Combined Heat and Power Plant Explained

CHP aka Cogeneration plants have been in existence for quite some time now. In Ireland alone the technology
has been in use for the last three decades. However the need for them has never been in focus as at present due to the past unpleasant experiences with the fuel prices and the looming bleak global economy.

In this light it is not only important to know what your options are in reducing your production costs but also
implement them as a priority. It is no secret that fuel prices play a major role in production cost in any industry. When the oil prices are high that’s why the prices of essentials too go up. A process where the fuel usage is optimized therefore presents a viable cost cutting solution. A CHP is one such process.



The following are points that will make you understand this less understood fuel saver process.

  • Electrical Energy is produced using many a technology. The prime mover or the powering device initiating
    the process is where the fuel is consumed (if any).
  • The prime mover can be basically operated on Non Renewable Energy sources such as fossil fuels or on renewable Energy Sources such as Hydropower, wind turbines, Solar panels etc.
  • By far the most common prime movers are fossil fuel run Reciprocating engines and Turbines run on steam./The latter technology (which in most of the case operates on unclean coal) is basically for the mega scale power plants aimed at electrical power for the utility grid.
  • Up to approximately 15 MW capacities, Electricity Generators are run on Piston Type engines either Diesel Engines (Compression Ignition type) or in some cases Spark Ignition (Otto Cycle) Engines etc. This is true whether the power generation is for the utility grid or whether it is for an industry which rely on its own power for many a good reason.
  • The Compression Ignition (“Diesel”) Engines are generally run on Petroleum distillates such as no. 2 oil which is the most commonly used fuel. But it is possible to use up to No.6 oil.
  • The Spark Ignition engines on the other hand are generally run on Natural Gas, LPG and similar gaseous and volatile fuels.
  • Some Diesel Engines are designed to run on both gaseous and liquid fuels.
  • These 4 –stroke Reciprocating (ie. Piston type) engines are generally not more than 50% efficient which means 50 %  of the fuel used is wasted as heat .The waste energy does not serve any purpose and is dissipated to the environment.
  • A Heat Rate of 11,280 kj /kwh and the Thermal to Electric Ratio is 4090 kj/ kwh (1.136) is an average output that can be expected.

The 4 stroke engines are not the only type of engine that can be adopted for CHPs. The turbines too are highly
efficient thermal energy generators. These along with large reciprocating engine driven CHPs could easily be adopted for district heating systems.

The best efficiency of 4 stroke prime movers is when it is operating at 100% capacity. One important point to check when you select a CHP is the prime mover’s part load fuel efficiency as the Electrical Power Generation may not be at 100% capacity all the time.

The last listed item points out the amount of Thermal Energy available for building heating or Process heating that is just wasted in conventional power generation. The CHP is designed to harness this waste heat and provide high grade heat for your requirements.

An efficiency of up to 80% is good enough to think twice about these versatile type of power generators even at this late stage on the verge of Winter.