The road ahead

There are two approaches to the adoption of hydrogen as the prime energy carrier of the future. The first is to extract hydrogen from a readily available fuel like natural gas or petrol. As stated earlier, this is done by a reformer unit. The sage of the green movement, Amory Lovins, claims that a reformer the size of a water heater 'can produce enough hydrogen to serve the fuel cells in dozens of cars'. The great advantage of this approach is that there already exists the infrastructure for natural gas which has the highest hydrogen content of all the candidates for reforming hydrogen. This could equally apply to buildings, with an individual house accommodating a reformer/fuel cell package which would supply both heat and power. In future, garages could reform natural gas on site to make it available at the pump. The downside is that readily accessible gas reserves are diminishing and the UK faces the prospect of buying 90% of its gas from nations on whom it would prefer not to be reliant.

Another problem is that, if there is a substantial investment in a national system involving the reforming of natural gas, there is the danger that this will 'lock-out' the direct use of hydrogen produced by electrolysis. From a renewable energy and environmental point of view the technological 'lock-in' of an inferior technology would be most regrettable.

An infrastructure carrying hydrogen produced directly from electrolysis is the second option. This poses the 'chicken and egg' problem. Manufacturers will not invest heavily in the development of fuel cells until there is the network of pipes to serve a critical mass of consumers. On the other hand, infrastructure providers will be loath to develop a network until fuel cells are cost-effective and have a strong foothold in the market.

Some experts claim that the incremental path to the hydrogen economy is the only realistic approach, arguing that a complete hydrogen infrastructure built from scratch would be prohibitively expensive. This argument is attractive to governments who would be expected to bear some of the capital costs of the enterprise. Others disagree, claiming that converting a natural gas network would not be 'prohibitively expensive' and that there would be economic and environmental costs associated with adopting a compromise solution with its lock-in risks.

As a distributed energy system matures, and PV and fuel cell efficiencies improve, so also will the opportunity for operators of domestic-size renewable installations to direct their electricity to a neighbourhood electrolyser unit with reformer backup to produce hydrogen to feed a community fuel cell which would, in turn, provide the cluster of homes with heat and power.

Such dedicated PV/hydrogen installations already exist. One example is in operation in Neunburg vorm Wald, Germany.

Solar energy offers one of the most abundant sources of electrolysed hydrogen. Deserts flanking the Mediterranean have already been mentioned as the ideal location for parabolic trough or parabolic dish reflectors to produce high-pressure steam to power steam turbines or Stirling engines to create the power to split water. The export of PV and solar hydrogen could transform the economies of some developing countries.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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