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How to begin with a hydrogen economy? (NOT YET FULLY EDITED)

There are several approaches from which to start off. The principal points are: its

Production
Distribution
Utilisation

Hydrogen Production

The manufacture of hydrogen is already established. Improving the efficiency and reducing the investment cost along the learning curve is under way. Industrial production from fossil material is technically almost mature. This is not the case concerning methods of producing hydrogen from biomass.

Hydrogen Distribution

There are two ways of distributing hydrogen:

Installation of a hydrogen gas grid parallel to the existing natural gas grid.
Utilization of the existing natural gas grid

The installation of a separate hydrogen gas grid to supply petrol stations is being prepared. It is intended to use wind power from coastal regions. This has been estimated by Forschungszentrum Jülich to cost about 29 billion €. It is estimated that hydrogen will be available at the petrol stations at 10€/kg (30€ct/kWh). This would be competitive with present day fuels. For stationary purposes this would be too expensive even without taxation.

Utilizing the natural gas grid for transporting wind hydrogen has already commenced. Several power to gas plants which feed hydrogen into the natural gas network compliant with regulations (DVGW G 262) have been erected or are under construction. This is economical only with hydrogen from biomass because it is cheaper. Conforming to present law (EEG) it would be permissible to operate natural gas CHP plants using virtual hydrogen. This way the reimbursement for CHP power fed into the grid increases from 5,4 €ct/kWh (CHP supplement) to 22 €ct/kWh (renewable energy supplement). The payoff depends only on the amount of energy fed to the grid and not on the composition of the gas. The input of renewable gas (according to DGBW regulations) tends to slightly decarbonise natural gas, that is to say, make it greener. The existing incentives stimulate this trend but they are not a step in the right direction.

Fuel Cells in a Hydrogen Grid

Fuel cells in a hydrogen grid herald a new era. In order to utilize simple membrane fuel cells economically the gas content of hydrogen should exceed 30%. As yet DGBW regulations do not permit this. However, on their own territory local gas providers may ignore them and tolerate pure hydrogen or high concentrations of hydrogen. In this way the advantages of hydrogen fed fuel cells could become manifest. The graph below gives an example.

Operation of simple membrane fuel cells (PEMFC) in an mixture of NG and Hydrogen

For fuel cells running below 300°C natural gas is an inert gas, just like nitrogen. It takes no part in any reaction. That is true in particular for low temperature fuel cells such as PEMFC which operate at around 80°C. When such fuel cells are charged with a mixture of methane and hydrogen, only the hydrogen is converted to electricity. As, however, the efficiency drops sharply at partial pressures below 50mbar (i.e. 5 vol %) this constitutes a practical limit. In the case of CNG filling stations or gas turbines the pressure is mostly much higher so that even lower hydrogen content would be tolerable. The addition of a fuel cell upstream of conventional gas heating systems means they never see mor that 5% hydrogen. All older systems can cope with this.

Should the hydrogen supply fail altogether the original situation would be restored. This would also hold if the provider normally supplies its customers with pure hydrogen.

The gas supplier is free to alter the type of gas supplied. However, he must ensure customer equipment still operates with the new gas. For this reason gas contracting is advisable: the gas supplier procures and installs the equipment at his expense, and offers his customers an attractive heat and power supply. Since hydrogen from biomass costs about the same as natural gas, he can share the pioneering profits from lower electricity prices with the client. The provider could also sell power according EEG tariff.

The annual characteristic of mixed gas with fuel cells.

The operator of a hydrogen plant is interested in running it at constant load. In the case of private homes the provider will supply pure hydrogen in summer and a mixture of hydrogen and methane in winter. In summer the export of power is possible only if the fuel cell is cooled. The electric efficiency will still be better than that of the best gas fed power station. Those who produce power for their own consumption will find that the heat produced will just about match the amount required for warm water, washing machine etc. In winter the provider can increase export of power without loss and facilitate the stabilization of the power grid.

The above outlines a way to enable a sliding transition to the hydrogen economy. This change could also be done from day to another, like when the change from town gas to natural gas was effected some years back, but this would involve higher investment in several hydrogen plants and storage facilities.

Utilizing excess hydrogen from chemical plants could also be expedient because it is normally combusted in power stations instead of methane. From these sites a reliable delivery can be expected. The graph shows two examples:

A genuine hydrogen pipe network has been in operation in the Ruhr area and near Leuna for 80 years now. It could be tapped and extended. Hydrogen from alkali electrolysis plants is even partially green.

Integration of the Hydrogen Economy in the existing Hydrogen Network in the Ruhr

By using hydrogen from biomass both chemically and energetically most chemical products become green. At the birth of the chemical industry synthesis gas was made from coal, today it mainly originates from NG or crude oil, tomorrow it is going to be from biomass.

Hydrogen connection from the Industrial Centre Frankfurt-Höchst

An intra-plant hydrogen grid already exists at the Industrial Park Höchst (Frankfurt/M). The operators are willing to supply their (electrolytic) hydrogen, which owing to the present power mix is already 25 % green, at a small surcharge to the local municipal energy provider Mainova to demonstrate at some objects the advantages of fuel cells. But the provider is turning a deaf ear on this. Presently this hydrogen is being combusted in a power station instead of methane; only a single filling station in the vicinity of the area is being supplied.

updated: 05.07.2014