Utility-scale flat-plate thin film photovoltaics

Abstract

Thin film photovoltaic (PV) systems convert sunlight into DC electricity using large-area, solid-state semiconductor devices called thin film PV modules. This section characterizes fixed (nontracking), grid-connected systems in the U.S. producing conditioned, AC electricity ( Figure 1). The system in this document is a composite based on the three most mature thin films. In addition to thin film modules, PV systems include other components: support structures, inverters if AC electricity is desired, a solar tracker if needed (not in this study), wiring and transmission, and land. Figure 1 shows the losses between each part of the PV energy delivery system: the amount of sunlight and the power and energy produced at the module level (called the system's 'peak power' when the output of all the modules is summed); and the power-conditioning subsystem (including DC-to-AC inverter) with the losses in wiring and DC-to-AC power conversion. The 'peak power' is only the starting point. By the time the electricity gets to the busbar, losses are about 20% of the initial, peak system total. These losses are taken into account in the energy and cost calculations.The system input is sunlight. The amount of incident sunlight depends on the latitude and local climate. U.S. average annual solar energy input is about 1800 kWh/m -yr for a nontracking array, and varies by about 30% from this amount necessarily preferable, since they add cost, have moving parts, and require maintenance. In this characterization, we describe only fixed (nontracking) systems, and we describe two levels of sunlight as input to our PV arrays: a high level (2,300 kWh/m -yr) to characterize solar installations in areas of exceptional sunlight; and 1,800 kWh/m -yr as an 2 2 average case, to indicate a more typical level for the U.S.The use of an average U.S. solar location to calculate cost projections for the long-term allows us to generalize conclusions about the impact of the PV characterized here. The economics of a PV system are inversely proportional to the amount of local sunlight. Since sunlight variation in the U.S. is about 30% from an average value, meeting low- UTILITY-SCALE FLAT-PLATE THIN FILM PHOTOVOLTAICS4-19 cost goals in an average location would qualify PV for consideration in almost all U.S. climates and most global locations. For example, if future PV systems were to produce electricity at 6¢/kWh in Kansas (U.S. average sunlight), the same system would produce electricity at 8¢/kWh in New York State and at 4¢/kWh in the Desert Southwest. These extremes could still provide acceptable costs, given the variation of the cost of conventional electricity (although, of course, such cost variations are unrelated to variations in sunlight). It should also be noted that the first large installations of PV are likely to be in areas of high annual sunlight (or locally high electricity prices). We will capture this by using our 'high sunlight' assumptions to describe pioneering installations by 'early adopters'. Longer-term projections are all base...