Doubts on how a battery feeds household loads ...

[newresearcher]

Hi all,
I'm new to the concept of PV-battery systems and have a basic question on how battery supplies the house consumption while appliances are being used.

Let's consider this scenario that I have a fully-charged battery and going to use high power appliances (like a dryer, dishwasher, AC) at the same time. Apparently, the battery has limited capacity and will be discharged if I supply all these appliances. My question is, while using the battery capacity, if an appliance like the dishwasher or dryer is in the middle of operation and battery would be discharged (SOC_min), would the loads be connected to the grid without any problem in the appliance operation? Or, the battery charge is compared with an appliance consumption (for one activation) in advance so that it could make a decision that the appliance would be connected to the battery or the grid?

The impression was from a paper which describes for battery scheduling where each appliance consumption is compared with the battery capacity to make a decision for starting on grid or battery. I wanted to know if commercial batteries in market work like that, or this was just a specific concept for smart home energy management system discussed in a paper.

Many thanks!

[bcroe]

Batteries have so many issues, generally used only when there is no other way. The sort of appliances
you mention are best handled by a net metering setup, where the Power Co acts as a giant battery.
Bruce Roe

[Sunking]

Simple if you are connected to the grid you have no use for batteries.

Here is what you are missing. Anything you take off grid, just in battery cost alone you will be paying roughly 4 to 10 times more for electricity than what the POCO charges you. So it would be very foolish to go off grid, or have a hybrid system like you are referring to.

Think of it this way. Two gas stations on opposite corners of an intersection. One station sells gas for $2/gal, and the other sells for $10/gal. Why would you opt to pay $10/gal?

Do not say to lesson your carbon footprint because those are the words of a fool. Fact is batteries are heavy heavy polluters. If your goal is emergency power, then use a conventional grid tied system with a whole house generator. A whole lot cheaper to install and operate with a great added benefit. With a generator you get to run everything in your hours. With batteries only a few circuits like your refrigerator and a few lights. Let your neighbors and fools with batteries suffer with an outage.

Besides with batteries you cannot run the high wattage items unless you are willing to pay $40 to $50 thousand dollars every 5 to 6 years replacing batteries not to mention all the Employment Prevention Agency Red Tape and local inspections required for all that toxic waste you will be held liable for cleaning up.

[ButchDeal]

My question is, while using the battery capacity, if an appliance like the dishwasher or dryer is in the middle of operation and battery would be discharged (SOC_min), would the loads be connected to the grid without any problem in the appliance operation? Or, the battery charge is compared with an appliance consumption (for one activation) in advance so that it could make a decision that the appliance would be connected to the battery or the grid?

Ok your question seems to be based on a miss understanding on how solar works. In order to do this as you specified as strange as it is and if there was some reason to set things up this way, would require a bimodal inverter. Now it also assumes that the grid is working so the bimodal inverter is still grid tied.

So so if you wanted to run the dishwasher or any appliance from solar/batter and not the grid, there is no need to do any switching. You just have the inverter put out at least as much power as the appliance is using. This is done at the whole house level often but could be done at an appliance level if you wish. So since there is no switching at all, if the inverter outs out less power at any time the grid takes over the difference. This is all governed simply by ohms law.


the only time you have to switch anything is when the grid is down and then the inverter has to provide ALL power .

now as others have already said economically there is no need for batteries if there is net metering and a grid tie inverter it simply puts out as much power as it can . If there is zero feed in rules then it puts out exactly the power that the home is using or less ( zero feed in ). Simple.