LPI-Solar. CPV (Concentration Photovoltaics)

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2 CPV (Concentration Photovoltaics)

3 sunlight sunlight Area A FPPV CPV FP electricity Area A FP=Flat panel (Silicon) CPV=Concentration Photovoltaics Solar cell area A/C g CPV electricity Concentration factor C g

4 Generation of electricity: potential cost ($/KWh) reduction Fewer cells (A/C g ) More efficient cells (38% vs. 22%) Challenges The increased system complexity 1 can compromise the potential cost reduction 1 Efficient optics, heat sinks, two-axis sun-tracking, alignment, installation

5 cost cells cost + other costs energy = solar radiation efficiency Optical efficiency x cell efficiency High-efficiency concentration cells can be up to 500 times more expensive than 1-sun cells (per unit area). Cell area must be strongly decreased (C) Optics, tracker, heat sinks Only direct radiation (90-65%) is usable

6 Trade-off off: : CAP = concentration C g X acceptance angle α Large C g - low α Low C g - large α 2α 2α 2α 2α accepted rays accepted rays CPV CPV Solar cell Solar cell

7 Trade Trade- of: concentration C g - acceptance angle α Large C g - low α Low C g - large α sun low α Difficult aiming Easier aiming (and more!!) large α 7

8 CPV (Concentration Photovoltaics)

9 Increased need for renewable energy sources Global warming: increased funds from governments Increase demand of oil and resulting oil prices Rising economies: China and India will keep oil prices high Silicon solar cells not keeping up with demand Flat panel solar uses more (costly) commodities Short Shorṯ- term goals: availability (there is a bubble of interest!) Long Long- term goals: CPV to demonstrate its cosṯ- cost competitiveness with non- renewable sources

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11 High Concentration PV companies Company Country Type of cell Cell efficiency Type of optics Concentration ratio Aiming tolerance USA MJ 35% XR (SMS) 1000x ±1.9º Spain Silicon 26% Fresnel + SOE 400x ±0.5º Spain MJ 32% TIR-R (SMS) 1200x ±1.2º Japan MJ 32% Fresnel + SOE 400x ±0.4º Germany MJ 30% Fresnel 400x ±0.4º Spain MJ 32% Fresnel + SOE 400x ±0.8º USA MJ 35% 2 mirrors 500x ±1.0º Spain MJ 35% Fresnel + SOE 400x ±0.8º USA MJ 35% Taiwan MJ 35% Fresnel + SOE Fresnel + SOE 400x ±0.8º 400x ±0.8º Japan MJ 32% Curved-Fresnel 400x ±0.7º Australia Silicon 26% Parabolic mirror 400x ±1.0º US Silicon 26% Fresnel + SOE 400x ±0.5º

12 CPV companies: lack of acceptance syndrome Optics requires high accuracy. Assembling is expensive because fine adjustments become compulsory. Efficiency decreases significantly from single unit to an array. Optical mismatch. Efficiency increases significantly when the cells are bigger.

13 42.8% DARPA Very High Efficiency Solar Cell (VHESC) program Boeing-Spectrolab monolithic MJ cells from ~30% to 40% during the last decade

14 CPV (Concentration Photovoltaics)

15 Desired CPV system attributes High optical efficiency 1. limited number of optical elements High concentration 2. decreasing cell cost Long term durability 3. is energy, not power High acceptance angle 4. relaxes optical, mechanical requirements Irradiance uniformity 5. cell efficiency and durability Low cost 6. mass producible components Compactness 7. transportation costs

16 Why large acceptance angle? Conventional CPV system C g =1000x, α=±0.6º SMS device C g =1000x, α=±1.75º sun Difficult aiming High accuracy-high cost Easier aiming Low accuracy-lower cost

17 Why large acceptance angle? Decreases structure stiffness Relaxes optics accuracy (low cost) Simplifies assembly Easier array installation Reduced maintenance Potential for higher concentration Reduced mismatch losses Cost-effective + large-scale implementation! System Efficiency!!!

18 With LPI SMS Present Fresnel lens-based systems Half-acceptance angle α (degs) concentration factor New cells: efficiency & cost Circular aperture Square aperture Present parabolic dish-based systems

19 With LPI Patented record-breaking technologies SMS devices achieve the largest α for a given C g Sorties into cost-cutting strategies: same manufacturing/installation processes as conventional devices but less tight (easier tolerances) 20 years experience Design, Optics manufacturing, Materials, Processes, Supporting/tracking structures, Sealing, Protection, thermal management