Vast Solar – basic and detail design of main steam circuit of Jemalong pilot solar plant

In 2013, H&D Engineering was invited to participate in the design of a concentrated solar power pilot plant in Australia. H&D cooperated with the R&D division of Skoda Doosan Power on the project, which aims to significantly change the energy market conditions and increase the ratio of renewable resources in Australia and other countries. The end client, Vast Solar, aims to re-engineer the future of large scale solar to transform world energy systems. It plans to do this by delivering efficient, modular Concentrated Solar Thermal Power (CSP) technology with affordable storage.

Vast Solar’s Jemalong pilot plant makes use of CSP technology and is located close to Forbes, in NSW, Australia. The plant consists of five solar fields, each with approximately 700 mirrors, or heliostats. The heliostats can be focused on a 27 meter high tower to heat the main heat transfer fluid.

The use of liquid sodium as the main heat transfer fluid differentiates the Jemalong plant from similar projects around the globe, which generally make use of water or molten salt. The key advantage of liquid sodium is its high thermal conductivity and therefore excellent heat transfer properties.

The heated sodium with temperatures above 500°C is led to a storage tank, which acts as a thermal buffer to the power cycle. This reduces cyclic loading and thermal shock on the steam generator and other components downstream.

The sodium from the storage tank is used to produce steam in the steam generator. The generated steam produces up to approximately 1.1 MWe via a single-stage steam turbine generator. The Jemalong unit has been produced mainly for testing purposes. If the current testing is successful, Vast Solar plans to build a considerably larger unit of 30MW.

Main steam circuit design with Cadmatic

H&D Engineering was responsible for the basic design and detail design of the main steam circuit for the pilot plant. It also conducted pipe stress calculations on the sodium lines in the fields and prepared additional documentation for commissioning and cleaning operations. 

Štěpán Šmida, H&D Machine Design Department Manager, indicates that Cadmatic was used as the main design tool for the project. 

“We were able to import all the technology elements such as the turbine and air-cooled condenser very quickly into the Cadmatic 3D model in the form of large *.step files. It helps a lot when you can do everything from start to finish in one 3D model. It was easy to prepare the main concept power plant and subsequent documentation as we did not have to create new 3D models for each step of the design process. Cadmatic also eased project communication, allowing rapid transfer of data between Australia and The Czech Republic.”

Changing standards

During the project, it became necessary to change all the standards used from EN to ASME. This naturally affected all pipes, elbows, flanges, etc. 

“It was the first time we have needed to change standards mid-­project and we were not sure how time-consuming this would be. It was a pleasant surprise to see that Cadmatic handled this change very quickly and efficiently,” Štěpán says. 

A challenging aspect for H&D on the project was a design concept that envisaged the large-scale use of sloped piping to allow the draining of more than 500m of sodium piping between the solar fields. 

“It was quite challenging to connect all the pipelines to the main connection points on the tower and then hit the connection points on equipment several hundred meters away. We naturally used simple aliases instead of calculating the angles for this. Cadmatic’s ‘Follow pipe’ tool also assisted greatly in accomplishing the task,” explains Štěpán.

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