Just floating an idea for the power gurus here.

Would it be practical for a home solar system to have on site storage consisting of a water tank underground and one in the roof, and have excess power from the solar cells pump water to the upper tank, and have a water turbine with generator attached to provide power at night ?

Would this be cheaper and more efficient than storage batteries ? In good conditions could it provide enough storage to fully power a home at night ?

In a word no

There wouldn’t be enough water to power a house over night using water on the roof

Lets say you had 1kg of water at 3m high

The potential energy is p = mgh

P = 1 * 10* 3. = 30 joules

So 1 kg of water being 1 litre in volume would only store 30joules of energy

Electrically you might be drawing 1kw of energy that is 1 W = 1 joule a second

If your house was drawing 1 kw then the joules per second would be 1000 joules a second

If 1 litre had 30 joules , then you can see that 1000 joules a second would require a fair amount if water per second

You can see if you are dumping 33 litres a second

Times that by 60 seconds times that by 60 minutes

How much water would you need. Assuming that you able to convert the flow 100 percent to electrical energy

Rumpole – definitely not.

To put it into some perspective. If the height of the water was 3 metres, and you wanted to store the equivalent amount of energy as a 12 volt 100 amp/hour battery you would require approximately 150,000 litres of water. So two reasonable sized swimming pools worth.

And that’s for one average sized battery.

Fair enough then, thanks

If you are looking at putting this in your suburban backyard probably not. If you built something the size of a normal backyard swimming pool (I dunno … 100 cubic metres). If you elevated so that you had an effective drop of 4 metres (and by this stage building this would probably piss off your neighbours but let’s press on), then you’ve got about 3900000 joules.

That’s about 1 kWh. A standard Australia metric house, as covered in the news, seems to be taken as 1 kW, so you could probably run stuff for an hour. It’s not nothing. But fuck, this would be a lot of outlay for one fucking kilowatt-hour.

If you have a good sized property with some kind of reservoir already existing and a bit of topography: still probably not but worth looking at.

Let’s assume that the

dv said:

Let’s assume that the

Looks like DV’s water ran out.

sibeen said:

dv said:

Let’s assume that the

Looks like DV’s water ran out.

(Gets back on the bike…)

It’s funny, though, to think that I could pump a backyard swimming pool 4 metres upwards in a couple of gym sessions.

…or you could build one of these and get the missus & kids to take turns

you could try wind power though

someone was telling me about a hydro scheme they are proposing, the body of water is in the middle of no where so you’d need to build new power lines to it, the other thing is that you’d only be able to generate 38 MW of power, which in the grand scheme of things just isn’t worth it.

I’d always thought what a great idea until I realised that the flow to the river would mean this huge outflow of water to it for 8 hours say, at the moment its a fairly constant , regulated flow, adding the hydro would mean feast or famine for the river – the set up needs a minimum flow to actually generate and that minimum flow is big.

hydro can only really be viable with a reliable water source and with a large capacity behind it.

in this case a piffling 38 MW just wouldn’t be worth it given the outlay to make it viable compared to coal or gas

Aquila said:

…or you could build one of these and get the missus & kids to take turns

Using an inverter to run a light bulb??? If only they could invent a DC light bulb…

OK, so hydro is out.

What other options are there for on site storage ? Are conventional batteries still the best alternative ?

BUMP

rumpole said:

Are conventional batteries still the best alternative ?

Yes.

sibeen said:

rumpole said:

Are conventional batteries still the best alternative ?

Yes.

How many conventbatts to the Sydharb metre?

I could do with a wind generator, additional to five PVs, 850AH flooded deep cycle LA batteries, and diesel generator.

We tend to get a bit of wind with the cloud and rain that comes through this time of year, not always so still have to go to diesel generator if have three days or so of cloud and I stay up all night on computer with lights on, which I do a bit.

But when I pull my finger out I’ll get to building the fast charger for batteries powered by generator, have (some of the) parts sitting behind me on the shelf. Have to order the toroidal transformers, and it’ll be linear so think I was about to guess the voltage type and wasn’t quite sure, actually it’ll be two or three transformers paralleled at rectifiers, and thought probably have to insert some ballast resistors on them, anyway it wasn’t urgent, clearly.

I like the old school dirty flooded LA, you can flog them a bit on the high voltage charge, cleans them up inside nice, equalizes, get that last 5% or so in too. But there’s always checking and topping up, and the terminals get corroded so you know wire brush job, bit of CRC, have to be careful oil doesn’t migrate around cap seals into batteries, have seen it does a tiny bit so more careful now.

I think with a sun tracker and power tracker I could live on 400W of PVs. Presently peak power is around 500W, summer, middle of the day, hole in the ozone layer, you know when all is ideal.

transition said:

I like the old school dirty flooded LA, you can flog them a bit on the high voltage charge, cleans them up inside nice, equalizes, get that last 5% or so in too. But there’s always checking and topping up, and the terminals get corroded so you know wire brush job, bit of CRC, have to be careful oil doesn’t migrate around cap seals into batteries, have seen it does a tiny bit so more careful now.

You can also drain strain and refill the batteries to get longer life out of the cells.

transition said:

I like the old school dirty flooded LA, you can flog them a bit on the high voltage charge, cleans them up inside nice, equalizes, get that last 5% or so in too. But there’s always checking and topping up, and the terminals get corroded so you know wire brush job, bit of CRC, have to be careful oil doesn’t migrate around cap seals into batteries, have seen it does a tiny bit so more careful now.

Flooded cells can take way more abuse than these new fangled sealed lead acid batteries can, that’s for sure; and generally their life well exceeds that of SLA batteries as well.

>You can also drain strain and refill the batteries to get longer life out of the cells.

Sounds messy, think i’ll just leave the lead in the space in the bottom of the battery.

transition said:

>You can also drain strain and refill the batteries to get longer life out of the cells.

Sounds messy, think i’ll just leave the lead in the space in the bottom of the battery.

Yes messy, if one doesn’t handle carefully but then how else does one handle acids?

>Flooded cells can take way more abuse than these new fangled sealed lead acid batteries can, that’s for sure; and generally their life well exceeds that of SLA batteries as well.

Yeah I’m done with SLAs. Just have to be sure to keep the fluid above plates in flooded batteries, otherwise they similarly too die young.