Introduction to Carbon Capture - Introduction to Carbon Capture and Sequestration - page 157

will likely use steam to regenerate the capture medium. This diverts
steam from the power cycle of the plant, which effectively imposes a
parasitic load on the power plant. We can use thermodynamics to esti-
mate the loss of electricity. First we have the Carnot effi ciency (

η fi nal )
which gives us an upper limit of the effi ciency in which heat ( Q ) is trans-
ferred into work. In addition, the steam turbines have an effi ciency of
0.75 [4.6]. If we add these contributions, we get the following equation
representing the parasitic energy of CCS for the power plant:

E par = 0.75 η fi nal Q + W comp ,

where W comp refers to the work required for compression. As an example,
this equation tells us that if the steam requirements of two processes are
the same, the one with the lowest compression cost will have the lowest
parasitic energy and be the more favorable design.
At this point, it is important to mention that energy costs are not the
only costs that matter. Energy will be an important factor in the opera-
tional cost of CCS, but building a carbon capture separation unit is an
investment that can represent as much as 50% of the cost of the power
plant. The chemicals necessary to run the capture process, for example,
may constitute a signifi cant fraction of the total capital cost of the new or
retrofi tted power plant. At the end of the day both operating and capital
costs will contribute to an increase in the price of electricity. This price
will be one of the most important factors in the selection of a new
technology.
Researchers in the chemical and materials sciences face a special
challenge when seeking to develop new chemistries for carbon capture
because it is very diffi cult to translate fundamental research cost to
manufactured cost. For example, how can we estimate the future world-
wide production price of a material that is currently handmade by a PhD
student at rate of 1 milligram per day, on a good day? Naturally, a mate-
rial that is already used on a very large industrial scale will be orders of
magnitude cheaper compared to a completely novel material. Yet if this
new material could signifi cantly reduce the parasitic energy of CCS com-
pared to known technology, it could play an important role in lowering
costs in the future. It is therefore the responsibility of researchers to
demonstrate that new materials will result in signifi cantly lower energy