HYDROGEN, A HOPE IN THE WORLD OF ENERGY

Cecilia Smoglie

Versión español

Energy as a global challenge

The World Energy Council (WEC) has stated that the economic development , as it is understood at present, is unsustainable due to three reasons: generation of exclusions, contamination of the environment, and unrestricted use of non-renewable resources. It has also mentioned that it is urgent to provide stable, distributed, affordable energy with minimal environmental impact in order to address these three serious matters. It concludes that this challenge adds to the steady growth of the energy global demand. Hence, it is essential to work altogether to increase the Energy Efficiency (EE) and the Rational Use of Energy (RUE), defined as follows: EE = obtained energy + inverted energy to obtain it < 1 RUE = necessary energy + actual consumed energy ≤ 1 The theoretical limit of EE is physically lower than 1, but this fraction is likely to increase if innovation and technology are applied. On the other hand, the theoretical limit of RUE is 1, but to approach this value, each good or service consumption such as electricity, oil, water, paper, chemicals, must be the strictly necessary one. Then,waste should be avoided without sacrificing comfort. This requires a cultural change that starts at home and is developed at school, university, the business field , the government. Only focused on EE and RUE, the most delicate transition of all the times at a global level will be achieved : the sustainable development.

 Use of renewable sources of energy

It is a fact that renewable sources of energy are not mostly used. It is frequent to pay expensive and inefficient fuel transport in islolated areas that are not connected to the electricity or gas network due to the fact that local sources of energy like the wind, sun, rivers and so on, are not exploited. Patagonia is a clear example of this situation because several settlements or farms use diesel generators. However, a high potential of local wind energy is available there. In areas connected to the conventional system, the local renewable sources of energy are wasted too. The intermittence of natural resources, such as wind and sun, makes it difficult to generate electricity and control tension supply. As a solution to this problem, the conventional system is expanded and the intermittent contribution of the plants is limited. Nevertheless, the shortening of this contribution is not only incompatible with the necessary technical limits to expand the system and the growing energy demand but it also poses a threat to the productivity of wind and solar plants. There are two ways of dealing with this dilemma : – to develop systems with large capacity to store energy and suitable to absorb energy surplus when there is some spare wind and sun – to provide electricity when the resource is lower than the demand. The design of these systems to balance demand and supply, must also guarantee efficiency, reliability and affordable costs.

 Hydrogen, energy and clean fuel storer

Any electric energy surplus, whatever the generation source might be, can be used to produce and store hydrogen that eventually will power an electricity generator . Pure hydrogen or hydrogen mixed with CNG, biogas and so on is a fuel suitable for heating, oven, cooker, injection in the gas network and particularly for running electricity generators with Otto cycle engines. Storing hydrogen is more efficient than using batteries because the latter have limited charge, are heavy and short-lived. They are contaminating waste too and the treatment to dispose of them ecologically implies a high level of energy consumption. Hydrogen, in its free form, hardly exists in natural state. It is mainly generated through the reforming of natural gas, petrol, fuel and coal – all of them non nonrenewable resources- or else through thermochemicals of biomass or similar ones. However, relevant quantities of greenhouse effect gases can be released through these processes. The use of electrolytic reactors that dissociate the water molecule into hydrogen and oxygen is one alternative to reduce emissions. In the subsequent hydrogen combustion, the water molecule is restored and heat is obtained. Although the technologies to produce, store and use hydrogen are known and to a great extent, easy to handle, the challenge implies assembling robust, reliable and competitive systems.

 Auto-pressurized alkaline electrolysers

Energy per unit of hydrogen mass is 3-6 times higher than the one of any other fuel, but in its gaseous phase it is the least dense of all. Therefore, in order to have enough energy in manageable volumes, the gaseous hydrogen must be stored at a pressure of 700 bar or more. Most of the comercial electrolysers produce hydrogen at pressures in the range of 1-30 bar. The subsequent compression of hydrogen up to 700 bar is an expensive and inefficient process that consumes a high percentage of available energy in the stored hydrogen. To overcome this limitation, the Technological Institute of Buenos Aires (TIBA) has developed auto-pressurized alkaline electrolysers that make it possible to produce and store hydrogen at high pressures without needing compression stages. It reduces costs, improves security and doubles energy efficiency of the whole process. Innovation in tanks for hydrogen at high pressure

In order to store hydrogen at high pressures, the TIBA has developed a new tank concept that replaces the conventional cylinder. Details have been omitted due to confidentiality reasons but its advantages are the following : – high resistance to internal pressure – less weight and cost – conventional, recyclable material, damage-free by hydrogen and corrosion – higher heat transfer towards the environment during the filling process. – gradual gas release through breakage, which avoids the ignition around leak points . – size and shape adaptable to available spaces, even in vehicles. Otto cycle engines powered by hydrogen

The TIBA is studying hydrogen combustion in Otto cycles based on its experience in conversion of diesel cycle engines into Otto cycle ones run on gas. The hydrogen is a good alternative to petrol because it has : – high caloric value and carbon-free – high octane rate which allows efficiency through a great compression relationship – wide range of ignition making it possible to use poor mixtures and have combustion at temperatures that inhibit the formation of nytrogen oxides.

Stable, distributed, affordable energy with minimal environmental impact The WEC recommends that if aeolian and solar energy were available, the hydrogen technologies described above would be able to combine in order to provide stable, distributed and affordable energy with minimal environmental impact. The aim is to design and build a system that integrates aerogenerators and photovoltaic solar panels, electrolysers, hydrogen storage, Otto cycle engine powered by hydrogen, a small local electric network and a control system of the whole project. This pilot plant, designed to provide isolated areas with electricity and heat, must be modular, robust, reliable and reproducible on scale. The TIBA moves forward towards the achievement of this objective , encouraged by its leadership in hydrogen technologies and control systems.