People are looking for ways to efficiently produce green hydrogen in order to store electricity for longer periods of time. Current methods such as batteries are not the most suitable for long-term storage. But hydrogen has its problems, and although it is one of the solutions to the volatility of renewable energy sources, its problem is that a huge amount of energy is lost here. E.g. in the case of electric cars, the battery one will travel 2-3 times the distance on electric energy, which is driven with relatively small losses by the battery, than if the same electricity is used to produce hydrogen and then electricity for a hydrogen car. However, hydrogen might not be a bad solution, even if it is inefficient, as a solution to an excess of energy (which will occur with RES in certain situations as well as a shortage). Methods of hydrogen production that do not “use electricity” could theoretically make sense. However, it also uses a new cogeneration method that was introduced and tested by the Ecole Polytechnique Federale de Lausanne (EPFL). The efficiency of hydrogen production does not impress, but at least it is not the only thing it produces.
At EPFL, they built a giant 7-meter parabola with an area of 38.5 m2, which was equipped with a 2-axis tracking mechanism turning it towards the sun. It concentrated the light in one place, which was a reactor with a CPV module (concentrated photovoltaics). Electrolysis took place here, and the result was not only hydrogen, but also oxygen (which will be used, for example, for medical and industrial purposes) and thermal energy. The problem is that the system will give the most heat in the summer, when it is least needed and vice versa.
The system was tested for 13 days (4 days in August, 5 days in February and 4 days in March). And what were the results? Let’s start with thermal energy. The maximum power achieved was 14.9 kW (the average was 10.6 kW) and during these 13 days (we remind you that 2/3 of the test took place at the end of winter) the system generated 679 kWh of thermal energy. As for hydrogen, the maximum power achieved was 2.9 kW, which corresponds to 1.26 grams of hydrogen per minute. In these 13 days, 3.2 kg of hydrogen was produced, which would be enough for a hydrogen car to travel about 310 to 320 kilometers. That doesn’t sound very encouraging.
If we had solar panels with an area of 38.5 m2, they could produce approximately 7.5 MWh of electricity per year without the tracking system, a little more with it. A 40% increase is usually reported for 2-axles, let’s be more pessimistic and expect a 33% increase and 10 MWh. This would be enough for a regular electric car with a consumption of 18 kWh/100 km and taking into account losses during charging (say 24 kWh/100 km in total) to cover more than 41 thousand km. If we assume that the 3.2 kg of hydrogen from the 13 days of summer and midwinter is representative of the average 13 days of the year, then it would produce about 90 kg of hydrogen per year. For that, a hydrogen car could drive only about 9,000 km (if we were to say that the tested days do not represent average ones and it should be more, it would still be somewhere around 10,000 km or slightly above this value). On the other hand, with this solution we also get thermal energy and oxygen for industrial purposes.
2023-04-26 16:16:29
#Production #hydrogen #oxygen #heat #solar #dish #minute
