Going off-grid was once the sign of a truly ‘deep green’ approach to life. But with the National Grid facing a capacity crunch this winter, changes in technology and a new UK Solar Strategy just published, now may be the right time to rethink our attitudes to solar power. Melanie Thompson of Get Sust! externallink investigates ...

Are you ready for the capacity crunch? We may not need to put candles on our weekly shopping lists this winter (except for the decorative Christmas variety), but it would be no surprise to read ‘avoiding power shortages’ on the National Grid’s office Secret Santa wish-list.

In early September the Grid reported that it is stepping up actions to ensure the electricity continues to flow during peak periods this winter, despite unexpected glitches in the national power-generation system externallink. Faced with emergency shut-downs at two nuclear power stations (caused by technical problems) and reductions in output at conventional generators (caused by two large fires at Ironbridge and Ferrybridge and production issues in Barking), the National Grid implemented a plan to purchase additional capacity from other sources. This Supplemental Balancing Reserve externallink plan ought not to have been needed until 2015/16 and in any case was always intended to be a short-term measure because capacity was expected to rise by 2018/19.

As it turns out, now may be exactly the right time to take the leap out of the dark. 

Whether or not the predicted nation-wide dimming of lights comes to pass this winter, the possibility casts a timely ray on the importance of a strong energy supply strategy and raises the question of why – amid the hot air blowing around on fracking, offshore gas/oil and wind power – the huge potential for solar energy has dropped down the power supply agenda (again).

As it turns out, now may be exactly the right time to take the leap out of the dark.

The bling thing

In the 1990s and early 2000s, ostentatious deployment of shiny photovoltaic (PV) panels was criticized by some in the sustainable construction sector as being ‘eco-bling’ (Get Sust! was as guilty as other commentators on this score). However, back then there was a legitimate point being made: that developers, clients and building owners were ignoring the core sustainability message of “fabric first”, and opting instead for the easier-win, highly visible solutions of PV panels and micro-wind turbines.

But now – with stricter Building Regulations, corporate and domestic energy reporting requirements (through energy performance certificates and display energy certificates, EPCs and DECs), and the falling cost of PVs – this high-tech solution to energy demand ought to be much higher up the power-supply pecking order.

Solar is certainly going great guns in Australia, where a surge in the installation of rooftop systems resulted in ‘free energy’ (in the form of price deflation externallink) for a week or more in Queensland in July 2014. Meanwhile in China, which has a much more varied weather pattern than sunny Australia, at least 12GW of solar power was installed in 2013 (twice the previous record amount, according to Bloomberg New Energy Finance (BNEF)) and that trend will continue.

In the UK, small-scale (under 5MW) installations have increased, according to government data based on the feed-in tariff. Overall solar PV capacity at the end of 2013 was 2,805 MW, an increase of 59 per cent (1,041 MW) since the end of 2012, and amounting to 508,222 installations in 2013 – up 26 per cent compared with the 2012 figure. The most recent data externallink (July 2014) shows a further increase to 3,867 MW (589,596 installations).

The government’s Solar Strategy externallink, launched by the UK climate minister Greg Barker in April 2014, attempts to address the planning barriers (at least for domestic-scale installations), which is just as well considering that the Strategy sets a challenging target of one million rooftop installations by 2015. Putting this into context with the figures quoted above, leading solar provider SolarCentury estimated in July externallink that there are only around 13,000 rooftop installations in London – including the 6000m² ‘solar bridge’ over the Thames at Blackfriars Station externallink.

Subsidy blight

Earlier this year the government completed a consultation exercise into the need for subsidies, particularly for larger-scale rooftop installations.

According to the Solar Trade Association, “British solar just needs one final push, one last period of support, before it can achieve solar independence and compete subsidy-free.”

As the consultation drew to a close, more than 150 businesses wrote to the Prime Minister to underline their concerns about its proposals. Jeremy Leggett, Chair of SolarAid and Non-executive Chairman of SolarCentury, who handed the letter over to Downing Street on behalf of the signatories said:

“Despite all of the incredible achievements of the UK solar industry since 2010, it’s still very clear that the Whitehall mindset has yet to catch up.”

The letter and responses to the consultation are still under consideration, but in early September the new minister of state at the Department of Energy and Climate Change (DECC), Matt Hancock, reiterated the government’s support for the technology as part of the UK’s energy mix.

The problem with subsidies is that past experience shows there is a risk of stoking up a short-lived bubble of activity, rather than a long-term acceptance of a new technique or technology.

For example, retrofitted PV panels did experience several brief moments in the sunshine as a result of very tempting government subsidies at the turn of this decade. But when the carrots proved only too tempting and the government reduced the benefits externallink of purchasing and feeding in power to the network, interest waned. It was as if the nation was collectively holding its breath waiting for another tempting offer.

So it will be interesting to see whether there will be a significant rise in the number of domestic retrofit installations from July 2014, which is when the famous furniture store IKEA began selling PV panels direct to the public through its partner, Hanergy.

People power

With luck, the considerable marketing power of the furniture giant may help to tempt people back into the retrofitting market: making solar power a fashion item rather than a government-prescribed panacea to high home energy bills.

IKEA’s strategy is to rouse us from our apathy (chucking out more chintz externallink as we go) and drive sales through a simple online self-assessment system which asks homeowners for a rough idea of the roof orientation and pitch, then uses the power of Google Maps to calculate the cost and predicted first year and 25-year savings that could be achieved.

All of which is great, but when a leading PV researcher confesses in a TED talk that her home has no PV panels, it is clear that fashion statements and subsidies (availability or lack of) are not the only barriers to take-up of domestic or larger-scale photovoltaic technologies.

Professor Alison Walker, Director of the Centre for Doctoral Training on New and Sustainable Photovoltaics externallink at the University of Bath (Department of Physics) lays the blame for the slow take-up of PV technology – at least in part – at the door of the construction industry. While domestic-level installations can be fairly straightforward, PVs for schools and offices (which require large amounts of daytime electricity and are therefore well-suited to the technology) can be more complex in terms of design. The need to meet BREEAM requirements, and the general lack of easily available installation information can be off-putting.

“[B]uilders are very conservative,” says Walker.

Professor Walker’s TED talk externallink (which runs to approximately 15 minutes) includes a neat counter to the arguments that we simply do not have enough sunlight in the UK; but she cites the lack of south-facing roof space, problems with shading (especially in cities) and the need to gain planning permission as other barriers to wider take-up of PV technologies.

East, west or south is best?

However, Professor Ralph Gottschalg of Loughborough University says at least one of those barriers can be overcome with relative ease.

“The installation of south-facing systems is ideal to maximize energy yield of PV systems,” he explains, in a news article externallink for the University. “[But] in the case of a domestic system such as a typical family home, there is little that can be done about roof orientation anyway!

“The case is different for large scale systems on flat roofs. These tend to be installed at shallower pitches ... These systems may benefit from an east-and-west facing system as there is significant potential for cost savings. It is important to note that one has to install an east-facing system as well as one west-facing system – there is no benefit in terms of costs just to rotate a single system.”

According to Professor Gottschalg’s calculations, an east-and-west system may produce less energy than a south-facing one (of an equal size), but the former tend to be installed at relatively shallow angles and thus the overall loss is not too high.

In particular, east-and-west facing systems have an extra benefit, because the time of generation peak of an east-facing system is towards the morning, and for the west-facing one it is towards the afternoon, resulting in a much more even energy profile over a day. Such systems are in use in Germany, but the UK is some 5-10 years behind in terms of the number of such installations.

There are also economies of scale (installing twice the capacity gives better prices) and in terms of manufacturing (see www.sustainablepractice.org/tag/solar-panels externallink for an example of such a system).

Ralph Gottschalg suggests that PV system designers tend to focus on optimizing a single system for energy yield and overlook other opportunities. But even with such economies, the cost is still the main factor holding back the success of PVs.

“Unfortunately, [clients still] don’t look at life-cycle costs or operating costs. In companies, operating costs are one budget line, building costs another and the impact from one on the other is often not considered”, he says. “How to overcome this? Honestly, I have no idea.”

Professor Gottschalg says that, even though the price of wafer-based technology is continuing to fall, the device cost/efficiency and system costs are not straightforward. He suggests that the actual semiconductor cost is not the dominant factor: it is more to do with production, installation and design costs (see, for instance, Energy Generation of PV Systems: Risks and Due Diligence externallink, 29 September 2014).

Professors Gottschalg and Walker are both leading teams that are focusing on the physics of the photovoltaic materials and how to build better systems. So should we just wait a little while longer to reap the benefits of their labours?

In part, this has been a problem of the sustainable construction sector’s own making... 

Time to abandon the waiting game?

That has been the attitude of many clients and homeowners – waiting either for the next round of subsidies, or until the next generation of technology comes on stream. The problem with that approach is ‘how long should we wait’?

In part, this has been a problem of the sustainable construction sector’s own making. Many years of using payback as a way to try to persuade homeowners and clients to invest in energy-efficiency measures and technologies has resulted in a counter-intuitive inertia, whereby we all delay taking the plunge because we’re being told that systems will achieve payback in 25 years’ time.

That approach is fine for fit-and-forget measures such as additional insulation, (natural) ventilation systems and even, to a certain extent, heating systems; it also works in the commercial sector where fit-outs are programmed into the building’s lifecycle. But it no longer makes sense to try to encourage market growth for ‘big ticket items’ such as buildings-integrated photovoltaics – for new-build or retrofit projects – on the basis of long paybacks, because everyone knows that superior technology is just around the corner. The only thing we can’t be certain of is the precise distance to the corner!

Motor manufacturers, and software and IT developers are very familiar with this problem: they need to persuade customers to invest in a vehicle or system today in the full knowledge that a better one will be along the day after tomorrow. Apple externallink has got this marketing approach down to a fine art.

So, in the spirit of Steve Jobs, here is a quick summary of PV technologies that are in development (edited from a extract provided by Prof. Alison Walker). But please don’t let these exciting developments put you off investing in today’s energy-saving, money-saving, carbon-reducing PV technologies.

Technology Advantages Disadvantages
Thin film technologies (based on non-silicon semiconductors such as CdTe, CdSe and CuZnSnSe)
  • Light-absorbing layers are just one micron thick (compared with 350 microns for traditional silicon wafer cells)
  • High efficiency (within a few percentage points of crystalline silicon)
  • They need to be put between glass panels
  • They use toxic elements Cd, Te, Se
Kesterite solar cells (based on CuZnSnSe)
  • Much more sustainable than the thin film types above
  • Efficiencies have so far reached only 10% (compared with 20% for thin film)
Amorphous silicon (thin layers similar to CdTe)
  • Cheaper than crystalline silicon
  • Degrade quickly
  • Similar efficiencies to more recent cells (see below)
Organic solar cells
  • Very thin layers
  • Can be made by printing (i.e. low energy budget techniques)
  • Flexible
  • Good for portable PVs to replace batteries
  • Low power efficiency
  • Degrade quickly
Dye-sensitized solar cells
  • Do not need to be put between glass panels
  • Semi-flexible and semi-transparent and come in variety of colours
  • Can be made using roll printing methods
  • Most materials required are cheap and non-toxic
  • Efficiencies around 11% (slightly better than organic cells)
  • Not very stable
  • Best dye contains ruthenium and cells also need platinum, both of which are expensive
  • Conventional dye cells contain a highly corrosive liquid electrolyte so most research on solid state replacements which are only 7% efficient for the moment have been superseded by perovskite cells (see below)
Perovskite cells (a recent development from Oxford University)
  • Extremely rapid efficiency improvements over 2 years (now similar efficiencies to CdTe cells that they may also supplant)
  • Potentially low cost because of the low temperature solution methods and the absence of rare elements
  • High potential for building integrated solar cells
  • Currently stability is a major concern