On Rooftops Worldwide, a Solar Water Heating
Revolution
Lester R. Brown
The harnessing of solar energy is expanding on every front as
concerns about climate change and energy security escalate, as
government incentives for harnessing solar energy expand, and as
these costs decline while those of fossil fuels rise. One solar
technology that is really beginning to take off is the use of solar
thermal collectors to convert sunlight into heat that can be used to
warm both water and space.
China, for example, is now home to 27 million rooftop solar water
heaters. With nearly 4,000 Chinese companies manufacturing these
devices, this relatively simple low-cost technology has leapfrogged
into villages that do not yet have electricity. For as little as
$200, villagers can have a rooftop solar collector installed and
take their first hot shower. This technology is sweeping China like
wildfire, already approaching market saturation in some communities.
Beijing plans to boost the current 114 million square meters of
rooftop solar collectors for heating water to 300 million by 2020.
The energy harnessed by these installations in China is equal to the
electricity generated by 49 coal-fired power plants. Other
developing countries such as India and Brazil may also soon see
millions of households turning to this inexpensive water heating
technology. This leapfrogging into rural areas without an
electricity grid is similar to the way cell phones bypassed the
traditional fixed-line grid, providing services to millions of
people who would still be on waiting lists if they had relied on
traditional phone lines. Once the initial installment cost of
rooftop solar water heaters is paid, the hot water is essentially
free.
In Europe, where energy costs are relatively high, rooftop solar
water heaters are also spreading fast. In Austria, 15 percent of all
households now rely on them for hot water. And, as in China, in some
Austrian villages nearly all homes have rooftop collectors. Germany
is also forging ahead. Janet Sawin of the Worldwatch Institute notes
that some 2 million Germans are now living in homes where water and
space are both heated by rooftop solar systems.
Inspired by the rapid adoption of rooftop water and space heaters in
Europe in recent years, the European Solar Thermal Industry
Federation (ESTIF) has established an ambitious goal of 500 million
square meters, or 1 square meter of rooftop collector for every
European by 2020—a goal slightly greater than the 0.93 square meters
per person found today in Cyprus, the world leader. Most
installations are projected to be Solar-Combi systems that are
engineered to heat both water and space.
Europe’s solar collectors are concentrated in Germany, Austria, and
Greece, with France and Spain also beginning to mobilize. Spain’s
initiative was boosted by a March 2006 mandate requiring
installation of collectors on all new or renovated buildings.
Portugal followed quickly with its own mandate. ESTIF estimates that
the European Union has a long-term potential of developing 1,200
thermal gigawatts of solar water and space heating, which means that
the sun could meet most of Europe’s low-temperature heating needs.
The U.S. rooftop solar water heating industry has historically
concentrated on a niche market—selling and marketing 10 million
square meters of solar water heaters for swimming pools between 1995
and 2005. Given this base, however, the industry was poised to
mass-market residential solar water and space heating systems when
federal tax credits were introduced in 2006. Led by Hawaii,
California, and Florida, U.S. installation of these systems tripled
in 2006 and has continued at a rapid pace since then.
We now have the data to make some global projections. With China
setting a goal of 300 million square meters of solar water heating
capacity by 2020, and ESTIF’s goal of 500 million square meters for
Europe by 2020, a U.S. installation of 300 million square meters by
2020 is certainly within reach given the recently adopted tax
incentives. Japan, which now has 7 million square meters of rooftop
solar collectors heating water but which imports virtually all its
fossil fuels, could easily reach 80 million square meters by 2020.
If China and the European Union achieve their goals and Japan and
the United States reach the projected adoptions, they will have a
combined total of 1,180 million square meters of water and space
heating capacity by 2020. With appropriate assumptions for
developing countries other than China, the global total in 2020
could exceed 1.5 billion square meters. This would give the world a
solar thermal capacity by 2020 of 1,100 thermal gigawatts, the
equivalent of 690 coal-fired power plants. This would account for
more than half of the Earth Policy Institute’s renewable energy
heating goal for 2020, part of a massive effort to stabilize our
rapidly changing climate by slashing global net carbon emissions 80
percent within the next decade. (For more information, see Chapters
4 and 5 of
Plan B 4.0: Mobilizing to Save Civilization.)
The huge projected expansion in solar water and space heating in
industrial countries could close some existing coal-fired power
plants and reduce natural gas use, as solar water heaters replace
electric and gas water heaters. In countries such as China and
India, however, solar water heaters will simply reduce the need for
new coal-fired power plants.
Solar water and space heaters in Europe and China have a strong
economic appeal. On average, in industrial countries these systems
pay for themselves from electricity savings in fewer than 10 years.
They are also responsive to energy security and climate change
concerns.
With the cost of rooftop heating systems declining, particularly in
China, many other countries will likely join Israel, Spain, and
Portugal in mandating that all new buildings incorporate rooftop
solar water heaters. No longer a passing fad, these rooftop
appliances are fast entering the mainstream.
Adapted from Chapter 5, “Stabilizing Climate: Shifting to Renewable
Energy,” in Lester R. Brown, Plan B 4.0: Mobilizing to Save
Civilization (New York: W.W. Norton & Company, 2009),
available on-line at
www.earthpolicy.org/index.php?/books/pb4