This data logger is specific to the need I have with a photobioreactor culturing microalgae. Culturing microalgae needs several key parameters in which the temperature is for thermo control and biological status, pH is for CO2 supply and control, and Dissolved Oxygen (DO) is for photosynthesis activity. This data logger can be used for other biological systems such as with aerating or pH static control.
are microscopic algae, found in fresh water and marine environments. Their size ranges from a few micrometers to a few hundred micrometers. Their function to the Earth system is similar to the plants that is, to convert solar energy to reduce carbon dioxide to organic carbon. This is vital to the Earth. Converting photon energy to chemical-bond energy is the first step to keep the solar energy in Earth. The oldest form of microalgae dated back 3-4 billion years ago. Together, the microalgae produce a half of the atmospheric oxygen (according to Wikipedia.)
One disadvantage of microalgae in compare with solar photovoltaic is a much lower efficiency in converting solar energy to equivalent energy either in term of chemical bond or in electron potential. Comparing efficiency in energy context favors the photovoltaic to electricity conversion. The argument for microalage is a neutral-carbon process or zero generation of new carbon dioxide in contrast to fossil fuels. The carbon atoms acted as electron carriers collecting electron during photosynthesis and releasing those to oxygen during combustion. Meanwhile, burning fossil fuels releases carbon dioxide to the atmosphere and thickens a layer of greenhouse gases. The microalgae biomass after harvest is extracted for liquid fuel to displace some percentage of fossil fuels. The value of microalgae is the type of compounds they produced and not merely by the energy they harvested.Source: https://www.cosia.ca/initiatives/greenhouse-gases/projects/algae-project
Microalgae needs CO2 as the building block or the material to dump electrons spitted from water. Before the photosysnthesis happens, the oxidation potential of carbon in carbon dioxide is plus 4 (+4), which means the carbon atoms are stripped away the electrons. Carbon dioxide is a stable gas because both carbon and oxygen atoms are at their lower energy status.
Photosynthesis happens in two main stages:
After one round of photosynthesis, CO2 molecules are consumed which leads to a tiny increment of the pH. If the reaction happens for a long time, most bio-available forms of inorganic carbons are exhausted and slows down the reaction rate. Now, I need to build a system to automatically replenishing CO2 just enough; otherwise, the pH is too low for the microalgae that effects functional groups on the cell's membrane. Balancing the CO2 can be done by installing an in-situ pH probe and reading the pH value to turn on/turn of a solenoid valve. When the solenoid valve is open, the CO2 is injected and dissolved in the microalgae culture and that reduces the pH of water. In the mean time, energy light from LEDs or from the Sun heats up the reactor. For research and improvement, retrieving the data DO, pH, and temperature with a high resolution (minute scale) would help to reconstruct what has happened. For the photosynnthesis of microalgae, replacing the plant in the reaction below for microalage, and submerse the reaction into water. That is what happening in the microalgae culture.
Stuff You Should Know podcast, one of my favorite recently made one for microalgae, take a listen: Algae: Food, Fuel, What?
As of September 2018, the Atlas-Scientific has updated the design of the insulator. The pH/DO breakout can be plugged on top the insulator. The USB port is convenient for a advance setup such as with Raspberry Pi.
In addition, the isolation of water is much less in air. The voltage insulator is not cheap, but it worth to invest and reduces the headache later.
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