The scramble for cheap green hydrogen. Tough competition to produce more efficient electrolysers

Abstract

Finite fossil fuel reserves and the ambition to reduce greenhouse gas emissions have led to a renewed interest in alternative and sustainable forms of energy generation. Hydrogen from solar energy is a promising technology, producing energy from an abundant source. The storability of hydrogen is attractive, because it helps to overcome the intermittent nature of most renewable forms of energy. But how does solar hydrogen compare economically to other forms of solar energy? This study identified photoelectrochemical hydrogen technology to have potential to be used as part of a distributed energy resource and provide combined heat and power to residential customers via fuel cells. Since the conversion chain via hydrogen is less efficient than direct use of photovoltaic electricity or heat from solar thermal sources, the technical advantage rests with the storability and subsequently higher utilisation of hydrogen energy. In order to answer the question “under which conditions solar hydrogen may be economically viable”, a techno-economic model has been developed. Temporal resolution of thermal and electrical demand for a residential dwelling throughout the year is used to assess the level to which solar energy can be used to displace grid electricity and natural gas. It has been found that storing hydrogen can indeed add value to a solar based installation, if the installed capacity is sufficiently large. Further, the model established the highest economic value for a combination of photovoltaic, solar thermal and solar hydrogen, giving rise to the suggestion that solar hydrogen devices should not be developed as pure hydrogen generators, but that a poly-generation approach, including some electrical and thermal output, may be favourable. The optimum mix depends on a range of parameters, including the total size of the installation.