DC-Coupling ESS Solution Whitepaper
An Analysis on How DC-Coupling ESS Solution
Increases Renewable Energy Ratio
In the past few years, the energy storage
nology - especially the rapid develop -
m u l t i p l e t e c h n o l o g i e s t o i m p ro v e
industry has seen a booming develop-
m e nt o f E V b at te r y te chn o l o g y.
th e fl ex ib ili t y o f a gro w in g p ro p o r-
ment driven by the joint impacts of the
Energy storage is a vital driving factor
tion of renewable energy power
falling LCOE of renewable energy and
to facilitate the energy climate-neutral
s ys tems .
breakthrough of energy storage tech-
transition. It can be combin e d with
Issues and countermeasures
China is one of the world’ s large s t
cially in China’ s northwestern region
more than a dozen provinces including
e n e rg y h u b s . T h e r a p i d g ro w t h o f
where the solar resource is abundant
Shandong, Shanxi, Xinjiang, Inner Mon-
renewable energy spurs the demand for
but cannot be fully utilized. In addition
golia, Anhui and Tibet have successively
flexibility in traditional power plants and
to this, the PV industry is facing with the
issued policies mandating energy stor-
the entire power system. In addition, the
challenges of a lower LCOE and the
age systems (ESS) being added to the
impact of PV volatility on the grid is also
wider range of volatility of output.
renewable energy power plants.
ing installed capacity. The countr y is
I n f a c t , C hi n e s e g o v e r n m e nt s a n d
Coincidentally, Germany sees similar
now witnessing clipping loss, a huge
National Grid have b e gun to s et up
problems in renewable energy develop-
challenge of solar power segment, espe-
requirements on this issue. Since 2020,
ment. The electricity generation in Ger-
scaling up with the substantial increas-
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DC-Coupling ESS Solution Whitepaper
many from November 2019 to August
2020 is shown in Figure 1, where the
volatility of onshore PV can clearly be
seen. Renewable energy accounts for
43% in the national energy mix, and this
proportion is expected to exceed 65% by
2030. By 2050, the power system will be
100% of renewable energy. As one of the
key driving forces in renewables , PV
segment is hiking.
Figure 1: Power Generation and Consumption of Germany (11.2019-08.2020)
In addition to fluctuations in power
as electric vehicles or heat pumps will
Moving for ward, ESS is becoming a
supply, hourly electricity demand also
gradually replace fossil fuel, we see a
widely-recognized solution to the volatility
changes . Therefore, not only power
growing demand on electricity, which
and clipping loss of renewable energy.
supply needs to be predicted, but power
makes the improvement of energy effi-
Especially with the LCOE going down
demand should also be predictable,
ciency a main concern. Therefore, the
continuall y, energ y s torag e w ill b e
ensuring a balance between the supply
regional annual electricity demand and
more accessible and flexible.
and demand. As new technologies such
hourly demand pattern will also update.
Issues and countermeasures
As we are at the cusp of energy transi-
have launched more product portfolios
lowering the LCOE of solar-plus-storage
tion, renewables, such as PV is required
with this function.
installations and maximizing the power
to be more grid-friendly. Energy storage
generation that can be fed into the grid,
is one of the most effective solutions to
There has been experienced track records
energy suppliers and developers are turning
address the issue. Likewise, as the cost
on the DC-coupling solution in a multitude
to DC-coupling solutions.
of PV modules continues to fall, and
of markets covered by market-oriented
batteries follow a similar downward
power transactions, such as Europe, the
Europe witnesses an even evident trend.
trajectory, solar-plus-storage application
US and Japan.
In countries like the UK, the DC-coupling
players. As one of the typical solutions
The US is leading the trend, where electricity
panies. It will help improve overall energy
among the solar-plus-storage markets,
generated by clean energy projects are
output of the hybrid system while also
the DC-coupling solution can maximize
becoming more competitive than gas
optimizing the costs and increasing
the utilization of renewable energy and
plants’ , especially considering other revenue
system reliability and flexibility.
smooth the power output, ensuring a
streams from grid services. Aimed at further
is in growing demand among industry
BESS is under development by local com-
more reliable and stable power landscape.
The DC- coupling solar-plus-stora g e
PV lnverter
PV Module
design means that an energy stor a g e
sy s tem c o nn e c t s to a s o l ar s y s te m
Grid
v ia D C s i d e (a s s h o w n in F i gure 2).
In this s o lu ti o n , a p re - a s s e mb l e d
e n ergy s torage inter f ace of a PV
LC
Battery
DC/DC
inver ter w ill b e ne ce s s ar y. Inver ter
sup p li er s rep re s ente d by Sungrow
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Figure 2: DC-Coupling ESS Solution Diagram
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DC-Coupling ESS Solution Whitepaper
Break through solar bottleneck
In view of the growing PV penetration, the
L ike w i s e , Sun gro w ’ s D C- co up lin g
algorithms. The PV inverter can be used
p o s sibilit y of clipping lo s s will als o
solution has been applied in China a few
for bidirectional charging and discharging
increase. Especially in areas with ample
years ago. Back in 2016, a 100MW PV
applications. Sungrow is one of a few
solar resources, DC-coupling solution is an
p l a nt in J in c h a n g , G a n s u a d o p te d
inverter manufacturers that can provide
ideal match for local decarbonization.
solar-plus-storage solution to solve the
bidirectional charging and discharging
problem of solar electricity clipping loss.
solar-plus-storage solutions.
Amos Liu, a senior technical manager of
A turnkey 1MW/1.1MWh ESS was offered
Sungrow, explained that the DC-coupling
to carry out relevant analysis, accumu-
“DC-coupling system can be used for stor-
system can solve the problems of clipping
late data and experience, and pave the
ing excess energy during the day and
loss and cur tailment. It absorbs the
way for future applications.
continue to meet the electricity demands
surplus electricity generated during the
at night. After that, it can also play a role in
daytime and feeds it to the grid at night or
Notably, Sungrow’ s newly launched
peak-shaving and absorption of wind
when there are dispatching needs. Com-
DC-coupling solution has made innova-
power and multiple energy sources from
pared with the AC-coupling solar-plus-stor-
tions in the power electronics and control
late night to early morning,” said Amos.
age solution, DC-coupling system can be
more profitable. With less restriction on
DC/AC ratio, the advantages will become
more prominent.
Taking Japan's Akita Odate FiT (Feed-in Tariff)
project as an example, a typical case of
solving solar clipping loss and grid volatility by installing energy storage on the DC
side. The limited AC capacity of the project
which received FIT subsidies is 49.5kW,
and the DC side is of 3 5 0kW, which
features a striking DC/AC ratio of 7. Sungrow supplied a 1.1MWh ESS to automatically store excess power to avoid clipping
loss and significant output fluctuations,
guaranteeing 24 hours of continuous
power yields.
Figure 3: Sungrow DC-coupling ESS Solution
Call for future actions
With the goal of carbon neutrality by 2060,
partially due to the lack of relevant standards
early entrant in the energy storage market,
renewable energy in particular PV and wind
and specifications.
Sungrow has a robust track record across
power will assume the responsibility of
the globe. Apart from DC-coupling solution,
energy transition. The problems aforesaid
Accordingly, policies should be made to
Sungrow is a pivotal player in 1500V AC-cou-
like volatility and clipping loss of solar do still
clarify the technical standards and busi-
pling solution as well. With an untarnished
exist. Although many countries have intro-
ness models, making renewable energy
fire safety record on over 1000 energy
duced policies for an energy storage system
a grid-friendly source. Besides, PV manu-
storage projects, Sungrow is pioneering
to be added along with renewable applica-
facturers also need to spur the develop-
more ventures teaming up with global partners
tions, the current design and implementa-
ment through te chnical innov ations
to make energy more profitable, accessible
tion methods of the solution are uneven,
and comprehensive ser vices . A s an
and sustainable.
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Sungrow Power Supply Co., Ltd.
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European System Solution Manager, Sungrow
Tel: +86-551-65327878-8412
Email: amos.liu@sungrowsamsung.cn
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Sungrow Power Supply Co., Ltd. All rights reserved. Subject to change without notice
Amos Liu