Stack cost

Typical service life and stack costs are reported in Table 6.5. 

Fuel Cell Catalyst OT, °C Carbon Tolerance Life Demonstrated, hr Stack Cost, /kW... 

The main difference in SOFC stack cost structure as compared to PEFC cost relates to the simpler system configuration of the SOFC-based system. This is mainly due to the fact that SOFC stacks do not contain the type of high-cost precious metals that PEFCs contain. This is off-set in part by the relatively complex manufacturing process required for the manufacture of the SOFC electrode electrolyte plates and by the somewhat lower power density in SOFC systems. Low temperature operation (enabled with electrode supported planar configuration) enables the use of low cost metallic interconnects which can be manufactured with conventional metal forming operations. 

While the stack, insulation and stack balance in this simple-cycle system is a key component the balance of plant is also an important factor. The stack cost again mainly depends on the achievable power density. Small systems like these will likely not be operated under high pressure. While this simplifies the design and reduces cost for compressors and expanders (which are not readily available at low cost for this size range in any case) it might also negatively affect the power density achievable. 

This configuration has the potential to yield a very competitive cost of electricity. For example, for a fuel cell stack cost of 300 to 400/kW, it is estimated that the COE would range from 3.5 to 3.9 cents/kWh (Assuming 20% equity at 16.5%, 80% debt at 6.3%, and a levelized carrying charge of 0.12.)... 

The main differences in high-temperature fuel-cell stack cost structure relate to the fact that they do not contain high-cost precious metals, on the one hand, and that they demand more complex manufacturing process, on the other. It must be noticed therefore, that, the fuel-cell stack is, in many cases, responsible for less than one third of the total capital cost of a fuel-cell system, and that a large portion of the total cost is caused by fuel pretreatment (reforming, cleaning etc.), plant control, and power conditioning. For small-scale SOFC systems, the cost of the stack is of the order of 40-45% of the total cost. 

Table 3.9. Estimates of future PEM stack costs at a cumulative production of 250,000 MWe/a (Tsuchiya, 2004)...

D Small series cost is reflected the current 85-kW PEMFC stack cost is about 10000 euro (with -2500 euro projected for 2025) (Sorensen, 1998 Tsuchiya and Kobayashi, 2004). 

Including all types, stacks cost in normal times from 1.50 to 4 per boiler horsepower in large sizes. 

The factors influencing platinum loading were assessed to develop an estimate of future fuel cell stack cost for reformate and hydrogen systems. Projections of minimum platinum requirements were estimated based on an analysis that considered ... 

The cost of non-active materials (gas diffusion layer, membrane, and bipolar plates) dominate stack cost at very low platinum loadings, while ohmic losses limit the benefit of increasing platinum loading beyond some point. 

The influence of platinum loading on overall stack cost will be discussed using a simple cost model based on a recent cost analysis by DoE. 

Stack and system cost for automotive PEFC are analyzed on a regular basis by the U.S. Department of Energy. At a production rate of 500,000 systems per year stack production cost were estimated 25.30 per kW while system production cost amounted to 51.31 per kW in 2010. Further cost reductions by more than 20 % are foreseen in the future [81]. In this case rather aggressive assumptions with respect to lowering platinum loading and a rather low platinum price has been taken into account. A recent update to the DoF study [82] acknowledged lower power density therefore, at a production volume of 500,000 units per year, the specific stack cost increased to U 27.05 per kW while the total system cost increased to U 54.83 per kW. The overall results of this study are shown in Fig. 14.19 and Table 14.2. It also shows the overall share of platinum metal cost to rise from 5.3 % at an annual production volume of 1000 stacks to 50.3 % at a stack production of 500,000 per year. 

In the European project Auto-Stack [83], a cost estimation for stack production has been carried out. The data were based on a survey of Emopean component suppliers. The results are shown in Fig. 14.20. It became evident that stack cost estimates were different by factor of two from the U.S. analysis. 

Fig. 14.19 Evolution of automotive stack cost according to the DoE 2013 study [82]. The relative share of platinum at the total cost is also shown...

Looking at the overall cost of PEFC stacks, achievement of high area specific power density has a key influence on stack and system cost. This can be shown using a comparable simple cost model dividing the stack cost in cost related to the pure platinum metal cost and cost related to the rest of the stack which for simplicity reasons is assumed to be proportional to the active area needed to achieve a certain stack power. 

Fig. 14.21 Dependence of specific stack cost on platinum loading using cost data fi om the 2013 DoE cost study [82]...

One can easily see that global minimum of stack cost shifts from 52.62 per kW at an annual production rate of 1000 stacks to 15.86 per kW at a production of 500,000 stacks per year. Surprisingly, the simple model predicts minimum stack cost at much higher platinum loading than the one used in the DoE studies 2012 and 2013 (Table 14.3). 

Once a mass market for fuel cell vehicles is established, availability of platinum will lead to increased platinum metal cost thus shifting the cost minimum to lower loadings. Figure 14.22 shows the influence of the Pt metal price on the stack cost assuming an annual production of 500,000 stacks. The cost minimum shifts to... 

Table 14.3 Mmimum specific stack cost and corresponding platinum loading based on the data of the 2013 DoE automotive stack cost study...

Fig. 14. 22 Dependence of specific stack cost on platinum metal price assuming area specific cost corresponding to a production rate of 500,000 units p.a.

Table 17.11 presents FC stack cost estimates, as well as the ICE cost, by various researchers. It can be seen that, in general, FCs are more expensive than ICE. However, if the FCs are mass produced (one million or more), then they become cheaper than ICEs, which are already mass produced. 

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