Page 31 - Impiantistica italiana

duction activities is mainly coming from CO as well While power from shore is a technically mature
2
as methane emissions. While there is still a lot of technology, challenges arise from the fact that
variation between the various regions of the world renewable energy sources are non-dispatcha-
(max and min values in 2021 vary from 193 to 64), ble. Moreover, electrification is attractive in geo-
in average two are the main sources of GHG emis- graphies where distances from land (i.e. the cost
sions, accounting for more than 80% of 2021 data: of interconnection), the abundance of renewable
• fuel combustion and energy use, with 63% of energy (i.e. the amount of decarbonized power
shares; that come from the grid) and technology feasibili-
• flaring, with 20% of shares. ty are all favourable. Recent field studies showed
that even in the UK North Sea, significant chal-
Above data are related to both onshore and offsho- lenges remain in the commercial viability of cer-
re fields and cover the entire world geography with tain electrification projects, based on high CA-
assets at different stages of their lifecycle. PEX and direct impacts on the levelized cost of
Looking instead at a specific country like Norway, electricity (LCOE) [3]. In deep waters, according
where the oil and gas production is primarily Of- to a FPSO operator, additional challenges come
fshore and where the industry already started from the need to further develop power cables
adopting lower carbon solutions in a “mature” as- for water depth and the technology limitations
sets base, 85% of sector GHG emissions are co- due to the high voltage power distribution on a
ming from power generation, while flaring activities topside, both in AC and DC configurations.
account for an additional 6,9% (Norwegian Petro- When decarbonizing a FPSO vessel, it was sho-
leum Directorate [2]). wed that there are already technically mature and
economically viable alternatives to “conventional”
Today, many operators are rotating equipment solutions [4]. One of such alter-
taking voluntary steps by natives is leveraging the high thermal power from
gas turbines exhaust [4], [5], [6].
“committing to a reduction in the Traditionally, on a FPSO gas turbines are used to ei-
overall carbon footprint from ther generate electricity (Open Cycle Gas Turbines
- OCGT) or for mechanical drive (i.e. drive pumps
their assets and compressors). Instead, combining the electri-
cal and thermal power needs on a centralized po-
The above numbers therefore demonstrate that wer station allows to exploit the thermal energy of
combustion of fuels remains a priority when loo- the hot exhaust fumes from the gas turbines which
king at ways to decarbonize. Historically, onshore otherwise would be wasted. As a result, a benefit in
power generation has attracted lot of attention [3], terms of increased efficiency and reduced carbon
with the adoption of solutions ranging from increa- emissions is obtained.
sed efficiency, fuel switch (e.g. from coal to natural Today, a number of Combined Cycle or Cogene-
gas), the adoption of nuclear energy and the pro- ration Gas Turbines (CCGT) installations operate
gressive spread of renewables (primarily wind and Offshore in Norway (Oseberg, Eldfisk and Snorre
solar). Onshore, main driver is usually the connec- facilities) and in the Gulf of Mexico (Appomattox).
tion to a larger grid for increased frequency stabi-
lity while the adoption of large/heavy equipment is
generally possible due to relatively no constraints in
footprint and weight.
Moving instead in an Offshore environment, the
context changes drastically:
assets usually work in an island mode, off from the
main land power grid and remote from main land;
• power demand can change very much during
project lifecycle and from day to day, depen-
ding on the platform operating mode;
• main goals are safety and uninterrupted
hydrocarbon production, so local grid stability,
power station availability and reliability are of
paramount importance;
• weight and footprint are very critical since they
affect the overall CAPEX and therefore project
viability.
In recent years, several studies have been deve-
loped with the overall goal to reduce emissions
from power generation Offshore. In Norway in
particular, power from grid (i.e. connection of
an offshore platform via a subsea cable bringing
renewable power) is being increasingly consi-
dered as a solution to decarbonize operations.

Impiantistica Italiana - Maggio-Giugno 2024 27