Sunday 27 May 2012

The Best Looking Solar Panels You’ve Never Seen

Perfect Symmetry?
If you are interested in having solar PV (electric) panels, but are discouraged by the effect the installation will have on how your home looks you are not alone. 

The headlong rush to get solar electric systems installed before cuts to the wildly popular government incentive scheme, the Feed-in-Tariff, created a focus on financial returns as the only goal.  A number of Crimes Against Architecture may have been perpetrated.  Ladies and gentlemen of the jury, its up to you.  Consider the gallery below.

Exhibit A

Have these installations knocked more off the value of the property than they will ever make in Feed in Tariff profits?  Am I being too harsh?  Let me know what you think - post a comment below.

Got any any better (worse!) photos of solar installations? Send them to me at this email address: and I’ll enhance the gallery. Credit given to contributors.

[UPDATE: Thanks to all who have sent photos - I have created an album on Flicker which you can see here]
An arbitrary Feed-In-Tariff banding structure has encouraged people to fit the maximum number of panels possible up to the 4kWp threshold at which the tariff reduces, sometimes with little thought for aesthetics.

Standardised solar installation kits offering a fixed number of of panel numbers further limits the chance of creating a sensitive roof layout.

The good news is that it doesn't have to be this way. There are alternatives available to those who want to reduce their energy use while protecting the appeal of their property.

It Doesn’t Have to Be This Way - The Best Solar Panels You’ve Never Seen

The default installation of solar pv is a rack-mounted checkerboard of solar panels mounted above the roof covering.  Due to their ubiquity many people think this is the only option available.
Fortunately for those who want a more harmonious-looking  installation, alternatives  do exist.  So-called integrated solar panels that replace tiles or slates in the roof covering, offering a much neater, low-profile installation.  These can be either tile-format panels where small panels fit into the tiles of the roof, or rectangular panels with a weathertight interface between panels and tiles.
Roof integrated solar panels (left) and solar tiles (right)

Some properties with smaller or awkward roof areas might be better served with a solar heating system. This requires far less roof area than it's electric counterpart, and can also be installed as a roof integrated system.  The forthcoming Renewable Heat Incentive could make this type of solar more popular, and systems installed now will qualify for the incentive once it starts as if installed on the first day of the scheme.

For more examples of roof-integrated solar panels check out the Viridian Solar Gallery.

Wednesday 23 May 2012

Peak Toil - Update on UK Photovoltaic Market

Challenge to Business Studies students:

Look at the chart above and write a business plan to create a sustainable long-term business based on photovoltaic solar in the UK.  Your plan must take account of the fact that the spikes are randomly imposed by the actions of the greenest government ever, determined as it is to help the industry by continuously "improving" the Feed-in-Tariff, the grant scheme that creates the demand for your products and services.

This is an update of an earlier chart showing the effects changes to the Feed in Tariff (FIT) have had on installation rates of solar PV in the UK.

Worried that they would over-spend the Treasury budget cap for the FIT, the government announced its intention to cut the subsidy in half from December 2011.  The ensuing rush of installations to get in before the cuts was followed by a second peak at the end of March 2012, as it became clear that the government had acted unlawfully with it's first date, and the new FITs would come in from March 3rd.

A third mini-peak erupted in the run up to April 2012 as another change was made to the FITs requiring that houses should have an Energy Performance Certificate (EPC) with a rating of D or higher to qualify for the FIT.

Following the third deadline, solar PV installation rates have remained stubbornly low, despite prices for PV having fallen to a level that means the return on investment is apparently similar to that during 2011.

The current Feed in Tariff rates and requirements can be found here.

Monday 14 May 2012

More Like a Car Than a Computer - Improvements in Solar PV Panel Efficiencies

Hard work if you can get it
How PV solar efficiency has improved over time

My phone has more computing power than it took to put a man on the moon, doesn't it?

Nowadays we take epic rates of improvement in performance and cost for electronic products in our stride.  It's a commonly held belief that the performance of PV solar panels are following a similar trajectory, but what does the reality look like?

Since 1975, the National Renewable Energy Laboratory in Colorado, USA has been plotting the current world's best efficiency for a range of different types of solar photovoltaic cells. The image above is a simplified version of a more detailed chart. I have shown only the three technologies in most common use and added two recent technical developments of great promise.

The efficiency shown here is not what you would expect to achieve from a commercially available solar pv panel, rather from a small, carefully prepared, no-expenses-spared laboratory sample.

The graph tells a story of hard-won gains over long periods of time more akin to the gradual improvements in fuel efficiency in cars than to improvements in computers, LCD televisions and digital cameras.  In the same time scale that rooms full of mainframe computers have shrunk down to fit into you pocket, the efficiency of solar panels has increased from about 14% to about 24%. 

You see, the bad news is that there's a Law's-of-Physics-type-limit to the efficiency of a solar cell and it's only 34% for the single junction technology that most solar panels use.  As you approach this limit the gains get harder and harder to win. You can see that the world record for silicon solar cell efficiency started to flatten off around 1995, polycrystalline around 1998, and that thin film cells are reaching a similar point right about now. 


Bright New Stars

Two exciting technology developments that have the potential to drive future improvements are organic cells and multi-junction thin film cells.

Organic cells are made from plastic photovoltaic materials, with the benefits of low cost and simple manufacturing processes that such materials bring. As can be seen in the graph, these new materials are just starting out, with low but rapidly rising efficiencies. They are quickly approaching the point where interesting applications will emerge - for example where the larger areas needed for the same power output are not a disadvantage, or the shapes that can be formed are important.

Multi-junction thin film cells sidestep the efficiency limit of conventional solar cells. Layers of photovoltaic material are stacked one on top of the other, each tuned to a different wavelength of light.  As light travels through the stack, each layer slices out the energy associated with the colour of light to which it is tuned.  The theoretical limit to efficiency for such a cell jumps to 64%.  Laboratory samples have already broken through the efficiency limit for a single layer cell.

There's good reason to be optimistic that further progress can be made in PV technology, just remember that today's laboratory record-breaking material can take many years to find its way into proven, real-world products.