Duel-fuel generators work like traditional diesel generators, except natural gas is introduced in the intake system before the diesel gets injected, and the diesel ignites and burns both fuels. Duel-fuel generators can work with just diesel fuel, or both fuels, but not natural gas alone.
Diesel engines, unlike gasoline engines, work based on the ignition of diesel under pressure. While a spark plug is needed to ignite gas, causing the pistons to move, diesel ignites when compressed by the cylinder.
The natural gas is injected before the diesel fuel in the duel-fuel engine process and essentially thins or cuts the diesel fuel. Dual-fuel generators generally operate in a sweet spot of a natural gas-to-diesel ratio, where the cost saved by adding natural gas to the mixture outweighs the added cost of having to compress the thinned out mixture more before combustion. Some duel-fuel engines substitute as much as 70 percent natural gas into the mixture. Substitution rates also vary according to the quality of the natural gas. Users can add more high-quality natural gas to the mixture than they can low-quality natural gas.
Duel-fuel generators effectively cut down on costs, as natural gas costs much less than diesel in some markets.