The Ultimate Guide to Solar Panels for Transportation Refrigeration Units: Boosting Efficiency, Reliability, and Savings

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In the transportation industry, efficiency is the name of the game. Every aspect demands optimization, from delivering products on time and intact to managing fleet operations on a budget.

Solar technology significantly impacts efficiency when powering transportation refrigeration units (TRUs).

This post explores how solar panels help the refrigerated transportation sector, offering benefits beyond simple power generation.

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The Challenges of Refrigerated Transportation:

• Reefer unit batteries can be drained and unavailable when needed, leading to downtime and service calls.
• Increasing regulations, such as those proposed by the California Air Resources Board (CARB), limit TRU exhaust emissions.
• Rising diesel costs add to transportation expenses.
• Maintaining the proper temperature for perishable goods is crucial but energy-intensive.

Solar Solutions for Reefers:

Solar panels offer an innovative solution to these challenges.

Let's explore the key benefits:

Enabling Trailer Telematics:

Modern reefers often incorporate telematics systems from companies like FleetPulse, Orbcomm, Geotab, or Novacom. These systems provide valuable data but can drain the reefer battery, especially when trailers wait for a load. A small 20-40W solar panel can counteract this parasitic load, keeping the battery healthy and ensuring continuous operation of vital tracking and monitoring systems.

Improving System Reliability:

Solar panels significantly enhance the reliability of reefer units. One customer reported a 4.32% increase in mean time between failures (MTBF) after adding solar panels to their reefers. This improvement translates to fewer breakdowns, reduced maintenance costs, and increased uptime for your fleet.

Typical reefer batteries have an 18-month warranty, but parasitic loads and other failures can shorten the MTBF. Solar panels help extend battery lifetime by keeping batteries in a higher state of charge. Batteries discharged to a greater depth of discharge result in fewer battery cycles. See the graph below.

Fewer Service Calls:

Dead batteries can lead to expensive service calls and the potential loss of perishable goods. Solar panels continuously charge batteries during daylight hours, dramatically reducing the need for jump-starts, which can run $200-$400 in remote locations. A refrigeration technician can cost around $90/hour, and losing a load can cost thousands. The ROI on a relatively inexpensive solar panel installation is quickly realized.

Diesel Fuel Savings:

Perhaps the most surprising benefit is reduced diesel fuel consumption. A recent two-million-gallon study by a nationwide refrigeration fleet found that adding a 20-30W solar panel to Carrier Vector hybrid reefers resulted in diesel savings of 0.09 gallons per hour. This translates to over two gallons of diesel saved every 24 hours of operation.

The study used a Differential Fuel Meter (DFM) mounted to each reefer's fuel lines and monitored data via telematics. It took place over an entire year, covering warm and cold months, with transported products kept at either 0°F or -5°F.

Emissions Reduction:

Solar-powered TRUs help meet increasingly stringent emissions regulations. CARB has proposed rules requiring zero-emission operation for stationary TRUs by 2025. One proposed rule states, "All trailer TRUs, domestic shipping container TRUs, and TRU generator sets must use zero-emission operation if parked or stationary for more than 15 minutes at an applicable facility and be equipped with an electronic telematics system." Solar panels and battery banks can help fleets meet these requirements today. CARB is looking to drastically lower 2.5-micron particulate matter (PM2.5) and nitrous oxide (NOx) emissions by 2025 from transport refrigeration units (see figures 19 & 17 below). Source: California Air Resources Board.

Reduced Alternator Load and Wear:

Traditional TRUs rely heavily on the vehicle's alternator to power their cooling systems. This constant demand can stress the alternator significantly, leading to increased wear and potentially shorter lifespans. Solar panels provide a supplementary power source for transportation refrigeration units (TRUs), reducing the need for the alternator to supply all the energy. This lessens the alternator's operational load and enhances overall system efficiency, distributing power more evenly and prolonging the alternator's lifespan.

Specific Solar Panel Options for Reefers:

Carrier Vector TRUs:

27W custom TRU-Mount Solar Charging System:

This solution easily attaches directly to the reefer.

Thermo King Precedent TRUs:

Thermo King's ThermoLite 30W Solar Panel:

This solution features cut crystalline wafers and an independent PWM charge controller.

Disadvantages include:

• Lower wafer efficiency due to edge defects.
• Less power is delivered to the battery (61% efficiency for a 30W panel).
• Longer installation times.

PowerFilm's 24W Solar Panel with Integrated Charge Controller:

This solution fits between the fans of the Precedent TRU.

Features include:

• Easy installation with four self-tapping screws.
• Allows access to the radiator cap without removal.
• Integrated FPPT charge controller.
• 88% power efficiency at 12V.

TRU Solar Panel Power Comparison:

The Thermo King panel lists a 30W output, but due to cut cells prone to edge defects and a lower-quality charge controller, it only delivers 18.4W to the battery (61% efficiency).

Due to the PWM charge controller, the power delivered to your reefer battery is much lower than the published panel wattage (see graph above).

The PowerFilm panels are rated well under 30W, but at or near 90% efficiency, they provide more power to the battery than a Thermo King panel.

Return on Investment:

Solar panels for reefers offer a quick return on investment:

• Fuel savings alone can result in panels paying for themselves within a few months.
• Calculation formula: (24 hours x 0.09 gallons/hour x diesel price/gallon x 365 days) = Annual savings.
• At $5/gallon diesel, potential savings are $3,942 per year per reefer.
• Additional savings from reduced maintenance and increased reliability.

Implementation Strategies:

To maximize the benefits of solar panels for your reefer fleet:

• Consult with solar providers or TRU manufacturers to determine the best solution.
• Consider a phased implementation to test and measure results.
• Integrate solar performance into your fleet management and maintenance systems.
• Train drivers and maintenance staff on the benefits and care of solar-equipped reefers.

Conclusion:

Solar panels for transportation refrigeration units offer many benefits: improved reliability, reduced maintenance costs, significant fuel savings, and environmental compliance. As regulations tighten and efficiency becomes ever more critical, solar technology presents an innovative solution for the refrigerated transportation industry.

By embracing this technology, fleet operators can stay ahead of regulatory requirements, reduce operational costs, and contribute to a more sustainable future for the transportation industry.

The future of refrigerated transportation is bright-and solar-powered.

Contact us today for more information on solar solutions for your fleet.

Sources:

https://ww3.arb.ca.gov/cc/cold-storage/documents/hra_emissioninventory2019.pdf.

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