Comparsion Of Diesel Fuel Versus Hydrogen Fuel

Introduction

In this report diesel fuel and hydrogen fuel will be compared to one another. Diesel fuel is used in internal combustion engines for passenger cars, vans, buses and trucks. Hydrogen can be used as a fuel in internal combustion engines in vehicles as well as fuel cell vehicles. According to stats.beepbeep.ie, so far in 2020 in Ireland diesel makes up 43.79% of new passenger cars sold when categorising vehicle sales by engine type. There is no statistics for any hydrogen fuelled cars being sold in Ireland so far in 2020.

Production of fuel, source, land requirements and cultivation

Diesel

Diesel fuel that is used in engines is refined from crude oil. When beginning the refining of crude oil, the oils’ temperature is raised above 400 degrees Celsius. This makes the liquid oils’ turn into vapour. The vapour is then put into a fractional distillation tower. While the vapour is rising, its temperature begins to drop. When this vapours temperature has dropped below a certain point the hydrocarbon chains in it turn back to liquid. Distillation plates installed in the tower capture the liquids as they appear. Long hydrocarbon chains only reach their boiling point when they exceed 400 degrees Celsius. When these chains are in the distillation tower, they convert back to liquid. This then exits at the bottom of the tower in the form of asphalt or bitumen. Short hydrocarbons start to turn to liquid as the vapour rises. As this vapour drops in temperature below 370 degrees Celsius, fuel oil emerges. This process continues in the tower the further up the vapour rises resulting in different distillates emerging as the vapours temperature drops. Diesel fuel starts to emerge when the vapour temperature is between 200 and 350 degrees Celsius. This is collected on distillation plates and it gets siphoned off and gets stored in a diesel holding tank.

Hydrogen

Hydrogen can be produced from many different sources such as biomass, nuclear power, natural gas and renewable clean power such as wind and solar power. The methods that are used to convert these sources into hydrogen fuel are electrolysis, thermal, solar-driven and biological processes. Electrolysis is when water is split into hydrogen and oxygen. This process is carried out in an electrolyser, that works as a fuel cell backwards. A fuel cell uses the energy from a hydrogen molecule whereas an electrolyser extracts the hydrogen from water molecules. The thermal process for producing hydrogen is done through steam reforming. This is “a high-temperature process in which steam reacts with a hydrocarbon fuel to produce hydrogen”. The hydrocarbons that are used to make hydrogen are natural gas, gasified biomass, gasified coal and renewable liquid fuels. These days approximately 95% of hydrogen is produced from steam reforming of natural gas. Light is used as an agent to produce hydrogen in a solar-driven process. The three different solar driven processes are solar thermochemical, photoelectrochemical and photobiological. Production of hydrogen using the solar thermochemical process involves concentrated solar power driving water splitting reactions usually with things like metal oxides. Hydrogen and oxygen are split from water by specialised semiconductors in the photoelectrochemical process. Whereas in photobiological processes the natural photosynthetic activity of green algae and bacteria is used to produce hydrogen. Hydrogen can also be produced in biological processes using microbes like microalgae and bacteria. Hydrogen is produced when the microbes break down organic matter such as wastewater or biomass in these microbial biomass conversions compared to the microbes using sunlight for energy in the photobiological process.

Fuel Standards

All fuels for vehicles and machinery, whether they are for road use or not, have to meet strict standards with regards their content. This is to protect human health and the environment as much as possible from the hazardous fume’s these fuels they will produce when burnt in an internal combustion engine due to their chemical contents. As Ireland is part of the European Union, we have to abide by the fuel standards set out under European Union law.

Diesel

Diesel fuel in Europe is specified by the standard EN 590.

The main goal of the introduction of these standards was to reduce the sulphur content of diesel fuel. Sulphur acted as a lubricant in the diesel fuel. The aim is to replace it with special additives in Ultra Low Sulphur Diesel. These EN 590 standards have been around since 1993 and often get updated.

Hydrogen

Hydrogen as a fuel is not as widely used in the transport industry at the moment, especially in comparison to diesel, and as a result of this I have had great difficulty in trying to source the fuel standards of hydrogen fuel. I have failed to find a table of standards as good as table 1 in this report relating to the chemical composition of hydrogen fuel. It may be due to the fact that hydrogen is a pure element on its own and therefore should not contain any sulphur. Sulphur reduction is the main goal of having the European standard for diesel fuel and this may be the reason I am unable to find a table of this kind for hydrogen fuel. However, what I was able to find was a table of the characterises for hydrogen, some of these characteristics will relate to some of the properties of diesel fuel as well for example the density of each fuel.

Fuel system considerations, technical, on vehicle, fuelling infrastructure.

Diesel

On Friday the 24th of May 2019 an article titled “Extortionate rate hikes mean dozens of local service stations face closure” (Hutton, 2019) appeared in The Irish Times, the author was Brian Hutton. Why this article is important to this report is the fact that it states that “There are about 1,500 petrol stations left in Ireland.” ) The vast majority of these will most likely sell diesel as well as petrol. I am mentioning this because I think this goes to show that there is a large fuelling infrastructure for diesel fuel in Ireland. This is not the case with hydrogen fuelling infrastructure at the moment, however there are plans to change this.

Hydrogen

On Thursday the 26th of September 2019 an article titled “Plan for 80 hydrogen fuel stations for Ireland by 2030” appeared in The Irish Times, the author of this article was Neil Briscoe. This article is very relevant to this research report as it states that “Currently, only two hydrogen fuelled cars are available on the market – the Toyota Mirai and the Hyundai Nexo – and neither is sold in Ireland, for the simple reason that there is currently nowhere to refuel them.” This article also talks about the plans to build hydrogen fuel stations in the next 10 years. This article points out the current lack of hydrogen fuelling infrastructure in Ireland which is a stark contrast to the wide availability of diesel refuelling infrastructure in Ireland.

Energy calculations relating to usage /comparisons

Diesel

The energy density of diesel fuel, that is used for automotive, is 38.6 Mega Joules per Litre. To get this as Mega Joules per Kilogram we take the density of diesel as 820 kilograms per cubic metre at 15 degrees Celsius, which means in it is 820 grams per litre. There is 1000 grams in 1 kilogram. So, 38.6 Mega Joules divided by 820 grams and then multiplied by 1000 grams means that diesel has an energy density of 47.07 Mega Joules per Kilogram.

Hydrogen

The energy density of hydrogen is 142 Mega Joules per Kilogram.

So, in comparison hydrogen is much more energy dense than diesel, 94.93 Mega Joules per Kilogram to be precise.

Fuel cost comparisons

Diesel

At the time of writing this, the current average price of diesel fuel in Ireland is €1.32 per litre. This is calculated by adding the lowest recorded price (€1.039 per litre) and the highest recorded (€1.598 per litre) and then dividing the answer (€2.637) by 2 giving you €1.3185 per litre. (myLPG.eu, 2020) Now one issue is that diesel is sold by the litre and hydrogen is sold by the kilogram. However, we can overcome this problem by converting the price of diesel in euros per litre to euros per kilogram. Again, the density of diesel is 820 kilograms per cubic metre at 15 degrees Celsius, which means in it is 820 grams per litre. There is 1000 grams in 1 kilogram. So, €1.32 divided by 820 grams, multiplied by 1000 grams = €1.61 per kilogram of diesel.

Hydrogen

As hydrogen fuel for vehicles is not available in Ireland at the moment I have looked into the price per kilogram of hydrogen in the UK, as they are our nearest neighbour who have hydrogen fuel on sale. According to an article titled “Hydrogen cars: How the fuel cell works, where the UK's filling stations are and how expensive they are to run”, that appeared in the Sussex Express on Wednesday the 5th of March 2020, “In the UK, hydrogen fuel costs between £10 and £15 per kg”. (Allan, 2020) So, I will take the average price to be £12.50 per kilogram (£10+£15=£25/2=£12.50). Now this figure is in Pounds Sterling, so I put this into Google and found that this converts to €13.24 per kilogram, going by the currency conversion rate at the time of writing.

So, in summary diesel costs €1.61 per kilogram and hydrogen costs €13.24 per kilogram. Hydrogen is €11.63 more expensive per kilogram.

Environment

Diesel

Unfortunately, when diesel fuel is used to power an internal combustion engine there are some emissions produced that get released into the atmosphere and have a harmful effect on the environment and human health. If complete combustion is achieved the only emissions that would get produced would be carbon dioxide (CO2) and water vapor (H2O). But unfortunately, in the real world this is not always the case and we end up getting even more polluting emissions from the diesel engine such as particulate matter, carbon monoxide (CO), hydrocarbons and nitrogen oxides (NOx).

Carbon dioxide (CO2) is bad for the environment as it is leading to the global temperature rising which is melting the ice caps and is causing sea levels to rise. It is also leading to more unpredictable and extreme weather types and storms globally. Water Vapour (H2O) is harmless. Particulate matter should get contained and dealt with by the diesel particulate filter (DPF). Carbon monoxide (CO) is poisonous to humans and can be fatal this is why it should not be released into the open air. Nitrogen oxides (NOx) are bad for both the environment and human health. They can lead to the formation of smog and can lead to the development of acid rain when they mix with other chemicals and substances in the atmosphere.

Hydrogen

Now there is good news and bad news about the effects of hydrogen fuel usage for the environment. The good news is that burning hydrogen in an engine or fuel cell with oxygen will only produce water (H2O) and warm air. These will not harm the environment or human health. The bad news is that hydrogen is often produced from resources that include the burning of fossil fuel and these obviously produce harmful emissions like those of a diesel engine. However, hydrogen fuel can also be produced from clean energy sources such as solar and wind energy. So, when the world moves towards eliminating the use of fossil fuels more and more hydrogen fuel will be produced from an emission free source which would mean a hydrogen powered vehicle, could in theory, be completely emission free.

Pros and Cons of each fuel

Diesel

• + Diesel refuelling points are very widespread
• - Diesel emissions are harmful to the environment and human health
• + Diesel vehicles are cheaper than hydrogen vehicles
• - Diesel taxes are always increasing so running costs will increase over time
• + Diesel fuel is cheaper per kilogram than hydrogen
• - Diesel vehicles resale value will be low in the coming years as more people are switching to cleaner alternatives

Hydrogen

• + Hydrogen vehicles release no harmful emissions
• - There are no refuelling points for hydrogen in Ireland and there is plans for only 80 of them by 2030 in comparison to about 1500 fuelling stations at the moment
• + The energy density of hydrogen is much higher than diesel, so a hydrogen tank actually contains a lot more energy than a diesel tank
• - Per kilogram hydrogen is much more expensive than diesel and the refuelling time of hydrogen is slightly longer than that of diesel
• + The price of hydrogen vehicles will reduce the more people are buying them and there will be government grants towards buying them as they are zero emissions
• - The current price of hydrogen vehicles is very high in comparison to diesel vehicles and there are very few options of models available to purchase