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MOdular high concentration SolAr Configuration

Periodic Reporting for period 3 - MOSAIC (MOdular high concentration SolAr Configuration)

Reporting period: 2019-06-01 to 2021-11-30

Seeking affordable and 100% clean energy supply.

Photovoltaic panels are the most common technology today for converting the sun's rays into electricity, but when it comes to storing that energy and meeting a fluctuating demand, other solar technologies are more suitable. Concentrated solar power, or CSP, is a technology able to store solar energy efficiently and cost-effectively. However, its full development and mass market penetration continues to be hampered by the cost of energy production. This is where the MOSAIC project comes in.

MOSAIC is an innovative modular CSP plant concept, in which the mirrors remain fixed and only the receiver tracks the sun, thus eliminating many moving parts and reducing costs. Its spherical concentration allows us to achieve high concentrations and temperatures in a linear receiver of reduced size, while the Fresnel approach of the concept allows us greater flexibility during its implementation, being able to adapt to any orography and facilitating its integration into buildings. These features and its modular approach make the MOSAIC concept ideal for matching the energy needs of end users under any circumstances (distributed and centralized generation, electricity and industrial heat applications).

The main objective of MOSAIC project is to validate this technology at a relevant environment. In order to achieve this, the specific objectives in the project are the following:
• Development of an innovative low-cost fixed solar field with a high concentration ratio taking advantage of combining spherical concentration and Fresnel features.
• Development of a high temperature receiver tailored to the highly uneven flux distribution generated by this solar field.
• Development of a low-cost, fully automatic receiver tracking and monitoring system.
• Integration, testing and validation of the whole MOSAIC prototype module.
• Design of the optimum modular plant based on lessons learned from the project.
This innovative concept has been validated in a relevant environment through the design, optimization, construction and operation of a prototype in Sangüesa, Spain.
• The most impressive element is the fixed solar field, acting as the concentrator of the solar rays and composed of 43 modules of mirrors divided in 3 Fresnel zones to reduce construction cost: a central skull-cap, and 2 concentrical rings. During the optimization process, the amount of energy reflected by each mirror along the year has been analyzed to identify the least cost-effective mirror zones and remove them to achieve both high concentrations and low implementation costs.
• The mobile receiver is made of three parallel helical tubes wound on a cylinder to balance the energy captured from the uneven flux distribution. A couple of flexible hoses link the mobile receiver to the rest of the thermal loop where the heat is stored. All this thermal loop is integrated in a skid at the top of the central tower. This tower also includes an oven to protect and warm the receiver, thus ensuring it’s ready for operation at any time.
• Finally, a tailored tracking system moves the receiver throughout the day and the year, covering the wide range of positions. In order to reduce costs and increase simplicity, while keeping high accuracies, the receiver is moved by actuated cables suspended by pulling mechanisms on four simple towers (one at each corner of the solar field). The control of the cables includes an artificial vision system that determines the actual position of the receiver at any time thanks to fixed cameras in the pulling towers.
In October 2021, this first of its kind system operated successfully for the first time and since then, the receiver is able to chase the reflection of the sun, eager to capture the 300 kW of radiation concentrated by the solar field.

A fast and accurate assembling methodology has been developed that allows the installation of all the mirrors in a very short time. A global control system synchronizes the receiver movement and the thermal loop to operate the whole system under the sun.

However, it is only the beginning of the development of this new technology. With the experience acquired and the data obtained, we are working on new, more efficient and lower-cost configurations. MOSAIC developers can already define with data in hand, which mirror configuration is more efficient, can be assembled more quickly and is the cheapest for each location and application. Likewise, the operation of the system have made it possible to identify how to improve the positioning system, more robust ways of knowing its position or easier ways to capture and take advantage of the heat generated.

The next steps should be focused on paving the way for the commercialization of this concept, building up on this experience of prototype tests, improving O&M by introducing Artificial Intelligence to allow 100% automatic operational modes, developing its modular versatility. Taking advantage of its modular and flexible semi-Fresnel approach, it is possible to adapt the designs to the thermal and electrical applications according to customer needs.
Receiver tracking the concentrated solar flux
Top view of the prototype
View from the centre of the spheres
Design of the solar field
Prototype under test
Conceptual Design of the system