Page 343 - Defrosting for Air Source Heat Pump

338 Defrosting for Air Source Heat Pump

costs are decreasing steadily from Case D5 to Case D8. Their values were 1.574 CNY
in Case D5, 1.552 CNY in Case D6, 1.389 CNY in Case D7, and 1.386 CNY in Case
D8. However, for the electricity cost during frosting in the four cases, although their
values show at D5¼D6>D7¼D8, their proportions at D5<D6<D7<D8. It is easy
to conclude that the running cost saved at the defrosting stage was much more than that
saved at the frosting stage. This also reflects that the economic performance of an
ASHP unit was highly improved after the trays and valves were installed.
Fig. 10.24 shows the total costs in the four typical cases over 15 operating years. From
big to small, their values were at 64,880.46 CNY in Case D5, 64,716.08 CNY in Case
D6, 63,910.52 CNY in Case D7, and 63,895.80 CNY in Case D8. This directly reflects
that the economic performances of an ASHP could be effectively improved after trays
or/and valves are installed. With nearly the same initial costs, the total costs in the four
cases were mainly decided by their running costs. The running cost in Case D5 was
56,880.46 CNY, but 55,730.80 CNY in Case D8. That means that as much as 3681.75
CNY, or 5.47%, of the running cost, could be saved after the trays and valves are
installed, from conditions (a) to (d) shown in Fig. 10.16. With their initial costs con-
sidered, the total cost decreased by as much as 3516.75 CNY, or 4.67%.
Fig. 10.25 shows total costs in four typical conditions in the 15 operating years. As
the fundamental assumptions are given, the total costs kept increasing in line with the
operating time. In practical application, the total running cost would increase much
quicker than expected because the energy performances of the ASHP unit would
decrease with time. Also, the maintenance costs increases the total running cost.
As shown in Fig. 10.25, the running cost relationship of the four typical cases shows
at D5 D6>D7 D8. This also reflects that the effects of the valves were more obvi-
ous than that of the trays on the running cost. After 2 years’ operation, their differences
were obvious. As shown in the inset in Fig. 10.25, their relationship became
D5>D6>D7 D8 after 12 years’ operation. The running period enlarged their dif-
ferences. Therefore, the conclusions of this study have important roles in the
budgeting work of equipment procurement. To clearly show the biggest difference
of the total costs in the four typical cases, the difference between Cases D5 and D8
is further shown in Fig. 10.26. Also, to further confirm the effects of the valves to
be larger than those of the trays, the total cost difference between Case D6 and Case
D7 in the 15 operating years is shown in this figure. When their values were 0, the
operating periods were both at 0.65 year. That means their additional initial costs
in Cases D6, D7, and D8 could be covered by their running costs in 0.65 year, com-
pared with the total cost in Case D5. When the operating durations were 5, 10, or
15 years, the total costs saved could be as much as 1062.25 CNY, 2289.50 CNY,
and 3516.75 CNY, respectively. Meanwhile, the total cost differences between
installing trays and valves were 976.78 CNY, 2088.58 CNY, and 3200.36 CNY,
respectively.
Fig. 10.27 shows the proportions of the initial cost in the total cost in four typical
cases in the 15 operating years. At the end of the lifespan, their relationship showed at
D8 D7>D6 D5. This also confirmed that the installation of trays and valves could
save more money in an ASHP unit’s application. As shown, when the recovery pro-
portions of the initial costs were at 50%, 40%, 30%, and 20%, the operating durations