NOTE: Make sure you read the first three posts (in order!) before tackling the rest, or it could be confusing: Post 1 is Designing the future, Post 2 is Setting up the problem, and Post 3 is Estimating basic requirements.

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Tuesday, December 05, 2006

Homestead Updates

Development of the Peak Oil Homestead Example Project has been really dragging, so I’m going to kick it into high gear to keep things exciting and also more relevant to all types of PeakOilDesign projects.

We need to create more assumptions for the Homestead Example in order to develop the requirements further. This will take the problem from the realm of general application to the specific, so our focus should remain more than ever on the process itself.

New assumptions:
Location: Central Iowa, 5 miles outside small town
Topography: 20 acres former farmland, 20 acres timber, small stream
Weather: 34”/year precipitation; Avg winter temps 10-40 ° F; Avg summer temps 50-85 ° F
Budget: $100K


I’ve also updated the ORD for the project using some previously unassigned requirements. They were assigned as follows:

Objective 1.1: The Homestead will provide enough power for 4 people.

Requirement 4.1.1: The Homestead shall have railings (per Spec XYZ) on all exposed stairways.

Requirement 4.1.2: The Homestead shall provide safety protection for all sharp corners per Spec ABC.

Requirement 4.1.3: The Homestead shall provide safety barriers (per Spec AAA) around all hazardous areas and devices.

Orphan Requirement The electrical system shall provide protection for electrical outlets per Spec AAA.
(This requirement will fit under an as yet undefined higher-level requirement.)

Requirement 2.1.1.1: The water system shall provide potable tap water at 50 ° F – 86 ° F.

Requirement 2.1.1.2: The water system shall provide potable tap water at 112 ° F – 145 ° F.

Requirement 2.1.1.3 The water system shall provide a source shut-off mechanism.

Requirement 2.1.1.4 The water system shall remain above 40 ° F at all points.

4 Comments:

At 4:10 PM, Anonymous jeff said...

This is great! Assumptions have to be made to more clearly define a project. I'm assuming this project will exist hypothetically in the real world even though an exact location has not been specified.

So here's what I'm wondering. The Homestead Project is a system that will exist within other systems such as laws, ordinances and codes which are outside the control of the Homestead Project. When defining the requirements for the Homestead Project, how are overlapping requirements dealt with?

For example, I'm assuming Iowa's state building code requires handrails on staircases as this is a fairly standard safety requirement these days. Unless the Homestead Project chooses to ignore the laws of the land, a handrail requirement will be forced upon it, so including it in the Homestead Project seems to be duplicating efforts, or reinventing the wheel, however you want to look at it. Does systems engineering allow for a way to "inherit" requirements, and if not, how is this best dealt with?

Most importantly, what exactly does the T in “T minus 4 minutes” stand for? :) Weather permitting liftoff is less than 6 hours away. Should be exciting.

 
At 5:44 PM, Blogger PeakEngineer said...

T is for Takeoff! :) And not only is the Florida weather not cooperating, but we have a space solar storm on the way which might cause us trouble! (sorry, can't find a link)

I plan to address codes in a little while (I'm taking a National Electrical Code Class in February), but I can say a few words here.

Most codes are based on good ideas (or at least once were) and should certainly be taken into account when designing. Depending on your situation, you may not be required to follow any particular codes (and boy do they vary from place to place!). Most codes do not include much regarding many of the designs popular in green building, even things such as solar and wind power. Throw something like strawbale insulation into the mix and you're likely to give your inspector fits!

The greatest benefit of Systems Engineering is that it allows you flexibility. If you choose to (or are required to) follow codes, it is a good idea to study them in detail early in the design process. If you're very new to construction, wiring, plumbing, etc. it can also save you from reinventing the wheel in a lot of cases.

As with everything, don't take any code as gospel. If something in a code is unbelievably stupid (it adds significant risk, for example), ask yourself if you are willing to ignore it and face the consequences.

That said, many codes have their basis in keeping things safe and reliable. So get all the information you can before making a decision.

 
At 6:12 PM, Anonymous Jeff said...

Thanks, I can't wait to learn how dominant systems get incorporated into subordinate systems (with the Homestead Project being, for the most part, subordinate to state and local codes).

 
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