Remember the First law of thermodynamics? Energy can neither be created nor destroyed. It can only change forms. Or, if translated into an idiot-proof rule of thumb: you can't go above 100%. Remember this? Now forget it; this law has got a loophole.

COGENERATION FACILITY AT 102% EFFICIENCY

Steve Clemens

EarthToys Renewable Energy Article
Remember the First law of thermodynamics? Energy can neither be created nor destroyed. It can only change forms. Or, if translated into an idiot-proof rule of thumb: you can’t go above 100%. Remember this? Now forget it; this law has got a loophole.
Belgian cogeneration facility above the legal limit:
102% efficiency!

By Steve Clemens


The Agfa-Gevaert Group has 140 years of experience in imaging, operating worldwide with offices in 40 countries, producing an extensive range of analog and digital imaging systems and IT solutions, mainly for the printing industry and the healthcare sector. In 2005 they decided to build their own cogeneration capability and installed 4 Caterpillar reciprocating gensets of 2MWe each, at their Belgian production facility in Mortsel. But they did not stop there. In a European first, with chp-technology partner Indea, they intergrated an innovative technology, usually reserved for gas turbine engines: an after-burner.

agfa

Since January 2007 this 8MWe cogeneration facility, fueled by natural gas, have been churning out energy at a documented efficiency of 102%, rather than the usual 85%. As if the technological wonder is not enough to boost Agfa’s and Indea’s profiles, this extraordinary efficiency number benefits from an extra financial bonus of €3,2M per year.

cat
A Caterpillar genset breaking the Law at Agfa, Belgium.

Responsible for the technological pixy dust are the use of a genset with very efficient electrical efficiency, at 40%, combined with the recuperation and re-use of all available thermal energy, both the heat condensed from the exhaust gases as the irradiative heat from the engine itself. This combo allows for a high thermal efficiency of 62%. Together: 102%

Three temperature-levels of thermal energy are produced.

First, the exhaust gas heat allows for the production of 1.25 tons of steam at 19 absolute bars, at 340°C, what computes as 965KW per engine.

Then cooling liquids from the engine, combined with an economiser from the exhaust gases, heat water up to 90°C. This results in 1.327KW thermal power per engine.

Also, water is heated up to 40°C by cycling it around the genset’s turbo, supplemented by a temperature boost from the last-stage of the exhaust gas condensers, adding another 555KW.

And finally, 200KW of irradiative energy is captured off the engine block, heating air up to 35°C to dry finished photosensitive films at the plant.

sci
Does it hurt as much if the Xray films were climate-friendly?

Generating various sources of heat are one thing, the key to high efficiency is to actually need and use this power in processes, thus offsetting other power needs. At Agfa, large amounts of various temperature inputs are required in the production of polyester films.

The afterburner.

Afterburners will typically improve gas turbines’ power output by 80%, but in a reciprocating engine the technical challenges are considerable. Their exhaust gases do not contain enough remaining oxygen to inject natural gas and have it combust spontaneously, so an extra air input is required for post-combustion. An extra 3.138KW are thus generated. But not all of it can be attributed to the cogeneration facility as extra fuel was added. A computation was worked out with the local energy (and green certificate-verifying) authorities and only 423KW are considered as part of the cogen, or for free.

graph

A fuel savings of 33%

  • To produce 1.970KW of electrical power with a conventional power plant, at 50% efficiency including T&D losses, you would consume the equivalent of 3.949KW of natural gas.

  • To produce 965KW of high-temp, high-pressure steam, with a steam boiler at 85% efficiency, you would consume the equivalent of 1.135KW of natural gas.

  • To produce 1.882KW of warm water, with a high-efficiency boiler at 90%, you would consume the equivalent of 2.091KW of natural gas.

  • To produce 200KW of warm air, with a ventilator-burner at 95% efficiency, you would consume the equivalent of 215KW of natural gas.

The above alternatives would consume a combined 7.381KW of natural gas compared to the 4.930KW for this ultra-high efficiency cogen facility, a fuel savings of 33%.

Profitable.

A yearly savings of 78.599MWh on fuel, after the legal authorities’ computation, leads to a yearly revenue from cogen-certificates of €3,2M, at about €41 per cogen-certificate. The investment for this facility is assumed to be about €8M above the business-as-usual power plant, so payback time is very short indeed!

What I particularly like about these cogeneration facilities, even if only at 85% efficiency: they can easily convert to burning biofuels, leveraging the climate change reducing potential. In case of this particular facility, a combination with sustainably produced biofuels would actually lead to negative carbon emissions or extracting greenhouse gases from the atmosphere. I would imagine thàt would unleash no small amount of gratitude from society…

Nevertheless, inspirational opportunities aside, if there is any lesson to be learnt from this story it must be that with just some political will (tradable certificates from cogeneration efficiency gains) the industry’s imagination can be unleashed, to the benefit of all.


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