First, a rather simple one which has some fancy arrow heads, partly overlapping other arrows. This one is from the CEZ Energo website and just a schematic visualization of the cogeneration principle.

The next one has a strictly vertical orientation and is built from rectangles and simple block arrows. It uses the same values as in the diagram I shows in the last post. Found on the Plzenska Energetika website.

The last one can be found on the TZB Info engineering website. Actually there are two separate Sankey diagrams being compared. A left-to-right orientation, the flow quantities labels sit on the node. This is the only one drawn with a Sankey diagram software (judging from the node symbols I would say it is most likely the discontinued Sankey 3.1 by Fichtner)
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If you find other cogeneration Sankey diagrams pls drop me a line…

The other day I used the Czech term for cogeneration (‘kogenerace’) … and immediately had five new diagrams to share with you. Two of them can be found below…

As in most cogeneration schema diagrams, two energy production systems are compared in one diagram. The classic one, and the combined heat and power CHP system. Heat (teplo) and electricity (elektrina) output is set to the same size and primary energy requirement is being compared. Losses (ztráty) branch out to the other side. In the first one these two systems (found on the EkoWATT website) are shown in a vertical orientation:

The second one (from All for Power website) has a horizontal orientation:

The cogeneration system is 1.4 times more efficient (140:100) in the first diagam, the second Sankey diagram has cogeneration 1.47 times more efficient (100:68).

Two or three more to come in another post next time.

Just to get started without any further delay, here is a Sankey diagram I dug out from my collection.

Not sure on which website or in which article I found this, but it is still hosted on imageshack.

The diagram is from Poland and seems to show cogeneration. Flows represent percentages and are not always to scale (compare 10% flow ‘Straty’ and 35% flow labeled ‘Energia elektryczna’). The label “1%” on the flow for ‘Kolektor spalin’ must be a mistake, I reckon it should read “7%”.

More postings in the next days…

“The exhaust gases coming from the hood are used for the production of the steam needed to feed the YD and the other auxiliary equipment of the mill (wet strength pulper, hall ventilation). The residual energy in exhaust gases in excess from the boiler are used in order to feed a chiller unit, which in turn runs the air conditioning system of the electrical room”.

This almost symmetric top to bottom oriented diagram shows the energy in MW for a certain production capacity (details not given in the article). It is a section of the other Sankey diagram featured in the article (Fig. 3) showing the whole process including the gas turbines plant, the cogeneration hood and the waste heat boilers (omitting only the absorption chillers). Only the latter shows the reduced heat loss (see light blue arrows labeled “to atmosphere”).

As for me, that’s the kind of curves I love…

UK’s Department for Environment, Food and Rural Affairs (DEFRA) has crowned its new website on combined heat and power generation with a nice Sankey diagram.

What is CHP? “CHP systems are highly efficient, making use of the heat which would otherwise be wasted when generating electrical or mechanical power (…) and typically has an efficiency of over 80%”, the accompanying text explains.

The diagram is built similarly to this one presented in a previous post: The Sankey diagram doesn’t feature absolute figures, but flows are scaled in relation to the baseline of 100 units energy generation in a power plant and a CHP unit. In a cogeneration unit 160 units of energy would be produced at the same time. Losses are accounted for with 65 units in the CHP. To produce the equivalent energy quanities in a conventional power unit would cause losses 1.65 times higher than the energy output itself. In the boiler 25 % of the energy is lost (40 units).
Overall losses in convential generastion are 205 units compared to 65 units in a CHP.

It shows that in a cogeneration unit with recovery of heat energy from engine water cooling and exhaust gas cooling, an overall efficiency of 85,4% can be achieved, and losses can be reduced to 14,6%.

Don’t ask me what the accompanying text means, I just understand that ‘Kogenerace’ is ‘cogeneration’. Note Nov 2011: I noticed that after an update the original page with the image is not available any more on motorgaz.cz

Apart from the overall energy efficiency of 75% the Sankey diagram doesn’t show any figures. The shadow effects on the flows look funky, and add a spheric touch.

It shows the advantage of energy cogeneration plants over energy production in separate plants. From a base value of 100 a yield of 85% can be reached in cogeneration plants (35% electric energy, 50% heat energy – the original text accompanying the diagram says 30% electric energy, 55% heat energy) with 15% losses. To get the same energy amount from separate energy generation plants, the required energy feedstock is 1.48 times higher, with losses more than four times higher (63:15), especially originating from the generation of electricity.

While I am far from fostering one or the other technology with this post, I think this Sankey diagram merits special attention, because it is actually a 2-in-1 diagram (both with flow direction left-to-middle and right-to middle) and a baseline scenario comparison. A very nice idea!