If renewables are developed way beyond the vision of current energy policies, at some point in the distant future they could provide high percentages of generation on integrated power networks. That will spark an increasing need for storage. But hydrogen storage will not necessarily be the most practical or the most economic solution. Reversible batteries, such as the Regenysys unit being developed by British power giant Innogy (Windpower Monthly, October 2000), are just as clean.
The EU and US hydrogen strategy blueprints indicate that 2050 could be the point at which it makes sense for renewables generation to be diverted into hydrogen production to power transport (until then hydrogen will come from fossil and nuclear sources). Again, it would require wind energy development to be ramped up to levels several times those of today for that to happen. Meantime, the need for hydrogen fuel may have diminished. By 2050 transport run on fossil fuels is likely to be far cleaner and more efficient than today, while bio-fuels and other solutions may well have made significant inroads.
If the needs of transport do drive development of a system of hydrogen storage and transmission, and if in a specific region wind generation exceeds about 10% of electricity demand, there may be occasions when diverting wind energy into hydrogen production is viable. Limiting wind input (not disconnecting it entirely) to a grid can become the most economic way of balancing supply and demand. Above 20% wind penetration and this would happen more often -- but still not often enough to justify building a hydrogen network specially for the purpose.
By the time 50% wind is reached, things start to look different, but other issues come into play. Demand-side management systems may have developed to the point where they play a key role in keeping the balance. Weather forecasting techniques will have improved making wind output projections more accurate. New storage technologies for electricity could be around. A hydrogen system may also be useful in an integrated energy system, but it will not be the key element, or even essential.