How It Works


The Prometheus Turbine ORC  is based on the Opcon Powerbox ORC, which is a stand-alone power-plant, that recovers heat from waste water to generate electricity, and does so with an amazing small, low temperature volume of waste heat water. 

Because the Prometheus Turbine ORC is based on the Opcon Powerbox ORC the way it works is explained first.

Picture 1 - Flowchart Opcon Powerbox ORC at Munksjö Aspa Bruk Sweden

Opcon Powerbox ORC recovering energy from waste heat waterHow the Opcon Powerbox ORC works
The waste heat water flows through an boiler, through which a fluid with a boiling point lower than water is pumped. See picture 1.

In the boiler, the waste heat water vaporizes the fluid which expands in a turbine driving a generator and generates electricity.

Next, the spent vapor exits the generator's turbine and runs through the condenser, turning it back to a fluid and is recycled back into the cycle. The cooling water used to cool the spent vapor is used in the industrial process.

It is very efficient. For instance, the Opcon Powerbox ORC at the Munksjö Aspa Bruk pulp mill in Sweden, converts a 340 m³/h and 81ºC hot waste water flow into 675 kW (gross output, net output is 580 kW because ± 100 kW of power is needed for pumps etc.).

Source: Brochure with he Munksjö Aspa Bruk pulp mill case study and other documents can be downloaded here.

Now, the Prometheus Turbine ORC is exactly like the pulp mill's Opcon Powerbox ORC (same boiler , condenser etc.) and works in the same way, but uses the Kanthal electric heating cassette as a heat source. See picture 2.

Picture 2 - Flowchart Prometheus Turbine ORC (Powerbox ORC using electric heating cass
ette as heat source)

Flowchart Prometheus Turbine ORC (Powerbox OCR using electric heating cassette as heat source) recovering energy from hot air


Energy Efficiency


The Opcon Powerbox ORC at the Munksjö Aspa Bruk pulp mill in Sweden, needs a 340 m³/h and 81ºC hot waste water flow to generate 675 kW gross / 580 kW net.

The Prometheus Turbine ORC uses a Kanthal made electric heating cassette as a heat source, which can heat a 1250 m³/h air flow to 200ºC, consuming 100 kW of power. See pictures  3 and 4.

Picture 3  -  Kanthal electric heating cassette Picture 4 - Needed power for different temperatures
Kanthal made electric heating cassette

Source picture 2 & 3: Kanthal brochure (direct download)
Energy consumption of electric heating cassette for different temperatures

The electric heating cassette's airflow is more than twice as hot , and almost four times as large as the pulp mill's waste water flow.

Because of this, and the fact the Prometheus Turbine ORC uses the same boiler etc., The Prometheus Turbine ORC should be able to generate at least the same the electricity output (675 kW gross / 580 kW net) as the Opcon Powerbox ORC used at the Munksjö Aspa Bruk pulp mill. Click here to compare pictures 1 and 2 side by side. Also see table 1.

The net power generation of the Prometheus Turbine ORC should be 480 kW (580 kW net minus the 100 kW power requirement of the Kanthal electric heating cassette).
 
Table 1
Variables Powerbox ORC at pulp mill
Heat source: waste water flow
Prometheus Turbine ORC @ anywhere
Heat source: air flow electric heating cassette
Volume of  flow 340 m3/h 1250 m3/h
Temperature of flow 81°C 200°C
Gross power 675 kW  675 kW*
Parasitic power for pump etc. 100 kW 100 kW
Power electric heating cassette - 100 kW
Net power 580 kW 480 kW*

*There are good reasons to assume the gross or net power of a Prometheus Turbine ORC, will be higher than 675 kW or 480 kW.

Why?

i) The air volume heated by the electric cassette is larger and also the air temperature is higher compared to the waste water's volume and temperature, so a larger and hotter vapor can be produced, driving a larger and more powerful generator.

ii) The power needed by the heating cassette is based on heating air at room temperature (±21ºC). The air exiting the boiler is likely to be warmer because it was 200ºC when it entered the boiler vs. the 81ºC of the waste eat water. Because it can be recycled into the electric heating cassette, less electricity is needed to heat the to 200ºC.

For better understanding please take a look at picture 5 (a Opcon Powerbox ORC's high flow waste heat example), which shows that a net power generation of almost 800 kW is possible by recovering energy from a 125ºC hot, and 450 m³/h large waste heat flow.

Picture 5 - High flow waste heat example Opcon Powerbox ORC

High flow waste heat example for Opcon Powerbox ORC

Source picture 5 is a screen shot from the Opcon Powerbox OCR brochure which can be downloaded here.

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