Low-Cost Distributed Solar-Electric Technology

Artin Der Minassians
(Professor Seth R. Sanders)
University of California Energy Institute (UCEI) Project No. 2514

In this project, we plan to investigate the feasibility of a distributed generation technology based on low-concentration-ratio non-imaging optical concentrators [1], used in conjunction with moderate efficiency integrated thermal-to-electric energy converters. The latter device is intended to be based on a Stirling engine design [2, 3] incorporating integrated electric generation capability. A specific innovative contribution to the Stirling engine technical area is in the conception and deployment of a multi-phase multiple-free-piston machine. Refer to Figures 1-3 for a sketch of the proposed device. We note that flat panel photovoltaic generation technology is available at roughly a cost of $5/Watt, and that it is believed in the energy community that a similar technology offered at roughly $1/Watt would lead to widespread deployment at residential and commercial sites. Thus, a project goal is to consider cost and focus on complete system designs that meet or exceed the cost goal of $1/Watt. We intend to target the concentrator-collector operation at moderate temperatures. Furthermore, these low ratio concentrators admit wide angles of radiation acceptance and are thus compatible with no diurnal tracking, and no or only a few seasonal adjustments (Figure 1). Thus, we do not anticipate any costs or reliability hazards associated with tracking hardware systems. We are outlining a strategy for exploiting solar resources in a cost effective manner. We believe the cost of the technology based on output power per dollar is the most important parameter, as opposed to efficiency. In contrast, photovoltaic devices based on silicon technology have needed to achieve high efficiency because of the inherent cost of the silicon wafer area.

Figure 1: Solar collector schematic. Rectangular region incorporates Stirling engines and linear alternators as shown in Figure 2.

Figure 2: Three-piston Stirling engine linear alternator schematic configuration. Details are shown in Figure 3.

Figure 3: Technical drawing of one piston connected to the linear alternator.

W. T. Welford and R. Winston, High Collection Nonimaging Optics, Academic Press, Inc., 1989.
G. T. Reader and C. Hooper, Stirling Engines, University Press, 1983.
G. Walker and J. R. Senft, Free Piston Stirling Engines, Springer-Verlag, 1985.

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