Though the current wave of electric vehicles is transforming the on-road passenger and commercial vehicle fleets, similar attempts in the off-road equipment sector appear to be lacking. Because of the diverse equipment categories and varied applications, electrifying off-road equipment requires significant research and development. A successful electrification of such equipment can offer an array of benefits, including reduced air and noise pollution, higher energy efficiency, and increased productivity. This paper provides a review of the current state of technology in off-road equipment electrification, with a focus on the equipment used in construction and agricultural applications. The paper also discusses advantages of, and challenges associated with, electrifying off-road construction and agricultural equipment. In addition, potential solutions for overcoming these challenges as well as opportunities to facilitate the electrification of off-road construction and agricultural equipment are identified.

Aftertreatment technologies in Tier 4 off-road engines have resulted in significant emission reductions compared to older tier engines without aftertreatments. The appropriate characterization of Tier 4 engine emissions in consideration of aftertreatment operation is important for projecting emissions and developing mitigation strategies. The current method of aggregating emissions over an entire duty cycle and averaging them by engine load has a limitation in developing emission profiles over various duty cycles of Tier 4 engines, especially at low-load operations, where aftertreatment control for NOx may not be effective. In this study, an engine power binning method was developed to characterize emissions for Tier 4 construction equipment with aftertreatment systems, especially at low-power operating conditions. This binning method was applied to real-time emissions and activity data for four different types of Tier 4 construction equipment. Results show that low-power operations (<20% engine power) are responsible for 38–60% NOx and 11–51% of PM_2.5 emissions depending on the equipment types. These results underscore the need for controlling NOx emissions during low-power operations. PM_2.5 EFs for non-DPF backhoes were one to two orders of magnitude greater than all the other equipment due to the lack of a DPF, despite being certified to the same PM_2.5 standard. This shows the benefits of DPFs on construction equipment and that they are substantial in reducing PM_2.5 emissions. Estimated emission differences between using the binning and the averaging methods were 49–86% and 16–82% for NOx and PM_2.5, respectively. These differences may change once the binning method is applied to larger emission datasets obtained from real-world vocational activities.

Effective incentive strategies have played a major role in the electrification of on-road vehicles. Similar approaches to the off-road sector will be needed to continue decarbonizing the transportation sector. Estimating cost-effectiveness with given incentive funds is crucial to successfully develop and implement financial incentive strategies. Because of the lack of cost information for electric off-road equipment, forecasting cost-effectiveness of electrifying the off-road fleet is not feasible. We developed cost projection models for major components of off-road equipment and combined them into an equipment cost simulation tool. This simulation tool was then used to estimate NO _x , particulate matter, and CO ₂ emission-based cost-effectiveness when diesel off-road equipment is replaced with equivalent electric equipment. Use of the developed cost-effectiveness framework in developing incentive strategies was also demonstrated. Finally, a sensitivity analysis was conducted to address potential variations of the assumptions made for projecting the cost of components and the resulting cost-effectiveness estimates. The framework demonstrated in this paper will inform governmental inventive funding programs to design the most cost-effective strategies, considering equipment vocation, model year, and usage.

The objective of this research was to collect real-world activity data from agricultural equipment that could be considered when informing air quality and incentive programs in California. This included monitoring 208 tractors via either engine hour records or data loggers, with 103 of these tractors monitored with data loggers. The results showed that the average annual hours of usage for agriculture tractors declined as a function of engine age/older engine technology. The average annual hours of usage were 60, 130, 143, 741, and 739 h, respectively, for Tier 0, Tier 1, Tier 2, Tier 3, and Tier 4 tractors. The tractors were used for about 4 h per day on average. During that time, the average engine load typically ranged between 22% and 35% for the different categories, with an overall average load percentage of 28% and an average idle percentage of around 26%. Average fuel-use rates were 4.2 gal/h, with a maximum of about 8 gal/h for the 225–478 kW category, whereas the categories <130 kW had fuel-use rates of about ≤2 gal/h. The average diesel particle filter (DPF) temperatures were ≥250°C across different power categories, although the temperature distributions showed that the DPF outlet temperature is <200°C for approximately 21.5% of the operational time, which is below the temperature typically needed for the injection of urea into the selective catalytic reduction.