THE energy situation in Latin America has forced all the countries of the region to consider renewable sources of energy. In 1996 around 60% of the primary energy used in Cuba came from oil and 90% of electricity was generated by burning oil.
Cuba now needs to reduce the amount of oil it uses for energy production. The ultimate aim is to achieve total energy independence and to guarantee sustainability in energy production. To reach this goal it is necessary to make use of all the country’s renewable resources and an action plan has been developed for hydro power development.
The hydro power plan forms part of a government programme under the Science, Technology and Environment Ministry on ‘Sustainable Energy Development’. On the hydro side this programme includes a National Technical Scientific Programme to develop hydraulic turbines. The programme focuses specifically on axial turbines, beginning with basic scientific research and moving on to project development and production.
The programme has an unavoidable social dimension, as the construction of the hydraulic turbines is intended to supply electricity both for isolated communities and the general population connected to the national grid.
The history of hydro development
In the 1980’s, various decisions taken in Cuba to reinforce its energy industry gave a boost to the country’s hydro industry. As a result of these decisions, a development plan was laid out that directed work on electrification and extension of the grid in accordance with hydro power development. The table right list the plants built under this initiative.
Since the electrification programme began, hydro has continued to be increased progressively and there have been big advances in the use of this renewable energy source. In most cases, power stations have been installed at existing irrigation dams. Annual hydro generation has increased in the second half of the 1990s by exploiting these existing reservoirs and the revenue for the electricity generated.
Cuba now has 176 power stations in operation. Together they have an installed capacity of 57.3MW and generate around 90GWh/year. They supply electricity to 18600 domestic properties and 4500 companies. They have allowed electricity to be brought to many isolated communities and many are still not connected to the national grid.
Studies carried out by international organisations suggest that hydro and small hydro potential will allow electricity on localised grids to be extended to a further 6% of the rural population. This extension is already under way. A series of small hydro projects, which will guarantee a total installed power of 6600kW and generate some 37600MWh per year, is currently under development.
Including plants now planned, Cuba’s total gross hydro power potential was estimated in the most recently completed studies at 14600GWh/year. This hydro power resource is particularly valuable to the country’s energy balance because of its stability and autonomy, its operational advantages and its many locations throughout the country.
Much of this capacity is available at Cuba’s 219 existing reservoirs. Constructed for water management, irrigation or other reasons, most of these are suitable for hydro power generation.
Of particular importance from the point of view of turbine deployment is the fact that out of all these reservoirs more than half – 141 – can be equipped with axial turbines . This standardised hydraulic turbine has already been installed at the small central hydroelectric plants listed on the table on page 26. Further development of these turbines is now planned as a major part of the programme to develop hydro potential on a national scale.
Developing axial turbines
In the case of axial turbines, no previous development of the technology had been made in Cuba and initially there was no knowledge base to begin production. As a result it was impossible to implement effective models to exploit the country’s hydroenergetic potential. The only way – or at least the most scientific way – to proceed was to develop a knowledge base that would allow the development of families of turbines, based on an effective methodology and employing, as far as possible, advanced technologies. These families could then be deployed at various sites.
Taking as a base the standardisation of an axial hydro turbine published in 1994, development work began in 1998. The project was titled ‘Investigation and development of the family of tubular axial turbines A1 for small central hydroelectric plants’ and was financed by the Science, Technology and Environment Ministry.
Cuba had previously employed two families of axial turbines. In deciding on the standardised version the highest priority was given to the so-called ‘A1’ design. The A1 was selected because this family can embrace a bigger number of hydro power objectives, construction of the various turbines is feasible for Cuban fabrication companies and since it does not require high technological complexity it can be produced at a national level. Finally, this group has excellent efficiency characteristics which will allow Cuba to make the most effective use of its hydro power potential.
The object of the current phase of work is to obtain a model example of a tubular axial turbine to use as a basis for development of the reminder of the family. It must offer guaranteed results when it is deployed and must allow efficient construction. Determination of the dimensions of the model to build is therefore of great importance.
The parameters of the A-1 family are obtained from a general selection graph. The unitary parameters of the turbine to be built are shown in the table above. These parameters guarantee that the turbine designed belongs to the family A-1.
The specific parameters of the model built are shown in the table below. This version is already built and ready for the next phase of development – a series of tests that will allow researchers to determine the experimental coefficients for the family, to develop a series of plants of corresponding diameters. The turbine was designed and built by the Center for the Study of Thermoenergetics (CETA).
The design and the construction of the turbine allowed Cuban organisations to develop methodologies for the design of tubular axial turbines. Starting from these procedures, it will be possible to design members of the axial turbine family A1 with six different sizes of rotors, as required for the project above, and also to set down the basis for construction of 88 axial turbines that are required to meet the ‘social objectives’ of the standardisation programme.
When it comes to installation of the model, two alternatives have been evaluated. In the first case, the equipment would be connected to the grid using an asynchronous generator. This variant reduces the costs of the generation system and at the same time can increase capacities in the area where the turbines are sited, contributing to decentralisation of energy production. In the second case the equipment would be sited in an isolated region which has not yet been connected to the grid. In this case it will be used as a synchronous generator and will employ an electromechanical system to regulate the frequency of the electricity generated.
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