SOLTESS Project

SOLTESS is the acronym of SOLar Thermal Energy Solid Storage. It was a project of the Ministry of Education, University and Research PON 2010 (Cod. PON01_00761) from 10/07/2010 to 31/12/2015.
Official site of the project.

Solar plants for the production of electrical energy using thermodynamic cycles exploit different approaches to concentrate the sun's rays, a source of heat at high temperature, on the receiver system. The most popular solutions involve: parabolic tubes and their variants (Fresnel mirrors), central tower systems or multi-tower systems, such as that proposed in the present project. The solar thermal technology (Concentrating Solar Power - CSP) has the following advantages:

• it is possible to accumulate the heat provided by solar radiation, coping the intermittence in the solar irradiation;
• the theoretical yield in the transformation of solar energy into electrical energy is higher compared to photovoltaic systems;
• the electricity production cost is low and decreasing for large size systems.
  

GENERAL OBJECTIVES

This project proposed an energy storage in solid materials, with heat exchangers incorporated in the material or immersed in fluidized beds. The storage medium was localized in the individual receivers of the concentrated radiation, placed on towers with low impact on the landscape. The storage system localized in the receiver was oriented to improve the characteristics of the receiver: low cost, high thermal conductivity, high storage capacity, simplicity of construction, free sizing of the storage. The innovative element of the type of system proposed in this project was represented by the medium of solid storage of the Solar Generating Unit (UGS).

Each UGS included: a field of mirrors (heliostats) for the acceptance and the concentration of solar radiation, with the related control system, which houses a "cell". The cell incorporated a medium of heat accumulation in mixtures of solid material, inside of which is immersed a heat exchanger with a tube bundle. The total area of the mirrors depends on the installation site and on the dimensions of the storage medium, given the operating temperature. The heating of the storage material taken place through an aperture in the lower part of the cell called "receiving cavity", which collected the solar radiation reflected by the heliostats.
The project was aimed at the realization of an innovative solar thermal power plant, declinable in different configurations: power plant, micro-system, plant integrated with fossil fuel power plants. The versatility of the proposed technology constituted a significant strength.

The project also included a training part.

The Solar Collectors Laboratory realized the optical design of the Heliostats field and of the receiver in order to optimize the collection characteristics. Laboratory and outdoor tests were made on materials and components for the construction of the Solar Generating Unit (UGS). The Lab staff also participated in the training part, linked to the project.