Wednesday, 20 November 2013

SUSTAINABLE DESIGN GUIDE (Part VI)





6. THE SUSTAINABLE DESIGN STRATEGIES

Looking at impacts in the context of lifecycle stages is a good way to measure them, but not as helpful when actually designing or redesigning; after all, sustainable design strategies often affect more than one stage.
Let’s look at a few of the strategies that Tom and Priscilla employed during their redesign processes.


Product Design - Parametric Optimization

We’ve focused in these initial examples on parametric optimization, that is, taking specific steps to incrementally reduce material and energy impacts. This often results in quick, low-hanging-fruit reductions in the overall product impact. Here are some strategies we saw in action:

Sourcing Locally
Priscilla’s first attempt was to move the manufacturing operation closer to the region of use. As she found out, this is often highly dependent on the modes of transportation being compared, not just the distances involved. Generally speaking, the modes of transportation listed in decreasing order of environmental impact are: 
  1. Air transport 
  2. Truck transport 
  3. Rail transport 
  4. Ship transport 
Besides distance and mode, another transportation factor is the quality of the fuel used, which is also regionally dependent. Fuel sourced in Asia often has a higher sulfur content, for example, raising the acidification potential of the transport leg. It is assumed that the fuel is sourced in the region of origin for each transportation leg.
The transportation impacts of changing the manufacturing region may be outweighed by the regional differences in manufacturing, however. Manufacturing energy—in the form of thermal energy (natural gas, steam generation, etc.) and electrical energy—vary in amounts, efficiencies and sources in different regions. The grid mix in the region of manufacture has an impact on the energy and other indicators in the Manufacturing phase.

Alternate Material Selection
Priscilla’s second tactic was to find a different material for her cup. Materials that designers and engineers select should satisfy four criteria: 
  1. The material must function as intended; 
  2. The material must provide the right aesthetic, ergonomic, and other form considerations; 
  3. The material’s cost must be in the range of the product’s cost of goods; and 
  4. The material’s environmental impacts should be minimized. 
Too often, we optimize for the first three criteria and ignore the fourth. Priscilla worked through the “Find Similar” material selection tool to find a material that satisfied all four criteria.
Priscilla was quite surprised to find that High-Impact Polystyrene (HIPS) satisfied all four criteria, including lower environmental impacts, than her original PET. Sometimes our assumptions about materials—like polystyrene, PVC, or various metals—are based more on negative press than on scientific data. By working with data-driven tools like SolidWorks Sustainability, we can sharpen our intuitions about material impacts.

Lightweighting (also called source reduction)
Finally, Priscilla re-examined the geometry of the cup to see if she could use less material to hold the same volume of liquid. Light weighting, or source reduction, is one of the most common ways to optimize for greener designs, especially since this reduces overall material costs as well.
One critical consideration for load-bearing materials that are being light weighted is to ensure that the product still has enough strength to perform as intended, within an appropriate factor of safety. SolidWorks has powerful Simulation tools that can be used in concert with Sustainability to optimize strength and reduced impact, which we’ll explore in future examples.


Product Development - Fundamentally Altering the Product

Tom struggled with this level of redesign in the discussions of his functional unit and system boundary. He wanted an “interactive toy”, but is a battery-operated speaker and lights the only way to achieve interactivity? What happens to the environmental impact if the parent replaces the rechargeable battery with disposables, is drawing power from batteries “dirtier” than drawing power from the grid? And what of the batteries’ impact at end of life?
Tom could fundamentally change his product to be one that was not battery-operated, but still interactive. The only way to know if he should focus his efforts on the battery would be to include it in the environmental impact calculations. We’ll talk about ways to model this when we revisit Tom’s fire engine.


Product Innovation - Changing the System

Finally, Priscilla thought early in the process about the system in which she was producing her cup. Product innovation and system redesign goes beyond product design, and touches upon reconsidering people’s behaviours, and the way they interact with the product system. She felt that her plastic cup was not a strictly necessary product in all situations, and that perhaps a reusable metal cup would mean a lower overall impact if more people were to adopt the practice of carrying or offering these. We’ll take a look at this system redesign in the future, and consider how to compare these two models and their associated behaviours.

To be continued...

Sources: Dassault Systèmes - SolidWorks Corp, EPA.



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