Pool pump/filter running off 12v battery, charged by wind turbine.

[Mack56]

Hello,

I have a small 7ft pool in my garden and need a pump/filtration system. I would like to run it as constantly as possible. Solar power isn't an option as I'm in the UK and I doubt it could provide enough power for a pump elsewhere anyway.

I'm wondering whether I can run the pump off a 12v battery and charge it using a wind turbine. The pumps are 25w off 240 so only 0.1 amps. The car battery is probably 6amps. Will I need a transformer to take the amperage down?

It's quite windy where I am so a trickle charge to the battery might work.

I'm not an expert in electronics and its an ambitious project but would like to know how feasible it is and the components I would need.

 

[rjenkinsgb]

Hypothetically, yes - but solar panels with the same typical output would usually be simpler and cheaper.

The small wind turbines sold to consumers in the UK have the output rating equivalent to being in a gale at 300ft above ground, or something equally ludicrous.

You would be lucky to achieve 5% - 10% of that rating, on average. Unless you life on a mountain top where the wind never stops & can mount it at double the height of any obstructions nearby?

The average output from solar panels is also a fraction the peak rating - but you can get the full output at times, at least.

The other problems involved are inefficiencies in voltage conversion. Unless the power source is specifically designed to charge a 12V battery, it will need a converter there that loses some power.

And, converting the battery voltage to 240V AC will also be inefficient.

Also note that "Car batteries" are not suitable for such use, they are wrecked by a very few discharge cycles; you need a deep discharge or "Leisure battery" type as used for electric buggies or caravans & boats etc. for running 12V gear.

You can get optimising adapters for solar panels to charge 12V batteries, that adjust the load to the light and keep the best possible output power.

Are 12V filter pumps of large enough size available? If not, an inverter would be needed to convert from DC to 240V AC.

It would need some kind of auto switch to enable and disable the pump, depending on the battery charge state.

 

[Lo_volt]

There's surprisingly little energy in wind until you go large. A 1-meter turbine probably won't reach 100 watts in a good wind.

Read through www.electro-tech-online's alternative energy forums:

https://www.electro-tech-online.com/forums/renewable-energy/



For other resources there are a few other forums and the like that are also worth reading listed on electro-tech-online:

https://www.electro-tech-online.com/threads/links-to-alternate-energy-websites.22448/

I like fieldlines.com myself. There are a few experienced turbine builders with a vast collection of hands on experience.

 

[Nigel Goodwin]

Solar power isn't an option as I'm in the UK and I doubt it could provide enough power for a pump elsewhere anyway.

Perhaps you haven't noticed the UK is all but covered with solar Panels

There are fields and fields of them, and multitudes of houses with solar panels.

As already suggested, you would probably need a reasonably sized wind generator, in order to produce an 'average' of 25W+ 24 hours a day 365 days a year.

I would imagine solar panels would be more viable, and using a 12V pump rather than mains would remove one level of inefficiency.

A visit to C.A.T. might give you some ideas, plenty of books to buy, and perhaps even someone to ask:

Centre for Alternative Technology

To avoid disastrous climate change we must take radical action now. CAT offers practical solutions and hands-on learning to help create a zero carbon world.

cat.org.uk

I've not been for a very long time, but it was always a great day out.

Edit - here's some info actually off their website:

A renewable energy technology could be ideal for pumping water where there is no mains electricity available, as a grid connection may be expensive and a diesel generator noisy and polluting.
Sizing a pump
The two main factors to consider when seeking a suitable pump are the flow rate – the amount of water that the pump will deliver, and the head – the height through which it will raise the water. These are related, as increasing the head will decrease the delivered flow. It’s important to minimise bends and other friction losses in pipework, as navigating these will require greater pressure, and as pressure and head are directly related, this effectively means a greater head.
Manufacturers’ technical data sheets will give the performance range of each pump, with graphs showing optimum combinations of flow and head. A pump sized properly to your needs will operate most efficiently. Suction pumps are limited to a depth of a few metres, so to draw water from a well or borehole, you’ll almost certainly need to lower in a submersible pump. Pumping wastewater or sewage necessitates one designed to handle drainage or effluent.
Small electric pumps for circulating water could cost tens of pounds, whilst those for drawing water from a well or borehole supply are likely to be a few hundred pounds. The main cost will be providing power to the pump, particularly when off-grid. Therefore, do first take all appropriate water-saving measures (such as spray-head fittings, mulches on plants to minimise water loss, etc) as these easily pay for themselves in the energy saved by reduced demand.
Off-grid electric pumps
Meeting a year-round water demand with a renewably-powered pump may require a combination of PV panels and a wind turbine, as this will balance energy production over the year. Sunshine and wind are naturally intermittent, so you may need some form of storage. Pumping water up to a tank (with demand then fed by gravity) during sunny or windy periods is more efficient than transferring the energy to batteries. If storing lots of water, you’ll need to balance the costs of a large tank (and supporting structure) against the costs of batteries (and their environmental impact and toxicity). An inexpensive control system can pump when needed, and otherwise divert power to batteries, giving extra backup facility.
The price of a small-scale renewable energy system will depend on the power and the maximum capacity needed. A very rough estimate is around £5 to £10 per installed watt. Siting generating equipment close to the pump minimises the cost and power loss incurred by cabling. As small turbines and PV panels usually produce power at 12 or 24 volts, a low-voltage pump would enable you to do without a costly inverter (for stepping up to 240 volts).
Mechanical pumps
For larger-scale pumping applications, you can avoid the losses in electrical systems by using mechanical power directly. See for example the question on our wind power page about wind pumps, or the question on our hydro power page about hydraulic ram pumps.

But why not, as it's in your garden, simply power it from the mains? - it's likely to work out cheaper.

 

[Mack56]

Thanks for your replies.

The pumps I'm looking at say they have a transformer to take the voltage down to 12v DC so wouldn't that make it easier? I'm not sure about current.. does that depend on the motor draw or would the higher current of the battery wreck the motor?

The pool is quite far from my house so I was thinking of charging a car battery then taking it down and filtering it for at least 8 hours. Not every day though. The wind turbine was a side thought but maybe not worth it I gather. Although if it could charge the battery over 2 or 3 days then have the pump on for 8 hours and repeat. Maybe that could be of some benefit.

I could get a solar panel but wouldn't they be very expensive to be worth using? Especially in the UK.

 

[Diver300]

I'm not sure about current.. does that depend on the motor draw or would the higher current of the battery wreck the motor?

No. The pump will take what current it needs.

A fuse is a good idea with a car battery in case something goes wrong.

 

[unclejed613]

there's also a device called a "hydraulic ram" pump that doesn't require any power at all, just gravity. not completely sure it would fit in your application, but i thought it was worth mentioning... https://en.wikipedia.org/wiki/Hydraulic_ram

 

[Nigel Goodwin]

there's also a device called a "hydraulic ram" pump that doesn't require any power at all, just gravity. not completely sure it would fit in your application, but i thought it was worth mentioning... https://en.wikipedia.org/wiki/Hydraulic_ram

Except it requires gravity fed water to power it - like a stream running downhill, or a waterfall. There's also a different type which requires much less pressure, I was watching a video about it last night.

 

[Mack56]

Interesting machine, never heard of it before but I was wondering if something like that existed. I don't think it would work though. I could have a tank of water above the pool that feeds it. Then put the outlet back in the tank, but I'm pretty sure the tank would soon run dry as the outlet volume is less than the waste. If the tank was big enough and lasted 6 or 8 hours then it could be of use. Then pump the water back.. I guess that could improve efficiency.

Another way could be osmosis but might be difficult to engineer.

 

[Pommie]

When you say "7ft pool" is it 7 foot diameter, long deep? What is the volume of the pool? What is it used for - fish, swimming, growing stuff?

Mike.

 

[Mack56]

It's a 7ft diameter swimming pool. I have chlorine in it and a cover but I don't think it will be enough to keep it clean for long. Therefore I want to have some kind of pump/filtration system but preferably without using mains electricity.

 

[Nigel Goodwin]

It's a 7ft diameter swimming pool. I have chlorine in it and a cover but I don't think it will be enough to keep it clean for long. Therefore I want to have some kind of pump/filtration system but preferably without using mains electricity.

The cheapest, easiest, most reliable, and least maintenance way would be to simply run mains to it - windmills, solar panels etc. are all going to be expensive to install, have serious drawbacks, and on-going maintenance costs. Mains will also give you lights, and anything else you might ever want.

 

[Lo_volt]

To add to Nigel Goodwin's comment, if you run mains to it, be sure to get a qualified electrician to do it. Swimming pools are at a level of hazard that will require a proper installation with ground fault protection and the like.