3 Turnaround and Refuelling With Liquid Hydrogen
3.6 Losses and Cost Adaption Due to Refuelling With Liquid Hydrogen
3.6 Losses and Cost Adaption Due to Refuelling With Liquid Hydrogen
Figure 3.17: COCs for a 180-passenger aircraft versus the turnaround time; additional dependence on the flight distance and by differentiating the energy carrier from LH2 or sustainable aviation fuel
To classify the calculated COC values, the costs for a comparable aircraft with sustainable aviation fuel produced renewably by PtL are plotted in Figure 3.17. The curves of the different energy sources behave in the same way, but there is an offset between them. This is because PtL requires more energy for production, and thus the fuel price is higher. The price for LH2 in this diagram is assumed to be 29.15 EUR/GJ and for PtL 35.6 EUR/GJ [130]. Thus, the 22 % price difference between the fuels is only reflected in the COCs in a weakened form.
Due to the low fuel price, LH2 has an advantage when considering the COCs. However, considering the DOCs, in which capital costs are also taken into account, would lead to PtL causing the lower costs. This is because the development costs for an LH2-powered aircraft would increase significantly compared to PtL.
3.6 Losses and Cost Adaption Due to Refuelling With Liquid
3.6 Losses and Cost Adaption Due to Refuelling With Liquid Hydrogen The fuel price is based on an analysis of the energy required to produce the fuel bySilberhorn et al. [130]. This investigation results in a LH2 price of 29.15 EUR/GJ. This analysis makes it possible to compare different energy sources regardless of density or calorific value. The conversion of the energy price results in a mass-related price of 3.5 EUR/kg LH2. Including other literature sources, this results in a price range for possible fuel costs of LH2 of 1.0 to 5.7 EUR/kg [130, 91, 36]. A detailed investigation for the LH2 price is not made due to the different production assumptions, such as the location, the process and the energy price.
As a result, losses of LH2 caused by chilling and vaporisation can be added proportionally to a refuelling operation on the fuel price. In addition to these direct losses of LH2, there are also the costs that have to be incurred to transfer the fuel. These influences include the power consumption of pumps or the gas’s cost in a pressure feed system. When a purging process is executed, the cost of the inert gas must also be considered.
To include the electricity price in the costs independently of location, the electricity price is based on the fuel price and the energy required to produce LH2 in an environmentally friendly process. As defined in Section 2.1, renewable LH2 requires specific production energy of 210 MJ/kg LH2. With the fuel price of 3.5 EUR/kg LH2, the electrical energy price results in 0.0167 EUR/MJ or 0.06 EUR/kWh. Therefore, this electricity price is the origin of the further calculation of the costs that arise from the consumption of electrical energy to be able to refuel LH2. The helium required for the refuelling process is assumed to have 22 EUR/kg in the following cost calculation [150].
The following list shows the fixed costs that are accrued per refuelling procedure and are independent of the vehicle type:
• 0.3 kg of helium is required for pressurisation as part of the purging process per refuelling, resulting in costs of 6.6 EUR
• The evacuation of the pipes as the second part of the purging process requires a vacuum pump with a power of 10 kW. There is a cost of 0.0135 EUR per refuelling
• The chilling down of the pipes is estimated to produce an evaporated quantity of 12.4 kg of H2, which results in a cost per refuelling of 43.4 EUR (without recycling)
The independent, fixed costs per refuelling cause a price increase of 0.29 % a refuelling quantity of 5000 kg LH2. In contrast, the price increases by only 0.08 % when the vaporised H2 is recycled in a liquefaction plant.
The additional operational costs for the distribution system, which are also independent of the vehicle type, i.e. independent of pipeline or fuel truck, consist mainly of the pump and the pressure system and keeping the tank pressure constant:
• The pump at the storage tank requires energy of 16.3 kJ/kg for feeding. This performance results in costs of 1 EUR for pumping 5000 kg LH2
• A vaporiser with an electrical power of 140 kW is needed to maintain the pressure for a mass flow of 20 kg/s. This consumption results in additional costs of 0.6 EUR for a delivery of 5000 kg LH2
• The vaporised LH2 for pressurisation amounts to 29.1 kg LH2 for a delivery of 5000 kg.
These losses, therefore, result in additional costs of 101.5 EUR (without recycling)
• Considering the cooling of LH2 in the refrigerator, which is necessary to produce LH2 as a single-phase fluid, there is a cost increase in the fuel price of 0.32 %
3.6 Losses and Cost Adaption Due to Refuelling With Liquid Hydrogen These variable costs for feeding from the storage tank increase the fuel price by 0.59 % without recycling the vaporised H2. With recycling through a liquefaction plant, a price increase is associated with the liquefaction energy of 0.09 %.
The dependent refuelling costs depend on the refuelling method and therefore differ according to the refuelling vehicle.
For a pipeline system with a dispenser as a refuelling vehicle, there are no further costs for refuelling LH2. The dispenser causes no losses and requires negligible electrical power.
There is a wide variation in additional costs for the refuelling truck due to the large number of possible systems that can be used. In principle, all trucks with a compressor and a high-pressure tank to store losses have an electrical cost of 3.78 EUR for refuelling of 5000 kg of LH2. In the following section, the possibility of using a pump on the fuel truck to deliver LH2 is considered first:
• The pump in the refuelling truck has a power of 148 kW, which means a cost of 0.62 EUR for a delivery of 5000 kg. This value is lower than the pump on the storage tank because less pressure head is needed
• Three possible methods are conceivable for maintaining the required pressure in the vehicle tank so that the pump can operate without cavitation:
1. The pressurisation of the tank with helium causes additional costs of 540 EUR in the conservative case and 324 EUR in the optimistic case. The different variants depend on the calculation method; see Section 3.3.1
2. Taking into account a vaporiser, additional costs of 86 EUR will arise without reuse.
With the recycling of the vaporised H2, costs of 13 EUR arise.
3. Pressurising with GH2 from pressurised bottles costs an additional 24.5 EUR to 52 EUR depending on the calculation method, see Section 3.3.1
Therefore, the fuel costs for refuelling with a tank truck and a pump increase between 0.09 % and 3.09 %.
The second way to feed fuel into the aircraft is through a pressure feed system. This system also differs in the choice of pressurant:
1. Tank pressurisation with helium costs between 1285 EUR and 2180 EUR
2. With the pressurisation with GH2 from bottles, costs of 101.5 EUR to 206.5 EUR arise The pressure feed system thus results in a price increase of LH2 between 0.11 % and 12.45 %.
Following only the maximum and minimum increase in fuel costs are represented as follows.
The minimum increase includes no purging and the lowest cost for each method. The maximum increase, on the other hand, includes a purging operation. Table 3.4 shows the methods with the maximum and minimum price increases.
3.6 Losses and Cost Adaption Due to Refuelling With Liquid Hydrogen
Fuelling method Subsystem Minimum increase Maximum increase
% %
Pipeline dispenser system 0.45 1.20
Refuelling truck Pump feed 0.54 4.92
Pressurised feed 0.56 13.62
Table 3.4: Price increase of LH2 depending on refuelling method; split into minimum and maximum fuel price increase related to the purchase price of 3.5 EUR/kg LH2 In conclusion, the pipeline dispenser system has the lowest operational costs, neglecting the investment costs. A refuelling truck solution is therefore also reasonable if the losses are recovered by intermediate tank storage. Otherwise, the high losses are not sustainable. From these results, for the airport infrastructure can be concluded that in a transition phase, fuel trucks are a reasonable choice because the operating cost is not significantly higher, and the investment cost is considerably less. Conversely, if there is a large daily demand, a pipeline system will be cheaper. This variety creates a trade-off between low capital cost and higher operating cost for a fuel truck system and high capital cost and low operation cost for a pipeline dispenser system. However, this break-even point will not be investigated further.
Nevertheless, it must be mentioned that the purging operation accounts for only 0.04 % of the increase. The helium price has the highest uncertainty because helium is only available in a limited amount. Thus, the recycling of helium is significantly important to establish LH2 as a fuel.