GB2058333A

GB2058333A - Solar energy collectors

Info

Publication number: GB2058333A
Application number: GB7931682A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-09-12
Filing date: 1979-09-12
Publication date: 1981-04-08
Also published as: GB2058333B

Abstract

A plate type solar energy collector has two sets of ducts each with its own header system. The ducts of each set are proportioned to provide for greater and lesser flow rates of liquid to be heated respectively and may be selectively operated to provide heated liquid at differing temperatures. One set of ducts is formed by a plurality of relatively small bore tubes 14, the tubes 14 being in thermal contact with a first absorber plate (15, Fig. 1). A second absorber plate 16, disposed on the opposite side of the first absorber plate to the tubes 14 defines a second set of ducts (17, Fig. 7). <IMAGE>

Description

SPECIFICATION Solar energy collectors The invention relates to solar energy collectors.

A problem associated with such collectors is to arranged for the correct or approximately correct temperature to be reached by the fluid being heated as the heater is in use. In some cases smallish quantities of high temperature fluid are required, in other cases greater quantities of lower temperature fluid are required and hitherto it has been necessary to design the collector for the particular application envisaged for it.

According to the invention there is provided a solar energy collector comprising an absorber plate, two sets of ducts in thermal contact with the absorber plate and two header means respectively associated with each set.

Thus the invention can provide a collector which provides for two modes of operation to suit instances in which both high and low grade heated fluid is required at one location. For example, such a collector can be used in instances in which a high grade fluid is required for domestic water heating and a low grade fluid is required for home swimming pool heating. Whereas a collector according to the invention is applicable to other situations, for the sake of simplicity it is described hereinafter in relation to a combined domestic hot water heater and swimming pool heater.

It is however also applicable to heating air for space heating within a dwelling or other building if provided with means permitting atmospheric air to be drawn through at least one of the sets of ducts.

The invention is applicable to plate type collectors of the kind comprising an extended metal or other conductive absorber sheet furnished with a plurality of fluid flow ducts extending from one end of the sheet to the other and with heater passages interconnecting and extending laterally of said ducts. In use the sheet is preferably arranged so as to be inclined with one header at the upper end and the other at the lower end and the ducts are disposed in a spaced apart array extending from one header to the other.

Preferably one of the sets of ducts comprises a plurality of metallic tubes in intimate thermal conductive relationship with spaced apart corrugations formed in the absorber plate and the ducts of the other set comprise the spaces between those corrugations.

Each duct is in good thermal conductive relationship with the absorber sheet and thus, when exposed to the heat of the sun, fluid in the ducts is heated and a flow is established from the lower header to the upper header. The ducts may comprise tubes or the like soldered or otherwise adhered to the absorber sheet and may be either on its upper face of its lower face. In other instances the sheet and ducts may be integrally united for example they may be formed as a single plastics extrusion.

The ducts of one set are preferably of relatively small cross-sectional dimensions and they together with their associated headers are used when a high temperature is required in the output fluid. On the other hand the ducts of the second set have relatively large cross-sectional dimensions and are utilised when a lower temperature output is required.

The invention is diagrammtically illustrated by way of example in the accompanying drawings, in which: Figure 1 is a front elevation of a solar energy collector according to the invention with parts of its outer components cut away to reveal the interior; Figure 2 is a plan view taken on line 2-2 of Figure 1; Figure 3 is a side elevation taken on line 3-3 of Figure 1; Figure 4 is a more detailed sectional view taken on line 4--4 of Figure 1 and drawn to a larger scale; Figure 5 is a detailed sectional view taken on line 5-5 of Figure 1 and drawn to a larger scale; Figure 6 is a detailed sectional view taken on line 6-6 of Figure 1 and drawn to a larger scale; Figure 7 is a detailed sectional view taken on line 7-7 of Figure 1 and drawn to a larger scale; and Figure 8 is a sectional detailed view taken on line 8-8 of Figure 1 and drawn to a larger scale.

Referring to the drawing, a solar energy collector comprises an outer casing itself comprising two tray-like members 9 and 10 resting one upon the other and secured together for example, by welding, about the periphery of the lower member 9.

The lower member 9 is filled with polystyrene foam or other insulating medium 11 in which is embedded a lower inlet header 12 and an upper outlet header 13. A plurality of relatively small bore tubes 14 extend from the header 12 to the header 13 and constitute one set of ducts for the heating of fluid which is to be raised to a relatively high temperature. Generally but not necessarily, the fluid will be water. Throughout most of its length each tube 14 is in good thermal contact with the underside of corrugations in the floor of the upper member 10, which floor constitutes an absorber sheet 1 5.

A second absorber sheet 1 6 is disposed within the member 10, it contacts the crests, as seen from the upper side, of the corrugations formed in the absorber sheet 1 5 thereby defining with the absorber sheet 1 5 a further plurality of ducts 17 respectively between neighbouring corrugations in the absorber sheet 1 5. The abosrber sheet 1 6 at its upper and lower edge is inclined so as to diverge from the sheet 1 5 to provide space near the upper edge of the collector for a sparge tube 1 8 whereby water or other liquid to be heated to a relatively low temperature may be fed into the ducts 1 7 to move downwardly between the two sheets 15 and 16.

At the bottom edge of the collector the diverging edge margin of the sheet 16 provides a sump space into which the liquid flowing downwardly in ducts 17 collects for removal by way of a drain tube 19.

The lower rim of the member 10 has a plurality of air inlet holes 20 formed in it. It will be appreciated that in use the collector is inclined so that the holes 20 are well above the open inner end of the tube 19 thereby avoiding the possibility of heated liquid escaping through them.

The upper edge of the member 10 is provided with an air chamber 21 with an air outlet pipe 22 at one end. Thus when the low grade heating system for liquid is not in use, air may be drawn from the pipe 22 by a suitable pump for delivery into a building for space heating therein, that air being heated by conduction and radiation as it flows upwardly through the ducts 17.

The open mouth of the member loins covered with a transparent sheet 23, which may be a sheet of a polycarbonate plastics or other suitable material which is not only transparent to light but also substantially transparent to thermal radiation emanating from a high temperature source such as the sun.

For preference the absorber sheets 15 and 16 are of aluminium or copper and have a matt black surface coated with one of the newly developed surface finishes which tend to prevent re-radiation of absorbed energy.

In practice a plurality of collectors may be utilised in a single installation with their respective header means connected each to each (in series or in parallel), depending on the total heating capacity required.

The installation could also include suitable valve arrangements to permit selection of one or other set of ducts as the operative set at any particular time. If desired the valve or valves may be automatically operated by a timer or by a relay responsive to the intensity of sunlight for the time being.

In some embodiments of the invention the absorber plate may also be utilised as a roof cladding sheet so that the collector may be integral with the roof of a building.

Claims

1. A solar energy collector comprising an absorber plate, two sets of ducts in thermal contact with the absorber plate and two header means respectively associated with each set.

2. A solar energy collector according to claim 1, wherein one of the sets of ducts comprises a plurality of metallic tubes in intimate thermal conductive relationship with spaced apart corrugations formed in the absorber plate and the ducts of the other set comprise the spaces between those corrugations.

3. A solar energy collector according to claim 1 or claim 2, including means permitting atmospheric air to be drawn through at least one of said sets of ducts to be heated therein.

4. A solar energy collector substantially as hereinbefore described and illustrated with reference to the accompanying drawings.