ConsumerismEnergy Systems

A Solar Powered Life, Part IV – The Dirty Little Secret

Editor’s Note: This is Part IV of a series. To see all parts, click here.

Have you ever wondered why you don’t see many electrically powered motor vehicles on the roads, despite all the recent hype? Well, it’s because electricity has a dirty little secret: We have the technology to generate massive amounts of electricity, however storing those massive amounts of electricity for later use has been something of a problem that hasn’t yet been solved.

The two main ways our society currently stores electricity for later use are batteries and hydro-electric facilities. I’m not suggesting that anyone construct a hydro-electric dam and generator in their backyard because it would require a huge volume of water to generate useful amounts of electricity, so instead I’ll discuss batteries and what they are all about.

You might not know it, but batteries are quite an old technology. At home I use lead acid batteries, a technology which was invented back in 1857. They produce electricity through a chemical reaction between the two metals lead and lead oxide with an electrolyte of sulphuric acid. As the amount of electricity stored in the battery decreases, the metals change to lead sulphate and the electrolyte becomes water. As the battery is charged, the chemical reaction reverses to its previous state. Fortunately, you don’t have to understand the chemistry behind a battery to be able to use one, however it is useful to remember that a battery is really a chemical reactor, which gives it odd quirks and limitations which we’ll discuss later.

There are alternatives to lead acid batteries such as: Nickel Metal Hydride batteries; Lithium Ion batteries; and fuel cells – just for some examples. Most of these examples would probably work far better than a typical lead acid battery of the same capacity. They may even weigh less than the equivalent lead acid battery. However, none of these alternative batteries are commercially available on the scale that you would require for a home solar power system. Even if they were, they’d be hideously expensive because of their use of exotic materials and low production volumes so they aren’t worth considering here.

Lead acid batteries are both a simple and reliable technology. They are also relatively cheap to manufacture. Therefore, if you looked at most off-grid solar power systems, they’d be using lead acid batteries.

Aliens and acid: More alert readers will notice that I’ve now used the word acid eight times so far. Way back in 1979, I went to the cinema and watched the science fiction film Alien as a young child, which left me with nightmares for weeks. One scene showed acid from the Alien‘s fluids dripping through several floors of the spaceship. Needless to say I’ve been left with an unnatural respect for the powers of acid (even though an acid couldn’t really reproduce the affect in the film — the effect was pure artistic licence, even for Alien acid). Batteries really do contain sulphuric acid though, which is corrosive.

Lead acid batteries come in two types: flooded; or sealed. The difference between flooded and sealed batteries is that the sulphuric acid is accessible for flooded batteries, whilst sealed batteries, as their name implies, are sealed. This doesn’t sound like much of a difference, but in flooded batteries, the acid can escape from the battery through evaporation or boiling off (if they are overcharged) so you have to keep any eye on the quantity and quality of the acid. Also, with a flooded battery, to stop the acid eating through the floor of your spaceship should it get knocked over, the battery has to sit in a drip tray. Other than that either type of battery has about the same amount of electrical capacity for its size, but sealed batteries are more complex to manufacture, so they cost a whole lot more.

Sealed batteries suit me and I use gel type sealed batteries in my solar power system. Many more people use the flooded lead acid batteries though because they are cheaper to manufacture, so they are cheaper to buy.

You might not think about it much, but there are lead acid batteries literally all over the place. Every time you see a motor vehicle, you can be pretty sure that somewhere in that vehicle there’ll be a lead acid battery. Given that there are so many of them kicking around people often ask me the question:

Can you use the batteries ordinarily found in a motor vehicle in a home solar setup? The simple answer is, yes, but the long term practical answer is no.

Anyone who has ever run out of petrol or diesel in a motor vehicle and tried to continue driving using the electrically powered starter motor knows that the battery goes flat pretty quickly. The batteries that are put into motor vehicles are manufactured so that they deliver a large amount of power quickly for the purposes of starting, lighting and ignition, but they won’t provide that power for very long. The batteries used in solar power systems are referred to as deep cycle batteries because they are manufactured to have a longer life, deliver a smaller amount of power over a longer period of time, and, more importantly, they can be charged and completely discharged many more times than a motor vehicle battery ever could.

Getting back to the dirty little secret. Existing and commercially available batteries simply can’t store that much electrical energy. If you wanted to run a 2,400Wh fan heater for an hour, the lead acid battery would weigh about 70kg! This shows the simple rule relating to lead acid batteries. Generally, the larger and heavier the lead acid battery, the more electrical energy that that battery can deliver. It may surprise some people to find that the lead acid batteries that I use in my house weigh in excess of 1,000kg. This weighs as much as a small car and their total electrical storage capacity when 100% full is only around 30kWh which an average household may use in about 1 to 2 days.

A Tesla Roadster (an electric vehicle recently released in Australia at a drive away price of over $200,000) according to Wikipedia will use about 17.4kWh to travel 100km. Admittedly, the vehicle uses advanced Lithium Polymer batteries, however this is almost half the storage capacity of my own system. If you think about how far you drive your own vehicle in a day, try and take this information and work out how much electrical energy you would require (174Wh per km). Then, have a second look at A Solar Powered Life – Part III and try and calculate how many solar panels you would require to power just your daily requirements. You can quickly see why oil derived products became the choice of fuels in motorised vehicles.

If anyone wanted a guaranteed way to make a fortune, it would be through developing a cheap and lightweight way to store large quantities of electrical energy.

In the next article, I’ll discuss how batteries work in the real world and more importantly what batteries, the space shuttle and airship disasters have in common.

Continue on to read Part V

14 Comments

  1. Thanks Chris,
    I’ve been a big fan of your series. We could use more “explain hyped-up technology X” type of articles.
    Keep up the great work!
    Sam

  2. “Dirty Little Secret” ?? WHERE?

    An over hyped titled for a pretty bland article. Surely anyone with an ounce of knowledge will know that battery power is limited UNTIL someone make a battery that is capable of efficiently storing power.

    A dirty little secret not. Just a fact that has been around for over 150 years!

    For vehicles, electric cars will never become commercially viable. The use of scarce materials required to create efficient batteries will simply not work.

    The use of hydrogen as an energy carrier is more viable but not without limitations!

    Something will come along one day as an ‘alternative energy’ but it is a long way off yet

  3. Hi Sam,

    Thanks for the feedback. You should enjoy the next article which will look at how batteries work in the real world.

    Hi John,

    You’re harsh! Most people have very high expectations which exceed the abilities of the available technology. I doubt it’s very common knowledge. You mention hydrogen, but you are obviously unaware that it takes more energy to produce hydrogen than the energy that you obtain from burning it. There are also some very serious engineering difficulties to be over come with the storage of hydrogen. Hydrogen must be manufactured, whereas oil products are mined this affects the net return of energy.

    Regards

    Chris

  4. Thanks for another well written and thoughtful article Chris.
    I read some time ago about research on lead acid batteries by a Finnish chemist – the reason lead acid is so effective is due to quantum effects. The charged lead nuclei can attract electons at 60% of light speed, giving the battery an extremely high voltage potential. Interesting stuff.

    John – “something will come along one day” is an indication of teleological thinking. I wouldn’t hold my breath waiting for any future technology to take the squeeze off our energy predicament.

  5. Hey Chris,

    Might be interesting for readers to know that the Alternative Technology Association (ATA – https://www.ata.org.au) put out a magazine called ReNew and in a recent past issue (No. 113) covered the different battery technologies. You rightly point out pretty much everyone uses lead-acid, although seems like some promising tech gaining ground like LiFePO4 (cost more of course but you can get up to twice the life if treated properly).

  6. Hi Ben,

    Thanks for the feedback. I read up on the quantum effects on voltage in lead acid batteries and it seems to me that they were onto a winner when they developed them way back in 1857. However, I can’t in all honesty say that I understood most of the article as once it worked it’s way into heavy physics my head started to spin! Thanks for the gentle rebuke too, you’re spot on!

    Hi Jason,

    Much respect to the ATA and Renew magazine which I have read at times over the years. Pretty much everyone uses lead acid batteries in their home solar power systems. Large scale Lithium Polymer batteries would be awesome and would save me the hassle of having over 1,000kg of batteries in the house. However, the gel lead acid batteries I have were expensive, Lithium Polymer batteries would be well beyond my budget. The solar industry would also need to develop regulators that correctly charge Lithium Polymer batteries too and if there is little demand, well… I’d love to see Lithium Polymer batteries developed and distributed on a large basis, but I can’t see it happening any time soon.

    Regards

    Chris

  7. Hi James,

    Thanks for the link, but don’t believe everything you read on the Internet, especially exaggerated claims. Investors have a saying, “If it sounds too good to be true, it probably is”.

    Water can only provide power for a vehicle if it is either:
    a) Compressed and stored then released, which requires more energy than it will ever return; or
    b) Split into hydrogen and oxygen and then either burnt or recombined, which requires more energy than it will ever return.

    You may note that there is a pattern here which I’ll talk about in the next article.

    Regards

    Chris

  8. Hi James,
    just few words to concur with Chris: the water powered car is a story that started more than 40 years ago in France (unless there is more than one of those “discoveries”). The narrative follows this trend:

    1) Press release, saying that there is this new technology, which found a new sponsor in X after being blocked in Y because by the oil/car business companies.
    2) Press release claiming that the new cars will hit the market very soon
    3) disapearance from the radar
    4) Go back to 1) after few years changing X by Z and Y by X

    This idea is based on a technical truth though: adding water to some combustion engines has *very specific* technical applications.

    Going as far as saying that we can then only use water on the other hand is a fantasy. Unless as Chris said, you use pressurized water or crack the water into hydrogen and oxygen, which is then even more of a fraud, because it is not the energy of water you are using, in the way you are using the energy of oil when you use it in your car.
    But it seems like Chris will soon develop on that ;-)

    Have a nice day
    Sebzefrog at hotmail dot fr

  9. Hey SebZeFrog,

    Nice to hear from you dude. Hope you are well. I didn’t realise that the water powered vehicle story started in France. Nice summary too. Thanks.

    I touched on some of the engineering difficulties with Hydrogen in the Part 5 of the series. When it goes wrong, it goes horribly wrong… Still the Hydrogen economy myth keeps rearing it’s head. The big difference between Hydrogen and Oil, is that Hydrogen can’t be mined from the ground, unlike Oil. There’s plenty of Hydrogen about, but no ready supply because it’s locked up in other molecules like water and the energy required to split it is more than you get from the burning of the Hydrogen and Oxygen collected. What do they say, “There’s no such thing as a free lunch”. Still, it does keep rearing it’s head!

    Regards. Chris

  10. One thing that caught my attention

    Chris is correct about
    1. water pressure
    2. splitting the water to use in a I.C.E. vehicle

    But listen at about 27 seconds “the generator takes hydrogen from the water releasing electrons that power the car”
    so i have to ask in the words of Paul Harvey and now for the rest of the story

  11. Using Chris’s figure of “17.4kWh to travel 100km” indicates that for a return commute of 20km you would need about 3.5kWh. In Melbourne we’re generating 1600kWh/annum (4.4kWh/day) from a 1.44kWp array. We would be getting about 1800kWh/annum if we didn’t have some shade from a chimney hitting the panels in the afternoon. (Limited north facing roof and Council restrictions where we could put the panels as we’re in a heritage overlay area.)

    After some work on reducing electricity use and installing an instantaneous gas boosted solar hot water system we’re down to around 3000kWh/annum (8.2kWh/day) electricity use with some potential for further reductions.

    The price of rooftop PV installations has dropped since we bought ours 2 years ago even with reduced rebates.

    So with around 5kWp of PV on a north facing unshaded roof you could supply – on average – a reasonably electricity efficient house and an electric car for a commute. An installation of this size is well within the budget of many people now and as the Chinese PV manufacturers crank up production the price is falling further.

    Cheers

    David

  12. Hi David,

    Thanks for your comment. You are getting some good generation potential at your site. Melbourne has about 2.5 peak sun hours per day over winter so there is useful PV power to be made even during winter.

    Well done on lowering your daily average power usage. Yep, the watt that you don’t consume is the cheapest of the lot!

    A 5kW PV system is getting more affordable. I’ve seen panels recently being sold for $1.10/W (incl GST) for 190W panels. Very cheap, I don’t know how they produce it.

    Regards and keep up the good work!

    Chris

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