1 Introduction
3
This is a high amount of energy! Equipping a roof with 1 m
2 of 20% efficient panels
allows you to drive a car, with an electric engine, 1800 km annually, as far as 159 litres
of petrol does for a typical combustion-engine car.
Indeed, a simple back-of-the-envelope calculation shows that for most industrialized countries in the world, the available roof surfaces could already provide for
a significant fraction, in the range of 30–100%, of the electricity needs, if covered
with PV
1 .
As a case study, we can consider the small (40,000 km
2 ) and densely populated
country of Switzerland (8.5 million people). A recent study [1] shows that the current energy system, which is based on 75% of energy from fossil fuels, could be
almost entirely decarbonised by installing 50 GW p of PV panels. This is less than
the potential surfaces available on roofs and façades (see an example of a façade in
Fig. 1.2b)—they have an estimated potential of ~70 GW p . This massive penetration
of PV should be accompanied by curtailment of PV production at certain times in
the year; it would take place simultaneously with the following steps: (a) a shift to
electro-mobility; (b) an improved thermal isolation of all buildings: (c) a widespread
employment of heat pumps for the heating of most buildings. Thereby, a large part of
the fossil energy presently used could be totally suppressed. Hydroelectric power and
electric cars could, in such a scenario, provide most of the required system flexibility.
The World’s global electricity consumption was, in 2018, totally ~22,000 TWh
(1 TWh = 1 Terawatt hour = 1000 GWh). The current total world energy demand of
~160,000 TWh, largely based on fossil energy, could be reduced, thanks to the gain
in efficiency if one switches to energy systems based on electricity. Hence, going
to a zero-carbon society could be technically done by installing 50–60 TW p of PV,
assuming a gain by a factor 3 in energy efficiency—by switching e.g., from fossil fuel
cars to electric cars, from direct fossil fuel heating to heat pumps. If photovoltaics
is to cover around 2/3 of the renewable energy required by 2050 with around 34
TW p , over 1000 GW p (or 1 TW p ) of new PV panels should be installed in average
every year until 2050 [2]. This means increasing—by at least a factor 10—the current
a)
b)
Fig. 1.2 a Large 43 MW p solar farm at Starokazache (Ukrainia); b Solar screen with bifacial silicon
heterojunction solar cells on the façade of CSEM (Switzerland)
1 Another alternative to harness the sun’s abundant energy is biomass, but the area required to grow
these crops is much larger than for PV, because it is a factor 20–100 times less efficient in terms of
final energy and would require surfaces which are simply not available.
3
This is a high amount of energy! Equipping a roof with 1 m
2 of 20% efficient panels
allows you to drive a car, with an electric engine, 1800 km annually, as far as 159 litres
of petrol does for a typical combustion-engine car.
Indeed, a simple back-of-the-envelope calculation shows that for most industrialized countries in the world, the available roof surfaces could already provide for
a significant fraction, in the range of 30–100%, of the electricity needs, if covered
with PV
1 .
As a case study, we can consider the small (40,000 km
2 ) and densely populated
country of Switzerland (8.5 million people). A recent study [1] shows that the current energy system, which is based on 75% of energy from fossil fuels, could be
almost entirely decarbonised by installing 50 GW p of PV panels. This is less than
the potential surfaces available on roofs and façades (see an example of a façade in
Fig. 1.2b)—they have an estimated potential of ~70 GW p . This massive penetration
of PV should be accompanied by curtailment of PV production at certain times in
the year; it would take place simultaneously with the following steps: (a) a shift to
electro-mobility; (b) an improved thermal isolation of all buildings: (c) a widespread
employment of heat pumps for the heating of most buildings. Thereby, a large part of
the fossil energy presently used could be totally suppressed. Hydroelectric power and
electric cars could, in such a scenario, provide most of the required system flexibility.
The World’s global electricity consumption was, in 2018, totally ~22,000 TWh
(1 TWh = 1 Terawatt hour = 1000 GWh). The current total world energy demand of
~160,000 TWh, largely based on fossil energy, could be reduced, thanks to the gain
in efficiency if one switches to energy systems based on electricity. Hence, going
to a zero-carbon society could be technically done by installing 50–60 TW p of PV,
assuming a gain by a factor 3 in energy efficiency—by switching e.g., from fossil fuel
cars to electric cars, from direct fossil fuel heating to heat pumps. If photovoltaics
is to cover around 2/3 of the renewable energy required by 2050 with around 34
TW p , over 1000 GW p (or 1 TW p ) of new PV panels should be installed in average
every year until 2050 [2]. This means increasing—by at least a factor 10—the current
a)
b)
Fig. 1.2 a Large 43 MW p solar farm at Starokazache (Ukrainia); b Solar screen with bifacial silicon
heterojunction solar cells on the façade of CSEM (Switzerland)
1 Another alternative to harness the sun’s abundant energy is biomass, but the area required to grow
these crops is much larger than for PV, because it is a factor 20–100 times less efficient in terms of
final energy and would require surfaces which are simply not available.