Criticisms

Cost of production

Liquid nitrogen assembly is an energy-intensive process. Currently applied algidity plants bearing a few tons/day of aqueous nitrogen accomplish at about 50% of Carnot efficiency.1

edit Activity body of aqueous nitrogen

Any action that relies on a phase-change of a actuality will accept abundant lower activity densities than processes involving a actinic acknowledgment in a substance, which in about-face accept lower activity densities than nuclear reactions. Aqueous nitrogen as an activity abundance has a low activity density. Aqueous hydrocarbon fuels by allegory accept a top activity density. A top activity body makes the acumen of carriage and accumulator added convenient. Convenience is an important agency in customer acceptance. The acceptable accumulator of petroleum fuels accumulated with its low bulk has led to an incomparable success. In addition, a petroleum ammunition is a primary activity source, not just an activity accumulator and carriage medium.

The activity body — acquired from nitrogen's isobaric calefaction of dehydration and specific calefaction in aerial accompaniment — that can be realised from aqueous nitrogen at atmospheric burden and aught degrees Celsius ambient temperature is about 97 watt-hours per kilogram (W-hr/kg). This compares with 100-250 W-hr/kg for a lithium-ion array and 3,000 W-hr/kg for a gasoline agitation engine active at 28% thermal efficiency, 30 times the body of aqueous nitrogen acclimated at the Carnot efficiency.2

For an isothermal amplification engine to accept a ambit commensurable to an centralized agitation engine, a 350-litre (92 US gal) cloistral onboard accumulator barge is required.2 A applied volume, but a apparent access over the archetypal 50-litre (13 US gal) gasoline tank. The accession of added circuitous ability cycles would abate this claim and advice accredit frost chargeless operation. However, no commercially applied instances of aqueous nitrogen use for car propulsion exist.

edit Frost formation

Unlike centralized agitation engines, application a cryogenic alive aqueous requires calefaction exchangers to balmy and air-conditioned the alive fluid. In a boiling environment, frost accumulation will anticipate calefaction breeze and appropriately represents an engineering challenge. To anticipate frost body up, assorted alive fluids can be used. This adds topping cycles to ensure the calefaction exchanger does not abatement beneath freezing. Additional calefaction exchangers, weight, complexity, ability loss, and expense, would be adapted to accredit frost chargeless operation.2

edit Safety

However able the insulation on the nitrogen ammunition tank, there will accordingly be losses by dehydration to the atmosphere. If a car is stored in a ailing aerial space, there is some accident that aperture nitrogen could abate the oxygen absorption in the air and could could cause asphyxiation. Since nitrogen is a achromatic and odourless gas that already makes up 78% of air, such a change would be difficult to detect.

Cryogenic liquids are chancy if spilled. Aqueous nitrogen can could could cause algidity and can accomplish some abstracts acutely brittle.

As aqueous N2 is colder than 90.2K, oxygen from the atmosphere can condense. Aqueous oxygen can spontaneously and berserk acknowledge with amoebic chemicals, including petroleum articles like asphalt.3

Since the aqueous to gas amplification arrangement of this actuality is 1:694, a amazing bulk of force can be generated if aqueous nitrogen is rapidly vaporized. In an adventure in 2006 at Texas A&M University, the pressure-relief accessories of a catchbasin of aqueous nitrogen were closed with assumption plugs. As a result, the catchbasin bootless catastrophically, and exploded.4

edit Tanks

The tanks have to be advised to assurance standards adapted for a burden vessel, such as ISO 11439.5

The accumulator catchbasin may be fabricated of:

steel

aluminium

carbon fiber

Kevlar

added materials, or combinations of the above.

The cilia abstracts are appreciably lighter than metals but about added expensive. Metal tanks can bear a ample amount of burden cycles, but have to be arrested for bane periodically. Aqueous nitrogen, LN2, is frequently transported in cloistral tanks, up to 50 litres, at atmospheric pressure. These tanks, getting non-pressure tanks they are not accountable to inspection. Very ample tanks for LN2 are sometimes pressurized to beneath than 25 psi to aid in appointment the aqueous at point of use.

edit Discharge output

Like added non-combustion activity accumulator technologies, a aqueous nitrogen car displaces the discharge antecedent from the vehicle's appendage aqueduct to the axial electrical breeding plant. Where emissions-free sources are available, net assembly of pollutants can be reduced. Discharge ascendancy measures at a axial breeding bulb may be added able and beneath cher than alleviative the emissions of broadly broadcast vehicles.