Tag Archives: Wake Forest University

Fiber cells, light pipes — Are they the future of organic PV?

Appearing today, a story I wrote for MIT Technology Review outlines work done at Wake Forest University in North Carolina. Researchers there, led by Prof. David Carroll, have developed a way to make low-cost organic solar cells that have more than double the efficiency of existing organic devices. The idea is to stamp evenly spaced but densely populated polymer fibres onto a substrate. The optical fibres, which protrude from the surface and function like “light pipes”, let sunlight enter from the tip. The sunlight gets trapped and bounces around inside the fibre until it is absorbed by the organic solar cell wrapped around it through a dip-coating process. Carroll has tested the design and found that it improves efficiency by 1.5 times compared to a flat cell design of similar chemistry. But more than that, the sunlight can enter the tips of the fibres at any angle, meaning it can accept sunlight from sunrise to sunset. This contrasts with flat or “planar” cells that must face the sun somewhat directly. Both of these features more than double efficiency.

It’s a fascinating example — and one of hundreds out there — of how innovation is driving real progress in the solar market.

Could solar represent one quarter of world electricity production by 2050?

The International Energy Agency, according to two recently released technology roadmaps, thinks solar electricity coming from photovoltaic or concentrating solar systems could by 2050 come to represent between 20 and 25 per cent of global electricity production. Now, to be clear, we’re talking about production — not capacity — so this is a significant figure given the sun doesn’t shine all the time. PV would be mostly for distributed on-grid generation, while concentrating solar power (CSP) would be mostly used at utility scale in a way where electricity could be dispatched, much like coal power plants are used today. CSP would have a thermal storage component, and it would be done on a large scale in regions with the best solar regimes. The electricity would then rely on enhanced transmission infrastructure to get the power to more remote locations. “Together, PV and CSP could generate 9,000 terawatt-hours of power in 2050.”

It also predicts that residential and commercial building PV will reach grid parity in some markets by 2020, and will be competitive at utility scale in some regions by 2030, when it would provide 5 per cent of global electricity. “As PV matures into a mainstream technology, grid integration and management and energy storage become key issues… By 2050, PV could provide more than 11 per cent of global electricity.”

The rest will come from CSP, which is expected to become competitive as a peaking and mid-peak power source by 2020 in sunny regions. “Thanks to thermal storage, CSP can produce electricity around the clock and will become competitive with base load power by 2025 to 2030.” It also predicts North America — i.e. the southern parts of the United States — will be the largest producer of CSP electricity, followed by North Africa and India. CSP, like PV, could represent 11 per cent or more of electricity production by 2050.

Personally, I’m equally optimistic. As Joe Romm over at Climate Progress regularly makes clear, CSP is well on its way to replace coal-fired power in many parts of the world. On the PV side, I’m encouraged by the state of innovation (see above posting).