Could a High-Efficiency Engine Make Your House a Hybrid?

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When you think of home energy generation, your mind immediately goes to solar power. But what if there was a generator you could run at home that would be cleaner than many of the United States power plants? A new stationary engine from German automotive supplier Mahle promises to do just that. The single-piston natural gas powered engine promises record setting efficiency for spinning a generator, while also using waste heat to replace your home furnace and water heater.

  • German engineering powerhouse, Mahle has just unveiled a stationary engine which runs and natural gas.
  • The engine could be used in homes to generate electricity, while waste heat is used to warm the house and replace the home’s water heater.
  • Mahle states the single-piston internal combustion engine operates at roughly 30-percent efficiency, before recovering waste heat.
  • Localizing the generation of electricity would cut out the power loss associated with normal power transmission.

Mahle, with the help of a team of partners, has created a more efficient engine to be used in a home power generation system. The system not only provides electricity by burning natural gas, but also replaces your furnace and water heater.

The single cylinder engine was designed from the beginning for static installation, yet uses some tricks that could make vehicle engines more efficient as well. Mahle claims the engine itself is 20 percent more efficient than even the best current engines.

Mahle Jet Ignition cylinder headMahle Jet Ignition head ignites a small amount of fuel in a separate chamber before shooting it into the main combustion chamber. This allows more precise control of the ignition event, as well as providing a higher energy ignition for fuels like natural gas. (Photo: Mahle)

Natural gas is an obvious choice for use in a home generator, most houses already have a line coming in. Although already so prevalent, it is a tough fuel to design for. While it ignites easily, it burns slow and inconsistently. Its combustion is highly sensitive to temperature and pressure variations. In some cases, natural gas can burn so slowly, that complete combustion is impossible at higher revolutions
per minute (rpm). If the temperature is low enough, the flame can actually burnout before completion.

To fight this, Mahle is employing its Jet Ignition, pre-ignition chamber. This positions the spark plug in a chamber, along with a fuel injector, outside the main combustion chamber. Another injector sprays fuel into the combustion chamber, like in normal direct-injection engines, but that mixture is lit be flames shooting out of the jet ignition chamber, rather than a spark. There are multiple advantages; including the ability to add heat to the combustion chamber and allowing for leaner air-fuel ratios.

Mahle found operating at 900 rpm to be optimum for energy output efficiency. The rotational speed, roughly equivalent to most ICE car engines’ idle speed, generates lower frictional losses. The lower engine speed also allowed the use of lighter pistons and connecting rods. Since this is a designed for static installation, engineers were able to optimize everything for that specific rpm, whereas car engine designers have to compromise over a wide rpm range.

The engine is just part of what Mahle refers to as a compound heat and power (CHP) system. Most engines throw away heat both in the form of cooling and exhaust. The CHP system collects that heat and can either supplement or even replace a home’s water heater and furnace. Mahle claims the its system is 80% energy efficient.


The United States is a long way off from switching over to all renewable energy sources. We need to act now to slow climate change. Installing solar panels on your rough is probably the best way to lower your carbon and greenhouse gas emissions, but in some areas, it may not be possible to run your house all year on just solar. Mahle’s CHP system would be an ideal supplement as part of a hybrid approach at powering a house in the most efficient way possible.


SAE Technical Paper on the Mahle engine technology

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