• This project is pointless and finished

    Domen07/17/2016 at 09:50 0 comments

    I have found out by just looking at the specifications of solar irradiation that any sort of artificial light that would mimic the sun would use up a lot of energy per m^2 which is simply not worth it since growing under the sun is cheap and easy.

    The current growing LED modules you can find on Ebay that are rated 150W - 300W would probably be sufficient for any type of growing so there is no need for a development of such a solution I previously proposed.

    I also can not see the point of skyscrapers growing food, where they use artificial lightning. They should rather build greenhouses I think. I'm open to any criticism.

    EDIT: Maybe it is efficient because they use so few of the LEDs? I am not sure.

  • Daily and monthly fluctuations of solar irradiance

    Domen07/17/2016 at 09:28 0 comments

    In the summer, solar radiation (measured by irradiance) will be greatest over the equator and the hemisphere tilted toward the sun.

    The further a city is from the equator, the more the solar radiation received will fluctuate throughout the year.

    Source: http://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/

  • Solar Irradiance across the world

    Domen07/17/2016 at 08:58 0 comments

    Annual surface solar irradiance received in 2008. The equator receives solar radiation at a higher intensity (irradiance) than the norther and southern hemispheres. Data compiled by P. Wang, P. Stammes, R. van der A, G. Pinardi, M. van Roozendael (2008), FRESCO+

    Solar irradiance is the intensity with which radiation enters Earth’s atmosphere. An relatable way to think about solar irradiance is by looking at the difference between a 20-watt light bulb and a 100-watt light bulb. Both produce visible light in the same wavelengths, but the brightness and intensity are very different. The 100-watt bulb has a higher intensity, or irradiance. Solar irradiance is the amount of radiant flux on an area, and is measured in watts per meter squared (W/m²)9.

    Source of the quote and the picture: http://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/

  • Sun vs. shade plants

    Domen07/17/2016 at 08:53 0 comments

    Most plants reflect green wavelengths while absorbing the rest of the visible light spectrum. In addition, shade plants respond to lower levels of PAR while sun plants harvest PAR more efficiently at higher light levels 7. In other words, as solar irradiance (intensity) increases, sun plants experience higher rates of photosynthesis. The leaves of sun plants are small and thick, with special cells allowing for these higher rates 20. Shade plants conduct photosynthesis at a lower radiation intensity level. Their leaves are thinner, longer and contain fewer chlorophyll cells.

    Source: http://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/

  • Amount of energy received (482 W/m^2 in 400 - 800nm)

    Domen07/17/2016 at 08:45 0 comments

    All quotes are from wikipedia: https://www.wikiwand.com/en/Sunlight

    Sunlight takes about 8.3 minutes to reach Earth from the surface of the Sun
    The total amount of energy received at ground level from the Sun at the zenith depends on the distance to the Sun and thus on the time of year. It is about 3.3% higher than average in January and 3.3% lower in July (see below).
    If the extraterrestrial solar radiation is 1367 watts per square meter (the value when the Earth–Sun distance is 1 astronomical unit), then the direct sunlight at Earth's surface when the Sun is at the zenith is about 1050 W/m2, but the total amount (direct and indirect from the atmosphere) hitting the ground is around 1120 W/m2.[3]

    In terms of energy, sunlight at Earth's surface is around 52 to 55 percent infrared (above 700 nm), 42 to 43 percent visible (400 to 700 nm), and 3 to 5 percent ultraviolet (below 400 nm)

    So the visible light energy that is hitting the Earth is ~482W/m^2 (1120*0.43).

    Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux. This is higher than the efficacy (of source) of most artificial lighting (including fluorescent), which means using sunlight for illumination heats up a room less than using most forms of artificial lighting.

    Maybe I should also build a device to measure the photosynthesis of the plant.

    Photosynthesis measurement systems are not designed to directly measure the amount of light absorbed by the leaf. But analysis of chlorophyll-fluorescence, P700- and P515-absorbance and gas exchange measurements reveal detailed information about e.g. the photosystems, quantum efficiency and the CO2 assimilation rates. With some instruments even wavelength-dependency of the photosynthetic efficiency can be analyzed.[36]

    Source: https://www.wikiwand.com/en/Photosynthesis

  • Photosynthesis irradiance curve

    Domen07/16/2016 at 19:49 0 comments

    The PI (photosynthesis-irradiance) curve is a graphical representation of the empirical relationship between solar irradiance and photosynthesis. A derivation of the Michaelis–Menten curve, it shows the generally positive correlation between light intensity and photosynthetic rate. Plotted along the x-axis is the independent variable, light intensity (irradiance), while the y-axis is reserved for the dependent variable, photosynthetic rate.

    Source for above quote and pictures below: https://www.wikiwand.com/en/PI_curve

    Above about 10,000 lux or ~100 watts/square meter the rate no longer increases. Thus, most plants can only utilize ~10% of full mid-day sunlight intensity.[6]

    Source: https://www.wikiwand.com/en/Photosynthetic_efficiency

    An irradiance between 400 and 800 µE m^-2 s^-1 seems to be the best option since 1000 µE.. would reqiure far more energy.

    I should probably build two different modules. One 400 µE... and one 800 µE... .