Solar Air Conditioning Without Batteries

[fw12]

Is it a crazy idea to think of running Air conditioner (AC) on solar panels and inverter without batteries?

Let's say a 1.5hp AC unit, which equals 1.1kW.
If one throws 6x 300W panels at it, at 80% efficiency, that would produce 1.44kW

Voltage sag from cloud cover...
A DC-to-DC converter may help keep the solar panel voltage constant through out the day.
This one promises: 1,800W 40A, 10V-60V input to 12V-90V output

https://www.aliexpress.com/item/32857772579.html

Inverter:
A 2kW Inverter

The big question is the AC's start up power.
For that, I was thinking to get a super capacitor.
Would something like this serve? https://www.walmart.com/ip/Farad-Cap...tion/525590085

So the no-battery setup would look like this

Solar panels --> Dc-to-DC converter --> Inverter + Super capacitor --> Air conditioner

The initial cost would be high of course. But it should last long enough, without one paying any electricity charges.
Also, the setup can also serve to run other high power tools around, one at a time.

[Mike90250]

a) yes

You forgot to factor system losses, which by my estimation would require about 3kw of panels & inverter and a minimal 48V battery bank of 200ah. There are large surges that a super cap from wallmart cannot deal with, a real battery is needed. And the system would only stay working in full bright sun, hazy or cloudy weather would impact the solar harvest. Batteries will carry it for a couple minutes but that's all

Opinions will vary, some may agree with you.

[bcroe]

There already exist Heat Pumps (air conditioners) that may be directly powered from
solar panels. So there is no need for all those wasteful intermediate steps. The newest
generation of HPs run off DC internally, which is inverted to drive variable speed AC
pumps and fans. Some adapt that to a solar connection. Typically they have an AC
line input to back up a shortage of panel power. The start surge problem goes away.

A constant DC to DC conversion does not solve the main problem, which is developing
an adequate source of POWER to do the job. Converters/inverters cannot do that. A
lot of extra panels can help.
Bruce Roe

[fw12]

>>>A constant DC to DC conversion does not solve the main problem, which is developing an adequate source of POWER to do the job
I get your point. I still think a running super capacitor can take care of momentary spikes. That is what they're for.

>>>There are large surges that a super cap from wallmart cannot deal with, a real battery is needed
Again, large surges that last a few seconds shouldn't be a problem for a capable supercap.

>>>There already exist Heat Pumps (air conditioners) that may be directly powered from solar panels
I'll research that too. If the cost is justified, that is definitely the way to go.

It would be nice to experiment with this concept and see how it works out. Unfortunately for me, I live in condo community. No solar panels allowed. All that Las Vegas sun is wasted for me.

[bob-n]

I found some information on solar air conditioners here:

https://www.greenbuildermedia.com/energy-solutions/pros-and-cons-of-solar-powered-air-conditioners

From a cursory read, these are simply high-efficiency A/Cs coupled to specialized electronics.

Does anyone here have first-hand experience with this kind of unit? Is the A/C any different from a good, conventional home A/C?

Assuming a grid-tied system with no batteries, how would payback on that sort of device compare to payback on a conventional A/C plus conventional solar? I would think that conventional solar would have an advantage because it can generate revenue even when there is no need for A/C, but the combined system only works for you on hot days.

[Ampster]

The ones i have read about are run by variable freguency inverters. The compresor motors are driven by those inverters. The startup current is very very low and the output varies with the solar production. I do not see the advantage over a grid tie system supporting a similar variable speed compressor in an efficient minisplit.

[bcroe]

The original question was,

Is it a crazy idea to think of running Air conditioner (AC) on solar panels and inverter without batteries?

My answer, it is available off the shelf, no batteries or other extra equipment required.

Super caps are not just like batteries. To access most of the stored energy, any cap
must be discharged almost completely. Most loads will not be happy with a supply
that has a very rapidly dropping voltage. Batteries tend to hold the V line till mostly
discharged.

My discussion is about the new inverter driven class of HPs. I have experience
running 6 of these, 4 different models, providing heating and cooling for some 5000
sq ft in 2 buildings. This whole class is a HUGE advance over the units from the 70s.
My first house AC unit had a SEER of 8, my most recent HPs use far less energy with
a SEER of 36. The development of micro processor controls and high power FET
transistor inverters makes practical variable speed drive to the fan and compressor
motors. This, along with redesigned fans, allows far quieter operation. The max
power (and max noise) is not often used, most of the time they operate silently while
using just enough power. Heat is pumped more efficiently using much enhanced
freon, compressor cycle, and higher pressure.

Within the class is a huge variety in details. Capacity may start around 9000BTU/hr,
ranging up to many times that. The lowest temperature for effective operation varies
greatly, from well above 0 deg F, to well below 0 deg F. Operation might be from 120
VAC, 240 VAC, PV panels, or some combination. Because they all rectify input power
into a DC bank, the surge of starting simple induction motors is eliminated.

Because these HPs are inherently DC powered, the problem of designing the HP to
use PV solar DC power is simplified. An advantage to this is the HP can operate
without the grid. A disadvantage, is no PV power at night, but most air conditioning
is done peaks days. Typically PV HP units may be wired for grid backup, some can
use a (big) 48V battery. Bruce Roe

[PNPmacnab]

I run a washing machine off panels with no battery and 4 panels. That is a lot less power needed than than an AC unit. It shuts down with a cloud and fortunately it remembers where it was. I suspect you would need at least four times that number of panels to do the same thing. It is a matter of having a smart control system. Problems like this are simple for me. I have a general rule. If someone really needs to ask, they likely can't do it.

[sdold]

This thread is already two years old, but I'd still love to chime in. Running an AC on solar panels and an inverter without batteries can be an interesting idea to explore. If you have a 1.5hp AC unit and throw 6x 300W panels at it, producing 1.44kW at 80% efficiency, it's a good start.

Hi, I have a question for you. I see you joined about 20 or more forums on Tuesday the 13th (a couple of days ago). You then posted a message on most of them in old threads beginning with "I know this thread is a couple of years old..." That seems very strange to me. Are you a legitimate user, or are you getting ready to spam this forum?

[J.P.M.]

Hi, I have a question for you. I see you joined about 20 or more forums on Tuesday the 13th (a couple of days ago). You then posted a message on most of them in old threads beginning with "I know this thread is a couple of years old..." That seems very strange to me. Are you a legitimate user, or are you getting ready to spam this forum?

Nice catch.
Could be a bot, but in any case, probably up to no good.
If no response, I'd dump the user.

[sdold]

This happens more than you might think, but usually it's clear-cut enough to outright ban them. This one wasn't as obvious so I thought I'd give him a chance. The last time I almost banned the poster outright, it turned out to be a legit user, so I need to be careful.

It used to be easy to spot them, but it's getting harder because it looks like they are copying a thread's initial post, pasting it into something like ChatGPT, and posting the result here. You can probably tell which ones they are by the style and certain phrases. For example, here's what I get back when I paste the OP's question:

It is not a crazy idea to consider running an air conditioner (AC) on solar panels and an inverter without batteries, but there are important factors to consider:

1. Power requirements: A 1.5hp AC unit consuming 1.1kW can potentially be powered by six 300W solar panels with 80% efficiency, providing 1.44kW. However, ensure that the panels consistently generate enough power, considering variations in sunlight and panel performance.
2. Voltage regulation: To mitigate voltage sag due to cloud cover or other factors, a DC-to-DC converter can help maintain a constant solar panel voltage throughout the day. The converter you mentioned, with an input of 10V-60V and output of 12V-90V, could potentially be suitable.
3. Inverter selection: Choose an inverter with a capacity higher than the AC unit's peak power demand to handle startup power requirements. A 2kW inverter should be sufficient.
4. AC startup power: AC units often have high startup power demands, which may exceed the capacity of super capacitors. While super capacitors can provide quick bursts of power, they typically have low energy density and may not sustain the startup power needed for the AC unit. It's advisable to carefully assess the specific startup power requirements of your AC unit and consider alternative solutions if necessary.
5. Cost considerations: Implementing this setup can involve significant upfront costs, including solar panels, inverter, DC-to-DC converter, and potential additional components. Evaluate the cost-effectiveness based on your energy consumption and the potential long-term savings from reduced electricity charges.

It's crucial to consult with a professional solar installer or engineer to assess your specific requirements, conduct a feasibility study, and provide appropriate recommendations. They can guide you in selecting the right components and ensure safe and optimal system performance.

Looks almost legitimate, doesn't it?

[J.P.M.]

This happens more than you might think, but usually it's clear-cut enough to outright ban them. This one wasn't as obvious so I thought I'd give him a chance. The last time I almost banned the poster outright, it turned out to be a legit user, so I need to be careful.

It used to be easy to spot them, but it's getting harder because it looks like they are copying a thread's initial post, pasting it into something like ChatGPT, and posting the result here. You can probably tell which ones they are by the style and certain phrases. For example, here's what I get back when I paste the OP's question:

It is not a crazy idea to consider running an air conditioner (AC) on solar panels and an inverter without batteries, but there are important factors to consider:

1. Power requirements: A 1.5hp AC unit consuming 1.1kW can potentially be powered by six 300W solar panels with 80% efficiency, providing 1.44kW. However, ensure that the panels consistently generate enough power, considering variations in sunlight and panel performance.
2. Voltage regulation: To mitigate voltage sag due to cloud cover or other factors, a DC-to-DC converter can help maintain a constant solar panel voltage throughout the day. The converter you mentioned, with an input of 10V-60V and output of 12V-90V, could potentially be suitable.
3. Inverter selection: Choose an inverter with a capacity higher than the AC unit's peak power demand to handle startup power requirements. A 2kW inverter should be sufficient.
4. AC startup power: AC units often have high startup power demands, which may exceed the capacity of super capacitors. While super capacitors can provide quick bursts of power, they typically have low energy density and may not sustain the startup power needed for the AC unit. It's advisable to carefully assess the specific startup power requirements of your AC unit and consider alternative solutions if necessary.
5. Cost considerations: Implementing this setup can involve significant upfront costs, including solar panels, inverter, DC-to-DC converter, and potential additional components. Evaluate the cost-effectiveness based on your energy consumption and the potential long-term savings from reduced electricity charges.

It's crucial to consult with a professional solar installer or engineer to assess your specific requirements, conduct a feasibility study, and provide appropriate recommendations. They can guide you in selecting the right components and ensure safe and optimal system performance.

Looks almost legitimate, doesn't it?

Yea, except for the social irreverence and politically incorrect humor and I often sprinkle in my posts with, I or some other regular posters might have written it.

Come to think of it, and somewhat based on the idea that to err is human, one temporary way and perhaps a tool to help spot such stuff, until the AIs wise up to it anyway, might be to look for political or grammatical incorrectness. Since AI probably won't use much profanity (at least maybe not yet) and will probably be grammatically flawless (at least for now), finding any such stuff in text might be a soft check for a human author.

The future will be interesting.

[GridWorks Green]

Have 120VAC mini-split running just fine on 18 solar PV panels standard 12VDC in 2 series strings of nine 180VDC, directly driven 180VDC Inverter provides 120VAC pure sine out to the mini-split and more, a small amount of grid power converted to DC stableizes the system for passing clouds.

No battery,no super capacitors,no maintenance and it all runs automatic.

Secondary power can be sourced from other than grid.

Will add a link shortly documents on page 22 and new information all the way up to page 27.

https://diysolarforum.com/threads/new-no-battery-pure-sine-wave-solar-power-system-with-smart-switchers.48023/page-22

Mains and capacitor discharge warnings ⚠️

Best wishes

[GridWorks Green]

Big steps forward in the past few days

Zero secondary or grid usage if full sun is available.

Mini-split is providing comfort in the largest 4 rooms of the home daily, no batteries, no battery maintenance/replacement cost.

Runs the Air conditioner and more daily.

Please read: https://diysolarforum.com/threads/ne....48023/page-29

Works better than I ever expected.

[PNPmacnab]

I like to run things with solar and no battery. But, it has been an unusual summer so far with rain and clouds almost every day. And then there is the smoke coming down from Canada. I never imagined it could be so visible at ground level. I've been washing clothes from PV voltage only for three years without issue till this year. I have succumbed to the dark side of solar, the battery people. I now have battery assisted laundry. When the PV array voltage drops slightly below power point voltage, the inverter will turn on and supply only just enough current to make up for the PV loss due to a cloud. Don't worry, it isn't much of a battery. Just a car battery picked up from town recycling with only about 10AH. There are people using this same technique with inverter AC units supplying PV DC to the inverters DC capacitors and adjusting line voltage down slightly with autotransformer to closer match the PV. I was disappointed to finally put a power meter on the washer and find it used less than 100WH to do an entire load. Hard to save any money when a load of wash only costs a couple pennies to do..