At our firm, we split the design stages into two distinct parts; Outline Design and Detailed Design. Outline Design includes everything required to support the various environmental, planning and grid connection consent applications. Once the consents have either been obtained or are expected to be issued the Detailed Design stage can start which includes everything required to actually build the system.
Outline Design (D1)
Outline Design includes the following:
•Detailed site survey
•Site plan and layout drawings of main structures and hydro hardware
•Outline design of all structures (weirs, channels, intake area, turbine house and discharge)
•Outline electrical system design
•Specification of main system parts (turbine, generator, penstock pipework)
All of the work completed at the outline stage is done to the same level of precision as the detailed design, the only difference is that the design is only taken to the point that is necessary to support the consent applications. The reason for this split is so that if the design has to be changed as a result of the consent applications then the minimum amount of time (and money) has to be spent reworking it.
Detailed Design (D2)
Once the various consents have been issued, or once everyone is confident that they will be issued then it is time to complete the Detailed Design stage (D2). This is the full construction design and equipment specification, including all mechanical, electrical and civil engineering aspects. The result is the construction design package which contains everything required to issue tenders for the civil engineering part of the installation phase and then go on to build it. It also includes the full hardware specification so that the turbine, screen cleaner and all of the ancillary parts can be ordered.