AREVA Solar, Inc. constructed, commissioned and operated the first-of-its-kind Once Through Solar Steam Generator (OTSG SSG), SSG4 at the Kimberlina Solar Thermal Power Station. The construction and commissioning of SSG4 was completed in September 2010, culminating in the successful execution of a series of performance tests. This was the first SSG that AREVA Solar, Inc. designed, manufactured and constructed to comply with ASME Section I, and registered with the National Board. SSG4 is the first in its class that produces high-pressure, superheated steam in a once through configuration. Some aspects of the system presented unique commissioning and operational challenges that are not commonly found in conventional fired boilers. These include: i) the use of a first-in-class model predictive control (MPC) system; ii) a steam integration system to blend steam from the once-through superheated SSG4 and the previous-generation, saturated steam SSGs; iii) a steam handling system that delivers the steam to a turbine generator or to a dump condenser; iv) precision optical tracking that is required for optimal boiler performance; v) 1310ft (400 meter) long boiler tube bundle. Unique for field erected boilers, the SSG4 tube bundle was welded at grade. After being inspected, the receiver and tube bundle support structure was placed over the bundles, secured and the entire receiver structure, with boiler tubes, was hoisted to its operating position, 60ft (18m) above grade. Following final connections of feedwater and steam piping, the boiler was inspected by Hartford Steam Boiler Insurance Company, which included hydrostatic test pressurization to 2002.5 psi (13.8MPa), and the stamps were applied to the boiler nameplate (see Figure 1 for a photo of the SSG4 boiler nameplate). Commissioning included standard boiler flushing and tube cleaning program and a comprehensive set of pre-operational tests. There were additional requirements that are unique to Compact Linear Fresnel Reflector (CLFR) solar thermal systems such as reflector alignment and tuning. These and other commissioning activities were scheduled around a constraint unique to solar systems — the availability of sunlight. A comprehensive set of procedures was followed to enable safe and successful integration and commissioning of the model predictive control system. Upon completion of commissioning, the plant was turned over to operations for continued testing. Stable superheated steam delivery was achieved within one week of Mechanical Completion, and Acceptance Testing was completed two weeks later at levels that exceeded the guarantee. This paper will describe the details of the integration, construction and commissioning milestones, distinctive aspects of commissioning solar thermal systems, and organization of the commissioning team to achieve success.

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