Promoting hydrogen fuel cell vehicles

K C Somaratna Managing Director, Somaratna Consultants

According to a AFP news item published in the Daily News of January 17, the top three automobile manufacturers in Japan along with Japanese energy groups are planning to promote hydrogen fuel cell vehicles as a greener alternative to the current modes of transportation.

A cutaway view of a fuel cell vehicle

A careful scrutiny of pros and cons of this seemingly harmless promotion with a comparison using its impacts on a combination of global warming and climate change will indicate that this alternative is not that harmless and lags far behind renewable energy enabled battery electric vehicles.

Normal road vehicle transportation using an internal combustion engine (ICE), as we practise today, contributes to climate change due to their emission of (a) waste heat (b) carbon dioxide and (c) water vapour.

Both the IPCC. TAR 4 and other authors do consider this anthropogenic heat generated as trivial quoting from a publication by N Nakicenovic et. al. dated 1998.

Although this waste heat from man-made initiatives may be small compared to the solar heat received or absorbed or reflected, this waste heat is a very high percentage of the energy consumed by mankind.

According to the IPPC report, while we have consumed 247.0 EJ of energy in 2004 we have wasted another 220 EJ, and the future generations will have to starve of energy as a direct result of this wastage.

This wastage is most pronounced in respect of road transportation using ICEs.

According to the report "On the Road in 2035" Published by Massachusetts Institute of Technology, we consume about 2.85 MJ/km in a Toyota Camry type vehicle using an ICE while the equivalent electric vehicle will need only 0.58MJ/km which goes to show that more than 75 percent of the energy we consume in driving an ICE goes waste.

It is the intention of the writer to compare the hydrogen fuel cell vehicle (HFCV) with three other options - the currently used ICEs, grid enabled battery electric vehicle (GEV) and renewable energy (solar energy) powered battery electric vehicle (REV) using the emission levels of the above mentioned three pollutants as the criteria.

Before this comparison is presented, one needs to understand how these three alternatives are powered.

In the case of hydrogen fuel cell vehicle, the hydrogen and oxygen (from air) is made to react in a fuel cell, thereby yielding the energy to drive the vehicle. This hydrogen to be used can be made either by centralised or distributed steam reforming of natural gas or by the electrolysis of water using main grid electricity.

The amounts of waste heat, water vapour and carbon dioxide generated as a result of this generation of hydrogen would thus depend on the process used and in the comparison given, the hydrogen is assumed to be generated by distributed steam reforming of natural gas. In the grid enabled battery electric vehicles, the batteries of the electric vehicles are recharged using electric power from main grid electricity and in the renewable energy powered electric vehicles, the batteries of the electric vehicles are recharged using electric power generated using a renewable source like PV solar panels.

In calculating these values, the writer has used data given in Tables 6,7 and 28, and figures 53 and 54 of "On the Road in 2035" and the following assumptions:

(a)Gasolene consist of 90 percent carbon and 10 percent hydrogen.

(b)Percentage of energy wasted to energy in the tank of ICE engine is 75 percent

(c)All CO2 quoted in above mentioned Tables and corresponding to the hydrogen fuel cell.vehicles do come from combustion of methane or a fossil fuel

(d)In battery electric vehicles no energy is generated nor wasted from the tank to wheel phase.

(1) Figures are based on average mix of power generation in USA.

(2)Figures are not readily available as quoted in literature.

From this Table it could be seen that when we shift from gasolene driven ICEs to hydrogen fuel cell vehicles there is about 70 percent reduction in waste heat, 65 percent reduction in carbon dioxide emissions, but 20 percent increase in water vapour.

One might ask now, what harm would this additional water vapour do to mankind or to climate change. The real answer to this question is "we really do not know".

In respect of water vapour the common pronouncements found in literature, on which there is general agreement, are as follows:-

(a)Water vapour is a key component in the atmosphere.

(b)Water vapour's green house effect is about twice that of carbon dioxide.

(c)Relative humidity of atmosphere does not change with climate and when temperature increases more water vapour gets into air to keep the relative humidity constant.

(d)The effect of water vapour on global warming is considered as a feed back effect rather than a direct radiative forcing effect because the lifetime of water vapour molecule is only a few weeks compared to the few decades for a carbon dioxide molecule.

While the last statement may be true for other sources of water vapour like evaporation from the oceans or from plants or from agriculture, this water vapour from transportation differs from the water vapour from above mentioned sources in respect of two aspects.

First is that water vapour from transportation gets into the atmosphere at much higher temperatures than the case for conventional origins and the other is that this is not water from the biosphere, hydrosphere, cryosphere, atmosphere or from the land surface; but contains newly formed water resulting from combustion of a fossil fuel which were present in nature in the form of a molecule containing hydrogen and carbon.

Anyhow in a scenario in which (a) the annual precipitation has increased from 1994 to 2006 at a staggering rate of 240 km3 per year per year, as reported in a recent research paper published in August, 2010 and (b) precipitation related disasters has already affected Sri Lanka, Philippines, Brazil and Australia, any solution which would enhance water quantity in the climate system should not be encouraged.

On the other hand, the report "Transport Scenarios and Policies to 2050" issued by the World Energy Council computed in its Appendix II how much a gallon of gasolene equivalent of hydrogen would cost if the hydrogen is to be obtained by electrolysis and using a value of 44 MJ for the energy equivalent of gallon of gasolene, they arrived at a value of US$ 2.44 for gasolene gallon equivalent of H2.

When they added the global hydrogen infrastructure cost of US$ 1 trillion (rough estimate of a number of studies) with a 30-year amortisation period for supplying a 5 percent hydrogen fuel cell penetration in 2050, the amortisation cost was found to be US$ 2.38 per gasolene gallon equivalent of hydrogen and total cost came to US $ 4.82 per gallon of gasolene equivalent of hydrogen.

Our computations indicate that if we invest US$ 1 trillion on a renewable energy based electric vehicle infrastructure with a twenty year amortisation period, the amortisation cost of gasolene litre equivalent of electricity will be US $ 0.40 only for nearly double the level of penetration.

As such if funds are available for mobilisation on a greener alternative to gasolene, renewable energy powered electric vehicle infrastructure would be more profitable and beneficial than a hydrogen fuel cell based infrastructure, and in fact will be the ideal solution.

When one looks at the Table above it could be clearly seen that the electric vehicles powered by renewable sources of energy like solar energy will be the best mitigatory path to be followed in order to prevent global warming or climate change due to transportation.

It is the writer's contention that natural gas - predominantly methane with one carbon atom and four hydrogen atoms - should not be burnt as fuel; but should be used to make other more valuable compounds like polymers or to make something like urea - which again has one carbon atom and four hydrogen atoms combined with one oxygen atom and two nitrogen atoms thereby enhancing the concentration of oxygen in the atmosphere.