Success has a Thousand Fathers , Failure is an Orphan
LOOK AT THE " SIMILAR THREADS " BELOW !
Mike Cantrell wrote:
Richard Hauser wrote:
<...>
The first usable tech is microhydro,
<...>
The second tech is pneumatic storage
<...>
The second tech points to the third tech, thermal storage.
<...>
The last energy storage is the one we are most accustomed to, wood.
<...>
There's a wonderful blog called Do The Math, written by a physics prof at UC San Diego. I'm going to link to one particular article here in a second, but before I do, I feel like I should promote him a little bit- just about every single thing he's written there has been pure gold. He goes into specifics on all of these energy topics, and like the titled of the blog suggests, he goes through an issue and does the math.
I'd encourage EVERYBODY who's interested in alternative energy to go to the beginning of his archive and read all his articles . They're a magnificent education. But I'll spoil the ending for you, too: the main answer to the world's electricity needs is a photovoltaic system on most roofs. The world's need for liquid fuels just has to shrink. That what he says, anyway.
Ok, back to the point. The author takes up these exact issues here:
http://physics.ucsd.edu/do-the-math/2011/09/got-storage-how-hard-can-it-be/
Here are some of the highlights.
Let's start small by considering the 3 W-h of energy stored in a AA battery, as computed above. One kWh of energy is 3.6x106 J of energy, so our AA battery stores 10,800 J of energy. A mass of m kilograms, hoisted h meters high against gravity at g=10 m/s^2 corresponds to E = mgh Joules of energy. If we were willing to hoist a mass 3 m high, how much mass would we need to replace the AA battery? Have a guess? The answer is 360 kg, or about 800 lb. A battery the size of your pinky finger beats the proverbial 800 lb gorilla lifted onto your roof!
The lesson is that gravitational storage is incredibly weak. A volume of water the size of our bedroom raised even 10 m above our home in a precarious threat to the neighbors would store 0.625 kWh. That’s enough for 30 minutes of typical household electricity consumption. You’ll forgive me if I ignore efficiency losses. It’s not even worth the effort.
Electrolysis for the production of hydrogen tends to range between 50-70% efficient. Then the fuel cell converts the stored energy back into electricity at 40-60% efficiency for a round-trip efficiency of 20-40%. If you happen to want some of the waste heat, then you might boost the efficiency estimate (true for any of these storage methods, actually). But in a straight-up apples-to-apples comparison, the hydrogen method is a very lossy storage option. If it were dirt cheap and low-tech, I might be more excited about its potential, despite the poor efficiency. But since the opposite is true, I’m not revved up over hydrogen storage.
I spent some time searching for a hydrogen fuel cell that I could buy today with a rating in the 10 kW range (appropriate for a home). I saw some production models achieving efficiencies ranging from 40-53%, but never a price tag. If you have to submit a query to learn the price, you probably can't afford it...
We could store energy in something akin to a spring by compressing air.
The efficiency for compressing the air and later turning a turbine for electricity generation may be less than what one might find for a flywheel. The storage itself is not the hard part. I could go out today and get some lab-sized cylinders (~50 liters), which could store 1.5 kWh each- about like a golf-cart battery, although heavier and bulkier. But I would have a very difficult time arranging an efficient pumping and extraction/turbine system. If not for that, I would find compressed air to be an attractive system compared to batteries: minimal maintenance; no apparent cycle limitations, reasonably low-tech, and perfectly tolerant of remaining at low charge indefinitely.
There's a wonderful blog called Do The Math, written by a physics prof at UC San Diego. I'm going to link to one particular article here in a second, but before I do, I feel like I should promote him a little bit- just about every single thing he's written there has been pure gold. He goes into specifics on all of these energy topics, and like the titled of the blog suggests, he goes through an issue and does the math.
I'd encourage EVERYBODY who's interested in alternative energy to go to the beginning of his archive and read all his articles . They're a magnificent education. But I'll spoil the ending for you, too: the main answer to the world's electricity needs is a photovoltaic system on most roofs. The world's need for liquid fuels just has to shrink. That what he says, anyway.
Success has a Thousand Fathers , Failure is an Orphan
LOOK AT THE " SIMILAR THREADS " BELOW !
"If you will live like no one else, later you can live like no one else." -- Dave Ramsey
Erik Little wrote:I just saw that the Company Iron Edison will now be selling US Made Ni-Fe batteries.
http://us4.campaign-archive1.com/?u=d832c729f5703f36b225522d1&id=c038f612c3&e=e0bde57760
paul wheaton wrote:Steven Harris just sent me this email:
I own NiFe batteries, I have since 1994. I know them well. The BIG reason to NOT buy them, they are incredibly expensive, they are charging you 9x the price of a lead acid and guarantying you only 5x the life. NiFe batteries are VERY inefficient, which means a significant fraction of the energy you put in, does not get stored, something like around 25%. They are VERY VERY gassy, that is why there is such a huge head space on them to hold SO MUCH extra water, which MUST be distilled water ONLY. They have a high rate of self discharge, so if you just leave them there, they can loose 10% or more of their charge PER DAY.
so yeah...they have a very long life, but everything else they have is a huge disadvantage.
Maggie Williams wrote:
Lead Acid Battery Efficiency - Below is a link to the Sandia National Laboratories results on Lead Acid Battery Efficiency. According to this document, they found out that when you are only using the top 20-30% of a battery, it really only has a charge efficiency of 55%. http://ironedison.com/images/Spec%20Sheets/Test%20Results/Sandia%20Labs%20Lead%20Acid%20Efficiency%20Test.pdf
Richard Hauser wrote:Please quantify the 1% self discharge number.
i.e. If you are off-grid and use solar to charge up your batteries to 100%, but then have a long storm so you get no charge for one week, where will the batteries be?
This is an important decision point in a design, because it will be a constant drain on the system, so it could be a limit the overall power you get out of a solar setup.
Wikipedia is listing 20-30% per month, so are you saying 1% per day?
Maggie Williams wrote:I would like to respond to the what Steven Harris said about the nickel iron batteries:
Questions 1. "Steven Harris just sent me this email: I own NiFe batteries, I have since 1994. I know them well. The BIG reason to NOT buy them, they are incredibly expensive, they are charging you 9x the price of a lead acid and guarantying you only 5x the life.
Answer 1: In reality, a nickel iron battery cost about double the price of a good lead acid battery. For example, a 12V, 263Ah Sun Xtender Sealed AGM Lead Acid Battery cost $650.00 online. This battery is rated at 1,850 cycles @ 30% DOD, which is 5 years. A comparable Nickel Iron Battery would be the Iron Edison 12V, 100Ah battery. The Iron Edison Battery is rated at 7200+ cycles, which is 20+ years. This battery will cost you $900.00.
So, if you are off grid and using your battery everyday, over a 20 years period you would have to replace that lead acid battery bank 4 times. With Nickel Iron you will never have to replace the battery, so over a 20 year period, you would have definitely saved money.
Country oriented nerd with primary interests in alternate energy in particular solar. Dabble in gardening, trees, cob, soil building and a host of others.
Get all of my Free Energy Classes at
http://www.Steven1234.com
Marcus Hoff wrote:
Where did I go wrong in my calculations?
Michael Buck wrote:I am an off grid lifer, been here 17 years won't ever, willingly, choose to go back. We electrified 11-12 years ago with 24v Trojan L-16HC. I was quite careful with my maintenance and that bank lasted me nine years of daily cycling. However, the last 6 months were dismal at best. Anyway, I mention the history as it is my only defense against ignorance about batteries. No science understanding, just seat of the pants daily charge and discharge.
A couple years ago, when replacement was needed, we decide on Iron Nickel and on Iron Edison as the dealer. I cannot say enough positive things about Brandon and Maggie Williams (owners of Iron Edison). Stellar individuals that really have there customers in mind and do ALL they can to help and ensure the product is understood and performing properly. I do love my batteries and I think the payoff will come but, obviously, that is along time from now. I have a neighbor with IN cells and we have fiddled and think we have found the sweet spot for DOD cycling parameters and it requires a more detailed description about what happens when you pass ~40-50% discharge. We have noticed that the cells discharged below 50% all the way to 80% discharge behave in line with the literature. That is, they will recharge and show no damage. They will fully recharge, however, the amount of energy to recharge the the 50-80% portion of the deep discharge is much greater than the energy required to recharge 30% on the top 40-50%. That is the only qualification I feel that the literature/information needs. You can deep discharge without damage but it will cost you to smile at the e-meter again.
Since we have backed off to a 40% discharge we are seeing stronger performance easier charging cycles and with an occasional overcharge the performance is fantastic. Water consumption is higher but even that has been largely mitigated with a slightly more gentle treatment.
Hey, do you know what would happen if you let the batteries run low on water? Anyone?
Permaculture and Homestead Blogging on the Traditional Catholic Homestead in Idaho! Jump to popular topics here: Propagating Morels!, Continuous Brew Kombucha!, and The Perfect Homestead Cow!
Dave Dahlsrud wrote:I think you would end up with carbon building up on the exposed plates and fouling your electrolyte. You would loose considerable efficiency of that cell, but on the bright side all you have to do is drain the electrolyte, open up the cell and clean it off with a pressure washer, then reassemble and refill with fresh electrolyte.
Get all of my Free Energy Classes at
http://www.Steven1234.com
Permaculture and Homestead Blogging on the Traditional Catholic Homestead in Idaho! Jump to popular topics here: Propagating Morels!, Continuous Brew Kombucha!, and The Perfect Homestead Cow!
SKIP books, get 'em while they're hot!!! Skills to Inherit Property
See me in a movie building a massive wood staircase:Low Tech Lab Movie
Community Building 2.0: ask me about drL, the rotational-mob-grazing format for human interactions.
The best place to pray for a good crop is at the end of a hoe!
Christopher Shepherd wrote:Hi Rachel. I use 12v for our main power supply here on our little farm. We just went through the darkest spring in 14 years here. We have 5 different setups with a total of 2000 watts available. We already have 12v lights, pumps, heaters, coolers, grinders, shellers, and so on. Have you ever tried using a supper capacitor to help with the high current start up of things like motors or inverters? I started buying caps and build them for our own use. They make a huge difference running things. I have a couple 58 farad at 16.2v and a few 350 farad at 16.2v. I would like to buy a couple 20amp hour batteries and controllers.
The best place to pray for a good crop is at the end of a hoe!
I'm gonna teach you a lesson! Start by looking at this tiny ad:
A PDC for cold climate homesteaders
http://permaculture-design-course.com
|