26 June 2013 KORANET-SUPSI

Transcription

1 26 June 2013 KORANET-SUPSI

2 New dimensions in trough technology Concrete frame PVC-PES foil ETFE foil Major innovations Receiver Concrete frame Pneumatic mirror and enclosure High-temperature (> 600 C) air receiver Packed-bed thermal energy storage Mirror foil stack 2

3 Concrete frame Pre-cast fiber-reinforced concrete structure: Optimized beam with accurate shape design Metallic frame structure (steel or aluminum) Expensive in investment and maintenance Low stiffness, wind sensitive Current systems 3

4 Concrete frame Advantages Long lifetime (60 years) Increased stiffness enabling larger trough apertures Low cost per aperture area In situ manufacturing, extensive use of local workforce and resources Anti-seismic mechanism able to withstand extreme seismic events 4

5 Pneumatic mirror Mirror foils kept in shape by differential pressures, linear parabolic configuration. Highly reflective silvered polyester foil (95% reflectance). Glass or aluminum mirrors Current systems Limited aperture (6 m with multi-mirror) Limited concentration factor (30 suns average) Expensive and difficult to align Prone to dust and scratching Water consumption for washing Limited manufacturing capacity R4=6.78m R3=7.80m P5 R2=9.52m P1 R1=12,18m 5

6 Pneumatic mirror Advantages Large aperture (9.7 m with 2 mirrors) High optical efficiency High concentration (60 suns average) Simple manufacturing Low cost per aperture area No production bottlenecks 6

7 Pneumatic enclosure The mirrors and receiver are protected inside a pneumatic enclosure with a controlled atmosphere, the external film is made of highly transparent ETFE (92% transmittance on the solar spectrum) Advantages Excellent self-cleaning properties of ETFE film and greater resistance than glass against scratching No dust and low humidity inside the enclosure Easy to wash and total recovery of washing water 7

8 High-temperature air as HTF - High primary concentration (C geom = 70x geometric) - High optical efficiency (h opt = 0.87) - Split-trough design allowing for greater re-concentration High-efficiency secondary (linear trumpet) C geom = 100x h opt, sec = 0.98 High operation temperatures possible However, current HTF i) have temperature limitations (400 C with thermal oil) ii) have a complex implementation (molten salts) iii) are difficult to be used in a trough configuration (direct steam) Air as HTF Advantages No costs and environmental issues No operating temperature limit and phase change in the considered temperature range Near-ambient operating pressure Allows for the use of inexpensive TES solutions (pebble stone packed bed) Straightforward to integrate in thermal processes where heating is attained conventionally by combustion Challenges Low volumetric heat capacity large volume flows leading to significant pressure drop Low thermal conductivity large active surface area needed for convection heat transfer 8

9 Receiver design parameters A series of further design criteria are introduced: A maximal operating temperature of 650 C to avoid the use of refractory alloys like Inconel or Hastelloy (which are very expensive, ~100 EUR/kg) Use of conventional materials and no high-tech coatings or vacuum insulation, no single cost-dominating component Low thermal inertia Design challenges Pressure drop minimization Large flow cross-section Radiative heat losses minimization High concentration Small ΔT between walls and fluid Small apparent emissivity Component design that can be manufactured at low cost High-performance insulation with little mass Radiation shield insulation 9

10 Cross-flow design Fundamental limitation of linear tubular receivers: D Δp, Nu ΔT D Straight pipe: L It would be ideal to control pressure drop and temperature difference independently Branching flow up in multiple parallel tubes yields 1 additional parameter Arranging them in cross-flow configuration yields 2 additional design parameters Array of straight tubes: D N L Array of cross-flow pipes in parallel flow arrangement: D l D d N L 10

11 The air "chrysalis" Spiral tube coil cavity ( chrysalis ) q rerad,tube q cond,wall q HTF q rerad,cavity T q solar,abs q cond,win m HTF q conv q solar,refl Advantages Cylindrical cavity high apparent absorptivity Lowest temperature at cavity opening lower apparent emissivity Secondary flow in coil high h and low ΔT Low cost 11

12 Receiver design Hot air duct Multi-shield radiative insulation Microporous insulation Linear secondary concentrator (water-cooled) Spiral tube coil cavity (chrysalis) Glass Cold air duct 12

13 System models System modeled simultaneously from different perspectives: Optical design (PRE-ETHZ) Cavity model Semi-analytical model of cavity coupled with raytracing (PRE-ETHZ) CFD model (ICIMSI-SUPSI) Receiver insulation (ICIMSI-SUPSI) Entire receiver airflow modeling (ICIMSI-SUPSI) 13

14 System models Receiver airflow modeling: Achieving near uniform massflow over the collector length through the use of adjustable diaphragm valves 14

15 Collector efficiency Yearly DNI [kwh/m2] Receiver performance Collector efficiency η col = η opt η th as a function of incoming radiation skew angle from simulations. Yearly DNI as a function of the skew range for Ait Baha, Morocco is also shown (N-S orientation of collector axis.) 80% % % % % 30% Yearly DNI Collcetor eff. 20% % 50 0% Skew angle [deg] 0 15

16 On-sun recevier prototipe test DNI [W/m2] T Chrysalis 1 [ C] T Chrysalis 2 [ C] T Chrysalis 3 [ C] T Chrysalis 4 [ C] T Chrysalis 5 [ C] T Runback 1 [ C] T Runback 2 [ C] :19:12 11:31:12 12:43:12 13:55:12 15:07:12 16

17 Assembled receivers 17

18 Thank you! 18

19 19

20 Concrete elements PT TLC FS TTD+TTS TLE TTC TTT ST Component LxWxH Concrete volume Weight [m] [m 3 ] [t] TLC x 1.35 x TLE x 1.75 x TTT x 1.10 x ST 3.48 x 2.31 x PT 1.50 x 0.97 x FS 5.50 x 4.38 x TTD / TTS 2.30 x 1.73 x TTC 2.30 x 1.35 x

21 Concrete manufacturing formworks TLE LxWxH: 44 x 3 x 3.6 m Total weight: 83 t Transportation: 5 trucks + 2 low trailers ST LxWxH: 5.9 x 3 x 2.7 m Total weight: 7.8 t Transportation: 1 truck (with PT) PT (2x) LxWxH: 2.3 x 1.8 x 2.4 m Total weight: 3 t Transportation: 1 truck (with ST) TLC LxWxH: 44 x 3 x 4 m Total weight: 85 t Transportation: 5 trucks + 2 low trailers TTC LxWxH: 7.5 x 3 x 4 m Total weight: 21 t Transportation: 1 truck TTT LxWxH: 13.7 x 8.9 x 15.3 m Total weight: 80 t Transportation: 5 trucks TTD + TTS LxWxH: 3.8 x 3 x 3.6 m Total weight: 10 t Transportation: 1 truck 21

22 Concrete components manufacturing 22

23 Concrete components assembly 23

24 Mirrors and ETFE enclosure 24

25 Glossary CAPEX: Capital expenditures. All the costs arising from the plant construction and commissioning. CPV: Concentrator PhotoVoltaic systems. Photovoltaic systems where the photovoltaic cells work with solar radiation concentrated many times by lenses and/or reflectors. CSP: Concentrated Solar Power. High temperature solar systems which attain these temperatures by working with solar radiation concentrated several times by reflectors and/or lenses. Debt: Part of the project financing which is provided by a third party, e.g. a bank loan. It requires periodic and pre-determined payment of interest rates and reimbursements. DNI: Direct Normal Irradiance. Also called beam irradiance, DNI is the fraction of the solar irradiation which comes directly from the solar disk (without scattering or absorption in the atmosphere) as seen by a plane always facing it. Equity: Part of the project financing which is exchanged for ownership of the plant, e.g. in the form of shares. Although a return on the investment is expected, it is not required that it is paid out systematically. ETFE: Ethylene tetrafluorothylene. A UV-transparent fluorine-based polymer. Heat transfer fluid / thermal fluid: Fluid (liquid or gaseous) which is used to transfer the thermal energy from its source to the user. LCOE: Levelized Cost Of Energy. A standard economic valuation method used to compare the cost of energy coming from different sources. It is based on the actualization approach, where future energy returns and plant costs are discounted at the cost of capital (i.e. the combined rate from the interest on debt and the expected return on equity). O&M: Operation and Maintenance. OPEX: Operational expenditures. All the costs generated during the plant operation. PVC-PES: PolyVinyl Chloride - PolyEtherSulfone. PVC-coated polyester fabric. Thermal energy storage: System that allows to store the thermal energy for later use in a similar fashion of what a battery does with electricity. Trough collector: Collector which focuses the solar radiation in one or more lines by means of linear parabolic mirrors. 25

26 Current CSP technologies parabolic trough linear fresnel stirling dish solar tower CENTRAL RECEIVER REFLECTOR ABSORBER TUBE SOLAR FIELD PIPING CURVED MIRRORS CURVED MIRRORS RECIEVER/ENGINE REFLECTOR HELIOSTATS ABSORBER TUBE AND RECONCENTRATOR 26

27 Anti-seismic mechanism Hanging rod sustain structure Collector tracking mechanism Collector wheels Hanging rod spherical joint Foundation Hanged collector base Dampers Hanging rod 27

28 AIRLIGHT ENERGY Holding - Biasca - Switzerland