25 Jan 24

7 alternatives to battery-powered drivelines

While the shift to carbon-neutral mobility and transport has become almost interchangeable with battery-powered drivelines, alternative solutions are still under research and development. Legislation isn’t tech-biased, so these might still stand a chance to play a role in decarbonizing fleets across Europe. Let’s have a deeper look at the oddball options and check their feasibility.

1. Hydrogen (HEV)

Ready for use in both combustion engines and fuel cells, the efficiency of hydrogen is considerably higher in the latter. HEVs rely on zero-emission electric drivelines (often hybrid with a buffer battery), increased autonomy and fast refills. Sourcing hydrogen from renewables and scaling up the infrastructure remain tight bottlenecks, even though the EU has endorsed a network rollout under AFIR.   

Doubt among investing automakers is rising for hydrogen to become viable in passenger cars. Hope is shifting to commercial fleets due to easier refilling if depot-based and almost mimicking the payload specs of diesel equivalents.

2. eFuels

A chemical combination of green hydrogen and CO2 capture produces electric fuels with a comprehensive use case (from diesel to kerosine) and no adaptation for the combustion engine applied. It’s zero-emission by CO2 compensation and not at the tailpipe while still subject to toxic emissions—the sky-rocketing pump price demands a scale-up to control the cost.

Germany put the door ajar for using e-fuels after the EU ban in 2035. With high flexibility and backing from investing industry stakeholders and major governments (plus a compulsory blending with current fuels), e-fuels could hold a genuine promise for decarbonising existing fleets. The green lobby disagrees.

3. Compressed Air Vehicles (CAV)

Both Toyota and Peugeot showcased cars on compressed air (CAV) but left the idea to ripe with small companies like MDI (Luxemburg, pictured above) and Energine Corporation (South Korea). CAVs emit no pollutants and use vessels with compressed air to propel a reversible engine. Compressed air can also be used in conjunction with a battery and electric motor.

Small in size and limited in cost, CAVs could play a role in urban mobility as free-floating pods. Compressed air is available in abundance as the fourth utility in the industry sector. Still, its lack of torque and low energy density make it hardly suitable for bigger-sized vehicles.

4. Solar-Electric Vehicles (SEV)

Cars exclusively running on solar energy struggle with extremely unpractical packaging, so solar panels serve better as a range extender for conventional BEVs. Ground-breaking startups like Ligthyear and Sono Motors had to throw in the towel at the production phase, leaving the technology as an add-on in conversion cases.

The promise of solar-electric vehicles (SEVs) suffered a premature death over the switch from prototype to production. But commercial fleets struggling with the range of current eLCVs and e-trucks can benefit from the technology as a range-extending accessory.

5. Hydro-Treated Vegetable Oil (HVO100)

A synthetic substitute for diesel. Hydro-Treated Vegetable Oil differs from biodiesel in some key aspects. It is made from advanced raw materials such as residues and waste, including used cooking oil, and not from plants like rapeseed. Also, the catalyst is hydrogen and not methane. As a second-generation biofuel, it increases CO2 reduction (90%) and performs better than first-generation biodiesel. Its flexibility means diesel engines can run on HVO without modifications.

The limited production output, high price per litre and poorly developed supply chain obstruct the adoption of HVO100. It stands a chance in heavy transport and agricultural fleets but is left out for passenger cars as it is not zero-emission.   

6. Flowcell

Dubbed a revolutionary power source, the flow cell (also used as stationary energy storage in wind turbines) consists of two tanks of ionic liquid, one positive and one negative. These are combined in a membrane, providing energy for the electric motor. With their exceptional power delivery flow cells can deliver ranges of up to 800 kilometres while being refilled in mere minutes.

Flowcells are a safe, green and versatile power solution, but they lack backing from legacy car makers altogether while setting up a filling infrastructure for the bi-ionic liquid forms a tremendous barrier. OEM nanoFlowcell showcased its first car ten years ago, and the odds have hardly changed since then.

7. Nanotubes

A completely new technology for generating energy. The starting point is carbon nanotubes with unique electrical properties. These hollow tubes made of lattice or carbon atoms are thinly coated with a layer of fuel, possibly LPG, hydrogen or diesel, which is subsequently superheated, causing a reaction of electric current.

Nanotubes can create electricity without a battery, ditching the weight penalty and charging times. Though twice as energy efficient as a conventional combustion engine (up to 80%), they still produce CO2 as a byproduct and don’t match with auto maker’s zero-emission goals—a possible solution for niches like supercars.

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Image Source: MDI

Authored by: Piet Andries