Purdue Formula Unlocks Potential of ‘Dark Side’ of Solar Panels

(photo courtesy of Purdue University)

A pair of physicists at Purdue University have developed a thermodynamic formula designed to get the most out of a new generation of solar cell. Known as a bifacial solar cell, it is capable of collecting sunlight on both sides. Muhammad “Ashraf” Alam, a professor of electrical and computer engineering at Purdue, says the newly-created formula provides information on the maximum amount of energy that can be generated using bifacial cells if the panels are optimally designed. According to the university, the formula indicates the bifacial cells could generate on average 15% to 20% more sunlight than the monofacial cells currently used in most solar panels.

Alam says the formula can calculate the necessary data in minutes.

“Anybody wishing to install a new system…will now get a cost estimate based on this maximum ability for it to generate power. It will be significantly larger than previous ones, but the question is how much more? How should you design it? Where should you put it?” said Alam. “What we have done is calculate the level of the fundamental limits of this technology and that will drive decisions by manufacturers (and) the people who are going to install new systems.”

The formula was detailed in a paper by Alam and Ryyan Khan, now an assistant professor at East West University in Bangladesh, which was published in the Proceedings of the National Academy of Sciences. According to the authors, bifacial solar cells are expected to capture 30% of the market share for solar panels around the globe by 2030. 

Alam says having information on the precise amount of energy a solar cell can generate creates a number of benefits due to energy sources of this type being very cost sensitive.

“It is like getting instead of 3% interest, you get 6%. You will make many decisions differently if your interest rates were different. So the extra energy you get, you can think about it like an additional interest rate that you are getting and so that will become an economic driver in terms of decision making.”

Alam says not only could the formula lead to the improved design of solar panels, but also find new avenues for them to be utilized. He theorizes a vertical solar cell could be installed on top of sound barriers used on interstates that could capture sunlight throughout the entire day, whereas before a monofacial panel could only accept sunlight for half of the day.

“A very big topic in Indiana that we are working on is called agrophotovoltaic. How can you integrate solar cells with the agriculture land so that you get the benefit of both? And if you have, for example, vertical solar cells in certain rows, then what happens is the combine can just go through and it will not be impeded by the solar cell, but in the morning and afternoon, the farmer has now access to a whole huge amount of energy that they had to buy from the grid before. It opens up many options, the formula that we have. It tells you that if you do it vertical, then how much more are you going to get? If you do it in a different orientation, then how much are you going to get?”

Purdue says the formula has been thoroughly validated and is ready for companies to use as they decide how to design bifacial cells. Alam says the key goal is to get the formula to the manufacturers and industry officials to accelerate the process of making the system available.