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Title: Evacuated flat-plate solar collectors

Abstract

A structural support system is disclosed for use in an evacuated, flat-plate, solar collector to eliminate the problem of stress fractures in a glass cover plate. Nonlinearly spaced supports are used within the collector to dampen vibrations in the glass cover and to prevent overdeflection before buckling or stress fractures occur.

Inventors:
Publication Date:
OSTI Identifier:
5980470
Patent Number(s):
US 4289113
Assignee:
IFI; EDB-82-038741
Resource Type:
Patent
Resource Relation:
Patent File Date: Filed date 27 Jul 1979
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; COVERINGS; STRESS INTENSITY FACTORS; EVACUATED COLLECTORS; SUPPORTS; FLAT PLATE COLLECTORS; DESIGN; FRACTURES; EQUIPMENT; FAILURES; MECHANICAL STRUCTURES; SOLAR COLLECTORS; SOLAR EQUIPMENT; 141000* - Solar Collectors & Concentrators

Citation Formats

Whittemore, P.G. Evacuated flat-plate solar collectors. United States: N. p., 1981. Web.
Whittemore, P.G. Evacuated flat-plate solar collectors. United States.
Whittemore, P.G. 1981. "Evacuated flat-plate solar collectors". United States. doi:.
@article{osti_5980470,
title = {Evacuated flat-plate solar collectors},
author = {Whittemore, P.G.},
abstractNote = {A structural support system is disclosed for use in an evacuated, flat-plate, solar collector to eliminate the problem of stress fractures in a glass cover plate. Nonlinearly spaced supports are used within the collector to dampen vibrations in the glass cover and to prevent overdeflection before buckling or stress fractures occur.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1981,
month = 9
}
  • Measurements in Solar House I at Colorado State University have provided comparison data on space heating, water heating, and cooling by systems in which flat-plate collectors and evacuated tube collectors were used. Data were procured on 47 days during operation of the flat-plate collector and on 112 days when the house was heated or cooled by the evacuated tube collector system. It was concluded that the system comprising an evacuated tubular collector, lithium bromide absorption water chiller, and associated equipment is highly effective in providing solar heating and cooling to a small building, that it can supply up to twicemore » the space heating and several times the cooling obtainable from an equal occupied area of good quality flat-plate collectors, and that a greater fraction of the domestic hot water can be obtained by supplying its heat from main storage. The cost-effectiveness of the system, in comparison with one employing a good flat-plate collector, can be determined when commercial pricing data are made available.« less
  • Measurements in Solar House I at Colorado State University have provided comparison data on space heating, water heating, and cooling by systems in which flat-plate collectors and evacuated tube collectors were used. Data were procured on 47 days during operation of the flat-plate collector and on 112 days when the house was heated or cooled by the evacuated tube collector system. It was concluded that the system comprising an evacuated tubular collector, lithium bromide absorption water chiller, and associated equipment is highly effective in providing space heating and cooling to a small building, that it can supply up to twicemore » the space heating and several times the cooling obtainable from an equal occupied area of good quality flat-plate collectors, and that a greater fraction of the domestic hot water can be obtained by supplying its heat from main storage. The cost-effectiveness of the system, in comparison with one employing a good flat-plate collector, can be determined when commercial pricing data are made available. A summary of monthly and annual energy use for space heating, domestic hot water (DHW) heating, and space cooling is presented. The collector performance is presented. The first two months of data were obtained with the system employing flat-plate collectors, whereas heating and cooling during the following nine months were supplied by the evacuated tube collector system.« less
  • Basic test results are given for a flat plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and one coolant flow rate. Collector efficiency is correlated in terms of inlet temperature and flux level.
  • In stationary heat-loss experiments, the thermal losses by gas conduction of an evacuated flat-plate solar collector (EFPC) were experimentally determined for different values of interior gas pressure. The experiments were carried out with air and argon in the pressure range from 10{sup {minus}3} to 10{sup 4} Pa. For air, loss reduction sets in at 100 Pa, whereas at 0.1 Pa heat conduction is almost completely suppressed. Using argon as filling gas, gas conduction is reduced by 30% (compared to air) at moderate interior pressures of 1,000 Pa. With decreasing pressure this reduction is even greater (50% reduction at 10 Pa).more » A theory was developed to calculate thermal losses by gas conduction in an EFPC: Fourier`s stationary heat conduction equation was solved numerically (method of finite differences) for the special geometry of the collector. From kinetic gas theory a formula for the pressure dependency of the thermal conductivity was derived covering the entire pressure range. The theory has been validated experimentally for the gases air and argon. Calculations for krypton and xenon show a possible gas conduction loss reduction of 60--70% and 75--85% (with respect to air, depending on gas pressure), corresponding to a reduction of the overall collector losses of up to 40%.« less
  • New comparative tests on two different types of solar collectors are presented in this paper. A standard glazed flat plate collector and an evacuated tube collector are installed in parallel and tested at the same working conditions; the evacuated collector is a direct flow through type with external compound parabolic concentrator (CPC) reflectors. Efficiency in steady-state and quasi-dynamic conditions is measured following the standard and it is compared with the input/output curves measured for the whole day. The first purpose of the present work is the comparison of results in steady-state and quasi-dynamic test methods both for flat plate andmore » evacuated tube collectors. Besides this, the objective is to characterize and to compare the daily energy performance of these two types of collectors. An effective mean for describing and analyzing the daily performance is the so called input/output diagram, in which the collected solar energy is plotted against the daily incident solar radiation. Test runs have been performed in several conditions to reproduce different conventional uses (hot water, space heating, solar cooling). Results are also presented in terms of daily efficiency versus daily average reduced temperature difference: this allows to represent the comparative characteristics of the two collectors when operating under variable conditions, especially with wide range of incidence angles. (author)« less