Cambridge University researchers have developed new algae-powered fuel cells that are five times more efficient than existing plant and algal models.
With the threat of climate change always eminent, there has been a growing need for cleaner, renewable alternatives to fossil fuels. And this brings us to biophotovoltaics (BPVs).
Biophotovoltaics are slowly emerging as an environmentally-friendly and low-cost approach to harvesting solar energy and converting it into electrical current. These solar cells utilize the photosynthetic properties of microorganisms such as algae to convert light into electric current that can be used to provide electricity.
Algae produces electrons during photosynthesis, some of which are exported outside the cell where they can provide electric current to power devices.
To date, all the BPVs demonstrated have located charging (light harvesting and electron generation) and power delivery (transfer to the electrical circuit) in a single compartment; the electrons generate current as soon as they have been secreted.
Now Cambridge has devised a new technique to create a two-chamber BPV system where the two core processes involved in the operation of a solar cell – generation of electrons and their conversion to power – are separated.
Building a two-chamber system allowed the researchers to design the two units independently and through this optimise the performance of the processes simultaneously.
As Professor Tuomas Knowles explains, the key here is miniaturization: “At miniature scales, fluids behave very differently, enabling us to design cells that are more efficient, with lower internal resistance and decreased electrical losses.”
The team used algae that had been genetically modified to carry mutations that enable the cells to minimize the amount of electric charge dissipated non-productively during photosynthesis. Together with the new design, this enabled the researchers to build a biophotovoltaic cell with a power density of 0.5 W/m2, five times that of their previous design.
While this is still only around a tenth of the power density provided by conventional solar fuel cells, these new BPVs have several attractive features, they say. For instance, algae-based systems require less energy investment and can be produced in a decentralized fashion
Separating the energy generation and storage components has other advantages, too, say the researchers. The charge can be stored, rather than having to be used immediately – meaning that the charge could be generated during daylight and then used at night-time.
Image, video and content: University of Cambridge