PV Magazine - Special Issue on Storage (2015)

p h o t o v o l t a i c m a r k e t s & t e c h n o l o g y
Storage special
Taking the pulse of the storage industry with in-depth
features, interviews, market analysis and 20 of the most
exciting battery technologies of the moment.
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Battery Special
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From the editor
Waiting to charge
The solar+storage story is almost as old as solar itself. Early pio-
neers of PV saw the technology as an ideal means for off-grid
living – a rootsy, anti-establishment, independent power source
that allowed one to stick it to the man, not the mains. Basic lead
acid batteries permitted solar to shine in those early, pre-incen-
tive days, and it is only in the past few years that the two sectors
have come to work together once more as the solar industry has
begun to evolve beyond grid-tied constraints.
In that time, energy storage has been made sexy. From the open-
plan offices of Silicon Valley to the studious laboratories of
deepest Germany, innovations in battery technology are mak-
ing the industry more affordable, more reliable, more scalable
and more compatible with a solar industry that had begun to
cry out for a helping hand in swimming against the anti-renew-
able tide.
And now, the two industries appear to be on the cusp of a break-
through, walking in lockstep towards a future where home-
owners have a PV system on their rooftop, a battery in their
garage and an electric vehicle on their driveway; where busi-
nesses self-consume the power their rooftop systems produce,
storing excess energy or feeding from the battery during peri-
ods of peak demand; and where even storage at large-scale is
helping solar and utilities to co-exist.
June’s Intersolar Europe exhibition in Munich, Germany,
brought these developments to the fore, with storage the hot
topic that everybody wanted to talk about. This month, as Inter-
solar hops Stateside to San Francisco, the electrical energy stor-
age (ees) exhibition will run concurrently with the show in the
U.S. for the first time, and promises to have an equally pivotal
impact as its European counterpart (p. 29).
The ees exhibition will showcase some of the latest storage tech-
nologies being developed for the market, and our hand-picked
top 20 storage systems (pp. 11 – 18) have been selected to offer
an appetite-whetting insight into the types of products that are
shaping the solar+storage story.
As the storage story proves unputdownable, DNV GL’s Ray-
mond Hudson warns that we are only in the first chapter of what
promises to become a hefty tome, explaining that questions over
economics and safety are still being addressed at various points
throughout the industry (pp. 4 – 5). ABB’s Otto Preiss, mean-
while, believes that storage’s role in the solar industry is only
going to get bigger (p. 28), while Sonnenbatterie’s Christoph
Ostermann explains how a growing pro-storage landscape is
helping the industry towards a strong H2 2015 (p. 3).
For large-scale storage, the most pressing question appears to
be which type of battery technology will come to shape this
sector in the next few years (pp. 25 – 27): can lithium-ion’s lead
be reined in? In the home, smart storage solutions are chang-
ing the way we consume our energy (pp. 8 – 9), while develop-
ments at the grid-management level are ongoing but excitingly
fast-paced (pp. 6 – 7).
Finally, Germany appears poised to act as the vanguard of bat-
tery storage development in much the same way it shaped solar,
and pv magazine has surveyed the leading battery suppliers
in the German market to better understand the types of tech-
nology on offer, and the kinds of costs that can be achieved
(pp. 19 – 24). We hope you enjoy this download special.
Ian Clover
Editor
Photo:IanClover/SolarpraxisAG
Sonnenbatterie expects a
strong second half in 2015
Insight: In the second half of 2015, demand for battery-based storage systems will
continue its steep ascent, an effect compounded in Germany by the threat of an end
to subsidies for storage systems. Sonnenbatterie’s CEO Christoph Ostermann tells
pv magazine that his company is ideally positioned for this surge in demand.
Sonnenbatterie GmbH can look back on
a successful first half of 2015. Currently,
the storage system manufacturer, based
in the southern German town of Wild-
poldsried, is producing 500 systems every
month. Following a large expansion of
production capacity last year, Sonnenbat-
terie can now meet demand and is aiming
for continued gradual expansion. Nev-
ertheless, the manufacturer is intent on
staying flexible, Ostermann told pv mag-
azine. Currently, however, the focus is
on expanding sales structures. The man-
ufacturer sells its “eco” storage system
at its Sonnenbatterie Centers, which
are selected installation companies that
receive special training. The company
currently has 50 such centers in Germany
and plans to expand 60 or 70 by the end
of 2016. Next year, Sonnenbatterie wants
to break the 100 mark, says Ostermann.
He also sees potential in production of
storage systems specifically for PV. Over
the next year or so, production capacity is
expected to reach some 1,200 systems per
month, depending on demand.
Ostermann named several reasons why
he expects a strong second half. Tesla’s
announcement that it would enter the
domestic power storage market with its
Powerwall drew significant attention to
the industry. “No other manufacturer
has managed this before,” says Oster-
mann. “Tesla’s move has awakened many
more people in Germany to the fact that
this technology is also available here. It
remains to be seen, however, just how well
Tesla’s products perform and whether
they can deliver,” the CEO says. “Still,
you’ve got to plan on having strong new
competitors, and such announcements
alone help to move the market forward.”
By Ostermann’s reckoning, the market is
just getting warmed up. The fate of Ger-
many’s incentives for power storage in
combination with small PV systems is
currently up in the air. The government
has yet to respond to an inquiry from
pv magazine on whether the scheme will
be continued in 2016. If the program is
allowed to expire at the end of this year,
Ostermann expects a spike in demand by
Q4 at the latest. He compares the situa-
tion to the run on PV systems ahead of
big FIT cuts in years past. If such a boom
comes, Sonnenbatterie’s reaction would
be fast and flexible, and it would increase
its production on short notice.
Market entry USA
Sonnenbatterie also has big plans for the
U.S. market. At Intersolar North Amer-
ica the manufacturer will present two
new products, one for the domestic roof-
top market and the other for utility-scale.
The requirements for storage systems in
the U.S. are different from those in Ger-
many, said Ostermann. For instance,
small system operators are primarily
concerned with consuming the power
they produce themselves, but are also
interested in back-up systems. For large-
scale systems, the main interest is peak
shaving. The different price model in the
U.S. electricity market makes commer-
cial storage systems particularly lucra-
tive there. “The payback time is around
4.5 years,” he says, which is why Sonnen-
batterie wants to offer a system with a
capacity of up to 240 kWh.
Ostermann says that his company will
shoulder some $3 million upfront invest-
ment to enter the U.S. market. Just a few
weeks ago, Sonnenbatterie opened its
R&D center in Atlanta, GA. In the U.S.,
Sonnenbatterie also focuses on partner-
ing with installers, and recently signed a
cooperation agreement with Sungevity.
Other partnerships will follow, Oster-
mann confirmed. By the end of Septem-
ber, the company plans to deliver its first
storage systems to U.S. customers.
The U.S. is not the only foreign mar-
ket for Sonnenbatterie this year. Not long
ago the company named a country man-
ager for Italy, and Ostermann is currently
organizing the development of local Son-
nenbatterie centers in the country.
This year, 20 to 25 centers will be estab-
lished in Italy. The storage systems for the
Italian market will be supplied from Ger-
many. The manufacturer is also currently
working toward market entries in Aus-
tralia and the U.K. By next year, Sonnen-
batterie plans to open its doors in both
countries. S Sandra Enkhardt
Sonnenbatterie founders Torsten Stiefenhofer
and Christoph Ostermann (right) pose with the
latest Sonnenbatterie storage unit.
Photo: Sonnenbatterie

54
Battery Special Battery Special
Raymond M. Hudson is the Global Solar Service Line Leader for DNV GL. He
has been involved in the power electronics and renewable energy industry
since 1990 with an emphasis on power conversion and application of solar
PV and wind power.
“The storage
story is becoming
more powerful”
Interview: In June, DNV GL launched a new service for
developers looking to add storage to solar projects or in
standalone installations. This new service arrives at a time
when the number of storage products on the market is
beginning to take off. pv magazine spoke to DNV GL’s
Raymond Hudson, the director of solar for DNV GL, about
this development.
DNV GL now has a new service offering on the market,
to serve developers looking to roll out storage offerings or
employ battery storage on projects. Why is it that DNV GL
has made this strategic decision?
Raymond Hudson: DNV GL has in the past done a lot of advi-
sory work and certification testing for solar and storage, and
we see they are coming together in applications and deliver-
ing quite significant benefits. We have also observed, however,
that they cannot be treated separately because the benefits are
system benefits.
So we have aligned our teams and coordinated them in a way
that enables us to provide advisory and testing services for
solar+storage. DNV GL, through some of our legacy organi-
zations, has seen wind go from a minor technology to a major
part of our energy infrastructure. We have seen solar grow as
well, and now we see storage doing the same.
Our clients are asking: how can we deploy storage successfully?
There have been many years where people have pointed to the-
ory, where demonstration projects have been caught people’s
attention, and now we are moving into a stage when real proj-
ects are being rolled out and there is a growing demand for
storage.
A lot of this is being driven by the economic dynamics of self
consumption and the costs of solar really coming down.
I have heard a number of times that the pure economics for
solar+storage still do not stack up. What is your take on
that?
I think it depends on the consumer. It depends on what the ref-
erence point is. I follow closely what is the cost of solar gener-
ation versus the utility price. Because solar is distributed, the
reference point is really what does the consumer have to pay to
generate electricity with solar against what the utility charges.
There are many places in the world where this price parity has
been reached. In some places it is great, islands being an obvi-
ous location, but even in California where there is relatively
expensive electricity there is a benefit for the self generation of
solar, and then storage can begin to add to the benefits deliv-
ered to the consumer.
Such benefits could simply be avoiding some of the high demand
charges, or in the provision of backup power – which itself if a
different system topography. I think what we’re seeing is that the
cost curves are coming down and storage, with all of its bene-
fits, is becoming more of an economic story. There are techni-
cal advantages, there are economic advantages, and I think we
are getting close.
So would you say there are very specific use cases under
which the economics become advantageous?
I would say generally the way to look at it is that there are places
in which you have reached price parity with solar – that’s the
place to start – and then once you have that benefit solar begins
to pull storage into the picture.
My view is that solar will drag storage into the mainstream:
solar will in effect be the advocate for storage. If you look back
four years at a trade show like Intersolar, you would find two
batteries. The following year you could find 15 or so booths,
then half a hall, then a whole hall and so on. There is a debate
as to whether electric vehicles or solar is going to provide the
pull for storage, and while there are many more electrics vehi-
cles than applications of stationary storage, the pull of solar is
really strong.
In terms of technologies, it also appears that lithium-ion is
winning the race in battery storage for solar+storage appli-
cations. What do you make of the technological landscape at
present?
Lithium-ion certainly is the data point for now, although there
are some advantages with lead acid. Clearly these are the two
most mature technologies. My personal opinion is that there is
a lot of opportunities for innovation. The next person who is
going to be as rich as Bill Gates is going to be the one who inno-
vates in the storage area.
Hopefully there will be some breakthroughs in the storage sec-
tor too. But I do like the industry because it is not dependent on
huge technological breakthroughs. With solar there hasn’t been
a doubling of efficiency over the years, but more the industrial-
ization that has led to the improvements we now have in terms
of cost. 20 years ago I would have never thought the cost curve
for solar would have gone down as quickly as it has.
Storage has that opportunity. At DNV GL we have worked with
all of the different technologies, including some of the more
innovative flow batteries on the market, but we are seeing more
lithium-based projects and products. Part of our position is
reviewing the technology. We also review companies, but the
product, the performance and reliability is a big part of the pic-
ture. Storage is now getting mature enough that there are proj-
ects attracting real financing.
We do hear some reports regarding concerns about the safety
of various battery systems, particularly if they are going into
peoples’ homes. Do you think there are a sufficient number
of conversations being had at present about battery safety?
You can always have more conversations about safety, it is a top
priority. DNV GL has a number of testing laboratories that look
at safety and qualification testing for batteries. We have one in
Arnhem in the Netherlands; in Chowfont in Pennsylvania, U.S.,
and we have a partnership with the New York Best test facil-
ity. At these sites we test batteries from manufacturers all over
the world. We also carry out some system testing in California
at our photovoltaics laboratory in Berkeley and at the former
PV USA in Davis.
Certification and safety is important. We always believe in car-
rying out testing beyond the certification requirements. I would
say that the PV industry has done a good job in making sure
the projects perform technically safely and meet their finan-
cial commitments.
I’m old enough to remember the solar hot water industry in the
U.S. in the 1970s. So when I started working in solar PV in the
1990s people used to tell me about their solar hot water system
not performing as it should or just falling apart. So that tech-
nology didn’t do a good job, but fortunately you don’t hear that
anywhere near as much with solar PV!
I have seen a lot of solar+storage kits where a battery,
inverter and solar module is bundled within and sold as
an optimized solution. What do you make of these offer-
ings? Do you think the optimization actually pays off for the
consumer?
People are starting to think about a system as more than simply
a bunch of components that can be assembled. There is a grow-
ing understanding that solar+storage needs to be assembled as
a system and the components need to be compatible. I think
that packages are partly as a response to customer demand as
consumers look for a system and don’t have the skills to put one
together based on components.
These are still the early days but I do think it’s a good start. We
continue to do independent testing and system reviews. We can
help these projects to be successful. It is hard to say that there
are truly optimized solutions at this stage, but we are begin-
ning to see some good systems and that will lead to the indus-
try evolving.
With brands like Tesla capturing the public’s attention when
it comes to storage, how does this change things?
I think that solar+storage is moving into the mainstream. As
we move away from purely demonstration projects, there really
are different questions to answer. When people look to develop
solar+storage systems, they have to talk to financiers and every
one has a different appetite for risk. So just like in solar where
we’ve seen the financing grow in importance, so too will it be
in storage where the manufacturers are going to have to engage
with financiers to ensure that the story, so to speak, is all in line.
Questions will need to be asked, like how has this solar+storage
system been designed? How has it been tested? Do you have a
history in this technology?
And surely another key question is what is the economics of
a project? How will it be paid for?
Absolutely. Right now we are at the early adopter stage – which
is great! I think in the long run it will come down to economics.
With growing economics presumably the rate of adop-
tion will also change. How do you think solar+storage will
impact on utilities?
At DNV GL we host a Utility of the Future conference. We
held one in Washington this year in which we invited not only
utilities but also a lot of Independent Power Producers. Clearly
the utilities view solar+storage as a potential threat. Some are
embracing the change and trying to engage with the trend,
because the last thing utilities want to hear is grid defection.
On the other side is the end user who in many cases has been
treated simply as a rate payer, not a customer. So utilities are and
must become more sensitive to that. At DNV GL we see the full
spectrum. We see the economics of solar+storage improving;
we see some level of change is inevitable. Business models for
both IPPs and utilities in the long run are changing.
Do you think that utilities will engage more and more with
solar+storage?
One of the things we do at DNV GL is a survey in which we ask
utility executives a bunch of questions. We found that certainly
utilities are concerned about environmental issues and serv-
ing the end customer, but the business model for utilities in the
future is the number one concern at the moment. S
Interview by Jonathan Gifford
Photo:DNVGL

Peakshavingstrategyone
0
–2
–4
–6
0 5 10 15 20
Power in kW
With control strategy one, once a maximum grid feed-in limit is
reached–using weather prediction data and household usage
data–the battery begins to charge.This maximum feed-in is
calculated dynamically, to ensure that the battery becomes
fully charged, which occurs around 2:30pm–after the peak
PV production period.
Time in h
Source:TUM/Alexander/Zeh
residual load
storing power
grid power
maximum feed-in limit
Peakshavingstrategytwo
0
–2
–4
–6
0 5 10 15 20
Power in kW
Strategy two does not require detailed weather prediction
data, instead requiring only the number of daylight hours
to calculate the battery’s charging power necessary for
reducing the grid load and getting fully charged, which
occurs around 2:30pm–after the peak PV production
period.
Time in h
Source:TUM/Alexander/Zeh
residual load
storing power
grid power
maximum feed-in limit
76
Offloading the grid
Charging strategies: Facilitating self consumption of PV is an obvious use case for
solar. However, charging when it suits the end customer does not always suit the grid.
To meet this challenge, researchers in Germany and farther afield have developed
charging strategies that can make grid friendly batteries a reality today.
It is well known that one of the compet-
itive advantages of solar PV is its abil-
ity to be installed close to consumption
– the principle behind distributed gen-
eration (DG). But that also means that
large amounts of PV capacity are being
installed on low or medium voltage grids.
These grids were not designed to cope
with large amounts of PV-generated elec-
tricity to flow into them; in fact, quite the
opposite. Hence, utilities and grid opera-
tors harbor concerns that on sunny days
grids could become unstable, causing
power outages when large amounts of
solar power flows into the grid.
Many experts believe that compla-
cency within the PV industry in terms of
potential grid destabilizing effects of PV
should be avoided. One such individual is
researcher Alexander Zeh from the Insti-
tute of Electrical Power Grids at Munich’s
Technical University (TUM).
“Low voltage grids aren’t dimensioned
for a big amount of feed in power,” he
said, “especially not the transformers
and power lines.” Zeh is a part of a team
at TUM looking at ways battery storage
systems can help limit this feed in, essen-
tially giving the grid a helping hand. “We
have to reduce that feed in power of the
PV systems.”
Enter batteries
Battery systems attached to residential
or commercial PV arrays are emerging
as the best way to limit this grid feed in,
while also optimizing the installation for
the self-consumption of the solar power
produced on site. However, in theory, if
optimized purely for self-consumption,
batteries could make the situation worse
for grid operators. Earliest opportunity
charging is employed to optimize a bat-
tery for self-consumption. It is therefore
optimal for a battery to become charged
as early in the day as possible. Unex-
pected cloudy conditions later in the day
could potentially leave a battery partially
full by evening if the rate of charge is too
slow. This means that batteries will begin
charging as soon as the sun rises, from
the electricity that is additional to the
household’s immediate needs.
“If all the batteries get full at the same
time, there could be a jump in the grid
load at about noon, and you won’t reduce
the maximum grid load in any way,” says
Zeh. This is where optimizing battery
operation for both feed in limitation and
self-consumption comes in.
Researchers are developing algorithms
to formulate dynamic control strategies
to do just this, and the results thus far
have been positive. Using such a control
strategy and a battery with a capacity of
5 kWh to 10 kWh, Zeh and his TUM team
believe that grid feed in can be limited
to 40% of the PV array’s peak capacity,
increase self-consumption, and lose only
about 1% to 2% of the total PV electric-
ity produced. These losses are known as
“throttling losses” where the PV gener-
ation must be curtailed to prevent grid
feed in.
Operation strategies
The TUM team has developed and pub-
lished findings on a number of different
battery operation strategies. In strategy 1
(see diagram 1, top right), weather pre-
diction data and household load predic-
tion data is used to determine a feed in
limit for surplus PV power which, when
reached, triggers the battery to begin
charging with this surplus power. At one-
minute intervals during the day, the con-
trol strategy adjusts this limit if the load
or weather conditions do not correspond
with the predictions.
In strategy 2 (see diagram 2, bottom
right), the household load data and the
number of sunlight hours – the time until
sunset – are the inputs used to deter-
mine a steady rate of battery charge that
is needed to ensure that PV surplus power
does not exceed a determined rate, such
as 40% of the installed PV peak capacity.
In the case of a very sunny day, when the
feed in limit will be reached, the opera-
tional control strategy can be switched to
strategy 1.
Both strategies have potential advan-
tages and disadvantages. With either
strategy there is the potential that the
battery will become full and throttling
of the PV system occur. These potential
throttling losses are lower with strategy 1.
However, self-consumption losses, of
around 1%, are more likely to occur with
strategy 2 if the battery does not become
fully charged by the end of the day. In
terms of inputs required, an advantage of
strategy 2 over strategy 1 is that precise
weather production data is not required,
only the number of hours until sunset.
The TUM team has developed blended
strategies too, which can be employed
depending on weather forecasts, as it
is advantageous to employ strategy 1
on sunny days and strategy 2 on mixed
weather days.
Financial losses
Although applying these operation strat-
egies minimizes throttling and self-con-
sumption losses, there is a potential
resultant reduced rate of return for the
householder’s battery investment for
employing operational strategies to limit
feed in. Zeh calculates them at being less
than 10%. Zeh envisages that compensa-
tion for this can be provided through bat-
tery subsidy schemes. “It’s a small step to
say, ‘if you reduce your feed in power to
40% or 50% instead of 60%, then you get
a better incentive program,’” he explains.
An additional advantage of using bat-
tery operation strategies to limit grid
feed in is that additional hardware is not
required. Operation strategies can sim-
ply be programmed into the existing bat-
tery control software. What is required is
a smart meter in the home, to provide the
household’s electricity demand profile.
Precise weather prediction data is not
free, however, and as noted this is the
decided advantage of the TUM control
strategy 2 over strategy 1. Where less
detailed weather predictions are needed,
or indeed the time until sunset, these can
be obtained online for free.
Feed in limit to 30%
Another German research group has
made headway on reducing grid feed in
through the application of battery charge
strategies. Jan Binder, from the Center for
Solar Energy and Hydrogen Research
(ZSW) in Stuttgart, has developed two
battery control strategies to limit peak
grid feed in.
Binder and his team at ZSW have for-
mulated two delayed charge strategies,
one based on a linear increase of charge
through the day, the second on histori-
cal load and production data. Both have
shown similar results to the TUM team,
as they manage to significantly reduce
peak grid feed in, without vastly affect-
ing a household’s self consumption. “We
almost square the circle with the his-
torical delayed charging strategy,” says
Binder.
An additional advantage delivered by
the control strategies is that batteries are
not required to hold charge for as long a
period as when they are charged at the
earliest opportunity. Lithium-ion batter-
ies in particular have a longer lifespan if
they are not kept fully charged for long
periods, thus improving the economics
of a battery purchase.
Cheap capital
Batteries for PV storage remain rela-
tively expensive despite recent price falls,
and Binder is confident that households
will install them, particularly as a hedge
against further increases in electricity
rates.
Dirk Uwe Sauer, from the University of
RWTH Aachen’s Electrical Energy Con-
version and Storage Systems team, agrees
that it is inevitable that batteries will be
widely installed in homes, given the eco-
nomics of self-consumption in Germany
at present. Sauer says that while big large-
scale storage solutions may be cheaper
than many thousands of batteries in
homes, due to economies of scale for one,
utilizing the existing capital within many
household budgets may make distributed
storage cheaper in the long run.
“The investment cost is higher for these
small systems,” says Sauer, “but when
you take the overall system cost includ-
ing the capital cost then things look dif-
ferent, because the individual is happy
already with a significantly smaller inter-
est rate or ROI compared to a utility or a
professional operator.” He also notes as
the problem of feed in peaks occurs on
the low or medium voltage grids, that is
where the solution is needed. “You won’t
construct a GW pumped hydro station
somewhere on the low to medium volt-
age grid, so there are two different levels
of discussion in terms of storage technol-
ogies.” S Jonathan Gifford
The charging needs of the end customer do not always align with what’s best for the grid, prompting researchers
to develop charging strategies designed to better handle load fluctuations.
Photo:PortlandGeneralElectric/Flickr
Graphics:HaraldSchütt

98
Smart storage to power
the Smarthome
Storage and the Smarthome: PV, batteries and consumer electronics are
coming together to deliver innovative solutions for the homeowner. It is capturing
imaginations, but can it capture the future of residential energy?
In terms of energy, Smarthome applies in
a number of ways. These can be loosely
divided into the categories of smart light-
ing and energy efficiency; heating, cool-
ing and smart thermostats, and distrib-
uted energy production and demand
management. It’s in this third category
where solar and storage sit, and it is an
area that has attracted the focus of solar
companies and battery providers alike.
There is some debate among the
PV industry as to how widespread
solar+storage will become. U.S. PV sup-
plier and project developer SunPower is
particularly bullish on the prospects for
PV systems coupled with battery stor-
age. In a recent analyst day presentation,
SunPower CEO Tom Werner said that the
firm was “investing heavily in software,
to give the customer the control over that
[their PV produced] electron so they can
use it whenever they want and match
it with the load.” SunPower has been
developing a solar+storage pilot project
in Australia, a market Werner says is a
good fit due to its ample sunshine and
high electricity transmission costs.
In November 2014 UBS released a
study in which it too concluded that
solar+storage is already financially com-
petitive for Australian households. The
analysis looked at a 5 kW rooftop array
coupled with 5 kW storage, at a cost of
AUD$18,000 (US$14,350), and concluded
that it would offer a household a return
of 10% a year when compared to buying
grid electricity.
“The cheapest system looked at is
already capable of earning its cost of cap-
ital,” UBS utilities analyst David Leitch
concluded.
However, these views shared by UBS
and SunPower are not universally held.
Certainly, when it comes to households
taking the bold step of installing suffi-
cient storage capacity to allow them to go
off grid – a practice known as grid defec-
tion – there has been some criticism. On
Greentech Media’s Energy Gang Podcast,
host Stephen Lacey has in the past sug-
gested that reports pointing to the eco-
nomics of grid defection stacking up in
some U.S. states are being overblown
and do not reflect the technical barriers
to large-scale grid defection. Co-founder
of Generate Capital Jigar Shah similarly
remarked that while he agreed that the
case for grid defection through battery
deployment was overstated, he was happy
to use it as a bargaining tool in discus-
sions with recalcitrant utilities.
“That people who are less educated
than we are on these topics are willing to
consider grid defection seriously I hap-
pily use to my advantage, and that’s poli-
tics,” said Shah. Bloomberg New Energy
Finance (BNEF) analysis also paints a
bearish picture for energy storage tech-
nology roll out in the short term. This is
despite BNEF’s firm view that residential
energy storage “will play a crucial role
in the transition of our energy system.”
These are the words of BNEF associate
for Energy Smart Technologies, Logan
Goldie-Scot. “There are numerous chal-
lenges,” says Goldie-Scot. “Paybacks for
storage for self-consumption remain too
long for the average consumer at more
than 12 years, and there is consumer
anxiety about the technology cycle life.
Policy makers often offer contradictory
signals, such as Germany, which has a
subsidy program for end user energy
storage and also a tax on self consump-
tion for PV systems larger than 10 kW.”
Power electronics innovation
Grid defection is an extreme example of
solar+storage deployment and there cer-
tainly exists significant opportunities in a
range of geographic markets. Along with
Australia, as already mentioned, Hawaii,
California and Germany are all potential
first-mover storage markets.
This is the geographic roll out strategy
of microinverter supplier Enphase’s AC
storage product, communicated when
the product was unveiled at last year’s SPI
trade show in Las Vegas, U.S. The Cali-
fornia-based company integrates one of
its microinverters into each battery unit.
Goldie-Scot says that the power elec-
tronics and control software is an area
within storage around which a great deal
of innovation is currently taking place.
“Power electronics and energy manage-
ment is increasingly competitive,” says
Goldie-Scot. “On the hardware side, lots
of development is underway on improved
power conversion hardware, such as bidi-
rectional and ‘smart’ inverters.”
Larger advantages
BNEF notes that at the forefront of bat-
tery production – the cells themselves –
large manufacturers have an advantage
given the high capital costs and econ-
omies of scale. Companies such as LG
Chem, Samsung SDI, Panasonic and
BYD are all going for scale. The growth
in e-mobility is also playing a role here,
particularly for the latter two manufac-
turers that are very active in that space.
Delivering customer-focused power
management solutions, however, is pre-
senting opportunities for small compa-
nies – something that is particularly evi-
dent in the solar+storage market.
“There are plenty of examples of suc-
cessful smaller companies that are bring-
ing products to the end consumer, such
as Sonnenbatterie and E3-DC,” says
Goldie-Scot.
Sonnenbatterie presents itself as
something of an unlikely player in the
solar+storage space. It has brought
down the costs of its solar-tailored stor-
age solution rapidly from one generation
to another.
Sonnenbatterie operates out of the
picturesque German hamlet of Wild-
poldsried, itself an energy indepen-
dent town drawing on large solar, wind
and geothermal installations in the sur-
rounding area. An innovative sustain-
able community heating system sup-
plies the Alpine region with warmth over
the cold winter months. Sonnenbatterie
reports that smart storage solutions, with
advanced control software and inter-
faces, are required to serve both con-
sumer demands and to support the grid
in areas of high renewable penetration.
“We have the situation today where
the share of renewable energy, espe-
cially solar and wind, is quite high so we
have situations where the grid needs to
be supported. Therefore, to make sure
that the storage system is working in a
grid-friendly way, you need intelligence
behind it,” says Sonnenbatterie CEO
Christoph Ostermann. “If storage isn’t
smart then it’s just a battery, not a stor-
age system.”
Sonnenbatterie has shipped more than
3,500 systems over the past four years and
has ramped battery assembly operations
in Germany to such an extent that it says
it can benefit from economies of scale.
The price reductions it has achieved have
been the result of a number of factors,
including a 70% reduction in unit assem-
bly time, and a streamlining of the prod-
uct itself to do away with features such
as backup power for German consumers
that are not required. Falling battery cell
costs have also had an impact.
Sonnenbatterie is expanding into the
U.S. market throughout 2015, where
backup power is a more frequently
desired feature, and will also target Aus-
tralia in the near future. The company
plans to tailor its products to meet a
range of geographic and market require-
ments. Sonnenbatterie closed a €7.5 mil-
lion (US$8.5 million) financing round in
December 2014 to support these plans.
Automation
Ostermannthinksthatthesolar+storage-
empowered ‘prosumer’ is unlikely to go
off grid, particularly in Germany, any
time soon. He does, however, believe
that a push towards greater automation
within the home through enabling Inter-
net of Things (IoT) and Smarthome tech-
nologies is inevitable.
“A lot of people are still afraid about
Smarthome devices because they do not
trust the technology. They think, ‘what if
a hacker comes and can access my house?’
But this is just a process and people will
get used to it step by step. It makes life
easier, and this is the key for intelligent
storage systems because it is impossible
to control them manually.”
There are a number of supportive
smarthome applications that are begin-
ning to make waves throughout the
industry, advancing prosumers’ abil-
ity to really take control of their energy
consumption patterns and monitoring.
Alarm.com was recently awarded the
Mark of Excellence Award at the Inter-
national CES show for its geo-services
technology, with which smart thermo-
stats adjust themselves automatically
depending on the location of the home’s
residents. The service tracks household-
ers according to their smartphone loca-
tion, warming the home as a resident
approaches and backing off the heating
as they leave. Germany’s Tado has been
employing similar technology in Europe.
Similar applications are also imagin-
able with solar+storage, particularly in
warmer climes where air-conditioning
is a source of major electricity demand
along with the types of grid peaks with
which utilities regularly grapple.
BNEF Founder Michael Liebreich has
previously noted in his annual cleantech
trends mailing that the excitement sur-
rounding “connected homes and power
storage” may be overhyped, but that it is
set to “catch the consumer imagination
in 2015 and beyond.” Liebreich notes that
Nest, now owned by Google, as well as
Apple, Honeywell and British Gas are all
actively rolling out products, along with
another security firm ADT – similar to
Alarm.com – leveraging its presence in
many million homes as a security-ser-
vices provider.
“All this should open up the chance for
households to take advantage of time-
of-use electricity pricing,” wrote Lieb-
reich. “Regulators in many countries are
looking to require utilities to offer this,
and indeed Italy and Ontario in Can-
ada already do so. Large-scale uptake of
demand-side management technologies
is likely to be faster in the U.S., where
air conditioning is a key part of the load,
than in Europe. The prize for the power
system as a whole will be much greater
flexibility to cope with peaks and troughs
in demand and in variable generation
from wind and solar.” S
Jonathan Gifford
Photo:Weberhaus
Photo:Sonnenbatterie
Newly built homes are ideal testbeds for smarthome technology, combining solar PV systems, electric
vehicles, storage technology and time-of-use electricity pricing.
Sonnenbatterie’s manufacturing output has
increased in step with the market development.
Heating and cooling services, combined with
solar+storage, are shaping the smarthome.
Photo: Bundesverband Wärmepumpe e. V.

Storage That
Makes Cents
Intersolar North America
West Hall, Level 2, Booth
8121
Stop by our booth to speak with one of
our staff and check if you qualify to join the
Sonnenbatterie family as a channel partner!
Sales hotline: +1(310)853-2404
Sonnenbatterie USA | Los Angeles, CA
E-mail: info@sonnen-batterie.com
Europe’s #1 Smart Storage
Solution is now available in
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+ Easy Installation
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Storage That Makes Cents
11
Storage Special
| www.pv-magazine.com10 | www.pv-magazine.com
Lower cost per kilowatt hour, more charging cycles, greater depth of discharge, larger
capacity, safer materials… or even just better aesthetics: there are many ways in which
the storage industry is pushing the boundaries of battery technology. These 20 storage
products are all – in some way – helping the sector move into the mainstream, and are
plugging some of solar’s evolutionary gaps along the way.
exciting
storage
products
Oxis Li-S energy storage
Set for roll out in early 2016,
Oxis Energy’s new lithium
sulfur (Li-S) batteries have been
tested in a real world environ-
ment in collaboration with solar PV
company Proinso at Project Helios –
a U.K. demonstration center for bat-
tery research – and the results have been
encouraging. Oxis is targeting a retail
price for its Li-S 3 kWh Li-s battery
storage system for around $250/kWh by
2020, thanks largely to the key material
being sulfur, which is cheaper than
lithium-ion. Oxis also claims that its
Li-S batteries can achieve 2,000 cycles
before capacity reduces to 80% of its
beginning of life (BoL), as well as 100%
depth of discharge.
What’s in store?
Oxis’s cells have an indefinite shelf-life,
meaning there is no charging required
when left for an extended period of time.
The Li-S battery is also considered an
eco-friendly alternative to lithium-ion,
using recycled sulfur that is a by-product
of the oil industry.
1

12
Storage Special
| www.pv-magazine.com 13| www.pv-magazine.com
Alevo GridBank
storage reservoir
The Swiss-based startup Alevo
Group has entered the utility-
scale storage market with a bit
of a bang this year thanks to its 2 MW
(1 MWh) energy storage “reservoir”, the
GridBank. Wrapped in 40-foot contain-
ers, the GridBank is comprised of racks
of lithium-ion cells that boast the capac-
6
ity to deliver more than 50,000 recharge
cycles – which Alevo claims is 10 times
the life of competing technologies. The
cells are modular in design, meaning the
GridBank can be scaled to suit a range of
utility-scale applications, while Alevo’s
supportive analytics and grid monitoring
software enable system owners to deter-
mine where, when and how their Grid-
Bank stores and delivers energy.
What’s in store? The GridBank’s
stacked services are designed to enable
greater integration of renewable energy
on the grid, which Alevo claim can help
offset necessary grid updates, enhance
grid stability, time-shift energy, regu-
late frequency and control voltage. Alevo
Analytics determines the service mix
that provides the optimal benefit to the
grid in real time.
SolarWorld
Sun-Pac LiOn storage
German solar PV manu-
facturer SolarWorld has
enhanced its storage
offering in recent months with the
development of another battery
system – the SunPac LiOn.
Employing lithium-ion phosphate
battery technology, the scalable
storage system is poised for a
European and U.S. launch in the
fourth quarter of the year. The sys-
tem size starts at 2 kWh and can
be scaled in 2kWh increments,
with each storage unit connected
together simply via a plug-and-
play application. SolarWorld
claims that the SunPac LiOn has
a depth charge of 100% and a life-
time of 10,000 charging cycles, and
is also connected on the AC side,
making it easily retrofittable to
existing PV arrays.
What’s in store?
The SunPac LiOn is being pitched
at “storage curious” households,
and is a scalable battery unit that
enables homeowners to increase
or decrease capacity as needs and
budget require.
2
SolarEdge’s StorEdge
batter solution
The StorEdge from Israel’s
SolarEdge will provide energy
independence for homeowners
keen on maximizing their solar self-con-
sumption. The DC-coupled storage solu-
tion is versatile and large enough to
act as a backup power unit, and can
be easily paired with a SolarEdge
DC optimized inverter that will
manage both the PV array and
the storage system. With a shared
PV and battery DC bus, the
StorEdge is designed to reduce
conversion losses because PV
power is directly stored in the
battery. Equipped with SafeDC
architecture, the system is
safe and high qual-
ity, requiring no
special wiring
and utilizing the
same PV cables.
The StorEdge also
has a full moni-
toring solution
that enables sys-
tem owners to
monitor their PV
production and
consumption.
3
What’s in store?
The StorEdge solution is designed
to be compatible with Tesla’s new home
battery solution, the Powerwall.
ViZn Energy Systems’
turnkey storage platform
Incorporating ViZn’s Z20
zinc-iron flow batteries with
inverters, grid connects and
auxiliary components from Princeton
Power, the new ZAC energy storage plat-
form is a turnkey AC flow battery sys-
tem that has been designed specifically
for commercial and industrial custom-
ers. The ZAC is available in sizes ranging
from 320 kWh to 960 kWh and comes
with a simple AC connection for meter
4
or utility interconnection, thus allowing
system owners to self-consume with ease
and monitor their power consumption
via the integrated control system.
What’s in store?
Based on redox flow battery technology,
ViZn claims that its ZAC platform is
one of the most cost-effective of its type
on the market today, delivering rapid
charge and discharge responses that can
perform unlimited cycles per day in all
types of weather coditions.
Sonnenbatterie eco
The new iteration of
Sonnenbatterie’s eco system
is a boundary-stretching piece
of kit that has already turned
heads at the recent Intersolar Europe
trade show in Munich, Germany.
Sporting a life of 10,000 cycles, the
fourth generation, German-made
Sonnenbatterie eco has reduced the
5
cost-per-kWh of stored power to around
$0.19 – $0.27/kWh. With such a long life,
the Sonnenbatterie eco can be used in a
variety of storage applications, includ-
ing residential electricity and heat pro-
vision, as well as grid-based services
and aggregation into a virtual power
plant. Sonnenbatterie has also revealed
that the system can be tied to a micro
CHP (combined heat and power), thus
enhancing its compatibility and widen-
ing its potential customer base.
What’s in store?
Available with rated capacity from
4 kWh to 16 kWh in increments of
2 kWh, the new Sonnenbatterie eco will
appeal to a broad range of system
owners, supported by the increased cycle
life and boosted depth of discharge
(up to 100%).

1514
Storage Special Storage Special
ASD Sonnenspeicher
Pacadu
Based in Freiburg, Germany,
ASD Sonnenspeicher has
recently unveiled its new
Pacadu battery system that the company
claims is the first energy storage sys-
tem that connects battery cells in paral-
lel, rather than in a series, thus increas-
ing its lifespan and performance while
lowering production costs. Comprised
8
of lithium-iron-
phosphate stor-
age, the Pacadu
“inside” tech-
nology allows
for each cell to
be connected
in parallel,
thereby mitigat-
ing the effects
of the weak-
est performing
cell – a prob-
lem for those
storage sys-
tems connected
in series. “A
storage device
with cells con-
nected in series
works well at
first,” said ASD
MD Wolfram Wal-
ter. “However, when the performance
of the entire system is hampered by one
cell, this faulty cell cannot be replaced
because the capacity, internal resistance
and health of the new cell would not
match that of the existing cells that have
already aged.”
What’s in store? The Pacadu will be
available in individual module sizes of
up to 3.2 kWh, which can be scaled up
to develop a large-scale storage system
or even used for electric vehicles.
Panasonic residential
storage battery
Already rolled out in
Australia, the new
Panasonic residential stor-
age battery system is a lithium-ion
battery with a storage capacity of
8 kWh. Measuring 1.4m x 96.6cm
x 27.8cm, the system is touted as
a “perfect complement to existing
and new solar systems on residen-
tial buildings”, and is scheduled for
a North American and European
launch later this year. Designed to
reduce households’ dependence
on the energy grid, the battery has
a 2 kW output, remote and pro-
grammable charge and discharge
and an emergency backup fea-
ture to ensure homeowners have a
steady power supply in the event
of power outages.
What’s in store?
Working in har-
mony with a solar
PV system, the
Panasonic storage
battery enables
maximized self-
consumption
around-the-clock,
thus lowering a
consumer’s energy
bill.
7
Electrovaya MWh-scale
storage solution
Canada’s Electrovaya has
developed a MWh-scale
energy storage solution
that has been designed to solve large-
scale power quality, reliability and secu-
rity challenges. Available in capacity
ratings from 0.3 MWh to 2 MWh, the
storage system uses lithium-ion super-
Polymer 2.0 technology to deliver high
nominal power ratings and battery
round-trip efficiencies of greater than
90%. For utilities, Electrovaya’s flexi-
ble technology ensures grid infrastruc-
ture investment can be deferred by offer-
ing uninterrupted power supply, the
possibility of micro-grid implementa-
tion, voltage and frequency regulation
and renewable energy integration. The
system can also be applied to industrial
11
and commercial sites, with the capacity
to reduce demand charges due to peak
power consumption.
What’s in store?
The development of Electrovaya’s energy
storage system generated more than
150 new patents, including a unique,
non-toxic approach to manufacturing
that removes the toxic component
of lithium-ion production, thereby
eliminating associated liability risks.
Redflow
zinc-bromide
battery
Australia-
headquartered
advanced energy storage com-
pany Redflow has developed a
range of zinc-bromide flow bat-
tery modules suitable for a vari-
ety of PV-supported applications
thanks to their ability to easily
store and shift renewable energy,
manage peak grid load and sup-
port off-grid power
systems. The range is available in
8 kWh, 10 kWh and 11 kWh
energy densities, and is also suit-
able for configurations in par-
allel or a series. The zinc-bro-
mide electrolyte is a water-based
natural fire retardant, making
the ZBM range safer than typi-
cal battery systems, and the bat-
tery can achieve 100% depth
discharge, making it an ideal
option for regions with unstable
grids or high levels of renewable
penetration.
What’s in store?
Redflow has partnered with
Flextronics to roll-out its ZBM
range across global large-scale
commercial markets, and has
recently been introduced to
Europe.
10
Imergy
vanadium flow
battery
The large-scale ESP30 storage
system from Imergy is a
vanadium flow battery that is a flexible,
scalable and turnkey solution for any
commercial or industrial consumer in
need of reliable on- and off-grid energy
backup. The Imergy ESP30 boasts a
capacity range of 120 kWh to 200 kWh
and a 100% depth of discharge rate,
and has already proven attractive to a
number of schools, municipals and
remote regions around the world as a
steady, safe and affordable alternative
to diesel-backed power generators.
What’s in store?
The Imergy ESP30’s key applications
include peak shaving, demand response,
9
energy shifting, utility grid ancillary
services, renewable energy firming and
microgrid and back-up power, coupled
with a low maintenance design
and unlimited charge-discharge cycle
capability.

1716
Storage Special Storage Special
BYD B-Box
battery
China’s BYD has
recently added to its
impressive portfolio of
battery storage products the B-Box bat-
tery, which is made by Fenecon and
13
Aquion S-Line
battery stack
Aquion Energy’s new
hybrid-ion batter-
ies were awarded the
Innovation Prize for Energy Storage at
the recent Intersolar Europe 2015 trade
show, and it is easy to see why. The
American company’s Aqueous hybrid-
ion batteries have been developed as a
sustainable and reliable alternative to
lithium-ion and lead-based cells, and
are intended for use in residential, off-
grid and micro-grid applications. The
hybrid-ion technology uses an electro-
lyte based on an aqueous sodium sul-
fate solution, which delivers increased
levels of safety and constant perfor-
mance even during periods of extreme
temperature fluctuations.
What’s in store?
Aquion’s S-Line battery stacks,
which utilize the Aqueous hybrid-ion
technology, have been developed
for stationary, long duration applica-
tions. They are 2 kWh and 48 V
nominal systems that can be con-
nected in series or parallel, delivering
15
Varta engion home
storage
German battery giant
Varta has augmented its
residential storage
offering with the introduction in June
of the new engion element lithium-ion
17
Powervault
storage box
solution
Four days –
that is all it took
for London-based storage startup
Powervault to raise $1.1 million
on crowdfunding investment plat-
form Crowdcube for its new home
energy storage system. The sleek,
patent-pending storage box solu-
tion is aiming to take on the Tesla
Powerwall at its own game… but
to do so more cheaply. The Power-
vault will retail at $3,140 for the
2 kWh system and $4,400 for the
4 kWh system, and unlike the
Powerwall, the Powervault com-
prises battery, charger, inverter
and control unit, and can be
installed in under an hour, the
company claims. According to
Powervault MD Joe Warren, the
system will lower household bills
by around 15% per year, and is
compatible with all new and exist-
ing rooftop solar PV systems.
What’s in store?
Currently constructed using
6 x 12 sealed lead-acid batteries,
Powervault hopes to soon roll out
a lithium-ion version of the bat-
tery, and is set to steer the crowd-
funding towards further cost
reduction, with a targeted reduc-
tion of 20%.
16
Tesvolt plug
and play
storage system
This 0.5 MWh
storage sys-
tem from German startup Tes-
volt is constructed using lithium-
iron manganese batteries and has
been designed as a transportable,
plug-and-play storage solution for
use both on and off the grid. Due
to its short discharge time at high
power, allied to its capacity dis-
charges, the battery accumula-
tor delivers effective energy supply
that is easily compatible with PV
systems, wind energy applications
and biogas plants. System owners
can tap into the Tesvolt TLC 1,000
for personal energy consumption
around-the-clock, or the battery
can act as an emergency power
backup if and when required. The
system has been designed to be
intrinsically safe, modular – allow-
ing for scalability to suit power
needs – and easy to monitor and
maintain, augmented and con-
trolled by a smart online platform.
What’s in store? The Tesvolt
TLC 1,000 has a maximum DC
nominal charging power rate of
144 kW and a 90% depth of dis-
charge, which sets new standards
for economical storage systems,
claims Tesvolt.
12
comprised of iron phos-
phate cells and available
in either a 2.5 kWh capac-
ity standard 3U battery,
or can be extended into
a 10 kWh battery cabi-
net. According to BYD,
the B-Box can hold 6,000
cycles even under rel-
atively high discharge
rates of 1C and, depend-
ing on the capacity, can
achieve discharge rates of
up to 12.6 kWh. German
inverter specialist SMA
has already confirmed that
the B-Box is to be com-
patible with its Sunny
Island Inverters, while the
in-built modular design
allows for greater flexibil-
ity for the system user.
What’s in store?
Depending on the number
of standard 3U batteries slotted within
the B-Box cabinet, the battery system
can be used for general residential self-
consumption, commercial and industrial
peak-shaving, or even as a backup power
source.
a wide range of potential
configurations.
battery system. The
complete system comes
bundled with an inte-
grated inverter and
energy management
tool built in, and is a
colorful (available in
green, red, blue, white,
yellow or gray), aes-
thetically striking addi-
tion to the home. The
battery is available in
two sizes: the engion
element 3 has a nom-
inal battery capacity
of 3.2 kWh and sys-
tem power of 1,600 W,
while the larger engion
element 6 is a 6.4 kWh
battery with system
power of 2,000 W.
What’s in store? Ease of use. Varta is
marketing these latest engion systems
as ideal for storage beginners, and states
that the entire battery can be monitored,
configured and controlled via a simple
online portal.
Delta Flex E3 battery
Delta’s new smart
energy storage system,
the Flex E3 battery, is
touted as a highly
flexible storage addition for homeowners
and small businesses keen on enhancing
the returns on their energy investments.
The Flex E3 has an energy conversion
efficiency of 93% and a smart-grid con-
troller platform that delivers optimal-cost
storage and consumption. Aesthetically
pleasing, Delta’s latest product also
appears to be user-friendly and easily
14
integrated into a variety of system
architectures.
The Flex E3 provides storage for PV
systems ranging from 2.9 kWh to
3.7 kWh, or three batteries can be run
in parallel to cater for an 11 kWh system,
depending on whether the client opts
for the lead-acid or lithium-ion battery.
What’s in store?
The Flex E3 is embedded with Delta’s
AC inverter, which delivers more
than 96% energy conversion efficiency
and nominal continuous power output
of 2.34 kW.

19
Battery Special
| www.pv-magazine.com
Market overview: Storage systems in Germany (Referring to table on pages 20-24)
Residential home battery storage systems are a hot topic in the German solar industry. By 2016 the figure of installed systems could be as
high as 40,000. This has made it attractive for providers to develop these systems. After the German market, providers are eyeing markets
in the U.K. and Italy, such as Sonnenbatterie and Varta, as well as in the U.S. The German market may well develop into the vanguard of
battery storage systems and become the place where problems are first recognized and solved, particularly concerning issues such as con-
nectivity, energy management, service life estimates and safety measures.
The staff at pv magazine surveyed battery providers in the German market, garnering a total of 51 respondents that offered details of
more than 290 systems. To a certain extent some systems are similar because wholesalers combine the same power electronics and the
same batteries in different ways. If one identifies those that use different power electronics, then there are around 40 different systems.
The full version of the survey, with some one hundred data points for each system and explanatory notes for some of the systems, can be
found in our online database at: www.pv-magazine.de/marktuebersichten/batteriespeicher/speicher-2015
The full version online contains further detailed information on efficiencies, energy management and security standards. This table is
intended as a snapshot of the survey.
Some explanations
Costs and prices: These can sometimes mislead because they contain different benefits in terms of monitoring, installation and accesso-
ries, for example. Also, the complexity of installation procedures can vary.
Those prices marked ** include installation.
Connection of the battery: There exist three possible connections points.“AC”-systems are connected at the AC side of the households
grid (e.g. SMA Sunny Island, Sonnenbatterie, Varta), while“DC“ systems are connected at the intermediary circuit of the inverter system,
i.e. behind the MPP Tracker and first DC-DC-converter, but before the DC/AC converter. These systems are generally bundled as integrated
solar inverter/storage systems. Some“DC”systems use bidirectional AC/DC converter, they can also be connected as AC-systems in case
the storage is retroactively added to the solar system and the solar inverter already exists (e.g. E3/DC, Fronius).“DC-Gen”systems form
the third storage system class. They are connected to the DC side of the inverter, i.e. before the MPP-Tracker (e.g. Tesla combined with
Solaredge, Solarwatt).
Uninterruptible power supply: There exist different kinds of uninterruptible power supply and standalone systems, which the table dif-
ferentiates in the online version.
Usable for reserve power: In Germany, there is a strong movement to a business model in which storage systems will be used for reserve
power, which offers the operator additional income.
no-load consumption: There exist big differences between the systems concerning this parameter. Particularly because for long periods
over the year there is only a low power load applied to the systems; the no-load consumption strongly influences the system efficiency.
Calculated by pv magazine: We calculated the data in the three columns to the right based on the providers’entries in the table:
Cost per kWh electricity = price/(capacity × cycles)
Cost per kWh capacity = price/capacity
DC system efficiency = (efficiency solar - battery) × (efficiency battery - appliances)
AC system efficiency = (efficiency home electrical system - battery) × (efficiency battery - appliances) × 97%
For the efficiency values of the AC systems, we assumed that they were combined with a 97% efficient solar inverter, in order to make them
comparable to DC systems.
For the cost parameters of the DC systems, we subtracted a solar inverter cost of €180/kWp in order to make the values comparable to the
values of the AC systems.
Cost of stored electricity (€/kWh): Some manufacturers give rather high cycle service life numbers (up to 10,000) for their batteries. Gen-
erally, the cost of stored electricity reduces directly proportional to the number of possible cycles. However, it has to be discussed how
many cycles one needs for a storage system per year, and at which age batteries can survive independently of the cycle service life. If ser-
vice life is 15 years and one needs one cycle per day, one would need about 5,500 cycles. In countries with severe winters (as in Germany)
one might need no cycles in the three winter months and so the number of necessary cycles reduces to about 4,000. We therefore give the
electricity costs for a cycle life time limited to 5,000 cycles in the first column. When one uses the storage system also for reserve power
or connects it additionally to a PV system to a small combined heat and power plant, one might need more cycles. Therefore, we give the
lower costs also for the high cycle numbers given by some manufacturers in the second column.
Max. efficiency, generator - battery - appliances (%): The calculated efficiencies only show an excerpt of how efficiently the systems
work, as there are many different operation modes, which are weighted in real world operation. The calculated efficiencies do not take bat-
tery losses into account as there is no reliable standard for determining the degree of battery efficiency.
* in column“Max. efficiency”, system efficiency is not calculated; it is directly specified, including battery losses.
For support and the design of the storage survey, we wish to thank Martin Rothert (SMA), Olaf Wollersheim (KIT), and Andreas Piepenbrink
(E3/DC).
Storage Special
| www.pv-magazine.com18
Gildemeister
presents the
CellCube
German energy
solutions provider
Gildemeister has recently unveiled to
the market a new vanadium redox flow
large-scale storage system called Cell-
Cube. The CellCube has been designed
to combine peak shaving and emer-
gency power supply for system owners,
boasting the capability to scale to multi-
hour and multi-MW scale storage. The
CellCube can operate in parallel to the
grid and is compatible with all types of
20
Mossau’s Blue
Hamster storage
system
Germany’s Mossau
Energy’s new energy
storage system – the Blue Hamster – can
be scaled to suit a range of solar PV
applications, from a private residential
system right up to a 72 kWh commer-
cial-scale application. The Blue Hamster
is a self-sufficient power supply that is
composed of two different storage sys-
tems: a short-term system and a long-term
system. The short-term system provides
energy during times of peak demand,
while a fully-charged long-term system
converts excess energy into hydrogen
that can be stored in permanent tanks
and, when required,
can be transformed
into thermal energy.
What’s in store?
A two-tier battery
storage system, the
Blue Hamster delivers
energy all day long via
its short-term store,
and can convert excess
energy into hydro-
gen via its long-term
store application, thus
delivering supportive
heating for the home.
19
18
ABB’s REACT
residential
storage system
New from Swiss-head-
quartered power and
electronics company ABB is the REACT
–3.6/4.6-TL residential energy storage
system, which represents a further evo-
lution of the company’s storage offer-
ing. The Renewable Energy Accumulator
and Conversion Technology (REACT)
is available in a 3.6 kWh or 4.6 kWh
model, and comprises a single-phase
ABB inverter and lithium-ion battery
delivering 2 kWh of usable energy. The
storage component has been designed
for a long life-cycle, with expected bat-
tery life of around ten years, making it
a good solution for typical residential
PV applications. An integrated Ethernet
port allows for remote or local monitor-
ing without the need for any additional
interfaces.
What’s in store? The REACT resi-
dential energy storage system can be
expanded by additional battery modules,
up to 6 kWh of usage energy, making
it compatible for larger residential PV
renewable energy systems, including PV.
According to Gildemeister, the system
delivers high levels of safety and unlim-
ited cycling, as well as fast reaction times
that makes it an ideal solution for com-
mercial customers in need of a reliable
and flexible storage and backup energy
supply.
What’s in store?
The vanadium redox flow battery is 100%
capable of deep discharge cycles and
offers up to 80% efficiency. The CellCube
is also a complete turnkey product, thus
ensuring ease of installation and opera-
tion for time-poor system owners.
systems. The system also has an auxiliary
AC back-up output for off-grid capabil-
ity during power outages.

2120
Company Product Approx.
customer
price,
exc. VAT
Batteryconnection
Solarinverter:nominalpower(kWh)
Battery
converter
Uninterruptedpowersupply
UsableforReservepower
No-loadconsumption
Battery
Calculated by
pv magazine
Withbattery(€)
(**withoutbattery)
Datatakenfromindependent
onlineshops
Numberofphases
Max.dischargecapacity(kW)
Usablebatterycapacity(kWh)
(batteryinc.indelivery)
Expandableupto(kWh)
Type
Min.cyclicservicelifeaccording
todesign
Max.efficiency,generator-
battery-appliances(%)
Costofstoredelectricity(€/kWh);
servicelifelimitedto5,000cycles
cyclicservicelifeasgivenby
manufacturer
Costperusablebatterycapacity
(€/kWh)
ABB Automation React 4.6 DC 4.6 1 1.8 2 6 Li 4500 *96.6
ABN Braun
Unterbauschrank AC 3 4 yes 50 3.2 LiFePo4 5000 89.3
Standbauschrank AC 1 4 yes 50 5.2 LiFePo4 5000 89.3
ads-tec SRS2025 AC 3 20 yes 20 Li 7000
Akasol
neeoQube (SMA) 7150 AC 1 to 3 15 yes 6 4.4 Li 5000 89.4 33 33 1625
neeoQube (Nedap) 7150 DC/AC 5.5 1 15 yes 6 4.4 Li 5000 28 28 1400
8990 AC 1 to 3 12 yes 6 4.4 Li 5000 89.4 41 41 2043
neeoSystemTyp 2 15790 AC 1 to 3 16.4 yes 12 8.8 Li 5000 89.4 36 36 1794
neeoSystemTyp 5 36790 AC 1 to 3 16.4 yes 30 22 Li 5000 89.4 33 33 1672
AlphaESS
AlphaESS Storion 3 Batterie 8200 DC/AC 3 1 3 yes 30 4 12 Li 6000 83.7 38 32 1915
AlphaESS Storion 5 Batterie 9100 DC/AC 5 1 5 yes yes 50 4 12 Li 6000 88.8 41 34 2050
ASD Sonnenspeicher
Hybrid DC DC 3 5 yes 15 - 60 10.75 LiFePo 3000 *88
Hybrid AC AC 3 5 yes 15 - 60 10.75 LiFePo 3000 *88
BayWa r.e. Solar
Energy Systems
*See online for exact
product description
SMA Sunny Island, LG Chem* 7500 AC 1 5 yes 18 5.7 11.5 Li 6000 88 26 22 1316
SMA Sunny Island, SONY* AC 1 2.3 yes 18 4.32 6000
SMA Sunny Island, SONY* AC 1 3.3 yes 18 4.32 8.64 6000
SMA Sunny Island, SONY* AC 1 4.6 yes 26 8.64 6000
3 x SMA Sunny Island, SONY* AC 3 13.8 yes 78 17.28 6000
SMA Sunny Island, Hoppecke* AC 1 2.3 yes 18 3.2 4 2500
SMA Sunny Island, Hoppecke* AC 1 3.3 yes 18 4 5.5 2500
SMA Sunny Island, Hoppecke* AC 1 4.6 yes 26 8 11 2500
SMA Sunny Island, Hoppecke* AC 3 13.8 yes 78 32.7 Pb-Gel 2800
SMA Sunny Boy 3600 SE DC 3.6 1 2 i.V. 2 Li 5000
SMA Sunny Boy 5000 SE DC 5 1 2 i.V. 2 Li 5000
ENGION FAMILY - 3,7 kWh AC 3 1.3 3.3 LiFePo 6000
ENGION FAMILY - 8,3 kWh AC 3 3 7.5 LiFePo 6000
ENGION FAMILY - 13,8 kWh AC 3 4 12.4 LiFePo 6000
Fronius Symo Hybrid 3.0 DC/AC 3 3 6.4 yes 50 3.6 9.6 LiFePo 8000 *90
PIKO BA System Pb DC 10 3 2.7 yes opt. Pb-Gel 2500
PIKO BA System Li* DC 6,8,10 3 4.7 yes opt. 3.24 8.64 Li 6000
BMZ ESS 3.0 1 to 3 17 yes 5 60 Li 5000 87.5
BYD/Fenecon
MINI ES 5500 AC 3 1 3 opt. 30 3 9 LiFePo 6000 *84 37 31 1833
PRO Compact 11000 DC 3 1 3 yes 40 8.5 LiFePo 7500 *89 25 16 1231
PRO Hybrid 13500 DC/AC 9 3 9 yes yes 80 8.5 25.5 LiFePo 7300 *89 28 19 1398
Deutsche
Energieversorgung
SENEC.Home 8.0 Pb 7990 AC 1 2.5 yes yes 20 8 56
Pb-
liquid
3200 89.3 31 31 999
SENEC.Business 30.0 Pb 21990 AC 3 7.5 yes yes 40 30 210
Pb-
liquid
3200 89.3 23 23 733
SENEC.Home 4.0 Pb 5490 AC 1 1.25 yes yes 20 4 28
Pb-
liquid
3200 89.3 43 43 1373
SENEC.Home 16.0 Pb 12790 AC 2 5 yes yes 25 16 112
Pb-
liquid
3200 89.3 25 25 799
SENEC.Home 5.0 Li 7490 AC 1 1.25 yes yes 28 5 35 Li 5000 30 30 1498
SENEC.Home 7.5 Li 9990 AC 1 1.88 yes yes 30 7.5 52.5 Li 5000 27 27 1332
SENEC.Home 10.0 Li 12490 AC 1 2.5 yes yes 32 10 70 Li 5000 25 25 1249
Durion Energy
CS 8/12 24900 AC 3 8 opt. yes 25 9 Li 7000 89.4 55 40 2767
CS 12/25 28900 AC 3 12 opt. yes 25 17.9 Li 7000 89.4 32 23 1615
CS 16/25 29900 AC 3 16 opt. yes 25 17.9 Li 7000 93.2 33 24 1670
CS 16/37 41900 AC 3 16 opt. yes 25 26.9 Li 7000 93.2 31 22 1558
CS 16/49 50900 AC 3 16 opt. yes 25 35.8 Li 7000 93.2 28 20 1422
CS 16/61 54900 AC 3 16 opt. yes 25 44.8 Li 7000 93.2 25 18 1225
CS 36/49 60900 AC 3 36 opt. yes 35 35.8 Li 7000 93.2 34 24 1701
CS 36/61 66900 AC 3 36 opt. yes 35 44.8 Li 7000 93.2 30 21 1493
CS 36/86 79900 AC 3 36 opt. yes 35 62.7 Li 7000 93.2 25 18 1274
CS 55/123 119900 AC 3 55 opt. yes 45 89.6 Li 7000 93.2 27 19 1338
customer
price,
exc. VAT
Batteryconnection
Battery
converter
No-loadconsumption
Battery
Calculated by
pv magazine
Withbattery(€)
(**withoutbattery)
onlineshops
Numberofphases
Expandableupto(kWh)
Type
todesign
manufacturer
(€/kWh)
E3/DC
S10 MINI All In One
** from
8000
- DC/AC 4.6 1 1.5 yes i.V. 40 2.12 8.46 Li 4500 *88 **75 **75 **3383
S10 E12 All In One
** from
10500
- DC/AC 12 3 3 yes i.V. 40 4.23 12.7 Li 4500 *88 **44 **44 **1972
Eon
Sunny Boy 3600 Smart Energy DC 3.6 1 2 i.V. 18 2 Li 5000 92.5
Sunny Boy 5000 Smart Energy DC 5 1 2 i.V. 18 2 Li 5000 92.5
KNUT® basiX / 5,5 kWh AC 3 3 yes 12 4.4 8.8 LiFePo 5000 84.8
KNUT® basiX / 11 kWh AC 3 3 yes 12 8.8 8.8 LiFePo 5000 84.8
ET SolarPowerGmbH
ET EnergieS-Nano-DC10® 1499 DC 1 0.25 0.8 LiFePo 80 1874
ET EnergieS-Nano-AC10® 1799 AC 1 0.25 0.8 LiFePo 78 2249
ET EnergieS-Tiny® 4999 AC 1 0.9 2 LiFePo 83 2500
ET EnergieS-Tiny-PLUS® 6250 AC 1 1.2 3.65 LiFePo 83 1712
ET EnergieS-Tiny-MAX® 10350 AC 1 2.6 7.3 LiFePo 83 1418
ET EnergieS-Li® 9850 AC 1 2.6 4 8 LiFePo 83 2463
ET EnergieSL-Li® 13950 AC 1 4 7.3 14.6 LiFePo 83 1911
ET EnergieS3-Li® 19850 AC 3 7.8 8 16 LiFePo 83 2481
ET EnergieS3L-Li® 27950 AC 3 12 14.6 29.2 LiFePo 83 1914
ET EnergieS3LX-Li® 59850 AC 3 24 43.8 58.4 LiFePo 83 1366
ET EnergieS® 7490 AC 1 2.6 4.4 8.8 Pb-Gel 2500 76 68 68 1702
ET EnergieSL® 10980 AC 1 4 8.8 17.6 Pb-Gel 2500 76 50 50 1248
ET EnergieS3® 14980 AC 3 7.8 8.8 17.6 Pb-Gel 2500 76 68 68 1702
ET EnergieS3L® 22980 AC 3 12 17.6 17.6 Pb-Gel 2500 76 52 52 1306
ET EnergieS3LX® 35980 AC 3 24 28.8 57.6 Pb-Gel 3500 76 36 36 1249
Fischer (www.
sonnen-fischer.de)
product description
Sunny Boy 5000 Smart Energy DC 5 1 2 2 Li 4000
PIKO BA System 11760 x DC 10 3 2.7 5.8 Pb-Gel 2500 *88 69 69 1717
Sunny Island, EnerSys Home* AC 1 6 no 4.6 4.6 Pb 2500
Sunny Island,Hoppecke* AC 1 4.6 432 Pb 2500
Sunny Boy 3600 Smart Energy DC 3.6 1 2 2 Li 4000
Sunny Island, EnerSys Home* AC 1 12 9.2 9.2 Pb 2500
Sunny Island, Akasol
neeoQube*
AC 1 4.6 432 Li 3000
Sunny Island, Hoppecke* AC 1 6 432 Pb 2500
Sunny Island 6.0H, AC 1 6 432 Li 3000
3 x Sunny Island,Hoppecke AC 3 13.8 432 Pb 2500
3 x Sunny Island 8.0H,
Hoppecke
AC 3 18 432 Pb 2500
Fronius International
Fronius Symo Hybrid 3.0 7600 x DC/AC 3 3 6.4 yes 50 3.6 9.6 LiFePo 8000 *90 39 25 1961
HycubeTechnologies
Hycube eActive S 8590 DC/AC 4.6 1 5 yes
from
Q4
3.84 11.52 Li 4000 82.8 51 51 2021
Hycube eActive M 9999 DC/AC 4.6 1 5 yes
from
Q4
5.76 11.52 Li 4000 82.8 40 40 1592
Hycube eActive L 11990 DC/AC 4.6 1 5 yes
from
Q4
7.68 11.52 Li 4000 82.8 36 36 1453
Hycube eActive XL 13449 DC/AC 4.6 1 5 yes
from
Q4
9.6 11.52 Li 4000 82.8 33 33 1315
Hycube eActive XXL 14890 DC/AC 4.6 1 5 yes
from
Q4
11.52 Li 4000 82.8 31 31 1221
IBC Solar
* See online version
Set IBC SolStore Li*
from
6800
AC 42064 2.2/18 yes 26 4.7 56.4 Li 5000 87.5 29 29 1447
Set IBC SolStore Pb*
from
7900
AC 42064 2.2/18 yes 26 4
unlim-
ited
Pb-Gel 2700 87.5 73 73 1975
KACO new energy
More systems in full
online version
product description
Powador-gridsave 1,35kWh* 10000 DC 6.4 1 3.3 1,215 Li 4000 90.9 182 182 7282
Powador-gridsave 2,70kWh* 11100 DC 6.4 1 3.3 2.43 Li 4000 90.9 102 102 4094
Powador-gridsave 5,40kWh* 13300 DC 6.4 1 3.3 4.86 Li 4000 90.9 62 62 2500
Powador-gridsave 6,75kWh* 14400 DC 6.4 1 3.3 6,075 Li 4000 90.9 55 55 2181
Powador-gridsave 1,35kWh* 10100 DC 8 1 3.3 1,215 Li 4000 90.9 178 178 7128
Powador-gridsave 2,70kWh* 11200 DC 8 1 3.3 2.43 Li 4000 90.9 100 100 4016

2322
customer
price,
exc. VAT
Batteryconnection
Battery
converter
No-loadconsumption
Battery
Calculated by
pv magazine
Withbattery(€)
(**withoutbattery)
onlineshops
Numberofphases
Expandableupto(kWh)
Type
todesign
manufacturer
(€/kWh)
KACO new energy
online version
product description
Powador-gridsave eco
(1-phasig)
AC 1 5 yes 89.4
Powador-gridsave eco
(3-phasig)
AC 3 15 89.4
KNUBIX GmbH
KNUT® 3.3 / 5,5 kWh 13490 AC 3 7.5 yes yes 60 4.4 26.4 LiFePo 5000 81.2 61 61 3066
KNUT® 3.3 / 11 kWh 16990 AC 3 7.5 yes yes 60 8.8 26.4 LiFePo 5000 81.2 39 39 1931
KNUT® basiX / 5,5 kWh 8990 AC 3 3 yes 12 4.4 8.8 LiFePo 5000 84.8 41 41 2043
KNUT® basiX / 11 kWh 12490 AC 3 3 yes 12 8.8 8.8 LiFePo 5000 84.8 28 28 1419
KOSTAL Solar Electric
PIKO BA System Pb DC 10 3 2.7 yes opt. 44105 0.5 Pb-Gel 2500 *88
PIKO BA System Li DC 6 3 4.7 yes opt. 44105 0.9 8.64 Li 6000 98
Leclanché TiBox 6160 AC 3 3.2 yes i.V. 25 3.2
6.4
/9.6
Li 15000 39 32 1925
LITRON GmbH
SUN Solarstrom-Speicher
2600
8200 AC 1 ca. 2.0 opt. 20 3.58 20.48 LiFePo 5000 86 46 46 2292
4000
8600 AC 1 ca. 3.5 opt. 21 3.58 20.48 LiFePo 5000 86 48 48 2402
2600
8200 AC 1 ca. 2.0 opt. 20 3.58 20.48 LiFePo 5000 86 46 46 2291
4000
8600 AC 1 ca. 3.5 opt. 20 3.58 20.48 LiFePo 5000 86 48 48 2402
MSTE Solar
MSTE POWERHOME®S 8000
DC-
Gen
1 to 3 1.5 25 3.24 Li 5000 49 49 2469
MSTE POWERHOME®M 9800
DC-
Gen
1 to 3 1.5 25 4.32 Li 5000 45 45 2269
MSTE Solar MSTE POWERHOME®L 11500
DC-
Gen
1 to 3 1.5 25 5.4 Li 5000 43 43 2130
Nedap Energy
Systems
online version
product description
PowerRouter PR50SB/S240
3894
(o.B.)
DC 5 1 5 yes yes 16 86.5
PowerRouter PR37SB/S240
3174
(o.B.)
DC 3.7 1 3.7 yes yes 16 86.5
PowerRouter PR37SBi/S480
3390
(o.B.)
DC 3.7 1 3.7 yes yes 16 86.5
PowerRouter Plus/ RESU64* 7917 DC 3.7 1 3.7 yes yes 5.76 11.52 6000 25 21 1259
PowerRouter Plus/ RESU64* 8427 DC 5 1 5 yes yes 5.76 11.52 6000 26 22 1307
PowerRouter Plus Unifit/
RESU64*
7197 AC 3.7 1 3.7 yes yes 5.76 11.52 6000 25 21 1249
PowerRouter Plus Unifit/
RESU64*
7359 AC 5 1 5 yes yes 5.76 11.52 6000 26 21 1278
Neovoltaic
Flex AC 6900 4.5 1 yes yes 4 4 8000 93 35 22 1725
Flex DC 6900 4.5 1 yes yes 8 8 8000 35 22 1725
Dynamic 3p AC 9900 10 3 yes yes 8 40 8000 91 25 15 1238
Dynamic 3p DC 9900 10 3 yes yes 8 40 8000 91 25 15 1238
PEUS-Testing
online version
ESS 10.0 11400 AC 3 6 yes 20 8.16 16.32 LiFePo 6000 90.3 28 23 1397
ESS 12.0 13000 AC 3 6 yes 20 9.792 16.32 LiFePo 6000 90.3 27 22 1328
ESS 15.0 15560 AC 3 6 yes 20 12.288 24,576 LiFePo 6000 90.3 25 21 1266
ESS 17.0 17080 AC 3 6 yes 20 13.824 24,576 LiFePo 6000 90.3 25 21 1236
ESS 23.0 21640 AC 3 6 yes 20 18.24 24,576 LiFePo 6000 90.3 24 20 1186
ESS 25.0 23400 AC 3 6 yes 20 20.48 61.44 LiFePo 6000 90.3 23 19 1143
ESS 35.0 34100 AC 3 18.5 yes 20 28,672 61.44 LiFePo 6000 90.3 24 20 1189
ESS 40.0 38100 AC 3 18.5 yes 20 32,768 61.44 LiFePo 6000 90.3 23 19 1163
ESS 50.0 46100 AC 3 18.5 yes 20 40.96 61.44 LiFePo 6000 90.3 23 19 1125
PHONO SOLAR Phonocube 7.2 8500 DC 7.2 3 7.2 yes 10 6.7 LiFePo 6000 88.7 22 18 1075
Proton Motor
(Spower)
SP BS 3000 15,4 kWh 6850 DC 3 1 3 9 Pb-Gel 2500 28 28 701
SP BS 10 30,8 kWh 14645 DC 10 3 10 15 Pb-Gel 2500 34 34 856
Q3 Energie Q_BEE 4.0 Li AC 1 1.5 i.P. 3.6 10.8 Li 83 2778
customer
price,
exc. VAT
Batteryconnection
Battery
converter
No-loadconsumption
Battery
Calculated by
pv magazine
Withbattery(€)
(**withoutbattery)
onlineshops
Numberofphases
Expandableupto(kWh)
Type
todesign
manufacturer
(€/kWh)
REFUenergy
product description
REFUrack, on-grid, RR* AC 3 18 11 264 LiFePo 6000 85.7
REFUrack, on-grid und
off-grid, RR*
AC 3 40 11 264 LiFePo 6000 85.7
REFUrack, off-grid, RR* AC 3 44 22 264 LiFePo 6000 85.7
REFUrack, off-grid, RR* AC 3 150 88 264 LiFePo 6000 85.7
REFUtower DC 2 to 24 1 and 3 24 yes 22.2 Li 6000
Rusol
Pro 4.0 8800
DC-
Gen
1 3.1 9.2 LiFePo 5000 93.5 57 57 2839
Pro 8.0 12400
DC-
Gen
1.5 6,2 9.2 LiFePo 5000 93.5 40 40 2000
Pro 12.0 16000
DC-
Gen
2 9.2 9.2 LiFePo 5000 93.5 35 35 1739
RWE Effizienz
RWE Storage basic 5 6390 AC 3 13.8 2.4 Pb-Gel 2500 88.8 107 107 2663
RWE Storage basic 12 8490 AC 3 13.8 6 Pb-Gel 2500 88.8 57 57 1415
RWE Storage vario mini 12100 AC 3 2.8 2.5 6.21 Li 8000 89.4 97 61 4840
RWE Storage vario S 12770 AC 3 1.3 - 4 4.1 12.4 Li 8000 89.4 62 39 3115
RWE Storage vario M 15000 AC 3 1.3 - 4 5.4 12.4 Li 8000 89.4 56 35 2778
RWE Storage vario L 21500 AC 3 4 9.1 12.4 Li 8000 89.4 47 30 2363
RWE Storage eco 4.5 6300 AC 1 2.5 opt. 30 3.5 10.5 LiFePo 5000 89.4 36 36 1800
RWE Storage eco 9.0 10300 AC 1 3 opt. 30 7 10.5 LiFePo 5000 89.4 29 29 1471
RWE Storage eco 13.5 14300 AC 1 3.5 opt. 30 10.5 10.5 LiFePo 5000 89.4 27 27 1362
Samsung SDI
3.6kWh All-in-One DC 4.6 1 2 3.24 86.5 41 34 2059
5.5kWh All-in-One DC 4.6 1 2 5 86.5
8kWh All-in-One DC 8 3 3 7.2
Schmid Energy
Systems
EverFlow - Compact Storage AC 1 3.5 i.P. 50 6.7 10000 65.3
EverFlow - Compact Storage AC 1 5 i.P. 50 10 10000 65.3
Shenzhen Growatt
New Energy
Techology
4320 DC 2 to 6 1 2 4 Li 4000 94 23 23 900
sia energy
Pro 4.0 8800
DC-
Gen
1 3.1 9.2 LiFePo 5000 94 57 57 2839
Pro 8.0 12400
DC-
Gen
1.5 6.2 9.2 LiFePo 5000 94 40 40 2000
Pro 12.0 16000
DC-
Gen
2 9.2 9.2 LiFePo 5000 94 35 35 1739
Pro 20.0 34000
DC-
Gen
4 15.4 23.2 LiFePo 5000 94 44 44 2208
Pro 30.0 45000
DC-
Gen
6 23.2 23.2 LiFePo 5000 94 39 39 1940
SMA Solar
Technology AG
Sunny Island 6.0H, einphasig AC 1 4.6 yes i.V. 26 432 89.7
Sunny Island 8.0H, einphasig AC 1 6 yes i.V. 26 432 89.7
dreiphasig
AC 3 13.8 yes i.V. 78 432 89.7
dreiphasig
AC 3 18 yes i.V. 78 432 89.7
Sunny Island 3.0M, einphasig AC 1 2.3 yes i.V. 18 432 88.9
Sunny Island 4.4M, einphasig AC 1 3.3 yes i.V. 18 432 88.9
3 x Sunny Island 3.0M,
dreiphasig
AC 3 6.9 yes i.V. 54 432 88.9
3 x Sunny Island 4.4M,
dreiphasig
AC 3 9.9 yes i.V. 54 432 88.9
Sunny Boy 3600 Smart Energy
from
4400
x DC 3.6 1 2 i.V. 18 2 Li 5000 *92.5 38 38 1850
Sunny Boy 5000 Smart Energy
from
4600
x DC 5 1 2 i.V. 18 2 Li 5000 *92.5 37 37 1050
Solarwatt MyReserve 500 4620
DC-
Gen
42064 1.5 5 4.4 11 Li 4100 *93 26 26 1050

2524
customer
price,
exc. VAT
Batteryconnection
Battery
converter
No-loadconsumption
Battery
Calculated by
pv magazine
Withbattery(€)
(**withoutbattery)
onlineshops
Numberofphases
Expandableupto(kWh)
Type
todesign
manufacturer
(€/kWh)
SolarWorld
SunPac LiOn 5 AC 1 1.8 yes 5 10 Li 5000 85.7
SunPac LiOn 10 AC 1 1.8 yes 10 Li 5000 85.7
SunPac LiOn AC 1 3 yes 10 Li 10000
SunPac 2.0 DC 10 3 2.85 yes 5.8 11 Pb-Gel 2500
Solutronic Energy
Solenergy Storage DC 40 7000 DC 3 1 2.5 yes yes 30 2.5 16 LiFePo 5000 85.7 52 52 2584
Solenergy Storage AC 25 6800 AC 1 2.5 yes yes 30 2.5 16 LiFePo 5000 88.5 54 54 2720
Sonnenbatterie
More systems in
full online version
Sonnenbatterie eco 4 AC 1 2.5 yes yes 30 4 16 LiFePo 10000 89.4
Sonnenbatterie eco 6 AC 1 3 yes yes 30 6 16 LiFePo 10000 89.4
Sonnenbatterie eco 8 11300 AC 1 3.3 yes yes 30 8 16 LiFePo 10000 89.4 28 14 1413
Speicherkraft
Energiesysteme
More systems in
full online version
HSR DTyp 3,36/6.0 (Basis) 8940 DC 7.5 3 7.5 3.46 6.72 Pb 1800 80 122 122 2194
HSR DTyp 3,36 / 15 12824 DC 15 3 15 3.46 6.72 Pb 1800 80 163 163 2926
HSRLi/DTyp 4,03 / 7.5 13410 DC 7.5 3 7.5 4.03 17.28 LiFePo 5000 95 60 60 2993
HSRLi/DTyp 4,03 / 12.5 18932 DC 15 3 15 4.03 17.28 LiFePo 5000 95 81 81 4028
HSRLi/DTyp 6,72 / 7.5 15959 DC 7.5 3 7.5 6.72 LiFePo 5000 95 43 43 2174
HSRLi/DTyp 6,72 / 12.5. 21481 DC 15 3 15 6.72 LiFePo 5000 95 56 56 2795
HSRLi/DTyp 13,44 / 7.5 23909 DC 7.5 3 7.5 13.44 LiFePo 5000 95 34 34 1678
HSRLi/DTyp 13,44 / 12.5 29431 DC 15 3 15 13.44 LiFePo 5000 95 40 40 1989
HSRLi/DTyp 20,16 / 12.5 37381 DC 15 3 15 20.16 LiFePo 5000 95 34 34 1720
Basic 1,1 / 0,6 1680 DC 0.6 1 0.6 1.1 Pb 1200 94 119 119 1429
Basic 1,1 / 1,5 1950 DC 1.5 1 1.5 1.1 Pb 1200 94 127 127 1527
Basic 2,2 / 4,5 3920 DC 4.5 1 4.5 2.2 Pb 1200 94 118 118 1414
Basic 4,4 / 4,5 5250 DC 4.5 1 4.5 4.4 PB 1200 94 84 84 1009
Tesvolt
More systems in
full online version
Li 10 AC 42064 4.2 opt. i.P. 10 7.2 9.2
Li 20 AC 42064 18 opt. i.P. 10 14.3 18.4
Li 30 AC 42064 18 opt. i.P. 10 21.5 27.6
Li 60 AC 3 54 yes i.P. 10 43 55.3
Li 120 AC 3 72 yes i.P. 10 86 110.6
VARTA Storage
Engion Home 2,8 - 6,9 kWh AC 3 2.4 yes yes 35-50 2.5 6.21 Li 14000 89.4
Engion Family 3,7 bis 13,8 AC 3 4 yes yes 35-65 3.3 12.4 Li 14000 89.4
Engion Element 3 AC 3 1.6 35 2.9 Li 6000 89.4
Engion Element 6 AC 3 2 35 5.8 Li 6000 88.1
ViessmannWerke
Stromspeichersystem LAA AC 1 4.6 yes 4.4 5000 89.4
Stromspeichersystem LVA AC 3 4 yes 3.3 12.4 8000 88.1
Stromspeichersystem BHA AC 1 4.6 yes 3.7 2700 88.1
Stromspeichersystem BHB AC 1 4.6 yes 7.4 2700 93.1
Piko BA System DC 11 3 yes 5.8 2500
Fronius Energy Package DC/AC 4 3 4 yes 3.6 8000
Wemag
ReeVOLT!-3-2.5 AC 11.5 1 4.16 yes 40 4.5 Li
leasing
model
ReeVOLT!-3-5.2 AC 11.5 1 4.16 yes 10 10.107 Li
leasing
model
The li-ion’s share
Large-scale storage: Demand for large-scale, stationary storage is being driven by
a combination of greater solar penetration and technical improvements within the
industry. But which battery technology is most adept at meeting the storage needs of
utilities and commercial-scale players?
When SolarCity co-founder and Tesla
Motors owner Elon Musk told an audi-
ence in Detroit last year that “solar and
utilities can coexist”, who was anyone to
argue? The middle ground between solar
and utilities is being occupied by a grow-
ing number of progressive providers in
Europe and the U.S., with large-scale bat-
tery storage following suit, expanding to
the edges to bridge the two poles.
For post-peak PV markets such as Ger-
many, the storage evolution is bringing
secondary value to a typical solar system,
while in the soaring solar sectors of the
U.S., China and Japan – as well as emerg-
ing markets in Latin America, the Middle
East and Europe – the benefits of batter-
ies are hungrily anticipated.
As with all emergent technologies,
issues of cost, adoption and regulatory
support abound, all underpinned by
the question: just which type of battery
technology is best-suited for storage at
volumes necessary to catapult the solar
industry to energy’s apex?
The value of lithium-ion
The most commercially proven battery
technology at grid-scale is lithium-ion
(li-ion). While not necessarily the most
cost-effective, li-ion technology has dem-
onstrated the fewest limitations and pos-
sesses by far the most in-depth volume of
quantifiable performance data under its
belt. “There are other battery technolo-
gies besides li-ion that are still commer-
cially unproven that could end up being
cheaper,” Ravi Manghani, senior energy
storage analyst at GTM Research told
pv magazine. “If you look at pumped
hydro, it is by far the cheapest technology
for bulk energy storage, but it has limita-
tions in terms of its location and the type
of benefits it can provide.”
Based on value rather than cost, li-ion
batteries provide wider benefits, and have
proven capable of satisfying the demands
of most large-scale consumers on matters
of safety, efficiency and performance flex-
ibility, proving adept at delivering load
shifting capabilities, demand charge
management and island mode. “These
aspects are all key drivers behind gen-
eral technical innovation in the battery
This 1 MW NAS battery system has been developed by Germany’s Younicos and installed at a technology center in
Berlin to deliver storage capacity at large scale.
Photo:Younicos

2726
to supply a greater share of the stationary
and large-scale storage market, believes
Goldie-Scot.
“The Gigafactory’s manufacturing
volume will provide economies of scale
regardless of the cell format,” he said.
“The factory could also host multiple pro-
duction lines and manufacture a range
of cell formats. But with no other auto-
maker using cylindrical format cells, if
Tesla’s sales are weaker than expected
then a wholesale switch to large format
manufacturing could make sense.”
Alternative large-scale tech
Neither GTM Research’s Manghani nor
BNEF’s Goldie-Scot believe that li-ion
batteries will be muscled out of the large-
scale sector any time soon, but both agree
that alternative technologies are exhibit-
ing a great deal of potential.
“Some flow battery technologies –
such as the vanadium flow batteries
being developed by Imergy – have the
potential to be more cost-competitive
than li-ion, but they are at least one-to-
two years away from proving themselves
commercially,” said Manghani. The ana-
lyst added that proponents of flow tech-
nologies must undertake more pilot proj-
ects and build up a bank of operational
and performance data in order to con-
vince utilities, customers and financiers
that this alternative technology is viable
and reliable.
“On paper, flow batteries are cheaper
than li-ion, but the technology needs to
move beyond proof of concept,” stressed
Manghani. “There have been concerns
about lifetime operating costs of flow
batteries, given their use of mechanical
components.” Manghani also has reser-
vations about the efficacy of lead acid bat-
teries at backup power scale, citing low
efficiency and shorter cycle life as draw-
backs when compared to li-ion batter-
ies. “But lead acid batteries do have that
mature industry infrastructure to fall
back on, and their cost is favorable to li-
ion,” he added.
“Although there is a large potential
market for all of the different storage
technologies – since many can often per-
form the same application – we expect li-
ion to remain the preferred technology at
large scale, at least for the next five years,”
said Goldie-Scot. The ability of vanadium
flow batteries to operate for 20 years or
more with few replacements is often cited
as a reason why the technology is proving
attractive for utilities. California-based
flow developer Imergy contends that its
recently launched ESP30 series is the
perfect storage option at large scale, able
to outperform li-ion batteries in terms
of renewables management, microgrid
implementation, emergency back-up
power, peak shaving and frequency regu-
lation. The non-toxic nature of vanadium
makes it a safer option than either li-ion
or lead acid, and Imergy claims that its
unique chemistry removes the need for
consumers to replace electrolytes, mak-
ing it more scalable.
“For anything that needs long-dura-
tion storage, the flow battery will win
every time, simply because it can provide
short duration cycles, for the stability,
and can also do long duration,” Imergy
CEO Bill Watkins told pv magazine last
year. “None of the li-ion manufacturers
talk about mid-balance – you want to
be able to charge and discharge, which
means you have to be below full. And if
you hold a li-ion battery below full for
long periods, it just dies. A flow battery
can operate in that middle band without
any impact for any number of cycles.”
Leading markets for large storage
Battery storage at residential scale is
already playing a leading role in the tran-
sition of the energy system. Self-con-
sumption models and supportive stor-
age policies are shaping Germany’s solar
landscape 2.0, and while market design in
many other leading solar countries needs
to evolve further – such as in the U.S.
states where net metering is the promi-
nent PV driver – the discussion is at least
brisk.
At the grid scale, however, the storage
market has thus far demonstrated little of
the dynamism evident in the residential
sphere. The markets of North America,
Japan and South Korea lead the way in
large-scale storage penetration, where the
sector has developed largely along coun-
try-specific parameters.
“In California there is a 1.3 GW stor-
age procurement mandate by 2020,”
said Goldie-Scot. “FERC jurisdictions
resolutions 755 and 784 have helped to
reward energy storage’s participation in
the market.” For Japan and South Korea,
it is a combination of government sup-
port and a pro-storage marketplace that
has boosted investment in the sector,
while China already plays an important
role in manufacturing batteries for con-
sumer electronics, and its role in station-
ary energy storage will no doubt grow,”
added Goldie-Scot. “However, we believe
that some of the large South Korean and
Japanese corporations will remain the
most influential.”
In countries with high levels of solar
penetration – such as Germany and Aus-
tralia – large-scale storage can alleviate
some of the wholesale market concerns
and improve uptake of self consumption,
adds Manghani. “For utilities operating
in these countries, storage coupled with
solar is a much better resource to man-
age, with ramp control, time-shifting and
smoothing capability.” S Ian Clover
Photo:Imergy
Photo:ASDSonnenspeicher
A vanadium-flow battery, the ESP30 series from California’s Imergy is a non-toxic alternative to li-ion
that its makers claim also delivers better renewable management and microgrid implementation.
ASD Sonnenspeicher is a developer of battery technology from Germany, and will shortly roll out to the
large-scale market its PACADU system based on LFP and LTO technology.
storage space, and are the reasons why
li-ion technology has picked up the bulk
of market share,” said Manghani. “With
much higher energy density compared to,
say, lead acid, li-ion reduces the footprint
and all costs associated with system size.”
Li-ion’s operational viability marks
it out as the preferred technology for
the majority of new storage project
announcements. Where once sodium
sulphur batteries were the option of
choice for large-capacity projects, today
it is li-ion that leads the field.
“With li-ion batteries, there is more
proven operational data across multi-
ple projects than any other technology,”
Logan Goldie-Scot, associate for energy
smart technologies at Bloomberg Energy
Finance (BNEF) told pv magazine. “This
is important since it helps alleviate risk.”
The market for li-ion battery produc-
tion is dominated by some of the indus-
try’s largest and most bankable compa-
nies, such as Panasonic, Samsung, SDI,
LG Chem, BYD and Saft. The series of
bankruptcies in the industry between
2010 and 2014 sowed seeds of caution in
the sector, making it more difficult for
smaller companies to gain market accep-
tance. “Developers have since become
focused on the strength of the warranty,
and particularly the company providing
the warranty,” said Goldie-Scott.
New players in the li-ion space
There is scope for smaller companies to
use their innovation to their advantage,
and in February Switzerland’s Alevo
announced a partnership with Custom-
ized Energy Solutions (CES) to deploy
200 MW of li-ion storage to U.S. whole-
sale markets. “This is a company that so
far hasn’t had a single commercial proj-
ect,” said Manghani. The company itself,
however, bullishly labeled the deal the
“largest-ever energy storage deployment
in the U.S.”, although skeptics were quick
to suggest a 261 MW deal struck last year
between Southern California Edison and
AES had preceded it. At a rather smaller
scale but still a potential game-changer
is the creation in late 2014 of a 6 MW
storage project in the U.K. from Berlin,
Germany-based battery software devel-
oper Younicos. Officially Europe’s larg-
est battery storage project, the Smarter
Network Storage (SNS) substation has
a 10 MWh capacity and was developed
with Samsung SDI li-ion batteries at a
cost of $29.3 million.
The role played by Younicos was to
develop custom-built intelligent soft-
ware architecture and components for
the project, which were designed to reg-
ulate power frequency and load-shifting,
and to stabilize the grid more effectively.
“The main advantages of using li-ion
batteries in the SNS project are economic
rather than technical,” Philip Hierse-
menzel of Younicos told pv magazine.
“The technology is the best option for
us on price, longevity and depth of dis-
charge. In this particular case Samsung
SDI produced good cells, which we were
then further able to enhance with our
software, thus ensuring that the battery
lasts 20 years, guaranteed by Samsung.”
EV’s role in li-ion adoption
The large-scale storage industry is evolv-
ing to offer a cost-effective alternative
to expensive peak demand charges that
rapidly empty the pockets of commer-
cial and industrial businesses. In the U.S.,
battery energy storage has emerged as a
useful solution in areas where time-of-
day charges or multiple tier pricing cre-
ates expensive peaks in energy.
Li-ion storage is the go-to tech in such
cases, and costs for stationary energy
storage projects have fallen rapidly in
recent years, making the technology
more competitive at scale. “This push
towards cost reduction has been driven
by developments in the electric vehicle
market,” said Goldie-Scot.
Tesla Motors’ highly anticipated $5 bil-
lion “Gigafactory” – to be built in Sparks,
Nevada – will serve to lower costs for li-
ion batteries globally. Panasonic Corpo-
ration has already confirmed it will invest
heavily in cooperating with Tesla at the
Gigafactory.
“Although not a stated target of Tesla’s,
the company’s published data would have
it on course to produce battery packs at
$220/kWh by 2020,” said Goldie-Scot. “At
BNEF we believe that this target will only
be achieved in the early- to mid-2020s.”
Tesla’s use of 18,650 cylindrical cells
rather than large format cells makes it
unique among automotive companies.
Its flagship Model S. Tesla is built with
such cells, but the company is yet to con-
firm exactly what types of cell format
it will develop at its Gigafactory. “It is
likely,” believes Goldie-Scot, “that Tesla
will manufacture both large format cells
as well as 18,650 cells. Panasonic’s confir-
mation as a partner means the plant will
certainly churn out prismatic cells, and
with Tesla also sourcing roughly 8% of
its cells from Samsung SDI, there is the
chance that large format cell capacity will
increase.”
As the most optimized li-ion cell avail-
able, and at the lowest cost per watt hour
(Wh), the 18,650 cell reached a period
of oversupply in recent years, but Tes-
la’s emergence alleviated the imbalance,
causing surging demand in the past two
years. The gap between large format and
cylindrical cells in terms of energy den-
sity is narrowing, however, and Tesla may
look to pivot away from using cylindrical
format cells at its Gigafactory as it looks

PV Magazine - Special Issue on Storage (2015)

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