# Probabilistic Analysis of Low-Emission Hydrogen Production from a Photovoltaic Carport
## 5 Discussion  
The probability of the photovoltaic systems generating individual levels of monthly energy production (Figure 12) can be easily converted into the probability of low-emission hydrogen production. However, this requires adopting certain initial assumptions which are listed as follows:  
1. All energy produced by the photovoltaic system will be used to produce hydrogen. For this purpose, it is necessary to use an energy storage device that is able to accumulate excess electricity and use it to power the electrolyzer during periods of lower sunlight or at night. 2. To produce 1 kg of hydrogen, 50 kWh of electricity is needed. This is a significant simplification because it results from the efficiency of the entire hydrogen generation system. However, it is very useful in quick and approximate calculations. 3. The low-emission hydrogen generation system operates reliably. All system components operate with maximum efficiency and do not fail. Under normal operating conditions, certain periodic downtimes related to inspections and maintenance procedures in the operation of the entire system should be expected. 4. No costs associated with compressing hydrogen to pressures of 350 or 700 bar are included. The probability of producing a specific monthly expenditure of low-emission hydrogen using the energy from the photovoltaic systems is shown in Figure 13. Low-emission hydrogen generation systems powered by 6.3 kWp peak photovoltaic systems are able to produce between 4 and 20 kg of low-emission hydrogen per month. Of course, the probability of producing a specific expenditure of hydrogen is higher in Italian conditions and is a direct result of the production of higher monthly energy quantities. At this point, it is necessary to discuss the possibilities of hydrogen fuel cell vehicles currently on the market. The capacity of the three hydrogen tanks in the Hyundai Nexo (Seoul, Republic of Korea) is 156.6 L, and they can hold 6.33 kg of hydrogen. Refueling them takes only 5 min. This amount of hydrogen gives a range of 666 km in the WLTP mixed cycle (in urban mode 0.77 kg/100 km, outside the city 0.89 kg/100 km, average consumption 0.84 kg/100 km). The average hydrogen consumption in the Toyota Mirai (Toyota, Japan) is 0.79-0.89 kg/100 km (also in the WLTP cycle). The car's range is approximately 650 km. Therefore, it can be stated that the compared hydrogen vehicles have almost identical hydrogen consumption, which translates into very similar ranges on a single refueling with  
Figure 12: Probability of generating particular energy levels per month by photovoltaic systems with a peak power of 6.3 kWp located in Poland and Italy. hydrogen. For further calculations, we will assume a hydrogen tank capacity of 6.33 kg and a vehicle range of 650 km. Taking into account the possibilities of producing low-emission hydrogen, we are able to state that the monthly hydrogen expenditures produced in the summer period amounting to 16 kg/month and even 20 kg/month in the case of Italy are able to provide monthly ranges of hydrogen vehicles amounting to 1643 km and 2054 km, respectively. The total amounts of energy produced annually by the tested photovoltaic systems located in Poland and Italy can be translated into the following annual ranges of hydrogen vehicles: for Polish conditions, 13,043 km, and for Italian conditions, 17,537 km. More advanced modeling methods can be used in subsequent stages of projects related to hydrogen production from renewable energy. Measurement data from real objects in the form of photovoltaic carports and hydrogen electrolyzers can be used to create physical models of these objects or to model their performance using recurrent neural networks. Models generated in this way can be used in dynamic modeling of hydrogen production in various scenarios of energy production from renewable energy sources. The input to the low-emission hydrogen production system can be the instantaneous power generated by the photovoltaic system.