Re: hybrid, off-grid, diesel generator

[elnav]

Win your question asking for a comparison of hybrid, off-grid, diesel generator and conventional generator,technically has many possible interpretations and as many answers. A complete answer would fill a book. Especially when you ask for a technical answer. Diesel versus conventional generator. The obvious answer is the kind of fuel used but diesel engines tend to last three times as long between service intervals than comparable power gasoline engines. However Gasoline engines are convertible to run on propane, natural gas, or methane. All of the gaseous fuelled engines have spark ignition and thus run at lower compression compared to diesel which is compression ignition. Diesels can be converted to run on vegetable oil derivatives. Both diesel and gasoline engines are capable of running a fuel mixed with ethanol. Perhaps this is where you got the ‘hybrid”label from.

One difficulty with diesel engines especially those running vegetable derived fuels has to do with low ambient temperatures. When cold such fuels tend to reach a gel point at much higher temperature than gaseous fuel ‘gasoline’ type engines. At that point the fuel does not flow and you see engine stoppages or not even starting.

It is common procedure to have electric fuel heaters on diesel engines. In fact most road vehicles include a glow plug start sequence for cold weather starts and my ford truck had heaters in both fuel filter and the pipe inline between lift pump and the injection pump. The electrical energy required for this heating may be too much for a limited capacity off-grid system with a depleted battery bank. My recommendation would be to use a gasoline engine for cold weather starting. However since gasoline is relatively expensive this fuel option may not be as economical in the long run. Much depends on your location and climate. Where I live we see -30 C temps sometimes for a week or more on end and diesels are really hard to start. Now you need to consider an insulated generator building or else other means of pre-heating the diesel for a cold start. Propane suffers from a similar issue. The vapor point of propane at which it volatizes is -34 C but above that there is a point where the vapor cannot develop enough pressure in the tank to get a motor going. Natural gas is okay that way but you may find it difficult to get natural gas in an off-grid location.

I’m still not sure where the ‘hybrid’ label comes into play. Are you asking to compare ‘hybrid’ with off-grid? Or hybrid generators with conventional generators?