DE102020002895A1 - PVT solar collector for year-round generation of electricity and heat - Google Patents

Abstract

The present invention uses the synergies of meeting the energy demand on or on a building through photovoltaics and solar thermal energy. The subject matter of the invention is a photovoltaic solar thermal (PVT) collector 23 for use on or on a building, which is preferably operated with a seasonal heat store, and in addition can contribute that this solar system with storage through multiple use of surface, construction material and heat output is also economical in the cold season, whereby the collector on the front is transparently thermally insulated by between the front of glass 1 and the heat exchanger 4 with the at the same time as thermal Absorber acting solar cells 6 a narrow space 10 with z. B. vacuum, while the other sides by pasting z. B. are thermally insulated in the insulation 12 of a building. After installation on or on a building, the collector becomes part of a heat-insulating building envelope that is impervious to rain and snow. With its glass-flush frame 11, this PVT collector promotes the residue-free drainage of rainwater and rapid slipping off Snow. - Its frame 11 enables independent assembly and dismantling of each individual collector. Overheating is prevented by shaping the heat exchanger 4 and the cooling channels 16 in the rear thermal insulation 12 through thermostat-controlled emergency cooling - preferably for optimal yields of heat (T +) and electricity ( PV) - even if the system is partially shaded - the flow of the heat transfer medium as well as the inverting of the electricity are regulated individually for each collector.

Description

The present invention relates to the fields of photovoltaics ( PV ) and solar thermal (ST), which combined as PVT enable electricity and heat generation from solar radiation with a component that z. B. can be inserted into facades or roofs.

So far there is PVT technology

• • with non-insulated PVT modules, which can heat the domestic water in addition to the electricity generated during the warm season when the wind is low, and whose electrical efficiency is slightly improved through the more intensive (liquid) cooling,
• • with non-insulated PVT collectors, whose heat exchangers not only use the heat generated by converting light into electricity but also serve as air heat exchangers at night and in winter - preferably with a larger surface for air flow, whereby the low-temperature heat obtained can be used by means of a heat pump is made (heat pump PVT) - a very good increase in the yield on the available irradiation area, as long as the electricity for the heat pump does not run out when the heat demand is highest -,
• • with partially insulated PVT collectors, whose front-side heat losses in the transition periods and in the cold season hardly allow any heat yield.

Purely solar thermal collectors - ST - are known with thermal insulation all around, also with transparent insulation and vacuum insulation on the front.

The above-described PVT modules (optimized for power generation) and PVT collectors (optimized for heat generation) are designed like normal PV modules or solar thermal collectors - when optimized for heat generation, they - like solar thermal collectors, have an overheating problem if the heat consumption fails ( Stagnation), which not only significantly reduces the yield for photovoltaics, but can also affect the PV service life.

• - Bei der erfindungsgemäßen Konstruktion des Randverbunds zwischen Glasscheibe und Wärmetauscher sorgt eine elastische Sicke entweder im Randstreifen an der Glasscheibe oder am Rand des Wärmetauschers dafür, dass die großen Wärmedehnungen elastisch abgefangen werden.
• - Die lokalen Spannungen wegen unterschiedlicher thermischer Ausdehnungskoeffizienten müssen durch geeignete Material-Paarung von Glas und Metall minimiert werden, wie das auch bei Vakuumröhrenkollektoren möglich ist.

In the case of vacuum flat-plate collectors, it has been shown that the vacuum maintenance is not sufficient after a shorter or longer period of operation, because the elastic seals used are not resistant to the effects of the weather and due to the constantly changing expansion of the front glass and rear material, so that the air that has penetrated with a constantly connected vacuum pump is to be pumped off.

• - In the inventive construction of the edge bond between glass pane and heat exchanger, an elastic bead either in the edge strip on the glass pane or on the edge of the heat exchanger ensures that the large thermal expansions are elastically absorbed.
• - The local stresses due to different thermal expansion coefficients must be minimized by a suitable material pairing of glass and metal, as is also possible with vacuum tube collectors.

The present invention firstly solves the problem of providing PVT collectors which, even without a heat pump, enable year-round heat output in Central Europe or in similar climatic zones, in order to reduce the costs for seasonal heat storage. The better the collector thermal insulation, the higher the heat yield at which the heat transfer medium temperature exceeds the minimum usable temperature.

Second, this PVT collector is designed in such a way that, in the event of stagnation, emergency cooling limits its absorber operating temperature, which means that electricity generation is no longer significantly impaired.

The subject of the invention is a photovoltaic-thermal (PVT) collector for use on or on a building,
comprising a front made of glass 1 and solar cells facing the front 6th which also act as a thermal absorber and on a rear heat exchanger 4th are upset
The collector is designed in such a way that it is thermally insulated on all sides after installation on or on a building,
the thermal insulation on the front is transparent by placing between the front of glass 1 and the heat exchanger 4th a narrow space with the solar cells 10 with a vacuum or a heavy noble gas (e.g. krypton or argon) is filled.

• - auf der Vorderseite transparent und
• - auf der Rückseite - Kosten und Bauvolumen sparend - durch Einfügung in die wärmedämmende Gebäudehülle 12
• - ersatzweise in eine wärmedämmende Tragschale bei Anwendung z. B. auf Flachdächern.

By coating 2 the front glass and / or the solar cells 6th will heat losses ( R. in 1 ) reduced due to reflection and thermal radiation, but this coating is allowed to allow light to enter L. not affect it too much.
The invention thus relates to a solar thermal collector for use on or on buildings, the one with photovoltaic solar cells 6th as an absorber from solar radiation L. both electricity PV as well as warmth T can win, so a known PVT collector. This will heat out all year round Solar radiation gain through very good thermal insulation on all sides:

• - on the front transparent and
• - on the back - saving costs and building volume - by inserting it into the heat-insulating building envelope 12
• - Alternatively, in a heat-insulating support shell when using z. B. on flat roofs.

The thermal insulation on the front side is preferably carried out using a high vacuum, which largely prevents heat transport through thermal conduction and convection 2 of the front glass 1 kept small, whereby this coating must be as permeable as possible for the incoming sunlight.

In the case of vacuum insulating glass windows (VIG windows), manufacturing and operating experience could be gathered, which according to the invention can be adapted for the flat-plate collector design.
In order to absorb the atmospheric pressure from the inside, tiny support bodies 1 mm high and less are used in VIG windows - at regular intervals, which only marginally affect the view. Such support bodies are state of the art and can also be used according to the invention for PVT collectors. However, selective support on solar cells should be avoided if possible.

The solar cells 6th can be crystalline solar cells or thin-film solar cells. Thin-film solar cells that are applied to a substrate can be placed directly on the heat exchanger 3 be applied. Crystalline solar cells are typically glued or laminated.

The support body 3 can preferably be placed on the heat exchanger forming the rear wall of the collector 4th be supported,
z. B. with 'quarter cells' - eg approx. 160 mm x 40 mm - the support is laid in the spaces between these strip-shaped solar cells.

Alternatively, the support body 3 be supported on the solar cells, in which case the distance between the support bodies is preferably approximately 1 cm, and preferably a flat contact is formed in order to prevent damage to the solar cells. The resulting heat conduction can be limited to a few percent of the absorber surface.
Through regular small bumps in close succession in the underside of the front glass 1 the support is then designed in such a way that the compressive forces are still bearable even for brittle silicon cells. These support bodies can also be made of elastic plastic that is printed onto the glass pane and can withstand solar radiation without outgassing or softening.

It is particularly advantageous for the assembly of the collector to form the support bodies according to the invention as projections on the glass pane in a grid-like pattern.

Alternatively, the support bodies can be provided with one or more heat-resistant insulated heating wires 3 are formed, which are preferably in the spaces between the solar cells 6th on the heat exchanger forming the back wall of the collector 4th are supported. Such a heating wire can be designed similar to a rear window heater in a car, it is useful for defrosting snow and ice in winter operation.
In addition, for the flat-plate collector design, the features of the glass-flush edge design are in accordance with the utility model application DE 20 2014 004 801 useful to ensure that snow slides off for winter operation.

The heat is drawn off, for example, via a pipe system with direct flow through it - 4th - e.g. as with conventional solar thermal collectors - which is preferably connected as a parallel connection - called "harp" - many evenly distributed tubes with an approximately oval cross section 6th - is performed.

An oval cross-section of the cooling channels in the embodiments according to the invention has a larger surface area than a circular cross-section with the same cross-section. With appropriate dimensions, this feature enables such a pipe to withstand the change in volume of freezing water without bursting open. This also applies to an oval tube that is flattened on the narrow side.

Another reason for the design of the cooling channels according to the invention is their dual function as cooling ribs for emergency cooling, because in the event of stagnation, essentially only the rear of the module is available for heat dissipation. The surface of the cooling fins and the narrow web between two cooling fins must be able to give off the heat to the air in the emergency cooling duct without excessively increasing the absorber temperature.

So that this system can be operated with water without antifreeze, it must be designed as a drain-back system, whereby these tubes and their collector pipes are designed with the necessary inclination so that the collectors themselves can be mounted horizontally and the system "looks tidy" .

Another way of removing heat is to use heat pipes as heat exchangers. The condenser ends of these heat pipes can be 'dry' - but with thermal paste - to a z. B. trapezoidal manifold can be connected, which can be made thermally insulated in the areas of its surface that do not touch the collector.

These collecting lines can also be designed as a support frame for the collectors and, in the case of building-integrated construction, such as the collector, are inserted into the heat-insulating building envelope.

The PVT collector should therefore be designed in such a way that it can be inserted into a heat-insulating building shell in a rain- and windproof manner.

This is preferably achieved by a profile of the edges (or at the edges between the front and back) of the collector, which prevents restraint forces that occur during movements of the building envelope z. B. can occur through wind or thermal expansion. This is, for example, on all four edges of a frame profile 11 as in 2 possible. The edge is preferably designed in such a way that each of the 4 edges, but at least 2 opposite, lower or upper edges can be used when laying on a wall or roof.

Another requirement for the design of the edges of the collector or its frame protecting the sensitive edges as well as for the supporting structure - as in 2 recognizable - results from the fact that maintenance work or damage, e.g. B. fireworks or falling bodies, each collector and its accessories must be accessible and, if necessary, replaceable independently of all other collectors.

The preferred routing takes into account the rain runoff, the induction loop-free pipe routing, optimal pipe lengths and the direction of flow on the back of the collectors for the intended emergency cooling.

Alternatively - for systems on flat roofs - a system comprising a collector according to the invention and a thermal insulation element can be used, the collector being inserted accordingly into the thermal insulation element. The thermal insulation element is optionally designed as a shell, which also serves as a support for assembly.

All thermal insulation measures should always be carried out with porous, non-combustible mineral material or as vacuum insulation. The disposal of other plastic waste is problematic enough.

1. 1. am Kollektorrahmen angebrachte Mikrowechselrichter (Hierdurch wird zugleich die Auslegung und Installation der Anlage erheblich vereinfacht.)
2. 2. Pumpen oder Regelventile für den Wärmeträgerfluss jedes einzelnen Kollektors verhindern, dass zeitweilig verschattete Kollektoren durch niedrigere Wärmeträger-Temperatur für den gesamten Wärmestrom durch die Vermischung die Temperatur absenken (Minderung der Exergie).

For building integration of the PVT collectors, the following measures reduce the influence of partial shading:

1. 1. Microinverters attached to the collector frame (this also significantly simplifies the design and installation of the system.)
2. 2. Pumps or control valves for the heat transfer medium flow of each individual collector prevent temporarily shaded collectors from lowering the temperature due to the lower heat transfer medium temperature for the entire heat flow through mixing (reduction of exergy).

Advantageous embodiments of the invention are shown in the figures.

• 1 zeigt die Leistungsflüsse und den Vorteil der Wärmedämmung von PVT-Kollektoren gemäß der Erfindung.
• 2 zeigt einen erfindungsgemäßen PVT-Kollektor 23 - hier mit direkt durchströmten Kühlkanälen 16 - in eingebauter Lage mit angrenzenden Kollektoren, Tragstruktur 21, 22 und einem Teil der Gebäude-Dämmung 12.
• 3 zeigt den aktiven Teil eines Vakuum-PVT-Kollektors: als Schnittzeichnungen
  1. a) Ansicht in Richtung der Kühlrippen, für beide Ausführungsformen, b und c) Ansicht quer zu a:
     • b) mit direkter Durchströmung der Kühlkanäle 16,
     • c) mit Wärmerohren 16, die „trocken-gekoppelt“ sind an das Sammelrohr 18.
• 4 zeigt einen direkt gekühlten PVT-Kollektor-Wärmetauscher 4 von unten.
• 5 zeigt einen Wärmetauscher 4 in Ansicht von unten mit gekröpftem festen Sammlerrohr 18 , trocken gekoppelt mit den Wärmerohr-Rippen 16.
• 6 zeigt Kühlrippen mit Kühlkanälen, die sowohl direkt durchströmt werden können oder, wenn ihre Enden entsprechend verschlossen sind, als Wärmerohr dienen.

List of figures:

• 1 shows the power flows and the advantage of the thermal insulation of PVT collectors according to the invention.
• 2 shows a PVT collector according to the invention 23 - here with cooling channels with direct flow 16 - in a built-in position with adjacent collectors, supporting structure 21st , 22nd and part of the building insulation 12 .
• 3 shows the active part of a vacuum PVT collector: as sectional drawings
  1. a) View in the direction of the cooling fins, for both embodiments, b and c) View across to a:
     • b) with direct flow through the cooling channels 16 ,
     • c) with heat pipes 16 that are "dry-coupled" to the manifold 18th .
• 4th shows a directly cooled PVT collector heat exchanger 4th from underneath.
• 5 shows a heat exchanger 4th seen from below with angled fixed collector pipe 18th , dry coupled with the heat pipe fins 16 .
• 6th shows cooling fins with cooling channels that can be flown through directly or, if their ends are appropriately closed, serve as heat pipes.

List of reference symbols

L.

Incident sunlight power

R.

light reflected and absorbed in the glass pane

PV

electrical power

T

total heat output

T +

usable power

T + is

usable power with improved thermal insulation

T-

Heat losses

T-is

less heat loss with better thermal insulation

1

viPVT collector

2

Functional layer

3

Support body, alternatively: electrically insulated heating wire

4th

Heat exchanger

5

Heat transfer cooling fin

6

Solar cell

7th

Glass-to-metal connection

8th

Bead for expansion compensation

9

Metal-to-metal connection

10

Space with vacuum or inert gas filling

11

Collector frame

12

thermal insulation on the building side

13th

Distribution pipe, collector pipe (cold)

14th

Collector pipe (warm)

15th

Pipe connection

16

Cooling duct

17th

Heat pipe condenser coupling

18th

Collecting pipe on the heat pipe condenser

19th

narrow stabilizing bar

20th

Space for microinverters

21st

vertical mounting rail

22nd

horizontal mounting rail

23

viPVT collector

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 202014004801 [0015]

Claims (6)

Photovoltaic-thermal (PVT) flat-plate collector for use on or on a building, comprising a front made of glass and solar cells facing the front, and a heat exchanger as the rear, on the smooth front of which the solar cells are applied, - where there is a vacuum or heavy inert gas in the narrow space between the glass pane and the solar cells, supported by tiny support bodies on the heat exchanger, - while the back of this heat exchanger consists of ribs through which the heat transfer medium flows inside, - whereby the heat exchanger with its cooling fins and the thermal insulation of the building - alternatively a thermal insulating shell carrying the collector - form an emergency cooling channel in which a thermostatically operated flap releases an air flow in the event of excess temperature. PVT collector after Claim 1 , characterized in that the support between the heat exchanger and the glass pane is provided by a heat-resistant, insulated heating wire, which also has the function of defrosting the glass pane in snow or frost if its low-E coating is not suitable for use as surface heating through which electricity flows. PVT collector after Claim 1 , characterized in that the support bodies are designed as projections of the glass pane, which are arranged in such a tight grid that they can be supported as point loads not only in the spaces between the cells but also on the solar cells. PVT collector according to one of the preceding claims, characterized in that it is designed in such a way that it can be inserted into a heat-insulating building envelope in a rain- and windproof manner - this being preferably achieved by a profile of the collector frame or the edges of the collector, which prevents restraint forces that occur during movements of the building envelope z. B. can occur through wind or thermal expansion. PVT collector according to one of the preceding claims, characterized in that its heat exchanger is designed so that it has collector pipes suitable for a drain-back system with water cooling. A PVT collector according to one of the Claims 1 to 4th , characterized in that the cooling fins of the collector are heat pipes, the condenser ends of which transfer the heat to a pipe system in the case of a “dry coupling”.

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