Bypass Diodes come of age
The development of thin-film flexible solar modules including Copper Indium Gallium Selenide solar cells (CIGS), has been a major benefit to the BIPV market. The technology has not only provided designers with the opportunity to expand traditional architecture and transform buildings into aesthetically pleasing, energy-producing structures, it has demonstrated the capacity to achieve impressive year on year improvements in efficiency.
In the past, leaders in the BIPV field were only able to muster performance efficiencies in the range of around 8%. This meant that to achieve efficiencies on par with traditional silicon solar panel technology, you needed two to three times as many solar panels to achieve the same power output – not only did the economics not work, it meant you needed more roof space to house the technology. Today, many leading BIPV CIGS products, such as BIPVco’s Metektron and Flextron range, are achieving efficiencies in the range of 16-17%, which is helping to transform the economics of BIPV from a niche to a mainstream technology.
Manufacturers creating thin-film flexible solar module technology have been working hard to introduce efficiencies into the production process. For example, new proprietary tools have been introduced by some companies, allowing all the layers of the PV film to be deposited in one go.
At BIPVco, we build our modules with Bypass Diodes embedded within the cell area of the module rather than within the junction box as with silicon crystalline modules. This helps to reduce the negative effect of shaded cells in other parts of the module and improve overall system performance and efficiency. Shaded cells dissipate power as heat and cause “hot spots,” dragging down the overall IV curve of the group of cells. Bypass Diodes get round this problem by allowing current to pass around shaded cells and thereby reducing the voltage losses through the module. We have introduced a module with 28 diodes, which means 56 cells are protected by diodes every 2 cells – the standard approach is just three diodes per module (1 diode per 20 cells).
As efficiencies continue to rise, conversely we are seeing the cost of production fall, which means BIPV is cheaper than it has ever been. The economies of scale, brought about by the emergence of new manufacturers and the ‘industrialisation’ of the supply chain, has had the effect of increasing competition and reducing costs within a once niche market. Over time, this is helping drive down the price of BIPV technology. Something we at BIPVco are very excited about.