integration of solid oxide fuel cells and ... - Ea Energianalyse

7. DISCUSSION
This leads to the next uncertainty - the lifetime which has been
assumed to be 10 years. This is a lot longer than what is possible today.
But as seen in figure 2.7 (page 36), the profitability doesn’t depend so
much on lifetime. So even if it is just 5 years, the gains from using the
SOFC is less than 10% smaller than if the lifetime was 10 years.
It must also be remembered that for all the calculations (of both SOFC,
ABS, and ECH) installation and maintenance costs have been neglected.
But even if these costs sum up to be as large as the purchase price of
SOFC unit during its 10 years lifetime, the pay back time of the SOFC
system will increase from around 1 to 1,5 years.
The model has been made as steady state and the selling and buying
prices of electricity have been assumed equal in the calculations in lack
of better data. In reality the sale price is likely to be lower than the
purchase price, but since the cost of the SOFC was seen not to have so
big an influence on the profitability, it might be a good idea to buy a unit
50% larger than average load, so it could be regulated up and down.
ABS unit
The ABS unit would give an extra gain of around 1,5 mil. DKK during
its 10 years expected lifetime which is quite good considering that the
additional purchase price of the ABS unit is only around 0,5 mil. DKK. 7 .
This way the pay back time of the ABS unit becomes around 1,5 years
for the hot climate, assuming the purchase price is 3700DKK/kW. If the
price were doubled, the pay back time would be 6 years. But the ABS
units are (in contrast to SOFCs) already on the market today, and the
estimated price is hence much more accurate than the estimated price of
the SOFC. There are however not so many suppliers of ABS units, and
very few of them make double stage units, so the price is still somewhat
uncertain, and one could imagine that it would decrease if the market
grew.
But as mentioned, the installation and maintenance costs have been
neglected for all units. If maintenance and installation costs for the ABS
sums up to be the same as the purchase price for the unit (during its 10
years lifetime), the pay back time of the ABS unit will increase from 1,5
7 The actual price of the ABS unit is 1mio DKK, but the supplementary ECH unit
can be smaller than if no ABS were used, so the cost of the ECH decreases from 1,4mio
DKK to 0,9mio DKK
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