Just bought this and need suggestions

[SolarQueen]

Just jumping in to the game now. Your location and loads list is exactly what is needed for this group to be able to help you. With the couple of corrections you made in the loads list, like the washing machine running occasionally, the microwave running less than an hour, etc, I think everything does round out to about 10kWh a day. Perhaps on days that you run a load of laundry, you turn off one of the fans to make up for it. Based on snoobler's 5.14 sun hours, which as he explained, is not hours of sun, but total time the sun equals the strength of noon, i.e. from 8am to 10 pm probably equals 1 sun hour, where from noon to 1pm is also 1 sun hour. 10,000Wh a day / 5.14 sun hours / .6 system losses = 3,200W of solar.

The size of the battery bank depends on what type of batteries, lead acid or lithium, and how many days without sun you need to run them off batteries before the sun can recharge them. Based on your other post, I'm assuming lithium. You don't want to use more than 80% of the stored energy in lithium batteries, so for 10kWh used a day, you want a 12.5kWh battery bank. That's assuming one day of storage. If you expect to have several days without sun, then you need to multiply that by the number of days you want battery backup. In the Caribbean, you probably won't have all that many days without sun, and on those days, you can chose to not run the washing machine and maybe turn off a fan to save energy.

The KiloVault HAB you were looking at in the other post has 7.5kWh of storage, so 2 of them would be plenty in my opinion at 15kWh. If you are interested, we do have them in stock in Puerto Rico, so shipping cost may not be as much as buying them from mainland US.

 

[snoobler]

Regarding your post here:

KiloVault Battery, is it good?

I haven't seen Will do a review on this. I'm still learning solar and figuring out my power needs. Yes, I've been told to do my work and I'm doing so but was looking at the type of batteries and I know lithium is costly but leaning more towards it. Is it best to build your own LiFePO4...

diysolarforum.com

Two of those would give you about 24 hours of backup at your normal power usage.

 

[snoobler]

total time the sun equals the strength of noon

OMG... thank you for that. I just couldn't come up with something so simple. I'm using it from now on.

 

[SolarQueen]

OMG... thank you for that. I just couldn't come up with something so simple. I'm using it from now on.

Took me about 10 years to come up with a simple explanation for that one.

 

[crucian]

I question the peak sun hours. The questions isn't, "how many hours/day you have sun?" It's how many hours of equivalent peak charging do you get? Since you're in the Caribbean, I highly doubt you get 11 hours of peak solar per day. No place on earth gets that.

From the link in my sig:

Solar Irradiance Calculator

www.solarelectricityhandbook.com

View attachment 19302

Kingston, Jamaica in the Carribean has a minimum 5.14 hours of solar irradiance per day in December. This assumes panels are due south and at the optimal 18° from horizontal.

That means in order to satisfy your 15.1kWh per day use, you would need:

15.1/5.14 = 2.9kW of panels.

Almost twice what you've estimated.

These are my numbers based on the site you showed:

an	Feb	Mar	Apr	May	Jun
4.89	5.66	6.52	6.88	6.69	6.93
Jul	Aug	Sep	Oct	Nov	Dec
6.92	6.76	6.15	5.58	4.78	4.57

I understand the peak hours but even during non peak hours, solar collects energy but just not as much right? Sun usually rises around 5:30am and sets at about 6:45pm

 

[snoobler]

Those numbers ASSUME you get charging all day while the sun is out and on the panels. If you don't get all day sun exposure, your actual harvest will be worst.

For December all day charging is the same as 4.57 hours of high noon charging even though you may be charging for a total of 11 hours.

15.1/4.57 = 3.4kW of panels.

If SQ and I disagree, we're both right, but she's more right.

 

[SolarQueen]

I understand the peak hours but even during non peak hours, solar collects energy but just not as much right? Sun usually rises around 5:30am and sets at about 6:45pm

Right, the amount of solar energy at 6AM is probably about 1/4 of that at noon. So you can't count them the same. That's where sun hours, or insolation hours comes in. People much smarter than I am put together the numbers so you can compare apples to apples. They take local weather, temperatures, sunrise/sunset, all of that into account. So you get the most sun hours in June, and the least in December. You generally design an off-grid system based on the worst numbers you will be dealing with. If you never lose power in the winter, then you can use the higher sun hours from the summer (hurricane season).

 

[SolarQueen]

Those numbers ASSUME you get charging all day while the sun is out and on the panels. If you don't get all day sun exposure, your actual harvest will be worst.

For December all day charging is the same as 4.57 hours of high noon charging even though you may be charging for a total of 11 hours.

15.1/4.57 = 3.4kW of panels.

If SQ and I disagree, we're both right, but she's more right.

Snoobler and I are both getting to about the same watt number with different assumptions. I assume you will use less energy that the list, as some of the bigger consumers are intermittent. The reason we are within a couple hundred watts of each other, is I also assume only 60% of the energy you make will actually survive the whole process and you will lose about 40% from voltage drop, inefficiencies, less than ideal setup, etc. Other than that, the snoobster (my new pet name for you, that won over the snoobinator) and I tend to agree.

 

[snoobler]

My point was that I'm a self/interwebz-tought hack, and you've been doing this for years commercially. You've already made your many mistakes and learned while putting in your 10,000 hours. I'm still bestowing lessons of wisdom to those who see me fail.

 

[SolarQueen]

You've already made your many mistakes and learned while putting in your 10,000 hours.

OMG. You just made me calculate how many hours I've been in the solar biz. 40 hours a week for 12.5 years = 26,000 hours. Dang!

 

[svetz]

...I understand the peak hours but even during non peak hours, solar collects energy but just not as much right?

Right! You can predict by how much.

At solar noon there's the least amount of atmosphere between the panels and the sun; the greater the angle the more the air robs the sunlight of the energy coming to them. The graph to the right shows the maximum possible percentage of power based on the elevation of the sun that you could get if you had a solar tracker, with fixed panels it'll be less. ... Sun usually rises around 5:30am and sets at about 6:45pm... Every hour is ~15°. So, at 5:30 the sun altitude is 0° and at solar noon 90°. At 0° you're getting 0 power and at 90° the maximum is ~1000W/m^2. The sun's power is only 50% (500W/meter squared) at 30° altitude (roughly 8 A.M.); so a 300W panel would only output 150W max.

In practice it should be less due to dust, clouds, etc.

OMG. You just made me calculate how many hours I've been in the solar biz. 40 hours a week for 12.5 years = 26,000 hours. Dang!

That's why you're the queen!

 

[snoobler]

@SolarQueen I don't believe for a second that you only do this 40 hours per week.

 

[crucian]

OK, in doing research and a few easy math, I came up with what my solar system results would be but need help to make sure I did it right and need to know if I went with a 48v system, how do I know how many lithium batteries would best suit my system as well as how many solar panels I would need?

My utility company cheats us badly. Last month my kwh was 339, this month it skyrocketed to 684. Here's what it was in the preceding months: 355, 336, 325, 362, 437, 407, 448, 327, 395, 470, 443. This gives you an example of my kwh for the last year. With everything being about the same each month, I can't tell how the bill skyrocketed.

This is what I calculate my system be at to run the basics with refrigerator, microwave, fans, tv, bluray player, washer and lights on a 48v lithium battery system.

System Calculation Results - 5943 watts per day x 1.5 (loss) 8915 watts x 4 days (autonomy) = 35658 watts / 48v = 743 amp hours + .25% or 186 ah (loss) = 929 (930) amp hours

 

[crucian]

@snoobler any suggestions to above?

 

[snoobler]

I'm assuming by watts per day you actually mean Watt-hours per day? If that's the case...

1.5X loss is ultra conservative.

25% loss applied a second time is also conservative

5.9kWh/day = 5.9/0.85 (DC-AC conversion inefficiency) = 6.9kWh/day

4 days = 27.8kWh/day

If using FLA/AGM, you need 2X that at 55.5 kWh (48V/1157Ah)
If using LFP, you need X/.8 that at 34.7kWh (48V/723Ah)

That will allow for 4 days with ZERO sun or backup generator based on the consumption you've given.

 

[schmism]

Last month my kwh was 339, this month it skyrocketed to 684. Here's what it was in the preceding months: 355, 336, 325, 362, 437, 407, 448, 327, 395, 470, 443. This gives you an example of my kwh for the last year. With everything being about the same each month, I can't tell how the bill skyrocketed.

You need to check your billing. That looks like a projected billing type scheme and then there is a "catch up" month when they need to reconcile the actual usage to what they "estimated" you would use.
Its my understanding that virtually all new utility accounts are set up this way as the utility experience has showed them that people are really bad at budgeting and can not deal with the fact that in the spring/fall a $50 utility bill means a "windfall" month and then july/aug when you run the AC 24/7 they arn't prepared to pay $300 so the utility does the avg for them.
I had to specificly request to be not put on the avg-plan when I signed up last time.

 

[crucian]

You need to check your billing. That looks like a projected billing type scheme and then there is a "catch up" month when they need to reconcile the actual usage to what they "estimated" you would use.
Its my understanding that virtually all new utility accounts are set up this way as the utility experience has showed them that people are really bad at budgeting and can not deal with the fact that in the spring/fall a $50 utility bill means a "windfall" month and then july/aug when you run the AC 24/7 they arn't prepared to pay $300 so the utility does the avg for them.
I had to specificly request to be not put on the avg-plan when I signed up last time.

My utility company installed what they called smart meters that is supposed to give them real time data and even cut you off and turn you back on with the push of a key stroke. They came out and took out the old meter and installed the new one, I stood right next to the guy as he did it. If it's a smart meter then this shouldn't be any projected or estimated billing. I rarely ever believe anything coming out their mouths as it's usually all lies.

 

[crucian]

I'm assuming by watts per day you actually mean Watt-hours per day? If that's the case... YES THAT'S WHAT I MEANT

1.5X loss is ultra conservative. WHAT WOULD BE A GENERALLY GOOD PERCENTAGE OF LOSS TO USE?

25% loss applied a second time is also conservative WHAT WOULD BE A GENERALLY GOOD PERCENTAGE OF LOSS TO USE?

5.9kWh/day = 5.9/0.85 (DC-AC conversion inefficiency) = 6.9kWh/day

4 days = 27.8kWh/day

If using FLA/AGM, you need 2X that at 55.5 kWh (48V/1157Ah)
If using LFP, you need X/.8 that at 34.7kWh (48V/723Ah)

That will allow for 4 days with ZERO sun or backup generator based on the consumption you've given.

Thanks for the reply. Would it hurt to have too many panels/batteries? I'm using some used 250w panels. Do I have to stick with 250w panels? If I get 300w or more, can I add them to my solar array? I know batteries must be the same and once I start, I have a short window to add batteries but just wondering if I need 723Ah if it would hurt if I got say 1000Ah LFP.

 

[schmism]

If it's a smart meter then this shouldn't be any projected or estimated billing.

Again they may know exactly what the usage is, however you still may be on a "budget bill" "even pay" plan. In which case there is still a catch up month.

 

[morth]

Again, I live in the Caribbean so this would be a system to use rather than a generator in case a hurricane or tropical storm hits and we go without power for weeks as we did when Maria hit and we went months without grid power. Also, my local power company does these rolling blackouts sometimes. I'm also taking into consideration the panels aren't damaged by a storm.

I found a local guy who sells solar batteries and he says we work on 13 hours of sunlight here but to me, it's more like 10-11 hours of sunlight. I also did some research used an online calculator putting in which appliances and lights I'd need initially and here are my numbers, does that look right? The washer would only be used once a week and figured clothes can dry on a clothesline.

Appliance​	Quantity​	Watts​	Hours On per Day​	Watt Hours per Day​
Fridge - 20 cu. ft. (AC)	1	59	24	1416
Microwave	1	1000	1	1000
Box Fan	1	200	13	2600
16	2	200	10	4000
Ceiling Fan	2	120	3	720
Clothes Washer	1	800	1	800
TV - LCD	1	150	5	750
Bluray Player	1	15	5	75
LED Bulb - 60 Watt Equivalent	11	13	2	286

System Calculation Results​
Killowatt Hours per Month:	454 kWh
Peak Sun Hours:	11 hours/day
Solar Panel Watts:	250 W
Number of Panels:	7
System Size:	1.65 kW

The fridge and microwave numbers are too low and those are your main consumers. I have a 1000 Watt (cooking power) microwave and it pulls 1700 Watts when running . Check your microwave, there should be a sticker some place that will show the voltage and max expected Amp draw. Multiply those 2 and you have max Watts. Do the same for your fridge. My 21cf fridge/freezer hits 450 Watts on start, then settles down to 120 running. On the fridge, see if yours has a way to disable the defrost cycle. On my fridge, defrost runs for nearly an hour and consumes 300 Watts while doing it. I would leave defrost enabled for normal use. When running on battery, I would disable it.

Given your location, roof damage is a very real possibility during a hurricane. You may want to consider storing a few panels inside in a safe location just in case the roof system ends up on the other side of the neighborhood. I have a 200 Watt Renogy solar suit case, 12 volt system that is very portable and can charge just about any battery chemistry. With a 2000 Watt inverter and 2 batteries in parallel, I can run the microwave when needed and it will run my fridge for about 26 hours. It can't replenish discharged batteries quickly (only 10aH rate), but it's enough to keep the fridge going for a long time.