The problem: Wind and solar energy have low duty cyles; wind does not blow all the time, and the sun shines for only so many hours a day (or week, here in Western Washington). Those off the grid must store the electricity somehow, and for years the only viable way has been with lead-acid batteries, which typically last only 4 years or less depending on type and application, and are an environmental hazard. (I don't think hydrogen electrolysis/fuel cell systems are viable.) Utilities don't have any way to store electricity, so wind power at night is mostly wasted. Photovoltaic cells are attractive to individuals who want to defray their energy costs through grid-intertie (which puts power into the grid when it's most needed), but this doesn't do anything to protect them from rolling blackouts, which will become more common in some parts of the country (eg. California.) These kind of power outages already cost the U.S. economy an estimated $100 billion annually.

A technology that may eventually provide a solution is the flywheel battery, particularly that being developed by Regenerative Power and Motion, or RPM: http://home.earthlink.net/~fradella/homepage.htm I've been interested in flywheels as high-capacity energy storage devices since I read in a 1996 Discover Magazine article about how flywheels would soon be used in place of batteries for electric vehicles, but this application has met huge technical challenges. Flywheels are currently available from dozens of vendors for the Un-interruptible Power Supply (UPS) market, but can only retain energy for seconds or perhaps a few minutes, long enough to start up a diesel generator.

What makes RPM's flywheel battery so appealing is that it has very low idle losses, about 2W for their small 2kWh model, and so this flywheel can potentially store electricity for days, much like a bank of lead-acid batteries. It's not clear to me just how long this flywheel would continue to spin unloaded; it's not given explicitly on their web site, and I suspect the quick calculation of 2000Wh/2W = 1000 hours is not correct. As a comparison, a year-old design from pentadyne.com has 120W idle power consumption and can store only 0.67kWh when drawn over 20 seconds. It delivers 120kW over this time, however--clearly, a different class of flywheel.

I hope RPM can withstand the uncertainties of its start-up period, especially with what appears to be very little capital. These batteries would be much less expensive to operate over time than lead-acid batteries, and larger models may eventually allow utilities a viable way to store electricity. If it isn't all just hype, the flywheels will become popular enough for the price to be driven down, and I know I could use a few!

I thought I should correct what I wrote earlier rather than spread misinformation. In fact the utilities do have ways to store electricity, and there may be practical alternatives to lead-acid batteries for smaller applications.

The most common way in which utilities store electricity is with pumped hydro storage. Water is pumped uphill during off-peak hours and flows back downhill to generate electricity as needed, all with an efficiency around 70% to 85%. Pumped hydro generally has high capital cost and large capacity, presently around 3% of global generation capacity.

A more limited technology is found in a 2700MW CAES natural gas turbine plant, the third of its kind, planned for construction in Norton, Ohio. Unlike most plants which compress the gas at the time of generation, this one will pressurize air in an underground cavern during off-peak hours, and so requires only 40% as much natural gas to achieve the same power output.

There are a number of other technologies that are practical for niche applications, for example:
High-power supercapacitors and flywheels for short time scale applications such as power quality and UPS handover to a generator;
Li-ion batteries for high efficiency and energy density suitable for electric vehicles;
Liquid sodium-sulfur (NaS) batteries for high efficiency and energy density at less capital cost, suitable for UPS and energy shaving (buying more at off-peak rates);
Various pumped electrolyte flow batteries for higher efficiency, lower losses, and lower lifetime expense than lead acid batteries.

The Electricity Storage Information's website gives more details on these technologies: http://www.electricitystorage.org/technologies.htm

These technologies help give some perspective to a medium-power, scalable energy, low-loss flywheel system such as is being developed by RPM and perhaps also Beacon Power. Its low losses and low lifetime expense are still pretty exciting, but will probably be more useful to individuals, businesses, and infrastructure such as telecoms than it will be to the utilities.

Hi, I'm considering getting a AA solar battery recharger and stockpiling heaps of AA betteries. My question is how do I manage my batteries to ensure that I get maximum life? For example, are stockpiled batteries still going to work if I use them for the first time ten years after I buy them? Or do I need to regularly discharge and re-charge my stockpile? Or are they all going to not work after something like five years so I'm best to limit my stockpiling to a small amount just to last that long?

I've tried to find out this sort information on the web but haven't had success because stockpiling doesn't seem to factor in to the information out there. Also, should I stockpile a few extra solar chargers as well? I don't know how long these are supposed to last.

Tehere are many types of rechargable batteries:

NiCD - Nickel-cadmium are most basic ones, and cheapest. They have low capacity, and low maximum current. They suffer from memory effect. You must discharge them COMPLETELY, before trying to charge them, or they will suffer from decreased capacity.

NiMH - Nickel metal hydride - these were standard in mobile phones couple years ago. Have higher capacity, higher maximal current and do no suffer from memory effect that much, however, they still DO. In mobile phones, with regural recharging, their capacity is slowly decreasing and after 1-3 years it's just a fraction of original.

Lion / Lipol - Lithium ion and lithium polymer are standard in mobile devices here (phones, cameras). They do not suffer from memory effect, ad have similar properties as NiMH (Lipol are also extremely light compared to other types). They work bad in low temperatures and can handle usually above 1000 recharges.

All types of rechargable batteries dicharge slowly by themselves, some more some less, so you cannot really "store" energy in them for longer time.

Oh - and of course - lead based accumulators you have in your car - but I doubt cheap solar charger would charge it

Cartz and Licho, thanks for this string. This is an important item that
some might over look.

I have a small stockpile of rechargable NiMH's put away. The batteries were very expensive though. But I purchsed them with a gift certificate to Office Depot that I had won in a contest. Had I not won the certificate, I would have purchased the rechargable batteries (eventually) on eBay where they apear to be much more affordable.

I also purchased a universal solar powered battery charger on eBay. Now that you mention it Cartz, it might be good to purchase a second, just in case. I think I paid under $10 for the solar battery charger.

You can find survival goodies on eBay at VERY reasonable prices.
Trip

For NiCd and NiMH batteries, you must charge them at least once a year to prevent deterioration in performance due to self-discharge. Lead-acid batteries need even more attention: they must be kept fully charged to prevent deterioration, and some types require the addition of water.

Also, NiCd and NiMH batteries generally do not store energy as efficiently as lead-acid batteries, but this varies with application. NiMH batteries charged moderately quickly (at a rate equal to its capacity, or 1C) can be over 90% efficient for the first 70% or so of its charge, and drops off after that. Lead-acid batteries are over 90% efficient for the first 85% of capacity, and drops off quickly after that, but this assumes a lower C/30 charge rate; any charge faster than C/10 may cause unacceptable damage to the battery. Li-ion batteries can achieve nearly 100% efficiency in larger batteries with limited applications.

Most people who want some battery backup choose lead-acid batteries because there's nothing else out there as inexpensive for the capacity. A 1350 watt-hour golf cart battery might cost 85 USD whereas the same capacity in NiMH AA cells would require 478 cells and cost 1195 USD, and I'm assuming ultra-high capacity AA cells at eBay prices. Sure, solar chargers are more expensive for larger capacity batteries, but small solar chargers are really quite overpriced. You might find you're paying only two or three times as much for ten times the capacity.

Actually, I think they make lead-acid batteries that are completely dry. You have to add your own water and perhaps sulfuric acid. This might be the best way to go for long term rechargeable battery storage, as I don't think there's any deterioration until you add water. Once you do add water, the battery might not last more than 3-6 years depending on type and application.

When I talked with the RPM people 3 years ago, he was not in a shipping product phase, whereas Beacon Power was shipping vaccum packed flywheels on magnetic bearings. Now beacon power is into 'renewable energy' and backup power. A 5kWH unit that grid interties and has battery backup.

For whatever reason RPM hasn't gotten investor money to build product. So if you want a flywheel - Beacon power is it.

Cartz:
The long answer is: http://www.batteryuniversity.com
The short answer is: Buy Nimh batteries and keep them in the refrigerator, charged and above 0 Celsius.
A bunch of alkaline non-rechargeables are probably also a good idea.
In the refrigerator they will last pretty much indefinitely. At room temperature, they lose 3% a year.

Thanks AdvocatusDiaboli I'll check out the link.

Although the refrigerator option isn't gooing to cut it for me because I'm planning on the batteries being my only power (charged with a solar charger) hence I won't have a refrigerator to keep them in.

Thought i'd share this article. I have to say that a set of these would come in hand for a notebook computer or PDA. Disposal might be a problem, however!!! link

I believe a few satellites in space run on nuke batteries and a future spacecraft is scheduled to use them also.

If it wasn't for the increased cancer risk, low sperm count, and radioactive landfills, it would be nice to have this kind of power.

While this is a nice sounding idea there some genuine problems with it that make me quite uneasy.

Radiothermal generators have been around for decades - ever since nuclear power and weapons were researched. Although they have historically been large devices used for powering remote installations - e.g. marker buoys in dangerous waters, or deep-exploration spacecraft. There was a brief spell with using them in implantable cardiac pacemakers, before chemical battery technology became good enough.

They aren't used in satellites - satellites get plenty of solar power. They are used for spacecraft that have limited supplies of power, due to distance (e.g. the Cassini-Huygens probe now examining Saturn and its moons - the sunlight would be far too weak) or due to lack of space (e.g. the mars rovers use radioactive warmers to stop their batteries freezing at night, but don't have the space for insulation or excess battery capacity).

There are serious risks with large (a few Watts) generators - as they contain a substantial amount of radioactive material, which must (by their very nature) be of very high radioactivty. There have been a number of incidents where they have caused serious injuries when handled incorrectly. For a typical incident read the report here:

IAEA.ORG

Historically, these devices have used several lbs of materials like Stronium-90, or Plutonium-238. These have very strong heat generation properites. However, they have multiple disadvantages - they produce penetrating radiation which needs heavy shielding, they can decay into other radioactive materials (which may be radioactive for thousands of years), and have long half lives and so themselves pose a hazard for hundreds of years.

These modern devices are much, much better. They have short half lives and decay into non-radioactive materials in a predictable way. The Polonium device discussed above has a half-life measured in days, so within 10 years there will be no significant radioactivity remaining. The other advantage is that it is a pure alpha emitter, so there is no need for radiation shielding - none escapes.

The main problem with these devices is not radiation released from the package, it is release of radioactive material from a damaged device into the environment. Alpha emitting radioactive materials are particularly dangerous because their radiation is not reliably detectable with geiger counters. There may also be a false sense of security because no significant radiation shielding is required - yet, these alpha emitters are some of the most dangerous materials on the planet if they enter the body.

10 picograms of Po-210 (about 1/100 the size of a particle of icing sugar), if swallowed or inhaled, could bring a very high risk of cancer at a later stage in life. Indeed the radiation is so intense, that drinking a solution containing even 10 nanograms of Po-210 could cause rapid fatal radiation poisoning.

The other problem with the modern systems comes from their short half-life - their power will rapidly decline. In the case of a Po-210 battery it will be operating at about 10% power after 1 year, and at 1% after 2 years.

Do we really want to hand these immensely dangerous materials to anyone who wants them, with no attempt to protect the environment from them? How do you stop a child from smashing up his toy with a hammer and releasing enough radiactive dust to kill him 10 times over? Do we really want to build devices with a short and finite lifetime, yet require storage for 10 years prior to final disposal?

I appreciate that radioactive materials are readily available in household items today (e.g. smoke detectors), but these 'batteries' would be several million times more powerful - a whole different class of risk.

There may be niche applications, but I would have thought few of these would be in the hands of the general public.

I've read that coal fired power plants also emit quite a bit of radioactive material. Why is no one concerned about this?



probably worse things to worry about like mercury, lead, and arsenic.

It does seem they are very interested in finding new power sources for cell phones. Maybe they should just make the battery 2x size, because the one i have is tiny.