Is there such a thing as too much solar

[Ian poyntz]

Hi All:

For 3 years I was watching my power consumption in my off the grid house as I only had 6 panels partly shaded by trees. Then I put up an 18 panel 4.5kw array and now by 11am each day the inverters (3 - 3kw. outback inverters) drop the array because the batteries (24 x 2volt KS-25 Surrette wet cell) are 100% charged at 52 volts after reaching 59 volts for 3 hours of absorption. My question is: is there such a thing as too much solar? Do batteries like to be always at 95 -100% charge? I can also equalize to 63.2volts now with no problem. Cell temperature seldom goes over 30 degrees centigrade.

[Ralph Day]

Hi Ian
Are they truly at 100%? Have you checked with a good hydrometer? If they're really 100% SOC that's great, time to look for opportunity loads:nuts: I have a water distiller, an oil filled electric heater and a mini split heatpump/ac. But not nearly the pv you do.

I've been considering adding more pv for more ac and heat dump loads, but not this year.

|Ralph

[Rob Beckers]

Ian, keeping the batteries charged just about every day, and shallow cycling is not a bad thing for lead-acid batteries. You'll get more cycles (and therefore years) out of them. There's a limit to that too though; ultimately the acid corrodes the plates, so even when cycled very little a lead-acid battery has a finite life span.

The real question though is what happens in winter. Most off-grid people have power coming out of their ears in summer. It's mid-winter when energy is scarce and batteries get cycled deeply.

I second Ralph's note that you don't really know if your batteries are fully charged until the specific gravity confirms it. Battery Voltage says very little when those batteries are being charged or discharged. If you don't have a hydrometer yet, take a look at the HydroVolt from Compasselect. It's cheap, really easy to use, and really accurate (well, we sell them, which would make me biased, though I truly believe they are great bang for the buck).

-RoB-

[Chris Olson]

Real deep-cycle batteries do not like to be charged every day. They don't live their lives on the solar cycle like people do. Charging them every day only elevates their internal temperature, continually cycles them on the most inefficient part of their charge curve, and causes excessive positive grid erosion.

There is nothing wrong with having excess installed solar capacity. Ralph has the best idea and that's exactly what we do here. I use a Morningstar RD-1 to progressively add load to our power system as system DC voltage tries to climb to Absorb V. This sends the PV power to the loads (electric water heating) and specifically prevents the batteries from being charged every day. I have our system set up to run a discharge/charge cycle every 5-10 days, which limits the number of cycles on the batteries to 50-70/year. In the winter the cycles can sometimes run as long as two weeks. In the summer, if we don't use enough hot water, they can end up being charged every day. But I got a logging system and three battery monitors to manage it to prevent the every day charging if at all possible.

I could show you how our system works, and I even got videos that I've made that explains all the details. But what we do and have might not apply to other off-grid folks because it would probably require a huge investment in replacing some of your propane-fired equipment with electric. But opportunity loading does work to better manage your batteries.

[Krista Hiles]

Definitely over charging should not be done. Excess of anything is bad, but it won’t be similar in winters.

[Rob Beckers]

This isn't about overcharging: Charge controllers ensure that batteries get charged correctly...

-RoB-

[JF Nantel]

We have lived off-grid since 2000. We have a 48 volt bank of 4KS-25PS. I am interested in what Chris is saying about limiting the absorb cycle on a daily basis. Would you tell me at what stage of charge (or discharge) you are keeping your battery bank at, before letting them charge, all the way up?

[Chris Olson]

Hey, nice to meet another off-gridder!

Our target recharge level is 50% DoD and we can usually achieve that on 3-5 days in summer, and 7-10 days in winter. However, we will go to 70% DoD (very close to LBCO with any real load on the inverter) if conditions warrant it. The bad part about anything below 50% DoD discharge level is that it is impossible to fully recharge in one day.

We heat 100% of our water with electric, and that takes a LOT of power (as much electricity consumed just for water heating that most off-grid folks consume for all their other loads combined). So having a high-use opportunity load works really well to both maximize harvest and to manage the batteries.

I have used many different controls to accomplish it, and continue to "tweak" it to make it more accurate and fully automatic. The latest incarnation (actually in service now for over a year without any changes) uses a Morningstar RD-1 Relay Driver to turn on increasing water heating load in progressive stages as battery voltage tries to climb to Absorb V. The result is that the batteries "float charge" for several days at a time during the day, then continue discharging at night.

An example of how this works - we start out with the batteries at 100% SOC on a particular afternoon. We wake up the next morning and they have dropped to 90-91% SOC. Voltage starts to climb when the sun comes up and when it hits 52V the RD-1 turns on 500 watts of water heating load. It will maintain that 500 watts as long as the system voltage stays above 51V.

The sun continues to get higher in the sky and the voltage continues to climb to 58V. At 58V the RD-1 activates channel 2 and operates a series parallel SquareD contactor that switches that water heating load from 120V (on a 240V 2,000 watt element) to 240V split-phase. This increases the water heating load on the system to 2,000 watts. It will maintain the 2000 watt load as long as voltage stays above 52V and then revert back to 500 watt load.

If voltage tries to climb to 60V (Absorb V is 62.0V) channel 3 on the RD-1 turns on an additional 1,000 watts of water heating load (240V 4,500 watt element operated on 120V single phase). That additional 1,000 watts of load (heating water at 3,000 watts total laod) will remain active as long as voltage stays above 56V. If voltage actually hits Absorb V (62.0V) the RD-1's channel 4 shuts down the wind turbines and reduces the amount of power input to the system. The wind turbines will remain shut down until the voltage falls to 60V where they start up again.

Our loads and hot water use pattern is such that, on average, once a week we get two really nice days in a row. The water heaters get totally caught up and their thermostats shut off the elements. Now there is no water heating load and the system charges up the batteries.

In winter time we manage how fast the batteries discharge over a long period of many days by using diesel prime genset power for a few hours a day, and peak load genset power (two generators, one of which is auto-start on peak load standy power). The generator management system is even more complicated than the water heating system. But basically, the generators are used to directly power loads at times when they can be run at 80% rated load or better (best fuel/kWh efficiency) to reduce load on the RE system and slow the battery discharge rate. The charger in our XW inverter is disabled so the generators can never use it to charge batteries. The only time we will enable the charger in the inverter is when we plan on being gone for a long time so the auto-start genset can recover the batteries in the event that is needed.

The reason I do this is because the losses using a generator to charge batteries are too great. Using two different sized gensets to directly power loads (with the use of Generator Support in the inverter) is quite efficient (relatively speaking when considering generators) and yields much higher usable kWh/gallon of fuel burned.

We have gone 2-3 weeks without charging our batteries in the winter, but it was almost a disaster because our system could not generate enough power to fully de-sulfate them again and still power our other normal loads. So these days if our TriMetric says it's been 10 days since a full recharge, I'll let it go a couple more days. But if the weather doesn't improve I shut off the breakers to the water heaters and let the system catch up and sacrifice a little water heating for that day. We have dual 50 gallon water heaters and we can store enough hot water at 165deg F to go 5 days without heating any water if we have to. So I use that "reserve" if it is needed to get a battery charge done if it has gone too long.

[Chris Olson]

JF Nantel -

I'll add a bit more on this, because even though I've been attempting to make it fully automatic for quite some time, it still requires manual intervention sometimes. The TriMetric is my primary tool for managing the batteries and as of today we are at 4.75 days since charged and the batteries are charging at 33A on an absolutely beautiful sunny summer day here:

https://lh6.googleusercontent.com/lpuFUL_hS39xjyfDyj3ymLF8y2Md_r1Ig-PjC184mfs=w640-h480

https://lh5.googleusercontent.com/-fmzLTrW9HQk/U6Rz0_a80MI/AAAAAAAAIOM/65NkpabnFMo/w640-h480-no/100_4319.JPG

What has happened on our current cycle is that we had several days of solid overcast and rainy conditions. Our batteries were dead on 50% SOC this morning and we used up all our hot water we had stored last night. The top element in primary water heater has power to it all the time, controlled by its thermostat set at 125F. So we never actually run out of hot water because that element heats about 20 gallons or so if it drops below 125F. That happened last night when I took a shower and that 2,000 watt top element came on, running on battery power.

When this happens in winter - out of reserve hot water and batteries 50% or below, this is when we will be running the little prime diesel generator. The generator will go to heating water and carrying some of the other loads. The inverter and RE system will carry some of the loads beyond what the generator can't power, and let the RE system use the balance to try to catch the batteries up more.

In the summer when we get more nice days we don't run the prime generator. But with the batteries at 50% and out of hot water it'll take two nice days just to heat 100 gallons of water back up, plus power our loads, plus put enough in the batteries to make it thru the nights. And it will then take two more nice days to finish charging the batteries. So we're probably looking at a 9-10 day cycle on our current one, assuming it stays sunny and nice for the next four days.

This is quite unusual for summer here, but it does happen. And the batteries run nice and cool when it does. Our utility room is not heated in winter, but well insulated. Our battery bank is in insulated wooden cases and is kept at about 22C in the winter by a duct fan that blows heated air from our basement into the battery case. In summer that duct fan blows the nice cool air from the basement into the case and keeps the batteries at 22-25C. When they finally get to absorb they will rise to about 29-30C by the time they get fully charged, then it takes a couple days to cool them back off to 22-25C.

[JF Nantel]

Thanks for this explanation Chris,

When you stall your batteries at 52v (around float), and keep them there for as long as possible (summer time), are you doing this to spare battery bank cycles for prolonged battery life?

I understand what you are doing with the transfer of energy into hot water and also with the fuel/kw efficiency of the gensets, but I would like to stay on the battery bank (I will call it) "stalling" for now.

Aside from, maybe battery bank life span, any other reasons for the "stalling"?

Was Steve Higgins or littérature from Surrette a confirming party into your equation?

Aside of course, the plain fact that the battery manufacturer advertises; "longest battery life with minimal discharge while keeping the temps. on the coolest rather than the highest side?

[Chris Olson]

When you stall your batteries at 52v (around float), and keep them there for as long as possible (summer time), are you doing this to spare battery bank cycles for prolonged battery life?

That is correct. You can "float charge a battery" and actually get it to 100% SOC assuming it has not gone thru a long cycle where the lead sulfate is harder to put back into solution in the electrolyte. My whole system is designed to cycle the batteries (target) 50-70 times per year.

It was all designed with direct input from Steve. He said we should be able to go 30 days without an issue between recharges. But I found that does not work. We simply do not have enough RE installed capacity here to do it. Steve bases that on using an industrial grid-powered charger to charge the batteries on a 24 hour charge after they have gone 30 days without a full charge. We all know that is virtually impossible to do with an RE system, even with wind turbines, because the wind turbines don't put out steady enough power to charge batteries - only power loads and prevent discharging them.

The theory is that you can discharge a battery at the 100 hour rate and that takes a little over 4 days on a 100hr discharge before charging again. Well, we can't do an exact 100hr discharge rate because our loads jump all over the place. So what happens is that the battery discharges at the 20 hour rate or better for a time, then discharging is halted and it is charged at about C/40-C/50 for several hours, then goes back to discharging again at the 20hr rate during the evenings. So after several days of this, the average discharge rate is a little slower than the 100hr rate. The battery ends up cycling anywhere from 50-85% SOC for several days, gradually getting lower and lower, or sometimes maintaining a 60-75% SOC level for a couple days. Then it gets charged back up.

The tool that tells you whether or not all your lead sulfate went back into solution after absorb is done is the hydrometer. You cannot get normal fully charged SG if you still have some sulfate left on the grids. If you find your SG is low, you have to bump your Absorb V. And that is why we use 2.58VPC for absorbing. That's what it took to get 1.255-1.265 SG's on these partial state of charge cycles.

[JF Nantel]

Thank you for this Chris,

It is encouraging to see a thread that pursues reason while dealing with real life off-griding.

If you don't mind, could I know what your total battery bank capacity is? This would put a picture over your method, in other words it will complete my understanding of the way you operate.

Regards,

[Chris Olson]

At the 20hr rate our batteries are 820ah, at the 100hr rate they are 1156ah. We have the CS plate jars in 12V containers. Yours are the KS plate jars in 4V containers. I'm not sure what the difference is between the CS and KS jars, but I think ours are .260" positive and .180" negative with 25 plates and the KS jar are .275" positive and .180" negative with 21 plates.

I wish I would've gotten ours in the 6V or 4V containers because each of ours weighs about 585 lbs each. It's not too big of a deal to pop the top off the container and pull the jars out to move them. But me and a friend man-handled them with prybars and pieces of pipe on the floor to roll them into the utility room when we put them in, and they've never been moved since.

[JF Nantel]

Thanks for this info. Chris,

The Ks plates are a little thicker, but a like all the electrical power that you are running in and out of your batteries.

Its nice that RE systems can allow us to do all kinds of things. Conventions are good for a baseline but when you completely rely on yourself to sustains your electrical needs, then, baselines are meant to be transgressed.

[Chris Olson]

I guess I made some videos to show folks some of this. This one is for the water system, and I made one change after this video was taken - I added an additional 1,000 watts on channel 3, and move the turbine shut down to channel 4

http://youtu.be/YC7OLA7G0bE

And then I did a series of three videos showing how we use generators to manage loads, and manage battery discharge under varying conditions. This first one is an introduction to inverters with Generator Support and how it is used:

http://youtu.be/3nWOQNGl3MU

And this is one explaining Gen Support on prime power:

http://youtu.be/WH41IRQ1n2g

And the final video in the series on conserving battery energy

http://youtu.be/AxdOnJaino4

[JF Nantel]

Hello again Chris,

Would you be willing to share what your total yearly fuel consumption is for your two gensets, in volume, not money?

It would be interesting to know as well the total yearly hours of run time for both gensets?

Lastly, how many hours do you figure these gensets have in them, before they have to be replaced?

I am trying to tie all the strings to figure out overall system output/efficiency when everything in the household is electricaly driven (save the heating of course). I am looking at it as if the off-grid living was full time/year round/two adults.

A price per kw/hr is not really what I am looking at since the price of various fuels can vary quite a bit depending upon where you are on the planet, hence the individual questions for fuel volume, yearly hours and gensets life expectency.

Regards,

[Chris Olson]

We have a logging system and it tracks energy output and hours from the generators but not fuel burn. But since the load is precisely controlled by the inverter whenever a genset runs and I have measured fuel consumption to determine most efficient load range, I can calculate it and come out within probably +/- 2% of actual.

Our energy consumption in our home last year was 7,863 kWh, or average of 21.5 kWh/day. The prime genset logged 1,307.1 kWh last year and run time of 691.5 hours. The peak load genset logged 555.9 kWh and run time of 152.2 hours.

The prime genset burns 0.17 gal/hr at 1.92 kVA load. Actual load on the genset was slightly below that, and that may introduce some error. Calculated fuel burn was 117 gallons.

The peaking generator burns 0.58 gal/hr at 3.60 kVA load. Average load on that one was pretty close, so calculated fuel burn was 88 gallons.

Total energy produced by the gensets was 1,863 kWh, total fuel burn was 205 gallons, yield is 9 kWh/gallon of fuel. Current fuel price is $3.64/gallon, so today's energy cost from the gensets is 40.4 cents/kWh. The prime generator is considerably more efficient than the peaking generator and power from it costs 33 cents/kWh. Power from the peaking generator costs 58 cents/kWh.

Since the gensets only run when RE conditions are poor, or when the inverter can't handle the continuous loads, the cost in solar/wind or additional inverter/batteries is astronomical compared to the $750 in fuel we burn every year in generators.

Our energy logging system is a Schneider Electric Conext ComBox. The data it gathers is invaluable in making decisions on how to tune your system. Our logged data shows that from Dec 1 to Feb 15, to power our home without using a generator would require approximately 47 kW of installed solar capacity and we would need 4.7x the battery capacity we have currently, plus one additional inverter. That equates to about $60,000 additional cost in solar, $40,000 additional cost in batteries, and $4,000 in another inverter. I can buy fuel for the generators, at today's prices, for over 100 years at today's cost of RE equipment to cover those extremely poor RE months.

Our gensets have Honda GX engines, and they are proven 7,000 hour units in the power equipment rental business. We also have a Robin diesel generator for prime power, and we use that in the summer to run our central A/C in July and August. Its operating cost is very similar to the small Honda EP2500CX gas unit.

[JF Nantel]

Thanks for this Chris,

My interest is mostly trying to discern what works exceedingly well in a system versus another.

I can see that you noted the alternate scenario if you decided to pull the gensets and add panels. I guess, for me, what it boils down to is how one decides he's going to make it work.

Obviously, you have your reasons for powering your home the way you do, but I believe we (off-grid ones) are all somewhat bound, to a certain extent, to using a certain amount of fuel (diesel or gas), no matter what.

I've even looked into fuel cells and as it stands, right now, there is no option to go completely without some fuel, that is enough to make a system reasonably viable.


That is why I believe it exceedingly important to try and maximize and try to improve/perfect what we have.

Regards,

[Chris Olson]

For us, going off-grid was never about "going green" or "saving the planet" or anything. It is because of location and the fact that utility power does not come here. We've been here for 14 years as of June 8. After about the first 7-8 years we got tired of scrimping on every watt and "conserving". So I set out to build a system that is economical to operate long term, with all the conveniences of having utility power.

The only concession we have to make today is that I cannot do any welding in the shop if my wife is running both the range oven and clothes dryer at the same time. But that is very rare.

We had a LPG generator at first, but that thing would not start or stay running in the winter and the price of LPG is ridiculous in these parts - $5/gallon for a fuel that only has 2/3's the energy in it of diesel fuel. One of our off-grid neighbors has a LP fridge and is looking to get rid of it and get an electric one because it is costing them $75/month for propane for their fridge. That's just one example of why, back when I started designing, I looked for a way to build a 100% electric off-grid power system.

The days when we have to run a genset to power our electric lifestyle means that we are indeed burning diesel fuel or gasoline instead of propane. But it's pretty efficient the way I have it set up. And as of today, we are burning less dollars per month in our generators than our neighbor is in JUST his fridge - and our energy consumption in our home is about 22 kWh/day average and theirs is about 6-7 kWh/day. That is because our system goes against all "convention" in designing an off-grid power system, while theirs is the "traditional" design with using propane for cooking, water heating, et al, with a generator charging batteries when they go dead, and using electricity for only the basics.

If you never think outside the box no progress is ever made.

[JF Nantel]

Thanks for your response Chris,

I really appreciate it.

For my wife and I, it never had anything to do either about going green or saving the planet. We went of grid because the only land we could get to our liking was off-grid.

That was in Yukon, what a place to start and try making decisions about a system. At first we lived almost like hippies, like you said, trying to earn every watt. I remember my wife on a sewing machine, listning to some tunes on the cd player out of a cabin connected to a few second hand Trojan batteries and a car sized inverter. Almost unbelievable when we look back at that.

Won't tell you the whole story right now, quite long and dearley emotional!

Long and the short of it, about four set-ups later, and a move back closer to my birth place, this present off-grid move was simply on account of the Provincial power company just skinning people alive and its plans to double their prices in the next couple of years. Additionally, when I did try to deal with them when I was building, since they have a monoploly, they were not very accommodating.

It ended-up costing much more than connecting to the grid, but like you said we too wanted to be comfortable. And I am so glad that you are up front with your details, it really makes me feel like we are not alone fighting and living for what we believe in.

I just think its great to have a forum like this and share!

Thanks again

[Chris Olson]

You know, I don't know how many times I've read on internet forums that the "procedure" for going off-grid is to first get your loads down to the bare minimum, learn to conserve, use propane for everything in sight except maybe a few light bulbs and the well pump.

Looking back on our early start, which pretty much parallel's yours, the people that came up with the above "recommendations" have either:
1.) absolutely zero experience with off-grid living
2.) forgotten that most people who want to make the move to off-grid are usually fairly well-off financially and can actually afford it

We have several off-grid friends in Ontario, north of Minnesota and Wisconsin, that have also been living off-grid for more than 10 years. And all of their systems also parallel ours. One observation we can make is that of folks who follow the "traditional recommendations", very few have made it more than 5-7 years full-time off-grid living. It gets too tedious. Every off-grid couple I have met that has made it more than 10 years has taken the initiative to re-design their system, no matter what the cost, to live a more normal lifestyle. And the driving factor in every one of those was not the man of the house - it was the woman. Us guys might be able to live in a two-room shack with a single light bulb that doesn't work unless you tap on it, and be happier than a pig wallowin in mud. But the woman of the house becomes more demanding with time and wants something better.

[JF Nantel]

My wife was born and raised in Toronto, lately the off-grid topic came up and she said, “it doesn’t make any sense to me to develop a property to the point that were one really likes it and not have all the electricity one really needs”. And I agree with her completely, we wouldn’t want to feel like we are camping at home.

As well, once one is reasonably set up, it is very nice to not get a bill from the power company. Since we are sheltered in a maple grove of very tall trees, it is quite cool here even throughout the summer; nevertheless, in the very near future I am planning on getting AC to accurately regulate the humidity level inside the house.

Our Radian has an AGS “load start” feature among many others, so it is quite easy to manage “heavier loads” when need be.

Our dishwasher heats the water up to 140 degrees F + and depending on the cycle it can go for up to three hours, most of it with a draw of 15 Aac. With our system, no problem, if I don’t want to draw from the bank, the diesel genset will fire up and even charge the bank at the same time if it needs it.

I love diesel gensets, ours has an electronic governor, very steady, as well, these engines consume fuel proportionately to their load. The greatest bonus of running one in the garage (with a residential grade muffler) is that it really does a good job making it nice and toasty in there during the coldest time of the year, we have a loft and a gym and plants, etc… there. An automatic exhaust fan with louvers also prevents the temp. from getting to warm. There is a propane heater in the garage but it is set at 15 degrees C and this type of fuel is usually reasonable around here but if the cost reaches the price of off road diesel, then we get a double bang for our buck if we run the genset…the garage heats up nice and our battery bank gets charged by the same token, now that’s nice (for pennies) specially on those short, overcast, cold winter days. If that’s not efficiency, I don’t know what is. There are two CO detectors in there and they have never come on and never will.

Lately, there was talk about maybe moving again…one of the first things my wife said was “are we going to have at least a generator”, there was a sense of urgency to it! Even born and raised in the big city she would feel deprived without a genset and there is nothing wrong with that, I thought wow! Lastly for the genset, if all else failed, we would stay very comfortable with only that for as long as we fed it fuel.

And that’s just the beginning of our setup, we like it cause it has treated us to comfort. Many times, my wife would come home from work cause there was no power there, “brownouts” she’d say. At home she’d hit the automatic garage door opener, drive into a warm garage, get in the house, make herself a coffee and then did whatever she wanted to. I guess you really have to live it to “dig” it.

There have been challenges, mostly for me, but it has been a good learning experience.

[Chris Olson]

That's pretty cool, and it's amazing how well our two systems sort of parallel each other.

We got one large pole shed here that is not insulated or heated - we keep our 5th wheel RV in there in the winter, as well as trucks, tractors, and some other machinery.

I have a large shop that is insulated and heated - powered and heated by a Cummins 4BT 50kW diesel co-gen set. I have a smaller shop that is insulated and heated, and powered off our inverter with an underground service buried to it. I do most of my work in the smaller shop in the summer. But when I need to work on something big like a truck in the winter, I fire up the co-gen to warm it up in there. It usually takes 12 hours or so to get the low pressure water system up to 180 degrees, and we have a transfer switch in the power room that I can switch the house and small shop over to the co-gen when it's running so we got virtually unlimited power (full 200A split-phase service) in the house. The co-gen feeds the AC1 (grid) input on our inverter, and we have a separate transfer switch on the 240V panel so the loads from that do not have to go thru the inverter when the co-gen is going.

Then we have the three smaller generators for the house and small shop - two of those are gasoline, one is diesel. We put in central A/C in the house last year - a 1.5 ton Trane high-efficiency 22 SEER unit. Our RE system runs it fine during the day. At night, if it is hot and humid, we start our small diesel at sundown and run it all night to keep the A/C going, with the diesel powering the AC2 input on the inverter. The diesel is a little Robin RGD 3300 and it can power the A/C fine, but requires the generator support from the inverter to handle surge load for compressor starting and other normal loads in the house. So it still uses some battery power when we are running the A/C on genset power.

We heat the small shop with a diesel-fired space heater. And I also have a solar hot air panel on the south wall of that shop that works fairly good in the winter when the sun gets down on the horizon and the solar collector gets reflected light off the snow into it. We use the waste heat from the gasoline gensets to heat the generator room in the winter. They are air-cooled engines and require about 70 degree ambient temp so the engines run at the proper cylinder head temperature.

I make another video last year when we decided to go from the diesel prime to gasoline because the diesel is too hard to get started in the winter time, and some explanation on how the prime power system works:

http://youtu.be/QG_9PwXXvKo

Like your wife, we wouldn't be without generators. They are probably THE most important thing in our entire system - not the solar panels, inverter, etc.. A lightening strike can take out the entire RE system, and we can still bring everything back online on genset power. I always joke that I have more ways to route power around this place than Con Edison has. I can flip transfer switches and power the loads from any genset in the system without so much as even getting a screwdriver out of the tool box, completely removing the inverter and DC system from the picture. This allows for full shutdown and servicing of the DC system without ever losing power for even 1 millisecond.

You only find this level of redundancy in off-grid systems that are experienced and have been around for awhile. The vast majority of RE installers do NOT know how to set up an off-grid power system. They set it up according the book and then the first thing that happens is that you have an inverter failure and have to swap out an inverter in the dark because the only way the genset was wired was to the inverter's AC input. And they make the huge mistake of only installing one generator. I know of NOBODY that has lived off-grid for more than 5 years that has only one genset.

Again, nice to meet somebody else that knows what off-grid power, and what it takes long term, is all about.

[Chris Olson]

Just to provide a real-life example of how we manage our system - a couple days ago I mentioned that I figured we'd be running a 9-10 day cycle on our batteries this time around. Well, that's not going to work. The weather is not going to cooperate.

We had a beautiful day here today. It takes 81,000 BTU to get both our heaters from the top in the primary being at 125F to both of them up to 165F. Electric water heating is almost 100% efficient and that takes 24 kWh input to the heaters to accomplish it. The system ran the water heaters at 500W as the sun came up, then 2,000W for awhile, then full 3,000W load for 5.6 hours and caught the heaters up in one day. In the mean time it got the batteries up to 84%. They're down to 82% at 11:30 at night here and we're pulling 13 and a half amps from them @ 49.8 volts.

https://lh4.googleusercontent.com/ALxIrUUEBbq7--wt--DRSR3MkjOGoQew4nDe_Hp1oGA=w640-h480

https://lh4.googleusercontent.com/-MlywNyOCT_4/U6ZgKui-nlI/AAAAAAAAIOs/yBKeOn_0JB4/w640-h480-no/100_4321.JPG

I looked at the weather forecast and we're going to have good sun until noon, then cloud over and rain and overcast until Wednesday night with 90% chance of rain. We're at 7 days right now and this is going to put it over 10 days on the current cycle because it'll take all morning tomorrow to make absorb.

We got one of them blender valves on the water heaters that only lets 125deg water out to the faucets. That is necessary to prevent being accidentally burned by the 165F water in the heaters. So when the water is at 165 we don't use very much. But we used some hot water tonight to take showers, so there's reheating of water that'll happen in the morning first before the batteries get charged.

By morning we'll be at 78% and we need 200ah to charge up the batteries tomorrow, or about 11-12 kWh JUST for battery charging to get to 100%. That ain't going to happen with our other normal loads on because we'll use 12 kWh from midnight to noon just for loads. We can produce 12 kWh in the morning from solar if it's sunny like they say it will be. There won't be anything from wind because that's forecast to be calm until Sunday night when it's supposed to pick up a bit from the NE.

So I just made the decision, after reviewing what the system is telling me, that I'm going to start the little prime genset in the morning at sunup and run it for 12 kWh @ 1.9 kW load. That will offset what we use from now until noon for loads, and let the RE system get those batteries charged up before we head into several more days of overcast weather.

I hope other off-grid folks can see that this is taking a proactive approach to managing your power system. Fix the problem before it becomes a problem, instead of running the batteries down and then using a generator to charge them - which is fixing the problem after the fact. There is a huge difference in efficiency between the two management methods. My method will use 1.2 gallons of fuel and we'll be good for at least 5 days of poor weather without running a genset again. If you do it the other way and wait until Monday or Tuesday when the batteries get down to 50% and then run a big 6-8 kVA genset to recharge them, you'll burn at LEAST 3.5 gallons of fuel to accomplish the same thing.

Having the proper equipment to monitor your system and make these decisions is critical. I've heard some people downplay detailed logging of all your system performance parameters as being "useless". But I'd say these people that claim that don't have a clue. I look at our load history for the past 21 days, and pull up how much we use from midnight to noon over that period, and it only takes me 30 seconds to realize that we ain't gonna make it without injecting 12 kWh into the system in the morning with a generator. Without that data at your fingertips, and equipment to collect it, you are flying "seat of the pants" - no different than if you were charging batteries and you THINK they're charged but you don't have a hydrometer to actually measure it and know for sure.

[JF Nantel]

I always preferred the shorter charging cycles myself, especially if they are done with a genset. I’ve always felt that I wanted to be “on top of it” since in the past I’ve had to (no choice) bring the batteries up from deeper DOD, when something unforeseen happens.

When we were in Yukon, because of wintertime, very short daylight hours, you quickly learn that maximizing whatever you need to charge up your bank is mostly everything but solar array. I believe this type of thinking is a key factor that opens up the mind to taking the true meaning of power (electricity) economy to its limits.

One may have all the technology in the world, and even the fuel for that matter, but the fact remains that the “solar world” starts taking a more realistic meaning, functionalbility wise, if one has to assess the operation off a RE (solar or other) installation in a constricting factual/real life position. What I mean to say is, it is very difficult and almost impossible (for most people) to start having deep reflections and compute system validity from a theoretical stand point and validate those thoughts before having been faced with it in a real life situation.

Under very (or even extremely) lean solar (sun) availability, most systems in our neighbouring area, up North, had very limited solar arrays and with reason. I remember contemplating “even if we had a football field sized solar array” that still wouldn’t work and if you bumped it up (in size) anymore, it might end up working in the end but it would be extremely inefficient.

Now one may say, yes but you were North of the sixtieth parallel and we are way further South so here things are different. Unfortunately, if one thinks like that, the point has been missed. What I am driving at is opening the mind to assessing “solar” into an integral efficiency concept.

Didn’t really want to use that example, but I have no choice: Solar farms, in Canada or the Northern USA. Now this has got to be the most inefficient catering of electrical power to the population. Imagine that, in the daytime when the sun shines nicely, warming up everything (people, machinery, buildings…etc.) and by the same token lights up everything within its range, that’s when the “solar farms” start to put out power. Now when the sun goes down and most leave work and go home and it gets dark and cold, the “solar farms” stop putting out power and that’s when people really need it the most. In the evenings, families are using power, through the nose, bumping up the furnaces, cooking supper, doing laundry…and the solar farms…dead! Now in my book, that’s the summum of inefficiency. On top of that, the power companies come up will all kinds of impossible schemes trying to influence people to tell them when they should do a load of laundry or something else.

Now what I have just described is money driven, therefore extremely biased and it contradicts opening the mind to RE efficiency. To back up that claim, I don’t know about USA but in Ontario, most “solar farming” are fuelled (paid for) through a provincial “program” where the investors are paid a guaranteed return, on contract, for their investment, at a higher rate than what the kw/h sells for to the public. So guess who has to pick up the difference.

Now I just had to say that because, basically, if we want to assess true “solar efficiency” we can’t rely on the models that are permeating society. And to respond to the title and first question of this thread; “Absolutely, yes there definitely is such a thing as too much solar”. Sloughing off power from a large array, or any size of array, is certainly “not an efficient way” (at least not the most efficient way) of managing RE.

In my mind, the perfect scenario for “solar power” is when it is used on satellites/space station, etc. (perfect sun to panel efficiency, no clouds, ever, super clear, they probably even get something from the moon as well). Or in an off-grid system where the temperature stays above freezing, year round.

I am not saying that “solar power” or being grid-tied is not good. What I am saying is that if I want to be absolutely honest an objective about “solar power” I first have to acknowledge the “total system efficiency factor” and in order to do that, I must firstly start off with an unbiased and totalitarian outlook.

Our property here is somewhat conventional with an average house size and a garage with a loft. In Yukon, the house and garage had a slightly smaller footprint but the environmental elements were harsher so, all in all, our situation is somewhat similar, major difference being, more winter time daylight here. I guess a good benchmark to gauge our “solar system efficiency” is our uninterrupted home comforts versus our yearly “cash” outlay (including initial system investment). I am extremely satisfied with our numbers. Last winter was considered very cold (on record) and the house here has got a lot of glass (one person once said “you need a little bit more wall”), that means we have to sacrifice heating costs to enjoy the lovely views of the forest. In other words, last winter the furnace was “on” a lot and the genset fuel consumption was excellent. To top it all off our solar array is (would be considered) very small. I will add a little bit more later this year for AC purposes but it will still end up being a very small array if compared to what gets installed in most system nowadays.

Last thing for now is fossil fuel consumption vs. clean solar energy. Our total RE system utilises less fuel, on a yearly basis, than an SUV driving around town for two months out of a year (got nothing against SUVs!). Our genset burns so clean; we never get crankcase fumes and never smell exhaust fumes outside the garage if the engine is running. Burning a few logs in the fireplace (high efficiency) and relaxing just watching the flames is actually burning fossil fuels, but it is an awsomely nice thing to do.

[Chris Olson]

I don’t know about USA but in Ontario, most “solar farming” are fuelled (paid for) through a provincial “program” where the investors are paid a guaranteed return, on contract, for their investment, at a higher rate than what the kw/h sells for to the public. So guess who has to pick up the difference.

You've seen those 10kW FiT installations in Ontario? The last time we visited some of our off-grid friends up NW of Thunder Bay we took a drive and looked at two of those. We talked to the owners of them and one was considering abandoning it. He had taken out a loan to put it in, and even with the subsidy from Hydro he couldn't make the payments on it. He said from March to September it barely breaks even, and from October to February it is costing him money out of his pocket because the loan payments are more than it produces.

Both of the ones we looked at were on big single-axis circular tracker outfits that had gear motors driving this big table with the solar panels mounted on it, and little micro-inverters mounted behind the panels.

[JF Nantel]

Hi Chris,

I should have been more explicit about the contracts. What is garanteed is the rate of return for each kw/hr produced.

[Chris Olson]

Yes, that's what the owners of those said. One guy claimed it was breaking even. The other guy claimed he was losing money on it. It looked like they put in a separate meter to measure how much the solar array produced and fed back. And then these folks had yet another meter that measured how much their houses used.

Evidently, for the one guy at least, somebody didn't do the calculations right on what the return was. Or over-estimated the amount of solar insolation that was available on that site. I know most of our off-grid friends up there have 6 kW solar arrays to power their systems that typically consume 8 kWh/day. And they all used to run their generators every single day in the winter. I built a 3.75m wind turbine for one of them and the wind turbine reduced his generator run time to about 1/3 of what it was before. The word got around and I ended up building 11 wind turbines for those off-grid folks up there around MacDowell Lake.

[JF Nantel]

We are nowhere near that size of array and we’ll pull off the AC demand no problem after we had a few more panels. Daily generator running is one thing, daily generator runtime is something else. In Yukon, with very cold weather, -30 C solid for six weeks (happened once), all we needed was about 1.5 liters of fuel per day and our batteries never really went below 35% DOD.

I have started to reduce the absorb time to a minimum on our battery bank. What I am doing is observing the state of charge of the bank (taking SGs) while trying to make the top-up charge cycles “shallower”. I am presently not equipped to “stall” the battery bank voltage completely at around 53 volts. By I can live with that for now.

Since “Surrette/Rolls” agrees that SGs at 1.265 once a week is fine, and that this will even prevent the need for a rigorous monthly equalizing, I guess I am not loosing battery life by trying to verify how this will pan out.

The only thing I do not like about this now, is the fact that the controller has to slough off some solar RE for some part of the day. Fortunately, since we have a smaller array I don’t feel too bad about it.

I do somehow suspect that since the battery manufacturer suggests less DOD, on each cycle, for longer life, that less lengthy top offs at a higher temp. (58.8v for hours, usually bumps the bank temp. by a few degrees every time) could spare battery life, just as much.

If we’d be in the winter time, this process would be much easier to achieve, given our system setup. But the Rebulk voltage setup, on the Midnite controller, offers me latitude to adjust the setting, for as long/many times as I want until I am satisfied with what I see.

Thanks to the info from this forum, it truly helps.

[Chris Olson]

I have started to reduce the absorb time to a minimum on our battery bank. What I am doing is observing the state of charge of the bank (taking SGs) while trying to make the top-up charge cycles “shallower”. I am presently not equipped to “stall” the battery bank voltage completely at around 53 volts. By I can live with that for now.

I don't know if I'd shorted the absorb time unless the SG's indicate it is OK to do so. Our system does not use an absorb timer, but rather uses accurately measured net amps to the battery to determine end of absorb. Our absorbs can vary anywhere from an hour and a half on a shallow cycle with several days of good weather in a row to taking two days on a deeper longer cycle because there's not enough hours of sunlight in one day to get it done.

That absorb stage, and making sure it is done correctly, is very, very important on a system where you regularly use PSOC cycling.

[JF Nantel]

When I talk about a "shallow" (my word) charge cycle, I mean I let the voltage climb to the absorb set point on the controller 58.7v. and then just let it bring itself to float as soon as it hits END AMPS set point.

I used to let it run longer with a lower setting for END AMPS.

I’ve just checked the SGs and they are really nice, with the bank just floating at 52.7 and at 23 degrees C.

There are at least two functions that I use on our 250 M Classic, for the absorb cycle span; a MIN.and a MAX. for TIME and the END AMPS for current resistance.

I have asked Steve Higgins at “Surrettes” about all those parameters so that I have a solid referenced baseline to guide myself from.

END AMPS prevents an over extension of the absorb cycle. TIME is usually set according to a manufacturer formula, to make sure the batteries get a good full charge in the case where they could be somewhat sulphated and reaching END AMPS setting too quickly.

There should be no problems when dealing with it with a reasonably good charge controller and a good refractometer/hydrometer. It’s very straightforward, no in betweens for error.

Anyways, like I said, for two days now, shortening the absorb cycle has not yielded any negative signs. Of course, I will closely monitor this for at least two weeks to a month and make up my mind about this afterwards.

[Ralph Day]

Hi Chris
I know if the folks who were breaking even in the summer built the array in the shade or what. On a sunny day in the summer we'll harvest over 80kwhrs...at $0.80 per kwhr gives $more than enough to pay for the system. True, the gloomy winter months are tough, but still, unless they paid $150K for their installation I don't see how they can't make money. Our yearly income from the microfit is between 12 and 14K per year, depending on the weather.

Simpler is better in my opinion. Stationary racking as opposed to trackers (less to go wrong), change the angle monthly for best results. When ours was installed for about $80K in 2010 the tracker units were going for about $100K, but their output betters ours by a bit...probably 8 - 10% over the year. Not making money makes no sense.

There's a meter just for revenue, no loads on what you produce, unlike net metering. In fact, we couldn't put our house system on net metering because there's a 10kw limit per connection point. Silly, but that's the OPA rules.

I did get my wind turbine working again. The production welds failed on the rotor head, they were mickey mouse done, and I mean mickey mouse. The local machinist fabricator and I repaired things, we replaced the thrust bearings and put it up for another 5 years, I hope.

Always like reading about your control systems Chris. I try to emulate somewhat, but using utility power to sneak amphours in the bank overnight (just let the SW4048 float level charge), or even leave to float if it's cloudy with no wind at all. That's quite often the case. In the summer I just let things cycle, there's enough hours of quality sun during the week.

Ralph

[Chris Olson]

The guy that said he's losing money on it is by Kakabeka Falls. It's overcast there more days than it is sunny because of the largest body of fresh water on earth - Lake Superior. We got the same problem here - if a low pressure area with counterclockwise rotation goes over that lake we only get peeks at the sun now and then for many days. North of the lake in Thunder Bay it is known as the "sunniest spot in Ontario" because they don't get the cooling effect of low pressure winds off the lake. But that huge inland sea affects a pretty large area - thousands of square miles.

We haven't been to Canada yet this year - we are doing the Lake Superior Circle Tour on our motorcycles in 2-3 weeks. The ice just went off Superior a couple weeks ago and the water won't get above 35-36F surface temp all summer this year. The fog over the lake is severe because of the cold water. That lakes holds something like 10% of all the fresh water on earth, is over 1,000 feet deep, and the surface temp never does get much over 40F. Some scientist figured out once that it contains enough water to flood all of North and South America to a depth of one foot.

Whoever did the calcs on that FiT system didn't do it right. They used some calculator that shows solar insolation by latitude or whatever instead of actually measuring it. Just the point that solar installers got a lot to learn and you can't install solar panels at any location and make them work any more than you can wind turbines.

[Ralph Day]

Ah, the dreaded Lake Superior micro-climate.

It's strange that we're here stuck down in Lake Ontario (Prince Edward County) and we have some of the best insolation in the province. There are dozens of microFITs and over 100 megawatts of solar farms, mostly in the eastern half of the County. Of course, that has to do with the amount of "scrub" land that the big installations can cover and take out of farm production. You can grow very little on 2 inches of lousy topsoil laid over limestone.


Ralph

[JF Nantel]

Geographic location should always be considered in its totality when assessing “total system efficiency”. Seems to me like insolation is, more often then not, the only factor considered when assessing system efficiency. Actually, when I say that, I am still talking mostly from my general area’s standpoint, meaning anything relatively close to the 48th parallel going upwards.

As well, one should include demographics. Otherwise, the basis, for developing an efficient system, is flawed.

What I mean is, it doesn’t matter if Spain/Portugal or India would decide to go ahead with more solar panels, it certainly doesn’t validate that their needs (electrical) will be met with the same efficiency as ours would if we had a system similar to theirs.

What about Iceland? Why don’t they have tons of solar farms? It’s simple, most reasoned countries/areas adapt to what is more efficiently feasible “where they are” (at least, I hope). If you have a geyser that you can harvest from, for heating and maybe some electrical applications, then that ends up translating into RE efficiency. It is constant and has more than one application and waste is negligible. Especially if it gets cold there (somewhat like here save their added temperance on account of the ocean and the nearby jet stream effect).

If one has travelled elsewhere in the world, one would have to realize the differences between the electrical needs according to geographic location. The Caribbeans, Central Europe, Southern Europe, Asia…etc, all have different needs. In the Philippines or the Caribbeans, most of the cooking is not done over an electric range like in Ontario. Same thing with water heating. Work hours in the day are different; some places shift the work day to accommodate temperature. The working classes are different in different areas and the needs (electrical) vary according to that too.

It shouldn’t be any different here in Ontario, but somehow it seems to be. I guess Ontario, being probably the richest (for now) province in Canada, figures it can make and spend money just about as much as it wants. This is, in my mind, a hindering/stumbling block to “total energy system efficiency” thinking.

What I am driving at is that around here, consideration to the geographical “Latitude” and the lifestyles/demographics factors is/has been neglected/usurped by overwhelming financial interests at the expense of “total energy system efficiency” concept.

It seems like, around here, we want what we want, when we want it and it doesn’t really matter if what’s good for the goose is not necessarily good for the gander but its just gonna have to be!

Unfortunately, here, it appears to be an accepted concept and fact that it is inevitable and therefore almost completely acceptable (OK) that a single off-grid home’s solar array should/would slough-off/shed hundreds or even thousands of kw/hrs per year. The irony of it all is that the “geographical” location factor is used to justify the wasted kw/hrs instead of being used to re-assess the efficiency of the systems.

[Chris Olson]

Ah, the dreaded Lake Superior micro-climate.

It's strange that we're here stuck down in Lake Ontario (Prince Edward County) and we have some of the best insolation in the province.

So-called "micro-climates" affect just about every place on earth. Some are suitable for solar installations. Some aren't. And that's why you'll see solar "farms" in the desert southwest, but you won't see them put up in big numbers them on the eastern seaboard where the climate is affected by the Gulf Stream, even though it's at the same latitude.

[Chris Olson]

If one has travelled elsewhere in the world, one would have to realize the differences between the electrical needs according to geographic location. The Caribbeans is, in my mind, a hindering/stumbling block to “total energy system efficiency” thinking.


Interesting - we were anchored off the island of San Andres in the SW Caribbean last winter for two weeks. It's a small island, very popular tourist destination. 100% of the power on the island is diesel generators.

The reason solar panels aren't used? San Andres is in the hurricane belt. The solar panels don't withstand the hurricanes.

[John Nelly]

Hi,

Solar power is free to collect however its bounty is impossible to control. No matter how many batteries or inverters you use to store the power, you would only be harnessing a fraction of it perhaps to let it escape or go as waste due to limitations in storage capacity.

However technology has provided an answer for this in the form of solar power controller switch aka solar power diversion manager. This device diverts surplus power from the solar panels to applications such as heating water in an immersion tank or appliances like washing machine and even to charge or store in batteries. Came across this post in FB - https://www.facebook.com/groups/SaveTheWorldGetOffTheGrid/ about a device called solarimmersion - SolarImmersion - The efficient solar PV water heating system - YouTube that can do this.

[Chris Olson]

There's all sorts of "green energy" products and ideas these days. But in reality everything on this planet runs on solar. Including your car running on gasoline or diesel fuel. Plants stored solar energy millions of years ago and the biomass turned into crude oil. It is one of the most sustainable sources of energy yet discovered. Plants are way more efficient at converting sunlight to energy, and storing it, than solar panels and batteries are. And new technology has revealed that the reserves of this stored solar energy in plants is far greater than ever imagined.

The entire planet runs on a carbon cycle powered by the sun and plants. Humans will never be able to invent anything that beats it for efficiency. The real problem is that humans have over-populated the planet, and mother nature will eventually take care of that problem too.

[Mike Mianrazi]

You are definitively right on that. energy never goes to "waste" it only goes from one form to another. That doesn't mean we shouldn't conserve energy tho. The less energy we use the less carbon foot print we leave behind.

------------------------------------------------------------------------------------------------------
www.mrheatmechanical.com