*3.2. The Design of the New System*

At the idea generation phase of the design, several ways were investigated to fulfil the functional requirements. This is the phase where designers look at all kinds of materials (look and feel [48], recycled or bio-based, shapes (Nature-Inspired Design) [47], and systems (C2C, Life Cycle Thinking). Designers focus on maximum value for the stakeholders. User groups are asked for their preferences.

The eco-burden of concepts at the idea generation phase are normally dealt with by gut feeling, however, this gut feeling is often not fully in line with the reality of LCA. Since the eco-costs of materials weigh heavy in the total eco-costs of the manufacturing of physical products, the LCA-based materials selection app [43] has been developed to give guidance to the designer. When transport and/or energy in the use phase is important, the LightLCA version of the app is required. With the aid of such an app, the environmental aspects of the design are readily available "at your finger tip", so that the designer can focus on the most important aspect of the design at this stage: the creation of value.

In the case of the street lighting system in Rotterdam, the Customer Perceived Value relative to the base case was tested in a small user group for five design concepts: (1) surrounding light attached to the walls of the houses; (2) bamboo posts; (3) Arc light hanging above the street; (4) lamps attached to trees; (5) rooftop-mounted lamps. The rooftop-mounted lamps, see Figure 12, scored the best. A comparison with the base case is shown in Figure 13.

**Figure 12.** Light design proposal with small and asymmetric beam to avoid light shining into houses.

**Figure 13.** The rooftop lighting system (without PV cell) compared to the base case (one street one year).

An important design issue of Figure 12 is the equal distribution of light, which is a major aspect of the perceived value of street lighting. Shades of shadow cause feelings of unsafety. The combination with trees in the street requires special attention in the system design.

Interesting observations in Figure 13 are: (1) the production costs of the rooftop system are not lower that the production costs of the lamp post system, however, the installation costs are lower; (2) the eco-costs of the rooftop system are considerably lower; (3) the replacement of the PL fluorescent lamps by LED results in less electricity (less costs as well as eco-costs); note that these savings could have been realised with a new lamp post system as well; (4) the benefit of the new system compared to the old system might be used to compensate the house-owner (in this case a housing association) for using the roof.

At a later moment in this project, in the concept development stage, the rooftop-mounted lamps were combined with one PV cell on the roof, a logical system extension in regard to sustainability. The comparison of such a system with the bases case is shown in Figure 14.

**Figure 14.** The rooftop lighting system, with one PV cell, compared to the base case.

In the EVR approach, the cost savings of the PV cell (the delivered electricity) is depicted in an extra line at the end of the curve: line 7 + 8. This line has the same slope as line 4, since they are both electricity. At the end of line 7, the amount of electricity that is used by the lamp, is delivered by the PV cell. Line 8 depicts the overproduction of the PV cell. An interesting issue of Figure 15 is how to divide the benefit of a lower Total Costs of Ownership of the new system (compared to the base case) between the house-owner and the resident of the building (to compensate for the extra burden caused by the municipality). Such a division is arbitrary, and will result from negotiations, but the point between line 7 and line 8 might be a logical choice: the benefit for the resident is the overproduction of the PV cell.

**Figure 15.** A prototype of set 2 PV cells plus lamp.

It is obvious that the owner of the building, in this case a housing association, might take the opportunity of installing extra PV cells. That is kept outside this analysis, but is shown in Figure 15: the first prototype of a set of 2 PV cells plus lamp. This prototype has been redesigned for a test pilot in the Marconistraat 43 in Rotterdam (an industrial area). The test pilot is still operational.
