The Hydrogen Grand Challenge

More than 90% of the world’s growing energy demand is satisfied by fossil fuels (BP Statistical Review ..., 2015)1. One consequence of the unrestrained use of this technology is the continuous increase of the CO2 level of the atmosphere2. There are also the challenges associated with the limitations of the corresponding resources (Hubbert, 1956; BP Statistical Review ..., 2015). Climate change as a consequence of the growing CO2 level (see text footnote 2, ESRL Global Monitoring Division, 2015) has been identified as one of the most critical challenges facing mankind and requires immediate action: “The Paris Agreement aims to strengthen the global response to the threat of climate change, ( ... ) by low greenhouse gas emissions development, in a manner that does not threaten food production” (United Nations Framework ..., 2015). How to reach the corresponding significant reduction of CO2 emission by 2050 is not defined in this document, but it implies that mankind must transform its energy technology from a fossil to a renewable basis. Numerous studies and publications have indicated that the sun’s energy and its derivatives (wind, water) are by far sufficient to supply world’s energy demand (see, e.g., Smalley, 2005; Züttel et al., 2010); but the large daily and seasonal power variation of renewable energy is an additional complication for a wide spread replacement of fossil energy by renewable energy. This difficulty is drastically demonstrated by the economic crisis of some electricity companies (How to loose half ..., 2013), which cannot cope with the growing but strongly varying supply of renewable energy while maintaining the public mandate of a safe and continuous electricity supply. Large scale daily and seasonal energy storage is thus urgently needed to make the transformation toward a renewable energy society possible. Various technologies are under discussion including mechanical storage (fly wheel, pumped hydroelectricity, compressed gas storage, etc.), and electrochemical storage (batteries). Here, we do not want to diminish the potential of these storage possibilities but highlight the one of energy storage by the production of chemical fuels such as hydrogen (Schlapbach, 2009). One argument is the sheer size: seasonal energy storage for northern countries means the storage of roughly 50% of their total annual demand: with an approximated consumption of 10 kW per capita, this corresponds to 158,000 MJ to be stored in 87,600 kg Li-batteries, or by 3285 kg fuel oil (diesel) per person and year. Apart from technical challenges, these numbers illustrate another important issue: many house holders in Europe are indeed used to store several 1000 l of fuel oil for heating. Changing the energy carrier hydrocarbons implies that the corresponding infrastructure supplying more than 50% of the world’s energy has to be replaced (pipelines for oil and gas, fuel stations, end user installations, the automotive and aviation industry, market models, etc.). Alternatively, the existing infrastructure could be used in accordance with the ambitious Paris agreement (United Nations Framework ..., 2015), if the hydrocarbons are produced from renewable energy. This is the great challenge (Smalley, 2005), which may be partly overcome by tackling the Hydrogen Grand Challenge as described in the following.