GB2524026A

GB2524026A - Solar thermal panel

Info

Publication number: GB2524026A
Application number: GB1404283.2A
Authority: GB
Inventors: Nicholas Anthony Allen
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-03-11
Filing date: 2014-03-11
Publication date: 2015-09-16
Also published as: GB201404283D0

Abstract

A solar thermal panel comprising of a finned 4 capillary tube 5 inserted into multi-wall polycarbonate sheeting 2,8. The finned capillary tubes are connected to header manifolds 1. The solar panel is weather-tight and fitted with mounting points for installation. The tubes are preferably copper and the fins can be aluminum or copper and both the tube and fins may be coated in an absorber material. The finned capillary tubes are preferably contained in an evacuated tube and form a flat plate solar collector.

Description

Description Title

Solar Thermal Panel

Introduction & Background to the invention

This invention relates to a solar thermal panel. It is neither flat plate or evacuated tube type.

Nor is it made from glass. it is a capillary finned tube inserted into a multi-wall polycarbonate sheet. There is a peat. deal of energy (in the form of heat) from the sun striking the earth per square metre: the difficulty has been collecting it. Whilst the flat plate type collector tries to absorb the heat and transfer it to a circulating medium (usually water based) through a large insulated conductor plate it suffers from inherent re-radiation' losses due to the time taken for the volume of water to absorb' the sun and the poor insulative properties of fiat plate glazing. On the other hand the evacuated tube type collector tries to reduce these inherent, losses through insulating the smaller flat plate in a partial vacuum to eliminate the re-radiation. However the evacuated tube type still takes time to absorb' the sun. This time delay is known as lag-effect'. Both types, whilst excellent in the way they work, are either expensive to produce and or install or have limited use due to their design.

Statement of ffivention

To overcome these problems the present invention proposes to a solar thermal panel comprising of finned capillary tubes inserted into multi-wall polycarbonate sheeting. The finned capillary tubes are connected to header manifolds that provide flow and return connections to a solar array system. The panel is insulated and weather-tight.

Advantages of the invention The capillary finned tube solar panel overcomes a number of these difficulties. Firstly the volume of circulating medium in the capillary tube (water based in this ease) is closely matched to the heat (irradiance) from the sun (wIm2) thus increasing the absorption rate over the traditional flat plate and evacuated type collector. For example a flat-plate collector may typically have a volume of 0.5-1 litres per square metre of panel whereas the finned capillary has 0.04 litres per square metre. In other words it takes very little time for the capillary finned collector to absorb' the sun compared to the fiat-p'ate and evacuated tube type. therefore reducing the lag-effect. With the lag-effect reduced any inherent re-radiation losses are mininiised therefore making it not. necessary to be housed in an evacuated tube.

The capillary finned solar panel benefits from a number of other advantages too. The use of multi-wall polycarhonate sheeting means the panel does not have to he hermetically sealed.

The use of industry standardised sizes of the sheet mean that it can be retrofitted to existing structures and a readily stocked product is more cost effective for production. By weight polycarbonate sheet has a smaller carbon footprint from manufacture than the equivalent section of glass required for the existing type of panels. The weight of the assembled panel is less than the current types of panel, making it possible for a one-man fit'. Due to the lightness of the assembled panel the influencing factor due to load bearing of the existing structure is substantially reduced.

Introduction to the drawings

The solar thermal panel comprises of three parts. The finned capillary tube, header manifolds and multi-wall polycarhonate sheet.

Figure 1 shows two views of the solar thermal panel. The fig a showing the whole of the panel and fig b shows an enlarged view of a corner for detail.

Figure 2 shows the finned tube detail. Fig a showing the finned capillary tubes connected to the header immifold and fig b shows the single finned capillary tube detail.

Figure 3 shows (he finned tube assembly inserted in to the polycarbonate sheet in fig a. whilst fig b shows the polycarbonate sheet only.

The original drawings have been produced to full scale and the above figures have been copied to fit the views appropriately. They are not to scale but give a true representation of the original invention and the associated components.

Detailed description of the invention

Assembled Panel Referring to figure 1 the transparent encapsulation is multi-wall polyearhonatc sheeting 2.

The panel is connected into an array system by means of a flow and return utilising two of the four header manifold connections 1. The panel is insulated prior to being made weather-tight with PVC enclosures 3. It is preferable to make the header connections I, top and bottom opposite ends (TBOE) for optimum efficient. However the nature of the installation may limit the array to utilising top and bottom same end (TB SE) when making the header manifold connections 1. Fixing points are provided by means of u-chmnel bracket.

Finned capillary tube detail The capillary tube must he connected to the fin by forming. insertion or crimping. Whilst a continuous braze / soldered joint would produce the best heat absorption from the solar gain the level of distortion through this method of production would render it unusable. Referring to figure 2 the method of fabrication is that the fin 4. Typically the fin size is 0.5mm gauge aluminium or copper x rib width of polycarbonate sheet x length of panel. The fin 4 has a number of double holes' 6 spaced equally along the strip and then pressed to form an insert for the capillary tube. The capillary tube 5 is then inserted along the length of the Fin 4. Once this is complete a selective coating cm be applied. There are pre-coated selective absorber materials that are currently available that can be used as suitable alternatives. Having formed the finned capillary tubes they can be inserted into the flutes' of the multi-wall polycarbonate sheet.

Header Detail Referring to figure 2 the header manifolds 1 are 10mm OD and (he capillary tubes 1mm ID 5.

Both are made of copper. A row of holes 7 is drilled in the header tube at centres spaced equal to the finned tube centre distances when they inserted into the multi-wall polycarhonate sheet 2. The diameter for the hole 7 in the header manifold 1 is sufficient for the capillary tube 5 to pass with a small clearance as to produce a capillary brazed joint. The typical clearance is between 0.08 aud 0.022mm around the capillary tube. Given the ID of the capillary tube the hole diameter to he drilled in the header tube is indicative to the gauge of the capillary tube. Formula; hole diameter for header manifold (1) equals ID (capillary tube) + (2 x wall thickness) + (2 x 0.08). The joint is brazed using silver solder, typical content 5% Ag. Due to a copper only' joint a no-flux braze' can be achieved using a Cu/Ph type rod. To prevent the end of the capillary tube becoming blocked' during the brazing process a 6mm OD tube is inserted into the header manifold (1) to fashion a tube stop. This 6mm inserted tube also prevents over insertion of the capillary tube 5 at the hcAe 7. Finally it provides continual alignment of the finncd capillary tubes along thc manifold header 1.

Inserted Detail Relerring to figure 3 the finned capillary tubes are inserted into one of (he ayers 8, eaving the remaining layers for insulation. There can be any number of finned' inserts along (he ribs of the polycarhonate sheet: however fifty has been an acceptable limit for production purposes. Once the finned capillary tubes are inserted 8 in to the polycarhonate sheet 2 they can be connected to the header manifolds at each end 1. The number of header manifolds can vary given the area of the collector array. Figure 1 has a maximum distance of im between the header manifolds Possible modifications & Variations The fin section 4 can be made from either copper or aluminium. The copper and aluminium maybe pre-coated with selective coatings prior to the fabrication of the finned capillary tube.

The capillary tubes 5 can he varied in diameter. The definition of a capillary tube is that the OD is 4mm or less, typically 0.75-2mm ID. Thc capillary tubes Fig 2b,5 arc 1mm ID.

The number of header and footer manifolds 1 can vary from area of collector panel. Again the diameter of the header manifolds can vary.

Thc hcadcr manifolds I can he connected to thc capillary finncd tubes below the polycarbonate sheet 2 so that the panel can be placed into existing or newly installed glazing bar system to provide an integral part of the roof.

The sheet thickness, wall type. rib spacing and structure of the polycarbonate sheet can vary although the five-wall type used has proven most suitable Fig Ia, 2.

Claims

Claims 1. A solar thermal panel comprising of a finned capillary tubes inserted into multi-wall polycarbonate sheeting, wherein the finned capillary tubes are connected to header manifolds, is weather-tight and mounting points are provided for installation.
2. A solar thermal panel as in claim I, wherein the finned capillary tuhes comprise of a copper capillary tube and an aluminium (in.
3. A solar thermal panel as in claim 1, wherein the finned capillary tubes comprise of a copper capillary tube and a copper fin.
4. A solar thermal panel as in claim 1, wherein (he finned capillary tubes comprise of a copper capillary tube and a pre-coated absorber material.
5. A solar thermal panel as in claim I, wherein the finned capillary tubes are encapsulated in an evacuated tube.
6. A solar thermal panel as in claim 1, wherein the finned capillary tubes are contained in a singular flat plate collector.
7. A solar thermal panel according to any of the preceding claims, in which the capillary tube diameter is varied.

S. A solar thermal panel according to any of the preceding claims, in which the panel is constructed to he installed into a azing bar system.