What is the cost (in the UAE) using PV technology to produce 1 Kg of hydrogen gas?
The production of hydrogen gas using PV technology entails the electrolysis of water. With the current PV technologies, efficiency rates range from 50 to 80% (Mokri, Ali, & Emziane, 2013). The production of 1 kg of hydrogen, which possesses a specific energy of approximately 40 kWh/kg, requires 48 kWh/kg of electricity. In the UAE, the cost of energy produced from PV technology is 3.00 U.S. cents ($0.03) per kilowatt-hour (Borgmann, 2016). Therefore, the cost of producing 1 kg of hydrogen gas is 48 × 0.03, which is equal to $1.44.
How much solar energy is required to produce 1 Kg of hydrogen with current PV and electrolyzer technologies?
With the current technologies, an electrolyzer working at 100% efficiency needs 39 kWh of electricity to liberate 1 kg of hydrogen (Bossel, 2016). However, it is not possible to achieve an efficiency of 100%. The highest efficiency rate achievable is 80%, which needs 46.8 kWh of solar energy to produce 1 kg of hydrogen.
If an electrolyzer at 100% efficiency requires 39 kWh, what about at 80% efficiency? At 80% efficiency, 20% more energy will be required. Hence, the total energy requirement will be 120%.
(120/100) × 39 kWh = 46.8 kWh.
How much energy can be derived from 1 Kg of hydrogen if converted back to electricity via a fuel cell?
The process of electrolysis:
H2O →H2 + ½ O2 ∆H= 285.83 kJ/Mol (Kumar, 2014).
The reverse process in fuel cells:
H2 →2H+ + 2e– ∆G = 237.13 kJ/Mol
Electrical energy output = 237.13 kJ/Mol
1 Mol of H2 = 2 g
1 kg of H2 = 1000 g
Therefore, the amount of energy that would be liberated from burning 1 kg of hydrogen in a fuel cell = (1000 g/2 g) × 237.13 kJ/Mol
= 118,565 kJ/Mol
Since 1 kJ/Mol= 0.000277778 kWh
The amount of energy liberated in kWh would be 0.000277778 × 118,565 = 32.934 kWh.
The efficiency of the above process is (237.13/285.83) ×100 = 82.96%, which is an ideal process.
However, the highest efficiency achievable is 80%. Therefore, the amount of energy that can be generated by fuel cells is 80/82.86×32.934 kWh = 31.76 kWh per kg of hydrogen.
With current efficiencies and costs of solar panels, is it feasible in this region?
The cost of electricity in Dubai is 0.23 AED/kWh, which is $0.06 per kWh (Dubai Electricity & Water Authority, 2016).
31.76 kWh produced from 1 kg hydrogen is equivalent to (31.76 kWh × 0.06=) $1.90.
From question 1, the cost of producing 1 kg of hydrogen using PV technology is $1.44. The output is higher than the input. Therefore, the process is feasible.
The efficiency of all components of the system
Inputs = $1.44
Outputs = $1.90
Efficiency = Outputs -Total inputs ×100%
Total inputs
Efficiency = (1-9-1.44)/1.44 ×100
= 31.94%
The above calculation does not consider the initial cost of the PV cells, electrolyzers, and fuel cells. The costs of these gadgets vary with the type of equipment and the expected output in terms of energy production. Other factors, such as the amount of solar irradiation and the resistance of the systems, also affect total efficiency. The efficiency of fuel cells also decreases with a rise in temperature and changes depending on the voltage input (Omer, Fardoun, & Alameri, 2015).
References
Borgmann, M. (2016). Largest solar power plant. Web.
Bossel, U. (2006). Does a hydrogen economy make sense? Proceedings of the IEEE, 94(10), 1826-1837.
Dubai Electricity & Water Authority. (2016). Tariff calculator. Web.
Kumar, S. (2014). Clean hydrogen production methods. New York: Springer.
Mokri, A., Ali, M. A., & Emziane, M. (2013). Solar energy in the United Arab Emirates: A review. Renewable and Sustainable Energy Reviews, 28, 340-375.
Omer, Z. M., Fardoun, A. A., & Alameri, A. M. (2015). Economic Feasibility Study of two Renewable Energy Systems for Remote Areas in UAE. Energy Procedia, 75, 3027-3035.