solar panel in cloudy weather

Thread Starter

Fanfire174

Joined Mar 13, 2018
240
I want to use a solar panel for home equipment. I located in india We know that solar panel is directly dependent on sunlight. Solar panels produce much electricity in sunny days. They don't produce much electricity on cloudy weather. solar will not useful in cloudy day. Is there a solution to this problem?
 

MrAl

Joined Jun 17, 2014
8,479
I want to use a solar panel for home equipment. I located in india We know that solar panel is directly dependent on sunlight. Solar panels produce much electricity in sunny days. They don't produce much electricity on cloudy weather. solar will not useful in cloudy day. Is there a solution to this problem?
Use about 4 to 10 times as many solar panels than you would need in direct sunlight.
 

AlbertHall

Joined Jun 4, 2014
11,506
They produce a lot more than I was expecting. The system on my roof produces a maximum 3.6kW, full sun, midsummer, midday. Today, middle of the afternoon, spring, cloudy day, they are producing 700W.
 

Janis59

Joined Aug 21, 2017
1,350
Latvian climate (57 latitude) gives 40-60 W/m2 at cloudy days and 250-350 W/m2 at sunny days. Multiply with panel efficiency, what may be between 15% for bad and 45% for state-of-the-art.
 

MisterBill2

Joined Jan 23, 2018
9,304
The nature of solar panels is that they deliver power proportional to the sunlight that falls on them. That is a basic reality. Even the utilities with many resources are limited by that. And at night the only choice is either power stored in a battery system or an alternate generation means. So the simple solution, possibly, is a lot more battery capacity to have for cloudy days.
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
240
solar panels charge the storage battery and the battery supplies electricity to the home devices. But does the battery never get damaged if it is over-charged?
 

KeithWalker

Joined Jul 10, 2017
1,919
No, if you don’t overcharge them.
If well maintained, the batteries have a life of about 10 years, then they will need replacing. Have you considered using a wind powered generator as well as solar panels? They will supplement each other and you will need less batteries for storage.
Keith
 

MisterBill2

Joined Jan 23, 2018
9,304
solar panels charge the storage battery and the battery supplies electricity to the home devices. But does the battery never get damaged if it is over-charged?
The prevention of an overcharge is the main purpose of the charge controller device that is normally installed on all solar power systems. It is quite important for that device to function correctly. Certainly over charging batteries will damage them. If your system does not have a charge controller then it is incomplete.
And how did the subject suddenly become overcharging when it was about getting an adequate charge on a cloudy day????
 

Thread Starter

Fanfire174

Joined Mar 13, 2018
240
And how did the subject suddenly become overcharging when it was about getting an adequate charge on a cloudy day????
answer is a lot more battery capacity to have for cloudy days. I think this is best way

If your system does not have a charge controller then it is incomplete.
I am planning to develop solar panel at my home The four major components of a solar energy system are the panels, inverter(s), racking and solar battery storage. Would It be better to develop the solar panel its own or I should consult a company. If it is not very difficult to make, then I would like to make a one solar panel system for home appliance . I have background in electronics and embedded domain.
 

nsaspook

Joined Aug 27, 2009
8,686
It's usually better to over panel by some X factor than to have over battery capacity that must be refilled with energy from some other source during extended days of low production. Some battery chemistries behave better in extended lower SOC conditions but as a rule, storage, usage patterns should be matched with higher levels of generation to refill batteries quickly, with excess production on sunny days going to opportunity loads.

This is a three day chart of increasing sun. As you can see the panel voltage levels (blue) are similar into to the MPPT Charge Controller but the battery charge current/power levels (green) dramatically change as cloud cover dissipates.

 

MisterBill2

Joined Jan 23, 2018
9,304
answer is a lot more battery capacity to have for cloudy days. I think this is best way


I am planning to develop solar panel at my home The four major components of a solar energy system are the panels, inverter(s), racking and solar battery storage. Would It be better to develop the solar panel its own or I should consult a company. If it is not very difficult to make, then I would like to make a one solar panel system for home appliance . I have background in electronics and embedded domain.
Unfortunately I see no mention of a charge controller. You do need a charge controller if the system will be charging batteries. ALL battery chemistry types need to have a charge controller because they are all subject to damage from over charging. Excess power generated during the day can be used to pump water up to the cistern on the roof.
 

MrChips

Joined Oct 2, 2009
24,233
Why not have your batteries charge on a rotating basis?
When one battery is fully charged, switch over to the next battery, cloudy or sunny day.
This way you will always have some batteries fully charged rather all batteries with partial charge.
 

MisterBill2

Joined Jan 23, 2018
9,304
Why not have your batteries charge on a rotating basis?
When one battery is fully charged, switch over to the next battery, cloudy or sunny day.
This way you will always have some batteries fully charged rather all batteries with partial charge.
Charging a separate set of battery would certainly be within what a charge controller would do.
 

nsaspook

Joined Aug 27, 2009
8,686
Why not have your batteries charge on a rotating basis?
When one battery is fully charged, switch over to the next battery, cloudy or sunny day.
This way you will always have some batteries fully charged rather all batteries with partial charge.
I have already researched, designed and built a system 10 years ago that does just that.

https://forum.allaboutcircuits.com/threads/project-solar-wind-pic-controlled-battery-array.32879/
This is a system to keep up to 4 isolated batteries charged from a single solar/wind power generator. It's using aPIC18F8722 Microcontroller from http://www.futurlec.com/PIC18F8722_Controller.shtml as the controller with software written in C18 from Microchip. Most of the parts came from junk from old equipment at work but I need to buy a full array of solar to make it useful.

The plan is to monitor the batteries and have it select the best one to charge and to alert via RS-232 link any abnormal conditions.
It's a zero sum game of energy in and energy out. Just like the 2nd law, You Can't Win.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
9,304
I have already researched, designed and built a system 10 years ago that does just that.

https://forum.allaboutcircuits.com/threads/project-solar-wind-pic-controlled-battery-array.32879/

It's a zero sum game of energy in and energy out. Just like the 2nd law, You Can't Win.
That function certainly sounds like part of a charge controller system. Perhaps you can share additional insights with the TS. I am aware and familiar with what a charge controller must do, but have never needed to design or create one.
 

MrChips

Joined Oct 2, 2009
24,233
At this point TS is concerned about overcharging the batteries. That is a valid concern.
He needs to stop charging when the batteries are fully charged.
 

nsaspook

Joined Aug 27, 2009
8,686
That function certainly sounds like part of a charge controller system. Perhaps you can share additional insights with the TS. I am aware and familiar with what a charge controller must do, but have never needed to design or create one.
Sure, he needs a Charge Controller to properly recharge a energy bank but that's just one function of a proper multi-battery BMS. When that bank is partitioned to optimize every watt the management (BMS) of resources calculations start to get complicated. This is also important with lead acid battery banks of series cells to increase bank voltage to at least 24vdc for efficient energy transportation, storage and transformation into AC utility voltages.

Li-Ion/Li-Po BMS example:


A prototype version of my current BMS I use for software development (notice the huge values on the LCD) for the operational system with 300W of panel and a 24vdc battery bank.

My primary insight is that adding batteries without the additional X days panel capacity to recharge your bank in one day is a recipe for battery murder with typical RE daily power usage cycles.
Example: 100Wh of battery usage per day needs at least 200Wh of panel for a realistic cloudy day reserve capability. People seriously underestimate what's needed for usable off-grid solar power. It's an expensive solution more suited to the real needs of a remote location than a way to conserve energy and money.
 
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