Solar panel beginner- getting the most out of my set-up

Hey all

This was the most obvious place for me to start pulling my research together.  I’m just  starting to look into solar panels. My focus here is just the setup part not the panels .  I’m not an electrician so a good question for me to ask is, how can I get the most out of a set of panels. Where would I be losing energy, in a setup or in a  product?  What would you consider an  efficient setup?

Jason Fay wrote:Hey all

This was the most obvious place for me to start pulling my research together.  I’m just  starting to look into solar panels. My focus here is just the setup part not the panels .  I’m not an electrician so a good question for me to ask is, how can I get the most out of a set of panels. Where would I be losing energy, in a setup or in a  product?  What would you consider an  efficient setup?

Start with an mppt charger from the word go. You will get better production on overcast days, be able to purchase cheaper per watt panels and run thinner wire from your panels to the controller than if you use a cheaper pwm charger.

Jason Fay wrote:Hey all
how can I get the most out of a set of panels. [...] What would you consider an  efficient setup?

Hey, I have set up several solar systems now, and have been living off grid on solar power for a while now.

To your first question, I will say that this seems to imply a limitation in the number of panels you could have. From a cost perspective, this is not really the case anymore - panels have gotten quite cheap relative to the other components in the system, so it is really not that much more expensive to have a bit of "extra" capacity in your array. Now, if you are constrained by available space, not budget, then there are ways to make sure you harvest every last electron from a given array size. If that is your situation, I would suggest you get a massive battery, or set up a dump-load system where once the batteries are full a controller will start powering a hot water heater, for example.

So, and efficient setup with solar is a flexible setup. You will need to calculate your energy budget very carefully by measuring how much load all your appliances draw, and then work backwards from there. If you come up with a usage of 1 kwh per day, for example, then you would probably want a battery that can provide 4 or 5 kwhs of power (depends on how cloudy your climate is, but this is a good rule of thumb). Then size your array based on the battery: depending on chemistry, there will be limits to how much current they will accept during charging. Having more solar power than is usable is not very efficient if it is sunny 300 days a year, but might make sense if it is cloudy 300 days - the larger array will harvest more power on an overcast day. I would say 1kw of array per kwh of usage would be good in a relatively grey place (like here in Oregon) If you live in the southwest, you could likely cut that in half.

Flexibility will become more and more important the "leaner" your system gets. If you can shut off loads to save power during cloudy spells, then you can get by on a much smaller system most of the time. Things like fridges, freezers, and the inverter to run them (Having an inverter just standing by is easily my biggest load, btw) will need to be powered pretty much 24/7. Stuff like laundry and vacuuming the floors can wait for sunny weather. Anyway, if you have any more questions as you progress in your research, feel free to ask away!

Small System ($4,000 for 4KWH/day)
$1,000 Solar Panel + Support (1KW with the avg 4hrs/day = 4KWH/day)
$600 Charge Controller (48v x 20A equal a 1KW charge controller, get a MPPT they are the best)
$1,000 every 3yrs Battery (at least 1days worth of usage but aim for 3days, so 4KWH = 48V x 100Amp-Hour)
$1,000 Inverter (120V, 4KW so that you can run most devices/appliances)
$10 Wires (thicker wires, shorter runs and higher voltage means less system loss)

Medium System ($20,000 for 24KWH/day)
$6,000 Solar Panel + Support (6KW with the avg 4hrs/day = 24KWH/day)
$600 Charge Controller (48v x 120A equal a 6KW charge controller, get a MPPT they are the best)
$6,000 every 3yrs Battery (at least 1days worth of usage but aim for 3days, so 24KWH = 48V x 500Amp-Hour)
$6,000 Inverter (240V, 12KW so that you can run big motors/etc, but you can do 120V, 4KW to save money)
$60 Wires (thicker wires, shorter runs and higher voltage means less system loss)
https://unboundsolar.com/1891771/unbound-solar/solar-kits/5.92-kw-grid-tied-backup-system-with-sol-ark-inverter-16-astronergy-solar-370-watt-panels-and-agm-battery-bank

Alternative System ($20,000, 10am to 2pm is when you would have to run most of your equipment, almost like direct solar)
$12,000 Solar Panel + Support (12KW with the avg 4hrs/day = 48KWH/day)
$1,000 Battery (so 4KWH = 48V x 100Amp-Hour)
$6,000 SolArk Charge Controller+Inverter (240V, 12KW DC input and AC output so that you can run big motors/etc)
$60 Wires (thicker wires, shorter runs and higher voltage means less system loss)
(you can also just think of this system as being grid-tied, with the option to still work even with a power outage, and the option to get a full 24KWH battery pack after 3yrs)

Alternative DC System ($20,000) 10am to 2pm is when you would have to run most of your equipment, almost like direct solar)
$12,000 Solar Panel + Support (12KW with the avg 4hrs/day = 48KWH/day)
$6,000 every 3yrs Battery (at least 1days worth of usage but aim for 3days, so 24KWH = 48V x 500Amp-Hour)
$1,000 Inverter (120V, 4KW so that you can run most devices/appliances)
$60 Wires (thicker wires, shorter runs and higher voltage means less system loss)
(DC motors for tools/ac/fridge/washer/dryer/blower fans/etc, this involves alot of DIY)

What about the newer batteries, how are they looking cost wise compared with the notes from S. Bengi?

The newer batteries, LiFePO4 cost a little less than $1000 per 1000Whr. Technically someone could build one for about 1/3 that cost.

LiFePO4 batteries are great because they can be fully discharged without it affected their lifetime throughput/cycles, they don't waste energy and overheat once they past 80% charge, so the battery bank can be smaller. They can be charged and discharged ~8000 times, so they don't need to be replaced as often. They are lighter and smaller. They can be fully charged/discharged in just 1hour aka 1C, so you can oversize your solar panel/inverter aka have a smaller battery bank

https://unboundsolar.com/9989910/fortress-power/batteries/fortress-power-eflex-5.4-kwh-lithium-ferro-phosphate-lfp-battery
https://unboundsolar.com/9580114/simpliphi/batteries/simpliphi-phi-1.4-kwh-12v-115-ah-lfp-battery
https://unboundsolar.com/9979990/discover/batteries/discover-battery-aes-7.4kwhr-48vdc-with-xanbus-lithium-lfp-battery



I have seen some subpar LiFePO4 batteries going for super cheap, but their charge/discharge rate is very very low and the amount of cycles is unlisted but I estimate it to be only 700cycles
https://bigbattery.com/products/48v-ape-lifepo4-233ah-11-2kwh/

The solar system you buy needs to be proportional to the size of your house and how much energy you and your family consume. If you have a smaller home, you can get away with a 5KW solar system off grid. If you have a three-story home with many big appliances, you might consider the 10KW off grid solar system price option, even if it can be a bit more expensive. Go for panels that can give you the highest energy conversion rates. Try purchasing solar panels made with monocrystalline solar cells, which are known to be very efficient in absorbing light energy. This will allow you to make the most out of your stand alone solar system.

Jason,

Since no one has asked, is this just an experiment or are you planning on powering your home or something in between?

I just dabbled in solar energy recently with a little homemade “battery box” and a roughly 30 watt solar panel to charge the 15 amp 12 volt SLA battery.

The little panel (about 12”X18”) charges on cloudy days, inside sitting in sunlight filtered through a window and of course sitting outside.  I personally found that as long as the panel was laying flat on the ground or slightly tipped in the direction of the sun, it worked fine.  It was not necessary to aim the panel directly at the sun and track it all day.  Obviously, keeping it out of shade is important but I was surprised by how flexible the placement could be.

Incidentally, I need to store the panel with a piece of cardboard over the panel or better still, keep it in total darkness.  Since I have electrical lines coming off, I don’t want an accidental short and this can happen from even surprisingly small amounts of light.

I am not exactly certain if this is the type of answer you were looking for, but if so, you know my thoughts.

Eric

S Bengi wrote:The newer batteries, LiFePO4 cost a little less than $1000 per 1000Whr. Technically someone could build one for about 1/3 that cost.

Are the blue square one worth considering?
https://www.aliexpress.com/wholesale?trafficChannel=main&d=y&CatId=0&SearchText=LiFePO4<ype=wholesale&SortType=price_asc&minPrice=40&maxPrice=999&page=1&groupsort=1

The hybrid inverters i am looking at all want a 48V battery system.
While lead-batteries have no BMS and thus can be connected in series, what is the situation with LiFePos?
Can i take 4 (identical) 12 Volt LiFePo-batteries and connect them in series, or do all cells need to bee connected
to the same 16S balancer?


I was told i should go for a sperate inverter and charger, but it seems to me that this is more expensive than the hybrid solar inverter.
Also the hybrid units support AC input and most of them can be run without batteries, while the stand-alone MPPT-Chargers explicitly
say do not connect the inverter
All-in-all the topic is rather complicated so i think going for the hybrid unit is the way for me, as it also saves me time in reseach,
and time is a big factor right now, for those of you who do not know it : The italian harbours are being blocked, so  at least in EU we will
run into immense supply issues in the near future.
Nevertheless i want to mention another argument for the sperate inverter:
If your inverter is seperate from the rest of the system you are not dependet on new/fancy transformatorless inversters,
but can go with an old-school copper-based transformator. The advantage this gives is that transformatorless inverters
can give you the peak power for like 20ms while the big coils in a transformator act as buffer, effectively giving you 2-5 seconds
of peak power.

To follow up on some of your questions.  I have a 24V Conext that though can not grid-connect, can receive AC input for battery charging.  My XW+6848 can grid connect if there was one (none).

Whether or not a Li battery with a BMS can be wired in series is manufacturer specific.  Unless the manufacturer says they can be placed in series, assume they can not.  All lead-acid batteries can be wired in series.

Inverters can be divided up into low-frequency transformer based models, and high-frequency transformerless models.  Transformer based handle very large surge starting currents, for from 5 to 60 seconds.  Transformerless inverters have no meaningful surge, being limited to maybe 200% for only 8-16 milliseconds.

Most All-in-One (AiO) units like the MPP are transformerless units.  Things that have an electric motor that starts under load will have a high surge startup current draw, in the range of 3-5X the running current.  That means things like refrigerators, air-conditioners, compressors, and well-pumps.  

I have a Schneider XW+6848 inverter, which is a transformer based sine-wave inverter.  I need that to run my 240VAC well-pump, which runs at ~2000W, but requires 9200W at startup.

You can measure the real-world startup currents of any equipment with a clamp meter like a Uni-T 216C, which can measure "inrush current".  A regular clamp meter is not fast enough to measure the inrush in the first second or so.  The 216C also measures DC current, and I think it's perfect for monitoring an off-grid solar system.

Will the system need to be easily moved, or will it be stationary in a building where weight isn't an issue? I'm pondering lithium vs lead acid but since it won't be moved often the weight doesn't matter much to me, and I consider the Rolls 5000 series (like https://rollsbattery.com/battery/6-cs-21p/ ) to be the FLA standard to beat, as they will give 4500 cycles at 50% discharge, and around $1000 will get you over 4kwh of storage (2kwh usable).

I have little faith in ordering from an overseas distributor and getting warranty support if a battery fails a year in, compared to bringing it back to a store, but maybe I'm wrong about that. If the batteries need to be mobile then lithium makes a lot more sense, but so far I've yet to find any for less than double the price of FLA.

Didn't see replies back from OP, so don't really know much about the application requirements ...

We had Rolls-Surrette FLA batteries ... we, too, managed to kill our first set way sooner than we thought, even knowing that this might happen. Maintenance is *very* time-consuming and problematic. While we were not happy dealing with the weight and size aspects of FLA batteries, that might have been the least worries with this technology. If at all possible, try to get to LiFePO4 technology ...

Also,and again not knowing OP requirements, we went the propane generator, then batteries/inverter, then solar panels & such acquisition route. It's not for everyone, but we didn't mess with calculations, living within those calcs (next to impossible in this family of four), and so on ... just added/improved each piece as we could. Endless power this way ...