DEVELOPMENT OF A METHOD FOR MEASURING PPFD DISTRIBUTION OVER THE TECHNOLOGICAL AREA OF A GREENHOUSE BY A MOBILE INSTALLATION

A mobile installation for measuring the distribution of PPFD over the technological area of greenhouses has been implemented, and a measurement method has been developed using this installation. Mobile measurements were organized, according to the results of which, the errors in determining the average irradiance and uniformity of irradiation were established.

Influence of irradiance on the growth and biochemical composition of Nitzschia aff. pellucida

In this paper the influence of irradiance and the operation modes on biomass production and biochemical composition, especially the fatty acid profile, on the diatom Nitzschia aff. pellucida was studied. Experiments were carried out under laboratory conditions, but simulating those outdoors, at irradiances ranging from 100 to 1000 µmol photons m−2 s−1, both in batch and semi-continuous mode. The data show that the growth rate increased with irradiance, following a hyperbolic relationship with the average irradiance (Eav). However, at irradiances higher than 450 µmol photons m−2 s−1, photo-inhibition was observed, with Fv/Fm values notably decreasing at irradiances above 1000 µmol photons m−2 s−1. To take account of this phenomenon, a growth model is proposed that considers the saturation constant modification (Ek) as a function of available irradiance. The data indicate that N. aff. pellucida is better adapted to low irradiances, below 300 µmol photons m−2 s−1. Regarding the biochemical composition, the highest content of lipids (~ 20%) and carbohydrates (~ 40%) was achieved at high irradiances (≥ 450 µmol photons m−2 s−1), while the highest protein content (> 8%) was found at low irradiances (≤ 200 µmol photons m−2 s−1). Elevated amounts of saturated fatty acids (SFA) (> 60%) were measured at high irradiances, while the highest content of unsaturated fatty acids (USFA) (> 35%) was found at low irradiances. Eicosapentaenoic acid (C20:5 n-3) (EPA) and arachidonic acid (C20:4 n-6) (ARA) were only detected at 200 µmol m−2 s−1 but not at higher irradiances. The results confirm the effects of irradiance and the cultivation mode on the growth and biochemical composition of N. aff. pellucida. The model is an important tool when using this valuable strain to produce compounds of biological interest.

Experimental Study of Polyethylene Fusion by Scheffler Solar Concentrator

Aims: The present work is the use of Scheffler technology to melt plastic waste to produce composite materials using an oven type receiver. The composite material in this study contains polyethylene as a matrix and sand as reinforcement. Study Design: The fusion temperature of polyethylene is about 200°C and is obtained by solar concentration. The experimental plastic melting unit in Saaba (latitude 12.38° N; longitude -1.43° E), Burkina Faso, uses two 8 m² Scheffler concentrators sharing a cubic receiver. Three types of mirrors with a reflectivity of at least 90% are used as reflecting facets to equip the Scheffler dishes at the site. Methodology: The thermal behavior of the receiver is analyzed experimentally. Temperatures are measured on the inner and outer walls as well as the internal air temperature with 5 K-type thermocouples. When the fusion temperature is reached on the inside, we introduce the plastic waste which has been previously washed, crushed, dried and weighed. Results: The installed model obtained an average energy of 1.80 kW at the receiver and an average internal temperature of 251.15°C for an average irradiance of 623 W/m² during the no-load test. During the load test, an average energy of 1.34 kW and an internal temperature of 206.4°C were reached for an average irradiance of 473 W/m² and an optical efficiency of 56%. This test led to the production of two pavers of the composite material matrix with 2.2 kg of plastic waste. Conclusion: These results show that the profiles of the primary reflector, tracking system, and tilt axis are accurate and the maximum concentrated solar flux converges on the absorbing surfaces of the receiver. The tempered panes of the absorbing surfaces is more transparent and less emissive. Thus our device contributes to the valorization of plastic waste by using a non-polluting energy source.

The effect of different working fluids and internal geometries on the efficiency of evacuated tube heat pipe solar collectors

In this study, a heat pipe was modified with designed and manufactured inserts of specific profiles in order to investigate the effect of the internal geometries and working fluids on the efficiency of the evacuated tube heat pipe solar collector. The experimental rig was made of a mobile frame, an insulated water tank, a solar simulator and an evacuated tube heat pipe. Using an average irradiance of 700 watts per square meter, the indoor tests were conducted first on a heat pipe without any working fluid (dry mode) and later on the heat pipe containing, in turn, each of the six working fluids for each of the five geometries. Results show that, when inserting different profiles in the heat pipe, there is an enhancement of the heat transfer and hence an increase in the efficiency of the evacuated heat pipe solar collector.

FISH PRE-TREATED WITH SALT BRINE: PROCESS STUDY AND DRYING KINETICS

This work is part of a study for the conservation of fish products through solar drying. The grey seabream is dried after a pre-treatment of 16 hours in a salt brine under two conditions: on a rack in open air and in a solar dryer. The tests were carried out under average irradiance conditions of 592.76 W/m², an average ambient temperature of 30°C and an average air temperature in the dryer of 50°C. The results obtained, allowed us to reach a final humidity of 32% from an initial humidity of 65% in a wet basis. The drying was processed in 15 hours, (i.e. two days in the dryer) and 24 hours (i.e. three days in the open air). The modeling of the drying kinetics of the grey sea bream is carried out from empirical or semi-empirical models taken from the previous works. Several criteria were defined for the choice of the two-term model as being the one that can describe in the best way, the drying of the fish in both conditions. The effective diffusivity was determined using Ficks diffusive model whose solution is given by Crank, so that the logarithm of the reduced moisture allows us to find effective diffusivities for fish of 9.88823 10-7 (m²/s) and 1.72534 10-6 (m²/s) for open-air and in dryer drying respectively.

Contributions to the Surface Downwelling Longwave Irradiance during Arctic Winter at Utqiaġvik (Barrow), Alaska

Intrusions of warm, moist air into the Arctic during winter have emerged as important contributors to Arctic surface warming. Previous studies indicate that temperature, moisture, and hydrometeor enhancements during intrusions all make contributions to surface warming via emission of radiation down to the surface. Here, datasets from instrumentation at the Atmospheric Radiation Measurement User Facility in Utqiaġvik (formerly Barrow) for the six months from November through April for the six winter seasons of 2013/14–2018/19 were used to quantify the atmospheric state. These datasets subsequently served as inputs to compute surface downwelling longwave irradiances via radiative transfer computations at 1-min intervals with different combinations of constituents over the six winter seasons. The computed six winter average irradiance with all constituents included was 205.0 W m−2, close to the average measured irradiance of 206.7 W m−2, a difference of −0.8%. During this period, water vapor was the most important contributor to the irradiance. The computed average irradiance with dry gas was 71.9 W m−2. Separately adding water vapor, liquid, or ice to the dry atmosphere led to average increases of 2.4, 1.8, and 1.6 times the dry atmosphere irradiance, respectively. During the analysis period, 15 episodes of warm, moist air intrusions were identified. During the intrusions, individual contributions from elevated temperature, water vapor, liquid water, and ice water were found to be comparable to each other. These findings indicate that all properties of the atmospheric state must be known in order to quantify the radiation coming down to the Arctic surface during winter.

Compact UV LED Lamp with Low Heat Emissions for Biological Research Applications

Much biomedical research focuses on the effects of UV light on human cells. UV light sources are a prerequisite for such research. This paper presents the design and achieved performance of a UVA (Ultraviolet A: 320–400 nm) and a UVB (Ultraviolet B: 290–320 nm) LED-based lamp suitable for use in bioassays, as well as inside an incubator. Numerical simulations were used to optimise the number, layout and output power of LEDs to achieve good irradiance homogeneity while maintaining low costs. Design was optimised for the efficient transfer of generated heat away from the irradiated samples through the heatsink at the back of the lamps. The average irradiance of the target surface by the UVA lamp was 70.1 W/m2 with a maximum deviation of 4.9%, and the average irradiance by the UVB lamp was 3.1 W/m2 with a maximum deviation of 4.8%. With the UVA and UVB lamps, the temperature of samples undergoing irradiation in the incubator rises from 37 to 42 °C within 40 and 67 min, respectively. This by far exceeds the required UV irradiation time in most cases. Tests on Jurkat and HEK-293 cell cultures confirmed the suitability of our lamps for biomedical research.

Estimating Underwater Light Regime under Spatially Heterogeneous Sea Ice in the Arctic

The vertical diffuse attenuation coefficient for downward plane irradiance ( K d ) is an apparent optical property commonly used in primary production models to propagate incident solar radiation in the water column. In open water, estimating K d is relatively straightforward when a vertical profile of measurements of downward irradiance, E d , is available. In the Arctic, the ice pack is characterized by a complex mosaic composed of sea ice with snow, ridges, melt ponds, and leads. Due to the resulting spatially heterogeneous light field in the top meters of the water column, it is difficult to measure at single-point locations meaningful K d values that allow predicting average irradiance at any depth. The main objective of this work is to propose a new method to estimate average irradiance over large spatially heterogeneous area as it would be seen by drifting phytoplankton. Using both in situ data and 3D Monte Carlo numerical simulations of radiative transfer, we show that (1) the large-area average vertical profile of downward irradiance, E d ¯ ( z ) , under heterogeneous sea ice cover can be represented by a single-term exponential function and (2) the vertical attenuation coefficient for upward radiance ( K L u ), which is up to two times less influenced by a heterogeneous incident light field than K d in the vicinity of a melt pond, can be used as a proxy to estimate E d ¯ ( z ) in the water column.