3 ms·

> What remarkable faith? It's a program to start/stop AC/heat units based on temperatyre readings, not to send people to Mars. > A talented high school student

> What remarkable faith? It's a program to start/stop AC/heat units based on temperatyre readings, not to send people to Mars. > A talented high school student can write one today, and do it with a Rasberry Pi and for much less than $1 million (more like 5-10K). Yes, writing a bang-bang controller would be trivial. Even some kind of PID controller wouldn't be too hard for an enterprising high schooler to try. What makes the professional systems valuable is that they can build much more accurate models of how the building heats and cools. These models depend on the building's geometry, usage patterns, outside climate, etc., and are notoriously hard to produce. However, they can produce meaningful savings over long time periods since they ultimately use less energy due to the quality model.

ams6110 8y ago
Those accurate energy-saving models IMO fall apart because they keep buildings just a bit uncomfortably warm or cool, leading everyone to bring in plug-in space heaters, dehumidifiers, and fans. One other trick in the summertime when the central operations folks have decided that the building is cool enough but everyone is sweating, is to bring in a space heater and put it under the thermostat.
- pp19dd 8y ago
  Ah, but it's not always done for comfort optimization. Older electrical meters weren't all that accurate, especially for larger systems - that's true even today. They're analog as an only option of measurement due to incredible amounts of power going through them (too noisy for hall effect sensors). Large buildings are reactive loads to the grid, almost like an inductor. Anyhow, older meters picked up velocity for usage calculations. Some A/C controllers carefully modeled how fast the power meters accelerated as an instrument, then used that information against them, throttling and ramping power use to slow the measurements down, basically causing under-metering. Saved USPS millions a year in power bills.

ams6110 8y ago

Those accurate energy-saving models IMO fall apart because they keep buildings just a bit uncomfortably warm or cool, leading everyone to bring in plug-in space heaters, dehumidifiers, and fans. One other trick in the summertime when the central operations folks have decided that the building is cool enough but everyone is sweating, is to bring in a space heater and put it under the thermostat.

pp19dd 8y ago
Ah, but it's not always done for comfort optimization. Older electrical meters weren't all that accurate, especially for larger systems - that's true even today. They're analog as an only option of measurement due to incredible amounts of power going through them (too noisy for hall effect sensors). Large buildings are reactive loads to the grid, almost like an inductor. Anyhow, older meters picked up velocity for usage calculations. Some A/C controllers carefully modeled how fast the power meters accelerated as an instrument, then used that information against them, throttling and ramping power use to slow the measurements down, basically causing under-metering. Saved USPS millions a year in power bills.