One big problem with non-centralized solar power generating systems is that, while solar panel, inverter and charge controller technology has advanced greatly in the past 20 years, we’re stuck with 100-year-old battery technology. Household deep-cycle batteries are mostly just hugely beefed-up car batteries – they’re enormously heavy, enormously expensive, and have strictly finite lifespans. Unlike everything else in the system, they’re expendable commodities.
This raises a big cost issue with people who have places in the boonies but don’t live there full-time. Their battery costs are as great as those of full-time residents but the expense of new batteries may not be worth it to them.
Which is why, when part-time neighbor TC died, amid the sadness and lost what-if’s an opportunity arose.
TC never got to really develop his property. He had one of those big prefab sheds trucked in, he had a solar power system installed in it, and then he spent two years fighting cancer and I basically never saw him again.
TC died, his son contacted me as caretaker, drove down from out of state to look over the property, and I think he plans to put it up for sale. That could take years, and during those years the solar power components will probably be fine but those already two-year-old batteries will continue to deteriorate.
Meanwhile I have a neighbor whose very expensive battery bank is in the process of giving up the ghost. It must be replaced, but it would cost on the order of $4000 to do a full-on job of it. The property is only used two weekends out of the month tops. Lately, with Monsoon, quite a lot less. A less-expensive alternative would be good.
I’m the caretaker there as well. I won’t cheat either party, but the living are worth more to me than the dead. So I did something I do only very reluctantly: I played middleman. I pointed out the possible opportunity to my neighbor, I explained – but did not overstate – the entropic facts of life to TC’s son. I offered my services as intercessor.
Sums were offered, sums have recently been accepted and will no doubt change hands in due course. And then – oh, my aching back – I’ll be schlepping batteries around. My neighbor got his cheaper alternative, TC’s son got a cash infusion in return for something that he didn’t value and that would otherwise be wasted, and I get goodwill.
Long-time readers know that’s not nothing. I live on goodwill.
I’ve occasionally wondered about the feasibility (and cost), or a gravity-driven electricity storage system. A tower, with a motor at the top which, using excess electricity generated during the day, pulls up a weight which is lowered on demand in the dark hours, thereby running the motor backward and re-generating the electricity which was used initially to raise the weight.
No idea what such a system might be called, but is there any reason it wouldn’t be practical? There are moving parts to worry about of course, but no acids.
Have to be a helluva tower, to generate significant nighttime power. Interesting low-tech solution to a high-tech problem, though. The big problem with solar, even in regions that get a lot of sun, is that it only works 1/2 – 2/3 of the time, hence the need for big expensive battery banks.
A private “Banks Lake” project is feasible in certain locales. Pump water uphill while the sun shines, drain the lake in the dark. I’ve done the calculations and it’seems a real possibility on my 20 acres.
Jaberwok, gravity-driven electricity storage has been around for a long time. Only instead of a tower they use the height differences in natural terrain. The “weight” that they pull uphill is thousands of gallons of water. It’s called pumped-storage hydroelectric. https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity
instead of a tower they use the height differences in natural terrain
I’d heard of that idea, and it’s probably the source of my own thoughts on the topic. I generally think of the towers as adjuncts to a Lunar colony (no lakes on the moon!).
I realize that even if such a tower set up would work, it probably wouldn’t be economically feasible for our host, and not economically worthwhile for most other people.
And not a lot of gravity. 🙂
Seems to me that if you wanted the “lake-bank” to perform anything like a battery-bank you would need some sophisticated controls so as to provide instantaneous power equal to the load at any given time. If not the lake would have to be generating power continuously at night or when it’s cloudy thereby draining the lake needlessly between load demands. Such controls would have to have batteries, capacitors or something to provide the instantaneous demand until the “lake-bank” is brought online (with modulating water valves I would presume) to supply the sustained demand. I suppose you could just let er rip all night but that would be pretty wasteful of the stored power in your “lake-bank” – especially if the next day happened to be cloudy.
And not a lot of gravity.
True dat:-). But that’s why you use a lot more weight, and a very tall tower! It would have to be at least slightly pressurized too to avoid vacuum welding. Still easier than hauling tons of batteries to the moon though, or fabricating them in situ (I’d think anyway).
They have one back near where I come from:
https://en.wikipedia.org/wiki/Seneca_Pumped_Storage_Generating_Station
It’s too bad nickel iron batteries aren’t more common, 30 + year life spans would be good.
As far as power storage on the moon, it would make more sense for them to do that by electrolysing water into hydrogen and oxygen with solar power during the “day”, and then burning them to create electricity at night. They are already going to be breaking down water into those two chemicals for propellant.
Joel, are those the batteries you were discussing a while back, some of which had apparently frozen and split their cases? How did all that turn out?
Oh, no. Those were inside an old golf cart that had been left outside and uncharged for years too long. These are the same make and model of battery, but only two years old and always charged and pampered. They should be good for 4/5 years minimum, especially the way they’ll likely be used.
And while you are disconnecting, reconnecting, lifting, hauling batteries around you’ll be wearing your full personal protective gear from head to toe, right??? And have a hose spewing water nearby in case… Of course. Silly of me to ask.
Pull up a heavy weight with spare electricity, let it drive a generator as needed – great idea!
One thought:
So as to generate power for as long as possible, you use a high tower and a HEAVY weight, then use reduction gears &/or brake to drive the generator at the appropriate speed from the descending weight. Exactly how you maintain speed control has me puzzled at the moment.
What exactly IS the appropriate speed. This depends on the generator, but generally:
Generator Frequency (f) = Number of revolutions per minute of the engine (N) * Number of magnetic poles (P) / 120
For a four pole generator, and since we want 60 Hz generator frequency (for the US), we get N = 120 * 60 / 4 = 1800 rpm. For a two pole, it’s 3600 rpm.
A gearset that changes downward motion of a weight to 3600 rpm drive to a generator and transfers significant power could be somewhat noisy – kind of like how an air-raid warning siren is noisy, but at a MUCH higher pitch.
One kilowatt hour equals 2,655,223.74 foot-pounds. That equals lifting / dropping a 13+ ton weight 100 feet, assuming 100 percent efficiency up and down. Compared to what it would cost to set that up, batteries are essentially free.
Problem with most of these approaches is that you never get as much return as you initially put in . . . inefficiencies, etc.
The pumped water storage is economically feasible because you pump the water up during a time of lower use at lower rate per kwh and run it back down thru the turbines at a time when you can charge more per kwh.
TANSTAAFL.
😉