Last Word: Solar Thermal – Time to Redress the Balance

While a range of technologies exist that offer clean, sustainable renewable energy, one technology is largely neglected and ignored despite its strength in some markets and its considerable potential. It is high time that solar thermal emerges into the light, says Petri Konttinen.

As professionals in the renewable energy industry, we all know that renewable resources are critical to the future of our planet. With the pressure on fossil fuels, it is increasingly fashionable for the mainstream media to talk about wind power, biofuels and photovoltaic energy as solutions to the finite energy reserves and rising fuel prices.

But do the mainstream media — and, for that matter, those of us working in the industry — ever take a step back and consider those technologies that have not yet fulfilled their potential?

I strongly believe that, while photovoltaic is a wonderful technology fully deserving of the levels of investment it attracts, there is a second, equally viable solar technology — solar thermal. This is a technology which is largely neglected in articles, passed over by experts and ignored by the mainstream media — an oversight I passionately believe should be redressed.

I have a vision of a world where it would be as unthinkable to design a building that couldn’t harvest solar energy as it would be to design it without windows or doors. Solar thermal energy has the potential to be as mainstream and commonly accepted as fireplaces were a hundred years ago and radiators are today. I would love to see architects and builders select solar thermal collectors in the same way as they do every other core component of the build — it really could be that simple.

A solar partnership with great potential

Photovoltaic has traditionally been the dominant of the two solar technologies and I firmly believe in its potential — as long as it is utilized for the right purpose. This technology is on the brink of a huge leap forward in the field of renewable energy and it really proves its worth in generating electricity. However, it is not nearly as efficient to use photovoltaic systems for heating as it is to use solar thermal. Nonetheless, that doesn’t mean it needs to be a case of ‘either/or’ for these two solar technologies. Solar thermal and solar photovoltaic can work in perfect synergy with each other and, together, they could almost provide a total solution for powering and heating our buildings using renewable energy.

A brief look at the latest statistics from the European Solar Thermal Technology Platform confirms this. In the EU, 20% of the energy consumed is turned into electricity and 31% is used for transport. That leaves 49% of energy being consumed in heating and cooling (mainly of buildings). Much of this could be provided by solar thermal energy.

This is a powerful and significant statistic. Solar thermal technology is currently used in only a small percentage of European buildings, mostly for heating water and mostly in private houses. But almost half our energy needs could actually be supplied by solar thermal energy. It also has many advantages over other renewable energies such as wind power, biofuels and photovoltaics.

Often when wind farms are planned ‘NIMBY-ism’ becomes an issue with local opposition groups declaring that the turbines blight the landscape. Equally, using biofuels for energy production is not without challenges. As food prices continue to rise due to global shortages of wheat, there are increasing calls to halt the devotion of land to biofuel production. Solar thermal collectors do not share these issues as they are discreet, cannot be perceived to endanger wildlife and, as they are installed on the buildings they serve, have no impact on land use.

We are all familiar with the solar photovoltaic panels on the roofs of buildings. Solar thermal collectors, however, can be a more architecturally desirable solution since they do not have the same immediate visual impact. The solar thermal collector system can be designed so that no additional roofing is needed in the panel area. Instead, the joints of the collector’s glass can blend seamlessly with a copper roof. The copper heat transfer elements of the solar collector have excellent efficiency and durability properties.

The collectors have an annual solar energy yield of around 4 MWh per 10 m² per year (depending on the building’s location and orientation), with the best results achieved on a south-east or south-west facing roof. Expressing that in more tangible terms, at a peak energy price of 18.8 pence ($0.37) per kWh from utility suppliers (source:, 2008), this equates to an energy cost of £752 ($1489) to a home owner per year.

Solar thermal systems traditionally have an efficiency rate of 30%-50%, which means that up to half the sun’s energy hitting every collector will be used to heat water for the building. This is several times more efficient than solar photovoltaic systems. With 219,000 TWh of energy available from the sun every year, the potential for solar thermal systems is immense — even allowing for the inevitable rain in Helsinki, fog in London and snow in Moscow.

Approximately 10 GWth of solar thermal capacity was in operation in Europe in 2005 and this could be set to increase to at least 200 GWth by 2030. We have the ability to harness the power of the sun and, at the moment, we are only capturing a tiny amount of what is out there. Imagine solar thermal technology providing heating and cooling to buildings all over Europe. Imagine if this were adopted globally! I can see future generations looking back on the early part of the 21st century and scratching their heads, wondering why it took us so long to break away from our dependence on fossil fuels and really start to exploit the natural resources that fall on the Earth every day.

Why is more efficient solar thermal being ignored?

So why does solar thermal not get the recognition it deserves? I believe the biggest disadvantage that solar thermal energy faces is that it is not being championed by industry or opinion-formers. As a result, it is virtually absent from public awareness. According to MEP Claude Turmes from the Green Group, over 90% of the discussion on renewable energy at the European Parliament is focused on electricity, not heating.

This was confirmed by the omission of solar thermal from the International Energy Agency (IEA) report to the G8 group of countries published in June this year. This report, which formed the basis for a high profile global discussion on climate change, detailed three scenarios for the future of renewable energy — none of which prominently featured solar thermal as a key technology.

That is not to say that I disagree with all the IEA’s recommendations. I fully support the call for drastic action to be taken to address the world’s future energy needs and I do, of course, recognize the key role that photovoltaic technologies will play in achieving this. However, I feel the report reflected a tendency — long prevalent in Europe — to focus heavily on reducing carbon dioxide emissions, with photovoltaic electricity generation as the solution to global energy problems at the expense of other viable technologies.

This is because electricity is easy for the person in the street to understand, easy to control and has the strong lobby of the electricity providers behind it. A puzzling situation when we recall that electricity accounts for only 20% of energy requirements in Europe, while heating is nearly 2.5 times this. Surely more of our attention needs to turn to solutions for heating?

Or maybe it is because we still have a child-like fascination with novelty. We will clamour to investigate the next exciting thing to come along while abandoning a tried and tested technology, like solar thermal. There are many new developments in industry all the time and the mainstream media are quick to pick up on them. After 30 years of development, solar thermal energy is already well established. Perhaps that is why it no longer gets the column inches it deserves.

As each one of us is an opinion-former of some influence (even if it is just among our peers), we have an opportunity to change public perception and communicate the facts about renewable energy sources. According to the European Solar Thermal Technology Platform: ‘Turning solar thermal energy into a major energy resource for heating and cooling in Europe by 2030 is an ambitious but realistic goal provided the right mix of research and development, industrial growth and consistent market deployment measures is applied.’ I firmly believe this, but solar thermal energy has become the poor relation in the renewable energy family. Much work still needs to be done to ensure it receives the attention it deserves.

The world is heading for a huge crisis as global consumption continues to increase at an alarming rate while finite global resources diminish and the huge potential of renewable resources is not fully realized. The only way to tackle this is globally, with far greater co-operation between governments and companies sharing information at the research and development level.

We also need significant investment in manpower, resources, research and development to make the most viable technologies become solutions for the future.

We all know that renewable energy is the future — after all, we wouldn’t be doing the jobs we are doing if we didn’t passionately believe that it would change our world forever. But we also all need to play our part in making sure the world knows this, because only then can it start to become a reality.

Dr Petri Konttinen is senior consultant, Solar Division, Luvata Oy based in Finland.


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