PV-CHIMNEY

Abstract

The present invention is in the field of an improved naturally ventilated façade with incorporated PV that can provide heating and ventilation and can provide electricity. Especially for buildings receiving high amounts of sunshine and in particular when such buildings need ventilation such systems can be applied advantageously.

Claims

1. A modular structure for attaching to a wall comprising and enclosing at least one PV-module attached to at least one spacer, the spacer providing a distance of >5 cm of the back-side of the PV-module from the wall, the PV-module comprising an array of at least 2*2 cells, comprising at least one duct at least partly enclosing the at least one PV-module, the duct providing a distance of >5 cm of the front-side of the PV-module at least one adaptable inlet, wherein at least one inlet is located at the bottom part of the duct, at least one adaptable outlet located at the top part of the duct or in an outside of the duct, wherein the inlet and outlet are in fluid connection with at least one duct, wherein the vertical structure is adapted to provide a convective air flow over the front-side and over the back-side of the PV-module and through the duct and inlet and outlet, and a controller for opening and closing the at least one adaptable inlet and at least one adaptable outlet.

2. A structure according to claim 1, wherein the structure provides passive Heating, passive ventilation, and passive air conditioning (HVAC).

3. A structure according to claim 1, wherein the at least one inlet or at least one outlet comprise a closure.

4. A structure according to any of the preceding claim 1, wherein the at least one inlet is adapted to be in fluid contact with a at least one opening provided in a building wall.

5. A structure according to claim 1, wherein at least part of the vertical structure is.

6. A structure according to claim 1, wherein the at least one inlet or at least one outlet comprise a variable opening.

7. A structure according to claim 1, comprising at least one fastener for attaching to the wall of a building.

8. A structure according to claim 1, comprising a heat exchanger for stripping heat from the air flow, or a heat absorber, a phase change material, or a heat storage, or a combination thereof.

9. A structure according to claim 1, wherein a cross-sectional shape of the duct is selected from triangular, hexangular, square, rectangular, oval, circular, and combinations thereof.

10. A structure according to claim 1, wherein the duct is made of glass, an optical converter, a Fresnel lens, a gradient index lens, an axicon, a diffractive material, a parabolic concentrator, a reflector, and combinations.

11. A structure according to claim 1, wherein the PV-module comprises solar cells selected from interdigitated back contact solar cells, thin film solar cells, silicon based solar cells, Copper Indium Gallium Selenide thin film cells, and combinations thereof.

12. A structure according to claim 1, wherein the duct comprises an inlet at a base area thereof.

13. A structure according to claim 1, wherein the duct has a height of >1 m, a depth of >20 cm, and a width of >100 cm, and wherein the height:width is from 4:1 to 1:1.

14. A structure according to claim 1, wherein the convective air flow is a passive convective air flow.

15. A structure according to claim 1, wherein the at least one PV-module is located at >5 cm from a back from the structure.

16. A method of operating a modular vertical structure according to claim 1, comprising providing said vertical structure, converting light into electricity, providing a passive convective air flow over the PV-module and through the duct and inlet and outlet.

17. The method according to claim 16, wherein the vertical structure is provided below a roof line.

Description

FIGURES

[0030] The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying figures.

[0031] FIG. 1-3 show set-ups of the present invention.

[0032] FIGS. 4a-b show experimental results.

DETAILED DESCRIPTION OF THE FIGURES

[0033] In the figures:

[0034] 100 modular structure

[0035] 1 PV-module

[0036] 2 adaptable inlet

[0037] 3 adaptable outlet

[0038] 4 duct

[0039] 4a outside wall duct

[0040] 4b front duct air flow channel

[0041] 4cback duct air flow channel

[0042] 5 spacer

[0043] 8 closure

[0044] 9 heat absorber

[0045] 11 opening

[0046] 12 facade

[0047] FIG. 1 schematically shows a duct 4 surrounding PV module 1, inlets 2, a closure 8, and outlet 3.

[0048] FIGS. 2a-d shows a side view, further showing openings 11 in the wall and heat absorber 9. In FIG. 2b an outer wall 4a (typically glass) of duct 4 is shown, with two air flows passing by PV-module 1. Also façade 12 is shown. FIG. 2c shows also cooling elements, in this case water pipes 9. Top water pipes are cooler than low water pipes. FIG. 2d shows a duct, attached to a (n existing) wall 11, wherein PV-module 1 is spaced apart from the wall by spacers 5, and spaced apart from the front side of the duct 4 by selecting the length of spacers 5.

[0049] FIG. 3a shows four layouts (“1” to “5”) tested. “1” is a prior art layout, “2”-“4” layouts according to the invention with varying depth of air flow channels 4b and 4c respectively, and “5” is a layout of a PV-module directly mounted on a wall. The height of the chimney was 10 m, a width 1.2 m, a depth 0.4 m, and the chimney was oriented southward. FIG. 3b shows an experimental set-up showing a glazing, a PV-module, spacers, and a wall. FIG. 3c shows a thermal node model with the front glass part 4a of the duct, air flow channels 4b and 4c, PV module 1 and façade 12. Details of this experiment can be found in a paper entitled “Photovoltaic Chimney: Thermal modelling and concept demonstration for integration in Buildings” of Lizcano et al. A maximum width was determined by the size of the PV module which is 2 m. The width of the frame is an additional 0.1 m on both sides of the PV module resulting in a total width of the structure of 2.2 m. The height affects both the mass flow and the temperature distribution of the concept. Ideally, the height is as high as the façade of a building. The channel depth was varied between 0.1 m and 0.4 m in total, the aim of the experiment was to validate the model, and then use it to predict the best location for a PV module. Layer thicknesses were selected to be as close as possible to a real application. A glass-glass PV module of 8 mm thickness is used as front or middle layer. When the PV is placed in the middle, a hardened glass sheet of 8 mm thickness is used as front layer. Finally the back layer were MDF plates of 18 mm of thickness, insulated with 60 mm of thick polystyrene to simulate an insulating building material. The sides were closed with plastic sheets to prevent horizontal draught. Layers were placed as vertical as possible, and inclination readers were taken at each new set of data collection. 1000 W/m2 light was provided.

[0050] The environmental temperature was measured for different layout setups. It was found that there is a maximum difference of 6 K with a cavity depth of 0.1 m and the PVC layout located in the middle of a 0.48 m chimney cavity. A lower ambient temperature increases the difference in temperature with respect to the air within the cavity. This results on higher mass flow. However, this effect was found negligible compared to the effects of the cavity depth. With a PV-module located in the front, against the duct panel, the temperature difference was only a few K. A larger or smaller cavity depth than 0.1 m decrease the temperature effect significantly as well. Similar results were found for the relative humidity, varying between 25% for the best layout (0.1 m cavity depth) and 40% for the worst layout (PV-module in front). Also the temperature of the PV-module itself was measured and showed similar results as above. (about 20 K difference in temperature). Such large differences are rather unexpected. So a channel depth of 20 cm±5 cm was found the best, with the PV-modules located substantially in the middle thereof.

[0051] The highest flow velocity was obtained close to the PV module (about 3 m/s), dropping to close to zero in the right middle of the channel closest to the wall, and rising to about 0.5 m/s close to the wall, and close to the PV-module (about 6 m/s) at the side closer to the duct wall, dropping to about 1 m/2 in the left middle of the channel closest to the duct wall, and rising to about 7 m/s close to the duct wall, for a given case.

[0052] Heat flows for the present system were about 2-4 times as high (up to 5600 W/m, for the left channel) as prior art systems (about 1400 W/m), and again channels with a depth of about 20 cm with the PV-module in the middle performed best. Also mass flows were about 2 times better (about 0.25 kg/sm).

[0053] The PV-module temperature dropped from about 110° C. for a PV-module attached to the duct wall to about 85° C. for the present invention.

[0054] The performance of a PV-chimney was carried out by comparing it to the case of a PV-façade for a three story construction in Amsterdam, The Netherlands. The façade measurements, on both cases were assumed 10 m by 10 m, oriented towards South. A basic sensitivity analysis of the heat flow generation and electricity production was performed for both the PVF (front) and the PVC (channel) cases. The first step was to study the effect of the channel depth on both variables. The depth was varied from 0.2 m to 1.02 m in steps of 0.04 m. It was found that at smaller depths, heat flow generation changed significantly until it reached a plateau at 0.2 m. From this depth onward, the increase on heat flows grows slightly until a depth value of 0.4 m. The PVC, due to its configuration, presents a higher heat flow than the PVF. However, the PV modules on a PVC work at higher temperatures when compared to the PVF, which reduces their electrical performance. Experiments were performed with the aim to find the best position of the PV module inside the channel. As in the case of the cavity depth, both Heat flow and electricity production were studied. The modules were located from 0.01 m from the front glass to 0.01 m of the masonry wall with steps of 0.01 m. An optimum for heat flow production was found when the PV modules are located near the middle of the cavity, slightly closer to the front glass (FIG. 4a). To maximize electricity production, the middle of the cavity also yields the highest values, slightly closer to the masonry wall (FIG. 4b).