Abstract
Benchmark refrigeration systems in the road transportation sector are powered by diesel, having operation costs of up to 6,000 €/y with the consequent increase of the goods cost. This chapter presents an alternative refrigeration system based on fuel cells (FC) and hydrogen as fuel, with higher efficiency, reduced costs and independent of diesel price fluctuations. Examples of the energy load profiles impact on the FC sizing, H2 consumption and system autonomy are presented as well as a description of the FC model and performance simulation results. The economical feasibility of this new refrigeration system linked to renewable energies is also analyzed and an economical assessment for different scenarios is presented.
TopBackground
The road freight market in the EU is currently recovering from the deep economic crisis of 2008/09 which greatly reduced transport activity. In 2010, road freight transport activity in the EU, measured in tonne-km, was roughly 3% higher than in 2009. However, this followed a fall of 2% in 2008 and another 10% drop in 2009 which leaves road freight transport activity in the EU still about 9% below pre-crisis levels of 2007. This development has not been uniform throughout the EU though. The distribution of the inland freight transport in Europe in 2010 is shown in Figure 1.
Figure 1. Distribution of the Inland freight transport in Europe in 2010. Source: European Commission.
According to some analysis developed by the European Commission, the road transport sector contributes hugely to the European economy: it provides about 4.5 million jobs and generates a turnover worth about 1.6% of EU gross domestic product. Moreover, most of the freight deliveries begin and end with a trip on the road. Road transport therefore also plays a vital role in the development of Europe’s integrated transport networks and intermodal transport solutions.
The distribution of road freight transport activity by distance class reveals that more than half (55%) of all goods in terms of their weight are not transported more than 50km. Three quarter of all goods are not transported more than 150 km. It is in these distance brackets where road transport has no economically viable competing mode of transport. Only around a quarter of all goods are transported over distances greater than 150km.
Refrigerated road transport contributes largely to the whole goods road transport; depending on the Member State shares can range from 35%-60% of the heavy-duty vehicles.
Heavy duty trucks typically use diesel engines, whose fuel cost has been estimated to be around 38% of the total yearly direct costs (Ministerio de Fomento, 2013). Refrigeration units are currently based on auxiliary diesel engines and use additional diesel to feed the refrigeration system, increasing the fuel consumption in about 12% (MdF, 2013).
The interest about hydrogen as a low emissions fuel for energy applications has sharply increased the last years leading to the so named the “Economy of Hydrogen”. This chemical reactant has become a versatile fuel with the additional capability of being obtained from many sources including renewable energies.
The 96% of the current hydrogen is obtained from fossil fuels, by natural reforming or oil cracking, and used on site in petrochemical plants, pharmacy or other chemistry related industries. But a 4% of the gas is obtained by water electrolysis which consists in breaking water in an electrolyser by using electricity as energy source.
Key Terms in this Chapter
Electrolysis: A process in which a chemical change, especially decomposition, is brought about by passing an electric current through a solution of electrolytes so that the electrolyte's ions move toward the negative and positive electrodes and react with them. If negative ions move toward the anode, they lose electrons and become neutral, resulting in an oxidation reaction. This also happens if atoms of the anode lose electrons and go into the electrolyte solution as positive ions. If positive ions move toward the cathode and gain electrons, becoming neutral, a reduction reaction takes place. Electrolysis is used for many purposes, including the extraction of metals from ores, the cleaning of archaeological artefacts, the coating of materials with thin layers of metal (electroplating) and the hydrogen production from water decomposition.
Fuel Cell: An electrochemical device that produces electricity by combining a fuel, usually hydrogen, with oxygen. In this reaction, electrons are freed from the hydrogen in the fuel cell by a catalyst, and gain energy from the chemical reaction binding hydrogen and oxygen; this provides a source for electric current. The exhaust of hydrogen fuel cells consists simply of water. Fuel cells are currently used in spacecraft, and increasingly in ground transportation, with potential use everywhere electricity is required.
Modelling: A computer model refers to the algorithms and equations used to capture the behaviour of the system being modelled. This enables to determine some behaviour or property of the original system avoiding the need of performing real tests. The external data requirements of simulations and models vary widely. For some, the input might be just a few numbers (for example, simulation of a waveform of AC electricity on a wire), while others might require terabytes of information (such as weather and climate models).
Battery: An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work. Primary (single-use or “disposable”) batteries are used once and discarded; the electrode materials are irreversibly changed during discharge. Common examples are the alkaline battery used for flashlights and a multitude of portable devices. Secondary (rechargeable batteries) can be discharged and recharged multiple times; the original composition of the electrodes can be restored by reverse current. Several different combinations of chemicals are commonly used, including lead–acid, nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and lithium ion polymer (Li-ion polymer). Rechargeable batteries come in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network.
Hydrogen: Hydrogen fuel is a zero-emission fuel which uses electrochemical cells, or combustion in internal engines, to power vehicles and electric devices. It is also used in the propulsion of spacecraft and can potentially be mass-produced and commercialized for passenger vehicles and aircraft. In a flame of pure hydrogen gas, burning in air, the hydrogen (H2) reacts with oxygen (O2) to form water (H2O) and releases heat. Nevertheless, hydrogen is an energy carrier, like electricity, not an energy resource.
Electrolyser: Electrochemical device where water electrolysis takes place. Redox reactions are the inverse ones that happen in the Fuel Cells, it means that water is decomposed into hydrogen and oxygen.
Renewable Energy: Renewable energy is generally defined as energy that comes from resources which are naturally replenished on a human timescale such as sunlight, wind, rain, tides, waves and geothermal heat. Renewable energy replaces conventional fuels in four distinct areas: electricity generation, hot water/space heating, motor fuels, and rural (off-grid) energy services. Renewable energy resources exist over wide geographical areas, in contrast to other energy sources, which are concentrated in a limited number of countries. Rapid deployment of renewable energy and energy efficiency is resulting in significant energy security, climate change mitigation, and economic benefits.