Sizing a Solar set up to meet the demand of a device?

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claybcook
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Sizing a Solar set up to meet the demand of a device?

Post by claybcook » Tue Mar 13, 2018 2:37 pm

If I'm trying to power a specific device, rather than just attempt to keep batteries charged, how would I do this? My camp needs a pump to get the grey water from the evap pool to the grey water tank. I'm looking at one of various sump pumps at HD. All of them specify amps drawn, etc. How would I take the needs of the pump to size the solar system to power it? Same question if I were to try to power a refrigerator: begin at the need and build back to meet that demand. How?
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Captain Goddammit » Tue Mar 13, 2018 3:30 pm

You’re not quite making sense, generally batteries run the device and the solar panels keep the batteries charged.
Skipping the batteries is a crummy plan, especially for a must-not-fail system like your evap cesspool (another bad idea).

I take it you’re not a solar hobbyist, which is normally the only good reason to run solar at Burning Man. Just practically speaking, solar isn’t a good way to run temporary power. It’s more money and hassle than it’s worth.
In a semi-permanent installation things are different.
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Token
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Token » Tue Mar 13, 2018 3:48 pm

Super easy.

Find someone in camp that understands AC and DC electricity, Amps, Volts, Watts, and the likes, then delegate.

For grey water transfer, these are awesome and powered by BPR or Whiskey!

Image

For running a fridge, look at the Volts and Maximum Amps, multiply them to get the Watts. This is very important and used everywhere.

Take that Watts number and multiply by 1.5 and that is the size of inverter needed.

Next you need to estimate the duty cycle of the fridge - I.e. how long the motor actually runs during an hour, on average over a 24 hour period. Take that runtime per hour average and multiply by 24 hours. Write that down as it is used to figure thhe size of batteries and solar panels.

Now, them Watts we figured earlier, multiply that with the duty cycle for the 24 hour period we just figured - that is how much energy you need to generate and store in the batteries over that 24 hour period. It will be expressed as Watt-hours. Or more likely KiloWatt-hours.

Now the tricky part; batteries usually are 12V and have a rating of Amp-Hours. So we gotta covert that into Watt-hours so we can have apples and apples. Take your battery Amp-Hours, multiply by the battery voltage of 12V and divide by 2 because batteries should never discharge below 50% capacity or they get ruined.

Now you can figure out how many batteries you need. Take the Fridge Watt-hours number and divide by the battery Watt-hours and round up.

Are you sure you don’t want to delegate to someone ... the solar panel one is even worse as we need to deal with the sun moving across the sky, inclination, azimuth etc ...

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Re: Sizing a Solar set up to meet the demand of a device?

Post by Popeye » Tue Mar 13, 2018 5:38 pm

Thank you Token. Very well put. If you don't mind I might copy that.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by claybcook » Tue Mar 13, 2018 7:42 pm

Unnecessarily judgemental guys. Any post that begins, "You don't know enough to..." should disqualify the poster. If this isn't the place to ask questions, where should I go?

Given the vast range of panels and inverters and devices contemplated, it seemed easier to cut to the chase and ask the fundamental question rather than wait for the specifics to materialize before any question could be asked.
A device will use power at a certain advertised rate.
A battery can store a certain quantity of power.
A solar panel can recharge that battery at a given rate.
The inverter can process the DC into AC at an advertised rate.

I know there is a fundamental equation here; I just don't know it. Hence; asking for help.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by Captain Goddammit » Tue Mar 13, 2018 8:41 pm

All of that is false. Literally all of it.

So clarify... are you trying to skip having a battery in the system?
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Re: Sizing a Solar set up to meet the demand of a device?

Post by motskyroonmatick » Tue Mar 13, 2018 9:32 pm

Here's a real world scenario for you. I ran an evaporator for a camp of 3 having minimal showers off of a Harbor Freight Solar panel setup. The only thing ran was a low amperage 12 volt DC bilge pump lifting water 4' to the top of the evaporator. It worked perfectly and the battery did not run out of charge in the night.

They key to continuous power was a power draw(consumption rate) that did not drain the battery(big enough capacity) during the non charging period(overnight). A charging system that simultaneously could charge the battery to max capacity and power the system during the charging hours(direct sun). Regular maintenance to make sure panels were relatively clear of dust and oriented to the sun.

BUT

The solar set up cost about 150 bucks at the time

I bought different charge controller for about 25 bucks

The battery cost me 150 bucks (It was a really nice battery)

Were already at 325 bucks here and all I really got was in-between 1 and 2 amps of power use 24 hours a day for 5 or 6 days. I might have spent as much on the project as I spent on my Burning Man ticket that year.

It was a neat little project that worked well and at the time I had money to spare but it is pretty ridiculous to spend that kind of money for so little power. I think alot of solar power things end up this way on the Playa.

Research 12 volt DC bilge pumps. They are much more conducive to using with solar power than 120v AC motor powered sump pumps. Some come with float switches which can be super handy.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Token » Tue Mar 13, 2018 10:10 pm

I just love it when someone asks a vague question then complains about the provided solutions or advice.

It is impractical to design a solar solution that does not have some form of energy storage.

There are rare scenarios where this is done - solar attic vents, small gadgets like calculators.

Why is it impractical? Because solar panels are big, bulky, expensive plus don’t produce constant energy and very few devices run 100% duty cycle or can tolerate variable power input based on light availability and efficiency.

So, the whole pump thing can be done with a battery and say a 50W panel or no battery and a 400W panel for the 30 minutes you run the pump per day.

Similar for the Fridge question. It will be big, heavy, bulky, expensive.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by FlyingMonkey » Wed Mar 14, 2018 10:09 am

You will need to "no-shit" evaluate your power requirements and scale your system from there. If all you are doing is using a solar panel to pump grey water then you can probably get by somewhat cheaply. If you want to start out small & grow your system over the years then you can spread the cost out.

What pumps are you looking at? I would recommend using an RV or boat pump rather than something from HD. Your requirements will be much less than a house sump pump.

Things to keep in mind......

It sounds like you have essentially zero experience with solar power. This is not a big deal because everyone starts at zero. I would recommend doing a lot of reading and get smart enough to be dangerous. It's not rocket science but you want to be safe & not ruin expensive equipment. Here's a good start: https://www.homepower.com/solar-electricity

Something to consider since it seems that you wanted to go battery free, most systems use a charge controller to charge batteries & distribute power. Many charge controllers do not work if they don't detect a battery. That's really good to know before you set up on the Playa.

Things go wrong, charge controllers burn up, if it can break it will. Have a back-up plan. The bilge pump that token posted a pic of is actually a good idea. Consider having some spare components. I always have a spare charge controller.

Once you get everything built test it at home to make sure it works.

I think you can do this with a small bilge pump and may or may not need a battery.

Running a fridge is a different matter. I honestly don't think it's worth building a solar power system that is capable of powering a fridge. Consider an using an RV fridge (maybe LP) or just use good old fashioned ice & coolers. When you start powering big appliances like a fridge you will obviously need to incorporate deep cycle batteries. Those batteries weigh 60-80 pounds & usually cost over $100. Typically you will need more than 1 battery. So, as you can see, when you start increasing your requirements you will need to go "all in" & get smart about Solar power, purchase expensive equipment, & haul all that heavy equipment out to the Playa. People do it but only you can decide if it's worth the effort & expense when a big cooler & ice can accomplish the same thing.

If all your doing is running lights, charging phones, & pumping gray water then yeah, that's easy.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by Token » Wed Mar 14, 2018 5:36 pm

BTW, here is the requested equation:

E=mc2

Unless you’re a black hole that is.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by FlyingMonkey » Thu Mar 15, 2018 7:58 am

Token wrote:BTW, here is the requested equation:

E=mc2

Unless you’re a black hole that is.
And that's exactly the kind of thing a Burner (Old school non-Frat Boy or tourist) would do. Make a small nuclear reactor to pump grey water. :mrgreen:

However, I think Ohm's Law would be more appropriate in this case. But I'm not opposed to someone splitting a few atoms on Playa as long as it's quiet & not moopy.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by FlyingMonkey » Thu Mar 15, 2018 8:10 am

And there is this.

https://www.theplayalabs.com/home/labs/solar-home

That'l pump yer sump.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by some seeing eye » Thu Mar 15, 2018 9:07 am

A search of ePlaya for Ah Wh Watts produces

viewtopic.php?f=277&t=81177&p=1138388&h ... s#p1138388

and

viewtopic.php?f=278&t=80397&p=1137228&h ... s#p1137228.

Most cities will have solar hobbyists and maker spaces. Visit the Alternative Energy Zone (village) the year in advance of your need.

A current new solar panel at $1 a Watt, charge controller, deep cycle battery and inverter have use around the house for power outages and disasters. They are a better investment than Harbor Freight, G**l Zero play systems or janky CL panels priced above $.10/Watt.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Luigi » Thu Mar 15, 2018 11:53 am

Hi Clay

Sounds like you need:
12 volt bilge pump with a float switch (so it only turns on when the float says it is needed)
Deep cycle 12 volt battery
Charge controller (to avoid over charge of battery)
Solar panel

The key to your question is the size of your pump and how long it will run (how many gallons will be pumped)

When you have that key, the rest is math.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by BBadger » Sat Mar 17, 2018 10:35 pm

Claybcook,

It looks like you have all the component specifications listed in terms of rates and capacities. The equations essentially fall out by themselves with only a few additional other unit conversion formulas, and maybe additional margins and factors to keep things safe.

The fundamental equation here, as with all equations, is:

Inputs = Outputs

You'll be working in terms of energy. Power (Watts) = Volts * Amps; Energy (Joules) = Watts * Time

- Battery specifications: Energy capacity = Volts * Amp*Hours ; (only discharge to 50% so use only half the rating)
- Solar Panel: Output power = volts * current generation = watts; energy production = power * time
- Load (like a refrigerator): input power = watts; energy consumption = watts * time

You will have two phases: day-time and night-time. These affect whether something, such as a battery, is a sink (output) or a source (input). It'll also affect whether sources such as solar panels produce anything at all.

Day:

inputs = solar_panel(W/panel) * solar_radiation(kWh / day / 1kW/panel)
outputs = battery(0.5 * volts * amps * hours) + load(W) * day_time(seconds)

Night:

inputs = battery
outputs = load(W) * night_time(seconds)

Solve for battery capacity and solar panel rating using the two equations.

The factor of 0.5 on battery is so you only have 50% discharge.

You can easily figure out battery capacity, and then plug the rest into your equations. Solar radiation is like 4.3kWh/day/kW/panel in Nevada under perfectly ideal conditions. Then add margins, etc. so you don't burn out your stuff, can deal with inefficiencies, and can compensate for problems such as lack of strong sunlight, bad panel angle, etc.

Token already went through this process, just without the explicit equations.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Jeannie Ginx » Fri Jun 26, 2020 1:49 pm

I'm just posting a "hi there" so I can find this thread later.

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Re: Sizing a Solar set up to meet the demand of a device?

Post by XPTom » Sat Jun 27, 2020 9:54 am

My old 100W panel in the Black Rock sun maxed out just under 6 amps. My newer 160W panel gives me 9ish amps. In theory a 50W panel should give you the 2.5+ you think your small pump needs....

----BUT #1---

motors on pumps and refrig draw more than advertised on startup. You'll need a battery for starting surge or go big on the panels like Token said.

----BUT #2-----

Modern charge controllers should be hooked up to a battery and not simply used by themselves as power supplies. “12 volt” panels are more than 12 volts. Bargain basement PWM controller (Pulse Wave Modulation) will send a pulse of higher panel voltage to the battery and then a shorter pulse of zero to give the “12 v” battery (really 12.9) an average of 13++ volts. The battery needs to be there to smooth out the peaks and valleys.

More expensive MPPT controllers will take the 9A/17V out of my 160W panel and send 12A/13+V to the battery. Much more efficient but they also need to be connected to a battery for that magic to work.

If you're talking about a small .02hp pump the battery under your hood can be that battery. Just hook up the pump and panel to it. For a small fridge you need to to think multiple panels and batteries.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Jeannie Ginx » Sun Jul 05, 2020 11:07 am

Hey smart electronics burner. Lets see if my rudamentary electronics skills got this right.

I want to get a 100Watt solor panel with a compatible power station.

So say during the day and factor in non peak sun we should get about 80watts/hour on average from the panel

The watt for your devises is the voltsXamps. So say my arctic air mini swamp cooler is 5Vx1.5amps is 7.5 watts

ok lets add up everything my fragile soul needs

I want to run:
2 arctic airs in my 2 man dome tent= 15 watts
(For my 2 bucket swamp coolers and an extra fan for air circ in the monkey hut)
2 pumps = 7.2 watts
3 fans = 45 watts
that equals 67.2 watts per hour? So my panel should be able to run this no problem?

When it gets dark I have a small light with say a 40 watt bulb. My power station should be able to take the extra load from the panel during the day and run my small light at night? I'm considering the extra $20 and get the solar controller box as well.

For shits and giggles I'll probably get to the playa with a fully charged or partially charged power station for the first day/night.

Am I missing a piece of the puzzel or did I get this correct? Be gentle I haven't calculated electronics in years.
Thanks in advance

Loves
j

PS I'm considering renting a onewheel for the event for quick travel across BRC might bring an extra panel just to charge up the onewheel.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Popeye » Sun Jul 05, 2020 3:06 pm

Your math is ok but you are missing two things. First the ampacity of the power supply, I'm pretty sure that if you are using a 5 volt power supply you are using a USB connector. At 5V your draw is 13.4Amps which is way more than can be supplied. Power supplies are designed to supply 80% of rated power after 3 hours. They will usually supply more than that but... Second, your PV panels are RATED to supply 100 watts not guaranteed to supply that. Dust, clouds, etc. will reduce the 100W to whatever.

Are your panels producing 5V or 12V?
As a general statement a USB power supply will not produce enough power (watts) to keep anything cool. These personal coolers are the rip off of the month. They sound a lot better than they are.
My advice? Build a Figjam evaporative cooler/ Bucket Cooler. There is a long thread on here with detailed instructions and much praise. They work! and are fun and interesting to build. Buy a 12V deep cycle battery and a 100W 12V panel to keep it charged.

Good luck and keep asking questions.

Jeannie Ginx wrote:
Sun Jul 05, 2020 11:07 am
Hey smart electronics burner. Lets see if my rudamentary electronics skills got this right.

I want to get a 100Watt solor panel with a compatible power station.

So say during the day and factor in non peak sun we should get about 80watts/hour on average from the panel

The watt for your devises is the voltsXamps. So say my arctic air mini swamp cooler is 5Vx1.5amps is 7.5 watts

ok lets add up everything my fragile soul needs

I want to run:
2 arctic airs in my 2 man dome tent= 15 watts
(For my 2 bucket swamp coolers and an extra fan for air circ in the monkey hut)
2 pumps = 7.2 watts
3 fans = 45 watts
that equals 67.2 watts per hour? So my panel should be able to run this no problem?

When it gets dark I have a small light with say a 40 watt bulb. My power station should be able to take the extra load from the panel during the day and run my small light at night? I'm considering the extra $20 and get the solar controller box as well.

For shits and giggles I'll probably get to the playa with a fully charged or partially charged power station for the first day/night.

Am I missing a piece of the puzzel or did I get this correct? Be gentle I haven't calculated electronics in years.
Thanks in advance

Loves
j

PS I'm considering renting a onewheel for the event for quick travel across BRC might bring an extra panel just to charge up the onewheel.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Popeye » Sun Jul 05, 2020 3:12 pm

"PS I'm considering renting a onewheel for the event for quick travel across BRC might bring an extra panel just to charge up the onewheel. "

Check what voltage is needed to charge the one wheel. It may come with a 120V AC charger which you will need a generator or an inverter for.

There was concern after last years Burn about all the electric bikes and onewheels, etc. speeding across the playa. I'd wait to see how the rules change beforfe laying out any money.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by XPTom » Mon Jul 06, 2020 1:20 pm

[quote="Jeannie Ginx" post_id=1202330 time=1593972452
that equals 67.2 watts per hour? So my panel should be able to run this no problem?
[/quote]

In the ballpark with your 80W guesstimate, but cutting it close. . If the solar station you're thinking of uses PWM controller figure closer to 70W usable output. If MPPT figure on 90W+ from a 100W panel.

If you trouble yourself to point the panel toward sunrise before sleeping you can get 5.9A peak output 30 min after sunrise. Adjust it 2-3 times a day and you can get 13+ peak hours per day.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Jeannie Ginx » Tue Jul 07, 2020 8:59 am

considering a second panel. Do you guys perfer to set up in parallel or series?

I'm going to use a rockpals power station. So I can't decide if the volts or the amps is the most important thing to keep.

Paralell increased amps and same volts
series increased volts and same amps

So many decisions before I purchase. I might mess with both options and see what happens.

got to love Ohm's law
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Jeannie Ginx » Tue Jul 07, 2020 9:06 am

XPTom wrote:
Mon Jul 06, 2020 1:20 pm
[quote="Jeannie Ginx" post_id=1202330 time=1593972452
that equals 67.2 watts per hour? So my panel should be able to run this no problem?
If you trouble yourself to point the panel toward sunrise before sleeping you can get 5.9A peak output 30 min after sunrise. Adjust it 2-3 times a day and you can get 13+ peak hours per day.
[/quote]
XPTom, I'm going to put up a monkey hut with the sides facine east/west with the openings at north/south. My plan now is 2 100Watt panels towart the top apex of the hut and drap one on the east side and one on the west side. I figured that config would be the most peak sun during the day I can get. I just need to figure out a way to get them slightly tilted south at 40degrees (since Gerlach is at lat 40)
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Re: Sizing a Solar set up to meet the demand of a device?

Post by motskyroonmatick » Tue Jul 07, 2020 9:37 pm

If it is a MPPT charger it won't matter a huge amount but if the charger on the power bank is PWM then it is most important for the solar panel voltage to be matched to the battery bank. I would stick with panels that closely resemble what the manufacturer of the power pack recommends.

I recommend putting your solar panels on the ground in a panel frame you can rotate around to meet the sun. It's easier to anchor them to secure from wind and monkey huts aren't really that structural. It may take quite a bit of beefing up the top of the monkey hut to make it a good mount that can survive the wind load

Personally I am a bit overboard on trying to prepare my camp for wind. I actually try to have nothing that I have to change if a big wind comes. I might be out of camp when the big wind comes and it would be horrible to come back to structural failureville. The solar panels on top of monkey hut worries me a little. It's a tougher place to get to once everything is set up if there was a problem. I could see it working if the panels are not too large and extra ribs were added to the monkey hut with the sole purpose of supporting the panels.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by XPTom » Wed Jul 08, 2020 9:22 am

Panel Tilt 40.78 degrees from level would be perfect for BRC at high noon on equinox. 31 degrees for the last week of August, but erring toward 40-45 is just fine. More tilt gathers less dust and that extra 10-15 degrees won't cost you one drop of electricity. .

Series vs Parallel When my local RV guy adds a panel for a customer he wires two identical panels in series to a MPPT controller.. It is the best way to get the most watts from the roof to the battery with the least cable loss. If your plan is to point the panels in different direction to maximize solar day you will find a simple series system is as strong as its weakest link. You do have time to study bypass diodes..... or not. Turning the panel isn't rocket surgery.
OR.... Just point both panels south.(why didn't I think of that sooner?) Early and late output will suffer but you'll get the equivalent of a 9 hour solar day. I travel light and try to keep my footprint small so I try to get a 13 hour day out of one panel. 2 panels for 9 hours beats my one panel for 13 hour plan, and it is less work.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Jeannie Ginx » Wed Jul 08, 2020 1:33 pm

XPTom wrote:
Wed Jul 08, 2020 9:22 am
Panel Tilt 40.78 degrees from level would be perfect for BRC at high noon on equinox. 31 degrees for the last week of August, but erring toward 40-45 is just fine. More tilt gathers less dust and that extra 10-15 degrees won't cost you one drop of electricity. .
the panels I'm considering are the fold up kind that are on a thick canvas material with gromets. Not the standard stiff ones. So I will have to mess with this set up a lot before I make it to the playa. Also I probably wont want to be at my camp all the time to re-position them so I need to come up with a happy medium.
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Re: Sizing a Solar set up to meet the demand of a device?

Post by Popeye » Thu Jul 09, 2020 4:37 pm

Check the ampacity of the panels and the wiring as well as the blocking diodes before putting the panels in series.
With panels in series all current runs through all panels and if the wire, diodes etc. will not handle that amount of current it will burn up.
Literature from panel maufacturers (that I have seen) will tell you how many panels can be tied in series.
“Tell me, what is it you plan to do / with your one wild and precious life?” Mary Oliver

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