CNC Report 08.26.24 8.5x11 - Flipbook - Page 130
04 TIMELINE TOOL
Annual Balance, Avoided Emissions And Net-Zero
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The basis of the timeline tool is an annual balance of positive “emitted” carbon dioxide (e.g.
building heating and cooling) and negative “avoided/sequestered” carbon dioxide (e.g. PV yields
and tree growth) emissions.
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Whereas, sequestration is a clear carbon removal method, the term “avoided” emissions can be
critically discussed. By assuming that the produced “clean” PV electricity is replacing the same
portion of “dirty” grid electricity, one claims the negative benefit of the grid emissions per kWh of
PV yield.
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To achieve net-zero, the “emitted” quantity of emissions has to be equal to the “avoided/
sequestered” quantity of emissions on an annual basis.
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But, as grid emissions vary over the time of year and time of day as well as between different
regional grids, the actual moment of pulling electricity from the grid and feeding PV electricity back
into the grid can have a big impact on the actual emissions.
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As more and more private or public entities feed their surplus PV yield into the grid during sunny
summer days, the grid mix gets “cleaner” during that time. On the other hand, during cloudy winter
days, almost nobody feeds in and most pull from the grid which at that time is relying on traditional
sources like gas or coal power plants.
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An annual balance doesn’t show or represent these dynamics. Due to the complexity of modeling
the dynamics, it is often not feasible to do a balance on smaller time-scales (daily or weekly).
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But still, it should be kept in mind that there are solutions to cope with the increasing imbalance of
emission intensities in electricity grids: thermal and battery storage systems. The latter are better
suited to cover short-term scarcity of renewable energy (day-night cycle). Thermal storage systems
(geothermal, chilled/hot water, etc.) are the preferred choice for seasonal cycles.
Emission Trends
Based on the “Annual Energy Outlook” from the U.S. Energy Information Administration, the emission
trends were defined as seen on the left.
These trends represent a more conservative assumption of the transition towards a “greener” energy
grid and industry in general. They are not aligned with the goals of the current administration to be
climate neutral by 2050. By using these trends, it is ensured that the focus of the CNC remains on local
interventions like PV or sequestration to reduce emissions on site rather than trusting that the emission
will fall otherwise in the coming decades.
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archimania
Transsolar
KlimaEngineering
