A new solar system

Duckie

earthbound wrote:

Hmm, it's going, don't think it's doing much though.... It's all running fine on the solar side of things, hasn't skipped a beat. Plant growth is a bit average though, suffering from a lack of nutrient I think. Took a while to cycle and now there's still only half a dozen goldfish in it so there's not a lot of feed going in. We might look at sticking some silvers in soon so we can start the plants really pumping.

That would be awesome!

What sized system have you got this attached to?

vk3laj

My greenhouse system is going to be solar..

Ive got 1 x 100Watt panel, 1 x 40 Watt Panel
1 x 25amp solar regulator
70 ah of deep cycle batteries

Until i can add another 200watts of panels and another 130ah of battery, i'm going to have the solar side as my backup system via an automotive relay..

Battery bilge pump and Battery air pump for emergency power outages

Once ive got a total of about 340watts in panels and 200ah in batteries i'll give it a crack as a 24x7 solution.

http://www.ebay.com.au/itm/DC-12V-60L-M ... 231db8069a is what im thinking as my 12v backup air - to go with the 500gph bilge water pump

solarmon

Hi vk3laj

What are voltage specs of the panels that you have? How will you be connecting them together - in series or in parallel?

What make/model is your charge controller (solar regulator)? Does it support MPPT (Maximum Power Point Tracking)? MPPT is good to get the most out of the panels.

Cheers,

Mon

nebbian

I just ordered a solar panel and pump, and am having a devil of a job trying to find an air pump to put in... so came here to see what you guys used.

And it seems like you're not using one at all!

Are you using an air pump? Are the fish dead? Hmmm... :think:

longnt

Hi EB,

Interesting to see you had built a real off-grid system and how it work.

I was thinking of going green and going off-grid as AP is more or less about going green so I was searching for solar system. I currently have a 105AH battery and 300W inverter for backup purpose. I found a portable solar 120W include regulator for $180, however I is not enough to power my system of 35W water pump + 5W airpump run CF. The higher watte portable panel is so expensive so I search for solar panel & regulator as it is cheaper. I come across MPPT regulator as it is more efficiency, however it is also expensive, then I found a grid-tie inverter that also integrate MPPT and not much more expensive than a MPPT with same A current.

This inverter convert solar power and output directly into home-grid so we can draw back to AP system. The power grid serve as an unlimited power storage (battery). This way we only need small battery for back up purpose and we can keep all 240V pumps/timer. The only draw back is that it won't run if power grid is down so we can't use solar power to run AP when power grid down at day time (usually power down at night most of the time) unless we install some switchs to divert solar power to regulator.

I know that it feels great to go off-grid completely but imagine that if we put 1KW into the grid then we draw back 1KW from the grid for AP is the same as we run off-grid 1KW (at least mathematically but I think many or maybe most of EB's customers won't think it is the same unless you can convince them).

There are many advantages of use the solar power this way, just list a few:

- Eliminate the use of 12V gears that are so expensive or unreliable.
- Reduce cost of battery as off-grid requires extra battery capacity to account for cloudy days, more chance of running battery flat that reduce its life.
- No waste energy from solar panel when all battery is fully charge (many continue sunny days). We may put more energy in to the grid in summer then draw it back in winter the same as we save some money in the bank everyday for some rainy days.

Some solar stuff I intend to buy in the near future:

- Grid-tie inverter 500W, $200: http://www.ebay.com.au/itm/500W-Grid-Ti ... 942wt_1163
- Solar panel 250W, $250, may buy 2 of them: http://www.ebay.com.au/itm/321017098861 ... 715wt_1108

After install this 500W solar power in the system I will have about 5hr*500W*95%=2375W/day save into the power grid ($0.5) bank account. I will think of put more stuff into the system to have more fun :cheers:

.

Cheers,
Long

Ronmaggi

An easy way to look at it is why add another point of ineffency, point of failure, and more wiring, when you can get a pump that can run on the native voltage.

solarmon

Hi Long,

I too have a 4Kw grid-tie solar setup.

The main problem with (typical/standard) grid-tie inverters, as you have already correctly pointed out, is that it does not protect you from grid power failure. So you will still want/need some form of power backup if that is the end game.

Also, the cost of importing electricity is typically more expensive than exporting it to the grid. Thus, exporting 1Kw and then importing 1Kw will cost you more (unless your you have an analogue import meter and it runs backwards... :whistle:

)

On the flip side, the cost of purchasing, installing and maintaining an off-grid solar setup and battery bank can be costly too, depending on your requirements.

One of the benefits of using 12/24V DC compared with 110/240V AC is the low voltage - which will mean it should be safer to work with, especially in and around water. Yes, it maybe more cheap/efficient to run an AC pump using direct AC power but you have the hazards of working with higher voltages.

However, working with high DC current in the batteries also has its hazards and you still need to be careful; and DC cables runs (compared with AC at same current) needs to be thicker (and thus more expensive); and shorter to keep power losses down.

You can make a 12/24V DC setup efficient by not converting to 110/240V AC - i.e. don't use an inverter - and just power directly yo 12/24V DC equipment. Although, as you pointed out, DC equipment tend to be more expensive than AC equivalents (but can be more efficient).

With regards to 'excess' solar electricity generation - i.e. what to do when your battery is fully charged and the sun is still shining. The typical way to handle this is a 'dump diversion' and this is usually is in a form of a water heater. Thus, you can use the excess electricity to provide hot water for your house (or FT). However, again, all this will mean more equipment and expenses.

IMHO, the most important aspect of a backup system for an AP setup are the air pumps. Thus, this should be given priority in terms of power consumption off the batteries. I would say, let the pump fail due to power failure and try to keep the air pumps going as long as possible on the battery bank. I suspect the plants will survive much longer without water (flowing/running) compared to fish without DO. If you think you have enough battery power then power a smaller (in terms of power consumption) separate water pump to provide at least some water flow through the system.

Cheers,

Mon

Raskal311

Our power company will credit you exactly what you export to the grid so no negative impact in cost per wattage used/sold.

solarmon

Hi Raskal311

I'm not sure what it is like in the US and Australia, but here in the UK, the FiT (Feed-in-Tariff) for solar works as such.

You get paid for two things:

1. Generation - you are paid for the amount of solar electricity you generate, regardless of how much you use or export. For me I get paid 21p per kWh.

2. Export - you are paid for the amount of electricity you export to the grid. If you do not have an export meter (which most don't until 'smart' meters are fully introduced) then it is calculated as 50% of your kWh generation figure. Depending on your household this may or may not be a good rule. For me this is 3.2p per kWh.

My electricity supplier (British Gas) charges the following:

1. Import - 11.98p per kWh
2. Standing Charge = 15.020p per day

You can see that my export payment (3.2p per kWh) is much less than that British Gas charges me for importing (11.98p per kWh). Thus, it makes financial sense to try to use up the electricity rather than export it to the grid, especially if the 50% of Generation calculation is used.

Cheers,

Mon

nebbian

nebbian wrote:

Are you using an air pump? :think:

Bumped because I would really like to know if you are using an air pump at all?

earthbound

We aren't using an air pump in ours.. The air pumps are there only for backup, for when the power goes out..

nebbian

Lovely, thanks for that.

I'm assuming you'd say that solar is more reliable than 240 V, so you don't need the air pump as the water is oxygenated enough by running through the growbed and falling back into the tank?

earthbound

Basically yes... Though our system can't be stocked as heavily because the pumping cycles have been cut right back. If we had more panels and batteries we could stock it the same..

nebbian

So with a 130W panel, a 100 Ah battery, and a 20W pump running at 50% duty cycle, you were having issues with running out of juice?

Back of the envelope suggests you should have been fine... No substitute for real world experimentation I guess.

4thavenuebhs

Looking forward to it Joel, hope it’s going to be a successful one.

Backyard Aquaponics
A place to discuss aquaponics