Mid-infrared emissivity of crystalline silicon solar cells

Abstract

The thermal emissivity of crystalline silicon photovoltaic (PV) solar cells plays a role in determining the operating temperature of a solar cell. To elucidate the physical origin of thermal emissivity, we have made an experimental measurement of the full radiative spectrum of the crystalline silicon (c-Si) solar cell, which includes both absorption in the ultraviolet to near-infrared range and emission in the mid-infrared. Using optical modelling, we have identified the origin of radiative emissivity in both encapsulated and unencapsulated solar cells. We find that both encapsulated and unencapsulated c-Si solar cells are good radiative emitters but achieve this through different effects. The emissivity of an unencapsulated c-Si solar cell is determined to be 75% in the MIR range, and is dominated by free-carrier emission in the highly doped emitter and back surface field layers; both effects are greatly augmented through the enhanced optical outcoupling arising from the front surface texture. An encapsulated glass-covered cell has an average emissivity around 90% on the MIR, and dips to 70% at 10 µm and is dominated by the emissivity of the cover glass. These findings serve to illustrate the opportunity for optimising the emissivity of c-Si based collectors, either in conventional c-Si PV modules where high emissivity and low-temperature operation is desirable, or in hybrid PV-thermal collectors where low emissivity enables a higher thermal output to be achieved

Pathways for mitigating thermal losses in solar photovoltaics

“…Four back reflectors (MgF 2 -Ag, PERC, ITO-Ag and Al-BSF) are selected using data from 15 , extrapolated beyond 2.5 μ m up to 4 μ m (even though this range contributes less than 1% of the total AM1.5 irradiation power). The selected reflectance data for the Al-BSF back reflector are consistent with those provided in 16 . Above 4 μ m, panel emittance is dominated by that of glass 16 , hence the soda-lime glass emittance spectrum given in 12 is applied.…”

“…The selected reflectance data for the Al-BSF back reflector are consistent with those provided in 16 . Above 4 μ m, panel emittance is dominated by that of glass 16 , hence the soda-lime glass emittance spectrum given in 12 is applied. Dependence of emittance with polar angle is modelled using a weighting factor inferred from 8 for every wavelength.…”

Experimental study for thermal regulation of photovoltaic panels using saturated zeolite with water

“…A test rig was setup and calibrated in order to evaluate the thermal performance of solar panels under different arrangement of the zeolite. Solar panels were simulated using three blue coated copper plates of emissivity 90% of similar characteristics of PV panels based on experimental results [24], [25]. Only heat transmitted (Q transmitted in flow chart below, not the total solar energy input to the panel) is considered to be removed at solar radiation of 600, 800 and 1000 W/m 2 .…”

Performance of a dielectric PVT concentrator for building-façade integration

“…The absorption of the solar cell is also considered for rays reaching the target. With this regard, the model developed by Riverola et al has been utilized [16].…”