Bite the dust

Robonaut’s Thomas Michel explains the impact that dust can on solar panels, but highlights that this need not stand in the way of a solar power for the Gulf region.

Why is dust an important factor for future solar projects in the gulf region?

Thomas Michel. The Gulf region and Arabian Peninsula is an ideal region for solar power. There is plenty of sunshine, lots of unused land, high local energy demand and available capital. However dust, both in the air and settled, spoils this picture.

Regardless of the question whether thermal or photovoltaic (PV) will make the race, dust has to be taken into account. For thermal solar power, both dust in the air and dust on reflectors have a negative effect. Light is scattered and lost. Consequently reflectors rely on impeccably cleaned surfaces. In contrast, PV is much more tolerant to defused sunlight. However, once enough dust is deposited on PV panels it will start to shade off sunlight and ultimately decreases performance.

On the Arabian Peninsula dust is omnipresent. Summer and winter sand storms (Shamal) disperse vast amounts of mineral dust particles into the air throughout the year. The occasional cold-front sand storm (Habub) can dump high amounts of dust in a matter of minutes. The Gulf region is in fact a very dusty place.

Why is efficient cleaning of PV panels in large solar parks important?

TM. Dust on PV panels is generally easy to clean off. PV surfaces do not have to be cleaned perfectly. But how do you clean 130 soccer fields worth of solar surface? Just like any surface, but very much faster.

A 100 MW PV power plant is composed of about 130 football fields of solar surface. You may hire 150 people, give them a broom and lots of water to drink. They might do the job, despite the unpleasant heat. They possibly finish the whole surface after 2 weeks and then start anew.

Another way is to send one mobile robotic cleaning machine and let it clean the entire surface in less than 10 days, no human error, no water consumption. This is exactly what the Swiss company Robonaut GmbH has in mind. 

Why use a fully automated robotic system?

TM. High speed and constant quality are some of the key factors. It is clear that recruiting an armada of people with a broom might not be the most efficient method. You may agree, that a machine of some sort would be a necessity.

A manually operated machine bears the risk that operators make mistakes. The monotonous work and the time constrain increase this risk. Consequently, the machine must do all the critical manipulations autonomously, with no operator involved.

A robotic system does exactly that. It eliminates human error. It does the same job much faster and more reliably than a manually operated machine. In fact it can operate 24/7 with unchanged quality and reliability. Let's be reminded that damage on the PV arrays is costly and not predictable.

In very large PV parks, one task is to do the cleaning, another is to drive intelligently through the PV arrays, minimising the unproductive time. 

A structure to support and guide the cleaning head is generally a very good idea. However, this must be planned and integrated by the company who builds the panel arrays. Besides the added cost, it is difficult to motivate the numerous manufacturers to add such a feature.

How does Robonaut's robotic cleaning system work?

TM. The off-road mobile robot system with the brand name Xpedous cruises alongside the PV panel array using a redundant navigation system and many sensors. It caries all the cleaning machinery on-board and is powered by a suitable energy source. The sensor guided cleaning arm floats over the panel array and does not need any supporting structure. On reaching the end of an array the cleaning arm is lifted off and put down at the next array. Dust is collected automatically into a container. Xpedous is designed for 24-hour operation.

About

Thomas Michel is co-founder and Managing Director of the Swiss based company Robonaut GmbH. His experience as a mechanical engineer and entrepreneur as well as his expertise in robotics and large solar installations are fundamental for Robonaut's activities and future products.