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darryl
01-22-2016, 09:05 PM
Last night I put together one of my panel assemblies. I used 6 panels- each being 8-3/8 wide I figured to stay within about 4 or 5 feet in length for ease of build and use, etc. It became 50 odd inches in length and about 11 inches wide- a reasonable size.

Today just for fun I wired the panels in series and did a voltage check. We don't have sun here today, and it's quite dark for mid afternoon, but I was getting over a hundred volts from it. While thinking about this whole 'powering something' thing, I started wondering about actually using it in a high voltage mode. Keep in mind this is academic, and I have no unrealistic expectations of getting useful amounts of power out of it- aside from the original use which will be as a 'top-up' source in my vehicle, and all panels wired in parallel for this, with nothing more than a voltage cutout circuit to control overcharging.

So back to this high voltage idea- a person could make up a simple circuit to detect voltage, then switch a series transistor on at the high voltage point, then off at the low voltage point. The high point would be the panel voltage at the peak power point (times the number of panels) and the low point would be something less than that, perhaps about 2 volts less per panel. The array would charge a capacitor, and the output through the series transistor would feed through an inductor to a battery bank. The switching of the transistor would have some hysterisis so the switching action is sharp. The charging action would then be done in pulses, which suits batteries fine. The battery bank determines the voltage on one side of the inductor, and the two switched voltage points would keep the panels working in a small range where the maximum power point is.

Offhand, this doesn't seem much different than any MPPT controller, except that the input voltage is much higher than the output voltage, and the switching losses would be less. Virtually every circuit I've seen uses a panel voltage that's only about 30% higher than the battery bank voltage- typical from what I've seen is a panel voltage at MPP of about 18 volts, with the battery bank at 14.4 or so- my large panel is rated at 17.6 v or so at maximum power, and my latest panels are rated at 18.8 volts. You've basically got about 4 volts of difference, and a loss of 1 volt in switching represents a 25% loss. Why not lose that 1 volt from an excess voltage of perhaps 100 volts, for only a 1% loss. That's the basic idea anyway.

I see that one spec for solar panels is maximum system voltage. One spec said 200, another said 600 volts. I'm sure that just reflects the breakdown potential at any point where electricity could jump a gap or destroy a reverse-biased cell, something like that. But it does suggest the possibility of using a higher system voltage, like 120 vdc for instance. Your battery bank could be 10 12v batteries in series, with conversion for powering appliances being a directly switched output without an inverter.

As I said before, this is academic at this point and just for discussion. Basically a discussion regarding using panels wired in series rather than parallel, both for low voltage battery bank or high voltage battery bank.

Paul Alciatore
01-22-2016, 09:30 PM

J Tiers
01-22-2016, 09:44 PM
Almost every serious MPPT controller I am aware of uses at least up to 120V or even more. See Outback solar, etc.

It is an absolutely standard way of operating, and allows optimum power output. Utility systems use a voltage up to 600V, possibly more, although the UL recognitions for panels and connectors, etc only go to 600V.

Most of them do MPPT, to get all the power available.

This one uses a max array voltage of 145VDC. A friend of mine has one of these, as I recall. (He might actually use a Xantrex product, but the specs are about the same). His system currently is at about 125 VDC in good sun and a cool day.

darryl
01-22-2016, 11:32 PM
Well that shows how little I knew about 'real' solar power systems. Glad that what I was talking about actually makes some sense-

Largest system that I've seen is a bank of 12 2 volt cells from a railway switchyard. His panels are 36 volt, but all in parallel. The controller has everything though, from what I saw. While I was there it was displaying input voltage, charge current, and battery voltage. I thought the numbers were impressive- charge current at the time was over 30 amps, 37 I think it was.

I'll keep tinkering, and learning.

J Tiers
01-22-2016, 11:37 PM
My take on it is that you are a pretty sharp character, (which we already knew) and that you have a good sense of practical engineering (which we probably also knew).

Nothing wrong with finding that your good idea is in production, it proves that you can come up with good ideas.

PStechPaul
01-23-2016, 12:36 AM
One problem with wiring so many panels in series, is that if any one is shaded or otherwise putting out less current than the others, it may limit the total amount of power that can be extracted. AFAIK, MPPT controllers are most efficiently implemented on a one-per-panel basis, and the outputs are matched so that they can be connected in parallel with a fixed voltage or charging current for storage batteries. It should be possible to use a switching type battery charger that works similar to what you describe. In most cases, it would probably be a buck current/voltage switching supply with the output lower than the input. You can use most any line-operated switching supply on 120-370 VDC corresponding to 85-264 VAC. If you connect panels in parallel, you should use a low Vf Schottky rectifier rated higher than the maximum panel voltage.

J Tiers
01-23-2016, 01:05 AM
If a panel is out of commission, it simply gets bypassed. It's possible to bypass each panel with a parallel diode. When the panel is producing, the diode is reverse-biased. If a panel is not producing, then the current simply goes through the parallel diode as a lower-voltage path than the forward voltage of a series of cells.

When a panel is bad, you lose about the same amount of power, one panel worth, as in the parallel case, but you generally have a lower loss in the "ON" voltaqe and forward voltage of devices and diodes under all conditions. Overall it should be lower loss.

You also lose less in the panel system wiring, due to the considerably lower current, and you require only one switching device for a number of panels. Plus, you get to choose your battery voltage, which can be anything less than the panel string produces.

dp
01-23-2016, 03:47 AM
Series wired PV cells have a problem when the total voltage exceeds the forward breakdown voltage of a single cell. This can happen with smaller cells that lose light as when a bird or large leaf blocks it. Because they have a very large area, series arrays are vulnerable to shadows from any source shutting down the entire array. I'd be interested in what ever purpose somebody might have for doing this. Inverters do the same thing without introducing shading problems.

Our Blues Band did a show at a remote venue last summer on what is called the Solar Stage. It has an array about 2 meters on a side, a box of batteries, and an inverter to drive our amplifiers. Epic fail - the batteries were unable to maintain adequate power for our band, stage lights. We're in a desert with very long summer days being just at the Canadian border but we have thunder storms and heavy rain all weekend. I guess that is why solar is considered unreliable. The solar is also augmented with a wind turbine but had no impact on the reliability. Even the luggable 2KW portable generator didn't help. The other stage had a large fossil fuel generator and they didn't miss a beat. Fortunately our band played that stage too so the day wasn't a complete bust. None of us were happy about having our very expensive gear investment exposed to that lashup.

So the lesson is size it appropriately and keep a battery charger handy that uses grid power if reliability is at all important.

J Tiers
01-23-2016, 10:36 AM
Solar is NOT "considered unreliable". It is FAR more reliable than wind power.

Every panel is a series connection of cells, as many as 30 or more, depending on the panel voltage. So a series array is simply more of the same.

NO.... A bird or large leaf does NOT "shut down" the array. Or the panel. All that happens is a reduction in power output. My own array continues to put out power at the times of day that it is as much as 20% in shadow. Reduced power, of course, the shadowed parts are not producing as much as the others.

EVERY large installation is made with series panels. Your objections are simply unfounded hearsay that is proven to be silly by installations all over the globe. Including mine, and the one my friend has. He has no grid power at all, and has been living there with solar for many years, finding it quite reliable.

Edit: I have no idea what you mean about "inverters". They are for making AC from DC, and nothing to do with solar panels other than using their output.

As for the "solar stage fail"......

From your description, the array was simply an abysmally poor design. For reasonable power, it should have been more like 2 or 3 meters by 10 meters.

At your estimation of 4 square meters, it hat a raw arriving power of about 6kw maximum. The efficiency of about 12% would lead to a net output of about 700 watts. Not enough to keep up with a band.

You do not say what the inverter power was, nor the battery capacity, but my suspicion is it was similarly stupidly small.

The system was not adequate for the usage, THAT is why it did not work. Apparently your usage was too large even for the 2KW genset, let alone the silly 700 watt array.

My friend has had a yearly 2 day music fest for the last 12 years at his place, all solar powered. He has never had a power failure, but his array is about 3 x larger than what you describe, and there are not full bands with PA, its a folk fest.

mayfieldtm
01-23-2016, 01:25 PM
I'm reading that your measuring the total voltage of the series strung panels.
The high voltages are cool but what about current?
Voltage times Amps equals Wattage which is what we really need to know to get usable work out of a system.

I'm really missing something about your ideas on using a parallel diode for bypass.
If a Panel is producing power, it's parallel diode will short it out.
If you turn the diode around, it does nothing.
Upon some more reflection, I think you need to add a series diode with the panel and then bridge those with an additional diode.
Do the panels themselves act as diodes and block reverse current flow? In which case the parallel diode may work after all.

Tom M.

Rosco-P
01-23-2016, 02:13 PM
Even the luggable 2KW portable generator didn't help.

If anything like the Honda EU2000is, it doesn't produce anything close to 2000 watts continuous either.

darryl
01-23-2016, 05:02 PM
The parallel diode allows one panel to be non-productive while others still produce. The diode bypasses the weak panel, allowing current to still flow from the others. Imagine that you have a series of water valves and one closes- no current will flow. In the solar array the diode blocks current flow when the panel is producing, so it doesn't short out the panel, but when the panel is not producing it will be 'reverse biased'- in other words the other panels will impress a voltage on the weak or dead one, in a reverse direction. The diode passes the current in this direction, thus completing the circuit so current from the producing panels can still flow.

darryl
01-23-2016, 05:28 PM
I just did a test. I hooked up a power supply to one of my panels, then varied the voltage up to the limit, which with this power supply is 21.5 volts. With the panel in room light, it's showing about 5 volts output. As I raised the voltage level to it, the 'leakage' current was zero up to about 19 volts or so, then rose to about 30 ma at 21.5 volts. When I hooked it up in reverse, the leakage current never rose above a few ma, if it was there at all. It's hard to read this low of a current on my power supplies scale, so it may have been zero or maybe a few ma. There is no reverse diode on the panel- otherwise the current would have assumed a very high value even with less than one volt applied. What I did not test, and what could be an issue, is a higher applied reverse voltage. This could happen with a series connected array- but then I would assume that any 'better quality' array would have the reverse diode installed, and probably a forward diode as well per string, where more than one string would be connected in parallel. A consideration here would be when using a forward diode you'd want to use one with a low forward voltage drop- this is usually a shottky diode, which may not have a very high reverse voltage rating. You would consider this when putting several panels in series for a higher voltage output. Of course as you series the panels and get higher voltage output, the forward voltage drop of the series diode becomes less important and you would probably use a regular silicon diode, which can have a reverse rating of 1000 volts or more.

In any event, my current panels will be wired in parallel, since they will be used to maintain 12v batteries. I will probably not use either a reverse diode or a forward diode, since the voltage is not high enough to damage a cell in reverse bias, nor damage a weak parallelled cell.

dp
01-24-2016, 12:46 AM
Solar is NOT "considered unreliable". It is FAR more reliable than wind power.

Solar is unreliable. There is no question about it. Solar cells quit working every day requiring transfer to battery backup. Solar cells have to power the inverter(s), battery charger, and the primary load while the sun is shining. The people who built the system are bad at math. That is obvious. That is why I said you have to size the system appropriately.

Solar panels fail miserably, depending on design, when panes are shadowed. There is no question about this. Series panels (where there are no parallel panels) are the worst.

Proper panels are arrays of parallel and series cells that can survive with minimal energy generation loss. Solar as built and installed on an annual basis is at best 50% efficient relative to the placard rating. That is because the sun goes down on average half the time. Seasonally it is far worse. Daily it is worse yet. Anything that quits working once a day is unreliable.

NO.... A bird or large leaf does NOT "shut down" the array. Or the panel. All that happens is a reduction in power output. My own array continues to put out power at the times of day that it is as much as 20% in shadow. Reduced power, of course, the shadowed parts are not producing as much as the others.

Actual field test. It all depends on the array geometry what the degree of output failure will be.

In a series wired array where the total array voltage is greater than the forward voltage rating of a single panel that is shaded, that panel behaves like an open circuit and the entire voltage of the remaining active cells is impressed upon the inactive array. That is bad.

EVERY large installation is made with series panels. Your objections are simply unfounded hearsay that is proven to be silly by installations all over the globe. Including mine, and the one my friend has. He has no grid power at all, and has been living there with solar for many years, finding it quite reliable.

The OP is describing a single high voltage series wired array. Try to follow the conversation were having and not the one you imagine.

Edit: I have no idea what you mean about "inverters". They are for making AC from DC, and nothing to do with solar panels other than using their output.

Inverters are what make solar arrays useful. Solar DC output direct to load are unusual but not impossible. They are what make solar arrays useful as general purpose energy sources. The OP hasn't mentioned them and this part of the conversation is general as applied to solar array in lieu of grid energy.

As for the "solar stage fail"......

From your description, the array was simply an abysmally poor design. For reasonable power, it should have been more like 2 or 3 meters by 10 meters.

I already said in my post that you have to be careful when designing solar power systems to size them correctly. There is more wrong with the solar stage that you and I have discussed. The real problem is they don't have enough money to buy what they need. They do have enough money to buy a proper generator, though.

darryl
01-24-2016, 01:06 AM
I agree there is a lot of misinformation regarding solar systems- perhaps misinformation is not the right word, maybe over-optimism describes it better. I did a mental calculation a couple weeks ago when trying to explain the reality of the situation to a young lad. I came up with 5% of the solar panel rating as an average of the power output. Even that might be optimistic. I guessed at the cost of hydro and came up with a payback period of 16 years- and that's for the price I paid, not what these would be retail. Our cost for hydro is 1/2 of what I used for my calculation, making the payback period 32 years. Talk about sizing the system correctly- it would be virtually impossible to power a stage setup including lights with any system that you could reasonably set up on site. I do applaud the effort to do so, and it probably would have been the highlight of my day to see this being set up and used to power a stage- I've set up enough stage gear and lights in my time for this to have been a unique part of the experience. I've had my share of 'not enough power' when it comes to running everything, and had my own ideas on how to supply enough juice for everything when all that was offered was a 14/3 50 ft long extension cord from a 15 amp outlet- and even for that, how many sq yds of solar panel would it take, even with full sun, to develop even that much (or little) power-

One of the outdoor concerts we powered up had it's own generator on a trailer, probably a 20 kw unit, and it was barely adequate. Makes what I'm doing seem like an expensive alternative to a single AA battery.

J Tiers
01-24-2016, 03:22 AM
Solar is unreliable. There is no question about it. Solar cells quit working every day requiring transfer to battery backup. Solar cells have to power the inverter(s), battery charger, and the primary load while the sun is shining. The people who built the system are bad at math. That is obvious. That is why I said you have to size the system appropriately.

Solar panels fail miserably, depending on design, when panes are shadowed. There is no question about this. Series panels (where there are no parallel panels) are the worst.

Proper panels are arrays of parallel and series cells that can survive with minimal energy generation loss. Solar as built and installed on an annual basis is at best 50% efficient relative to the placard rating. That is because the sun goes down on average half the time. Seasonally it is far worse. Daily it is worse yet. Anything that quits working once a day is unreliable.

Actual field test. It all depends on the array geometry what the degree of output failure will be.

The unreliability is your opinion. Can you cite credible sources? A lot of power companies seem to feel your worries and concerns as expressed are irrelevant. They produce lots of power every day, as do thousands of individual house-top grid tied systems.

If you are concerned about clouds, well, clouds are obviously an issue, obviously they can block much of the sun. Cheaper panels reduce output more from cloud cover than better ones, as I have seen. But they hardly seem to be a matter of such serious unreliability as to cause systems to be scrapped.... One simply accepts that clouds occur, and you get your power as and when it occurs, storing it for use when needed. Only a zero-storage system is truly unreliable in your meaning.

By having more solar arrays distributed over an area, any cloud cover in one place is made up by power from another. And few are so foolish as to put extensive solar arrays in areas which are commonly "socked-in" by clouds.

You may as well condemn solar as unreliable for not producing power overnight..... And in fact, predictably YOU DID...... failing to realize that a known daily outage is not unreliable, but completely reliable.... it WILL be down from a known time to another known time.... RELIABLY. Sensible folks know and plan for that, it does not come as a surprise to them, as it seems it must for you.

AND... I hope you realize what you have actually said in much of the above.....

What you have said, is that a solar cell system, which depends on the light from the sun to generate electricity, will not generate electricity when the sun is blocked from the active surface of the cell system......

That's just about like saying "when water is eliminated from a sponge, that sponge is dry". Was it supposed to be a surprise to us?

Most folks have gotten the memo.... "if you are putting in a solar panel system, do not put it in the shadow, and do provide storage for times when it is not lighted.". If sited sensibly, such as out in a field on the south side of any tall items (northern hemisphere), shadows are no problem.

Then also, the effects shown in the video may be substantially due to the connection and load applied to the panel, and are unlikely to be such an issue with a high voltage system which requires a step-down converter. It would have been much more informative to see the panel output VOLTAGE along with the current. (I didn't have audio with the computer I viewed it on, maybe they explained it all, or not)

These things are no surprise to the rest of us, and can be planned for, accounted for, etc. It's called "engineering", in most places, something apparently not done at the venue you were at... Either a failure by the facility planners, or by your band, which put a demand on the system which it was obviously unable to supply, since a genset of several times the nominal output was equally inadequate.

Poor planning is definitely NOT proof of an inherent failure.

In a series wired array where the total array voltage is greater than the forward voltage rating of a single panel that is shaded, that panel behaves like an open circuit and the entire voltage of the remaining active cells is impressed upon the inactive array. That is bad.

This is, of course, NOT true, and the actual effect has an easy simple, and cheap solution. The panel is not "an open circuit".

The panel behaves as a series array of diode junctions The junctions can reduce the output voltage by the sum of their forward voltages, along with not producing voltage. They can conduct the current, although it is better not to allow them to if you want to avoid extra losses.

A simple parallel diode will conduct the current past the non-productive panel, and the only loss will be a SINGLE forward voltage added to the loss of the active voltage from the panel.

The OP is describing a single high voltage series wired array. Try to follow the conversation were having and not the one you imagine.

That is the sort of system I am talking about.... (large scale systems are simply a number of those paralleled, each one acting like an independent single circuit). My friend who lives off-grid has a single string high voltage system, works great. I have experience with multi-panel single string systems, such as my own, which has several panels in series.....and your contentions are obviously not relevant to any system I have dealt with. Of course, we have the sense not to put up a solar system in the shadows..... that is a crazy thing to do.

As to the inverter deal..... I don't know how the bold section of the first quote relates to the second quote.... Perhaps you can try to explain what "same thing" inverters do without introducing shading problems......The second quote certainly does not explain it....

Series wired PV cells have a problem when the total voltage exceeds the forward breakdown voltage of a single cell. This can happen with smaller cells that lose light as when a bird or large leaf blocks it. Because they have a very large area, series arrays are vulnerable to shadows from any source shutting down the entire array. I'd be interested in what ever purpose somebody might have for doing this. Inverters do the same thing without introducing shading problems.

Inverters are what make solar arrays useful. Solar DC output direct to load are unusual but not impossible. They are what make solar arrays useful as general purpose energy sources. The OP hasn't mentioned them and this part of the conversation is general as applied to solar array in lieu of grid energy.

Of course, shadows do not shut down the array, they reduce output to an extent related to the degree of shading, the voltage reduction, the minimum output voltage required by the load, and other considerations.

If you charge a 12 volt (nominal ) battery with a panel that has a 17 volt loaded output voltage at nominal current.... you have about 2 to 3V headroom. Full charging requires 14.4V or thereabouts. If you cover 3 or 4 cells, the voltage reduces, and the forward voltage, together with reduction in output voltage, bring the volts below the battery charging voltage.

Then the array must reduce output current in order to raise the voltage to a point where a new , lower current flows.

Obviously, if the battery is 12V, or 24V, and the array voltage is nominally 125VDC, a few volts change will make far less change in current. You have 100V or so of available headroom. A small change in current related to the power supplied by the "lost" panel or cell output is all.

You have demonstrated your disdain for most alternative energy in the past, so it's not you to whom this is directed. You will not change your attitude. But others can, and it is to them I give the "engineering response".

dp
01-24-2016, 03:41 AM
The unreliability is your opinion. Can you cite credible sources? A lot of power companies seem to feel your worries and concerns as expressed are irrelevant. They produce lots of power every day, as do thousands of individual house-top grid tied systems.

How much solar energy is being generated in your state right now (11:30 pm, PST)? I can predict the answer is zero watt/hours. Can you name any storage method for electricity that is not a net consumer of electricity? I can think of only one.

Solar quits producing with extreme reliability each and every day. If you had a coal fired plant that did that you would call it unreliable. I am not more charitable for solar. Wind is unreliable too because it's a crap shoot if the wind will blow and other environmental conditions permit the turbines to function.

Can you imagine having to deal with this for the millions of turbines needed to power the grid in the absence of fossil energy? Oh - and because all the solar arrays are buried under the snow and the pumped storage reservoir is dry and the battery backup went off line after 19 hours, the fuel pumps don't work to fuel the helicopters and the de-icing fluid pumps even if there were fueling stations to fuel the snow plows to clear a road for these other infrastructure vehicles to support a wide area blizzard.

https://wattsupwiththat.files.wordpress.com/2016/01/de-icing-wind-turbine.jpg?w=460&h=260&crop=1

Here's the problem: 100% ice up of the UK

wtrueman
01-24-2016, 04:31 AM
Darryl, I have a float cabin on the west side of Bligh island and have used three of your panels (11by48? Out there they are on a very small voltage regulated to keep the system no more than I think 13.8 volts. As long as we are there, we have good power. With today's technology and some of the guys on this forum, you can do well!

darryl
01-24-2016, 04:55 AM
I do not wish to enter a urine shooting contest, but in a sense I'd like to explore the idea of which stream shoots the furthest- in terms of storage and maximum return of stored energy. Yes, this has been covered many times before, but perhaps we can come up with something better than what we have now. There have been schemes postulated and some used in testing and pilot programs- to what practical end I don't know. There has been air pressure pumped into giant salt caverns, water pumped uphill into reservoirs- the usual battery bank systems, heat storing insulated underground ponds, etc. Can anybody think of something that has potential to be better, considering the state of technology these days? What ever happened to flywheels in vacuum bottles, chemical separation and recombination processes, electrolysis of water- I'm missing some for sure. I'm pretty sure we all recognize the need for it.

I think what bugs me most is that solar heat is about the most abundant form of collectible energy, yet storing it requires a massiveness in structure that isn't really practical- and then its use in any form other than heat is problematic. Electricity is about the most versatile in end use, with wintertime heat being quite practical as well. Summertime cooling- well that's pretty much a need as well for a lot of us.

We need a breakthrough in how we're able to control energy.

Rosco-P
01-24-2016, 09:21 AM
We need a breakthrough in how we're able to control energy.

We need a practical and cost effective application of superconductors to our power distribution system. Little or no energy lost to waste heat, greater capacity than an equivalent sized power line in open air. We can generate the power by: fuel oil; natural gas; hydro; geothermal; wind; solar; waves; tides; etc., we just can't get it from where it generated to whee it's needed efficiently

J Tiers
01-24-2016, 10:39 AM
The single factor holding back solar and wind is storage. A real practical and efficient storage means for utility power levels is needed.

It's not hard to do local storage for a few kW of solar array. Battery systems are readily available, of reasonable size, and not prohibitively expensive. It has not been practical to do storage at the megawatt level, or at above. The battéries that are fine for smaller power levels become unwieldy for high levels.

Pumped storage works, and is available for hundreds of megawatts, but cannot be done everywhere, it depends on local geography. It also is relatively inefficient.

The nature of solar is to have known, predictable outages, which are fairly easily planned for in smaller systems. Utility scale photovoltaic solar requires only an effective large scale storage means to make it mainstream.

At present, solar at large power levels is more of a 'peaking plant" since it is available during the highest usage times, but not overnight, without a pumped storage facility.

Wind is far worse. The sun reliably shines every day, but the wind may not blow for days. And wind power generators have some quirks about the power they generate, which disturb the grid if there is too much wind power vs conventional.

A battery (or similar) load leveling system with inverter output would efficiently take care of such issues, but is not available.

Flywheel systems have practical issues. They have been proposed repeatedly, eb
ven demonstrated for lower powers, but high power versions have never been made.

Interestingly, solar thermal (not electric based) air conditioning has been done. It works, and obviously is most available at exactly the time it is most wanted.

Thermal and photovoltaic systems are compatible, and can be combined, at least for lower grade heat. A high temperature solar cell would make them extremely compatible, but hasnot yet been developed.

mayfieldtm
01-24-2016, 02:06 PM
OK
I sat down and drew out the diagram of Panels and Bypass Diodes.
I see now how Bypass Diodes do work!
Apparently, many panels come with the Bypass Diodes already installed.

On the web I've been reading about Mono vs Poly... Mono appears to be more susceptible to spotty shading,
even though it's considered more efficient than Poly.
Why? I'm not sure.

Tom M.

J Tiers
01-24-2016, 03:23 PM
OK
I sat down and drew out the diagram of Panels and Bypass Diodes.
I see now how Bypass Diodes do work!
Apparently, many panels come with the Bypass Diodes already installed.

On the web I've been reading about Mono vs Poly... Mono appears to be more susceptible to spotty shading,
even though it's considered more efficient than Poly.
Why? I'm not sure.

Tom M.

Yep, the diode takes care of it!

One other difference is that the mono seem to lose LESS output in haze or light clouds. The old mono panels dropped to half with overcast, the new poly ones (a northside tree fell on the old ones) appear to lose at least 75% under same condition of overcast.

I don't know why that happens. And it seems opposite to the shading consideration you mentioned.... Dunno.

dp
01-24-2016, 07:44 PM
Yep, the diode takes care of it!

One other difference is that the mono seem to lose LESS output in haze or light clouds. The old mono panels dropped to half with overcast, the new poly ones (a northside tree fell on the old ones) appear to lose at least 75% under same condition of overcast.

I don't know why that happens. And it seems opposite to the shading consideration you mentioned.... Dunno.

Monocrystaline cells have better low light performance than poly, though poly works better in bright light. Not enough to make a difference per square inch, though as the mono cells are overall more efficient per square inch. Per dollar things look better for poly.

I think the effect shade has is equally applicable to mono and poly and is circumvented to the degree possible by using micro-inverters. This drives up the cost and drives down the MTBF of the system. Micro-inverters are also wired in series for the frequency management and AC output, so if there is any water anywhere in the cabling or in an inverter box the entire system can fail. The same problem exists with series connected central inverters, and the very high input voltage (>300 VDC) is an automatic reliability issue. For those installations where other energy sources are unavailable one has to bite several bullets and dig deep to get equivalent reliability and energy/dollar value.

Most failures are related to lightning - the arrays are very large wide band antennas - and lightning damage can require abandonment or full replacement.

PStechPaul
01-24-2016, 08:43 PM
The energy storage can be accomplished by means of elevated mass, where heavy material (rocks, sand, metal, etc.) is transported to higher elevations via efficient electrically driven rail vehicles, and energy is then extracted by the opposite process. Efficiency is supposed to be as high as about 80%, and the method is fairly easily scaled up or down so that they can be utilized in a distributed system with local storage.

Electric cars can provide a great deal of local distributed storage, where they can charge during daylight (working) hours and return some energy for local needs at night. There is often more wind at night and when there is cloud cover so a solar/wind installation can smooth out the otherwise predictably cyclic generation.

There will probably always be some need for fossil fuels, but their use for electrical and mechanical power can be drastically reduced by adhering to energy policies that maximize efficiency and reduce waste. However, as we have seen recently, reduction of demand can cause major disruption to the economy, when so much of it is based on continuous and accelerated consumption. Eventually there may be breakthroughs in battery technology, fuel cells, and even fusion power, that eliminate the present challenges that make some people doubt or ridicule today's attempts to transition from a carbon-based energy paradigm to cleaner, healthier, less damaging, and more sustainable sources. But the most difficult challenge is not the technology, but the dogma of BAU (Business As Usual), as promoted by Big Oil, Big Coal, and Big Gas, and they have no problem spending millions of dollars for propaganda to keep people addicted to their products. Here is a fun video:

J Tiers
01-24-2016, 11:16 PM
There's a certain amount of truth to the thought..... if your car can only go 60 miles before it needs a 10 hour recharge, you ain't gettin far, bud. Nobody will care anymore if all the national parks are sold off....they wouldn't be able to visit them anyway.

The better plan is either solar fuel manufacturing, swappable batteries, or a reloadable battery with a liquid electrolyte and one liquid plate. Drain off and re-fill in 5 min, while the drained stuff is taken to be solar recharged.

The whole 10 hour recharge deal is for the birds.... it needs to be 10 minutes, but that would strain the electric grid if such a fast charge in-car was done.

In fact, the whole idea of recharging IN THE CAR is for the birds. It ties up an expensive car for most of its lifetime, 2 hours drive time, 10 hours charge... who thought THAT was a good idea? Better to charge off-line and swap part or all the battery, IF battery is the way chosen.

Everyone is used to the idea and process of fueling, so make the recharge process resemble that as much as possible. Time-wise, at the very least. Using a fuel which is made by use of solar power is far better, as it gives the advantages without the really STUPID charging process. And it makes use of the already-in-place infrastructure that supports the IC automobile.

Yeah, I know, supposedly "most people" could use the E-car for 80% of their useage..... so then they need a SECOND car for the 20%? Sure... everyone needs a second car for just a few percent of their usage....

Better yet, carefully plan your life so you KNOW that on Thursday a month or two from now between 5 and 9 PM you will need to reserve one of the few rentable fuel type cars..... if it turns out to be available, and not "oh, sorry, the last one went down for maintenance, we rescheduled you for a week from tomorrow".....

Hey.... try making sense for a change.......

PStechPaul
01-25-2016, 12:08 AM
No need to get snarky. EVs, even with present technology, are practical for many people, but not everyone, and not for all purposes. I have two vehicles: a fuel efficient small Saturn (35 mpg avg), for long trips and general transportation, and a 4WD Toyota p'up for when I need to haul large or heavy items, or when I need 4WD. If I still had a daily commute, I would certainly consider an EV, either purchase or DIY. In the future, commercially available EVs will achieve greater range, and fast charging stations or battery swapping and other methods will make long trips more convenient. As I said, there will probably remain some needs that are best met using an ICE and fossil fuels, but EVs should be used for most transportation needs.

Sorry if this doesn't make sense to you. I must have touched a raw nerve.

dp
01-25-2016, 12:28 AM
Sorry if this doesn't make sense to you. I must have touched a raw nerve.

I think the conversation went into the dumper when you introduced information not supported by fact.

But the most difficult challenge is not the technology, but the dogma of BAU (Business As Usual), as promoted by Big Oil, Big Coal, and Big Gas, and they have no problem spending millions of dollars for propaganda to keep people addicted to their products.

People you don't agree with are incapable of rational conversation but only regurgitating dogma implanted in their weak brains by big this or that. That is not only wrong, it is unavoidably insulting. You are regurgitating the dogma of big wind, big solar, big green, and big anarchist and don't see a conflict with your accusation.

You have suggested solutions using technologies that are yet to be invented, don't scale, won't work where elevation opportunities don't exist, exposed yourself as indifferent to the absence of technologies your solutions require, are willing to waste right off the top 20% of generated power to implement your impossible dreams, and to drive up costs of legacy reliable energy by off-lining them to emergency fallback to solve a problem you haven't identified. You are advocating unreliable energy that costs more and is far more complex than common sense accepts. And now you're getting uppity because the people you insulted are snarky.

J Tiers
01-25-2016, 01:09 AM
No snarkiness at all...

That was stone cold sarcasm, my man......

Anyway....

I am not at all sure that "EVs SHOULD be used for most transportation needs".... That's getting a little dictatorial, isn't it? "Should be usable for....." is perhaps a little better.

An IC based vehicle running renewable fuel would be nearly identical in "footprint", but would not require hundreds of billions in all-new physical infrastructure spread across the country. A somewhat more manageable investment in renewable fuel supply would use most of the existing infrastructure and driver skillset, not to mention the existing maintenance facilities, already trained personnel, etc, etc, etc. That represents more hundreds of billions which would have to be spent. (remember, a billion isn't much. It won't buy one new NFL stadium)

The largest problem with the EV at the moment is the way everyone tailors the problem to fit the pre-selected solution. That is clearly irrational.

I don't know that there is any "nerve touched", but there is a big disconnect between capability the reality of needs, and the chance that the needs can actually be filled. Even the chance that everyone can ever actually HAVE an EV.

People have simply not considered the realities of what has been created in society.

We have almost forced people to live in concentrated areas. And virtually every such experiment has been dynamited and re-developed, because it does not work with actual people, only with theoretical people who behave as the planners thought they should.

So, we have spread-out residential areas, often at a considerable distance from their workplaces. And there is no mass transit of a practical nature in many places. I know I could drive in 25 minutes to one former workplace. But to take mass transit, the same trip would have taken almost 3 hours, half of which would have been spent waiting outdoors at -15C in winter. Hel-LOOOOOO!

So.. cars are it, no alternative in a huge number of locations. But the EV that is most available (Nissan Leaf) cannot reliably travel that round trip, it's over the safe distance for many folks. And the range is only improvable with bigger batteries that drastically raise the cost, or with pie-in-the-sky batteries that do not exist yet. So a massive infrastructure of chargers all over the nation is needed.... Which is not going to be paid for.

Neither is everyone going to move house when they get a different job.

These things combine to really limit the usability of the EV in reality, given the current structure of cities. Of course we still hear about the airy promises of chargers in every parking lot, etc, or "studies show EVs suit 80% of trips", or anecdotal statements of "it would work fine for me".... etc, etc.

I am not seeing those chargers, except in a few places, to service the very high cost EVs that "nearly" are practical because they have decent range (they still need a long re-charge time). I am not seeing the folks who say "oh, an EV would work for me", rushing out to BUY one.... so evidently those folks mostly don't think it really WOULD work. So the largest number of folks who think they could use an EV are not willing to really do it.

If even the folks who are in favor of them mostly won't buy them, what does that say?

In reality, in order to use the EV, everyone has to be "taught" to lower their expectations to fit the solution which has been selected. A fairly strong flavor of "If that doesn't fit your needs, then adjust your needs to fit the solution we have selected". How democratic......

Just driving to visit someone who is not on a mass transit line, say 100 miles outside of town, would be pretty much impossible using a "Leaf". A family vacation to Yosemite? Only for the rich, bro, YOU ain't going there. Going to the lake for the weekend? Not possible, no charger out there, and with a 10 hour recharge needed on the way, it's a two day trip to go just one way.

Now, lots of people can afford two present day cars. But given the expense of the few almost practical EVs now, that may simply be beyond many people's resources. ONE EV may be too much.

It makes a LOT more sense to use what we have, to change fuel, but not try to remake the entire personal transport sector, trying to make everyone fit a partial solution that represents a higher cost, but a huge reduction in capability for most people. Why pay a lot more for much less?

Better to pay more and get the same. We already know we will pay more..... it's the "get a lot less" part that bites hard.

nothing wrong with the EV for some uses. The problem is that the "fire, aim, ready" procedure for solving the problems we have by means of the EV will not be accepted without laws to force it (more democracy at work). And right now, such laws are not exactly going to be accepted with open arms... Not in the current political climate.... So nothing will be done.

And why should such laws be accepted? A change of strategy can potentially use much existing energy infrastructure while still operating with renewables, and not forcing a huge disruption on everyone, not to mention the costs we would all be saddled with.

Heck, we don't even have focused real research going into better batteries or battery systems, we are just drifting along into an already-failed plan with no way to make it work. And the proponents, even yourself, admit it does not really work.

if we were serious, we'd have a "manhattan project" type development going to get it in place. that's what is needed. But we do not, and probably will not have such. Possibly that is because most folks realize that we are looking at the wrong solution......

It's not too late to move on renewable fuels, we are not yet irrevocably committed to the failed EV, the charge-a-battery-in-the-car idea.

ironmonger
01-25-2016, 10:51 AM
No need to get snarky. EVs, even with present technology, are practical for many people, but not everyone, and not for all purposes. I have two vehicles: a fuel efficient small Saturn (35 mpg avg), for long trips and general transportation, and a 4WD Toyota p'up for when I need to haul large or heavy items, or when I need 4WD. If I still had a daily commute, I would certainly consider an EV, either purchase or DIY. In the future, commercially available EVs will achieve greater range, and fast charging stations or battery swapping and other methods will make long trips more convenient. As I said, there will probably remain some needs that are best met using an ICE and fossil fuels, but EVs should be used for most transportation needs.

Sorry if this doesn't make sense to you. I must have touched a raw nerve.

A friend of mine has a Tesla, and the only major drawback is the price tag... she has much more disposable income than do I. It is, however, an absolute blast to drive... The other minor drawback is the total lack of nuclear power plants.. Right now the only source of electricity is fossil based. Bet the same folks that are pandering for EV's are likely the ones that killed off the nuke plants...nice job. It takes 85 KWH to completely charge the battery. That's likely around \$340,000 without rebates to install (http://michaelbluejay.com/electricity/solar.html) a sufficient system to charge your Tesla. While it may be cost effective the initial outlay is not something that most people can afford. Want to build an EV? I know a guy with a 25 HP motor...

As far as solar goes, it remains the best solution for off grid locations, but as far as sustainability goes I have yet to see that Don Lancaster’s (http://www.tinaja.com/etsamp1.shtml) criticisms of energy to produce V total output power has been addressed as yet (look for morengf.pdf in the link). The original article was published in 2002, and to date net gain has not been achieved.

Even if you don’t like this article, Don has a wealth of articles that are interesting. He was the guy that wrote the TTL cookbook, which introduced TTL logic to the non engineer.

As far as I am aware there is no producer of photovoltaic panels that is powered by them... That would be testimony to their practicality.

darryl
01-25-2016, 05:46 PM
Don Lancaster has written for Popular Electronics and probably other mags for decades. If you have any interest in electronics it's definitely worth looking up his body of work.

'As far as I am aware there is not producer of photovoltaic panels that is powered by them... That would be testimony to their practicality.' Now there's a statement. Ironic isn't it-

PStechPaul
01-25-2016, 07:20 PM
There was a company in MD, Solarex, that had a manufacturing plant at least partially powered by solar energy, but it closed around 2010 due to inability to compete with China, and the 2008 financial crisis:
http://www.green-energy-news.com/arch/nrgs2010/20100020.html

It was given some financial help by the State of MD in 1994:

I think Don Lancaster's statement was based on conditions in the 1970s, where solar cell production costs were as much as 250 times higher than today. Solar cells also can be recycled to a large extent, saving much of the energy required to make them from raw materials:
https://en.wikipedia.org/wiki/Solar_panel

His article (http://www.tinaja.com/glib/pvlect2.pdf) has been revised over time with the latest copyright 2008, and it shows that costs at that time were rapidly approaching the net gain point.

He is still posting (as of June 2015) on sci.electronics.design:
http://www.tinaja.com/whtnu15.shtml#d06.10.15

J Tiers
01-25-2016, 08:10 PM
Yes.

Most of his information is a lot more true if you are in Maine, than if you are in Arizona, California, etc. Both on the basis of sunlight percentage, and , in California also on the basis of the electric rate. That one is true many other places as well, and investing in solar NOW for a later benefit may be a better plan than he thinks.

Nonetheless, he has a point, albeit one that is getting less true.

darryl
01-31-2016, 01:18 AM
Had a thought regarding those electronic drill battery chargers- since the power supply is rectified ac and gives roughly 160 volts dc, what would stop anyone using solar panels in series from dumping directly into the filter cap in one of these chargers. I wired my first panel in series and had over 155 volts coming out. Granted, under load the voltage would drop to 120 or so- but which the charger may automatically correct for. Output of one that's in my hand right now is 12v, 1.5 amps. That's almost exactly what my panels are rated for.

Hmm. Now I think I want to bench test one of these using a variac. I would guess that the limiting factor as the voltage dropped is heating in the power device from the rise in frequency of operation, and the corresponding increase in the current draw if full power is being delivered to the power supply output. Next thought- it would be good to put to use whatever excess voltage would potentially be stored in the filter cap under high solar influx conditions. This makes use of the energy that might otherwise just be wasted as heat, and does the important job of limiting the input voltage to a safe level. But also perhaps the charger can take a higher input voltage safely-

Now we get to deal with the charger regulator circuit. Most of these will be designed to deal with either a nicad or li/ion. I would be happy to just have it operate continuously, limited to a safe voltage for the battery. There's going to be a pin somewhere that is there to disable the output when full charge is reached. If I can distinguish that point in this charger and disable it, I'll have my test rig.

Something else, while I'm having ideas- you will reach a point where the battery pack is fully up and the sun is out in full force. Shame to not collect on that energy coming in while you can- so here we go. Considering that somewhere along the line it will all go to heat, might as well dump the excess electricity from the panel into a 'heat sink'. It will go in using element wires, and there will be a thermal mass of a certain size in there- with enough high temperature insulation to keep the loss minimal. If your system can use the heat contents overnight, and come back over an average day for use the next night, this heat sink module could perhaps be very reasonably sized.

And that takes me to the simple phrase 'stored sunshine'- if you were going to store energy as heat to begin with, why not then take it directly from the sun. So here we are into focussing or reflecting systems, plus tracking. But the conversion from solar radiation into heat in a capsule is pretty efficient. Just for the next moment let's get carried away and imagine some kind of thermoelectric module which can be used to generate electricity from the heat-

And here I am, wanting get all the energy I can out of some system, in three usable ways- heating, cooling, and electricity. Each kind of stored up separately- not too much to ask for?

Anyway just a few thoughts.

PStechPaul
01-31-2016, 02:58 AM
Maybe you can install a sort of Venetian blind system that can shade the solar cells when they have fully charged the batteries, and instead have a black surface with pipes and hoses to capture the heat and store it in a hot water heater for other uses. A similar process could be accomplished using reflectors to direct the sun's rays to the photocells or the passive solar collectors. A heat pump might be added to extract some of the heat and return cooler water to the collectors, or to cool the cells for greater efficiency.

darryl
01-31-2016, 03:41 AM
At one time I was thinking of installing a wind generator on my house. It wouldn't be big- maybe a 6 ft blade diameter or so. I figured at the time to catch the power down in the basement by running a drive shaft vertically down through the roof- easy enough to do with some types of wind generators. The drive shaft would be sheathed by a larger tube of course, which would be the tower holding the rotating blades or whatever. The key thing here is that the mechanical power is transmitted into the shop, where I station the actual generator et al. The same concept is what I'd like to do with focussed solar- optics bring the light down a shaft which directs it into an absorber of some kind. I'm looking at having the absorber able to work at very high temperatures- perhaps 1000C or more. Just a concept.

darryl
01-31-2016, 03:32 PM
Well I ran one of my drill battery chargers through a test. If I do not plug the battery into the charger first, I'm always able to get the charger to start and work, even with the input voltage down to 70 vac. It will deliver the full charging voltage to the pack, so I'm guessing it will then be delivering the rated current as well.

I tried with the battery plugged into the charger before ac voltage is applied. Then it didn't matter what level of input voltage I gave it- it would give a bad battery indication. No sun again today, otherwise I'd continue the test to see whether the charger would run from the limited current available from the solar panel. Power-wise it should be fine, but nothing beats a real test.