It is internationally acknowledged that alternative energy resources are required to replace fossil fuels as soon as possible. In addition, there is an increasing global demand for energy. This predicament means that it has never been more important for scientists to find new ultra efficient ways of generating renewable energy that are also profitable for suppliers. One of the latest emerging renewable energy resources is blue energy. Blue energy production requires fresh and salt water. If blue energy plants were to be placed at all river estuaries, it has been calculated that they could generate as much as 7% of our global energy demand. There are many advantages of blue energy compared to other sustainable energy sources like solar and wind energy.– No landscape or visual restrictions– No pollution (heat, exhaust, Co2)– Its production is continuous– Potentially cheaper than sun and wind energyAll together it shows that blue energy is potentially one of the best sustainable energy resources in the world. Therefore, additional research is required to improve efficiency, sustainability and reduce costs of blue energy generation. We are a young team of scientists who plan to do exactly that!
Blue energy is the energy that is released when salt and fresh water are mixed under specific circumstances. Salt, sodium chloride (NaCl), when dissolved in water, splits into positively charged sodium and negatively charged chloride ions. These ions equally spread throughout the water, similar to dye added to water. If you add water to salt water, sodium and chloride ions will move around until they are equally spread again. This naturally occurring chemical process is the power that drives blue energy generation.To transform this form of power, known as osmotic power, into blue energy specific membranes and electrodes are required. These membranes need to be placed between three adjacent compartments, where the middle compartment is filled with salt water and the other two with fresh water. These membranes are ion-selective and can be seen as a filter. They prevents the exchange of water between both compartments, but allows the passage of sodium or chloride ions. Two types of ion-selective membranes are used: Cation Exchange Membranes (CEM) and Anion Exchange Membranes (AEM). The cation membrane is positively charged and promotes the transfer of chloride ions. The anion membrane is negatively charged and promotes the transfer of sodium ions. The result of this is that the sodium and chloride ions move from the salt water through the membranes to the fresh water. The electrodes placed in the fresh water compartment are able to convert the movement of the charged ions into blue energy via a chemical process. These electrodes either oxidize or reduce to restore the change in charge. This change results from the increase of charged ions in the fresh water compartment. The oxidation and reduction of the electrodes generate a current; a blue current. Simple!
In nature, biofilms are usually formed of several different types of micro-organisms, however in this experiment we are using biofilms that are purely made of the bacterium, Bacillus subtilis. Biofilms made of Bacillus subtilis have remarkable architectural features, made up of very sophisticated cell specialisations and cell-cell communication within their community. In order to make the biofilms even better our team will modify a Bacillus subtilis biofilm in such a way that its biofilm has more potential to generate blue energy. The modifications will induce overexpression of genes that promote rigidity of the biofilm and result in a more negatively charged biofilm that is better for creating energy. One requirement of a rigid biofilm is the presence of a carrier, on which the biofilm can grow. Ideally this carrier is biological and promotes biofilm growth without influencing the ion-selectivity of our biofilm. In order to create a biofilm that is able to grow under water we require a drip flow reactor setup. To test the ability of our membrane in generating blue energy we need an experimental setup, which would be able to test ion-selectivity, energy production of our biofilm and currently used membranes.
We hope to discover a biological membrane or biofilm that is cheaper and a more sustainable alternative to the currently used membranes that generate blue energy by the mechanism described above. A biofilm forms in the natural world when bacteria adhere to surfaces in moist environments by excreting a slimy, glue-like substances. Examples that you will be familiar with include the plaque that forms on our teeth or the slimy layer that appears on rocks.
As we are still students, our university has provided us with a laboratory and equipment. However, we also require a multitude of lab materials, chemicals and kits to conduct the experiment. This includes equipment to enable us to maintain our bacteria, genetically modify our bacteria and test our modifications. Furthermore, we need to order specific parts to create our experimental set up to test if our biofilm is able to generate blue energy.
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