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The Cost of Mobile Power
Among the common power sources, energy from non-rechargeable
batteries is the most expensive. Figure 17-1 reflects
the cost per kWh using non-rechargeable batteries, also referred
to as primary batteries. In addition, non-rechargeable batteries
have a high internal cell resistance, which limits their use
to light loads with low discharge currents.
In the last few decades, there has been a shift
from non-rechargeable to rechargeable batteries, also known
as secondary batteries. The convenience of recharging, low
cost and reliable operation have contributed to this. Another
reason for the increased popularity of the secondary battery
is the larger energy densities available. Some of the newer
rechargeable lithium systems now approach or exceed the energy
density of a primary battery.
|
|
| |
AAA
Cell |
AA
Cell |
C
Cell |
D
Cell |
9
Volt |
|
|
| Capacity
(alkaline) |
1100mAh |
2500mAh |
7100mAh |
14,300mAh |
600mAh |
| Energy
(single cell) |
1.4Wh |
3Wh |
9Wh |
18Wh |
4.2Wh |
| Cost
per Cell (US$) |
$1.25 |
$1.00 |
$1.60 |
$1.60 |
$3.10 |
| Cost
per KWh (US$) |
$890 |
$330 |
$180 |
$90 |
$730 |
|
|
Figure 17-1: Energy and cost comparison
of primary alkaline cells.
Energy from primary batteries is
most expensive. The cost increases with smaller battery sizes.
Figure 17-2 compares the cost of power
when using rechargeable batteries. The analysis is based on
the purchase cost of the battery and the number of discharge-charge
cycles it can endure before replacement is necessary. The
cost does not include the electricity needed for charging,
nor does it account for the cost of purchasing and maintaining
the charging equipment.
|
|
| |
NiCd
AA Cell |
NiMH
AA Cell |
Lead
Acid
(typical pack) |
Li-ion
18650 Cell |
Reusable
Alkaline AA Cell |
|
|
| Capacity |
600mAh |
1000mAh |
2000mAh |
1200mAh |
1400mAh 1 |
| Battery
Voltage |
7.5V |
7.5V |
12V |
7.2V |
7.5V |
| Energy
per cycle |
4.5Wh |
7.5Wh |
24Wh |
8.6Wh |
6.3Wh |
| Cycle
life |
1500 |
500 |
250 |
500 |
10 |
| Cost
per battery (ref. only) |
$50 |
$70 |
$50 |
$100 |
$6.00 |
| Cost
per kWh ($US) |
$7.50 |
$18.50 |
$8.50 |
$24.00 |
$95.00 |
|
|
Figure 17-2: Energy and cost comparison
using rechargeable cells.
Older battery technologies offer
lower energy costs compared to new systems. In addition, larger
cells are more cost-effective than small cells. The battery
packs taken for comparison are for commercial applications
at over-the-counter prices.
For this calculation, 840mA is used since subsequent capacities
are rated at 840mA (60% of initial capacity). If the battery
is discharged partially, a higher cycle life can be obtained.
Figure 17-3 evaluates the cost to
generate 1kW of energy. We take into account the initial investment,
add the fuel consumption and include the eventual replacement
of each system.
Power obtained through the electrical utility
grid is most cost effective. Consumers in industrialized countries
pay between $0.05 and 0.15US per kWh. The typical daily
energy consumption of a household is 25kWh.
|
|
| |
Investment
of equipment to
generate 1kW |
Lifespan
of equipment before major overhaul or replacement |
Cost
of fuel
per kWh |
Total
Cost
per kWh, incl. fuel, maintenance and equipment replacement |
|
|
NiCd
for portable use |
$7,000, based on 7.2V, 1000mAh
at $50/pack |
1500 h, based on 1C discharge |
$0.15 for electricity |
$7.50 |
| Gasoline
Engine for mobile use |
$30, based
on $3,000/100kW (134hp) |
4000 h |
$0.10 |
$0.14 |
Diesel
Engine
for stationary use |
$40, based on $4,000/100kW (134hp) |
5000 h |
$0.07 |
$0.10 |
| Fuel
Cell |
$3,000 – 7,500 |
|
$0.35 |
|
| - for portable
use |
|
2000 h |
--> |
$1.85 – 4.10 |
| - for mobile
use |
|
4000 h |
--> |
$1.10 – 2.25 |
| - for stationary
use |
|
40,000 h |
--> |
$0.45 – 0.55 |
Electricity
from electric grid |
All inclusive |
All inclusive |
$0.10 |
$0.10 |
|
|
Figure 17-3: Cost of generating 1kW of
energy.
This takes into account the initial
investment, fuel consumption, maintenance and eventual replacement
of the equipment. The most economical power source is by far
the utility; the most expensive is portable batteries.
The fuel cell offers the most effective means
of generating electricity, but is expensive in terms of cost
per kWh. This high cost is made economical when comparing
with portable rechargeable batteries. For mobile and stationary
applications, the fuel cell is considerably more expensive
than conventional methods.
Note: The costing information obtained
on the fuel cell is based on current estimates and assumptions.
It is anticipated that improvements and wider use of this
technology will eventually lower the cost to be competitive
with conventional methods.
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