Add Energy (E) to documentation

docs/measurement/sci.md

@@ -1,18 +1,42 @@
 # Software Carbon Intensity
 
-SCI = ([E](https://sci-guide.greensoftware.foundation/E) * [I](https://sci-guide.greensoftware.foundation/I)) + [M](https://sci-guide.greensoftware.foundation/M) per [R](https://sci-guide.greensoftware.foundation/R)
+The [Software Carbon Intensity (SCI) specification][1] by the [Green Software Foundation](https://greensoftware.foundation/) is a method for **scoring** a software system based on the components that emit carbon.
+
+The SCI can be used to reduce the total carbon footprint of software. However it is a _rate_ of carbon emissions for software and not necessarily the total carbon footprint.
+
+The top-level formula of the SCI is the following:
+
+> SCI = ([Energy (E)][2] * [Emissions Factor (I)][3]) + [Embodied Emissions (M)][4] per [Functional Unit (R)][5]
 
 ## Energy (E)
 
-TBC
+Energy (E) represents the operational energy consumed by the physical hardware that the software system operates on. More info in the [SCI Guide][2].
+
+> Unit: kilowatt hours (kWh)
+
+### Runtime energy
+
+This project surfaces runtime energy consumption through [Kepler ( (Kubernetes-based Efficient Power Level Exporter)](https://github.com/sustainable-computing-io/kepler).
+
+Kepler deploys a Kepler Exporter which runs as a Daemonset in the cluster. The Kepler Exporter scrapes energy metrics and exports them to Prometheus.
+
+The metric chosen to calculate the energy consumption of Falco is [`kepler_container_joules_total (Counter)`](https://sustainable-computing.io/design/metrics/):
+
+> This metric is the aggregated package/socket energy consumption of CPU, dram, gpus, and other host components for a given container. Each component has individual metrics which are detailed next in this document.
+
+In the [SCI dashboard](https://github.com/cncf-tags/green-reviews-tooling/blob/3a6266ceae99f40aaa367174ffb899385caf1d50/clusters/base/falco-sci.yaml#L505), the joules total is then converted to kWh using a hidden [dashboard variable](https://grafana.com/docs/grafana/latest/dashboards/variables/) `$watt_per_second_to_kWh`. This standard unit conversion metric is equal to `0.000000277777777777778`.
 
 ## Energy Carbon Intensity (I)
 
+> Unit: carbon per kilowatt hours (gCO2eq/kWh)
+
 TBC
 
 ## Embodied (M)
 
-Embodied carbon (also known as embedded carbon) is the amount of carbon emitted during the creation and disposal of a hardware device.
+Embodied carbon (also known as embedded carbon) is the amount of carbon emitted during the creation and disposal of a hardware device. More info in the [SCI Guide][4].
+
+> Unit: grams of carbon (gCO2eq)
 
 M = TE * (TiR/EL) * RS
 
@@ -21,16 +45,14 @@ M = TE * (TiR/EL) * RS
 - EL = Expected Lifespan; the anticipated time that the equipment will be installed.
 - RS = Resource-share; the share of the total available resources of the hardware reserved for use by the software.
 
-More info [here](https://sci-guide.greensoftware.foundation/M).
-
-- TE we use the [Boavizta API](https://doc.api.boavizta.org/) passing the server spec published by Equinix Metal 
+- TE we use the [Boavizta API](https://doc.api.boavizta.org/) passing the server spec published by Equinix Metal
 - EL we use 4 years (35,040 hours) which is the value recommended by GSF
 - TiR is 15 minutes (the duration of the green review)
 - RS is 1 (we use bare metal servers so 100% of the resources are allocated to the software)
 
 The Boavizta API uses data published by the manufacturers. You can read about their methodology in this [blog post](https://www.boavizta.org/en/blog/empreinte-de-la-fabrication-d-un-serveur).
 
-### M Per Instance Type 
+### M Per Instance Type
 
 | Instance Type	| TE (kgCO2eq) | TiR (minutes) | EL (years) | M (gCO2eq) |
 |---------------|--------------|---------------|------------|------------|
@@ -52,3 +74,10 @@ CPU: Intel Xeon E-2378G [datasheet](https://www.intel.com/content/www/us/en/prod
 ## Functional Unit (R)
 
 TBC
+
+<!-- Sources -->
+[1]: https://sci.greensoftware.foundation/
+[2]: https://sci-guide.greensoftware.foundation/E
+[3]: https://sci-guide.greensoftware.foundation/I
+[4]: https://sci-guide.greensoftware.foundation/M
+[5]: https://sci-guide.greensoftware.foundation/R