The need for workable energy options is perhaps the greatest single challenge facing our nation and the world in the 21st century.
– MIT Energy Research Council, July 2006
If Wikipedia is right, this idea is just a little older than you all (since the 1990s).
Prior to oxy-fuel burners, gas-fired glass melting used complex heat recovery to preheat the air.
Otherwise there's no way to achieve the necessary temperatures. Of course, other fuels also worked.
In 2008 the boiler team won a Chicago Innovation award for a boiler heat recovery invention. They combined it with other state-of-the-art boiler technology to make a "Super Boiler" with Cleaver Brooks.
Images are from a super boiler presentation to the DOE (PDF)
The peak of all of this research was around 2004-2008, when natural gas was the most costly it's ever been. Research funding is lot more scarce now.
We used load disaggregation to identify discrepancies between businesses (like, an office leaving their A/C on all night long) and message them suggestions, like to put the A/C on a timer. This is paid for by utilities in states where they're required to have energy efficiency programs.
This image is from MIT because I couldn't find one from where I worked
Maybe surprising (or not since they have so many locations) — McDonald's has a big sustainability initiative including energy efficiency. Some ideas include