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Why energy storage sucks

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Re: Why energy storage sucks

#61

Post by semi-extrinsic »

dangravell wrote: post #40
mangecoeur wrote: post #28

Very limited view of energy storage tech frankly. Quick list of things I am aware of (some deployed and some in labs) - Pumped hydro, by far the most widespread - Flywheel storage, used at grid scales for frequency regulation - Thermal storage used in conjunction with solar power using various materials - molten salt, HTF, hot dry rock - Many different battery chemistries: - High temperature batteries (e.g. ZEBRA bat…

Some interesting products utilising PCMs in the domestic hot water markets... Replacing traditional hot water cylinders which suffer from very high heat loss even when insulated.

The economics aren't great for replacing a hot water cylinder with something more efficient.

According to this [1] a typical hot water cylinder wastes less than 2000 kWh per year. That's a yearly expense of less than $400. This means a replacement system aiming to break even over five years must cost less than $2000.

Replacing a hot water cylinder with a bog standard new one costs at least $1000. Thus the PCM heater must be essentially as cheap as existing solutions, and so it faces the challenge of not being able to get enough initial volume to get the cost below break-even. Government subsidies are probably the only way to make it work.

[1] http://www.solarblogger.net/2012/11/heat-losses-from-hot-wat...

Re: Why energy storage sucks

#62

Post by debacle »

Dylan16807 wrote: post #59
mhandley wrote: post #34

Earlier quoted context omitted.

A 12V deep-discharge lead-acid battery is typically 120amp-hours. That's 1.4kWh. Suppose you only 50% discharge it for longevity, that's 700Wh. I'll assume your box of batteries has ten of them, so a usable capacity of 7kWh. 1kWh = 3.6MJ, so 7kWh = 25MJ How high is your roof? Lets say 10 metres. Potential energy U = mgh. (m=mass in kg). h=10, g~=10, so U=100*m. So, to equal those batteries, assuming 100% efficiency,…

So 'roof' is clearly out of the question. Now let's look at basement. I install a 4x4x2 meter tank, then drill down 100 meters to create another such tank. 32 tonnes lifted 100 meters gives me 32MJ, perfect. Now how expensive is it to build a water storage area underground? Is this a 50 thousand dollar project or a 50 million dollar project? If the ground water is at the right depth, you would only need to drill a we…

Your 100 meter channel is going to get flooded.

Re: Why energy storage sucks

#63

Post by Dylan16807 »

debacle wrote: post #62
Dylan16807 wrote: post #59

Earlier quoted context omitted.

So 'roof' is clearly out of the question. Now let's look at basement. I install a 4x4x2 meter tank, then drill down 100 meters to create another such tank. 32 tonnes lifted 100 meters gives me 32MJ, perfect. Now how expensive is it to build a water storage area underground? Is this a 50 thousand dollar project or a 50 million dollar project? If the ground water is at the right depth, you would only need to drill a we…

Your 100 meter channel is going to get flooded.

That's your biggest objection to the idea? A 100 meter waterproof pipe is the easiest problem to solve here.

Re: Why energy storage sucks

#65

Post by nkurz »

mineshaftgap wrote: post #45
aolagers wrote: post #37

Earlier quoted context omitted.

Pumped hydro is interesting but the reservoir requirements are huuuge. This post makes a very convincing case that scaling it up is not that simple: http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-stor... There is some discussion about the German rock variation in the comments. The density doesn't seem to help THAT much compared to water only.

"to get the amount of energy stored in a single AA battery, we would have to lift 100 kg (220 lb) 10 m (33 ft) to match it. To match the energy contained in a gallon of gasoline, we would have to lift 13 tons of water (3500 gallons) one kilometer high (3,280 feet). It is clear that the energy density of gravitational storage is severely disadvantaged." http://physics.ucsd.edu/do-the-math/2011/11/pump-up-the-stor...

It's almost incredible that a AA battery can do that much work, but I checked the math:

  Alkaline AA Battery =~ 3 Wh =~ 10000 Nm
  Gravitational Potential Energy =~ kg * m * 10 N/kg
  100 kg * 10 m * 10 N/kg == 10000 Nm == AA Battery
It also puts into perspective how much solar energy is available. A single 200 W panel (~5 sq ft or ~.5 m^2) can charge hundreds of AA batteries per day, and thus would require lifting more than 10000 kg by 10 m to store a single day's output from just that one panel!

Re: Why energy storage sucks

#66

Post by jhallenworld »

aidenn0 wrote: post #55
pjc50 wrote: post #8

Earlier quoted context omitted.

Personal VRBs make about as much sense as having your own gas turbine, but utility-scale ones for peak demand response make a lot of sense.

Speaking of having your own gas turbine, that was my existence proof a while back for how to handle events where lots of people want to charge there cars all at the same time: 30MW in a trailer http://www.pwps.com/gas-turbines/30-mw-mobile.html Granted there are almost certainly better solutions, but anywhere we can deliver NG to, we can deliver stupendous amounts of electricity to, for a price.

Gas turbines have a loudness problem, but there are natural gas reciprocating engine co-generation plants available for your house:

http://world.honda.com/powerproducts-technology/cogeneration...

Re: Why energy storage sucks

#67

Post by tarikjn »

mangecoeur wrote: post #28

Very limited view of energy storage tech frankly. Quick list of things I am aware of (some deployed and some in labs) - Pumped hydro, by far the most widespread - Flywheel storage, used at grid scales for frequency regulation - Thermal storage used in conjunction with solar power using various materials - molten salt, HTF, hot dry rock - Many different battery chemistries: - High temperature batteries (e.g. ZEBRA bat…

Also, of note, Proton exchange membrane fuel cells can be used both for Hydrogen but also fuels liquid at room temperatures. For examples there are Direct-Alcohol Fuel Cells for Methanol and Ethanol.

Re: Why energy storage sucks

#68

Post by Fjolsvith »

aswanson wrote: post #30
stcredzero wrote: post #21

Earlier quoted context omitted.

Spellchecking? What about innumeracy? As you can see if you only drain your battery to 75% (meaning you only use 20% of your capacity) you get tremendously more cycle’s (more than double!) then say using 50%. So when systems are designed for energy storage you generally want your batteries to last a long time (since they’re expensive) so you want the maximum amount of cycles for them, which means that you should only…

Yeah, I was hesitant to click on the article based on the title. Thanks for confirming my suspicions.

I did learn a few things from the article, though. The big one has to do with why the car batteries I use on a hydraulic and winch system have been failing fast. It has to do with the way I run them all the way down before charging them back up.

In my shed delivery business, I have a custom designed trailer with a hydraulic lift for the tilt bed and a winch for loading and unloading the buildings. They are 12 volt and I just run them with a car battery.

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