International School on Concentrated Photovoltaics Ferrara 2 6

International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006 “CHARACTERIZATION OF CONCENTRATED LIGHT BEAMS WITH APPLICATIONS TO SOLAR CONCENTRATORS” Part B: “Radiometric methods” Antonio Parretta ENEA – Bologna

OUTLINE 1. 2. The Double Cavity Radiometer: i) Theory ii) Practical realization iii) Calibration iv) Applications Introduction to radiometers for solar concentrators with cylindrical receivers Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DOUBLE-CAVITY RADIOMETER (DCR)(1) The optical model (1)Patented Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Radiometer with two coupled integrating spheres P 0 sphere 1 photodetector m in to voltmeter or lock-in sphere 2 Pm Pin c i Pi Pc(r) G 1 Pc(l) j G 2 Pj Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model Energy conservation law applied to sphere 1: Energy conservation law applied to sphere 2: Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model Irradiance into sphere 1: Irradiance into sphere 2: Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model Power at input “in”: Irradiance incident on the photodetector “m”: Radiant power on the photodetector “m”: Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model We define the following Attenuation Factors: i) ii) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model iii) iv) Attenuation factor for the irradiance (flux density measurements) Attenuation factor for the power (power measurements) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model Attenuation Factors: i) iii) iv) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Modelling of a prototype of DCR sp cl of win wof is 1 is 2 wc wm pr m rad 1 We model the radiometer for measurements of the total power incident on the concentration cell Sun. Power HECO 252, used as photovoltaic receiver in the concentrating system Pho. CUS operating at ENEA Research Centre of Portici.

C-Module of the Pho. CUS Project C-Module Assembled Sun. Power HECO 252 cell Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Modelling of SP cell and optical fibre SP-HECO 252 cell SS frame Glass window DCR window Optical fibre SP-HECO 252 cell Absorber Surface area (mm 2) Emissivity [7] Reflectance (%) SP cell: Central region Sm 1 = 156 _ Rm 1 = 4 SP cell: Copper frame Sm 2 = 69 Copper scraped 0. 64 Rm 2 = 36 Optical fibre: Glass window Sof 1 = 7. 1 _ Rof 1 = 4 Optical fibre: SS frame Sof 2 = 12. 5 Stainless steel Sheet polished 0. 07 Rof 2 = 93 Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

The optical model (prototype) P 0 Sin Sm Pin G 1 Sc Pc(r) Pm G 2 Pc(l) Sphere diameter, d = 5 cm; input window area, Sin = 1. 1 × 1. 1 = 1. 21 cm 2; photodetector window area, Sm = 1. 5 × 1. 5 = 2. 25 cm 2; optical fiber head area, Sof = 0. 196 cm 2. Sof Variable quantities: aperture area, Sc = 0. 1÷ 2. 0 cm 2; wall reflectance, Rw = 92÷ 99%. Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006 Pof

The optical model (prototype) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Attenuation factor for power Attenuation factor of the DCR radiometer, calculated as function of the intermediate aperture area, Sc, for some values of the wall reflectance, Rw.

DOUBLE-CAVITY RADIOMETER (DCR) Ray tracing Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Ray tracing (prototype) Ray tracing by Trace. Pro Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DOUBLE-CAVITY RADIOMETER (DCR) The thermal model Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Thermal model Heat generated on the Sun. Power cell: where: Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Efficiency of SP-HECO 252 cell Efficiency versus concentration Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Efficiency of SP-HECO 252 cell versus concentrationat at input of DCR Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Generated Heat generated on the SP-HECO 252 cell of DCR vs. light concentration (medium) at input, for different Sco values. Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

Generated Heat generated on the SP-HECO 252 cell of DCR vs. light concentration (high) at input, for different Sco values. The curves are truncated at Gm = 200 suns. Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DOUBLE-CAVITY RADIOMETER (DCR) Manufacturing of the prototype (1) Patented Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006 (1)

Schematic 2 of the DCR gauge head 1 (t) (w 1) (w 4) (si 1) z (b 1) y (si 2) (fco) Vertical section x (fco) (w 3) 1 (si 1) (b 3) (si 2) 3 y (b 2) Horizontal section x z 2 (w 2) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

General scheme of DCR fc (pa) (Pe) (rd) (fo) Spectrometer (tr) (rd) (v) (ins) (rd) (ra) Control Module T (°C) P (risc. ) Touchscreen Isc Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DCR-1 Radiometer Output to the optical fibre Input of light ECO-VIDE (Roma) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DCR-1 Radiometer slit Sun. Power cell ECO-VIDE (Roma) Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DCR-1 Radiometer Input of light insert Window for SP cell inserts Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DCR-1 Radiometer Input of light auxiliary window insert Window for SP cell inserts Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006

DCR-1 Radiometer baffle 1 baffle 3 baffle 2 Ist International School on Concentrated Photovoltaics, Ferrara 2 -6 September 2006