Wind energy storage technologies - Wind Power Generation and Wind Turbine Design - page 676

There are two NiCd battery designs: vented and sealed. Sealed NiCd batteries
are the common, everyday rechargeable batteries used in a remote control, lamp,
etc. No gases are released from these batteries, unless a fault occurs. Vented NiCd
batteries have the same operating principles as sealed ones, but gas is released if
overcharging or rapid discharging occurs. The oxygen and hydrogen are released
through a low pressure release valve making the battery safer, lighter, more
economical, and more robust than sealed NiCd batteries.
The DC-DC effi ciency of a NiCd battery is 60-70% during normal operation
although the life of these batteries is relatively high at 10-15 years, depending on
the application. NiCd batteries with a pocket-plate design have a life of
1000 charge/discharge cycles, and batteries with sintered electrodes have a life of
3500 charge/discharge cycles. NiCd batteries can respond at full power within
milliseconds. At small DoD rates (approximately 10%) NiCd batteries have a
much longer cycle life (50,000 cycles) than other batteries such as LA batteries.
They can also operate over a much wider temperature range than LA batteries,
with some able to withstand occasional temperatures as high as 50°C.
4.4.2.1 Applications of NiCd battery
Sealed NiCd batteries are used commonly in commercial electronic products such
as a remote control, where light weight, portability, and rechargeable power are
important. Vented NiCd batteries are used in aircraft and diesel engine starters,
where large energy per weight and volume are critical [3]. NiCd batteries are ideal
for protecting power quality against voltage sags and providing standby power in
harsh conditions. Recently, NiCd batteries have become popular as storage for
solar generation because they can withstand high temperatures. However, they do
not perform well during peak shaving applications, and consequently are generally
avoided for energy management systems.
4.4.2.2 Cost of NiCd battery
NiCd batteries cost more than LA batteries at $600/kW [3]. However, despite the
slightly higher initial cost, NiCd batteries have much lower maintenance costs due
to their environmental tolerance.
4.4.2.3 Disadvantages of NiCd battery
Like LA batteries, the life of NiCd batteries can be greatly reduced due to the DoD
and rapid charge/discharge cycles. However, NiCd batteries suffer from 'memory'
effects and also lose more energy during due to self-discharge standby than LA bat-
teries, with an estimated 2-5% of their charge lost per month at room temperature in
comparison to 1% per month for LA batteries [3]. Also, the environmental effects of
NiCd batteries have become a widespread concern in recent years as cadmium is a
toxic material. This creates a number of problems for disposing of the batteries.
4.4.2.4 Future of NiCd battery
It is predicted that NiCd batteries will remain popular within their current mar-
ket areas, but like LA batteries, it is unlikely that they will be used for future