Solar Thermal Energy – cheaper & easier than Photovoltaics

Solar thermal energy, which is the oldest way of tapping power from the sun, has been used for years in heating applications for households. Although its counterpart solar photovoltaic seems to be getting more attraction, according to European Solar Thermal Industry Federation (ESTIF),  solar thermal energy industry in Europe has grown over 60% in 2008.

In a recent interview broadcasted by RenewableEnergyWorld.Com,  Olivier Drücke, president of ESTIF, mentions that the solar thermal potential in Europe can meet 15% of heating and cooling demand in 2030 and up to 50% in 2050. That is particularly significant given that heating and cooling demand represents 50% of the final energy consumption in Europe (with the remaining 20% for electricity generation and 30% for transportation).

Global market

According to ESTIF statistics, the fastest growing European solar thermal market in 2008 was in Germany. Germans have reached 11 million sq-m of solar panel surface area (7,765 MWt) by installing a record number of 2.1 mil sq-m in 2008.

China is reported to have almost 130 mil sq-m collectors already installed, making it the biggest market in the world (too big for the graph as well). Turkey, still one of the biggest markets in the world, installs around 500,000 sq-m each year.

Cyprus, Israel and Austria have developed their markets significantly in recent years, consequently positioning themselves as the global leaders in installed capacity per capita. Austrian manufacturers are dominating 40% of the solar thermal market in Europe.

Japan installs around 300,000 sq-m every year, and roughly 15% of Japanese households are equipped with solar water heating systems. The USA is one of the biggest markets for low temperature systems, accounting for 11 mil sq-m. However, as can be observed from the graph, the market development in medium and high temperature systems has been negligible when taking into account the country’s potential.

Is it worth considering?

In his interview, Mr. Drücke points out that developing common industry standards and offering public incentives is important. He emphasizes that creating public awareness programs is the key to having success in this industry, including a cleaner environment and more jobs as a consequence.

It is clear that installing the application is easy for households since the technology is less complicated and cheaper than PV. According to The Solar Guide, the payback period for an investment in a solar water heating system is 3 to 5 years, although it may vary a lot in different countries due to national standards and differences in manufacturing quality.

The return of investment depends on the system and the current fuel source that is being used to heat the water. It makes more sense to install a combi-system (hot water+space heating) whereby a 12-20 sq-m would completely cover a household’s water heating demand and a substantial part of its space heating demand in spring and in autumn.

How does Solar Thermal work?

The basic mechanism of solar thermal energy is to collect the solar radiation and transfer the heat directly or indirectly to its final destination via a heat transfer medium – usually a fluid.

The most commonly used applications are Domestic Hot water (DHW), Combined DHW and Space Heating, District Heating, Solar Cooling and Air-Conditioning. High Temperature Solar Thermal Electricity Generation is also among solar thermal applications. (e.g. solar tower and parabolic through applications).

The key component of the solar thermal systems is the collectors which can be divided into two groups:

  • Unglazed collectors have been used in the industry for a long time, mainly for heating open-air swimming pools. There is no heat exchanger in the system, and the water is flowing directly through long thin tubes. It is cheap and easy to install. Due to the simplicity of unglazed collectors, they cannot fulfill the needs for delivering full-time energy. Unglazed collectors are mainly used in the USA and in Australia.
  • Glazed collectors are much more efficient in supplying continuous heating and achieving higher temperatures than unglazed ones. Glazed collectors are usually rectangular boxes covered by glass, containing little pipes and tubes and a heat absorbing material inside. There are different types of collectors for different means of use. Glazed collectors are commonly used in China, Europe and the Middle East.

[sources: ESTIF Publications, IEA Country Stats, photo credit: Abri Beluga, graph by author]

Have any Question or Comment?

25 comments on “Solar Thermal Energy – cheaper & easier than Photovoltaics

I am going to quote good friend, and Solar Energy know-it-all, Nat Bullard at New Energy Finance who recently wrote a great chunk of starter info about Solar Thermal Electrical Generation. Nat, you will notice that I’ve changed your British spelling, no doubt heavily influenced by NEF, which I find ridiculous given your New York/Virginian-Harvardian accent:

“Solar thermal electrical generation (often abbreviated as STEG) and frequently referred to as Concentrating Solar Power (CSP) encompasses a variety of non-photovoltaic solar generation technologies. Rather than use photoelectric processes to generate electricity, solar thermal uses the heat of solar radiation to generate heat, from which it produces electricity via thermoelectric processes.

There are three solar thermal processes which ultimately use steam turbines to generate electricity: parabolic trough, heliostat and tower, and compact linear fresnel reflector (CLFR). They are market-established in that order, with parabolic trough comprising well over 90% of extant physical plants, heliostat and tower used in a single commercial application to date, and CLFR, which is still in proof of concept.

Steam turbine solar thermal systems use linear reflectors or tracking-axis mounted individual heliostats, all of which focus solar radiation on a collector device, which in turn transmits heat to a steam boiler and a turbine. The three technologies (discussed in much greater detail in their respective folders) operate at varying degrees of heat and steam pressure, resulting in variant thermal efficiency and capacity factor.

A fourth solar thermal technology, the Stirling engine, is a modular reciprocating heat engine which uses parabolic dishes to focus on a point, rather than a line, and operates without water in its thermal cycle.

Solar thermal is inherently a utility-scale technology. There is no ‘distributed’ application for solar thermal, as there is in PV. Because they are based on a steam turbine (which are usually 50MW+), most solar thermal systems are built around modules of 50-200MW.

Solar thermal is becoming a viable peak-load generation technology in two markets. The first is highly insolated markets with significant time-of-use power price variation, such as Southern California, where solar thermal power is seen as an offset or hedge on natural gas prices, and an invariant-cost peak load generator. The second is in the feed-in tariff markets of Europe, in particular Spain, where generators are paid an above-market rate regardless of time of use.

Solar thermal is subject to several systemic concerns. The first is the availability of water to run the steam block, which is naturally a concern in the direct normal insolation environments in which solar thermal is best-suited. Land use and permitting are also an issue, as unlike a wind farm of similar nameplate capacity, a solar thermal plant will utilize a far higher proportion of the land available in its permitted area, precluding concurrent use for an alternate activity.”


Solar energy is the purest form of energy going. Always has been. Long before there was knowledge of electricity and even longer still before there was PV, there were Light & Heat. Both of these forms of energy are brought to you courtesy of the Sun!

Many centuries of civilizations existed without electricity but none of them went without Solar Energy! Direct use of solar thermal energy requires far less storage, conversion, transportation, and utilization devices than PV. Think about it, you can stand still and get warm in the sun. You can heat rocks or water without a bunch of technology. Solar thermal applications for space and water heating has been in use for as long as we’ve used both. Solar thermal is a primary technology in developing countries for these reasons. Long before every home has electricity.

It’s rather funny to me that we in the “developed” countries often act surprised about solar thermal’s use. Have we “developed” so far that we forget how simple and essential the sun is beyond just electricity? It’s no wonder to me that Solar Thermal is seeing growth of this kind, it’s just puzzling why it took so long…

Many thanks Levent for such an interesting post and Ian for such a comment 🙂

Solar thermal indeed has many advantages over solar PV.

I am wondering why nothing was written here on CleanTechies on the Desertec project. Do you think I (or someone else) should write something on it ?

Another post I wrote for my blog that might be interesting in this discussion is this one on how solar thermal could bring up to a quarter of the total electricity generation by 2050.

I’m always happy when dispassionate articles are written about relative efficiencies of technology. Regarding dollar value, thermal solar is 3-4 times more cost effective that PV per unit of energy. If you’re an environmentalist, realizing that 50% of all energy consumed in the built environment is for space heating, cooling and domestic hot water, solar thermal is a wise choice. Coupled with the inherent efficiencies of district or “Neighborhood Energy,” solar thermal is used more and more in thermal utility applications as evidenced by the 20K Sq.M array that heats the city of Marstal, Denmark, and the 52 unit subdivision outside of Calgary, Alberta, known as Drake Landing. Thermal solar heat generated mostly in the summer and stored, utilizing a novel “borehole thermal energy storage” battery releases it in the cold months for space heating.

Efficiency of energy capture, distribution and use: keeping the energy within phase rather than converting to something like electricity, which requires transformers, stepping up/down DC to AC releases or results in energy loss. It is inherently more efficient to simply keep it as thermal energy. Which is why our nonprofit, N2e is promoting solar thermal as a resource for our neighborhood thermal utility projects. Visit us at: Also read about our Sunnyside Neighborhood Energy project in the “Green Issue” of Oregon Business at:


Excellent post!

I agree that more awareness on Solar Thermal Energy needs to be created. Your post is a one small piece of the puzzle.

I’ll see you on Twitter


Eric Bonnici

!wan van Bochove

the beauty of solar thermal is that it is so simple and straightforwarded. In the PV community solar thermal is regarded as ‘the ugly duckling’; PV is sexy, modern and expensive, making it very attractive indeed. However, we at solior have managed to shed off the ugly feathers and give solar thermal a complete makeover.

See our website and enjoy. and remember: our solar water heater is almost twice as cost efficient as our competitors..

Much attention and market growth has been focused upon the solar heating of water yet the most cost effective and simplest applications of solar thermal technology both in terms of dollar value and ease of building integration relates to the heating of air. This technology is often overlooked and its benefit relatively unknown. Whether applied in new construction or retrofitted on existing building structures each sqm of roof or wall-mounted, transpired collector surface will deliver upwards of 2-3 GJ of energy annually, with real returns of 20 – 30% on investment. Such systems often blend seemlessly with the buildings’s exterior facade and HVAC system, and will easily last the life of the building all while requiring virtually no maintenance. For more information see


We installed Apricus solar collectors for heating water, heating home via in floor hydronic heating system. We are getting ready to install the solar thermal dehumidifier by Novalaire soon. Already our savings are 65% compared to a conventional home. Once the dehumidifier is installed, we are looking at between 75 to 80% savings. Solar PV looks “sexy” as one put it, but the pay back is close to 30 years or more. Besides, one cannot heat a home with PV!


“Solar PV looks “sexy” as one put it, but the pay back is close to 30 years or more. Besides, one cannot heat a home with PV!”

Agreed, that’s why I have a carbon-neutral wood burning stove to compliment a PV electric system. I agree with your comments, but I have yet to see a PV Thermal system (solar hot water) run a gas meter backwards!!!! Yet my meter is going backwards and have sized capacity for the shortly to arrive plug in cars.

At that point, the PV electric system will cover my domestic consumption and local transporation requirements. Not the complete solution but clearly a multi-faceted solution.

Now if I could only create more roof space for my PV Thermal (domestic hot water)….

Jim Lindsey

Very sensible post and accompanying replies:

In 1980 to ’82, my company installed over 300 home solar water heaters. I’m sure some are still “cooking.”

According to my calculations, if only 300 operated for 27 years, we assisted the State of Tennessee in harvesting approximately 40,000,000 Kilowatt hours

from the sun.

This program was a result of President Carter’s mandate for TVA to promote solar in TVA’s district. If anyone cares to visit TVA’s web site, you will NOT see one word about said program on their history page. I’m sure it was just an oversight.

I have once again ventured into the solar arena, due to the fact that PV is the real future of solar. It did not take long for me to revert back to the “old fashioned” flat plate collectors. With thermal being three times more efficient than PV, it is ludicrous to sell PV, until any need for heating water has been satisfied.

Does anyone know if “carbon offset” money could be retro-active? That might possibly “offset” losing my butt years ago.

Jim Lindsey, Solar Plexus Power Nashville, TN

Solar Thermal Energy will be very popular in the next couple years for sure.

With solar thermal system manufacturers building affordable, high-quality systems in the USA these days, there is no need to import vacuum tube solar collectors from China.

After government incentives, my customers receive the components for a flat-panel, drainback system for under $ 1,200.

Payback should be under 5 years for a typical family.

Try to do that with solar PV!


I guess we all agree that solar thermal is a well known entity with proven track record. The PV is still in its infanacy. The newly started Suniva factory is making one of the mast efficient PV collectors in Georgia (

If anyone is interested, Southeast solar co is conducting a solar thermal (evacuated tube collector) training session on Friday July 24,2009 in Georgia. If interested in knowing about this contact # is (678) 957-8454.

Both PV and Solar Thermal is important now and for the future.

For heating, Solar Thermal is the best solution, cheap and efficient… and I have seen some sexy solutions at

In Denmark the biggest Solar Thermal plant is It’s 18.000m2 plant the newest plant in Sønderborg is 9000m2. Both systems has big storage tanks, and the energy (hot water) is distributed to the user via distibuted heating. Levent, you will have to come to Denmark again to visit these plants.

But to make energy to be distributed over longer distance we need to convert in to electricity, PV is the simplest solution for that. PV i still expensive, but due to the Germanys start of feed in, there is an industy now with prices going rapidly down. This 45 min propaganda video explains the solar power history

Of couse there is also the dessert projects with huge mirrors directing the sun to a tower making steam to kind of a conventional steam to electricity. This is a great soloution in e.g. desserts with lots of space and sun. But not so good in places with less space and lots of clouds.

Wind turbines, Bio gas and water power is also important sources of energy… and last but not least: Smart grid management combined with ways of storing electric energy is needed.

Levent, thanks for taking the initiative to this blog

We may all be relying on photovoltaic energy in the future, we need to spread the message loud and clear.

Thanks for sharing this type of information with all of us. Its highly motivational to see Solar Energy Systems efforts stepping up and doing the right thing for the environment and for their budgets. Good Luck.


how much pressure can we get by using this method, if i use a reflector of 1 metre square, closed cylinder carrying 3 litre water, please reply if anyone know abt this technology in detail.

Solar Thermal Energy,but it seldom saw in our life.we hope it could be used in our not far life;

Swathi Sunsource Power Pvt Ltd builds, develops and installs Solar Thermal Power Projects in India. We utilize the technology of CSP (Concentrated Solar Power) using Parabolic Troughs. All our projects are handed over to clients on a turnkey basis and we also provide servicing for the solar thermal plants. Our team consists of highly qualified technocrats and engineers in thermal power.

We have our manufacturing facility in Penukonda, Andhra Pradesh and it is spread over 50 Acres of lush land. We have already undertaken Solar Thermal power projects in India. We will be installing a 20MW plant for a famous Gujarat based company and also several other 20-40 MW projects across India.

Our Solar Thermal Plants are technologically advanced and cost effective. We have technically tied up with various German and US Based companies to increase efficiency and match International Standards. We are the first company in India to be felicitated by the Southern Gujarat Chamber of Commerce for our progress in technology.

For more info visit our website


Always appreciate a good article, thank you

As “usdoc1ga” said, solar thermal with vaccum tubes are really efficient, they have more than 95% efficiency and they deliver exccesif amount of energy. In less than a month (200Hours) we accummulated more than 400KW of thermal energy. Follow the link above to see our installation.

Could marine photovoltaic vs monocrystallines be the Uranium

Banana Skin? 5% in the five years leading up to 2010.

After that, I mean it’s interesting it trade through different markets for this oil. With solar panels being fitted by just one installer, its claimed that customers are unlikely to shop around for competitive quotes, as would happen in the rest of the year out.

Too bad solar thermal technologies do not offer the financing models that solar PV providers do.

The solar PV PPA is what is going to make photovoltaic technology a mainstream energy source in the USA.

Interested in Solar But Don't Know Where to Start? - Go Green - SustainLane says:

[…] articles on solar energy written by professionals working in this industry. For example, Levent Bas compares photovoltaics with solar thermal in his article, and Ceylan Oney analyzes differences between solar energy in Germany and […]

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