Residential solar thermal power plant

Abstract

A high-efficiency residential solar thermal power plant for economically generating power from solar-thermal energy, using a parabolic trough mirror having a longitudinal focal axis, for concentrating sunlight, a timer rotator for rotating the mirror about the focal and longitudinal rotation axis to follow the sun, and a heat collector surrounding a flow channel that preferably has an oblong cross-sectional shape with a major axis aligned with a longitudinal plane of symmetry of the parabolic trough mirror. The heat collector is coaxially positioned along the focal axis of said mirror to receive concentrated sunlight so that a working fluid is heated and provided for use through an outlet end of the heat collector.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation-in-part of prior application Ser. No. 10 / 835,665, filed Apr. 30, 2004, by Charles L. Bennett, and incorporated by reference herein.STATEMENT OF FEDERALLY SPONSORED DEVELOPMENT[0002]The United States Government has rights in this invention pursuant to Contract No. W-7405-ENG-48 between the United States Department of Energy and the University of California for the operation of Lawrence Livermore National Laboratory.FIELD OF THE INVENTION[0003]This invention relates to solar-thermal energy systems. In particular, the invention relates to a highly efficient residential solar thermal energy collection, storage, and utilization system having a parabolic trough-type solar concentrator rotatably mountable on a preferably fixed structure, such as a residential rooftop, and a tubular heat collector coaxially positioned to receive concentrated sunlight from the concentrator, with the concentrator and collector sha...

AI Technical Summary

Benefits of technology

The numerical values in Table 1 for conventional parabolic troughs are taken from the Sargent Lundy report for 2004 parabolic trough technology. The net efficiency advantage of the present invention, i.e. the product of all the individual efficiency factors, is shown in the last row in the table.

[0016]Since there is little in the current configuration that incurs additional cost relative to those well known in the SEGS plants, it is possible to estimate the cost of electricity by scaling the conventional SEGS cost by the inverse of the relative efficiency factor from Table 1. Assuming no significant increase in capital costs, the Levelized Electricity Cost (LEC) is estimated to be cut from 10¢ / kWh to 6¢ / kWh. In the residential application, the economic value of the heating derived from the cooling water feed to the steam engine can be estimated based on the quantity of avoided heating fuel. This economic value is approximately 2¢ per kWh of heating energy. The heating energy derived from cooling the engine is approximately double the power produced by the engine. Reducing the LEC cost by the economic benefit derived from water and space heating leads to a cost for the electric power that is less than 4¢ / kWh. Since this cost is much less than the retail price of electric power, approximately 10¢ / kWh for a typical customer in Northern California, this shows that residential solar thermal power based on the configuration of the present invention is indeed economically competitive.

Problems solved by technology

Despite over a century of attempts to make solar power commercially viable, solar energy currently makes up an insignificant proportion of per capita energy supply.

This has been due primarily to performance and cost inefficiencies of existing solar energy collectors, concentrators, and interfaces to heat storage media which have prevented widespread adoption and use for commercial and residential applications.

This cost is much greater than the cost to generate electricity by burning coal, which is approximately 3¢ / kWh.

One particular limitation of currently available solar collectors / concentrators, however, is their relatively low thermal gathering efficiency, which is the ratio of the thermal heat delivered by the heat collecting element relative to the solar heat incident on the concentrating mirror surface area.

This efficiency is low primarily because the solar concentration factor for these collectors is relatively low.

Another limitation associated with the relatively low concentration factors of parabolic trough collectors is that the axial length of the collector relative to the concentrator aperture width is quite large.

Another efficiency loss factor that is characteristic of the current state of the art parabolic trough collectors is associated with their horizontal deployment.

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