The UAE’s Shams 1 officially opened on the 17th March, marking the start of operations at the 100 MW concentrated solar power (CSP) plant. Whilst it might be tending towards hyperbole to see this as the landmark birth of utility-scale solar developments in the region, there’s no arguing with the size and ambition of the project.
As our guide during a tour of the site tells us, solar power plants are all about numbers, and Shams certainly boasts some impressive figures. Through its 258,048 mirrors, arranged in 768 units of solar collectors, the system creates the electricity needed to provide for some 20,000 homes. The plant, spread over a site of around 2.5km2 , is now the world’s largest CSP plant in operation, and amounts to around 10% of total CSP capacity around the globe.
The developers have said that the plant, located 120km from Abu Dhabi and 6km from Madinat Zayed, was sited in the emirate’s Western Region as a continuance of the area’s central importance to the energy sector. Home to the lion’s share of the UAE’s hydrocarbon reserves, the region is now set to become a focal point for renewable energy and in future will also play host to the Barakah nuclear development. Of course, the region also benefits from one of the world’s highest levels of solar irradiation – a rather more prosaic, though no less important consideration when developing a new solar plant.
A 7 metre wall, partially made up of concrete and topped with a mesh, protects the site from the worst of the desert winds that would otherwise dump quantities of dust and sand over the plant’s mirrors. The prevalence of dust in the atmosphere has been one of the key talking points about the development – with critics suggesting that excessive amounts could unduly impact on plant efficiency. The developers have combated this potential effect with twice-weekly cleaning of the mirrors using specially designed trucks that keep the reflectors at their cleanest and most efficient. At the same time, we were told that tests done early in development showed that mirrors left to the elements for three weeks still had a reflecting rating of 91% - still higher than the 85% below which performance starts to be substantially affected. It does seem that the ‘dust issue’ may well be under control.
Standing inside the plant, the scale of the project is very evident, as is the fairly intense heat radiating from the panels. Indeed, the operators say that when the plant is operational, with mirrors set to fully track the sun, it is not actually possible to walk around the site due to the high temperatures. The operation of the site sees the parabolic mirrors concentrate sunlight onto a central tube of heat transfer oil, heating the fluid to around a toasty 393 degrees Celsius. This fluid then circulates through the tubes – arranged in parallel loops – until it reaches a heat exchanger where water is turned into steam. The temperature of this steam is then boosted by onsite gas-powered heaters, which increase temperature to 540 degrees Celsius.
The presence of gas heaters on-site is an important part of the process, automatically compensating for temperature loss on days with high cloud-cover or low solar irradiation, and boosting steam to an optimal temperature for power generation. Without this gas boost, plant engineers said that plant output from solar alone would stand at around 53 – 56 MW – equating to around 55% of total plant output from the solar field. The gas heaters also allow for the site to be run at night – particularly useful during summer spikes in power demand.
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