Chilling in the Heat of Doha Sun

For the final of the 2022 FIFA World Cup football tournament some 86,000 spectators will convene at the Lusail Iconic Stadium in Qatar, if the nation’s on-going bid is successful.

As envisaged, the stadium is certainly iconic. Its Foster + Partners design encompasses the sweeping curves evocative of the sails of a traditional dhow boat, but — perhaps more significantly — it is also potentially set to feature a major solar thermal cooling installation. Designed to cool those thousands of fans who visit the Doha stadium in the up to 45°C heat of the Arabian Peninsula, with a backdrop of a World Cup final and its television audience of many millions, it will no doubt do much to highlight the power of solar cooling and low-carbon, low-energy development.

Located to the north of Doha, with direct connections by road and a new metro line, its parking and service areas are to be shaded by canopies of solar PV collectors, which will produce energy for the stadium when it is in use, as well as generate power for neighbouring buildings. Overall, the stadium is designed to be net zero carbon in operation.

Indeed, Sheikh Mohammed bin Hamad bin Khalifa Al Thani, chairman of the Qatar 2022 Bid, reportedly said: ‘The stadium will inspire a new generation of regional and international sports venues, incorporating environmentally friendly cooling technologies to ensure the ideal conditions for players and spectators alike. The design of the stadium provides fans with optimum views of the action in a cool and comfortable setting.’

In a recent interview, Mark Fenwick, senior partner of RFA Fenwick Iribarren Architects, commented on the major challenges in designing and developing such venues for this region. ‘Certainly the most important challenge for stadium design in the Middle East has to do with the need to cool the interior environment to an acceptable level, especially in the summer months,’ he said. Fenwick added: ‘One of the most exciting challenges in modern stadiums in the Middle East is to develop a design which allows cooling for the players and the spectators, and to resolve a responsible energy source, such as solar power.’

The solar-cooled showcase stadium in Qatar (Gem Advertising and Publications)

A Showcase for Low-Carbon Development

Blazing a trail for that major development is a pioneering installation at another of the 12 stadiums which the Qatar authorities submitted as part of their bid to FIFA.

Designed by Arup Associates, the 500-seater showcase ‘model stadium’ in question is zero carbon in operation and features an operating concentrating solar thermal cooling system. Serving as a proof-of-concept, it is expected to act as a development platform to refine the technologies for application across Qatar, at the Lusail Iconic Stadium and potentially across all arid regions.

Commissioned to demonstrate to FIFA and the world-wide audience that the harsh climate over the summer months is no longer a barrier to hosting global events, the showcase has been designed to create a controlled microclimate over and around the football field, and other public spaces. Its design is focused on three key elements: passive energy-saving architecture; photovoltaics; and solar thermal cooling for summertime air conditioning load.

Now completed after a four-month build period, the structure features a revolving canopy roof which moves to provide cooling shade within the building and is thermally insulated. Remaining closed over the space until the sun has passed overhead, the shading roof can then be opened without letting the sunshine heat up the space.

Unless the outside conditions are extremely hot and windy, the roof may open to the sky. Under more adverse conditions, the canopy can be closed in the run-up to an event, allowing the system to cool down the closed air volume ready for match time, working at maximum efficiency. The developers emphasise that the surfaces of the showcase are also designed to remain cool throughout a match in order to help to stabilise the thermal gains from lights, the assembled spectators and so on.

A solar field outside the stadium is made up of both grid-connected photovoltaic panels and Fresnel-type reflectors. Together with generators using biofuels, the amount of electricity generated exceeds net imports for events over the year, making the facility zero carbon for electricity.

The solar thermal field, supplied by German engineering and manufacturing group Mirroxx GmbH, features single-axis tracking flat-plate mirrors which focus solar energy onto a water-filled Schott PTR®; 70 vacuum absorber tube — heating the fluid, which is pressurised at 16 bar, to some 200°C. With a total aperture area of 1400 m², the collectors are rated at 700 kW, with Mirroxx claiming a maximum optical efficiency of 62%, based on DNI, and a peak performance of 500 W/m². The system has modules that are 4 metres long and 8 metres wide with 11 primary mirror rows and uses toughened flat white glass mirrors and a polished aluminium secondary reflector. Arrayed in 32 metre-long sections, each of the individually-driven mirror rows features a 7 W electric drive motor.

Mirroxx’s Fresnel technology is a spin out from the Fraunhofer Institute for Solar Energy Systems (ISE) and the product was launched five years ago, the Qatar installation being the largest demonstration of the collectors to date. High output temperatures from the design make the collector ideally suited to power absorption chillers, the company says.

Energy from the collector field is used to drive a double-effect lithium bromide absorption chiller supplied by Thermax Absorption Cooling, headquartered in Pune, India. Thermax Vapour Absorption Machines (VAMs) are designed to be driven by different heat sources and to offer a minimum outlet temperature of +5°C.

The output is then stored in eutectic tanks beneath the showcase for use in the evening when it is circulated through air-handling units (AHUs) supplied by Desiccant Dry Air. Commissioned in the early summer of 2010, the UK company produced two 8-metre-long dual wheeled desiccant AHUs designed to control the very high temperature and humidity found at the site, with outside temperatures as high as 45°C and relative humidity as high as 95%. The company’s engineers designed a high temperature, high pressure water system that would regenerate lithium bromide coolant for chilling the airflow. High pressure vessels were fabricated and pump sets designed and installed. These units supply chilled air to the area beneath the spectators’ seats, cooling the seating area and flowing down to the pitch to provide cooling for the players.

With the solar cooling system in operation, maximum temperatures are well below the guidelines set out by the FIFA medical committee to avoid players suffering significant heat stress and also beat the ASHRAE comfort standards for spectators, its designers say.

The showcase stadium’s collector field (Gem Advertising and Publications)

Fanning the Flames of Future Development

Recent research sponsored by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and conducted by the Fraunhofer ISE and others found that in the near term, small concentrating solar collector systems can significantly contribute to sustainable development goals. Such small and medium-scale solar thermal power stations generate heat at temperatures up to 400°C and can generate electricity, cooling and industrial process heat. Dr Werner J. Platzer, department head at Fraunhofer ISE observed: ‘Small is beautiful — and most of all fast. Systems ranging from 20 kW up to 2 MW can be more easily realised and they offer greater possibilities.’

‘For regional applications, the technology is economical where there is a large fraction of direct sunlight. For off-grid applications or for applications where the provision from the grid is unreliable, this technology is more cost-effective than employing a diesel generator,’ said Platzer.

‘Air-conditioning could also be an important application. Over 40 million new air-conditioning units are sold worldwide annually and the tendency is increasing. Up to now, this potential application has not been used because market-ready products and demonstration projects that serve as role models are still needed,’ he added.

The Qatar 2022 Showcase appears to have delivered at least one more role model. During the FIFA visit, with an outside temperature at 44°C only two hours earlier, the pitch was recorded as 23°C. If Qatar wins through against the other bids for the FIFA 2022 — including Australia, Japan, Russia, South Korea and the USA — then it will surely serve as a role model for large scale solar thermal cooling too. The FIFA Executive Committee, chaired by President Joseph S. Blatter, is due to vote on the winning bidder by secret ballot as REW goes to press.

David Appleyard is chief editor of Renewable Energy World magazine.

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