Evacuated tube solar collectors

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Technical information on KSR10 evacuated tube solar collectorsTechnical information on KSR10 evacuated tube solar collectors

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Evacuated tube solar collectorsHewalex KSR10 – basic data

KSR10

KSR10 2xKSR10

Optical efficiency 78.0 %

Heat loss coeff. a1 1.27 W/m2K

Heat loss coeff. a2 0.0012 W/m2K2

Stagnation temperature 303 oC

Gross surface area 1.823 m2 3.646 m2

Aperture surface 1.014 m2 2.028 m2

Weight 30 kg 60 kg

� Copper absorbers

� Direct flow technology

� Titanium oxide TiNOX® coating of the absorber

� Vacuum 10-6 mbar (0.1 Pa)

� RAL 7022 powder coated housing

� Warranty: 10 years

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Evacuated tube solar collectorsHewalex KSR10 – distinguishing features

� The high-performance evacuated tube solar

collector with direct flow through absorbers

� 1.8 mm borosilicate glass tube

with double-sided anti-reflective coating

� TiNOX® absorber’s layer: αααα=95%, εεεε=5%

� Mounting on planes with no inclination(also on the facade or horizontally on the roof)

� The possibility of rotation the tubes by 25o for

optimum absorbers’ position

� The inverted manifold enables quick removal

of glycol from the collector in case of

overheating

KSR10

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Evacuated tube solar collectorsHewalex KSR10 – maximum durability of glass-to-metal connections

� Patented glass-to-metal connection

� Metal disc embedded in glass - copper pipe passes

through the elastic disk

� Mechanical resistance to critical pressure and steam

bursts (cavitation) (confirmed by the test of 1000 thermal shocks according to EN12975 – coolingthe stagnating collector with the cold water)

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Evacuated tube solar collectorsHewalex KSR10 – maximum vacuum tightness

� Vacuum 10-6 mbar (0,1 Pa), (environment for comparison 100.000 Pa = 1000 hPa)

� Maximum vacuum tightness thanks to the patented combination of glass-to-metal

� The use of getter („degasser ”) – based on barium compounds

� Barium layer actively absorbs CO, CO2, N2, O2, H2 and H2O

(gases as a residue of the manufacturing process)

� Getter – as an indicator of the vacuum� chemical reaction in case of damage to the

pipe and the air supply giving off white layer on

the surface of the inner tube

Unsealed evacuatedtube

Getter

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Evacuated tube solar collectorsHewalex KSR10 – higher solar radiation transmittance

� Glass with a low iron oxide content

� An additional layer of anti-reflex (AR) increases solar radiation transmittance by

about 5%

� AR area in nanotechnology (silicates - SiO2)

� Mechanical durability and resistance to hail (test: hail 150g)

With AR layerWithout AR layer

Tra

nsm

issiv

ity

Wavelength µm

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Evacuated tube solar collectorsHewalex KSR10 – the flow of heating medium

� Concentric pipe with direct flow

� Vacuum tubes can be rotated by 25o

� The free flow of steam downward during overheating

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Evacuated tube solar collectorsHewalex KSR10 – Comparison of different types of evacuated tube collectors

Collector with direct flow Heat pipe

� The difference in the operating efficiency between the collectors (direct flow

compared to the heat pipe) of the same manufacturer (e.g. Narva, Kingspan) is

4÷6%

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Evacuated tube solar collectorsHewalex KSR10 – stagnation structure and behaviour

� Lack of long-term overheating –

glycol is pushed out the absorber

when even small amount of water

vapour is formed in the tubes.

KSR10

Standard� Risk of long-term overheating –

the glycol is trapped in the absorber

and causes prolonged boiling of the

fluid. Risk of the glycol degradation

due to large amount of water vapour

formed.in the tubes.

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Evacuated tube solar collectorsFlat plate or evacuated tube collector?

ηηηη = 71,0%Q = 426 W/m2

ηηηη = 58,2%Q = 349 W/m2

ηηηη = 50,1%Q = 301 W/m2

ηηηη = 45,2%Q = 271 W/m2

ηηηη = 35,6%Q = 213 W/m2

-18%

-29%

-36%

-50% 2-w

all e

vacu

ated

tu

be

low

eff

icie

nt

colle

cto

rs

� A number of evacuated tube solar collectors obtain lower thermal efficiency than a

group of good-quality flat plate solar collectors. The question arises whether their

use is justified.

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Evacuated tube solar collectorsFlat plate or evacuated tube collector?

Example: SUMMER

Example: WINTER

+30oC

-10oC

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Installation options of KSR10 evacuated tube solar collectorsInstallation options of KSR10 evacuated tube solar collectors

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Types of mounting bracketsMounting brackets for KSR10 evacuated tube

� Types of mounting brackets

Universal Handle Adjusting Handle Universal Construction

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Installation options of KSR10 evacuated tube solar collectors

� Facade mounting is the least benefical for the annual heat yields

� Annual yield is decreased by around 30%

compared to optimum orientation

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Installation options of KSR10 evacuated tube solar collectors

25o

25o

� The rotation of the evacuated tubes can improveenergy yields of the collectors.

� Maximum rotation angle - 25o

shading!

Rotation>25o Rotation 25o

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Installation options of KSR10 evacuated tube solar collectorsFor the slope inclined less than 30o

45o45o 90o90o

� Installing the collectors on the facade is advantageous in the followingsituations:

- the collectors are located in areas with heavy snowfall

- solar installation is intended for central heating support- it is necessary to reduce overheating during the summer- shading of the facade - protection from sunlight

- high buildings (strong winds)

� Daily maximum temperatures depending on the inclination of the collector(based on computer simulation):

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Installation options of KSR10 evacuated tube solar collectorsFor surfaces inclined less than 30o

Source: heizungsbau-ritter.de, Augusta Solar

� Horizontal mouting does not reduce significantly annual heat yields (about -10%)

� Adverse conditions in the areas of heavy snowfall

� The preferred solution for multi-storey buildings – reduction of stresses

on the roof. For horizontal mounting the ballast stress is even several

times lower.

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