7 replies to this topic

[SaRaRa]

The exhaustion of natural resources in combination with an increase in population, consumer demands, more intense climatic phenomena and stricter regulations (should?) force companies to take sustainability issues in all its aspects more seriously.

A tool to quantify some aspects of sustainability is Exergy analysis. But how much do companies really know about it? What is it actually? Is it employed in practise by the Food Industry or is it just a nice theory to discuss while drinking organic wine?

Food for thought and a poll to see where we are!



Enjoy!

[Simon]

To be honest I was about to edit the topic title - I thought you had spelled ENERGY incorrectly.

So what exactly is EXERGY?

Regards,
Simon

[SaRaRa]

Exergy is a thermodynamic concept and it can be considered as the quality of energy. It comes in many forms namely physical and chemical. For a definition I will just use our friend wikipedia:

"In thermodynamics, the exergy of a system is the maximum useful work possible during a process that brings the system into equilibrium with a heat reservoir.^[1] When the surroundings are the reservoir, exergy is the potential of a system to cause a change as it achieves equilibrium with its environment. Exergy is the energy that is available to be used. After the system and surroundings reach equilibrium, the exergy is zero. Determining exergy was also the first goal of thermodynamics."

An example: One could use electricity (pure quality of energy) to cook food but (common logic indicates that) it would not be very "sustainable" (and smart) to produce electricity from food.

It seems a rather abstract concept to grasp at once but in the end it can be quite useful. Useful in terms that one can evaluate quantitatively the performance of unit operations. Due to unavoidable irreversibilities 100% sustainability in a given process can never be achieved but it can at least be improved. Exergy analysis can be a tool to spot inefficient steps even when they seem energetically very efficient (but not necessarily sustainable). It wont provide solutions though. Those will come with the innovative spirit, knowledge and imagination of the analyst.

Edited by SaRaRa, 06 February 2012 - 12:14 AM.

[Rodriguez-Gonzalez]

Interesting conversation, I have learned about the term in energy management and food engineering books.

There are related methods to analyse energy use and find saving opportunities.

I have heard about the terms in engineering conversations as well.

What I haven't seen is if they use it for auditing energy management systems.

Are you interested in applying the concept?

Edited by Rodriguez-Gonzalez, 10 February 2012 - 04:53 AM.

[Simon]

Can you give an example of its practical application.

Regards,
Simon

[Rodriguez-Gonzalez]

As defined initially I understand that is a energy analysis based on thermodynamic properties. Therefore, it will require to measure physical properties (nutritional content) accurately to be able to get precise efficiencies.

There are several examples out there on its applications to food manufacturing. I see that its application is in two main areas: unit operation improvement and life cycle analysis. Like food safety assessments it can be helpful to identify areas of improvement to focus innovation efforts.

[SaRaRa]

Hello again,

Some examples found on the web:

2006 - Exergy analysis (improving thermal processes)

Exergy analysis of thermal processes and systemswith ecological applications

2009 - Energy and exergy analysis of a steam power plant in Egypt

2011 - Energy and exergy analysis of thermal power plants: A review

2011 - Design and exergy analysis of a thermal power plant using different types of Turkish lignite

I am sure you can find a lot more examples online.
I also find the following rather interesting to read. I suggest it to everyone:

1993 - Exergy, ecology and democracy: Concepts of a vital society or a proposal for an exergy tax



Cheers!!!

Edited by SaRaRa, 26 April 2013 - 06:26 PM.

[Rodriguez-Gonzalez]

This one is interesting too.

Exergy analysis: Atool to study the sustainability of food supply chains
http://www.sciencedi...963996905000761