Clean energy: How much hot air?

By Elisa Wood

February 1, 2012

NewScientist’s January 28 issue is likely to unsettle clean energy advocates – but it is worth the read.

The cover article, “Power paradox: Clean might not be green forever,” posits that even renewable energy can warm the planet, and eventually change climate, if we continue to ratchet up power production to serve our ever increasing demand for electricity.

It turns out that wind farms create heat, albeit a miniscule amount compared with fossil fuels or nuclear power, according to the article. Research from the University of Illinois in Urbana-Champaign indicates that wind turbines heat the ground nearby at night, apparently caused by the turbines sucking air downward from above.

Solar panels, too, create unintended heat. The article points to a study that indicates building a 1-TW solar power plant in California’s Mojave desert could raise temperatures in the air by 0.4 degrees Celsius. When dark solar panels cover light-colored sand, they warm the air and change temperature and wind patterns within a 300-kilometer radius, the article says.

Energy almost always creates some sort of waste heat, even in powering our cell phones and computers, says Eric Chaisson of the Harvard Smithsonian Center for Astrophysics, in the article. Electricity heats the circuits. We don’t use this heat; it dissipates into the air.

Of course, this is one of those glass half-full or half-empty issues. Heat by-products are not bad thing if we make use of them. Farmers already take advantage of the localized warming caused by wind turbines to fight frost, says the article. And while solar panels may generate heat when they cover light-colored surfaces, like sand, they cool when placed over dark surfaces, like a black roof.

More importantly, we can sometimes use recycled heat instead of fossil fuels. Residential solar panels are now available that convert waste heat from the panels into useful energy for cooling a house. And for many years we’ve captured and used waste heat in buildings and factories through combined heat and power (CHP) and recycled industrial waste heat systems.

Plenty of need exists to channel heat energy for useful purposes, including air conditioning in the US, as our aging population continues to shift southward. Globally, about 47% of the energy we consume goes toward heating/cooling, with industry as the largest single user, consuming about 43%. Homes follow at 41%, then commercial and public buildings, 9% and agriculture 6%, according to the International Energy Agency.

Should we worry that renewables generate heat? Perhaps. But the impact is small. Heat from renewables poses no immediate threat. Long term, however, waste heat from all sources could become a serious contributor to climate warming, if we continue to increase our consumption of electricity at the current rate of about two percent annually, the article says.

So clearly, it would be hard to take any argument against renewable energy seriously based on its heat output – particularly since renewables can displace fossil fuels that create far more warming. But the findings do underscore the value of exploring energy efficiency measures that make use of waste heat. We hear a lot about smart power; but stay tuned as smart heat rises up as a new priority.

Elisa Wood is a long-time energy writer whose articles can be found at www.RealEnergyWriters.com.

International plan makes efficiency top priority

By Elisa Wood

July 8, 2010

While several clean energy technologies play an important role in reducing carbon dioxide emissions, none compare to energy efficiency, according to a new report by the International Energy Agency.

“Increasing energy efficiency, much of which can be achieved through low-cost options, offers the greatest potential for reducing CO2 emissions over the period to 2050,” says Energy Technology Perspectives 2010. “It should be the highest priority in the short term.”

The report offers a “Blue Map” that lays out least-cost action to guide policymakers. Under the game plan, efficiency, by far, produces the greatest gains. End-use fuel and electricity efficiency provide 38% of the cuts in CO2 and power plant efficiency an additional 5% over the next 40 years. Carbon capture and storage comes next at 19%, renewable energy 17%, end-use fuel switching 15% and nuclear power 6%.

In the US, Europe and other developed parts of the world, retrofitting buildings will be key to success, according to IEA.

“Direct emissions from buildings account for around 10% of global CO2 emissions; including indirect emissions from the use of electricity in the sector increases this share to almost 30%,” the report said. “Most buildings have long life spans, meaning that more than half of the current global building stock will still be standing in 2050. The low retirement rate of buildings in the OECD [Organization for Economic Co-operation and Development countries] and in economies in transition, combined with relatively modest growth, means that most of the energy and CO2 savings potential lies in retrofitting and purchasing new technologies for the existing building stock,” the report said.

Great attention also needs to be paid to efficiency in developing nations, given the “startling” fact that they will be source of most of the growth in energy demand. Separately, the US Energy Information Administration reports that demand for energy will increase by 84% in developing nations, and only 14% in advanced economies through 2035. The largest and fastest growing developing countries are Brazil, China, India, the Russian Federation and South Africa.

On the plus side, these nations will construct new buildings, so efficiency measures can be installed from the get-go, offering quick and strong energy savings, the report said.

An executive summary of the IEA report is available athttp://www.iea.org/techno/etp/.

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