The two reactor tanks with a total volume of 1.4 liter looked like a solar panel which could be aligned to the sun. But the result was disappointing. The amount of hydrogen production dropped down from hour to hour. It was supposed that the purple bacteria were damaged by the strong radiation. The experiments ran quite successfully, but there is one very important point of critique.
Purple bacteria require an organic substrate for hydrogen production.
In the experiments presented lactate was used. The big goal is to split water into hydrogen and oxygen. All green plants do this. But the hydrogen becomes never existent. The vegetative cell of Nostoc corresponds with the flask containing green algae.