Batteries only charges to around 70 %

asked 2019-05-25 07:45:17 -0600

audunbul
81 ●3

updated 2019-05-27 15:26:59 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

I am simulating an off-grid building with PV-battery system in Shanghai, where I expect that we shall have excess energy some part of the year. I have set the initial battery changing state to 100%, but it never recharges to more than around 70% over the year. Even if I doubled the PV capacity, this did not change. Does anyone have some ideas about what can be wrong in my settings? I supposed it might be a wrong setting that limit the maximum charging power. I tried to change the "Design Storage Control Charge Power" under ElectricLoadCenter:Distribution to 300 W * 24 stk = 7200 W and the Design Storage Control Discharge Power to 570 W*24 stk = 13860 W, instead of my initial setting that was for 1 battery (300 W, 570 W). It is 24 batteries connected in series. But that led to a fatal error "ElectricLoadCenter:Storage:Battery named="LEAD ACID BATTERIES". Battery discharge current could not be estimated due to iteration limit reached." Here is a PDF which shows my PV and battery settings.

answered 2019-06-11 17:28:31 -0600

MJWitte

9740 ●6 ●10 http://www.gard.com/

I would start by comparing inputs with the ShopWithPVandBattery example file, which does fully charge each day.

Then I would add every available Electric Storage and Electric Load Center output variable and report them hourly or timestep and see what's happening in the model.

From a quick glance at your inputs, it seems the Design Storage Control Charge Power of 300 W may be too small? If I'm following correctly, the storage capacity is 500 Ah * 24 Modules * 2.32 V = 27.84 kWh. That means it would take 27.84kWh/300W = 92.8 hrs to fully charge. Try leaving the Design Storage Control Charge and Discharge Power fields blank as in the example file.

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Good reasoning about the charging time. I had used the ShopWithPVandBattery example file when I set up my file. I tried to compare again and make some changes, as long as I kept the Design Storage Control Charge and Discharge Power fields blank I got a fatal error:

"* Fatal * ElectricLoadCenter:Storage:Battery named="LEAD ACID BATTERIES". Battery discharge current could not be estimated due to iteration limit reached. "

As I mentioned last time, I also got the fatal error when I increased the Design Storage Control Charge and Discharge Power as for the whole battery pack.

audunbul ( 2019-06-13 00:48:24 -0600 )edit

I added all battery report variables, but it only reported for the design day since the yearly simulation did not run because of the fatal error. The total battery voltage and discharge power seemed to be normal.

audunbul ( 2019-06-13 00:49:52 -0600 )edit

It's difficult to know what to suggest without seeing the full idf file. Please post a link here or send it to the helpdesk at energyplus-support@gard.com