By Rajesh Chhabara, Asia correspondent

Desert climates may drastically differ from region to region. For example, the United Nations classifies deserts as hyper arid, arid, semiarid and dry-sub humid. There are real deserts such as in the Middle East, India and Australia. Then there are the ‘desert-like’ areas, as in the southwest United States and Spain.

Diverse meteorological stress conditions may exist in different regions or within the same regions. In the US, hot and humid in Miami (Florida) contrasts with hot and dry in Phoenix (Arizona). In California State alone, warm and humid in Sacramento gives way to hot and dry in Dagget. Then you have hot and mild in Almeria (Spain) and hot and dry in Thar desert (India). You get the picture.

So how do these different conditions potentially affect the design, maintenance and operation of a CSP plant?  Higher radiation level found in actual deserts could impact the plant design in terms of relationship between the size of the storage and the size of the solar field, says Prof. Dr. Robert Pitz-Paal, deputy head of the Institute & head of department of solar research at German Aerospace Centre’s Institute of Technical Thermodynamics Solar Research.

“If you have a higher radiation level, you need less solar field to run the power block. Also storage is less important to smoothen the intermitted solar resource. This means you have to add a smaller storage to the plant.”

However, higher radiation advantage is not limited to actual deserts and that makes distinction between a real desert and a desert-like area more complex.

“Some of the brightest spots on earth are in the southwest USA, especially in California and Arizona, which show 10%-16% higher direct normal irradiation (DNI) than countries like Saudi Arabia, Abu Dhabi or Oman,” Dr. Henner Gladen, founding member of Solar Millennium AG, says.

Dr. Pitz-Paal says that another key point is related to the availability of cooling water. Typical real deserts lack naturally available cooling water. Operators then need to rely on dry cooling. “A dry cooling tower is significantly more expensive than the wet cooling tower,” he notes.

As opposed to wet cooling, dry cooling towers rely on electrically driven ventilation systems, which further add to the cost, Dr. Pitz-Paal points out. Dry cooling is also relatively less efficient.

As such, companies that deliver innovative technologies to reduce costs of cooling systems for dry deserts will be winners.

Opportunities for niche players

Higher soiling of mirrors in a desert due to sand storms is another point of difference. More dust and sand means implies more frequent cleaning, and an additional effort in maintenance. “But the amount of radiation typically offsets this disadvantage,” explains Dr. Pitz-Paal.

In future, diverse climatic stress conditions may offer innovative opportunities for component manufactures to tailor products.  Observers say that this could mean emergence of niche manufacturers who may offer specific products or applications suited to the specific climatic condition.

However, key players in the mirror and the receiver technology sectors have not yet made attempts to develop such niche products, or to differentiate their products based on climatic conditions.

On the contrary Dr. Gladen points out that a standardisation of mirrors and receiver tubes is currently taking place. “Manufacturers want to have one single size so that they don’t have to equip different projects with different mirrors or different receiver tubes.”

But Dr. Gladen agrees that this situation may change over time. “Theoretically speaking, in 10 or 20 years it might be reasonable to have light weight structure in arid desert which are not so windy or have an extra lacquer on mirrors where we know there is more dust and the probability of sand storm is higher.”

The issue of site-specific customisation is not on the industry agenda at present. “At this moment we see mirrors of the same size and of the same quality for all site locations in the world,” he says.

Solar Millennium, which has CSP projects in various stages in diverse desert regions such as the Middle East, China, Spain, the US, India and North Africa, currently deploys the same equipment across all projects.

Currently, efforts are more directed toward improving the overall efficiency of products. For example, the US National Renewable Energy Laboratory’s plans include development of advanced reflectors that can reduce cost by improved performance by using anti-soiling coatings and low-to-no water cleaning.

Another NREL project includes developing soiling tests and determining soil properties and soiling rates at outdoor sites.  The learning can be potentially used to understand more accurately the different soiling rates in desert and desert-like areas.

Dr. Gladen says that if there are real markets in future with huge capacities to be installed such as exceeding 10,000 MW at one site, and if there are site-specific conditions that allow for specialised manufacturing, there may then be a case customised products.

To respond to this article, please write to:

Rajesh Chhabara: rajesh.chhabara@csrworks.com

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Rikki Stancich: rstancich@gmail.com