System Description

Sunlight:

1800 kWh/m2 -yr

(Annual Average U.S. Sunlight)

Sunlight:

1800 kWh/m2 -yr

(Annual Average U.S. Sunlight)

Fixed PV Array 20 MWP

Figure 1. 20 MWp (DC)/16 MWp (AC) grid-connected PV system schematic.

Power Conditioning Subsystem

AC-DC inverter, max power tracking

Substation (voltage control)

Substation (voltage control)

16 MW

30 GWh/yr (after power ,,t conditioning losses)

Fixed PV Array 20 MWP

18 MW Operational 33.8 GWh/yr

Figure 1. 20 MWp (DC)/16 MWp (AC) grid-connected PV system schematic.

Thin film photovoltaic (PV) systems convert sunlight into DC electricity using large-area, solid-state semiconducto r 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 i s 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 powe r 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 2-yr for a nontracking array, and varies by about 30% from this amount within the Continental U.S. [1]. For a single-axis tracking array, average output increases to about 2,200 kWh/m 2-yr and to about 2,400 kWh/m2-yr for a dual-axis system [1]. Despite the higher available energy, trackers are no t necessarily preferable, since they add cost, have moving parts, and require maintenance. In this characterization, w e describe only fixed (nontracking) systems, and we describe two levels of sunlight as input to our PV arrays: a high level (2,300 kWh/m2-yr) to characterize solar installations in areas of exceptional sunlight; and 1,800 kWh/m 2-yr as an 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 proportiona l to the amount of local sunlight. Since sunlight variation in the U.S. is about 30% from an average value, meeting low-

cost goals in an average location would qualify PV for consideration in almost all U.S. climates and most globa l locations. For example, if future PV systems were to produce electricity at 60/kWh in Kansas (U.S. average sunlight), the same system would produce electricity at 80/kWh in New York State and at 40/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 larg e 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-tem projections are all based on systems located in areas of average sunlight.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

Get My Free Ebook


Post a comment