Technological Development Status and Foreseeable Advancement of Hydrogen Production Systems and Fuel Cells and their Application Perspectives

U. Bünger, J. Schindler, L-B-Systemtechnik

Oral Statement for the 50^th Meeting of the Energy Commission, City of Munich, 13^th July 1998

Energy Policy Status

The liberalisation process of energy markets in the U.S., the UK and in Scandinavia gives a good idea which challenges also German energy suppliers will have to face soon. Furthermore, global acceptance of the greenhouse effect gains momentum, accompanied by a growing awareness of the detrimental effects of local pollutants and diminishing fossile energy resources, here especially mineral oil and natural gas.

Coinciding with the above developments we are currently experiencing the beginning of a technological revolution in electricity generation:

• electrochemical energy conversion with fuel cells: abandoning thermal engines will eventually result in significantly higher system efficiencies.

• accelerated replacement of carbon by hydrogen: the trend in fuel use, leading from coal to mineral oil and natural gas, is finally pointing at hydrogen.

One aspect of fuel cells as the primary energy converter of the future has to be specifically emphasized. It is their compatibility with hydrogen on one hand and with today’s carbon based energy carriers on the other. This gives us the unique opportunity to continuously migrate from hydrocarbon fuels such as natural gas to a completely renewable based energy system without major technological disruptions.

Hydrogen Generation

A number of U.S./Canadian, Japanese and European studies present transition and introduction strategies for hydrogen from renewable energies. Alternatives cover a number of hydrogen sources and hydrogen production processes sorted for timely realisation, ranging from

• industrial byproduct and

• well understood steam reforming of natural gas or Kvaerner’s plasma based splitting of methane by electricity producing solid carbon to

• renewable energy based and intensively researched processses such as
  • decentral synthesis gas generation from domestic biomass (dedicated crops and organic residuals such as crop, wood and waste),
  • water electrolysis from hydro, wind and solar energy, and international supply of gaseous hydro-hydrogen by pipeline or liquid hydro-hydrogen by tanker and
  • photosynthetic processes by direct conversion of sunlight.

In the transitition phase both utilization of hydrogen from conventional sources to ease its introduction in an economically feasible fashion as well as long-term sustainable supply options are of equal importance.

Large scale projects (PV in the Sahara desert, large hydro dams in Canada) and international hydrogen supply vectors (global link by tankers from Africa or North America) have scared the public. Decentral hydrogen supply schemes (domestic biomass gasification, wind-hydro concepts) however have proven to be much more sensitive in Europe.

In the German, especially the Bavarian, context biomass gasification has become economically prominent in politics. During the next years local industry will adapt known processes with funds from the local government. Focus will be their qualification for locally available fuels with long-term perspective.

It should however be warned that global food supplies may soon run short, a process that has already started in China. This will significantly increase international food prices influencing the competitiveness of biomass for energy as well.

Fuels Cells and Their Markets

Today’s conventional electricity generation processes deviate the direct electrochemical conversion by thermo-mechanical process driven generator sets. In fuel cells, system efficiency is not topped by the Carnot-number any longer, but by electro-chemical limitations in the stack instead.

Hence, electric efficiencies of fuel cell systems are in the same range as thermal efficiencies. Therefore, a major fuel cell application is for CHPs as well as for power only generation such as in vehicles.

Fuel cells are distinguished by surface oriented conversion processes, in contrary to their volume oriented thermal counterparts. Their efficiency is thus not depending on unit size, resulting in the most important consequence that fuel cell based energy converters are not forced to be large for being efficient. The quality of energy conversion systems will be improved by fuel cells for small and smallest highly flexible units such as portable electronic devices, residential and small and medium industrial energy supply.

Fuel cells will change the face of decentralized power generation in combination with other facilitating technological innovations such as communications (powerline) and automation (load management). Power brokering will be the economic tool to supply electricity with high security in time and at the right place.

Currently, worldwide development concentrates on low temperature fuel cells (PEM) for mobile and stationary use, as well as high temperature fuel cells (SOFC), thermally coupled with small gasturbines. Manufacturing cost reductions are expected to be largest for PEMFC whereas SOFC-GTs are characterized by highest electrical efficiencies of up to 80%.

A good example for the application of stationary fuel cells is the residential energy supply (HEV). The additional key function of this application will be power generation, further to the heat generated in conventional heating systems. This will certainly turn electricity supply systems upside down, and disintegrate current energy market structures. Fuel reformers (e.g. from natural gas to hydrogen), as well as small dc/ac-converters will allow to operate these systems from today’s natural gas grids and integrate them in the electricity supply system.

The success of stationary fuel cells largely depends on their production numbers for mobile applications, and the development of small efficient reformers for hydrocarbon fuels. In Germany commercial production levels for fuel cell based electrical vehicle drives are to be expected already for 2004 (Daimler-Benz A-class). The first small residential energy supply systems may become commercial even before (Vaillant, Hamburg Gas Consult).