High Efficiency All-Electric Truck & Trailer Refrigeration Unit Plug Load Evaluation

Work with local refrigerated truck fleet to demonstrate energy demand profiles, costs and benefits. Use plug-in capabilities, truck/trailer mounted PV, batteries, to demonstrate environmental and cost benefits of using electric powered TRus as much as possible. Substitute R-404A refrigerant with drop in replacement to demonstrate impacts to efficiency of TRu and ability to operate on electricity by characterize the energy and GHG impacts.

The California Air Resources Board (CARB) regulates Transportation Refrigeration Units (TRUs) and is rolling out requirements for TRUs to be all-electric (eTRUs). The project scope consists of a general discussion of the eTRU market, analyzing the impact of related, upcoming CARB regulations, and evaluation of one electric truck-mounted eTRU scenario. The two main project goals were to evaluate the performance of an eTRU and compare its energy usage, energy cost, and demand cost to existing hybrid TRUs. The scenario was a box-truck-mounted eTRU for above-freezing compartment temperatures (also known as a “medium temperature scenario” as opposed to a “low temperature scenario” for below-freezing compartment temperatures). The evaluation was concluded as planned. An eTRU with solar Photovoltaics (PVs) and batteries installed on a medium-temperature box truck operated by a wholesale food distributor. The eTRU achieved the required performance of maintaining the box temperature setpoint for the duration of the distributor’s deliveries. Two undesirable behavioral issues were found to reduce system benefits. First, neglecting to plug the TRU into shore power; and second, a reluctance to fully disconnect from diesel, leading to the intermittent use of the diesel system. Resulting invalid data was left out, where possible. The first issue is a matter of operational procedure, and it is likely to reduce as the technology proliferates. The second issue is an artefact of the retrofit approach used for this project. A diesel hybrid system was converted to all-electric, and the diesel components were left operational at the system owner’s request, to serve as backup. A normal marketplace system would be truly all-electric, with no diesel backup. The demand, energy usage, and utility cost of the baseline hybrid TRU and eTRU in the medium-temperature scenario are compared in Table-ES 1. All metrics increased for the eTRU, as expected, since it had batteries to be charged. Results may vary from site to site due to operational variables, tariff differences, and dependence on weather. The tariff used here was TOU-GS3, option D, no Critical Peak Pricing (CPP). This is a common tariff for medium-sized businesses with 200-500 kilowatts (kW) of peak load. For the tested scenario, simple payback economics were in favor of the all-electric system. Despite a high first cost of $80,000-$120,000, simple payback will be achieved after 4.9 to 7.4 years. Actual economics may vary due to several factors not considered in this study.