Estimation of avoided CO2 emissions

The amount of CO2 emissions avoided is proportional to the quantity of PV electricity produced. For the estimation of CO2 emission avoided (Figure 3) we considered that the electricity produced in the schools by the PV systems will be equal in value to the reduction of electricity produced by the Portuguese energy mix. In the Portuguese energy mix 1.2kg of CO2 is emitted per koe of primary energy consumed [7]. The conversion factor between primary energy and electricity is

0. 290 koe of primary energy per kWh of electricity [2]. Therefore, the CO2 emitted is given by:

CO2 emitted [kg/kWh]=1.2[kg/koe] x 0.290 [koe/kWh] =0.35 kg of CO2/kWh (1)

In this estimation, the CO2 emissions due the PV system assembling, manufacturing, and maintenance were neglected.

The CO2 emission trading market is not very stable yet. Still, in the future it will also be relevant to approach CO2 as a financial application. For this estimate we used a reference CO2 value of 24€

per ton of CO2 emitted. In the present case the total emission certificate value is 170-260 K€/year, see Figure 6.

Figure 6 — CO2 emission avoided (in blue) and their financial value (in grey)

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Using data from the International Energy Agency [8] is possible to see that the total PV production at schools will represent 0,06% of the electricity consumption in Portugal, and the CO2 avoided will be about 0,02% of the total Portuguese CO2 emissions.