At the 1878 Paris World’s Fair, a steam-driven printing press gathered crowds for days. How was that steam created? With a 20-square-meter concentrating reflector that used the sun’s rays to boil water and produce steam. In other words, with solar thermal technology.
Humans have used the intense energy of the sun to heat liquids for centuries. Starting in the late 1800s, it was common practice to heat water with the sun in the southwestern United States. At one point, almost a quarter of the residents of Los Angeles relied upon the sun to heat their water with rooftop solar thermal systems.
With this persistent application starting in the United States 130 years ago, where do we square up next to solar thermal powerhouses on the world stage such as China, India and Europe now?
It would be an understatement to say that the solar thermal market in the United States is underdeveloped in comparison to the widespread applications found elsewhere.
By the end of 2009, China installed 59% of the world’s solar thermal (101.5 GWth), with Europe accounting for 32.5 GWth. The US and Canada had a combined capacity of just 15 GWth- a fraction of China and Europe’s capacity.
Though lacking the high-tech sexiness of solar electric or the majesty of wind turbines, growth in solar heat is still trending up. 2012 was a year of impressive growth for solar thermal, with an extra 39.5 GWth of new capacity added globally- an increase of over 25% on 2011- according to the International Energy Agency (IEA). If IEA’s predictions hold up, at least 26 GWth will be installed in 2013, as well.
China installed 80.6% of those 2012 additions, and 10.2% installed throughout Europe. The US and Canada were only responsible for about 2% of new growth in 2012.
What’s the big deal, anyway?
Compared to photovoltaic systems, which rarely reach more than 17% efficiency, solar thermal systems can reach efficiencies of up to 80% because they use the sun’s heat directly.
Solar thermal systems can be used for hot water heating, space heating and cooling, pool and spa heating, and industrial process heating. In a typical residence, solar thermal can handle the hot water and space heating, which can make up roughly 50% of the building’s energy requirements.
Solar thermal is a time-tested technology that is a piece of the solution for mitigating climate change. Clean, efficient, and compact, solar thermal has taken off in some countries, but lags behind in the US. But, have no fear! Next time, we’ll explore some of the ways solar thermal is working in the US, and how policies and incentives are helping solar thermal take root on rooftops across the Mid-Atlantic.