Case Study: Battery Analytics in African C&I Solar Projects
A collaboration between AMMP Technologies, ACCURE Battery Intelligence, and Pirano Energy
Introduction
Reliable electricity supply across emerging markets is increasingly dependent on the adoption of battery storage systems. Batteries represent a large part of overall system costs. Early battery failures can hence be a big pain point for system operators and financiers. The main reasons for reduced service life are high battery temperatures and poor operation strategies.
Poor network quality is all too common across emerging markets and can lead to poor data quality. Therefore, one goal of this case study was to see how health-monitoring algorithms could deal with imperfect data sets.
The energy service provider Pirano Energy, the battery analytics provider ACCURE and remote monitoring provider AMMP Technologies collaborated to identify the potential of advanced battery analytics for extending the service life of batteries in real-life applications. The impact analysis was done using operational data of 14 PV-battery systems for C&I applications across Nigeria.
Opportunities for Battery Analytics
For C&I solar projects, batteries often make up around 40% of the total replacement costs.
Case Study Scope
ACCURE, AMMP, and Pirano collaborated to gain field experience on how advanced battery analytics can support energy service companies in the C&I market in operating and managing their batteries.
Goals
- Determine feasibility of battery analytics for African C&I solar projects
- Identify value of advanced battery analytics for energy service companies like Pirano
Scope
This case study used historical battery data from 14 small scale grid-tied C&I projects in Nigeria:
- 14 C&I systems in Nigeria
- 3 to 85 kW PV capacity
- 4.8 to 57 kWh Lithium-ion batteries
Data Quality
The historic battery data was acquired and standardized by AMMP over a period of 11 months and contains irregular data outages due to power or connection outages.
| Parameters | Actual Data |
|---|---|
| Data resolution | 5 min |
| Period of data | 11 months (including data outages) |
| Physical quantities | Pack voltage, Pack current, SOC, Temperature |
Aging Analysis
By evaluating the historical battery voltage and current, ACCURE can derive the remaining capacities of Pirano's battery systems and thus determine the State of Health (SOH) at each point in time.
While most observed batteries expectedly age by a small single-digit percentage amount per year, system 2 stands out by having lost 10% of its initial capacity within just a year.
Assuming there was no change in operating conditions, it would imply that the battery used in system 2 could reach its end-of-life in as little as two years in total.
Further, the analysis allows early and clear identification of warranty cases. If the SOH drops below 80 percent while the battery is still under warranty, a replacement should be demanded from the supplier. ACCURE's analysis proves that the battery was always operated within its specifications. For System 2 this means that it will be eligible for a warranty replacement soon.
The State of Health (SOH) helps to:
- Identify batteries that are most likely to fail soon
- Identify warranty cases
Operational Analysis
Historical data is a great source of information that can be used to extend the lifetime of a battery by optimizing the operation strategy. The evaluation focuses on state of charge (SOC), voltage and temperature characteristics.
As the battery of system 2 is exposed to the most accelerated aging, the operation of this battery was analyzed in detail.
State of Charge (SOC)
The SOC histogram of system 2 shows that the system is fully charged most of the time (1650 hours), while seldom discharged.
A forecast-based charging strategy could reduce the stress on the battery and thus prolong its lifetime. Load forecasts in combination with battery aging prediction can be used to set dynamic charging limits without reducing the utility of the battery.
Battery Temperature
Another cause for increased capacity loss can be a high battery temperature. In terms of aging, temperatures above 20°C should be avoided. The temperature distribution of System 2 showed that the temperature of the battery is excessive throughout the entire sample period, presenting a second potential root cause of accelerated battery aging.
Improved cooling could help to improve the battery lifetime.
Interview with Pirano Energy
After delivering the results of the battery analysis, AMMP's Jonathan Schulte and ACCURE's Marc Mennekes interviewed Stephen Bello, Pirano's Technical Customer Support Lead.
Jonathan: Which of the generated battery insights stood out to you?
Stephen: The insights drew our attention towards batteries with degrading State of Health in comparison to the number of charge/discharge cycles. The high operating temperature was identified as a root cause hence the need to improve the cooling around the batteries to improve their lifespan.
Marc: How can you explain the high operating temperature of some of your batteries?
Stephen: For the system with the highest operating temperature and interestingly also the lowest SOH (system 2), we increased the battery inverter capacity from 5 kW to 10 kW last year. The additional excess heat led to an ambient temperature jump from 38°C to 54°C in the operation room.
Jonathan: Can you take any measurements to prevent the battery from being exposed to these high temperatures?
Stephen: Our cooling solutions are very customized; they depend on the surroundings and the client's desires. For this specific system, it is not possible to add any additional cooling solution. We can only ensure that the windows and doors of the operation room remain open as much as possible. Nevertheless, after seeing the clear correlation between the high battery temperature and battery aging, we will design our systems and include cooling solutions such as fans or air conditions more frequently.
Marc: Would you recommend the use of advanced battery analytics?
Stephen: Yes. The granular overview of battery insights helps our team to manage and operate the batteries more efficiently while extending the lifetime of batteries. This finally reduces the cost of maintenance and expenditure on changing the batteries.
Conclusion
The focus of this work was to illustrate the feasibility and benefits of a battery analytics solution for PV-battery systems in C&I projects in emerging markets. Despite the limited data granularity and several data outages, ACCURE's algorithms were able to perform all insightful analytics.
Through computing the State of Health (SOH) and analyzing the historic operation, the battery analytics enabled us to achieve:
| Result | Example in the Case Study |
|---|---|
| Identified batteries exposed to accelerated aging | Battery of System 2 losing 10% capacity per year (ideal: 2-4%) |
| Understand the root causes of accelerated aging | Battery of System 2 exposed to high temperatures |
| Suggest changes of operation strategies | Change cooling strategy for System 2 |
High temperatures and high SOCs led to higher aging rates (capacity loss per year). For the system with the highest capacity loss, the main root cause was identified as high operating temperatures.
After sharing these results, Pirano was able to confirm that this single system is operating in bad conditions. The excess heat of the electrical equipment was responsible for heating up the operation room and consequently the battery. With these insights, Pirano was able to change the cooling strategy of the battery and can use these findings for their future storage projects.
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