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Registered Member #1561
Joined: Mon Jun 23 2008, 07:58PM
Location:
Posts: 25
So I'm working at a company that is using capacitors as a storage unit, like for batteries for electric or hybrid cars, the reason being is that they have a longer pack life. So I was thinking could you use a pack of capacitors as your storage unit for solar power. Have the solar panels charge the cap bank instead of a battery bank.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
I have no idea what kind of storage capacity the supercaps have relative to actual loads, so this might be unrealistic. What about using solar panels (roof mounted) to feed a large cap bank which can be connected to mobile supercap banks on golf carts? Relatively speaking it would allow for fast recharging cheap since currently they sit for a fair while to recharge.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
It would work if you got the capacitors for free, if not they are too expensive for most applications. The capacitors are also less efficient than lithium batteries so you would need more solar panels to get the same power.
Let us think about the golf cart for a minute. If you want 1 kW/h stored. That means ((1000*3600)/7290) = 494 capacitors of 2.7V, 2000F. That is $36 750 on ebay,
A random lithium battery from ebay gives (1000*3600/51948) = 70 batteries of of 11.1V, 1.3 Ah. That is $1050,
7.5 kg of batteries 200 kg of capacitors
You still need to add more capacitors to make up for the lower efficiency and increased weight. If we go down to the same price and weight the capacitors will only last 2 minutes instead of one hour. Charging is not a lot better for capacitors at the same energy either, in this case the batteries can safely be charged in 2 minutes to the same energy as the capacitors. Modern high power batteries may be charged to the same energy in 30 seconds.
It is very difficult to find an application where capacitors are clearly better if you have to pay for them. Even with applications that require many charge/discharge cycles. Because at the same price you can get so many lithium batteries that you can keep them cool at 40% charge and only cycle them a few percent so they will last almost forever.
In cases where you need very rapid charge and discharge the capacitors would be better.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
I did recall reading about "zero voltage" switching MOSFETs which will actually conduct with virtually no applied voltage between drain and source. These would be ideal for a switching supply using low voltage capacitor arrays, you just increase the pulse width linearly as the voltage drops.
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Solar Power Ideas
