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The Energy Opportunity in Wasted Heat

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For every one unit of energy that is converted into electricity in power plants today, two units of energy are thrown away. This wasted energy is primarily in the form of heat – or thermal energy - and, there is technology available today that can turn this waste into a usable energy stream.

Combined Heat and Power (CHP) is a technology that combines power generation and usable heat capture equipment to increase the overall efficiency of the power plant. These two energy streams can then be used locally (for example, in a manufacturing process) or transmitted via power lines and pipes to local communities. This approach allows more energy output from the same amount of fuel input, allowing society to get more from its limited fossil fuel resources.

Today, the majority of electricity generated in the United States comes from power plants fueled by fossil fuels (coal, natural gas, and oil). These plants run with an efficiency in the ballpark of 33%. The remaining 67% is mostly released into the environment in the form of heat. In CHP facilities, the bulk of this heat is recovered and used, leading to real-world efficiencies of more than 75%. Some CHP facilities in the United States have documented overall efficiencies of more than 87%.

CHP technology has been used in the United States for more than 100 years. Today, about 8% of the country’s electricity generation capacity comes from 82 Gigawatts (GW) of installed CHP. By comparing the efficiency of these facilities to typical fossil fuel plants, one can say that these facilities are responsible for reducing the country’s carbon dioxide emissions by 300 million metric tons per year – the equivalent of taking 50 million cars off the road.

Today, most (87%) of the U.S. CHP fleet can be found at manufacturing facilities. From an efficiency standpoint, this is great – one avoids transmission and distribution losses by co-locating supplies and end-users. It is also an advantage to the production facilities themselves, giving them relatively cheap and dependable energy streams that make them more competitive in the marketplace.

In the European Union, 11% of the region’s electricity is generated using CHP technology. While some countries have very little or no installed CHP (for example in Greece and Cyprus) others generate more than a third of their electricity using this technology. In Denmark, 43% of total electricity generation comes from CHP (co-generation) facilities.

Seeing the significant potential that exists for CHP in the United States, the Obama Administration has set a target to increase the size of the U.S. fleet by 50% by 2020. This means 40 GW of new CHP capacity over the next 8 years.

Some of this new capacity might be found in the upgrading of existing facilities, instead of building new power plants. Historically, CHP infrastructure at manufacturing facilities in the U.S. was sized in proportion to the baseload heat demand at the plant itself. The is different than in some other countries, where CHP facilities are “oversized” in order to supply local heating and cooling needs. The U.S. fleet could be redesigned to meet this outside demand.

According to the U.S. Department of Energy, a lot of potential also exists in commercial buildings around the country.

State governments, seeing this potential, have already begun to give CHP technology increasing policy support. Today, twenty-three states recognize CHP as a part of their renewable portfolio or energy efficiency recourse standards.

But, barriers exist that discourage CHP deployment in the United States. The most significant might be a lack of awareness and widespread willingness to adopt and use heat outside of industrial processes. This relegates CHP to a much smaller market than it could operate in. And, because CHP plants still rely on fossil fuels to generate their heat and power, their environmental footprints are not negligible. This leads to concerns over the potential for new environmental regulations before the end of the facility’s initial payback period.

But, regardless of the barriers, one things is clear – we throw away a lot of energy. But, the technology exists to allow us to recycle this waste, turning it into a valuable energy stream.

Photo Credit:

1. Graphics courtesy of the U.S. Department of Energy.

The views expressed are those of the author and are not necessarily those of Scientific American.

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