Biological photovoltaics, biophotovoltaics, or BPV, is a renewable energy technology that uses oxygenic photoautotrophic organisms (or parts) to generate electricity from solar power. These systems generate electrons through the photolysis of water, which are then transferred to an anode. A high-potential reaction occurs at the cathode, and the potential difference between the anode and cathode creates a current through an external circuit.
While still in its early stages, the field has seen notable advancements, particularly in genetic engineering, hybrid material integration, and early commercialization efforts.
Image Credit: petrmalinak/Shutterstock.com
Types of BPVs
BPV systems are categorized by their light-harvesting material and the mode of electron transfer between biological material and anode.1
Simple and complex materials
Simple and complex materials are both under consideration. The advantage of simple materials is that they tend to be more efficient than complex materials, but the trade-off is that they are generally less robust.1
Isolated photosystems
Isolated photosystems are the simplest available, offering a direct connection between anode reduction and water photolysis. These systems are typically isolated and absorbed to a conductive surface. However, these tend to have short lifetimes (just a few hours) and requirements for low temperatures to improve stability.1
Sub-cellular fractions
Slightly more complex are sub-cellular fractions. These devices use fractions of photosynthetic organisms such as purified thylakoid membranes.1
Some BPV systems, such as cyanobacteria, have been developed to take advantage of entire biological organisms. The system grows cyanobacteria in suspension with an anode made from indium tin oxide.1
These are the most robust type of BPV system, with lifetimes spanning months so far observed in the literature. The whole cells’ insulating outer membranes reduce electron transfer, resulting in devices with poorer energy conversion efficiency.1
Recent Developments in Biophotovoltaics Systems
The working principle behind BPVs has only recently been introduced in research settings. The use of natural photosynthesis for direct energy production has only been seriously put forward in the last few decades. While there is considerable promise for the technology, there are still several gaps in knowledge before it can come to fruition (or be found to be unworkable).1
Recent research has focused on overcoming the traditionally low current outputs of BPV systems by genetically modifying photosynthetic microbes for better electron export. For example, scientists achieved an order-of-magnitude increase in photocurrent from Synechocystis sp. PCC 6803 by removing its outer membrane barrier. This outer membrane deprivation dramatically enhanced extracellular electron transfer (EET), allowing ~10× higher current than the wild type.2
Researchers are also re-routing internal electron flow to favor electricity generation. A recent study published in ChemCatChem suggests “plugging” metabolic electron leaks so that fewer electrons are consumed by competing pathways like oxygen reduction or CO2 fixation. By hypothetically eliminating certain sinks such as diverting electrons away from respiration and excess carbon fixation, up to 90% of the electrons could be made available for harvesting. This multidisciplinary strategy points to the potential of metabolic and genetic tweaks to maximize electron delivery to the electrode.3
Innovative Materials and Electron Transfer Enhancements
Alongside biological improvements, new materials have been adopted to facilitate electron transfer in BPVs. Researchers are exploring conductive nanomaterials and porous electrodes to provide better contact between cells and anodes.
Graphene-based anodes
A recent study in Sustainable Energy and Fuels introduced sustainable graphene-based anodes for BPVs using few-layer graphene and graphene–cellulose nanocrystal (CNC) composite films. These films are produced via a green process and are naturally rough and hydrophilic, which helps cyanobacteria adhere. When tested with Synechocystis cells, the graphene-CNC electrodes showed stable electrochemical performance.4
Direct electron transfer
Other studies emphasize moving beyond soluble mediators like ferricyanide toward direct electron transfer. For instance, integrating microscopic nanoparticles inside cells or on electrodes can create electrical “bridges.” Some teams have induced cyanobacteria to biosynthesize metal nanoparticles in situ to enhance conductivity, though controlling particle size and placement remains a challenge.5
3D structured anodes
There is also interest in 3D structured anodes like foams or meshes to increase surface area for cell attachment. The caveat is that thicker electrodes can block light, so researchers are investigating transparent or light-permeable conductive materials (like nanostructured carbon or conductive polymers) to support dense biofilms without sacrificing illumination. Such material innovations are gradually improving the electron transfer efficiency and output of BPV devices.5
Prototypes and Real-World Demonstrations
In recent years, BPVs have progressed from laboratory curiosities to practical demonstrations. In 2022, a University of Cambridge team unveiled a palm-sized BPV device containing Synechocystis algae on an aluminum anode that continuously powered an Arm Cortex M0+ microprocessor for over six months using only ambient light and water. This algae-powered chip (comparable in size to an AA battery) ran reliably under natural day-night light cycles and fluctuating room temperatures, showcasing a level of stability and longevity promising for the Internet of Things (IoT).6
The Commercialization of Biological Photovoltaics
The recent advances have spurred the first steps toward commercialization of BPV technologies. One notable example is Electric Algae, a startup founded in 2023 as a spin-off from Technion – Israel Institute of Technology research. The company is developing a macroalgae-based bioelectric system that uses photosynthetic seaweeds to produce continuous electricity.7
According to Electric Algae, its seaweed-based cells generate current in sunlight and darkness (using stored energy at night), an advantage over conventional solar panels that go idle at night. This approach is envisioned as part of a circular economy solution, simultaneously yielding electrical power, biomass for food, and water purification as the algae grow.7
In Mexico, startup Greenfluidics is integrating microalgae into “biopanel” building façades. These biopanels use algae to capture CO2 and sunlight, producing oxygen and biomass, while a built-in nanotech-enhanced system harvests thermal energy for electricity via thermoelectric generators. Greenfluidics claims each panel could generate a few hundred kWh per square meter yearly under ideal conditions, though real-world results remain to be seen.8
Challenges and Future Directions of Biophotovoltaics
BPVs have improved in terms of efficiency and durability, but their performance remains modest, with efficiencies of around 0.5%. This is significantly lower than traditional silicon photovoltaic systems, which achieve efficiencies between 15% and 20%. While there have been advancements in long-term stability, polymer-encapsulated cyanobacteria trials reveal a lifespan of just six months despite exceeding previous records.1,5
Scalability is another significant challenge, as most BPV systems are currently limited to less than 1 square meter. There is a pressing need for low-cost materials and automated cultivation methods to achieve larger-scale implementation.1,5
On a more positive note, recent lifecycle analyses indicate that BPV could sequester 0.3 to 0.5 kilograms of carbon dioxide per kilowatt-hour. However, industrial-scale validation is needed to verify these results.1,5
Conclusion
BPVs have progressed significantly from theoretical concepts to real-world demonstrations, with advancements in synthetic biology, nanomaterials, and commercialization efforts.
While challenges remain in efficiency and scalability, ongoing innovations suggest a future where BPVs could complement traditional solar energy. As research continues, their potential for sustainable, self-repairing, and carbon-negative energy solutions grows increasingly promising.
References and Further Reading
- Tschörtner, J., Lai, B., & Krömer, J. O. (2019). Biophotovoltaics: Green Power Generation From Sunlight and Water. Frontiers in Microbiology, 10, 444354. DOI:10.3389/fmicb.2019.00866. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00866/full
- Kusama, S. et al. (2022). Order-of-magnitude enhancement in photocurrent generation of synechocystis sp. PCC 6803 by outer membrane deprivation. Nat. Commun. 13 (1), 1–12. DOI:10.1038/s41467-022-30764-z. https://www.nature.com/articles/s41467-022-30764-z
- Reilly-Schott, Vincent. et al. (2024). Electron Leaks in Biophotovoltaics: A Multi‐Disciplinary Perspective. ChemCatChem. DOI:10.1002/cctc.202400639. https://chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/cctc.202400639
- Lund, S. H. et al. (2024). Graphene and graphene-cellulose nanocrystals composite films for sustainable anodes in biophotovoltaic devices. Sustainable Energy & Fuels. DOI:10.1039/d3se01185b. https://pubs.rsc.org/en/content/articlelanding/2024/se/d3se01185b
- Cai, T., & Song, M. (2023). Life in biophotovoltaics systems. Frontiers in Plant Science, 14, 1151131. DOI:10.3389/fpls.2023.1151131. https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2023.1151131/full
- Renewable Bio-Photovoltaic Cell Created. (2022). Sci.News: Breaking Science News. https://www.sci.news/othersciences/materials/renewable-bio-photovoltaic-cell-10802.html
- Electric Algae. (2024). Israeli National Centre of Blue Economy. https://blueconomy-il.com/startups/electric-algae/
- Algae biopanel windows make power, oxygen and biomass, and suck up CO2. (2022). New Atlas. https://newatlas.com/energy/greenfluidics-algae-biopanels
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.