Nanotechnology challenges the solar debate

Nanotechnology could alter the solar power landscape. Electricity produced from solar cells reduces air pollutants and greenhouse gases compared with conventional fossil fuel technologies yet there are still arguments against PVs. For example, it is more expensive to produce power from solar energy than traditional fossil fuels and it is not a level playing field globally, as the Chinese government heavily subsidies solar cell production. Solar thermal energy systems are also more expensive per unit of energy generated; although it is cheaper over time because it lacks feedstocks (the raw material to supply or run a process).

Pros and cons

There are several different types of PV. About 90% of PV solar panels worldwide are based on some variation of silicon, which takes many forms depending on the element’s purity. This is classified according to how perfectly aligned the silicon molecules are and determines how well the cell is at converting solar energy. This is also known as the photoelectric effect.

Solar cells made of monocrystalline silicon (mono-Si) contain cylindrical silicon ingots. They have the highest efficiency rates, typically 15 to 20%, because they are made of the highest-grade silicon. Yet, they are also the most expensive and the circuit will break down if it is even partly covered by dirt or shade.

Polysilicon (p-Si), or polycrystalline silicon, cells are cheaper to produce than their mono-Si counterparts, with a slightly lower heat tolerance. They do have some disadvantages, however, including an efficiency of just 13 to 16% and they also have lower space efficiency.

Generally, the solar industry highlights the low costs of p-Si and also the technical components of solar cells, yet these components represent less than half the cost of an installed solar system. Larger costs arise from installation, maintenance, insurance and operation

Figure 1: The market for solar panels is expected to grow at CAGR of around 17% between 2017-2024.

Thin solar panels, many of which are in the early research and testing stages, have showed the most potential in terms of efficiency. This especially applies to copper indium gallium selenide (CIS/CIGS) solar cells. It has been found, however, that newer thin film technologies degrade quicker than older models, offsetting much of the presumed benefit.

What if there was a technology that could not only sidestep the issues of efficiency and economy mentioned above, but also help to reduce the burden on electrical grids?

Solar’s next stage

An evolution in PV technology could hold the answer to these problems by potentially avoiding them completely. Nextgen Nano has developed the PolyPower solar cell, which combines organic semiconductors and PVs. Using lightweight organic polymers in place of silicon, the cells can be used to make flexible and semi-transparent solar panels.

The last few years have seen rapid progress in increasing polymer solar cell efficiency from 10 to 17% power conversion efficiency. Given the high efficiency of polymer solar cells, it is expected that the efficiency of transparent solar cells can reach beyond 13%. That would open up a huge market for building integrated PVs and other energy harvesting applications that require transparency. What makes the system different is the use of nanotechnology.

Nanotechnology is already making new materials available, and it is likely that it will make solar power more economical by reducing the cost of constructing solar panels and related equipment.

This technology has the potential to transform and decentralise energy applications like electric vehicles (EVs). The benefits it will bring is that, rather than simply plugging EVs into charging points connected to the grid, there is now the potential to charge the vehicle through panels contained within the car itself. There is also scope to use the flexible and semi-transparent solar panels in technology in wearable devices, military hardware and other electronics devices.

The potential for decentralised power could alleviate the expected burden on electrical grids; at least 89% of air emissions associated with electricity generation could be prevented if electricity from PVs displaces electricity from the grid.

Current technology makes typical solar panels limited in their application. They are expensive, brittle and cumbersome and require large surface areas to provide any meaningful power generation, which must be supplemented by a centralised power source. Flexible solar panels applied to structures with wafer-thin, robust application allow transportation vehicles and other applications to supplement their power reserves, using PV.

Figure 2: EVs could charge through panels contained within the car