hydrogen compared to that of electricity. Hydrogen possess the property of a good short -term storage in the form of pressure fluctuations tolerable in a pipeline distribution network ( the pipeline itself, the memory ) and the long-term storage capability ( as is currently stored natural gas ) in the cavities. Required electrical energy can be generated from hydrogen on site using fuel cells with an efficiency significantly the would exceed the German power plants: However, the cited sources for energy efficiency of the fuel cell energy losses do not consider only the conversion of natural gas or hydrogen into electricity into account, however, incurred in the production, storage and distribution of the required hydrogen. Also, the low volumetric energy content is rarely taken into account: "A 40 -ton truck can transport just 350 kg of gaseous hydrogen ," says Bossel, " and even liquid hydrogen is as light as styrofoam. "