Using lithium batteries for energy storage in photovoltaic systems

February 10th, 2012 by University of Southampton

A joint research project between the University of Southampton and lithium battery technology company REAPsystems has found that a new type of battery has the potential to improve the efficiency and reduce the cost of solar power.

Dr. Dennis Doerffel of REAPsystems discusses with Yue Wu and his supervisors, the lithium iron phosphate battery as an energy storage device in photovoltaic systems (click image to expand - Image courtesy of the University of Southampton)

The research project, sponsored by REAPsystems, was led by MSc Sustainable Energy Technologies student, Yue Wu and his supervisors Dr Carlos Ponce de Leon, Professor Tom Markvart and Dr John Low (currently working at the University of Southampton’s Research Institute for Industry, RIfI).

The study looked specifically into the use of lithium batteries as an energy storage device in photovoltaic systems.

Student Yue Wu said “lead acid batteries are traditionally the energy storage device used for most photovoltaic systems. However, as an energy storage device, lithium batteries, especially the LiFePO4 batteries we used, have more favourable characteristics.”

Data was collected by connecting a lithium iron phosphate battery to a photovoltaic system attached to one of the University’s buildings, using a specifically designed battery management system supplied by REAPsystems.

Dr Dennis Doerffel (left) founder of REAPsystems and MSc Sustainable Energy Technologies student, Yue Wu (click image to expand - image courtesy of University of Southampton)

Yue added “the research showed that the lithium battery has an energy efficiency of 95 % whereas the lead-acid batteries commonly used today only have around 80 %. The weight of the lithium batteries is lower and they have a longer life span than the lead-acid batteries reaching up to 1,600 charge/discharge cycles, meaning they would need to be replaced less frequently.”

Although the battery will require further testing before being put into commercial photovoltaic systems the research has shown that the LiFePO4 battery has the potential to improve the efficiency of solar power systems and help to reduce the costs of both their installation and upkeep.

Dr Carlos Ponce de Leon and Dr. John Low now plan to take this project further with a new cohort of Masters students.

Dr Dennis Doerffel, founder of REAPsystems and former researcher at the University of Southampton, said “for all kinds of energy source (renewable or non-renewable), the energy storage device – such as a battery – plays an important role in determining the energy utilisation.”

“Compared with traditional lead acid batteries, LiFePO4 batteries are more efficient, have a longer lifetime, are lighter and cost less per unit. We can see the potential of this battery being used widely in photovoltaic application, and other renewable energy systems,” he said.


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