Can you replace a Battery Bank with Capacitor Bank for use with Solar ???  - Page 1
Forum section: electronics / general

author: Ksfixitman
author_rank: Newbie
timestamp: January 09, 2019, 04:44:01 am
content: This is why I'm asking. A video blogger posted a talk about his opinions on some Solar info he had done in the past with regards to battery banks and what type battery was the best and this was one of the responses. I did some research and it looked maybe 50/50 about the subject so Dave is always saying to post here and ask questions. so below is the argument on the subject.Shaun Sim10 hours agoBattery point blank are old dirty outdated tech wrapped up in fancy words and stickers all for marketing and prophet! Get yourself a Capacitor bank, does the same job all day long and you get well over 1 million + charges compared to dirty lithium which can only take 1200 charges, And lithium mining is outdated and harms and scars the planet compared to a capacitor that is clean and easy to make.﻿Is he correct or full of crap

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 09, 2019, 05:24:55 am
content: The answer depends on exactly what you are asking. You definitely can replace a battery bank with a large capacitor bank. And it will withstand many, many more charge cycles than a battery bank. And with today's technology will take many, many more dollars to build and much more room to house.Just for an example you can buy a capacitor module from Maxwell. 48V, 180 F for a mere $1500. Energy stored is 1/2 CV^2 or about 210 kJoules. A Joule is a Watt sec, so this is about 0.06 kW hours, assuming that you can extract the energy down to zero volts. In reality you will be able to use significantly less than the full energy content of the capacitor. It will take a lot of these $1500 modules to store enough energy to tide you over night time usage, let alone a long period of deep clouds.People get carried away with super capacitors. Thirty years ago the kind of capacity they have achieved was not just beyond state of the art, it was beyond science fiction. They really are amazing. But still not the right answer for energy storage.

author: Ampera
author_rank: Super Contributor
timestamp: January 09, 2019, 05:30:41 am
content: big caps are only useful for one thingsdetonating small electronics and various fruits and vegetables.no exceptions, no arguments.

author: Psi
author_rank: Super Contributor
timestamp: January 09, 2019, 06:02:33 am
content: Quote from: Ampera on January 09, 2019, 05:30:41 amThe 16V 433F super capacitor bank i had in my car to replace the car battery says otherwise.It worked great for 7 years (until i replaced the car.)It did understandably have a few disadvantages- It would discharge ~20x faster if i left anything on with the engine not running.- If the cap bank was ever under about 9V you had to give it a bit of gas for 5 sec after starting to prevent the alternator stalling the engine due to massive charge current.But it never wore out and the car sounded awesome cranking the engine over, since the voltage didn't drop much under 300A load the starter motor got more voltage.

author: Seekonk
author_rank: Super Contributor
timestamp: January 09, 2019, 02:12:54 pm
content: I can't argue that batteries suck. And how people do solar as well. I have only a car battery in my off grid system with all the normal stuff including PV hot water and a dishwasher with heated dry. No one is interested in real time energy use and prefer to just black box a system with big storage.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 09, 2019, 02:54:23 pm
content: The choice of energy storage component is driven by how long the energy needs to be stored for, how fast (peak power), and whatever's cheapest.Viewed from this angle, it is clear that solar is best served by batteries. Batteries are the slowest electrical component, with time constants from seconds to hours or days. Solar needs to store energy for less than a day, with peak power equal to the installation size, which turns out to be ideal for most battery chemistries (including lead acid and lithium ion).Supercaps are great at storing small amounts of energy for long periods of time ("CMOS backup"), or delivering high power over short periods of time (seconds). An example might be a boost circuit in an electric car, where energy is drawn from a slow battery, into a fast capacitor, then dumped into the motor and vehicle in a few seconds -- a race car might need to deliver a megawatt over a few seconds to accelerate competitively. But it might only need a fraction of that for cruise, which can be drawn from the battery while the supercaps are recharged for another boost.But supercaps are also quite expensive and bulky. It very often happens that, it's cheaper or more compact to use enough batteries to handle the peak power, which gets extra charge capacity as a byproduct. Or conversely, if you need the extra charge, you get the power for free -- which is how Tesla's cars are so powerful. They don't need to be, but they have the electrical power available, and it's not much cost (considering it's already a luxury vehicle) to connect that power to the wheels, so... they do!This back-and-forth continues onto smaller time scales as well, where we go from supercaps to electrolytic caps, to aluminum-polymer and film capacitors, to ceramics and transmission lines. Switching power supplies, for example, have large power demands on the microsecond time scale, but it's more economical to use relatively oversized electrolytic capacitors to satisfy that demand, rather than film caps which are more bulky and costly. Though the balance changes a bit at high voltages, where film caps are actually less bulky for the same power or current rating (or electrolytics aren't available at all!).On the smallest time scales, we have transmission lines -- storing energy, nanoseconds at a time, as wave energy propagating near the speed of light. The most notable case is the "Z Machine", which uses an extremely pure water dielectric to deliver petawatts in about a hundred nanoseconds!There can also be economies of scale. Thermal plants (solar thermal, usually) store heat energy in enormous tanks of molten salt: the high melting point, and relatively high specific heat, keeps the process temperature up, even after the sun sets, allowing a steam turbine (usually) to operate reasonably efficiently around the clock. Pumped fluid systems include water going up and down from a mountain lake, or air pumped into an underground chamber. These have their losses, but apparently not so bad they can't be used for day-to-day demands, as results from solar and wind sources.Electrical storage is actually one of the least efficient possible, in terms of space -- you can only make a capacitor as small as a few atoms, and you can only put as much energy into those atoms as they'll store before ionizing. Ionization is chemistry, and then you have a battery, see?Tim

author: metrologist
author_rank: Super Contributor
timestamp: January 09, 2019, 04:47:17 pm
content: What about a super cap that is integrated with the foundation/slab of the house/garage, and equal in size, out of the way?

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2019, 06:58:17 pm
content: Perhaps if you are a billionaire with nothing better to spend your money on and don't mind tearing the house down if you ever have to replace the capacitor.Even the best supercaps don't store anywhere near as much power as a battery and the cost is orders of magnitude higher.

author: Nusa
author_rank: Super Contributor
timestamp: January 09, 2019, 07:11:56 pm
content: Quote from: metrologist on January 09, 2019, 04:47:17 pm