A short history of my system and how well it works.

Les Nagy

As I have mentioned in some other threads, I purchased a full off grid system in the US and had it shipped ahead of me to my new home in Chile. I purchased batteries from a business in Chile.

The system I purchased:
Xantrex XW4548 export inverter
Xantrex XW-MPPT60-150 solar charger
Xantrex XW System Control Panel
Kyocera KD205GX-LP (205 watts) solar panels quantity of 9
Midnite Solar E-Panel MNE250XW distribution panel with breakers
Midnite Solar Combiner Box MNPV3
Tri-Metric 2020 with shunt and 48V adapter
Exeltech 1100 watt 120 volt true sine inverter
Various other bits and cables and wires

You can see my setup and the batteries I purchased in Chile here:
http://lesnagy.ca/?p=167

Now the batteries I purchased seemed to only have 1/3 or their rated capacity when I started to use them, and during the 8 months it took to try and get the company to replace them, then give up and buy batteries from the US, they dropped to 1/8 capacity. The short story of these batteries is that they appear to be very old stock, probably purchased by the company I dealt with for nothing and resold to me as new fresh stock with their new labels on them.

So I purchased 12 UB-8D AGM UPGI (Universal Battery) batteries from a US reseller. The good news is that these batteries seem to be working to spec or above. I have been using them for a month and they follow the discharge curves as published by UPGI almost perfectly.


Now on with the overall performance of my system since the new batteries were installed.

Constantly during 24 hours I use somewhere around 280 watts as a minimum value. This load comes from a fridge, lights, and a couple of notebook computers.

During the day I use a 900 watt coffee maker that runs for about 10 minutes, a 2400 watt electric kettle a couple of times a day for 3 or 4 minutes, a 1400 watt microwave for 5 to 20 minutes, a desktop computer that I turn on to do specific work that draws around 500 watts with the monitors. I also have a satellite TV receiver and a 32" HD TV with a 5.1 surround system and a 200 watt sub-woofer. My gas stove also has an electric grill at 2500 watts that gets used very occasionally.

For comfort, I have an in the wall Air Conditioner/ Heat Pump at 900 watts and a electric blanket on the bed at 60 watts. I have used the AC/Heat Pump for hours at times and the electric blanket almost every night all night. The electric blanket as a duty cycle of about 60% and AC/Heat Pump varies according to the ambient temperature.

After setting up my Tri-Metric for the new batteries as specified I have watched the system closely using the information gleaned from the XW System Control panel and the Tri-Metric.

Given the general usage of my system as listed above, I have not had the batteries drop below 76% consumption and never below 49.1 volts. An average harvest from the panels has been around 10 kWH per day. I have seen a peak of 13.5 kWH a couple of days. This is with my panels still lying on the ground and they are now starting to be partially shaded by the container they are sitting beside during the morning and afternoon. I am sure that when they are optimally placed (hopefully very soon) on a frame and angled to the sun I will be able to harvest closer to 15 kWH or more per day.

I have made no real effort to conserve energy other than to not get carried with energy usage. After my 8 months with failing batteries perhaps I pay more attention to energy than I might have. It took me a week to stop being obsessive with watching the Tri-Metric like I had to with the old batteries. It is also a relief to not need to tolerate the noise of a generator every night for an hour or two to keep the batteries alive for the night.

So it is possible to live basically "normally" totally on solar power with just a little bit of care. My location helps greatly here for this however. My house is at 2450 meters (8000 ft) altitude, more than 300 clear days per year, and the driest desert in the world. I could not have better sun conditions I think.

As far as the equipment I purchased goes I have a few comments.

I like the Xantrex XW setup. It has its faults like inaccurate meter readings at the low end and flaky generator syncing. The Midnite Solar panel is a MUST IMHO for this kind of system as it made wiring nice a neat and puts everything you should have for for all your connections and breaker all in one nice tidy package. A battery monitor is a must for any system and the Tri-Metric does a nice job for a basic system.

The solar panels have performed as they should and they have also proven to be tough. I had one panel on a piece of cardboard and the wind caught it and flipped it over onto the one beside it. I was horrified when I saw the situation but when I flipped the panel back over all I found was a slight rub mark on the glass of the panel where the flying panel hit it with its corner on the way down.

The Exeltech inverter has performed flawlessly while powering my lathe and other tools that I brought with me from Canada. It was cheaper to buy the inverter than to buy all new tools and motors.

The biggest lessons learned are that you should have a generator no matter how good you think your system is for those just in case times, and that the best batteries for the desert are AGM type. They are worth the extra cost, plain and simple.

I hope the information in this post is helpful to someone as I certainly have gained a lot of knowledge on this forum and gained a lot of experience in a very short time.

icarus

Re: A short history of my system and how well it works.

My initial reaction is,,, you have 1800 watts of PV, and my guess is that you are using more than you might ought to.

My rule of thumb for off grid, is to take the name plate rating of the PV, divide that number by 2 to account for all system loses, then multiply that number by the nubmer of hours of good sun you can expect, year round on a daily average basis. (I use 4, it sounds like you might well be able to use say 6. 1800/2*6= 5400 wh/day. Your standing load of 280 watts 24/7 makes ~6.7 kwh/day, already more than a base line capacity. Add in all the resistance heating appliances, the extra desk machine, HVAC, electric blanket etc and I can easily see how you are on the road to killing your batteries unless there is someting I am missing. (I understand that you are probably nearer the equator so your days are longer than my mid winter, but shorter than my mid summer).

Personally, I consider using any resistance electric heating element appliances (coffee maker/tea kettle etc) on any but the biggest PV system is a no/no. I would consider a stove top coffee maker like the coleman Mr. Coffee work great, with out loading the PV system for example. Even the 60 watt blanket, drawing 50% duty over 8 hours is 240 wh.

Just for the record, we live with 400 watts of PV, we can generate ~1.2-1.5 kwh/day on an ideal day. We routinely draw ~6-800 wh/day.

Have you actually Kill-a-Watt metered your real loads?

Am I missing something?

Tony

Les Nagy

Re: A short history of my system and how well it works.

Tony:

I have looked carefully at my loads and usage. I have monitored the voltages of the batteries and kept an eye on total amps drawn from them between charges. Everything adds up to a healthy system with full recovery of the batteries every day.

The batteries have never dropped below 49.1 volts (48 volts bank of course) and during only the hardest use on a couple of days did they not get fully charged back up. Even then they get close to fully charged and when the sun goes down they run at 51.7 volts under load at the start.

Maybe you are missing something, or I am, but everything looks good with my system as I described it.

Remember, I have ideal sun conditions. No pollution, no clouds, thin air (high altitude), and no moisture in the air at all. So given these variables I might be actually getting more like the equivalent of 8 sun hours per day. Remember that I am watching what the MPPT60-150 says it is pumping into the batteries. It is possible that is reading high. If I guess an average voltage seen by the batteries during the day and read the total AH pumped into the batteries at the end of the day as measured by the Tri-Metric I get a value close to the 11 kWH that the MPPT60-150 reports.

I hope all my observations are right as I do not want to kill my new batteries.

P.S.
I just reviewed the spec sheet for the batteries and they reach basically the 6 hour voltage point on a 20 hr discharge curve. This jives with my observations.

icarus

Re: A short history of my system and how well it works.

Like you said, you are getting ~10kw out of the system. By my calculations you must be getting at least 7 hours of enough sun to put out 80% of Name plate. Pretty good harvest.

Sound like your PV is putting out ~25-30 amps into 48vdc?

The difference between your situation and many, is the difference in sun hours relative to season. We get better than 18 hours of sun mid summer, but only~7.5 in the winter. Even the 18 is hard to harvest because of the rotation of the sun across the sky, hence the four hour average, week in week out over the course of the year.

Keep taps on it and keep in touch.

T

MisterB

Re: A short history of my system and how well it works.

Wow, you really do live in ideal solar conditions. The Atacama desert is the driest desert on the earth. I just looked up San Pedro de Atacama on Wikipedia and you're at 7900 feet(2408m). I live at 7300 feet(2226m) and where I live would be refered to in Spanish as "altiplano" but I live in a very wet desert--just a few more inches of rainfall a year and this wouldn't be desert at all. Tonight we had our first light snowfall of the winter. In addition to harvesting solar and wind energy, I also harvest rainwater and store it in an 1800 gallon cistern. I like reading about off the grid systems in extreme climates and yours certainly qualifies.

It looks like you've done things right with your system and you should be enjoying it for years to come without any major issues. I installed my first solar array around 1989 with used Arco panels manufactured in the 1970s and that array is still producing about 80% of it's rated capacity. You are not abusing your batteries so they should give you years of service.

Les Nagy

Re: A short history of my system and how well it works.

icarus wrote: »

Like you said, you are getting ~10kw out of the system. By my calculations you must be getting at least 7 hours of enough sun to put out 80% of Name plate. Pretty good harvest.

Sound like your PV is putting out ~25-30 amps into 48vdc?

T

I have seen 23 amps peak going into the batteries as indicated by the Tri-Metric. At that moment I believe that the MPPT60-150 was reporting 28.5 amps output. The balance was going to the running appliances at the time.

Les Nagy

Re: A short history of my system and how well it works.

MisterB:

Yes, I agree. There cannot be any better solar conditions than where I live now. I moved here not for the sun though, but rather the other stars. I am an astronomer and there is no better place in the world to live and have a telescope.

icarus

Re: A short history of my system and how well it works.

Les Nagy wrote: »

MisterB:

Yes, I agree. There cannot be any better solar conditions than where I live now. I moved here not for the sun though, but rather the other stars. I am an astronomer and there is no better place in the world to live and have a telescope.

Cool! I bet you don't get the Aurora much though.

T