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.


Thursday, October 05, 2006

Peak Oil Home Electricity Requirements (Part 2)

Smart design is about allowing for transition. Yes, appliances will eventually degrade and power sources will decrease in efficiency over time – but rather than requiring that you have all your sustainable skills and supplies in place by the time your home is built, allow time to transition from an energy-intensive life to a sustainable one. Don’t beat yourself up for using a refrigerator in your post-Peak Oil home, but learn to get by without it (e.g. using ice houses, root cellars, etc.) as part of your graduated development. Also, don’t design yourself into a corner for which you lack the skills or resources to cope.

If you design your systems to meet your current connected lifestyle with TV and computers (how else could you keep blogging?!?), when those devices are no longer useful you will gain spare electrical capacity.

This first estimate is by no means the final word on your electrical requirements. As your design matures, you may find that you don’t need anywhere near the initial estimates (after designing insulation, non-electrical heating, etc.) or that you can’t afford to generate that amount. If the latter is the case, you can fix your situation either procedurally or technically; that is, by adjusting your usage behavior or using more energy-efficient appliances.

For now, in the first design iteration, we will keep these values as test requirements and adjust things as we go.

Take a look at the numbers in table in Part 1. We can use the daily 65 kWh as-is for now, but the 27 kW of peak power is a huge figure. Already, it is obvious that running all of these electric devices at the same time is not practical (in fact, you would really have to work hard at it to run them all at the same time!) and procedural limits are required. Re-examining the list, we can see that the constantly running devices we don’t turn ‘on’ (e.g. fridge, water heater, etc.) could cause a peak of 6400 W (in the summer) if they all clicked themselves on at the same time. Using engineering judgment, we can then say that a limit of 3600 kW of transient electricity for the remaining appliances could meet the family’s needs. So for now, let’s choose 10 kW as our peak energy draw requirement.

Our second iteration on all the parts of this design will begin after we complete the other top level requirements.


At 1:32 PM, Blogger Jon L. Picard said...

Hi Peak Engineer,

I like the Usage Table - I think i'll do the same for a 12 volt system.

I would like to do an online interview with you on a bulletin board. Email me - conserver(at) - if your interested.

Thanks and best regards,
Jon L Picard

At 4:17 PM, Blogger PeakEngineer said...

I'll do that Jon.

At 9:59 PM, Anonymous SnippetsandBits said...

Nice blog Peak Engineer. I checked your site a month or so ago and I was interested.....but now I'm truly impressed.

Keep up the good work!


At 10:05 PM, Blogger PeakEngineer said...

Thanks, MiedRN! I'm definitely a fan of your site as well. Glad to see you're back in action :)

At 7:50 AM, Blogger Tony said...

Assumming all home loads are 110 volt (117 actually), and also assumming most homes are built with a 200 amp service, won't those homes be limited to peak usage of 117*200=23,400 watts (23.4 kW).

So, isn't anything above 23.4 theoretically impossible in this scenario.

At 12:19 PM, Blogger PeakEngineer said...

It's true that U.S. homes are currently limited to 23.4 kW, but that's a matter of electrical code, not necessarily technical requirement. We haven't even begun discussing codes and their rationale, but it will be a lengthy discussion when we get there.
For now, let's just focus on our perceived needs and adjust things if we decide to follow particular codes. In any case, it's a moot point with this example as we've identified a much reduced number for our requirement.

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