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Forum Index : Solar : Tiny Solar - Large Post
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| Shaz_Au Newbie  Joined: 31/10/2012 Location: AustraliaPosts: 11 |
Hey Guys, I'm currently constructing a new back shed! Initially there won't be power connected so I would like to try and power the basics such as lighting using solar. This is a "back shed project" I understand this system will not be the most economic solution to power my shed. I've already got 3 phase to the house and a grid-tie solar system but I would like to learn more about off grid power and this seemed like the ideal project. As my shed is literally a pile of bits of steel in the backyard at the moment, this will be a longish term project. The bits I have so far: - Steel bits for 6x13m shed - 2x 24V 120W solar panels (see my Topic in "Price Watch" for panel details) - 12x 12V 5Ahr SLA batteries (in good condition ex UPS) Even though this is not the most economic solution cost is still an issue! BATTERIES: Yes I know the battery pack is small but I thought it would be a start and it was free! I've read about parallel battery connections here: http://www.smartgauge.co.uk/batt_con.html I understand that I will need some sort of dc rated fuse or circuit breaker between the battery and regulator REGULATORS: I'd thought initially I would go with a 24V system so I could have a higher system voltage while still using a cost effective PWM regulator with a digital display such as the STECA PR3030 and fairly common 24v inverter. I even thought I could have two separate battery banks with a switch or two completely separate systems to help reduce the issue of paralleled batteries. Obviously with all the small batteries and looking longer term a higher pack voltage of 48V would be better. This got me looking at the Plasmatronics Dingo and also the cheap MPPT solar converters on ebay for about the same money. The Dingo is obviously more versatile than the steca but I don't understand the differences between negative/positive grounding and the display seems to require lots of scrolling to reach the info you wish to view, shunts and datalogging interfaces are extra. The cheap MPPT inverters make a lot of promises but there is very little I could find about how they perform in the real world, I would also need to invest in additional panels to increase the voltage on the panel side of the inverter. LOADS: Possible loads include: - Lots of fluoros, not necessarily all at the same time (see below) - a small pressure pump to run a single tap off the rainwater tank (either 12v using dc-dc converter or 240v via inverter) - Down the track I would also like to run some power tools such as a drill press, grinder, etc. With the lighting I wasn't sure if I should use low volatage ballasts that match the system voltage and have the advantages of higher efficiency (not going from 48v-inverter-ballast) and me being able to wire them myself (low voltage). Cost in ballasts and larger cabling for the DC are the disadvantages. Alternatively I could put the money saved by using standard ballasts towards an electrician to wire up 240v fluoros and purchase an inverter to suit. Thank you if you read my entire post  Your feedback and suggestions would be welcomed!
Cheers, Shaz |
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norcold Guru  Joined: 06/02/2011 Location: AustraliaPosts: 670 |
Batteries are too small, but you know that. I`d go with 240v flouros and an inverter. You can get very cheap 12v or 24v diagpharm pumps complete with pressure switch on Ebay. Have had a good run with these, they have thermal protection but you can carefully wrap 1/2 inch copper pipe (soft) around the motor to allow them to run continuous. Probably not neccessary for your use. Change bearings every two years or so, their brilliant. Main thing have fun, as you`ve illustrated with the $79 120w panels, it no longer costs the earth. We come from the land downunder. Vic |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
I would wire the shed for 240 VAC and set it up as any standard shed wiring, power points and lights. Because, as time goes on you may choose to need a grid connection for heavy shed loads like compressors and welders etc. Then as a stop gap, use the solar and battery bank you have, and whatever inverter you can get your paws on for the best dollar that will cover your base needs. Like you say, not everything needs to be on at one time, adapt and adjust as needed. Just dont buy a "PowerJack" inverter, they are pure rubbish. As for your water and pump, install a small headed tank in/on the roof and use a pump to fill it when needed, its far more cost effective to run the pump to fill a header tank when needed than running a pump on demand for a single tap. There will be times you have full batteries and lots of solar, so better to pump water then and store it than use power on demand to run the tap. I think fluros are the best shed lighting, but im not sure if they are so efficient off an inverter. Some years back i done some quick tests with a square wave inverter on fluros and incandescent light globes, and the fluros drew more current for their rated output than the incandescent light globes did. I have been meaning to repeat the tests with modified and true sine wave inverters to see if the results are different. I would expect a different result, but its not tested as far as i have done. The trick is with your lighting is to break it into single switches for each light, then you only use power to light the area needed and not 1 switch for all the lights. You have a choice of your panels in series or parallel, for 24 or 48 VDC, 24v would be my choice due to the lower cost of inverters, but there is a lesser range in 24v, there is mass in the 12v range and then a big step to 48v which is more to the "Off Grid" inverter range for stand alone systems. The 24v is a good middle of the road but not as well catered for in choice. Have fun! Pete. Sometimes it just works |
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AMUN-RA Senior Member  Joined: 10/03/2007 Location: AustraliaPosts: 144 |
http://www.jgmdirect.com look for the 520mm led light strip for $26.00 I use one of these instead of 4 1.2m flouros 6.50watts at 12 volt and for the price worth every cent for me Every day the sun shines & gravity sucks= free energy. |
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| Shaz_Au Newbie Joined: 31/10/2012 Location: AustraliaPosts: 11 |
Hi Guys, Thanks for your replies. I'm still undecided about how I'll proceed with the solar at the moment. I'm making slow progress on turning that pile of steel into a shed though! Can you clear up one silly question please? To run two 12V LED strips like AMUN-RA has suggested using a 24V battery pack it isn't as simple as wiring the LED strips in series is it? If I was going to try and avoid a 24-12v converter wouldn't I have to calculate the voltage drop across the LEDs and then add resistors until the voltage fell to the correct level? Thanks for the tips on the Pumps Norcold and I'll be sure to avoid the powerjack inverters too Downwind. I might ask for more advice on these once I progress further. Cheers, Shaz |
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| Shaz_Au Newbie Joined: 31/10/2012 Location: AustraliaPosts: 11 |
PS Guys I do plan to wire the shed with 3 phase eventually. I'm just not ready to start the trenching just yet! |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
You can wire them in series as long as you remember that the first LED strip will have a floating negative (at 12 volts) and may need to be isolated from earth. The other alternative is to go with a 24 Volt light strip, I'm guessing it will have 6 LED's in series per resistor pack instead of 3 LED's for the 12 volt strips. I'm confused, no wait... maybe I'm not... |
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| AMUN-RA Senior Member Joined: 10/03/2007 Location: AustraliaPosts: 144 |
Shaz au got my panels today they work but very rough finish sealant missing i places but should be fine for camping and such or to learn about solar how did you go getting the bonus cable and carry bag???? Every day the sun shines & gravity sucks= free energy. |
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