Why Solar on Trucks?
Truck-mounted solar can save fuel by providing power for cabin services (heating/cooling, fridge, entertainment), refrigeration (reefers) and even range extension. Truck-mounted solar is not yet popular, because of the perception of high cost and the uncertainty about the payback time. Savings from truck-mounted solar is more difficult to determine than for grid-connected solar. Factors that affect the savings include: truck route, which determines the solar irradiation, electrical load, fuel costs, and solar system efficiency/durability. To help individual truck and fleet owners, manufacturers and end users determine whether solar makes sense for their application, Fraunhofer can measure the solar potential for a specific truck or trucking fleet. The following case study provides an example.
Case Study: Reefers in the Northeast US
Fraunhofer CSE (Boston, MA), partnered with Agri-Mark/Cabot Creamery (Burlington, VT) to measure the solar potential on two reefers in the Northeast during October-December 2016. Self-powered instrumentation was installed to measure the amount of sunlight, rooftop temperature and truck location on the road. Table 1 describes the instrumentation package.
The instrumentation is solar-powered, with the battery, data-logger and cell modem contained in a weather-proof enclosure mounted on the trailer behind the tractor. The Cabot Creamery trucks traveled throughout Vermont, New Hampshire, Maine, Massachusetts, Connecticut and New York, making regional deliveries of cheese.
Northeast US Study Results
The dataset was filtered using several criteria: day/night, moving/parking, in home port/traveling. The solar energy generated while moving is more valuable as the truck is off-grid while on the road. While in home port, the truck could feed the solar power into the grid to generate savings at grid electricity rates.
The Cabot Creamery trucks moved 15% of the time (15% off-grid) with most of their time spent at their home port (Burlington, VT). Assuming full roof coverage of solar (36 m2; 388 ft2), a total energy savings equivalent to 290 gallons of diesel per year was calculated. The energy savings during the off-grid time is equivalent to 44 gallons of diesel.
Case Study: Reefers in Central Europe
The same instrumentation was installed on 4 reefers which traveled through Central Europe from June 2016 through January 2017. The truck that traveled furthest south into the French Riviera generated the most total fuel savings (equivalent to 480 gallons of diesel). Both the sunnier location and the warmer season increased the fuel savings compared to the Cabot Creamery trucks driven in the Northeast during the fall months. The off-grid time (35%) enabled an annualized energy savings of 169 diesel gallons while on European roads (vs. 44 diesel gallons calculated for the Northeastern US). Table 2
compares the energy savings of the best Cabot Creamery truck with the best overall truck of the study.
How can Fraunhofer help?
Together with Fraunhofer ISE, Fraunhofer CSE can provide an analysis of the savings and payback time for your truck in your usage scenario. Fraunhofer would install instrumentation on your truck(s), record the data and perform the analysis to provide solar power output, fuel savings and payback time.
Most current solar installations on trucks are “retrofits” and thus are not fully optimized for the truck application. Fraunhofer ISE can partner with trailer/truck manufacturers to design an integrated solar system which is optimized for trucking. Design aspects such as ventilation, temperature management, cable management, weight and durability will be optimized to maximize output while minimizing cost.
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