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yahoo2
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Posted: 14 February 2017 at 6:05am | IP Logged Quote yahoo2

One of the habits I have developed over the years is to sit down with a pencil and paper and a few excel spreadsheets every three months and revisit some aspect of renewable energy.

What I am looking for is a new loophole that will change the cost or efficiency of a system.

Surprisingly, they never stop coming, I thought I would be tapped out for Ideas in a couple of years after all its all pretty simple right! sun hits a panel, wind turns a motor blah, blah ,blah

"how hard could it be, where is my hammer" copyright J Clarkson top gear.

So here is a few examples that are quite simple.
buying a new chest freezer
if we choose a freezer with an inverter motor drive and an external condenser rather than a conventional motor and condensers built into the freezer walls we pick up efficiency by heat not leaking back into the cabinet through direct contact and the lack heavy motor current draw on startup means that there is potential for a smaller inverter to be fitted to the system. Careful positioning of the freezer so that it gets a rising cool draft up the back over the condenser further cuts the power usage, less power used at night means potentially a smaller battery bank.

So what else runs at night, well for most offgridders the big one is a water pump they suck a lot of juice over a day. Sometimes we get lucky and find secondhand large pressure accumulators, give them an upgrade with a new bladder and then trigger the pump in the afternoon while the sun is out and WHAM no battery power used to pump water.

Change the refrigerant gasses on an A/C and fridge to a hydrocarbon propane butane mix with the right specs can drop the power usage up to 30%

Anyway you get the picture, 30 or 40 of these little changes add up to a lot. we can fit a much smaller battery bank or draw less power from the grid in a hybrid grid connected system. this in-turn throws our battery charging numbers out the window, each battery chemistry has a charge speed limit.
so we have a situation, particularly with wet lead acid such that if we draw the batteries down to a low state of charge we need TIME to get them back up, with solar arrays designed to maximize the FIT (feed in tariff) and a poor site for afternoon sun, we are not going to make it.

In the past I have split systems in two, the main sets of panels is tilted slightly east to capture more morning sun and a tiny 2 panel setup faces west to finish the absorption and or equalisation phase in the late afternoon, the batteries only need higher voltage and time at this point the current draw is very low.

If we go to a chemistry that can handle a faster charge speed or does not require a long absorption time because of its lower resistance then all this theory can go in the bin. However there are days that are still difficult even with a battery that can rapid charge and there are also days when we want to use power all day and just let the batteries sneak little crumbs of charge in-between our use.

Recently I have been looking at the LG NEoN2 panels.

Now, they are not cheap but they have some pretty smokin performance, some of this is down to fancy new tech but a lot of it is down to attention to detail and perfect build quality. handling cells so they dont develop microcracks and having a good tabbing system to join them is 80% of what makes a great panel and a panel that lasts.

Their 19+ % efficiency means that it is now possible to fit a reasonable amount of output on a home made simple single axis tracker and still keep the footprint and the wind load manageable. We dont need to put all our panels on it and we also dont need to rotated the tracker a full 180 degrees to squeeze every last drop of sunlight, that limits our positioning options and blows our feeble budget. This also applies to sites that get a lot of refracted haze and polarisation in the sunlight, the LG NEoN can bounce light off the topside of the backsheet and into the underside of the cell so under these conditions panel rotation could be even less.

For most people today the savings will be minimal over fixed cheap panels on a roof, not worth the effort.

However, thinking a bit laterally throws up a few tasty options

1. There are deals around that can get a 10 cent per Kwh feed in tariff (rumoured to soon rise to 12 cents)
2. Some families and businesses are thinking about fitting EVSE (electric vehicle service equipment) and charging cars vans forklifts etc DURING THE DAY.

The offsets from the FIT, sucking a small about of offpeak grid power occasionally and the gains from solar straight to EV battery with a level 2 or fast charger charger slashing transport costs can put this into the realms of insanely cost effective. As with any install there is a range of possible cents per kwh depending on how it is used but to put it in perspective nothing I have done in the past even comes close to this combination. In cents per kwh we are talking single digit numbers and that gets our EV fuel costs down close to one cent per km. For comparison my old toyota's fuel costs 12 cents per km.

Given that some business connections pay penalties for unbalanced 3 phase usage and reactive loads, charging EV batteries has the potential to reduce or even eliminate that as well, I am liking the possibilities here.

Anyway enough rambling, hope it gets the old brain cells grinding away. cheers

*note* for the dedicated back shedders, walking or riding a pushbike, electric pushbike, train, bus or mobility scooter and owning (or sharing) a 12 year old super reliable riceburner that was fully depreciated when you purchased it that sits in the shed 99% of the time is still the cheapest form of transport.

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Madness
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Posted: 16 February 2017 at 4:06am | IP Logged Quote Madness

Great write up Yahoo,

As much as I love the idea of a Tracker I can't see it being worthwhile when second-hand panels can be bought for a $1,000 per 5KW. A bit like your 12 year old car scenario, my 10 year old Diesel car did not cost me much and is cheap to run. Still I would love to drive a Tesla but as yet I have not won lotto.

If I came across a second-hand tracker at the right price I would grab it. I know where this is one with SMA control gear on it that has died. The owner may give up on it and if I was to pay to get it I would have to the panels put on a fixed installation in the paddock I may get it. Previous owner of the property has told me there is 2 truck loads of concrete in the ground to hold it up.

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Posted: 16 February 2017 at 11:39pm | IP Logged Quote Warpspeed

A tracker may still have application where suitable space for unshaded panels is extremely limited.

Agree with Madness, secondhand panels are now so cheap that the optimum setup these days is probably a virtual tracker with extra large panel area.

The main problem seems to be in mid winter with total cloud cover. In that situation it does not seem to matter where the panel points as there is only very low level diffused grey light in all directions.

With total cloud cover, you will get more by oversizing the panel area than you will ever get with a tracker. Dollar for dollar it seems more panels will get better winter performance.

I am also beginning to think that the solar controller, provided it is very effectively current limited, does not need to be rated for the full solar panel output rating, but only for the power you actually require.


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Posted: 17 February 2017 at 12:29am | IP Logged Quote chronic

The axial type trackers (ed: panel-on-a-stalk type) look like requiring very robust and expensive
bases and supports so as to cope with rotation with wind loads etc. I suspect
a "lazy susan" type base, ie a racetrack bearing and pivot, would be
more effective.
I have to agree though, it is now more cost effective, where there is the space, to get more panel than to track. Maybe a simple fixed reflector, could add by reflect the sun to the panel in the morning or late arvo (say) when it is more useful, at the expense of some peak output at midday.
It seems dumb to make cells single-sided, for the same amount of silicon and similar processing they could be made double sided and used with simple
reflectors to get a lot more output.
ed - Incidentally for a small system a bbq spit motor would probably rotate a panel OK (?) Don't know how long it would last though.


Edited by chronic on 17 February 2017 at 12:35am
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Posted: 17 February 2017 at 1:12am | IP Logged Quote Warpspeed

A tracker should not be too difficult to make. I started by buying a 2Hp geared motor on e-bay. Removed the three phase motor that came with it and fitted a very small geared stepper motor in its place, contained in a weatherproof enclosure.
The enclosure bolted onto the original motor flange, complete with the original plastic motor coupling.



The main gearbox and bearings are plenty strong, and a tiny stepper motor when sufficiently geared up with its own small gearbox can generate torque far higher than the original three phase motor.

My idea was not to track the sun optically, but merely to drive the stepper motor from a 24 hour programmable timer, so it travelled in one direction for 12 hours for roughly 180 degrees, then reversed and went backwards at exactly the same speed for twelve hours at night.

I never finished this off, because I decided to fit a virtual tracker instead.
It would have made a very simple and very robust tracker.

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Posted: 17 February 2017 at 2:41am | IP Logged Quote yahoo2

Thanks Madness, it was straight off the top of my head unedited so it is a bit rough.

Looking at it again I can see should follow it up with some more detailed explanation. Comparing cost between a larger battery(more independence) versus the community approach of grid hybrid and what it does to the bottom line.

I have stayed away from trackers in the past for a number of reasons, I am thinking that to make it work it needs to be low cost, have a simple structure, robust functional tracking and be very low maintenance. I have looked at a couple of commercial solar farms that do tracking and there a a couple of ideas that should transfer easily to a hobbyist level.

I would like to do a series of topics covering cost effective energy, it frustrates me terribly that "experts" that are interviewed in the mainstream media are still rolling with arguments and opinions based on economics that are either 20-30 years out of date or just plain wrong.
I know I cant change the world, however it would be satisfying if the readers of this forum had their own inbuilt bull button. Knowing when we are being conned is half the battle.


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Posted: 17 February 2017 at 4:35am | IP Logged Quote Clockmanfr

Cost effectiveness.....

The best I can do with a 2kW Solar PV Tracker is $800 cost for materials for the tracker itself, includes ..... Actuator arm,.... control electronics, (Dave in NSW)........ metal and base concrete.

Any bigger surface area of PV than 2kW, then your pushing Wind stress with this particular design to its limits.

This photo shows at about midday setting on one axis, and set for Winter setting on the other axis.





These of mine have coped with hurricane conditions.

See........ http://www.echorenovate.com/purchase-book---make-a-2kw-solar-tracker.php



The below photo is a normal standard rotating design, this one is a 10kW in US, (not mine) looks good... then severe gusting and WHOOPs





Edited by Clockmanfr on 17 February 2017 at 4:43am
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Posted: 17 February 2017 at 7:20am | IP Logged Quote chronic

Have I got this right ?

At $1,000 per 5KW - $800 is 4Kw, ie twice the 2kW panel -
so for the same money two extra 2kW panels could be deployed -
one facing more east, one more west. That would be fixed (robust and no maintenance) and give more power (?)
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Posted: 17 February 2017 at 7:24am | IP Logged Quote Warpspeed

chronic wrote:
Have I got this right ?

At $1,000 per 5KW - $800 is 4Kw, ie twice the 2kW panel -
so for the same money two extra 2kW panels could be deployed -
one facing more east, one more west. That would be fixed (robust and no maintenance) and give more power (?)

That is precisely why I abandoned my mechanical tracker.

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Posted: 17 February 2017 at 11:29am | IP Logged Quote johnmc

Good Day All,
I have 3, 2kw single axis solar trackers cost about $1000 each for the tracker frame and foundations material.
In my opinion if, you have the space dont bother with solar trackers
Where can you get 5kw of used solar panels for $1000 dollars?javascript:AddSmileyIcon('')
cheers john


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Posted: 17 February 2017 at 11:34am | IP Logged Quote Madness

johnmc wrote:

Where can you get 5kw of used solar panels for $1000 dollars?javascript:AddSmileyIcon('')
cheers john


Solar installers, gumtree, Ebay is usually dearer. As time goes by they will get cheaper too. I have seen some selling in 10 - 20 KW lots from upgrades to larger installations. Some panels even end up at scrap metal dealers.

Ultimate is to install your panels flat then they will produce the most power in cloudy conditions (I have proven this over and over). I am intending to end up with 20KW of panels, when the weather is bad here I get about 20% of rated power. So 20% of 20KW is 4KW so on those bad days I get 4-5 times 4KWH. End result 16KWH per day at worst, that is enough to run my house entirely from PV 24/7/365.

What about when the sun is shining brightly and those flat panels are not at the optimal angle? Who cares! 20 KW of flat panels is going to be producing far more power under full sun than I can ever use even in the middle of winter.

Edited by Madness on 17 February 2017 at 11:48am


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Posted: 17 February 2017 at 9:17pm | IP Logged Quote Warpspeed

Amazingly, flat panels can produce more power in total cloud than any other orientation. The proviso being that the panel can "see" the whole sky all the way around ideally right down to the horizon in all directions. That is usually not possible, but its the ideal.

Flat panels work pretty well in mid day summer sun too, but the main benefit will be in the worst darkest cloudy wintery conditions. If you are building a virtual tracker, a very large area flat array will be the highest power producer (per panel) in total cloud.

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