just remind me, Watts = volts x amps yes?

So a 12v bilge pump, with a 1.5 amp draw, could be run off a PV panel with, say a Wp of 30W?

Obviously linking it all up with a SLA would be a good idea, but if want a cheap system that just pumps water round a cooling circuit when the suns out, would this lot work?

http://www.ebay.co.uk/itm/350545631123
http://www.ebay.co.uk/itm/330712846242

How best to control charging/drawing with an SLA?
Im guessing that since the panel cant be counted on producing 1.5A except at peak sunlight, it would just sit there producing <1.5A and the bilge pump not pumping until the sun came out?

Watts = volts x amps yes?

Yes, no idea what you’re on abou otherwise 😛

http://www.engineeringtoolbox.com/electrical-formulas-d_455.html

Bookmark this site.

handy, wrecker, ta.

I’d want somethign that only tripped the pump in once the current got above a certain level – constantly running a small current through it even if it’s not enough to turn the pump may be an issue?

I’d want somethign that only tripped the pump in once the current got above a certain level

that’s what I was thinking. what would be the best way of doing that?

no idea, I just know I’d want one 🙂

I’d say its all way to close. The pump will probably draw a higher current at start-up and the panel won’t give anything like the rated output. That said, being a DC motor it might work, if a little slower than designed.

You will need some kind of control or the pump might overheat if there is some power from then panel but not enough to spin it.

I would set the panel up to constantly charge a battery then run to pump occasionally directly from the battery, possibly on a simple thermostat. You will need a higher voltage from the panel to charge the battery.

the panel can produce a peak of 17v ish so should be able to charge.

Can you connect the pump across the battery terminals while simultaneously the panel is also charging across the same terminals?

I’d have a look somewhere like this;

http://www.campervan-motorhome-electrics.co.uk/index1.html

you may need some sort of split charge ciruit in place. I’d also investigate battery protection – you don’t want to deep discharge it if the sun goes in unexpectedly.

http://www.backwoodshome.com/articles2/yago91.html

http://www.builditsolar.com/Projects/WaterPumping/waterpumping.htm#PVPumps

Fill your boots

Your solar powered pumping system should include a pump controller such as the one in the photo on page 37. Although it is possible to connect the pump leads directly to the output terminals of the solar module, a controller provides much better pump performance and start/stop control. It will also avoid trying to operate the pump in a stalled condition when solar output is too low.

EDIT again; http://www.altestore.com/store/Solar-Water-Pumps/Submersible-Solar-Pumps/Sun-Pumps/SunPumps-PCA30M1D-Submersible-Pump-Controller-6A-Delrin/p4070/

A relay, timer switch or thermostat and battery would be required.

There will be a marine solution somewhere, Fishing livewells often have pumps and timers. Hozelock garden timers hacked?

cheers wrecker – very useful.
Unfortunately a pump controller is going to make the set up too pricey.

maybe I can bodge something from a pond system
http://www.ebay.co.uk/itm/Solar-Powered-Pump-Kit-800LPH-Fountain-Water-Feature-Remote-Control-LEDs-Pond-/330676165522?pt=UK_HomeGarden_Garden_PondsWaterFeatures_UK&hash=item4cfdd5db92#ht_2642wt_952

Bookmark this site.

How long has “E” been Voltage (EMF presumably)? Is that something specific to Engineering, or did Electronics change when I wasn’t looking?

Stoner – no idea what you are trying to do, but I’m fairly sure that panel won’t run that pump in anything but the very sunniest of days in the UK (and even then only if you have the panel mounted correctly with no dirt / shadow etc). Even 50% of claimed performance is optimistic in the real world! But if you put in a 100W panel so it would run on most sunny days it might kill the pump with no protection in there on a really sunny day.

If your flow rate is critical then you should be aware that bilge pumps aren’t known for actually delivering their rated spec under real conditions either! If e.g. you are trying to pass water round a long loop of pipe, I would expect a much lower flow rate than the spec (especially if the pipe is narrower than the bore of the pump outlet). “Detritus” in the inlet also reduces pump efficiency and lifetime, if your system is not going to be very clean. They also aren’t known for having a huge lifetime if used heavily (on most boats they will run only very occasionally).

It’s very American, cougar. Maybe that’s why?

cheers poly.

Im planning on putting a coil of spare 16mm dia UFH pipe at the top of my wine box* and putting a 800L water butt out the side of the shed. Simply pumping (max head needed of about 1.5m) the water around at even a slow rate is all thats needed to keep extracting heat from the box. The insulation works very well, buffering diurnal changes and keeping peaks down, but it doesnt help keep the temperature down at 14degs over the hottest summer months.

[img]https://lh6.googleusercontent.com/-ewHejWmbHRM/TgjoPr6Tm1I/AAAAAAAAACE/Ef_h8ArsEJE/s400/P1000691.JPG[/img]

orange area is outside air temp diurnal range. red/blue lines are recorded inside the wine box.

I’m strugling whether to admire you for bothering to record all this data about your wine store and then being prepared to plumb something in to change it or just being stunned that anyone would be so bothered…

I have some nice wine, I want to keep it that way 😛

You have a wine cellar and you won’t buy a pump controller? 😯

its not that nice

anyway, any ideas what product I should be looking for in a UK supplier – as I cant find “solar pump controller” on eBay

Opps 27degrees thats the white wine ruined better send it this way for enviromentaly safe disposal

http://www.solar-facts.com/panels/panel-efficiency.php

scroll down to

“How Your System Affects Panel Efficiency”

Stoners temp chart may seem unnecessary to some but it did prompt me to create a spreadsheet to record my commute times.

[/url] Bike Data by bushmills77, on Flickr[/img]

You could always dig a hole and put the wine in there. Some sort of cellar structure might work. Or you could make it complicated 😀

I’d look at a cheap solar pond pump kit TBH. They seem to work in gardens without technical input.

this is a handy site on sizing and managing current for solar powered pumps
http://www.solarproject.co.uk/Install%20Tips%20and%20Tricks.html#PVTips

The author was the guy I used to help me set up my solar thermal panels.

Anyway, I think Ive decided to use a 12v pump from him and for now a 240v transformer with a timer switch, and maybe a thermostatic switch unless I can size a 30W+ panel for less.

nice work palmer. never too many graphs on STW.

Stoner,

I figured it was something like that (well I guessed you were trying to cool a greenhouse with a water butt).

Is this approach tried and tested (or theoretically validated)? I’d have expected (1) On really hot days the water butt heats up from both the sun and from the heat it is sucking out the wine store. (2) is UFH pipe a good enough conductor to be effective (I know that sounds silly given it is designed for heating) – but plastic pipe can’t have a great heat transfer coefficient can it? (3) Will the mass transfer in the box be good enough just from convection or do you need a fan too? (4) If that wine rack is full of bottles they have a huge thermal mass and it is going to take an age to cool. Obviously your aim is to keep the air cool so they don’t warm up in the first place, but if they do… (5) Actually given that each bottle has a lot of thermal mass – does it matter if the air in the box gets warm – what happens to the temperature of the wine inside the bottle – that must damp the temperature rise even more?

Stoner – I now know why you didn’t invite me round, you’ve heard of my passion for grape…….

Thanks Stoner 🙂 Is it wrong to be proud of a spreadsheet?