Do we need a solar power technology breakthrough?

Hillary Clinton’s commitment to making the United States more reliant on renewable energy – should she enter the White House in 2017 – and to increase the country’s solar energy capacity by 700% is very bold indeed.

Viewed in the context of the development of solar technology, such an ambitious proposal could be as significant a change in the long term as IBM’s introduction of the personal computer over 30 years ago.

So is it feasible?

Scaling up

In terms of the technology, Clinton’s proposal is certainly doable. Photovoltaics (PV) is a recent form of power generation, sharing its origins with the development of the transistor midway through the last century.

Up until around 1990, solar was principally limited to industrial applications, providing electricity to satellites, powering small remote installations and a few large-scale demonstration projects. Most solar cells did not leave the research laboratories in the US, Japan and Europe.

The situation changed when, in 1991, the German government announced the 1000 Roofs Program, which was expanded in 1999 to 100,000 roofs, at the cost of, in today’s currency, around €560 million.

This initiative ultimately resulted in the total 38 gigawatts (GW) of photovoltaic modules being installed in Germany (and 88 GW in Europe) by the end of 2014. This compares with some 18 GW which have, to date, been installed in the US.

The US lags Europe in solar production, where Germany has an aggressive renewable energy policy.Tim Fuller/flickr, CC BY

This growth, however, has not been without pain. By the mid-2000s, the rapidly growing photovoltaics (PV) industry suffered supply constraints with its primary material feedstock – crystalline silicon – which, up till then, it shared with the microelectronic industry.

The response of the global PV industry to the apparent “silicon shortage” was dramatic: over the subsequent decade, most of the cell and module manufacture moved to China and the Far East. And the manufacturing costs dropped by more than a factor of four.

Aftershocks are still being felt today. The current low prices due to a substantial oversupply mean that the remaining companies struggle to remain in profit. Further price reductions in silicon photovoltaics are therefore in the immediate future unlikely, but there is a host of other technologies waiting in the wings.

Thin film solar cells are already being produced and installed on a large scale, and dye sensitized and organic solar cells are making rapid progress in the research laboratories. There are also more exotic concepts based on making solar cell materials using nanostructures to improve the conversion of sunlight to electricity.

Compared to Europe

So how much more solar capacity will the US need to add to achieve the targets outlined in Clinton’s plan? In terms of the volume of photovoltaic modules needed, it would require a target of installing the photovoltaic capacity of some 150 GW in the US by 2027.

The photovoltaic industry estimates that some 1,000 GW of modules will be installed in the world by 2025, so that the US installations are then likely to represent less than 15% of the world total. Despite a slowdown in European installations, Europe is likely to reach a similar capacity as projected for the US before 2020.

It’s possible then to describe the Clinton target as challenging but ultimately doable. All US installations need to do is catch up with Europe and the rest of the world. Thinking big: a solar farm in Long Island, New York.Brookhaven National Laboratory, CC BY

Reaching the target is also likely to encounter other challenges, however. The integration of a relatively large number of intermittent generators such as photovoltaic modules (and also wind turbines) does not fit easily with the structure of the centralized electricity supply that we have in most countries around the world today.

Some of the problems are of an economic nature. Because the price of the fuel for solar and wind generators is free (the sun and the wind), at times of high renewable energy generation, the wholesale electricity price can drop substantially (in extreme cases becoming negative), reducing the profit margins of conventional generators.

Many countries that already have or are planning to have a high penetration of renewables are strengthening their high-voltage transmission networks so as to counter the geographic variations of when renewable energy is generated (solutions to this problem may also exist at the local level).

Again, these challenges can be overcome, particularly as the target total US PV generation capacity is likely to be in the region of 14% of total generation capacity (including nuclear and particularly fossil fuels which can be dispatched at will and compensate the fluctuating nature of solar), in comparison with the current German solar generation capacity of 22%.

But the electricity prices will undoubtedly have to rise. The electricity price in Germany, where consumers pay to subsidize renewable electricity, is currently about three times those in the US. It will be interesting to see how the American public will respond.

Upside for new technologies?

A significant challenge will be to incorporate energy storage that will be necessary to smooth over the intermittent generation. At present, electricity is generated when it is required and the energy storage introduces a novel component; questions and uncertainty remain both about the system aspect and the availability of suitable large-scale technologies that can used to meet this need.

Will solar panels become as commonplace as personal computers?medienzeitmaschine/flickr, CC BY

But perhaps the most significant impact of the Clinton initiative could be that the acceptance of solar generation in the US would trigger a “paradigm shift” resulting in major technology developments that one can only speculate about at this stage – along the lines of IBM PC, which catalyzed broad adoption of computer technologies.

With more rapid adoption of solar power, researchers and investors, for example, could step up efforts to commercialize new types of solar cells.

These changes might include a wholesale revolution in the way that we generate and use energy, including transport and heating. It might also include the electrification of the poorest regions of the world, without relying on power supply grids.

Although the Clinton target is achievable with the current technology, the impetus and funding that would result might bring in yet unknown types of solar cells and other generators that would transform the energy sector beyond recognition.

Tom Markvart received funding from UK Government research councils.