Throughout the history of Claytex, we have applied state of the art systems modelling and simulation techniques to solve the problems faced by both road vehicle OEMs and in motorsports. The application of our knowledge and tools ranges from human comfort in the cabin to destructive vibration in the driveline with recent focus on the electrification of the powertrain and its ancillaries. Last but not least of course, is our experience in the field of ADAS (advanced driver assistance systems) and autonomous vehicle development. The time has now come for us to apply these proven techniques and methodologies to the agriculture industry as we discuss in this article.
Increasing demands for more and better quality food coupled with more changeable weather conditions apply greater pressure on food production chains. One method to reduce this pressure is to improve the efficiency of agricultural machinery with the electrification of the powertrain and/or the ancillaries. Choosing the right electrification architectures is key for success.
Correctly considered, electrification can yield benefits not only for CO2 emission reduction, but also for the users and operators of the machinery. User benefits of plant electrification can be quantified in terms of lower running costs (albeit vs a potentially higher development and purchase price), enhanced operation control via electrified drives and considerable reductions in fuel usage over the years.
This is not to say that electrification will suit all agricultural vehicles or indeed applications. Investment is high, so predicting the return on investment and usability is absolutely key for both manufacturers and operators.
Farms that also benefit from solar panel installations can use such electrical energy sources to charge the electrical energy storage devices on the machines at low unit price costs. Such electrical energy sources can also be used for preconditioning of the machinery to improve operational efficiency (cabin, battery, lubricant and hydraulic oil preconditioning).
Figure 1: Big farm tractor tilling dusty Springtime fields, aerial view.
One of the first tasks when looking at the potential of plant electrification is understanding what the typical use / duty cycle will be. This is likely to include:
Additional consideration needs to be given to whether these operations are required to happen in one go; i.e. continuous machinery operation until the job is done. Particularly significant for harvesting, for example, within favourable weather condition windows.
So, for instance, it’s potentially detrimental having an electrified vehicle that can only operate for 4 hours on a charge when the typical shift would be 12 hours continuous operation. The operator would either have to either hire/purchase two or more vehicles that can be used alternatively throughout the operating time span; whilst one is in the fields, the other one is being charged.
Preconditioning – what is it?
Thermal management including preconditioning of powertrain related components is also key to maximising the plant efficiency and the ability to extract the full performance of the vehicle powertrain right from the start of operation. The most important and sensitive electrified powertrain system component that requires a well designed thermal management system and strategy is the electrical battery.
Figure 2: Battery preconditioning can yield significant benefits
Operating in high temperatures with low vehicle velocities and high loads means that large radiators and forced convection will be required to keep battery temperatures under control particularly when fast charging at standstill.
Conversely in cold conditions, we might not have such an issue managing the battery temperature in terms of cooling. However, we will need to consider the drop off in performance of the vehicle due to the increased internal resistance of the battery at low temperatures. In this case, preconditioning the electrical battery would be advised, particularly for larger batteries, where potentially the thermal inertia will be higher.
By nature, battery packs, such as ones fitted in place of the internal combustion engine in an agricultural vehicle, have the potential of high thermal gradients across them. Primarily, this is driven by the fact that the centre of the battery pack will be surrounded by many cells, in comparison to the flatter battery pack installations as seen on road vehicles. This can not only represent thermal management challenges but also pose battery degradation limitation challenges as a result of a simplistic thermal management system. This can be modelled using a systems approach where system design optimisation can be automated.
Investigations on trailers fitted with underfloor batteries have been made to increase plant range where this is required in a modular battery capacity augmentation approach.
Cabin and ancillaries:
When electrifying vehicles, the power consumption of non-powertrain systems might often be neglected. Such neglected systems can include the hydraulic pumps; also, where there are on-board operators within a cabin, the thermal management of the cabin will also have an impact on the power consumption. This is especially true if we are relying on PTC (Positive Thermal Coefficient) or electric heaters that are taking power out of the battery and therefore reducing operational range.
Plant cabins tend to have a high glazing-to-solid partition ratio for enhanced visibility and therefore will suffer significantly from solar gain in sunny weather conditions and high heat loss during the colder periods.
Preconditioning of thermal batteries is one way to reduce the electrical energy drain on the vehicle battery, especially where there are off-board electrical energy sources to achieve this. The stored thermal energy can be used to maintain a thermally comfortable cabin temperature for the duration of the operation without having to rely on PTC heaters. A range of thermal energy storage technologies can be considered including phase change materials.
Lubrication and hydraulics:
Oil viscosity and drag increase at lower temperatures generate higher loads on the pumps and gears contributing to the on board electrical energy device depletion. Pre-conditioning the oil temperature can reduce these parasitic mechanical losses during operation.
The lighting for low light level operation should also be taken into account, although the advances in recent years utilising LEDs have drastically reduced the power consumption of these systems.
How to develop such a revolutionary platform?
Historically, the preferred approach in the industry has been to build prototypes and demonstrator vehicles to prove a concept. Today we have all the tools necessary to be able to make 1000s of predictions from desktop using physics based models that for many years have been used in other areas of vehicle engineering.
In order to predict and simulate the plant operation effectively, all of the discussed points must be taken into consideration. We must integrate all the vehicle device, trailers, environmental conditions and soil conditions to be able to get a good idea of the electrified architecture design suitability and therefore design success:
- Thermal management
- Ambient conditions
Figure 3: CAD geometry can be brought into simulation animations to visualise mechanical actions
As with any ground-based vehicle in 2020, autonomous navigation of terrain offers much development potential. We are in a position to apply years of experience of autonomous vehicle design and testing into agricultural machinery. This includes not only the integrated plant models themselves, but also sensor models, so that the vehicles can be tested in virtual environments. Users can then dial in the conditions under which the vehicles are operating and predict the behaviour of all systems involved.
Figure 4: Ground vehicle automation is beginning to appear over the horizon…
What can we do to help you?
Lots is the simple answer! As leaders in systems simulation, we can:
- Help customers move towards zero prototypes
- Predict vehicle performance in user-experienced and user-defined scenarios
- Virtualise tests including performance and durability testing for powertrain, chassis and vehicle subsystems
- Conventional and hybrid architecture design optimisation to suit the intended duty cycles
- Component sizing for meeting your product and customer requirements
Written by: Alessandro Picarelli – Engineering Director