Economic Evolution

Empirical progress in manufacturing processes is frequently displayed by means of a "learning" or "experience" curve. Conventionally, such curves are plotted using logarithmic axes, to show per-unit cost versus cumulative productio n volume. Most often, such a plot will produce a straight line over a very large range of actual production volumes an d unit costs. The slope of that line, expressed as the percent of cost remaining after each doubling in volume, is calle d the "progress ratio." (Since a progress ratio of 100% would represent no learning -ire., zero cost reduction-it would perhaps be better called a "lack-of-progress ratio.") Most manufactured goods are found to yield progress ratios between 70% and 90%, but there appears to be no generally applicable rule for assigning a priori expectations of progress ratios for a given process.

Figure 1 shows the experience curve over the past 20-some years for PV module prices versus total sales. Price an d total sales are used as proxies for cost and manufactured volume because the actual cost and production informatio n for the entire industry is not available. Note that, although the plotted data comprise a number of technologies, th e dominant technology-crystalline silicon—has set the pace for the price-volume relation. Therefore, this figure mos t closely represents an experience curve for crystalline silicon PV, and this curve was used within the Technolog y Characterization for Residential PV systems. The 82% value falls within the range typical for manufactured goods , and the projections of crystalline-silicon module sales and prices provided within that TC are further supported by a "bottom up" analysis of the industry.

PV Module Price Trends

Installed Modules (MWp) □ Data source - Strategies Unlimited T M- Peterson, EPRI

Figure 1. Learning curve for crystalline-silicon PV.

A major departure from the historical trend could be caused by emergence of a fundamentally new technology wher e the learning process would need to begin anew. Both thin-film and concentrator PV are likely candidates for just such a fundamental technology shift. Because historical data are not available, a great deal of uncertainty exists regardin g the future costs of thin-film and concentrator PV systems which are so dependent on R&D funding and for which much industry data is proprietary.

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