TECHNICAL AREA Project: System to produce Hydrogen

Due to the difficulty of administrating the wind energy put into the network by wind turbine generators, and to the fact that it is not easy to store its mechanical energy (torsor pair of the axis), the technological developments to correct this variability are focused on : prediction and storage of electrical energy which the wind farm puts into the network.

As electrical energy is not storable, it is tried to store the chemical energy obtained by the reaction of some compounds, in presence of intensity. If the chemical reaction is reversible, which means that the initial pair of compounds can be obtained by the flowing of electricity through the resulting products of the direct reaction, then the chemical pair will be useful for the storage of electrical energy.

The chemical pair that provokes nowadays the most technological interest in the storage of electrical energy is hydrogen-oxygen. Both form the water molecule (H2O) and can be obtained by electrolysis (discomposition through electricity). The posterior combination (H2+O2) to form water gives back part of the energy absorbed in the previous electrolysis.

The main advantage of the pair H2-O2 over other ones is that only hydrogen has to be stored, as oxygen can be taken from the atmosphere, of which it is a part of 20%.

The most traditional way the energetic content of hydrogen has been used is in combustion with oxygen, since this can be done in an explosion engine. Nevertheless, the technology that has revolutioned the use of hydrogen is the fuel battery.

In the spring of 2005 a treaty was signed between Gas Natural and the Ministry of Innovation, Industry and Commerce of the Galician Government in order to develop a pilot project to store wind energy through chemical energy.

This project will be fulfilled in the installations of the Experimental Wind Farm Sotavento and will have a storage plant of wind energy that will use hydrogen at a scale that, without being the one that solves the variability of generation, allows making experiences in real operations that may easily be extrapolable to design global solutions.

The production of hydrogen will be obtained by an electrolyzer of 60 Nm3/h, which works on electricity from wind turbine generators. The electrolyzer will produce hydrogen at low pressure, which will later be compressed to reduce the volume of storage in steel cylinders at about 200 bar. For the following conversion into electrical energy, a motogenerating equipment of 60Kw electricity will be used.

Both systems (electrolyzer and motogenerator) are designed for a complete assembly in a container which can be installed outside and which will not need great constructions.

A motogenerator group with explosion engine has been used, as the aim of the project is to experiment with the use of H2 for wind energy and a fuel battery would add technological risks in face of an engine whose technology is well-known.

Working of the storage of wind or renewable energy

A possible way of storing the electrical energy generated on a wind farm consists in transforming it into hydrogen.

The electrical energy that we want to store is driven towards an electrolyzer, which is a device in which electricity dissociates water into its two components: oxygen (O2) and hydrogen(H2) according to the reaction H2O ? H2 + ½ O2. The H2 obtained is compressed to make its storage easier while the O2, which has no energy, is put into the atmosphere, which it is already a component of.

The H2 is stored in containers under pressure until the moment when it is used to generate electricity in situations of demand or need.

In this case, H2 is used as a fuel in a group of electricity generation, whose engine is similar to the ones of natural gas adapted to hydrogen. The engine takes atmospherical air, whose oxygen, in proportion of 20%, is the one that reacts with the H2 of the cylinders, provoked by the spark of the spark plug.

The combustion of H2+O2 only liberates water in an inverse process to the one produced inside the electrolyzer.

The crankshaft of the engine drives a generator that once again produces energy which is put into the network.

The different stages that take place along the project are:

1. Equipment election and previous analysis:
   It is necessary to evaluate all equipments that are nowadays on the market of hydrogen, as well as the different requirements of the water that enters the system in order to fit it and let it be used by the electrolyzer.
   
   In this stage the most important equipments are bought:

   -	Electrolyzer and systems of water filters
   -	Motogenerator equipment of electricity through accumulated hydrogen
   -	Systems of hydrogen storage

2. Integral development of the project according to the equipment:
   The execution project is developed and the construction is dimensioned
3. Execution of the construction:
   Prepare the construction to hold all the equipment and establish the different services: generation line from the wind turbine generators, water supply and communication line
4. Installation of the elements and start:
   Situate all selected components of the project and start the whole system
5. Evaluation of the whole system by applying different states:
   In this stage the system will be evaluated to be used in the following conditions:

   -	Absorb wind energy in generation and deliver energy with low winds
   -	Absorb energy to reduce positive market deviations and deliver in negative deviations

The present project between Gas Natural and the Ministry of Innovation, Industry and Commerce of the Galician Government , in the installations of the Experimental Wind Farm Sotavento.