Fossil Fuel Free Backup Power?

For the CIRS project at UBC (construction began 2009, completed 2011), we needed backup power to run the smoke exhaust system and to power exit lighting (instead of batteries inside light fixtures). PowerWalls were not an option then, and lead-acid batteries a bad match to a building with environmental aspirations).  Natural gas wasn't allowed because it's in a seismic zone and gas lines get cut off after earthquakes.  So we used a 'diesel' generator fed with 100% biodiesel.   Since tanked fuel goes bad after 2 years, you have to burn through the tank volume over that 2 year period through monthly testing.  Normally during testing this is just dissipated using a resistor bank, but our electrical designer set it up to feed power back to the grid.  https://cirs.ubc.ca

We looked at this and could not find anything that works.  The batteries you need for the initial load for elevators and pumps in multi family buildings do not make any sense so you are stuck with the generator.  Generators are likely to be the last stand of fossil fuels.  

Actually, we've had some good-luck for medium-sized multi-family with battery backup.   We completed a 50-unit, 3-story all-electric affordable housing apartment building in New Orleans that opened in February 2020 with 178kW of solar on the roof and a 125kW / 371kWh capacity Dynapower battery system.  We've gone through one hurricane-induced long power outage (8h) so far and everything ran pretty smoothly. 125kW appears enough to keep up with the inrush current demand, maybe because this project has 50 independent heat pumps, 1 per unit, and they don't literally come on all at once.   Biggest single demand is the elevator, which can be set during a fire to just go descend and let people out at the ground level in an emergency.

The base building construction budget was $6.4M, the building with energy efficiency enhancements, solar, and batteries was $7.4M.  The $1M upgrade was split between efficiency enhancements ($250k), solar ($350k--pricier modules to get to net zero given limited roof area), and batteries ($400k).  The cost of the solar and batteries was able to take advantage of the solar tax credit, resold by the non-profit developer.  We considered a fancy load-shedding system of only 'emergency' items on emergency power but the extra panels and wiring came in at $200k and the only thing it could have shed was the ovens; the HVAC needs power to ensure ventilation.  So we used the $200k for more batteries.  What I would do differently:  Think more about a 'reserve tank' that runs what code considers life safety (exit lighting, etc) distinct from everything else, and a communication (text-blast) system alerting residents that we're running on reserve and asking them to switch HVAC units to 'fan only' and avoid discretionary cooking. $400k for batteries is a lot more than what an equivalent 125kW emergency generator would have cost, of course.  But the local utility was interested in learning more about buildings with storage interacting with the grid and so funded the $1M upgrade.  And battery systems seem to be dropping in price by something like 20% per year these days, so one suspects that by 2030 this approach could be standard...

We recently proposed battery back-up for a project and the client considered it too much of a 'premium.' One other issue was that the building was part of a larger campus that is otherwise served by back-up generators, so there was also resistance to having a hybrid set of systems. So if anyone has developed good arguments for changing over to batteries in a campus context, we'd love to hear it! Otherwise, we see a lot of propane back-up generators.

This doesn't address the initial question regarding "fossil free generation," but another interesting (and promising) angle is "dispatchable generation." Portland General Electric has a program in which owners can contract with them to manage their generators. The generators provide the same backup function for the buildings, but also provide grid benefits (synchronization) and more efficiency (less carbon) for routine testing and maintence. On it's own, this is good. As a model for future use of battery systems, this is very promising. The costs of the battery systems can be shared (in some form) between building owners and grid operators. The utility also has a smart battery pilot program to test it.  https://portlandgeneral.com/save-money/save-money-business/dispatchable-standby-generators https://portlandgeneral.com/smart-battery-pilot

I've recently looked into hydrogen fuel cells for backup power and ran across this installation at a Microsoft Data Centre.  https://www.geekwire.com/2020/microsoft-makes-hydrogen-fuel-cell-breakthrough-quest-power-data-centers-renewable-energy/  I 've spoken with the group behind the installation (Renewable Innovations) who are integrators capable of using a variety of companies fuel cells (like Ballard, Daimler or Cummins). Interesting group and I was thinking of putting together a bit of a thought exercise on the idea of using fuel cells for a building's back-up power (size and storage reqts etc...). I'll post it here when complete.

Larger buildings require on site storage.  Using a large gas tank (or hydrogen, if available) on site can be interesting.