The rise of solar power - experts discuss developments
With technological improvements raising efficiency and lowering costs, solar power is catching up with conventional sources of energy. Rachel Lawler speaks to three experts about promising developments in the field.
Professor Stuart Irvine (SI), Director of the Centre for Solar Energy Research (CSER), Prifysgol Glyndwr University
Stephen Tay (ST), Earth-abundant and
non-toxic solar cells PhD
student, Imperial College
Dr Henry Snaith (HS), Founder and Chief
Scientific Officer, Oxford
How much have solar panels improved in the past decade?
SI The efficiency of solar panels has been steadily improving, with the best crystalline silicon modules now touching 20% and thin film panels reaching 13%, when the latter were 9% at best 10 years ago.
HS Current photovoltaics (PV) have improved considerably with respect to price. In 2004 it cost US$8/Watt peak (Wp) and it is now less than US$1. But can the price reduce much more and is solar compatible with the aesthetics of the built environment? Probably not.
ST Solar panels have come a long way, from devices found mostly in industry to widespread acceptance by the general public. Grid parity is becoming more of a reality today than it was 10 years ago, especially when coupled with Government support.
How does solar power compare to other renewable energy sources?
SI Development has been accelerating and, in terms of the reduction in cost of electricity produced, has been more dramatic than other renewable energy technologies. Some technologies, such as tidal stream power, are still at the demonstrator stage and it has yet to be proven what can be achieved, so we’re not all at the same stage.
HS It started a long way behind but is now approaching a cost comparable with wind power, and solar is much more deployable globally.
ST Wind and water turbines demonstrate efficiencies of around 60% and 85% respectively, while solar panels exhibit lower efficiencies of around 15%. Nevertheless, solar panels provide several advantages to consumers. They generate electricity without any noise and are not dependent on geographical landscapes as sunlight is widely available across all continents. And while countries located further away from the equator receive less sun, solar panels can be used to supply electricity to rural areas far away from the grid. This point-of-use power generation is unique to solar energy.
How much of an issue is energy storage in the use of solar panels?
SI With PV installed capacity in the UK set to rise from its current level of just over 2.5GW to around 20GW in 2020, storage will become an issue. There are great opportunities here to research on both the micro and grid scales to manage times when there might be a surplus of power. There are also opportunities for research in grid management, where smart meters will enable the grid to manage the flow of energy.
HS It is becoming a major issue as PV and other renewables are becoming a larger fraction of the total power generation. The current grid in the UK could cope with no more than about 20% PV. But this is still more than 10 times current installations. A massive drive to advance electricity storage is required.
ST Energy storage is a key component for utilisation of solar power. Challenges include the need for more effective cathode-anode-electrolyte systems, increased battery lifecycles and reduced costs. Although seemingly immense, I believe that with current research these challenges can be overcome.
Which areas of research do you think are most promising?
SI There are a lot of opportunities to provide solar panels that are more integrated into the fabric of a building and disguise the current, rather blocky, panels. We also hear a lot about graphene but, while it might play a role in transparent conductors, silicon will remain the most important PV material for the foreseeable future.
HS I don’t believe that silicon is the ultimate solution, nor are the current thin film technologies, so it is all to play for. My opinion, although biased, is that the new Perovskite semiconductors could transform solar power generation. Never before has a material been so cheap yet at the same time capable of reaching the very highest efficiencies.
ST The kesterite solar cell is an interesting and promising area of research as it is based on earth-abundant and non-toxic materials. If long-term production of solar panels is planned these qualities will be important. Silicon, although plentiful, is an indirect semiconductor and requires a phonon [a unit of vibration] as well as a photon to generate a charge. Kesterite is a direct semiconductor and requires only a photon. I see it as the next-generation solar panel material.
Are Government incentives a good way to encourage the use of solar panels?
SI The introduction of the Feed-in Tariff in 2010 has transformed the UK solar energy market. The UK is now in the top 10 solar energy adopters in the world so this is definitely a good idea. The growth in the scale of solar panel installation has actually helped bring costs down but the Government needs to monitor this as we move towards grid parity.
HS Yes, but we should now look at schemes that spread the cost rather than reduce it. For instance, the Government could help install panels on houses free-of-charge, but promise to sell that PV generated power at the lowest current utility price. This will mean that any technology that reaches grid parity will be adopted, even with a 10 or 20-year payback.
ST Government incentives are an excellent way to encourage the cautious consumer to try new technology, but they impose a large financial burden on public spending and this may fall on taxpayers. What I propose is funding for young, bright minds to enter the solar energy industry or research field. This could be in the form of PhD scholarships or outreach to secondary school students.
How much more work is needed before solar power becomes a viable alternative to fossil fuels?
SI This very much comes down to the cost of electricity. Southern Europe has more solar isolation that the UK and has already reached grid parity, but the UK might not reach that point until 2020. But who knows – if recent price falls can be sustained, it might occur sooner. A recent survey by the Department of Energy and Climate Change showed that acceptance of solar panels by the UK public was more than 80% – much higher than other forms of renewable energy.
HS It is already very close. The main issue is that most people don’t want to buy 20 years’ worth of power upfront. Once the payback is reduced to five years, demand will explode. Beyond this, we should be targeting, not just matching, fossil fuels and creating even cheaper power to enable the next evolutionary step in modern society and improve standards of living across the globe. The country that develops and commercialises the winning technology will do very well – power is a trillion dollar market after all – so we shouldn’t be waiting around for someone else to find a solution.
ST When consumers are convinced that solar energy will help them and they have the means to purchase panels, they will adopt the technology. It is my opinion that the general public has acknowledged the benefits of energy from solar panels. To proliferate solar energy use we must now reduce costs further through research and increase public awareness through outreach programmes.