Solar Thermal Energy – cheaper & easier than Photovoltaics

Written by Levent Bas



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.