Where Next after Diesel?


“The news of my death has been greatly exaggerated” or so wrote Mark Twain.

Back in the world of diesel engines, it is fair to say that whilst there are a few years left, it is definitely a product approaching the twilight years of its lifecycle, and there is a need to start weaning the world off the diesel engine in a progressive and planned manner.

To this end the UK government has committed to ending diesel and petrol car sales by 2035. However, the Medium Combustion Plant Directive, various industrial emission directives and Non-Road Mobile Machinery Regulations all illustrate this is not just a vehicle specific policy, quite apart from local planning constraints and localised air quality policy. The improvements in air quality during COVID lockdown have demonstrated the impact of normal economic activity. This should be taken as a strong indicator of where policy is going, and where other industries will follow.

One outcome of this is that many construction sites, which are large users of temporary power, will not be able to perpetuate the traditional scene of a number of diesel generators operating in the corner of the site for the duration of a construction project, and it should be noted that current  legislation is already requiring change.  Unlike product emission requirements however, it is not prescriptive. There is an onus on the user to deploy the best available solution, and those who do so must have an environmental best case for their chosen option. Sites deploying temporary power for more than twelve months will now be treated as a fixed installation requiring normal EA permitting.

So, what are the alternatives to diesel for static deployable power? Aside from emissions, diesel is a hard act to follow, since it is affordable, power dense, reliable, well understood, available in a plethora of sizes, mass produced etc., but the fact is if it is “game over” none of these will count. The new game is that emissions are king, and momentum is building to kill off the diesel engine no matter what its positive attributes are, and how they may be improved. If achieved this will set a new paradigm as the diesel engine will no longer be the benchmark against which all other technologies are measured. It is likely that all competing technologies will be more expensive than the incumbent diesel engine to begin with, but of course the true cost of diesel in terms of long-term environmental damage has never been factored in to the current benchmark figure anyway.

The idea, however, of replacing diesel fuelled plant as some sort of binary switchover at an arbitrary date is of course fanciful and would be fraught with all sorts of problems. A rather more planned and orderly switchover is required so that we set in place a glide path to all diesel equipment being replaced by the deemed date.

Ideally such a solution should complement existing diesel product and work alongside it during this transitionary period so that new equipment could be substituted as diesel equipment reached the end of life and new product became available in an ever increasing range of sizes.

At AFC Energy, we are ready to meet this challenge! We’ve been developing hydrogen fuel cell technologies and products for many years. Our research has resulted in a fuel cell which is modular, scalable (20kW to multi-MW) and easily transportable with the highest electrical efficiency in the market (~60% at fuel cell module). Unlike fuel cells used historically in mobile applications, the AFC Energy HydroX-Cell(L)TM can utilise all grades of hydrogen making the system significantly more cost effective relative to alternative solutions. It’s resilient to many fuel contaminants, have low cost of materials and manufacturing steps, along with a much longer operational life cycle. Ongoing developments regarding footprint reduction mean that it will shortly rival the current range of diesel generators with their now attendant emissions control equipment.


Impression of AFC fuel cells and diesel sets on construction site.

All this is good news, but how could such equipment be incorporated with diesel equipment and work alongside it to transition to emissions free generation? The answer is to provide the user with a solution that looks and feels the same as it always has from a functional point of view, but the technology behind it changes. Most larger sites will have multiple generators connected together and able to share load. This also provides a level of redundancy. Step one therefore is to replace one of these generators with a fuel cell generator, with the remainder as before. Such a set up would be managed to preferentially use the AFC Energy HydroX-Cell(L)TM fuel cell, providing clean power, with the diesel sets providing extra power as required all or some of the time. As time progresses,  a greater number of units would be substituted until eventually all power was from fuel cells, and such sites could declare that they were emission free during construction, in complete alignment with the long term objective of the current legislation.

In the meantime, the incremental substitution of fuel cell for diesel can be implemented as a credible scheme to lower emissions in a systematic and coherent manner as part of an emissions reduction strategy.

It should be remembered in considering the above that whilst emissions reduction legislation regarding diesel engines is generally a plant specific type of legislation the latest building regulations come from completely the other direction and require construction project designs to be based on the green credentials of materials used, energy efficiency during later building use, and sustainable construction methods being used during the construction phase. The cost comparison of fuel cells, or other green solutions versus diesel generators is therefore false as diesel will no longer be a viable option. Green temporary power technologies are simply a rolled-up cost in the greater objective of building sustainably, and on that basis the cost difference is negligible.

Graphic of green eco house.

Inevitably in considering the AFC Energy solution, it is necessary to address where the hydrogen is sourced from and how it gets to the fuel cell. If, as currently, much of this argument is that localised air quality around construction sites needs improving, then low grade industrial hydrogen can be used, but as the green building imperative gathers pace there would be a need to switch to green hydrogen produced from wind or solar power, and whilst a little more expensive at the moment, this is essential to meet the sustainable building legislation objectives.

Another question often asked relates to transporting and storing hydrogen as this can also be something of a challenge since it has a low energy density and is expensive to liquify. The answer to this somewhat challenging problem is to transport the hydrogen as ammonia and convert to hydrogen at the fuel cell package. The benefit of this approach is that a delivery tanker of liquid ammonia can deliver approximately 5 times as much energy as a similar sized tanker of compressed hydrogen. Despite using ammonia as a carrier, there is no negative environmental side effect from liberating hydrogen since it simply results in the emission of nitrogen, which is what 78% of our planet’s air already comprises of, and lest there is a worry about this “emission” it should be pointed out that air is where the nitrogen to make ammonia was harvested from in the first place: the whole end to end process being in fact a closed circle.

So, what does all this mean? Essentially it is all change, but no change. The market for temporary power will continue to exist exactly as before, but the means of production must evolve from the diesel engine to technologies that can provide the same power whilst having zero emissions to meet localised air quality, and carbon reduction targets. The AFC Energy solution is therefore an important steppingstone, and indeed final destination on the journey towards the realisation of emissions free hydrogen based temporary power.