Considerations towards a mature design of sustainable PV powered products

1.1 General system design considerations

In general one can say that in designing PV powered Products; a good balance has to be found between its sustainability, its functions and user context including ergonomics, and its overall design quality. Taking for granted that the use of PV powered products contribute eventually towards a more sustainable energy consumption concept, one could concentrate on the remaining subjects.

To answer what ‘mature and sustainable design’ is all about, one should focus on the following consideration:

a) Design Quality:

• Users become aware of ‘quality only in depth’, they will not judge a product for its pure surface beauty. As a result one of the considerations in sustainable product design will be that the appearance of PV cells for the long term should not the prominent factor of design. The PV cells simply have to perform well in the intended application but they should neither be allowed to interfere with the design freedom of shape nor with the user friendliness. An example in architecture, PV tiles with colour of normal tiles. It will not be obvious at first glance that the roof is something special. In other words a virtually invisible PV application. Of course if the purpose is to show the use of PV on the roof, this example will not be applicable.

• To get rid of the predicate ‘just a gadget’ the added value of the additional use of PV cell must be apparent.

b) User friendliness or Ergonomical Design Quality:

• The use and integration of PV cells in products must not introduce additional inconveniences such as for example in PV torch where the flat PV cells hamper a good grip.

• By introducing PV energy, the battery will work for a longer time. The common approach could then be to integrate more functions into the products, nullifying the energy gain. In maturely and sustainable designed products, all these additional functions must be implemented in such a way that the user can select which function is needed at that moment and be able to shut down the other functions.

c) Sustainable energy matching:

• To be able to claim sustainability at least there must be proper matching between the energy and cost payback time of the used PV cells and the economical time of the product concerned. As a consequence fancy, sexy and trendy designs are by definition not sustainable. Most today trendy designs will be outdated tomorrow ready for disposal. Quite often in these cases the incorporated PV cells still need years to function to meet their payback target.

• Proper sustainable energy matching means a systematic approach towards energy efficiency improvement. For instance reducing the energy loss introduced by ‘stand-by’ [Kan, 2002].

• Battery powered products with sustainability in mind must facilitate the use of rechargeable batteries. There is however a discrepancy between primary non rechargeable batteries on one side and rechargeable secondary batteries on the other side with respect to the voltage delivered namely 1.5 V versus 1.2 V. This consideration therefore has two aspects namely: environmental and ease of use of the products. . Historically the primary non-rechargeable penlight batteries for example were designed to deliver voltages at multiples of 1.5V, while the rechargeable penlight batteries deliver only a voltage at multiples of 1.2V. Products that can only function in a voltage range limited by multiples of 1.5 V and which are not designed flexible enough to be able to function also at the lower voltages as usually delivered by rechargeable batteries are therefore by design not sustainable. Parallel to this observation, to promote sustainable design, there must be a growing awareness at the battery manufactures that somehow there must be some international standardization. A logical step would be to have the rechargeable batteries also at multiples of this 1.5 V.