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We outline a suitable energy transition roadmap for Italy, in which the whole energy demand is met by electricity generated by low-cost renewable energy technologies, namely solar photovoltaic, wind and hydroelectric power, along with the highly sustainable solar thermal technology to generate low temperature heat. We assess the amount of extra power and storage capacity to be installed along with costs, return on investment and payback time.
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Cite this study: arXiv:1609.08380 [physics.soc-ph]
Italy 100% Renewable: A Suitable Energy Transition Roadmap
Francesco Meneguzzo,*[a] Rosaria Ciriminna,[b] Lorenzo Albanese,[a] Mario Pagliaro*[b]
This article is dedicated to Professor Vaclav Smil for all he has done to advance the understanding of energy transitions
Abstract: We outline a suitable energy transition roadmap for Italy,
in which the whole energy demand is met by electricity generated by
low-cost renewable energy technologies, namely solar photovoltaic,
wind and hydroelectric power, along with the highly sustainable solar
thermal technology to generate low temperature heat. We assess
the amount of extra power and storage capacity to be installed along
with costs, return on investment and payback time.
Keywords: 100% renewable; solar energy; wind energy; energy
transition; energy storage
1. Introduction
The dramatic increase of renewable energy generation across
the world which occurred in the last decade has been so
significant and rapid that, for short periods of time, the electricity
demand of whole industrial countries has been temporarily met
by means of renewable energy, notably wind, hydro and
photovoltaic power. For instance, as of May 15, 2016 (a Sunday)
at 2 pm local time when demand in Germany was 45.8 GW
renewable energies covered around 82% of power demand [1].
Since about 2008, scholars [2], energy analysts [3] and
environmental groups [4] started to investigate the feasibility of
a full transition from fossil to renewable energy. A radical energy
transition scenario was proposed by Jacobson and Delucchi in
2009 by investigating the feasibility of a global transition by 2030
to energy systems powered exclusively by wind, water and
sunlight [5].
The team calculated that to supply the world with 100%
renewable energy (electricity and electrolytic hydrogen) would
require 3.8 million 5-MW wind turbines, 40,000 300-MW central
solar plants, 40,000 300-MW solar PV plants, 1.7 billion 3-kW
rooftop PV installations, 5,350 100-MW geothermal plants, 270
new 1.3-GW hydro stations, 720,000 0.75-MW wave devices,
and 490,000 1-MW tidal turbines.
Smil has lately remarked the scope of such a transition noting
that, according to this scenario, in just fifteen years the overall
installed capacities would have to increase 30-fold for wind, 100-
fold for geothermal power and 500-fold for tidal power, with
40,000 new large (300 MW) PV plants and nearly 50,000 new
concentrated solar power (CSP) plants, as well as more than
700,000 wave-conversion projects [6].
For decades, critics of renewable energy lamented their
unsustainably high cost [7]. Since the early 2000s, however,
photovoltaic [8] and wind energy are experiencing a largely
unexpected global growth (303 GW of solar PV [9] and 486.8
GW of wind power [10] installed across the world by 2016),
which has led the cost of clean electricity to such low levels to
go below that of electricity obtained by burning coal ($2.3c/kWh
in a in an auction by Abu Dhabi for a 350 MW solar plant as of
September 2016 [11]).
A similar trend has occurred for the commonly neglected solar
thermal technology, with solar heating contribution in meeting
global energy demand second only to wind power among
renewable energy sources (341 TWh of energy supplied in 2014
mainly as hot water vs. 200 TWh of electricity supplied by PV
modules across the world) [12].
Critics of renewable energy today preferably advocate the “much
lower quality [13] of renewable energy whose intermittent
nature would pose insurmountable economic problems to the
grid reliability. For example, while convening that it would be
technically possible to meet total electricity demand from
renewable energy sources, Trainer argues that this would be
unaffordable due to the amount of redundant plants needed to
cope with intermittency [14].
However, wind and solar energy complement each other on
intraday and seasonal scales (continental wind energy tends to
peak at night, solar during the day, while the wind blows during
winter and stormy days when solar modules produce little
The higher the number of wind turbines and solar panels
connected to the grid, and the more geographically distributed
across a territory, the less volatile is the combined output of all
individual generators, smoothing out renewable energy
fluctuations on a second-by-second basis [15].
Neither Germany, nor Spain or Italy, for example, faced
particular grid problems when a large amount of solar PV and
wind power was installed in the 2005-2015 decade, even though
significant investments in the grid were deployed.
In this study, we evaluate the full transition of Italy to renewable
energy by 2050. We adopt a realistic approach, which starts
from the awareness that production, installation, and
maintenance of wind turbines and PV modules “remains critically
dependent on specific fossil energies” [16]; and that, so far, the
fastest historical sector-specific energy transitions observed was
30 years, though energy transitions have taken much longer [17].
The outcomes of this work will be useful to policy makers and
energy stakeholders called by energy and environmental
urgencies to accelerate the transition to renewable energy.
[a] Dr F. Meneguzzo, Dr L. Albanese
Istituto di Biometeorologia, CNR
via G. Caproni 8
45045 Firenze (Italy)
[b] Dr R. Ciriminna, Dr M. Pagliaro
Istituto per lo Studio dei Materiali Nanostrutturati, CNR
via U. La Malfa 153
90146 Palermo (Italy)
Cite this study: arXiv:1609.08380 [physics.soc-ph]
2. Current Scenario
The set of data and their respective sources listed in Table 1
include the relevant information about the Italian energy system.
Table 1. Italy's energy datasets and sources
Period and
Energy consumption by sourcea
BP [17]
Power capacity by source (excl.
Hydroelectric capacity by type
GSE [18]
Electricity consumption
Terna [19]
Intermittent generation from RES,
by source
Terna [20]
Oil consumption for transportation
MISE [21]
aThe electricity consumption in units of TWh is converted into primary energy
in units of MTOE after accounting for an average thermoelectric efficiency
factor equal to 0.38, as well as for the average oil energy content equal to 11.6
Figure 1. Total energy consumption by source in Italy, during 1960-2015.
Figure 1 shows that the total energy consumption (TEC) in Italy
has dropped as much as 18% in the period 2005-2015 (from
185.6 to 151.7 MTOE). Followed by coal, reduction in oil and
natural gas use was particularly pronounced. Such reduction
was only partially compensated by a relevant increase of
renewable energy sources (RES), mainly wind and solar PV.
The share of RES (Figure 2) over TEC has quickly risen from a
fairly stable 6% until 2007-2008, to over 18% in 2014, while
dropping to slightly above 16% in 2015 due to climate-
dependent reduction of hydroelectric output.
Remarkably, these figures match the binding requirements laid
down by the European Directive 2009/28/EC of the European
Parliament and of the Council of 23 April 2009 on the promotion
of the use of energy from renewable sources [22], according to
which in Italy 17% of gross end energy consumption in 2020
should be met by renewable energy sources.
Figure 2. Renewable energy generation partitioned into hydroelectricity and
other sources, along with its share of total energy consumption, in Italy, during
In practice, the whole increase of RES generation was produced
by sources other than hydroelectric power. Since 1999, the wind
source has steadily increased, totaling as much as 9,000 MW
(Figure 3), while the solar PV source has steeply risen from
practically zero MW in 2007 to 19,000 MW in 2015, with most of
the increase (+16,000 MW) during 2008-2012, and more
specifically in 2011 and 2012, when Italy's photovoltaic capacity
grew by about 15 GW and onshore wind by about 4 GW [6]. In
the same period, the capacity of hydroelectric power increased
by 2,000 MW; and that of geothermal power by 150 MW only.
At the end of 2013, Italy had an installed 18.5 GW of PV
(+18.500 MW from 2005) and 8.4 GW of wind (+7.000 MW from
2005) power, with most renewable energy plants in the South,
far from large electricity consumers [23]. Concomitantly, the
electricity demand declined from the 2007 peak (340 TWh) to
318 TWh in 2013, i.e. even lower than the 2003 level (321 TWh).
Together, the boom in RES generation and the decline in
demand brought the equivalent hours of natural gas power
plants in operation from 5,100 of 2006 to 2,100 as of 2013 (-
60%) [23]. In 2014 Italy's incumbent generator announced the
decommissioning of 13 GW of thermal capacity within five years
(of which it has decommissioned 8 GW to date, starting from the
coal-fired station near Venice).
Figure 3 shows that the whole increase of hydroelectric capacity
in 1999-2015 was due to new off-river hydroelectric plants,
which are unable to store electricity generated by intermittent
sources, while the capacity of reservoir installations (more than
400 hours of storage) and basins (2-400 hours) has been fairly
Cite this study: arXiv:1609.08380 [physics.soc-ph]
Figure 3. Power capacity of renewable energy sources in Italy, during 1999-
The hourly series of power generation from renewable sources,
along with the overall electricity consumption series during
November 2014 - October 2015 (Figure 4) shows that, as
expected, the wind and solar PV generation was significantly
more variable than the geothermal and hydroelectric generation,
though the respective shares of year-round RES generation
were not much different (HYDRO generation = 55 TWh;
WIND+PV generation = 41 TWh).
The latter figures account for 17.5% and 13%, respectively, of
the overall electricity consumption in the same period (315 TWh).
Figure 4. Hourly series of RES generation and electricity consumption in Italy,
during November 2014 to October 2015.
Back to total energy consumption, Figure 5 shows that, in Italy,
electricity accounts for almost half of the TEC.
Figure 5. Breakdown of total energy consumption into energy end use in Italy,
(Nov 2014-Oct 2015). Heating is powered by fossil fuels.
3. 100% Renewable Energy Scenario
The transition to full renewable energy generally requires the
electrification of energy end uses [24], particularly of heating and
transport needs, which are currently met by burning fossil fuels.
In a recent work aimed at promoting a rapid transition to 100%
clean, renewable energy [25], Jacobson and co-workers assume
that Italy, under the renewable-only electricity scenario, would
achieve about 34% reduction in end-use power demand due to
the much higher efficiency of electric motors over the internal
combustion engine; as well as of electric heating with heat
pumps and the elimination of energy use for the upstream
mining, transport, and/or refining of fossil and biomass fuels.
Although the latter is a reasonable hypothesis, guided by the
realistic approach mentioned above, in this work we have
chosen to assess the power needs deriving from each kind of
broad end use direct use of electricity, heating and
transportation that sum up to provide the overall figure for the
whole Italian electricity demand to be covered by RES as such.
To convert the current total energy consumption in Italy into
electricity, the average efficiency from fossil fuel heating
installations was prudentially assumed equal to as much as 90%.
The structure of the distributed electric heating infrastructure
was assumed to derive from a 50% heating demand concerning
high-temperature heat requiring electric resistances whose
efficiency can be assumed again around 90% - and the other
50% concerning low temperature (<100°C) heat, which can be
matched by air-source heat pumps (ASHP). Again, such
partition can be regarded as quite conservative, since residential
heating is likely to share more than 50% of the overall demand.
ASHPs are assigned an average coefficient of performance
(COP) of 4, i.e. the ratio between the quantity of heat transferred
to the heat sink (useful energy output) and the input electric
power, which is typical of relatively mild Italian climate [26].
Cite this study: arXiv:1609.08380 [physics.soc-ph]
While ground-source heat pumps generally enjoy higher values
of the COP than ASHPs [27], their higher capital costs and less
general applicability lead us to select air-source heat pumps as
the reference electric low-temperature heating technology.
On the basis of the above assumptions, the current heating
portion of the overall energy consumption (43 MTOE) is first
partitioned into high-temperature heating (21.5 MTOE). Due to
the assumed efficiency, the latter is simply multiplied by the oil
energy content (11.6 kWh/kg), resulting in an electric
consumption equal to 251 TWh.
The remaining portion of the current heating demand (again 21.5
MTOE), matched by air-source heat pumps, is multiplied by the
efficiency of fossil fuel heating installations (90%), then divided
by the assumed average COP of the ASHPs (4), and finally
multiplied by the oil energy content (11.6 kWh/kg), resulting in
additional 57 TWh. Overall, the above provides an additional
electric consumption due to heating requirements equaling 308
Concerning replacement of oil-based transportation, the current
equivalent oil energy content is multiplied by the ratio of the
average efficiencies of internal combustion engines and electric
vehicles (20% and 80%, respectively) [28], resulting in 107 TWh.
Hence, the total electricity consumption including current
electricity consumption (315 TWh in 2015) to be matched would
amount to 730 TWh, i.e. about 2.3 times the current electric
demand. Additional demand for heating purposes would share
42%, while additional demand for transportation would follow
with 15%.
Unless a country or region has access to suitable energy
storage such as large capacity pumped hydroelectric power,
balancing and variability are the main problems to address with
intermittent renewable energy sources [29].
As mentioned above, a fairly large storage for intermittent wind
and solar PV generation is already in place in Italy, based upon
the residual capacity of reservoir and basin hydroelectric plants.
In order to compute such residual capacity, we assume that that
no other storage system is available and that 400 h is the
average storage time available for the whole set of the plants
under consideration.
Thus, we calculate the amount of extra wind and PV energy that
can be generated and stored as hydroelectric power in this
residual capacity before being conveyed to the grid.
Figure 6 shows one of the possible outcomes, with wind
capacity around 18,000 MW, i.e. about double the current value,
and solar PV capacity around 30,000 MW, i.e. about 1.6 times
higher than the current value.
Figure 6. Determination of upper bounds for wind and solar PV capacity
whose overall generation matches the hydroelectric residual capacity in Italy,
during November 2014 to October 2015.
The yearly electricity generation from the wind and solar PV
sources combined would then increase to 62 TWh (about 1.5
times over the current output), and its share of current electricity
consumption from 13% to about 20%. The sum of the wind and
solar PV generation after hydroelectric storage (62 TWh), the
current hydroelectric (about 49 TWh) and geothermal (ca. 6
TWh), results in about 117 TWh, i.e. 16% of the projected total
energy consumption in the 100% electric and renewable
Although in principle a further increase of the hydroelectric
capacity with storage capabilities (reservoir and basin plants)
cannot be ruled out, it is unlikely to be sufficient to meet the
storage requirements due to the very large additional wind and
solar PV generation needed to match the projected total energy
(all electricity) consumption.
Figure 7. Partition of the renewable electric generation matching the overall
consumption under the 100% electric and renewable scenario in Italy,
simulated during November 2014 to October 2015.
Figure 7 shows the real (observed) electric consumption series
and the simulated structure of the hourly renewable electricity
generation for the same period under consideration in this study
Cite this study: arXiv:1609.08380 [physics.soc-ph]
(November 2014 to October 2015) matching the required total
electricity consumption. For the sake of simplicity, the annual
value of 730 TWh is evenly distributed across 8,760 hours,
resulting in an hourly demand equal to about 83,000 MWh.
Notwithstanding that at least a fraction of such additional
intermittent generation could skip the storage, due to the chance
of delivering any excess generation via cross-border
interconnections, as in fact it is already occurring [30], for the
purpose of this study it is assumed that the whole WIND+PV
generation must be stored.
The hydroelectric generation after the storage of the intermittent
PV+WIND generation, is partitioned in its turn into storage
shown in Figure 6 and additional storage in hydroelectric basins
and reservoirs up to saturation of the respective residual
capacity, as shown at the bottom of Figure 7.
The chart includes PV+WIND generation after its storage
elsewhere (for example, in batteries, stationary or onboard
electric vehicles), as well as the geothermal and hydroelectric
generation observed during the period. All such generation
components match the required electricity consumption every
Under this scenario, the solar PV and wind capacities should be
respectively increased up to about 315 GW (16 times more than
current capacity) and 190 GW (21 times higher than current
capacity), their combined annual generation would reach about
640 TWh (370 TWh from PV, 270 TWh from WIND), out of
which more than 550 TWh should be stored elsewhere than in
currently available hydroelectric basins and reservoirs,
averaging more than 65,000 MWh every hour.
The first outcome of the above analysis concerns the surface
requirements (land + building surface) needed for the new solar
PV installations as well as the power and number of new wind
towers and farms. According to 2002 estimates by the
International Energy Agency, with appropriate rooftops and
facades covered with commercial solar cells (763,53 km2 of
rooftop and 286,32 km2 of facade surface available in 2002, and
since then further grown), the potential annual energy production
in Italy is 126 TWh [31].
This suggests that only through building integrated photovoltaics,
40% of Italy’s current electricity demand, as well as 34% of the
respective target generation in the 100% electric and renewable
scenario (370 TWh), can be met with country-wide BIPV
To understand the scope of the transition required to achieve
fully distributed and renewable generation, at the end of 2013,
when the installed PV power in Italy was 17,429 MW, out of the
20.3 TWh of solar electricity produced, 80% was fed into the grid
and 20% was consumed locally [32].
Large penetration of renewable energy in Italy too has deeply
affected the electricity market, consistently lowering its price and
the way pricing is structured [33].
Perez and co-workers have lately shown that achieving very
high PV penetration and the displacement of conventional power
generation will require an effective electricity remuneration
framework in which customers are alerted to take advantage of
low-cost electricity when there is a surplus.
This, in its turn, hints to an essential role of the grid operator in
balancing the total amount of renewable generation with the rest
of the grid [34].
The second and even more important outcome of the present
analysis, indeed, concerns the immense capacity needed to
store about 550 TWh of additional PV+WIND generation: where
all this energy will be stored whereas currently, as put it by
Pickard, virtually none of the needed bulk storage capacity
exists today [35]?
4. The New role of Biomass and Solar Thermal
The issue facing policy makers is to identify as soon as possible
the efficient and economically viable energy storage
technologies on which to invest, in order to have them ready
when, at the best in about 50 years or more likely in 10 to 20
years [36], the supply of fossil fuels will have become scarce
and thus most countries will have to run on 100% renewable
Storage, indeed, was the main obstacle identified also by
Jacobson and co-workers who recently attempted to solve the
related grid reliability problem with 100% penetration of
intermittent wind, water, and solar for all purposes in the US, by
avoiding expensive chemical battery technology and assuming
energy storage of heat in the soil (Underground Thermal Energy
Storage) and water, cold in water and ice, and electricity in
hydrogen, phase-change materials, and hydropower [37].
Exploring the possibility of having Britain entirely powered by
solar PV energy, MacKay, for example, has recently
emphasized that 16,000 kg of batteries per person out of 60
million people comprising the UK population would be needed to
store the electrical energy consumed throughout the wintertime
(battery density = 100!Wh/kg; roughly 100 days of 40 GW
average demand, i.e. 2356!h×40!GW) [38].
The other major point concerns clean transport technology,
which has been hampered for decades by the obsolescence of
the battery technology. Things started to change with the advent
of state of the art lithium-ion batteries, whose energy density
already of about 200!Wh kg-1 is improving while cost is falling
more rapidly than expected, with prices declining by about 14%
per year since 2007 in a standard learning curve effect of 6% to
9% reduction in price for every doubling of production volume
Li-ion batteries built with recyclability in mind will play, we argue
herein, a significant role to store solar PV energy in stationary
buildings, as it is already happening with hundreds of inverter
manufacturers selling inverters equipped with Li-ion battery
packs capable to store from a few to several kWh.
Cite this study: arXiv:1609.08380 [physics.soc-ph]
With cars being produced at 80 million year-1 rate, each needing
about 10 kg of lithium, this will simply not be the case as
reserves of fossil lithium amount to 13.5 million tons [40],
enough to sustain less than a 17-year supply (13.5 tons/800,000
tons year-1 = 16.9 years).
Put simply, we will not replace fossil, finite resource such as coal,
oil and natural gas with another fossil, finite resource; but rather
with a renewable energy storage substance such as low cost
and abundant renewable hydrogen obtained from evenly
distributed biomass in which hydrogen is stored in safe and
easily handled polysaccharides with a striking ~5000 Wh/kg
energy density [41].
Indeed, although global efficiency of plant photosynthesis is
merely 0.2%, the global primary biomass production is
approximately five times the world's energy consumption [42].
Zhang and his teams in USA and China have advanced scalable
cell-free enzyme-based catalysis technology through which the
whole hydrogen content of cellulosic biomass is extracted from
lignocellulosic agricultural waste.
The technology is rapidly progressing. It will be first
commercialized in China in the synthesis of valued bio-based
products (vitamin B8 and synthetic starch) [43], and then of
amylose to be used as an easily handled solar fuel. While
formidable standardisation, industrialisation and upscaling
efforts would be needed in front of the immense storage
requirements mentioned in this and in related works, this
emerging technology appears one of the few viable alternatives.
In order to alleviate the burden represented by the additional
electric demand for heating purposes (308 TWh, or 42% of the
overall consumption), the so far severely underexploited solar
thermal (ST) technology should play a new and far more
significant role in Italy's energy future. By the end of 2013, the
total installed capacity of glazed collectors (flat plates and
evacuated tubes) in Italy amounted to 3,650,000 m2 of collector
area, corresponding to 2.555 GWth, with around 200 MWth of
newly installed solar thermal capacity [44].
With a net thermal energy, deliverable by a standard ST
installation (2.13 m2 collector surface area), recently assessed
as representative for Italy at the level of 1407 kWhth per year [45],
the overall thermal generation from the ST installations during
the year 2013 can be estimated around 2.4 TWhth, or about 940
MWhth per MWth installed capacity. Compared to the European
solar thermal benchmark of 264 m2 per 1000 inhabitants, in Italy
the national average as of 2014 was still very low (about 50 m2
per 1000 inhabitants, with market in 2014 having fallen by 25%
compared to the previous year at 268,500 m2 newly installed
collector area [46].
A major shift of current heating technologies is urgently required,
with far more solar thermal, geothermal and heat pump
technologies needed in the heating sector, is fully justified by the
current large share of heating (29%) in final energy demand, as
shown in Figure 5.
Today’s solar thermal technology using evacuated tubes (the
most efficient), or flat glazed panels (second best) is perfectly
suited to provide low temperature heat (<100°C) not only for hot
water delivery but also for space heating, hot water and air
conditioning (solar combi+ systems), a condition that in the
Mediterranean area has been identified as crucial if solar
thermal is to contribute significantly to the long-term heating and
cooling demand in the European Union [47].
Hence, given its very high potential for further deployment in
Italy (and elsewhere), a fourfold increase of capacity and low
temperature heat generation from the ST technology in order to
achieve the European solar thermal benchmark can be
reasonably assumed. This would contribute at least additional 7
TWhth that, in turn, converted into electricity demand by heat
pumps (COP=4), would alleviate the yearly overall electric
burden of the 100% electric and renewable scenario by only
about 2 TWh.
If, however, coherently with the approach of this study, we
assume that the increase of ST capacity parallels the PV one, i.e.
16 times the current figure to about 46 GWth (after assuming a
300 MWth capacity increase since end of 2013 to mid-2015), that
would contribute about additional 40 TWhth in the form of low
temperature heat that, in turn, converted into electricity demand
by heat pumps, would alleviate the yearly overall electric burden
of the 100% electric and renewable scenario by a more relevant
amount of 10 TWh, namely by 1.4%.
While the latter figure is not so large in the framework of the new
scenario, and while it does not change significantly the 550 TWh
estimate for the additional PV+HYDRO generation, it would
mean about 1 m2 of solar collector area per inhabitant: a
threshold difficult to overcome in the realistic approach adopted
in this study.
5. Economic Analysis
Significant investments in additional renewable capacity
comprised of overall 300 GW of PV power and 180 GW of wind
power is required, along with key electricity grid and storage
The estimated capital costs for this scenario using current full
installation costs (1/W for PV [48], 1.3/W for wind power [49])
amounts to about 530 billion for energy generation, even
though the actual cost will be significantly lower due to rapidly
declining prices for both solar modules, wind turbines and
Balance of Systems components.
Computing from 2017, therefore, the average additional
investment needed in renewables until 2050 would be about 16
billion a year (current money). The additional costs for
refurbishing and replacing the installations after 2050 are
deliberately omitted under the assumption that the savings
produced in the electricity bill will compensate such costs [33].
Cite this study: arXiv:1609.08380 [physics.soc-ph]
The eminent role of PV energy, much bigger than wind, is
justified by the very low cost of the technology, with 2017 prices
of PV modules having already approached the $0.30/W
threshold [50]. In addition, we do not differentiate between three
different types of PV (residential, commercial and utility), as the
latter differentiation is largely academic.
A recent study [51] outlining three energy scenarios aimed at
reducing emissions in 2050 by 80% compared to emissions in
1990, concluded that the most technically feasible pathway to
decarbonize the Italian energy system would rest on deploying
solar and wind technologies, a significant contribution from
biomass generation, a moderate but critical role for carbon
dioxide sequestration, accompanied by the deployment of more
efficient technologies in a number of industrial sectors within the
Italian economy, as well as in transport and residential energy
We also ascribe a significant role to biomass, yet in an
advanced scenario in which biomass is not merely burned to
generate electricity or make first-generation biofuels, but rather
used as an abundant source of valued hydrogen using the multi-
enzyme technology proposed by Zhang and co-workers [41].
Based on recent estimates, the cost of carbohydrate (amylose)
produced at industrial maturity could level around $0.3/kg
(0.25/kg at the present exchange rate) or lower [43].
Assuming the specific gravimetric energy content of amylose at
about 17 MJ/kg, i.e. 4.7 kWh/kg, a rough estimate around 29
billion (current money) can be derived for the cost of storage of
550 TWh of additional PV+WIND generation not storable in
hydroelectric basins and reservoirs. Further assuming a linear
increase of additional PV+WIND capacity during 2017-2050, the
overall cost for storage during the same 34-years period would
amount to about 500 billion, bringing the overall economic cost
of transition towards 1 trillion.
In year 2015, the Italian energy bill (oil, natural gas, coal and
other solid fuels, net electricity import) was about 35 billion, out
of which about 16 billion were due to oil import [52]. Assuming
constant prices for all fuels, as well as the above-mentioned
linear increase of the additional renewable capacity up to the
year 2050, the overall cost avoided by the transition would
amount to about 600 billion.
Therefore, the overall net economic investment needed to
perform the transition to 100% electric and renewable energy
system in Italy would be limited to approximately 400 billion
during the next 34 years, or an average of less than 12 billion
per year.
Afterwards, the main cost will concern the storage (29 billion
per year, in current money), i.e. 6 billion lower than the yearly
fuel savings, leading the pay-back time of the investment to
occur many decades after 2050, as shown in Figure 8.
Figure 8. Economic balance of the proposed energy transition, partitioned into
the cumulated cost of deploying additional PV+WIND capacity, cumulated cost
of storage and cumulated savings of fossil fuels.
Although this may look a relatively long time, it should be
considered that the scenario designed in this study will ensure,
in the short term, a progressive resilience against both price
fluctuations and possible scarcity of fossil fuels, while in not so
long term (between 15 and 30 years) it will be the only
alternative against a likely severe energy shortage.
Moreover, it should be noted that the fuel savings overcome the
cost of deploying additional PV+WIND capacity already in 2046,
or roughly 30 years from the beginning of the proposed
transition: in the meantime, the unit cost of both the additional
renewable capacity and storage technologies are likely to
decrease significantly, leading to a far more attractive economic
6. Outlook and Conclusions
We outline a realistic energy transition roadmap for Italy in which
the whole energy demand by 2050 is met by electricity
generated by low cost renewable sources, mainly solar
photovoltaic, wind, and hydroelectric, along with the industrially
mature, highly sustainable solar thermal technology.
It should be understood that the transition demands to invest for
many years to come a significant part of currently available fossil
fuels in producing wind turbines, photovoltaic modules, solar
collectors, heat pumps, metal wires, concrete, batteries and
bioenergy plants to meet the energy demands of modern
Along with the electrification of virtually all energy end-uses and
the transition to heat pumps as the standard technology
covering the generation of low temperature heat, the analysis
identifies large electricity storage requirements that, in our
viewpoint, will be met by a technology mix in which biomass will
play a pivotal role.
Cite this study: arXiv:1609.08380 [physics.soc-ph]
The study deliberately omits from consideration the
technological solution to balance the generation and demand via
interconnection between the Italian and European electricity
networks, importing electricity when generation is lower than
demand and exporting surplus electricity when generation is
greater than demand, as it actually happens in Italy since
In lieu of interconnectedness, the key energy balance issue is
addressed employing pump storage along with second-
generation biomass utilization via enzyme-based technology to
store any electricity surplus into energy dense carbohydrates
fixing the CO2 extracted from the atmosphere. In addition,
consumer behavior towards electricity usage will help reduce the
amount of balancing required, which in its turn requires
reshaping the market structure.
In brief, policy makers of forthcoming Italy’s Governments
elected by people ever more concerned about declining
resources, environmental crisis and climate change, will
eventually adopt wise energy policies capable to govern the
required energy transition towards a fully renewable energy
Although costly, in the end there are no other viable alternatives
to face the wealth-energy-population conundrum also in Italy.
The figures and the realistic approach devised in this study will
hopefully provide guidance in building such new policies, in
which fundamental and industrial research for ever more
efficient, reliable and cheap power generation and storage
technologies will play a pivotal role.
List of abbreviations
BP = British Petroleum
GEO = Geothermal power
GSE = Italian Manager of Energy Services
MISE = Italian Ministry for Economic Development
MTOE = Million Tons of Oil Equivalent
MJ = Megajoule
MW = Megawatt
MWh = Megawatt hour
PV = Photovoltaic
RES = Renewable Energy Sources
TWh = Terawatt hour
WIND = Wind
Thanks to Professors Yi-Heng Percival Zhang, Virginia Tech and
Tianjin Institute of Industrial Biotechnology, Richard Perez,
University at Albany, State University of New York, Tomas
Kåberger, Chalmers University of Technology, Mark Z.
Jacobson, Stanford University, and Derek Abbott, University of
Adelaide, for helpful discussion.
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