A NOVEL TECHNOLOGY FOR SOLAR APPLICATIONS Cristoforo BENVENUTI. SEEC 2009 Trento 8-9 October 2009

Transcription

1 A NOVEL TECHNOLOGY FOR SOLAR APPLICATIONS Cristoforo BENVENUTI SEEC 2009 Trento 8-9 October 2009

2 Alternative route to high temperature : Decrease thermal losses! Very low thermal losses may be achieved thanks to: Vacuum It is generally assumed that: A selective coating on the light absorbers Flat panels collectors are only adequate for low temperature application High temperatures may be obtained only by light focusing In this way 300 C are at reach without mirrors The flat plate evacuated solar collector Also the diffuse light is collected, which cannot be focused The diffuse component of solar light amounts to about 30% in the best solar areas, and exceeds 50% in Central Europe 2

3 The flat plate evacuated solar collector Mean monthly diffuse radiation as percentage of mean monthly global radiation for four UK stations for each month 3

4 Direct and diffuse light components in Geneva (CH) The flat plate evacuated solar collector 4

5 Total and direct component of solar light at different locations The flat plate evacuated solar collector 5

6 Issues Vacuum => 10 tons per m 2 of glass window, the glass must be properly supported The joint between the metal frame and the glass must be vacuum tight All materials inside the panels must fulfill UHV specifications (low degassing, cleanliness) The flat plate evacuated solar collector A built-in pump is needed to maintain the vacuum for 20 years This pump must preferably be powered by sun 6

7 Is vacuum really useful? The flat plate evacuated solar collector Variations of the absorber temperature as a function of the panel pressure 7

8 Selectivity: High absorption (α) of solar (visible) light Low emission (ε) of infrared radiation For α values of 0.9 and ε values of 0.07 (at 300 C), temperatures of the order of 300 C may be obtained for absorbers blackened on both sides, and of the order of 350 C for single side blackening How important is the absorber selectivity? Calculated variation of the peak stagnation temperature as a function of the α/(ε1+ε2) ratio The flat plate evacuated solar collector 8

9 History On the ground of these considerations evacuated flat plate solar panels were built and testes in the 70s. 9The flat plate evacuated solar collector

10 Global view of the 1 st panel 3 2 The flat plate evacuated solar collector 1. Frame with spacers 2. Absorbers with coating pipes 3. Glass window 1 10

11 The flat plate evacuated solar collector 11

12 The flat plate evacuated solar collector 12

13 These prototypes were exposed to real environment conditions on the roof of a CERN building for about 9 years. Results The flat plate evacuated solar collector Stagnation temperatures of the best and worse absorbers of a panel prototype 13

14 Global view of 3m panel The flat plate evacuated solar collector 1. Frame with spacers 2. Absorbers with coating pipes 3. Glass windows 3 14

15 In spite of the good thermal performance of the panels, the addition of mirrors helps gaining on cost effectiveness and increasing the useful operating temperature, so as to cover, with the same panel, all the possible solar applications Mirors Config.1 - Bare panel Stagnation temperature ~ 320 C Config.2 - Panel with cylindrical mirrors Concentration factor 1.9 Stagnation temperature ~400 C Config.3 - Panel with cylindrical mirrors and lateral mirrors Concentration factor 3 Stagnation temperature >450 C The flat plate evacuated solar collector Different panel configurations 15

16 Thermal efficiencies of the 3 possible panel configurations The flat plate evacuated solar collector These figures represent the performance which could be obtained by implementing certified improvements. The estimate is carried out for an incident power of 1000W/m 2 and a glass temperature of 30 C. 16

17 Thermal efficiency [%] Thermal efficiencies as function of the temperature Two sides blackening of the absorber Bare panel One side blackening of the absorber The flat plate evacuated solar collector Temperature [ o C] 17

18 Thermal efficiency [%] Thermal efficiencies as function of the temperature Panel with cylindrical mirrors The flat plate evacuated solar collector Temperature [ o C] 18

19 Thermal efficiency [%] Thermal efficiencies as function of the temperature Panel with cylindrical and lateral mirrors The flat plate evacuated solar collector Temperature [ o C] 19

20 Vacuum performances After evacuation the pressure inside the panel is in the low 10-7 Torr range. Due to the progressive decrease of the surface outgassing, the pressure decreases with time to the 10-8 Torr range, and increases to the 10-6 Torr when the absorbers are heated by sun to 300 C The flat plate evacuated solar collector The temperature dependance and its evolution over about 6 months for a recent panel prototype is illustrated in fig. 20

21 The flat plate evacuated solar collector 21

22 Applications The unique feature of the SRB solar panel is that it may be used for all the Solar Energy applications, a field now covered by products of different design The SRB panel is particularly suited for applications in the temperature range C (for instance for industrial heat production and cooling / air conditioning) for which the panel performance is outstanding. For the production of electricity the SRB panel efficiency is similar to that offered by parabolic through solar fields, but the mirror geometry is much less critical and the maintenance for cleaning much reduced For low temperature applications (<100 C, domestic water heating) the SRB panel provides higher efficiencies than the existing flat panels in regions as Central Europe, where the available solar energy is reduced. The flat plate evacuated solar collector 22

23 Solar power repartition The flat plate evacuated solar collector 23

24 TWh a Potential for thermal electricity % LAND USE SPAIN FRANCE GREECE ITALY PORTUAL UK FRG Potential solar thermal electricity generation vs. present electricity demand as a function of land use The flat plate evacuated solar collector 24

25 Solar Energy Input KWh(th)/m 2.year 2300 and above 1200 to to 1100 Key general information Typical Options and outputs Electric power generation and/or hydrogen production Electric power generation ; Industrial process heat; Heating and cooling Water and/or air heating for resindential buildings and low grade process heat Estimates of Attainable Systems Efficiencies Thermal Electric to to to to 0.10 Typical Regions Desert regions of North Africa, Southwest USA, Australia, etc. Moderate regions of North and South America, Asia, Australia, and primary regions of Southern Europe, etc. Secondary regions of Europe, Asia, Africa, North and South America, etc. The flat plate evacuated solar collector 25

26 Facilities in Spain 26

27 General view of the plant Facilities in Spain 27

28 Frame welding Facilities in Spain 28

29 Glass metallization Plasma gun Facilities in Spain Global view 29

30 Glass soldering Facilities in Spain 30

31 Glass washing machine Facilities in Spain 31

32 Frame chemical treatment Facilities in Spain 32

33 Chemical plant for absorber treatment Facilities in Spain 33

34 Assembly line Facilities in Spain 34

35 Assembly process Software Facilities in Spain General view 35

36 Tubes welding Bellows welding Facilities in Spain Sleeves welding 36

37 Absorbers Facilities in Spain Absorber cutting 37

38 Laser welding Facilities in Spain 38

39 Roll to roll system for Getter Facilities in Spain 39

40 Baking system prototype Facilities in Spain 40

41 Vacuum testing bench Facilities in Spain 41

42 Vacuum Facilities in Spain 42

43 Panel of 3m Facilities in Spain 43

44 Sun tracker for the homologation Facilities in Spain 44

45 Sun tracker Facilities in Spain 45

46 c/o CERN CH-1211 Genève 23 Tel Fax

47 References 1. Evacuable Flat Panel Solar Collector PCT / EP 2004 / ( ) Inventor: C. Benvenuti Applicant: CERN CH-1211 Geneva Protective device for a solar collector PCT / EP 2006 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL rue de Candolle,9 CH-1205 Geneva CERN CH-1211 Geneva 23 The flat plate evacuated solar collector 3. Solar panel collector with cooling conduits comprising thermal expansion means PCT / EP 2006 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL CERN 47

48 References 4. Device for vacuum tight soldering an evacuated flat panel solar collector PCT / EP 2006 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL CERN 5. High efficiency evacuated solar panel PCT / EP 2008 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL CERN 6. Evacuated solar panel with a non evaporable getter pump PCT / EP 2008 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL CERN The flat plate evacuated solar collector 7. Sealing mechanism for an evacuated solar panel PCT / EP 2008 / ( ) Inventor: C. Benvenuti Applicants: SRB ENERGY RESEARCH SARL CERN 48