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Cleaning robot Soltibot® successfully tested on Linear Fresnel Collectors

Contributed by: MinWaterCSP

Linear Fresnel collectors are used in a variety of solar thermal applications. Within the EU-funded MinWaterCSP project (Minimized water consumption in CSP plants), the Italian company Soltigua has developed an automatic robot called “Soltibot®” to clean the mirror rows of linear Fresnel collectors, together with a device to clean the collector’s receiver.
Cleaning robot Soltibot® successfully tested on Linear Fresnel Collectors
Mirror cleaning is a major operations and maintenance (O&M) activity in CSP plants and their optimisation is key in reducing the Levelised Cost of Energy (LCOE) of such systems. This optimisation refers to labour as well as water consumption, especially in arid regions where water supplies are costly and scarce.

Linear Fresnel collectors are easy to install on rooftops and have a compact footprint which makes them an ideal solution for MW-scale electricity generation and industrial process heat systems, such as process steam. However, depending on the location, soiling can significantly reduce the thermal output, decreasing the benefits for the plant owner. Therefore, cleaning the collectors on a regular basis is essential to ensure an efficient energy production.

In small-scale systems (up to a few MW thermal/electric), the most common way to clean the mirrors is by manual cleaning such as wiping and spraying. Wiping needs less water and is quite effective but done manually, it is very time consuming and can be very costly and cumbersome. Spraying has a high water consumption and its effectiveness is questionable.

The Italian SME Soltigua has developed an automatic robot-based solution: the Soltibot® in order to overcome such limitations.

The new device will reduce cleaning time and limit the amount of water consumed in the cleaning process. As a wheeled cleaning robot, Soltibot® moves along each mirror line carrying the cleaning water and cleaning the primary mirrors in three steps: washing - brushing – wiping. It quickly shifts from one line to the other. Soltibot® crosses the collector drive system which lies just in the middle of the collector and recognises any obstacle, which might be in the way, preventing any damage to itself or to the collector in case an operator executes an incorrect instruction. At the end of each mirror line, Soltibot® automatically moves from the mirror to a trolley, which completes the cleaning cycle. The trolley is used by an operator to slide the robot to a new mirror line and refill it with water.

The robot’s nozzle design reduces water consumption by 90% compared to existing CSP cleaning systems, with an average consumption of 0.11 lt/m2. Thanks to its wiping system, tap water can also be used in the system, saving on expensive water treatment systems.

In May 2018, the whole cleaning system was vastly tested at IRESEN’s Green Energy Park in Morocco, where a 16000+ m2 Fresnel system is located. Local operators learned to use it and effectively cleaned the collector mirrors, restoring the reflectivity to more than 99%.

Thanks to this new product, Soltigua can offer a complete package together with its collectors, also taking care of their customers’ O&M activities.

SOME FACTS about Soltibot® for Linear Fresnel Collectors:

Size and inclination of Mirror Line (FLT):
• The robot carries the water to clean up to 100 m of a mirror line (62 m2) and is quickly refilled from a secondary tank located in its ancillary trolley, which is used by an operator to transfer the robot from one mirror line to the other.
• The robot can run on sloped mirrors up to a 10° lateral slope, so that it can clean several mirror lines in the same angular position.
Typically, two robots (and two trolleys) can be used on the same collector working from different sides, minimising cleaning time.
Mirror drive is crossed by means of foldable ramps.

Effective cleaning:
• Soltibot® can clean dirty and sticky mirrors in one single run, effectively and consistently, bringing the mirrors back to their original reflectivity.

Economic cleaning:
• 55% reduction of cleaning time (min / m2), and
• Up to 90% reduction of cleaning water (l / m2)
• Low cost, a few k€ for serial production
• Limited weight, 55 kg incl. water
• Short dimensions (1100x700x330 mm)

For more information, please contact:
Lorenza Amadori - SOLTIGUA
Email: lamadori@soltigua.com

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Keywords

Linear Fresnel Collectors, MinWaterCSP, water consumption, soiling, mirror cleaning, SME, Soltigua, Soltibot, concentrated solar power, Green Energy Park
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