Performance of Tandem Solar Cells in Real Pilot Solar Farms: A Case Study

As the solar industry expands, researchers and manufacturers are seeking innovative techniques to boost energy production. In this process, pilot solar farms play a crucial role in evaluating new solar technologies before they are deployed on a large scale. Among the new developing technologies, tandem solar cells are one of the most promising breakthroughs. This article explains a real Pilot Tandem Solar Farm, located near Las Cruces, New Mexico. It will give you a project overview of the real pilot tandem solar panel, the project’s layout, the technologies used in it, and an analysis of its performance.

What Are Tandem Solar Cells?

The word “Tandem” refers to working together. A multi-layered solar cell, where each layer is made of different materials to absorb different parts of the sunlight spectrum, is known as a tandem solar cell. In a tandem solar panel, all the layers stacked one over the other work together to absorb more sunlight. Thus, it enhances the power production as compared to the traditional solar panel.

A tandem solar cell is made by splitting the solar spectrum into two layers, i.e., the top layer and the bottom layer. The top layer is usually comprised of perovskite or another wide bandgap material that can capture high-energy photons, such as ultraviolet (UV) and visible light. The bottom layer is typically made of silicon that captures the lower-energy photons that pass through the top layer.

With a high energy efficiency of above 30%, the tandem solar cells can produce more energy in less space.

Project Overview of Real Pilot Tandem Solar Farm

What Is a Real Pilot Solar Farm?

The pilot solar farm represents a small-utility-scale solar installation. It serves as a research and demonstration site. It is used as a testing ground for newly invented solar panels, new technologies, inverters, and performance tracking systems. The places selected for pilot solar farms are usually semi-arid regions with high solar exposure.

The main goal of a pilot solar farm is not just to generate renewable energy. It represents how the newly developed technology and the system can work under real-world conditions.

Project Overview of Real Pilot Tandem Solar Farm

The real pilot tandem solar farm is located near Las Cruces, New Mexico. The is a location with high solar radiance and a dry climate. So, it is selected to study the performance of the tandem solar cells under intense sunlight and extreme temperature swings. It evaluates the long-term reliability and efficiency of tandem solar cells.

The average solar radiation in the Las Cruces area is 6.5 kWh/m²/day with over 320 sunny days per year. This desert area has flat terrain with minimal shading.

This small-scale solar farm covers around 15 acres of leased land. The installation capacity of the solar farm is 3 MW DC. Approximately 7500 tandem solar modules are used in this project. Aluminum racking is used as the mounting structure with a 25° tilt on fixed arrays. For comparative analysis, 2 string inverter types are used in this project. The whole site is divided into 10 zones consisting of perovskite-on-silicon, all-perovskite, and III-V hybrid structures.

Location	Near Las Cruces, New Mexico
Solar radiance	6.5 kWh/m²/day (High)
Installation capacity	3 MW
Used Tandem Solar Modules	7500
Tilt Angle	25°

Real Pilot Tandem Solar Panel Layout

The layout of a real pilot tandem solar panel involves different technologies, precise monitoring, and real-world weather conditions. An organized layout isolates and compares the performance of tandem solar panels side by side. It compares the differences in output power based on various materials and mounting structures. It also identifies the best configuration that delivers the most stable and long-term performance. Thus, the successful test zones are upgraded to future commercial projects.

The real pilot tandem solar panel, situated near Las Cruces, New Mexico, has 10 performance testing zones that spread across 15 acres of land. For optimal solar tracking, the rows are designed with north-south orientation. Each testing block is separated by gravel pathways. The inverters are connected to the central control room with underground cabling. Each array is independently connected to its own string inverteror centralized inverter hub.

A table consisting of various testing zones, including different types of tandem solar modules, mounting structures, and inverter configurations, is represented below.

Zone Type	Solar Modules Used	Mounting Structure	Number of Panels
Zone A	Perovskite-Silicon Tandem	Single-axis Tracker	1000
Zone B	All-Perovskite Tandem	Fixed-Tilt	900
Zone C	III-V on Silicon Tandem	Dual-axis Tracker	800
Zone D	Bifacial Tandem Panels	Single-axis Tracker	950
Zone E-J	Mixed Technology	Mixed Mounting	700

The sensors and weather instruments used for monitoring equipment are

1. Pyranometers (Solar irradiance readings)
2. Temperature sensors
3. Anemometers
4. Soiling sensors
5. Thermal cameras

Technologies Used in Real Pilot Tandem Solar Farm

1. Tandem Solar Modules

This project uses mainly 3 types of tandem solar panels.

1. Perovskite-Silicon Tandem Panels: It consists of a perovskite top cell and a silicon bottom cell. It offers higher voltage output and powerful performance.
2. All-perovskite Tandem Cells: These tandem cells have both layers of perovskite materials with different band gaps. These are lightweight and potentially cheaper.
3. III-V/Silicon Tandem Panels: These tandem panels are made by combining gallium arsenide or other III-V compounds with silicon.
4. Mounting Structures

The mounting structures are classified into 3 categories.

1. Single-axis tracker: The panels rotate east to west during the day.
2. Fixed-tilt mounts: The panels are fixed andtilted at 25° facing south.
3. Dual-axis tracker: It tracks the sun in both azimuth and elevation.

3. Inverters

The types of inverter technologies used in pilot tandem solar farms are

1. String inverters:
2. Central Inverter
3. AI-powered inverters

4. Sensors Used for Performance Monitoring

Various sensors are used to monitor the panel’s performance:

1. Irradiance sensors: Measure sunlight intensity
2. Temperature sensors: Measure the heat
3. Soiling detectors: Detect the dust and dirt buildup over the panel.
4. Weather stations: Monitors wind speed, sunlight, temperature, and humidity

5. Cloud-Based Monitoring System

This advanced technology helps to store and analyze energy production and environmental data. This data helps fine-tune module designs to enhance the performance level of the solar panels.

Performance Analysis

Energy Output

After one full year of operation, approximate data based on energy output is represented below.

Total Energy Output	5100 MWh (Approximate)
Average Daily Energy output	14 MWh (Approximate)
Peak Capacity Factor	19.4%
Performance Ratio	83%
Increase in Energy Output compared to traditional Silicon Panels.
Perovskite-Silicon	+18%
All-Perovskite	+12%
III-V/Silicon	+22%

Challenges Observed in Pilot Tandem Solar Farm

1. Thermal degradation causes a significant drop in performance in some modules during July and August.
2. The sudden wind gusts, especially during the spring and monsoon seasons, lead to mounting frame stress, panel vibration, and tracking system misalignment.
3. Over the years, there are chances of chemical reactions between multiple layers of the tandem solar cell, which lead to minor efficiency drops.
4. In desert areas, the soiling and dust accumulation cause energy losses.

Conclusion

The real pilot tandem solar panel is a testing ground that helps researchers and developers understand the real-world limits of tandem solar technology. The real pilot project represents the potential of tandem solar panels when deployed under real-world conditions. The project offers a solid foundation for scaling tandem technology in utility-scale solar farms.

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