When people think about green energy, they often think of renewables like solar or wind power. While harnessing the earth’s natural elements to generate energy is an excellent strategy, these sources are intermittent and not always available. Also, space constraints in urban cores often make these technologies challenging to implement. Integration of wind and solar will certainly be a component of a greener future, but there are many other ways we can reduce emissions, save on fuel, and keep energy affordable by tackling the huge amount of energy wasted under current production conditions.
The United States squanders an incredible amount of energy through wasted heat. This heat, which is a byproduct of traditional energy generation processes, is vented to the atmosphere or released into bodies of water. Traditional generation and the electric grid itself are responsible for the majority of the thermal energy wasted. In fact, the United States loses more energy in wasted heat each year than is consumed by the entire nation of Japan.
One of the best ways to combat this issue is with CHP. By capturing heat that would have otherwise been wasted, CHP systems result in the most efficient use of fuel to produce clean, low carbon steam over traditional generation sources. Let’s take a look at what CHP is, how it works, and how it can help turn waste heat into usable energy to help reduce carbon emissions.
Understanding the CHP process
CHP stands for combined heat and power and is also referred to as cogeneration. CHP is an efficient process that combines the production of thermal energy (used for both heating and cooling) and electricity into one process. Unlike a traditional power plant that discards excess heat produced from its power generation process as carbon emissions, CHP harnesses this waste heat and puts this energy to good use. There are two common CHP processes that are used most often:
- In the first, fuel is combusted in a prime mover, like a gas turbine or engine. Then, a generator connected to the prime mover produces electricity. The energy normally lost in this process as heat exhaust is recaptured in a heat recovery boiler to generate thermal energy.
- In the second, a boiler burns fuel and produces high pressure steam, which feeds a steam turbine and thereby creates electricity. Upon exiting the turbine at a lower pressure, the steam is captured and used for thermal energy.
Benefits of CHP
There are many considerable advantages to CHP, both to individual buildings, campuses and society at large. CHP systems have an average efficiency of about 75%, but can exceed 80% efficiency when using steam turbines. This is versus the 50% efficiency yielded by traditional systems via separate boilers and generators. Greater efficiency means better fuel utilization. Better fuel utilization both reduces emissions and reduces costs.
Additionally, unlike many new technologies, CHP systems can be deployed quickly, and have few geographic limitations, making it easier for buildings within a district or campus to take advantage of the benefits of CHP and quickly lower their environmental impact. At the same time, CHP offers more resilient energy, especially when configured as part of an advanced microgrid. This was clearly evidenced in 2012 when Super Storm Sandy plunged New York City into darkness with its destruction of the local electric grid. But one campus stayed lit and heated – New York University’s Washington Square campus, which is powered by a 13.4-megawatt CHP plant.
Furthermore, CHP supports local economic growth by cutting energy costs and freeing up funds for other investments. According to the U.S. Department of Energy and the Environmental Protection Agency, Installing 40 GW of new CHP capacity would save U.S. businesses and industries $10 billion each year in energy costs and shave one percent off of the overall national energy demand. Such an investment would cost about $40 to $80 billion and could pay for itself within four to eight years, these agencies estimate.
A low-carbon future
So, CHP is more efficient, more affordable, and spurs economic growth. What about the environment? For starters, CHP often uses domestic natural gas, which is cleaner than coal and superior to oil from an energy independence perspective. What’s more, opportunity fuels like biofuels and wood waste are also options for CHP systems, offering an even greener approach to CHP. CHP overall, and its ability to integrate green fuels, provides cities with a tremendous opportunity to reduce carbon emissions on a massive scale. By pairing CHP with district energy networks, low carbon thermal energy can be delivered to a broad swath of buildings and generate significant carbon reduction benefits.
CHP’s emissions are inherently lower than alternative technologies, and can meet even the most stringent U.S. emissions regulations. This is partly due to its aforementioned greater fuel efficiency, which reduces greenhouse gas emissions, including carbon dioxide (CO2) and air pollutants such as nitrogen oxides (NOx) and sulfur dioxide (SO2), according to the EPA.
How much of an impact can CHP have on emissions? Let’s put it in perspective. The Department of Energy estimates that the U.S.’s current CHP deployment saves about 1.8 quads of energy annually, and reduces U.S. carbon dioxide emissions by 240 million metric tons. That’s the equivalent of taking 40 million cars off of the road. The DOE goes on to suggest that deploying an additional 40 GW of CHP could decrease CO2 emissions by an additional 150 million tons each year, which is like removing 25 million more cars from the road. In other words, CHP can have a massive positive impact on our environment and pay for itself.
CHP in action
With so many benefits and comparatively little cost to implement, it’s not surprising that in their recent Market Data: Combined Heat and Power in Microgrids report, Guidehouse Insights reported that they expect 11.3 GW of new CHP capacity to be added in microgrids globally over the next ten years.
Unfortunately, most of that implementation continues to be outside of the U.S. As with many progressive energy moves, Scandinavia leads the way. CHP accounts for 50% of Denmark’s power production and more than 30% in Finland and the Netherlands.
However, CHP only represents about 8% of the U.S.’s total generation capacity. That means that there’s enormous potential for growth. Some major U.S. cities are already reaping the benefits of CHP, including Boston, Cambridge and Philadelphia. In these communities, CHP is integrated with local district energy networks, delivering low carbon thermal energy to buildings and campuses across these cities’ urban core. In fact, CHP driven district energy has been so successful at reducing carbon emissions, its specifically tied to these cities’ climate action plans. By leveraging existing district energy infrastructure and CHP, these cities are leading the way in America’s adoption of this powerful technology and forging ahead towards a zero-carbon future.
