Author Topic: Blasphemy..... Solar power.  (Read 148432 times)

BruceM

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Re: Blasphemy..... Solar power.
« Reply #135 on: October 23, 2017, 04:33:07 AM »
Yep, the ongoing replacement cost of batteries is a serious issue. 

I had to scale back my solar hot water plans after crunching the numbers.  With a super insulated home, my heating costs were too low to allow for a fancier setup.  What I settled on works great, but I didn't get surplus free heat to heat the shop, which would have been nice.

starfire

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Re: Blasphemy..... Solar power.
« Reply #136 on: October 24, 2017, 04:07:03 AM »
Having a off grid battery bank is a pain, and actually limits what can be reasonably done with solar. A grid tie setup allows greater possibilities.
For me, I use around 2 KWhrs per day. To have a unstressed battery bank, it needs to be roughly 5 times this amount of storage to keep within a small  20 percent Depth of Discharge to make it last a reasonable time. Mine is 1500 Ah lead acid.  To charge the daily losses/use  takes around 2.5 KW hrs charging . To get this at my location with untracked panels requires around 500 watts of panels,  with around  5 hours of useful sun, easily achieved in summer.  On rainy days I see around 5 to 8 amps, worth having but unable to supply demand. More panels would easily increase this, but also supply way too much current in bright sun, they would throttle back via the controller in a very short time , therefore money not well spent.
Where battery banks really shine is with diesel backup, a few hours of generator time is all thats needed to give power 24/7 on demand via inverters.  It matters not to me whether the power is derived from solar or diesel, both are free energy sources for me, but not having to crank the Lister every single day is nice. Some things actually do work out in our favour, the Lister works harder in winter, just when the extra heating is a bonus for an example..
For anyone interested, and even further off topic, have been when time allows, messing with a charge controller that maximises low light  panel output. The concept I have come up with simply uses the panel/s to charge a largish capacitor to whatever voltage the panel can maintain in low light. A very simple differential comparator circuit monitors the delta, or rate of voltage change across that cap,  and dumps that "package" of energy into the bank when no further voltage increase is detected. The faster the delta, (DvDt) the higher the switching rate of the Mosfets. it is basically a high power relaxation oscillator the frequency of which is a product of volatge change and current.
 This reduces the bright sun performance by around half, but nearly doubles the low light performance, even allowing a few amps in average moonlight. I live in a tropical rain forest, so this kind of performance  I think will give me a better long term result  using solar.... as has been  said, panels are cheap, the limitation is now low solar radiation on shitty days.
A fascinating subject for sure..

Samo

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Re: Blasphemy..... Solar power.
« Reply #137 on: October 24, 2017, 12:11:09 PM »
Glort,

Sounds like 2 steps forward one step backwards but you seem to be making progress  ;D  For my setup I used a serial to Wifi dongle to send the output of my inverter to a computer, it just displayed a line by line update from the inverter, after a while I wrote some software to massage it and send it to a web server, so I had some graphs and history... the Serial to Wifi dongle was called FIREFLY & was pretty powerful with all the options it supports....  took a bit of fiddling to get it configured, but once it was it just worked...

Just an idea if your inverter has a serial port, most of them have some type of port if they don't support BlueTooth.

cheers,
Samo

Lister CS 12/2 & JKSON 10/1 Listeroid

starfire

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Re: Blasphemy..... Solar power.
« Reply #138 on: October 24, 2017, 01:52:43 PM »
Your observations are similar to mine in that some cloud can actually increase panel output. I put this down to cooler panels being more efficient, and this is what got me into a "cloudy day" controller.
My power usage is low in a domestic sense,  lights, my biggest useage, and my electronic workshop.
The other workshop, where I do light engineering and car/motorbike restoration work runs seperately off the Petter, max 5KVa.
Cooking/water heating via gas/oil and wood burner. I have an old fashioned "safe" to keep food cool, refrigeration not really needed with vege garden and meat on the hoof so to speak. This way of living was common a century ago, and for centuries before that. I see no harm in forgoing coffee makers, heated towel rails and all the other crap you city dwellers deem  indispensable....
Would a Lister actually feel comfortable running a heated towel rail?
Clip a high impedance multimeter to one of your solar panels , and monitor the output voltage under varying light conditions. Low light levels effect current dramatically, but the voltage remains fairly constant and when in darkness it will suddenly drop. No commercial controller is designed to work at these levels.
The idea here is to create what effectively is an impedance converter, where the milliohm battery impedance is matched to the high impedance of a light starved solar array. The capacitor passively does this by charging at the highest possible rate, the peak stored energy then dumped into the bank as a series of high current pulses.This is the electrical equivalent of a ram pump, the battery bank being the equivalent of an air over water collector/pressure tank.
Now, connect a largish capacitor across the same panel, and connect a small load, a flashlight bulb will do. You will get a brief flash as the cap  gives up the stored energy. This is the rudimentary concept of current collection over time.
On cloudy days Its better for me to get 16 hours of 22 amps, than 16 hours of 13 amps, the tradeoff is to  take a peak current hit mid summer, but then  nights are shorter and less lightinng time required. 
Im not sure what differences there are in different brand panel performances in low light, I have a very  old mitsubishi 80 watt panel, and 4 similar no name 100 watt Chinese panels that are new, these are what Im working with. As I said, its an experimental setup right now,, lacking any refinements such as over voltage protection for the bank.... purely a proof of concept . The next phase will be to add a voltage up converter to lessen the static battery bank voltage threshold, the equivalent of seriesing more panels.... here it gets tricky, as circuit complexity increases, so too does phantom current draw.
Right now we have a partial moon surrounded by scuddy clouds, Im seeing around 4 pulses a second, with a  4700mfd cap this is around 2 mJ, which is bugger all..... a few hundred mA at most.
 A dull overcast day, this rapidly increases to 120/200 J, there is a  nonlinear relationship between photons and current (Coulomb',s law)
In  bright sun, Im getting around 250/300 J, around 1/2 - 2/3rds of the max, at this point the panels are effectively tied to the battery voltage with a 80/20 pulse ratio.... the cap cannot charge instantaneously.... hence the loss.  measurement  made more difficult as the cap dis/charge rate is logarithmic, so ball park figures  here.
With solar, there are so many variables.
But, as you are on the natiional grid, non of this has any relevance to you.

BruceM

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Re: Blasphemy..... Solar power.
« Reply #139 on: October 24, 2017, 06:05:52 PM »
Some of the mppt controllers are already buck/boost capable- so are capable of doing what Starfire is experimenting with via simpler means.  The losses of running the buck/boost converter will exceed the output for dark/rainy days or moonlit nights.  A tropical rain forest is certainly a climate that would be well suited to a buck/boost mppt charge controller or it's functional equivalent and I applaud his experimentation.

For my high desert climate mppt is unnecessary with my 120vdc system; charging is quite good at low light levels.  With panel costs where they are today,  mppt for most climates is a marketing ploy; as Glort suggests, in almost all cases you are better off putting the money in panels than electronics to try and squeeze the last 20% of power on a semi-dark cloudy day.

In my case, since ultra clean DC was the goal, I used simple analog throttling of PV power via low-side bipolar power transistors.  Today, that design approach is still viable for a higher voltage design.  I used 350V  automotive ignition Darlingtons with a current sensing resistor for each and micropower op amp for each (one is the master and 3 others just match it's current to keep the load spread evenly between the 4 big T0-247 transistors),  but I would now I would likely use the latest linear rated high voltage power Mosfets instead. (They did not exist 12 years ago.)  Regulating the PV on the low side (below the 0v battery connection, with the +PV tied directly to battery +120VDC) keeps my maximum DC voltage to earth less than 148 V; which better than 3x safer than 120VAC.   I would seriously consider high side regulation today, with a maximum of 220VDC, since so many server farms are now running 350 VDC.  Having been zapped by 120VDC many times over the last dozen years, I also have a better appreciation for relative DC safety; it hurts a whole lot less...more like a static shock. For the same RMS voltage, it takes 4x the current to kill you with DC.

I will have to consider my options for increasing the power handling capacity of my series regulator as I add more PV power for my daytime inverter operations. I can just add additional modules in parallel with minor mods or revise the design.  Either way I'll have to add a battery charge current limit since my new PV arrays will be able to exceed my battery charge rate. 

I am amazed that wet lead batteries are STILL best bang for the buck in 2017.  I viewed my original development  as something interim until the new battery technology breakthrough arrived.  A also thought AGM batteries with their higher charge rate and efficiency would have completely eliminated wet lead long ago- but they have not, and their cost remains too high to justify for my system, though it was designed for them, with 10 individual battery shunt regulators. Because of the individual analog battery shunt regulators, I only do mini-equalizations for 3 hours every 2 weeks, and only have to add water every two years. (I do check them annually.) So treating wet lead batteries as if they were AGMs does have advantages.
 
My night time power consumption in winter is about 1.5 KWH.  Lighting and computer/projector use are my night loads. 
My daytime loads include computer plus low wattage electric cooking (300w rice cooker, crock pot, immersion heater, 500W hot plate), but only on sunny days (the norm here).  My refrigerator/freezer is propane which dramatically reduces the load on my batteries (and thus my ongoing battery replacement cost of $220/yr) and I do enjoy the soundless operation.  The "waste" heat does heat the separate gas kitchen in the winter, as does the "waste" heat of my incandescent bulbs for lighting in winter.

My 6/1 CS provides the big loads- AC for pumping water to my 2000 gallon tank (gravity feed), washing machine, and compressed air for my all my woodshop tools.  This runs about $15- $25 a month of diesel depending on what I'm doing in the shop.  My new inverter should be able to take over most of this, as it can run a 2 hp compressor to keep the 500 gallon tank topped up, so the CS would only be used when maximum air is needed (sanders, ripping on table saw, and my air string trimmer for the yard around the house). 






AdeV

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Re: Blasphemy..... Solar power.
« Reply #140 on: October 24, 2017, 09:12:57 PM »
... The calculator shows that to raise 250L of water (as is the size of my service) 30oC I will need about 9 Kwh of power. To raise it 20oC will need about 6...

Just a thought, as this thread is already as far off topic for an engine forum as it's ever likely to be  :o have you considered water solar panels for water (pre-)heating? Rather than convert the sun to electrickery (at ~25% efficiency at best), then convert it back to heat in an urn or other water heater - why not just run the water through a bunch of copper pipe inside of a wooden box (IIRC you paint the inside black) with a glass lid. As with solar PV, you still get heat even on cloudy days (but not at night as with Starfire's system!). Even if the water only picks up 5-10 degrees on its way through the system, that's 5-10 degrees you don't need to find electricity for...

Biggest issue, as I understand it, with direct-to-heat solar panels is boiling them (or "saturating" them as I believe it's called - presumably because something somewhere bursts under the pressure and saturates everything around it ;D), which can be avoided either by dumping the water out of the system before it boils, or having a large heat-sink which can cope with shedding the heat generated in the solar loop. Another problem, which would certainly affect much of the USA and the UK (and Europe) is, of course, freezing - but standard auto anti-freeze can be used if the water circulates through a heat exchanger rather than heating drinking/bathing/etc. water directly.
Cheers!
Ade.
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1x Lister CS Start-o-Matic (complete, runs)
0x Lister JP4 :( - Sold to go in a canal boat.

BruceM

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Re: Blasphemy..... Solar power.
« Reply #141 on: October 24, 2017, 10:11:25 PM »
The cost of PV has gotten so low, while copper/ plumbing costs remain so high that many people are going Glort's route and just using PV with their electric resistive water heaters. Especially when bargain used PV panels and DIY setup can be done.  Purchased solar water hot water panels have not seen the volume and price reductions of PV.

The picture changes when there is a bigger hot water need that can be met, climate-wise, with 85% efficiency direct solar water heating.

I built my own hot water heating flat panels and my own EPDM lined 800 gallon insulated storage tank (mostly below grade to allow for a simple, low cost single tank drain back system), and my own copper heat exchanger in the tank for domestic HW.  Heating is direct from the tank to avoid the cost/complexity of another heat exchanger.  This handles my home heating plus domestic HW all year round.  I never use cold water for laundry, now. This made sense because of being able to do my superinsulated radiant floor home heating.  I felt the extra expense and my labor were well invested now, while I was still able to do much of the labor myself, to improve my financial situation post post age 65.

Carlb has posted pictures before of his nice solar hot water setup for just domestic HW, with both DIY flat panel and reflector collectors.  The solar wand heat exchanger made by Bulter systems makes for a simple add on to an existing electric or gas hot water heater.  I am now a fan of the 1/16 inch polycarbonate for glazing- the 4x8 foot sheets can be rolled for cheap shipping, and it will tolerate stagnation temperatures.  There's no question that PV to electric heating is much simpler to plumb, and has no leaks. :)







starfire

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Re: Blasphemy..... Solar power.
« Reply #142 on: October 24, 2017, 10:56:55 PM »
BruceM, thanks for your comments....the phantom current from commercially built controllers is way too high for what I need. PV panels, like a hydro setup are  insidious in that power is available over time, even a few amps over a 24 hour period amounts to a lot of juice. Same goes for phantom drain, it adds up rapidly.
Digital Mppt controllers by design can never quite settle on a peak, will always be slightly above or below depending on the algorithm used , and theres quite a few active parts in the design, whereas the thing Im playing with uses a LM311 low power comparator driving a BJT switching stage, all less than a 4mA current draw. Because its already oscillating in use, the boost section can be nothing more than an inductor/diode on the series pass transistor, and  can be a largely passive design also.
I too use bipolar.... its not often realised the turn on resistance of a BJT can be even lower than a Mosfet, despite the intrinsic  voltage drop across it is  higher. They are also far more robust.
Im just messing with solar to see what is possible, all info I have seen concentrates more on peak outputs in bright sun.... here we have many many more overcast days over time.
Flooded wet acid still rule..... over the decades have tried many types. Gell cells died very quickly, gas pockets depriving the plates of electrolyte, either through localised gassing or heat.  A very large NiCad bank developed strange and random problems after just a few years of use. The most interesting was some genuine 110 year old Edison NiFe batteries I picked up from an abandoned coal mine.
These I simply filled with a caustic soda solution, all guesswork, and they appeared totake a charge no problems. Not very friendly to use for powering electronic s though. To charge at even a low rate saw the voltage increase from a nominal 12 volt bank to 17/18 volts, and a reasonable load saw 10 volts across the same bank, indicating high internal resistance. Have since found out this is normal... similar cells are made in China today.

BruceM

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Re: Blasphemy..... Solar power.
« Reply #143 on: October 24, 2017, 11:16:34 PM »
Looking forward to reading about your work on the small system, low-light charge controller as it progresses, Starfire. 

Take a look at the newer MOSFETs with a full SOA specification for linear operation.  Fairchild and IXYS both make some beauties, as do others.  While a bit spendy, they  can be very useful when you want low voltage drop when in full on mode than you can achieve with bipolars.  I use one for my linear 12V PV charge controller design.  Something like an LM10 for control (100 uA)...

But then I'm an analog fiend, and you're likely going to end up with a pure switch type design.




starfire

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Re: Blasphemy..... Solar power.
« Reply #144 on: October 25, 2017, 12:46:41 AM »
Many years ago, , worked on a small farm. The living quarters had no power, and it took hours to heat the water via the wetback., a real pain after a days hard work.
 A 100 meter coil of 3/4 ubiquitous black  alkathene pipe thrown on the roof would net a 44 gallon oil drum of near boiling water on even a medium sunny day thermo syphoned into  the drum on the peak. The good thing with hot water, it contains little oxygen, therefore steel drums dont rust, instead growing a protective layer of heat tolerant scum and slime.
Dont overthink this stuff.

starfire

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Re: Blasphemy..... Solar power.
« Reply #145 on: October 25, 2017, 01:22:52 AM »
Lead acid  funnily enough are almost 100 percent recyclable, the cases, the acid, and the lead, even though the greenies would have you believe they are an environmental hazard. They are worth too much as scrap to end up in a landfill, unlike  zinc carbon and Nicad/Lithium etc that largely do pollute, ending up in the waste basket.
Lead is reused, over and over. where the more esoteric types require rare earths that are in limited supply. Lead acids are big and inelegant, but no problem in stationary off grid situations.  Despite being  the most studied and understood of all battery technologies. they seem to defy any attempt at "improving" them.
The "Y2K" lot of lighthouse batteries I bought in year 2000, I doubled my money  17 years later in scrap value. Looking from a financial prospective, they supplied 17 years free storage, and then gave a healthy profit.... I hope my new  220ah crown batteries do similarly..
Little known byproduct in old used batteries..... dueterium, ie, heavy water.
This stuff is used as a moderator to slow nuetrons in nuclear reactors, and is the fuel  for hydrogen bombs.
. Its produced over time when water is continually electrolysed  into oxygen and hydrogen...  as in batteries...rather like an enrichment centrifuge....
Now, where did I put that block of uranium??? Need a deterrent in case the mericans take an interest.....
« Last Edit: October 25, 2017, 01:57:40 AM by starfire »

32 coupe

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Re: Blasphemy..... Solar power.
« Reply #146 on: October 25, 2017, 01:56:41 AM »

Check "virgin lead" batterys.
Expensive, but they are the ticket.

Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

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BruceM

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Re: Blasphemy..... Solar power.
« Reply #147 on: October 25, 2017, 02:08:39 AM »
I couldn't find a meaningful technical report showing that virgin batteries performance are enough better to offset the doubled price.  How about a link, 32 coupe?


starfire

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Re: Blasphemy..... Solar power.
« Reply #148 on: October 25, 2017, 02:21:35 AM »
Me too. One site reckons 400 cycles at 80 percent DOD, thats  only a little better than a top quality thick plate standard type.
Has anyone had experience with these?

https://www.hiteksolar.co.nz/blogs/news/106430214-why-should-i-consider-using-lead-carbon-batteries
« Last Edit: October 25, 2017, 02:30:21 AM by starfire »

32 coupe

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Re: Blasphemy..... Solar power.
« Reply #149 on: October 25, 2017, 02:45:24 AM »
I don't remember the sites.
I did a lot of research a few years ago.
As some of you know I work on large private
yachts and deal with batterys up to an including
4d and 8d size.
Battetys today won't last for more than 2 to 3 years.
I haven't had a car battery last for more than 3 years
here. I don't buy cheap batterys. The jell cell batterys
don't seem much better. I am in Florida and heat kills them.

All batterys today are made with recycled lead and from what
I understand it is the impurities that causes the early death.

Batterys used to last years, as many as 10. Not today.

The virgin lead batterys are used in commercial critical backup
systems. They are made in the USA by 1 or 2 companies.

Expensive, heavy.

I have a few in the field but it's too soon for me to give an
honest assessment yet, but time wil tell.


« Last Edit: October 25, 2017, 02:57:49 AM by 32 coupe »
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"