Simple and direct setup. Will it work?

[Desert sun]

Hello,

So I was in the solar panel section at the market the other day, and I came across an evaporative cooler (swap/desert cooler) that runs on 12v DC.

Very much similar to this one (https://www.alibaba.com/product-deta...838.0.0.ZIyC0v)

But the specs on the one that I found were :
Rated Voltage: DC 12V
Power: 100W
Airflow 2500m3/h
Rated Current,Max: 12A
Water Tank Capacity: 20L

The seller told that he will give me a special price if I buy it with the following:
1) 150w 12v solar panel
2) 100 amp battery ( as he put it "gel battery not car battery")
3) Charge controller

After her did some calculations, he promised me that the unit will run at least 12h a day. And if I want it to run 24h I should get another battery. But what I had in mind was totally different.

My plan is to wire the panel directly to the unit, and whenever the sun is out, the cooling starts. After hearing my plan, he assured me that it will never work, and that I will end up buying the

battery and the charge controller anyway.

My question is: can I run the unit without the battery and the charge control, and only have it run when the sun is up?
for example: Solar panel --------> unit. (direct setup, nothing in between)

Will a 150w 12v panel suffice, or should I get another one and wire them in parallel?

If i get a 250w 18v panel, will the 6 extra volts damage the motor?


PS: This is not the main cooling method for the space.

Kind regards.

[NEOH]

What you don't understand is ... the Voltage and the Current will change with the load, the sun and the temperature.
http://www.samlexsolar.com/learning-...teristics.aspx

There is only one combination of Volts and Amps from the PV Panel that results in Max Power.
An MPPT (not PWM) Charge Controller tries to operate the PV Panel at Max Power, regardless of Load.
The battery is the "constant voltage buffer" between the Load and the Charge Controller.
This makes your life "easy".

To run a load directly from a PV Panel ...
You need to know the specifications like: Imp, Vmp, Isc & Voc to know if can run a load directly.
You need to need verify that the Open Circuit Volts is never too high.
You need to verify that you never draw too many amps > Imp, which will then drop your voltage below Vmp.
Direct "can work", if Vmp and Imp ( varies with insolation & heat ) can support the load.
Is there any surge from load, on startup?

It is hard to say if 18 Volts will damage your fan motor and pump, or not.

[SunEagle]

I concur with NEOH. Unless the load has the ability to run at different currents, voltages and speeds you will need a battery.

Since I am not familiar with that "cooler" I can't tell if it will work directly powered by a pv panel. More than likely it will not work correctly and you will end up hurting it.

Another thing to think about. It may still be hot and you may still need some type of cooling even if the sun isn't out. That is when another power source (like the battery) becomes necessary.

What even you decide to do, you will need to match the battery Ah rating to the charging amps from your solar panel. Quick rule of thumb would be charging amps equals 1/10 the battery Ah rating. So that 150 watt panel is marginal matched with a 100Ah battery since it may only produce ~ 8.5 amps at best for charging which is barely enough.

[Wy_White_Wolf]

The guy is a snake oil salesman.

1. The unit uses 12A so in 12 hours that's 144AH or 44% more than he suggested in battery. Way too undersized.

2. You do not want a gel battery. You want a deep cycle battery.

3. 150W panel will not produce enough power daily to run it for 12 hours. 144AH * 12v = 1728watts. Being summer you might have 6 hours insolation daily so the panel may produce 900WH (150*6). But that is unlikely as in the summer heat panels will not produce full power. He also never calculated in any inefficiencies into the design.

By my calculation you want at least a 600w array and 600AH battery with an MPPT controller to possibly run for 12 hours.

WWW

[PNPmacnab]

Your concept is somewhat correct. There is a device that runs remote DC pumps without a battery called a Linear Current Booster. These work well on brushed DC motors. The solar panels operate at power point and provide as much current as possible to the motor at lower voltage. A 150W panel is way undersized and expensive, a 280W grid tie panels are cheaper with higher voltages. Batteries are always problematic and raise system cost Linear current boosters are in the $200 and higher range. Whatever control system this cooler has probably won't work with it. In my PV system I have automated controls that only operate things when the sun is out and there is enough power. Evaporative coolers are fairly simple and slowing the motor down with low sun ought to work. Cooling only when there is sun is a practical idea that should be used more. I can easily mostly equipment to do this, but equipment .is just not available for the general non technical public. So you need to go with a bigger dumb battery system.

[J.P.M.]

PS: This is not the main cooling method for the space.

In that regard, if the main cooling means is conventional A/C, know that if a swamp cooler is run inside the same conditioned space with conventional refrigeration type A/C equipment, the conventional equipment will need to work harder (actually less efficiently and/or longer ) due to the additional latent (condensing) heat load added by the swamp cooler. Overall, running both in parallel wastes energy. The swamp cooler adds moisture to the conditioned space. The A/C has to work harder to remove the moisture the swamp cooler adds.

[Sunking]

Perhaps this is what you need to know. Anything you take off grid is going to cost you 5 to 10 times more than buying power from the POCO.

So the question becomes; If you have commercial power, why would would you want to pay 5 to 10 times more for power? It is not the solar panels although they do figure into the cost, but it is the never ending replacing batteries.

I agree with WWW, whoever you spoke with is smoking dope and trying to hook you. It will take a lot more than he told you. He just wants to make the initial sale because he know later you will have to come back and buy a lot more equipment. Plus new batteries every few years. He is looking for a pigeon to pluck. Are you his millennial snowflake pigeon?

[Desert sun]

Thank you all for your answers and advises. I am overjoyed to see very well known names directing me in this ever growing field.

I have learned a lot from you all, but I still have more questions so things get more clearer.

NEOH: The link is very informative. I thank you.
But is it necessary to know the Voc since the circuit will never break. It's never an open circuit.
Also the amount of loads is constant. The fan never stops as well as the pump.

SunEagle: I first got this idea from a guy who claims that he did exactly that. That he connected his loads directly in an identical project.
Heres the youtube link : https://www.youtube.com/watch?v=2Fpa...ature=youtu.be
I believe, actually, hoping that the load can in fact run on different currents, voltage, and speeds as long as it doesn't exceed 12v... I think
I have to consult an electrician and check it DC motors that are rated 12v can handle voltage up to 14 or so.

Wy_White_Wolf: Thank you for double checking his calculations. I blindly believed him.
And, just to make sure, by deep cycle battery, you don't mean the ones that use battery water, correct?

PNPmacnab: Exactly what I was thinking, having low sun light will only reduce the speed of the fan.
But I fear the unsteady flow of current and voltage might fry the motor. Mainly the high spikes of voltage.
Im going to read more about the Linear Current Booster and hopefully come up with a more simple solution than the "big dumb battery system"

J.P.M.: hello JPM, that's a very good point. The added latent heat will reduce the AC's efficiency, but Im in a typical desert climate. The air is very dry here, and I'm
willing to trade some COP points for a little humidity.
And may I ask why running two panels in parallel is a waste of energy? wouldn't this double the amount of Watts but the Voltage stays the same?

Sunking: hello Sunking, it is sad that renewable energy still cost 5 - 10 more than buying it from the city. And I truly believed that by having a direct setup,
I can even out the costs.
I started this project hoping that I could utilize this wasted energy and convert it to cool air. Since I live near the Empty Quarter
the air is very dry and hot. Using the sun's energy to humidify and cool the air, even if a little bit, will be an astonishing achievement.


Kind regards,
Desert sun

[Desert sun]

I just wrote a lengthy replay, but when I posted it, it just disappeared.
This one, for the sake of the time, will be shorter and less organized. My apologies.

NEOH : The link is very informative. I thank you. the
Is it important to know the Voc if the circuit will never break? Its never open.
And the amount of loads is constant. The fan is always on as well as the pump. resistance never changes.

SunEagle: I have to consult an electrician if the motor can run different currents, votage ,and speeds, but I believe it can
This guy did exactly that, he wirethe PV panel directly to the loads in an identical project:

https://www.youtube.com/watch?v=2FpaSKazhNY&feature=youtu.be

WWW: I greatly appreciate you double checking his calculations. I blindly believed him.
And was very close to buying it. Thank you.

PNPmacnab: I will read more about the Linear Current Booster and hopefully will find a simple solution
not a "big dumb battery system"

JPM: Thats a very good point. The added latent head will reduce the AC's efficiency. But I live in a typical desert climate
and will gladly trade COP points for some humidity.
My question is why running both panels in parallel is a waste of energy? wouldn't it only doubles the watts?

Sunking: I live near the Empty Quarter and the air is very dry and hot. If I can use the suns energy to provide humid cool air, even if a little, it will be an astonishing accomplishment.

[J.P.M.]

JPM: Thats a very good point. The added latent head will reduce the AC's efficiency. But I live in a typical desert climate
and will gladly trade COP points for some humidity.
My question is why running both panels in parallel is a waste of energy? wouldn't it only doubles the watts?

I lived in a very dry desert climate for a few years w/a swamp cooler. FWIW, I found the swamp cooler performance marginally acceptable.
For your case, not only will the evap. cooler add to the latent A/C load, if it (the swamp cooler) works the way most such devices work, it will need an open or cracked window to exhaust the air it draws. That exchanged air replacement volume will also need to be cooled, further adding to the cooling load, as well as dehumidified by virtue of being cooled below its dew point by the A/c unit, thus removing most of the moisture added by the swamp cooler. An exercise in futility.

A respectful suggestion: Do what you want, but do yourself a favor and forget the swamp cooler and the crap PV system that is being pitched with it. First off, what you were being pitched is a steaming pile of road apples. Second, running an evaporative cooler and a vapor compression A/C unit in the same space and at the same time is a waste of energy, making about as much sense as operating a dehumidifier and an evaporative cooler at the same time in the same area. You want some humidification ? --->>> Use a humidifier set at a dew point a few deg. (5 to 10 deg. F. maybe) above the outlet temp. of the A/C unit.

To your question: When I was writing about "parallel", I was referring to operating a std. air conditioner and a swamp cooler to condition the same space at the same time. I was not referring to a solar panel arrangement to produce electricity. FWIW, I'd scrap that idea altogether.

[SunEagle]

I just wrote a lengthy replay, but when I posted it, it just disappeared.
This one, for the sake of the time, will be shorter and less organized. My apologies.


SunEagle: I have to consult an electrician if the motor can run different currents, votage ,and speeds, but I believe it can
This guy did exactly that, he wirethe PV panel directly to the loads in an identical project:

https://www.youtube.com/watch?v=2FpaSKazhNY&feature=youtu.be

I have seen other videos showing a pv panel connected directly to the load with mixed results. Sometimes it works and sometimes it hurts the equipment.

I own a couple of vent fans that are really small DC motors that connect directly to a 10W solar panel. These motors were designed to run at different speeds depending on the amount of sunlight hitting the solar panel.

That "cooler" may work like the one in the video but I wanted to warn you that sometimes what you see on the internet is not always reality.

Oh and the reason your first post did not go through was because of the weblinks. It went to Review for a Moderator which I did and then approved it.

[PNPmacnab]

Nothing works as good as you think and as bad as you imagine. I saw those coolers all over San Antonio. Even just a shade tree provides some relief. I'm disappointed in the cost Of linear current boosters. With slight modification these are nothing more than a $20 buck converter or speed control. Liked the radiator fan, these will accept a variety of voltages. Truth be told, in a hot climate and just a little lead loss, that panel will barely produce much over 15V. If you are willing to operate it manually and do some experimentation, you can buy a $10 "20A DC 12V/ 24V/ 36V/ 48V Motor Speed Control" on ebay and ten 1,000uF 50V capacitors. The capacitors are placed in parallel on the input of the board provide storage for a po boy MPPT controller. Setting it at just 75% speed will prevent over voltage and some current boost at lower light levels. You could adjust it manually three times a day for maximum speed.

I'm laying out a board right now for a multi micro power board for these applications that don't fit standard products. With a little automation, the motor can operate in linear current boost mode in the day, charge the battery, run at night for 10 minutes every 30 minutes till the battery reaches a state of discharge. I run a whole house on a single car battery and even get hot water. This year I will be adding a dishwasher! Of course you have to make little adjustments in life. What did we learn from the VCR flashing 12:00? Even minor technology is beyond the general public.

[Wy_White_Wolf]

....Wy_White_Wolf: Thank you for double checking his calculations. I blindly believed him.
And, just to make sure, by deep cycle battery, you don't mean the ones that use battery water, correct?....

No.

Gel refers to type of electrolyte in a battery. Deep-cycle refers to the intended use the battery is designed to serve.

Basic types of electrolyte for lead acid batteries are Flooded, AGM, and Gel. Flooded (FLA) can be both open cell (the ones to add water too) and sealed (SLA) or valve regulated. Generally FLA are a better cost per KWH than others. Actually the others should not be used in a solar system unless you have specific reason requiring them such as need to mount on the side or operating under extremely cold temperatures. Gel batteries are seldom used in solar systems as they have the lowest charge rates.

Basic designed usages are starting, deep cycle, and float. Your car uses a starting battery. Designed to put out a large current for a short time then be immediately recharged. Something that is to be cycled on a regular interval would be deep cycle. Something that is designed to sit the for long periods of time to cover emergency power would be float. These would be UPS batteries and telecom batteries.

WWW