Recovering Waste Heat From an Engine Powered Gen-Set

The benefits of recovering waste heat from an engine powered gen-set.

In this article we look at the benefits of converting a typical reciprocating engine driven generating set into a Combined Heat & Power (CHP) system, simply by recovering ‘waste heat’ from the engine and converting it into a valuable energy source.

Why recover heat from a gen-set?

Every engine powered gen-set produces heat. It’s a by-product of the combustion process and once the engine is started, is generated from every area of the unit. Most ‘power only’ gen-sets are quite inefficient in operation, as only around 30% of the fuel energy put into the engine is converted to power. The majority of the fuel energy is converted to heat and lost to the atmosphere.

The benefits of waste heat recovery

Around 50% of all fuel energy used in the engine can be recovered as heat. This is, in effect a ‘free’ energy source, as it requires no additional fuel input, yet can recover a massive amount of energy. Recovering this ‘waste heat’ also has the effect of increasing the gen-set’s overall efficiency from around 30% (power only) to around 80% (combined heat and power). Recovered heat can be used for a wide range of domestic, commercial or industrial uses, including district heating and hot water for residential developments, space heating in commercial premises, process heating for a wide range of industrial applications, generating additional electricity, in conjunction with a Stirling engine, or even running a chiller for comfort cooling.

Waste heat recovery potential

Recovering waste heat from a gen-set is quite straightforward. It involves the installation of heat exchangers to recover the ‘waste heat’ energy that can be harvested from various parts of the engine, which is then used to heat a water circuit. Heat can be recovered from most areas of the engine, including the exhaust system, the engine cooling circuit, oil lubrication, fuel systems, plus intercooled combustion air from the turbocharger.

A ‘total solution’ approach waste heat recovery

As around 55% of the engine’s total waste heat can be recovered from the exhaust stream, exhaust gas heat recovery is an extremely efficient method of converting a gen-set into a CHP system. However, that still leaves a significant amount of heat that can be recovered from other parts of the engine, including 24% from the engine’s cooling circuit; 12% from intercooled charge air; 9% from the engine’s lubrication system. Bowman are one of the few companies that can offer a complete range of heat exchangers and oil coolers to recover waste heat energy from every part of the generating set’s engine and can advise on the most appropriate heat recovery options available for a customer’s particular requirements.

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