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Consider cogeneration for savings!

Cogeneration is the simultaneous generation of electricity and heat power, in a single process from the same fuel.  Cogeneration is not new.  Thomas Edison's first electric generating plant used combined heat and power generation.  The principal of co-generation is simple.  Conventional power generation on average is only 35% - 40% efficient.  Up to 65% of energy potential is released in waste heat.

Out of 100% of the BTUs in diesel fuel only a bit more than 35% is converted to electricity.  35% is expelled out of the radiator as heat and the remaining 30%+ is heat lost through the exhaust and radiant heat.   A 12kW genset can produce up to 22,500 BTUs of recoverable heat per hour from the radiator when running under load.

A cogeneration system, as we build them, consists of a engine which powers your generator to produce electricity and a waste heat recovery system to capture heat from the water cooling system and exhaust. Energy efficiency can be more than doubled with co-generation.

Until recently cogeneration implementation has been limited to large industrial applications and commercial facilities. Our implementation of cogeneration would be termed as micro cogeneration or micro CHP (Combined Heat and Power) production.

Harvesting heat before it is expelled from the radiator is the simplest and easiest method of micro cogeneration.  This is because it doesn't affect the flow of water and air through the radiator and it does not affect engine performance.  Because water cooled engines manage their heat at the thermostat you can't take too much heat from the engine by tapping heat beyond the thermostat.  Harvesting heat directly from the engine block is also safe needing only a heat sensor to avoid taping too much heat and it is inexpensive.

Depending on your application, the integration of power and heat production into one on-site cogeneration system can quickly generate savings of up to 35%. The more heat energy you are able to utilize the more you can save.  The best candidates for co-generation are those that can utilize the most heat energy.  From owners of factories to remote camps, clients are taking advantage of co-generation.  Thermal energy is most frequently used for space and water heating, however commercial applications for the use of heat energy abound.


Our longest running and most durable generators units are powered by Perkins, Lombardini, Cummins and Kubota diesels.  You can expect at least 30,000 hours before requiring a rebuild.  That's three and a half years of continuous running 7/24.  We manufacture generators using these engines and many others.

Our co-generation solution:

We’ve developed a solution which:

  • Is easy, simple and requires little or no maintenance.
  • Does not rely on additional infrastructure for safety or controls.
  • Will not damage the generator if other downstream systems malfunction.
  • Is not dependant on downstream systems (will not cause malfunction or shutdown if there is a downstream leak or a circulating pump fails).
  • Is extensible:  The heat exchangers, spliced into the coolant line, remain in place and can operate without damage (brazing problems, metal stressing...) even if there is NO water being pumped into them on the secondary side.  Of course if you allow the secondary system to freeze damage will be done to the generator's heat exchange system.
  • Is able to use normal and proven, simple equipment (regular household hot water heaters can store the heat).
  • Is able to produce the greatest return on your investment. 

Our system with a high efficiency heat exchanger within the coolant circulation system is all of the above.  If sufficient heat is not removed from the water within the heat exchanger to your heat reservoir, the excess heat is safely pumped out of the radiator into the air.  Circulation and heat management are already in place as is shutdown protection should heat be too great within the engine (standard on all of our generators). 

You must design your own secondary system with safety systems within the secondary system  because input heat is at 160-180 deg F and must be managed carefully.  If your system doesn't have capacity or isn't sufficiently protected for pressurization something could pop, even if the temperature is not at boiling point.

To maximize heat capture for cogeneration and get more energy out of the generator the regular engine mounted fan can optionally be replaced with an electric fan and separate heat sensor on the radiator.  This may provide as much as 1-1.5kW additional power from the engine/generator because there’s no fan for the engine to push.  This additional modification will also “save” more heat for co-generation, not expelling it into the atmosphere until safety and engine heat management require additional heat dissipation.  This modification includes an electric fan replacement and sensor/relay installation within the radiator.

The manifold and engine casing depend on airflow for some cooling.  The alternator cooling fan pushes a significant amount of air.  Unless the generator is located in a small enclosed space, sufficient air movement is created, avoiding problems.

 

Heat capture from the exhaust system

The exhaust system dissipates of almost 30% of the BTUs  burned within a generator.  This heat would otherwise also be lost.  The BTU from exhaust gas for a 12kW diesel genset running at load is approximately 14,000 BTU/hr.


Design Considerations:

  • Requires a separate circulation system for both heat capture and secondary system.
  • Requires management of excess heat not absorbed by the heat sink.
  • Requires additional heat sensing, heat overload safety shutdown (otherwise a steam explosion could result).
  • If too much heat is extracted before the muffler a (smelly) tar like residue may be condensed within the muffler as exhaust gas condenses and mixes with hydrocarbon residue.

This system, while not rocket science, is not fool proof primarily because safety systems for heat dissipation must be incorporated.  It is not as cheap and easy as capturing heat from the engine coolant system but it provides additional “free BTUs” of heat for a relatively small investment.

This second heat capture system must be kept separate from the heat capture system from the coolant system because the radiator and fan capacity supplied is insufficient to remove this additional heat through the radiator should it be required to do so.

We have water cooled exhaust manifolds for several engines and can have a water cooled manifold designed for any engine available.  Double wall, water cooled exhaust stacks and pipes are also available.

Heat Utilization and Storage

We like to keep things as simple and inexpensive as possible.  Exotic systems and technology require longer pay-back times.  For example, heat storage can be as simple as a one or a series of household water heating tanks if you want to start of as simply and cheaply as possible. 

Cogeneration can reduce power generation costs by diesel generator down to the current cost of grid electricity. We invite you to call us to assist you in making your electrical generation solution more economical.

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Last modified: September 21, 2017