When the grid goes down, a standby generator is only useful for as long as it has fuel. The fuel system is often treated as an afterthought, but it’s what decides whether a site rides through a two-hour outage or a two-day one.
Start with the runtime requirement
The first question is how long the site needs to run without a refuel. That figure might come from a client specification, an operational risk assessment or the realities of getting a fuel truck to site during a major event. Hospitals, data centres and critical utilities often need considerably longer runtimes than a typical commercial building.
Runtime, combined with the generator’s fuel consumption at the expected load, sets the storage volume you need.
Base tanks, day tanks and bulk storage
Smaller installations often rely on a base tank built into the generator skid. Larger sites typically combine a day tank near the generator with bulk storage elsewhere on site, connected by transfer pumps and controls. Each arrangement affects footprint, structural loads, compliance requirements and how the system is refuelled.
In Australia, the storage and handling of diesel falls under standards such as AS 1940, which influences bunding, separation distances and other details. Your designer should be across the requirements that apply to your site.
Transfer and control
Where fuel moves between tanks, the transfer system needs to be reliable and monitored. Level sensing, alarms, overfill protection and pump redundancy all play a part. Many sites also integrate fuel level monitoring into their building management or remote monitoring systems, so low levels are flagged well before they become a problem.
Don’t forget fuel quality
Diesel that sits for long periods can degrade, pick up water and grow microbial contamination. Poor fuel quality is a common cause of generators failing when they are finally called on. Regular testing, water removal and, where appropriate, fuel polishing help keep stored fuel ready to use.
Design for refuelling
Consider how a tanker will access the fill point, especially during an emergency. Safe access, clear signage and a fill point that doesn’t require entering the generator area all make refuelling faster and safer.
The takeaway
A well-planned fuel system is sized for a realistic runtime, compliant with the standards that apply, monitored, and maintained so the fuel is usable on the day it’s needed.
