Energy cyberspace is replete with figures of carbon dioxide intensity per kilowatt-hour (CIPK) of various types of power generation. Mostly these figures are in general agreement. One good resource is the World Nuclear Association‘s summary of an Intergovernmental Panel on Climate Change (IPCC) study that represents a sort of “halfway” point in scientific literature estimates of these figures. These are lifecycle figures, i.e., they represent “all-in” carbon dioxide—all the CO<sub>2</sub> involved in putting each kWh of electrical energy into a grid.
For whatever reason, WNA likes to display data using vertical bar charts, with long x-axis labels that make you twist your head counterclockwise in order to read them. We at CNWC like to present data that’s easier to read. So here, in a horizontal bar chart, are the WNA CIPK estimates, based as mentioned on an IPCC study.
As you can see, the “non-emitting” sources—solar of various types, hydro, nuclear, and wind—carry by far the lower CIPKs. However, these comparisons are misleading. Solar is a “mode zero” electricity producer. That is, in a solar power production time series dataset, the most-often-occurring output value is zero. That’s because solar does not produce at night.
Similarly, wind does not always blow, as anybody who follows Ontario wind turbine output during serious heat waves can attest. When power is needed most, wind is frequently not producing power. Though wind supporters pooh-pooh this inconvenient fact, it is hugely important.
Power is needed all through the 24-hour day, i.e., when solar panels and concentrators are not putting power into the grid, and when wind is in one of its frequent lulls. Incidences of food poisoning and waterborne diseases dropped precipitously in the Developed World when home refrigeration and indoor plumbing became ubiquitous in the Developed World, nearly a hundred years ago. Refrigeration runs all day. Potable water is available all day, because of electric pumps that run on electricity that is available at all times during the day.
How credible is it, then, to publish figures of the CIPK of generation types that can provide power 24/7 next to generation types that cannot provide power unless they are in direct sunlight and/or the wind is blowing?
For this reason, we present here a table that provides performance characteristics of the generation types given in the WNA-derived plot above.
| Generation type | CIPK | Dispatchable? | Baseload supplier? |
|---|---|---|---|
| Coal | 820 | âś” | âś” |
| Coal with biomass co-firing | 740 | âś” | âś” |
| Natural gas | 490 | âś” | âś” |
| Biomass | 230 | âś” | âś” |
| Solar PV (utility) | 48 | ||
| Solar PV (rooftop) | 41 | ||
| Geothermal | 38 | âś” | âś” |
| Solar (concentrated) | 27 | ||
| Hydro | 24 | âś” | âś” |
| Nuclear | 12 | âś” | |
| Wind (offshore) | 12 | ||
| Wind (onshore) | 11 |
By far the most important type of generation in an electricity grid is baseload generation. That’s literally 24/7 supply. That’s what makes refrigeration and potable water ubiquitous across the Developed World. As you can see, baseload supply is delivered by coal, “biomass” (i.e., wood), geothermal (under extremely limited circumstances that are so extremely limited by geography that we wonder why it’s even included in the WNA figures), hydro, and nuclear.
The next-most important supply is dispatchable generation. This can throttle up and down, in response to significant changes in electrical demand. There is an even narrower range of technologies capable of delivering it. Of these types, only hydro comes with a low CIPK.
As you will notice, wind and solar do not provide either baseload or dispatchable power. In fact, dispatchable sources are required to balance wind and solar. If those types have high CIPKs, then we cannot honestly say that “variable renewable energy” (VRE) has a low CIPK. The kilowatt of power that comes from the combination of the high-emitting dispatchagle source and VRE actually has a CIPK somewhere between that of the particular VRE source and the dispatchable source that “balances” it.
That means that VRE actually advances climate change faster, because it adds more CO2 to the air per unit of energy generated.
And if VRE is balanced with hydro, then we must ask what is the point of VRE.
The point of fighting climate change is to actually fight it, not to spot it points so the fight is fair. We want slow carbon—carbon going into the air as slowly as possible.
From the table above, there are only two choices: hydro and nuclear. Most jurisdictions across the world, including Ontario have already developed the most available hydro.
That leaves only nuclear as the best way to go.
Slow carbon. Reliable power.
