How will the energy efficiency of folding PV containers be monitored and evaluated?

Folding photovoltaic containers have taken a leading position in recent solar power solutions because of their unique flexibility and efficient performance. Not only are these containers deployable rapidly, but they can ensure a stable power supply against all kinds of environments. How would anyone go about accurately assessing the energy efficiency of a folding PV container?

1. Basic Concept of Folding PV Container
A folding PV container is a containerized device for integrating a PV power generation system and an energy storing system. It allows easy transportation and storage of photovoltaic panels in compact form and quick unfolding in application for efficient conversion of solar energy.

2. Importance of Energy Efficiency Assessment
Energy efficiency assessment is one of the most important works for folding PV containers. It is related not only to the ROI of the equipment, but also directly to the stability and reliability of the power supply. An accurate energy efficiency assessment can help operators to optimize the system configuration and improve the power generation efficiency, thus reducing the operating cost.

3 Key factors for assessing the energy efficiency of folded PV containers
3.1 I-V curve test
The I-V curve test is one of the important methods for appraising the electrical performance of PV modules. By measure of current and voltage in different light conditions, through which IV characteristic curve, it can plot and thus analyze such electrical performance parameters as short-circuit current (Isc), open-circuit voltage (Voc), maximum power point current (Impp), voltage (Vmpp) of a module, etc. These parameters are very necessary for testing the generating efficiency of folded PV containers. The concrete practices are as follows: The function fitting method using the exponential function and the function fitting using the polynomial are adopted to fit the I-V characteristic curves of PSCs through the least squares method based on the test data of PV solar cells; analyze the influence brought about by different methods to the I-V characteristic by comparing the fitting error.
I-V curve tester: Professional I-V curve tester, for instance, the Italian HT I-V6002 can test single-sided and double-sided PV modules I-V curve and support two different sensors measuring the backside radiation of PV modules according to the IEC technical specification TS 60904-1-2.

3.2 Energy Storage System Efficiency
The energy storage system is an important composition of the folded PV container. The energy efficiency of the whole system is directly affected by the efficiency of the energy storage system. To evaluate the efficiency of the energy storage system, a number of factors need to be considered concerning charging and discharging efficiency, self-discharge rate, and cycle life. Together, these factors determine the performance and reliability of the energy storage system.
Payback period method: calculate the payback period of the investment cost of the energy storage system, i.e., investment cost/annual savings in electricity and maintenance costs.
Cost-benefit Calculation Model: establish the cost-benefit calculation model of the energy storage power plant and, by taking some practical examples, prove that under certain conditions, the energy storage power plant will achieve the expected economic benefit.
Measurement of economic value and environmental value: In studies related to measuring the economic value of Energy Storage Systems, an economic evaluation model has been established for energy storage systems operating under open market conditions. It examines the utilization of genetic algorithms in the calculation of benefit and optimal ratios that may be realized.

3.3 Environmental Adaptability
These foldable PV containers are operating in many extreme environmental conditions; hence, this factor must be considered regarding the evaluation of energy efficiency, including the weather and temperature resistance of PV modules, and the thermal management capability of an energy storage system.
Weather resistance test: employed to test the performance of PV modules under different climatic conditions, such as the impact of environmental factors like high temperature, low temperature, and humidity on the performance of PV modules.
Thermal management capability test: test the thermal management capability of the energy storage system, including the heat dissipation and insulation performance of the battery.

3.4 System integration
System integration is also an important aspect of energy efficiency for folded PV containers, mainly including matching degree between the PV modules and energy storage system, intelligence of control system, and automation level of the system. It includes a system matching test: testing the energy matching efficiency between PV modules and energy storage system through actual operation data.
Intelligence and automation test, test the intelligence degree of the control system, such as remote monitoring, fault diagnosis and auto adjustment.

4 Test methods
4.1 On-site test
Field test is a direct method to check the energy efficiency of folded PV containers. It tests the equipment in the actual operating environment and collects real operating data, such as power generation efficiency, energy storage efficiency, and system stability. These data are so important for the assessment of energy efficiency.

4.2 Simulation Testing
Simulation testing refers to the utilization of computer simulation software for the simulation of folded PV containers’ operation. In other words, it’s a way to predict in advance the energy efficiency performance of equipment before it actually operates. It is able to consider a wide range of different environmental conditions and operating parameters for comprehensive data to support energy efficiency assessment.

4.3 Performance Comparison
The comparison for performance is made to evaluate the energy efficiency of the folding PV containers by benchmarking the performance of others. In this direction, it helps operators take a realistic view about how competitive their equipment could stand in the market and indicates avenues for improvements.