Design and prototyping of an autonomous robot for automatic cleaning of solar orchards

There have been different studies to analyse and quantify the impact of the dirt on the performance of solar panels and all concludes the dust and dirt deposited on its surface to cause losses of irradiation in solar panels decreasing the power output of the modules that make up. According to the annual report 2008 of the Association of industries photovoltaic (Asif), the losses can be around 3%, and can reach up to 15%, when an optimal value for such losses would be about 0.5%. The losses estimated by MW of installed capacity, as a result of the dirt accumulated on the surface of the panels can range between 18.404 and 30.673 euros per year.

The company Solar Bright S.L., in collaboration with the Institute for Industrial development of the Science Park and of the University of Castilla - La Mancha, Albacete has implemented a project of r & d, co-funded by the Junta de Comunidades de Castilla La Mancha through the ERDF and the CDTI (Ministry of industry) fundsfor the development of a method of cleaning automated, secure, cost-effective, sustainable and effective.

The technical specifications agreed upon by the applicant company, Solar Bright S.L., the Industrial Development Institute and the University of Castilla - La Mancha to achieve the main objective of the project were:

Capacity of clean fixed solar panels of one or two rows

The Effector cleaning must have at least the length of two rows of panels (> 3,80 metres).

It must be effectively cleaned plates

After the cleaning process, the plates must recover, at least 97% of its production line.

It must operate safely

The cleaning process must have a zero rate of deterioration of the panels, so cleaning is carried out taking into account the pressure and maximum permissible temperature for panels.

It must be autonomous

You must have ability to clean up independently at least 8 hours.

Capacity of clean up quickly

You should be able to clean at least at an average speed of 1 km/h.

You must be a light

The weight of the package should not exceed 3,500 kg.

It should be easy to manipulate

A single operator must be able to operate the prototype.

After months of experimentation and study, it was determined a cleaning procedure based on the use of steam as a single product supply. The procedure of cleaning allows cleaning in motion to a linear velocity of more 1 km/h, i.e., a panel each 1, seconds, with a water consumption low, 166 cubic inches per panel, and recovering 100% of the efficiency of the panels.

However, this procedure required contact between the cleaning tool and very constant and controlled panel in pressure. Cleaning tool was mounted in a commercial vehicle on a hydraulic boom during the movement of the vehicle suffered approximately 28. of frequency oscillations and 600 millimetres in breadth. Thus, cleaning tool should maintain a constant pressure on the panel regardless of the vibration suffered by the end of the hydraulic boom during the movement of the vehicle on the streets of a solar Park. Figure 1 shows a diagram of the described scenario.

The mechanical system uses a four bar linkage that draws a straight line for the movement of one end. The other end moves through a motorized bar attached to the chassis through a connecting rod. The motorization of the bars is not linking them directly to the reduction of the engine if not used a four bar linkage. In this way it is isolated to the dangerous reactions engine, is also synthesized this mechanism so that you have a response more linear. The system also has two piers that were designed to help the engine to move the cleaning tool.

The pressure on the panels will be proportional to the intensity that passes through the winding engines. Maintaining constant intensity slogans can ensure uniform pressure on the panels. The control takes into account that the contact between the panel and the cleaning tool should never be lost. Similarly, you can fail over to a 'manual mode', where the operator is able to operate the position of the mechanism with a control located in the cab of the vehicle (transport mode).

The control application developed on the raised platform reads the position of the engines and provides them to maintain permanent contact between the cleaning tool and panels. Similarly, secured the contact, it maintains the level of pressure on them according to a motto selected from the operator in the cab of the vehicle.

Conclusion

Figure 2 shows the final appearance of the prototype, known commercially as Rolhus (Robot cleaner Huertas plots) and the result of the cleaning.

The General characteristics of the developed prototype are:

• Recovery of power: 97-100%
• Consumption of water: 150-200 cc/panel
• Range: 6-14 hours
• Cleaning speed: 1, 2s-1, 6 s/panel
• Number of employees: 1