Saturday, December 26, 2015

A post-summer review of my vent fans (Seattle Summer Slicers)

Back in May, I made my first post about a set of window fans I'd built to deal with the Seattle summer weather in a rental with no whole house fan or whole house AC - these gizmos.

The fans are some high quality (ball bearing) Delta 120mm computer fans, secured with automotive trim tape (quite sticky double sided foam tape) into a frame made of aluminum L angle.  Due to their rather high RPM, they've got fan guards on the front to keep fingers, papers, ferrets noses, and other things out of them.

For those unfamiliar with why I put together such a contraption: I live in the Seattle metro area.  Houses out here generally don't have whole house attic fans or whole house air conditioning.  Window units are common enough, but window units don't work well with side-opening windows (they slide sideways, instead of up).  In previous summers, the whole upstairs just got hot, stagnant, and very uncomfortable.  This summer looked like it was going to be a really hot one.  And it was.

It's now December.  I've run them all the way through our long, hot summer, in a house I've been in for nearly 4 years - so I'm quite familiar with how hot the house was previous years.

This summer was, by far, the hottest Seattle summer I've been through.  It was also, by far, the most comfortable in the house - entirely due to these fans.  And they're rental house friendly!

The fans ran perfectly.  I had literally zero issues with them.  After a month or so of playing around, I set them up with a lamp timer.  They turned on automatically around 3PM (that's about when the upstairs started getting warmer than outside), and turned off around 7AM.  In the afternoon, they were venting hot upstairs air, and at night, they sucked cold air through most of the house.  I could adjust airflow by which windows were open, but I also set up a default path that handled the common case (cooling down the whole house).

Read on if you're interested in how things ended up.

Sunday, December 6, 2015

Cobalt Requirements for a Global Electric Vehicle Fleet

It's commonly asserted by many people and a few companies that the future of transportation is electric cars.  One thing electric cars need a lot of is battery capacity - it's what makes them electric, and sufficient battery capacity is what makes them a genuine replacement for a car powered by an internal combustion engine.

One concern often raised about electric cars is regarding the materials needed for the battery.  Lithium is frequently mentioned, but it's not actually likely to be a significant problem.

Cobalt, on the other hand, is used in basically all of the high energy battery chemistries, and is a much more limiting element for widespread electric vehicle adoption.

If you're interested, join me in a bit of a dive through the numbers of cobalt, batteries, and just how much of the world's reserves we need for electric vehicles.  If you're just here for the ebike photos... you probably won't care too much for this post.

TL;DR: Current global reserves of cobalt are 7.2 million tons.  To replace the 1 billion vehicles on the planet with NCA based electric vehicles at 60kWh per car would take 6 million metric tons of cobalt.