GB2103783A

GB2103783A - Solar heating

Info

Publication number: GB2103783A
Application number: GB08124414A
Authority: GB
Inventors: Jakob Hermann Flamm
Original assignee: European Atomic Energy Community Euratom
Current assignee: European Atomic Energy Community Euratom
Priority date: 1981-08-10
Filing date: 1981-08-10
Publication date: 1983-02-23
Also published as: ES8400592A1; GR78005B; ES514449A0; IT8248953A0; GB2103783B; IT1149044B; FR2511133A1; FR2511133B1

Abstract

An integrated system for solar energy collection and storage comprises a transparent protecting cover and a solar energy-absorber (2) defining a free-circulating fluid passage (4). Channels (7) connect the passage (4) with a vessel (3) containing hollow plastics spheroids (8) containing phase-change material. A bimetallic control valve (6) is provided. The inner wall of the vessel (3) is covered by a radiator surface (10) mechanically supported by metal supports (12). <IMAGE>

Description

SPECIFICATION Solar energy collector with integrated heat storage and radiator The present invention relates to solar energy collectors having integrated heat storage and radiators.

The use of solar energy for heating a structure has been utilised in many forms until the present energy crisis; solar heating for supplementing the energy supply of a building has not been economically competitive. Spiralling energy costs and shortages now make solar energy utilisation in residential and commercial structures more economically competitive. Even if economically competitive under present changing conditions, many of the prior art systems for converting the sun's energy into heat required large collectors or reflectors which were continually exposed to the elements and could thereby degrade with time.

Low temperature heat (20--300C) suffices to keep living and working accommodation at comfort level, provided that this heat can be dissipated over a sufficiently large surface area within the space to be heated. Solar radiation concentrated and stored at this temperature level in outer building walls -- could contribute significantly to space heating and/or the reduction of heat losses to the outside, when the space is heated conventionally from the inside.

A number of experimental solar heating systems with heat storage in the outer wall of buildings exist already. The best known is the 'Trombe wall'. In its simplest form this is a brick or a concrete wall behind a transparent cover. The outer wall surface is suitably prepared for solar absorption; the captured heat being stored within the wall and used for room heating or the reduction of ordinary heat losses from this room to the outside. Several modifications have been proposed in order to improve the thermal capacity of the wall, e.g. by adding volumes of water with or without latent storage materials, or to improve heat transfer to the store or to the space to be heated.

Active or passive fluid or air circulation systems have been added, as well as thermal insulation between the solar collector and the heat storage section in order to improve the overall efficiency of such a system.

Artificial shading during a hot season is usually provided by manually or thermostaticallyactivated blinds or sliding panels. Cooling during the night hours of a hot season is very limited with these systems.

Following the above reasoning a new modular wall panel system is now proposed, applicable to both existing buildings and new buildings private, commercial and/or industrial combining solar collector thermal storage and radiator characteristics. The prerequisite for the system are complete autonomy of each unit, i.e.

no auxiliary power supply or working media, hence, low installation and maintenance cost, no running expenditure; automatic and attendance free operation, using system driven controls; fixed shading to render the system inoperational during the season of low solar incidence, i.e. during the hot season; easy accessibility to replace heat storage material after its life span and using preferably a collector material with good thermal insulation characteristics.

In brief, the proposed system consists of independent building wall modules of suitable size with the following main characteristics: a conventional transparent cover on the outside; a solar collector, preferentially with good thermal insulation characteristics (optional for heat loss economy); the air, enclosed in the system, is the heat transfer medium, auto-controlled by thermostatic flap valves; suitably insulated air ducts to and from the heat storage unit, which form the interior of the wall and serve as radiator.

The storage volume is filled with a granular material of high heat capacity in the 20--30"C temperature range, preferentially an encapsulated phase change material (PCM), offering a great energy density over a small temperature swing; the voids between granules serving as air ducts, thus forming a closed heat transfer loop with the solar collector.

The surface of the storage container, facing the space to be heated, is laid out for optimum heat transport and may be varied following aesthetic needs.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows the principle of a heat storage system, in a vertical section, according to the present invention; and Figure 2 shows an embodiment of the same invention.

In Figure 1, a transparent cover 1 of glass or a plastics material, protects the inside from the exterior, and a dark, thermally insulating solar collector surface 2 covers a volume 3 in which is held a salt body with phase change characteristics (PCM) for the heat storage. Between the solar collector surface 2 and the protective transparent cover 1, a free passage 4 permits the convective circulation of the air.

Figure 2 shows a section on a vertical plane of the outer wall of a building. An insulation 5 is shown, which may be also the existing wall, where passing holes or channels 7 are provided for the circulation of the heat transfer fluid (air). A bimetallic flap valve 6 may better control this circulation. On the interior side of the insulation there is the volume 3 filled with the phase-change material 8.

Said material 8 is constituted by a salt encapsulated in plastics spheroids. The interior side 9 of said volume 3 is covered by a radiator surface 10 facing the room 1 The radiator surface 10 is held parallel to the side 9 by metallic supports 1 2 which serve also as heat transfer bridges.

Owing to the particular form of the spheroids, voids for the circulation of the fluid are present inside the volume 3, so the heat exchange may take place between this fluid (air) and spheroids.

The advantage of the proposed system are: -the proposed system can substitute modular sections of outside walls in new buildings. No structural reinforcements will be needed, as the unit weight of the system corresponds roughly to that of conventional building materials; - applied to existing buildings, the thermally insulating solar collector material will improve the heat loss economy, in addition to the thermal gains of the system; - the working fluid is unconditioned air, and hence is free of any charge; - the system is thermostatically autocontrolled and should practically need no maintenance or periodic manual interventions; - provided the PCM can be operated with very small temperature swings the system could also serve for space cooling.

Claims

1. An integrated system for solar energy collection and storage including a transparent protecting cover, a solar energy-absorbing material, a free-circulating fluid passage between said cover and said solar absorber, an insulation wall, a volume of phase change material having a free-path, closed-circuit fluid circulation, and at least one bimetallic control valve; the inner wall of said volume being freely covered by a radiator surface mechanically connected by metallic supports.

2. An integrated system as claimed in claim 1 wherein the volume of phase change material is constituted by plastics spheroids filled by a salt.

3. An integrated system as claimed in claim 1 or claim 2 wherein the at least one bimetallic control valve is operated by solar radiation.

4. An integrated system as claimed in claim 1 or claim 2 wherein the at least one bimetallic control valve is manually operated.

5. An integrated system as claimed in any one of the preceding claims wherein the metallic supports of the radiator surface act as heat transfer bridges.

6. An integrated system for solar energy collection and storage substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.