GREEN DATA CENTER, Växjö
Partners
Organisation:
Partner’s role:
VEAB
providing district cooling, responsible for the city broadband
BUDGET
11 000 000 SEK
Summary
The Green Data Center was inaugurated October 23, 2012, and is a cooperation between
Wexnet (the broadband city net owned by Växjö Energy), the City of Växjö, the County
Council and companies. Instead of investing in individual server halls, they have created a
common computer center - the Green Data Center, governed by Wexnet. This makes the
Green Data Center a very cost efficient and modern solution, and it is estimated that each
project partner has saved 340 000 € by joining the project, compared to if they would have
built their own server halls.
The Green Data Center is also a good example on how to take use of energy in an efficient
way. Server halls generally need a lot of cooling since the servers generate a lot of surplus
heat. In most cases, this is solved by electric cooling machines. However, in Växjö we have
established a district cooling grid. Cold water is running through pipelines and contributes to
cool down the buildings that are connected to it. The cold water is generated via an absorption
process, which actually means that district heating (from biomass) is transformed to district
cooling.
Anyway, the Green Data Center is connected to the district cooling system and uses the
returning water that has been used for the cooling of the nearby shopping center. Even if it has
already been cooling the shopping center, it is still cold enough to cool down the server halls.
When passing the server halls, surplus heat is transferred from the server halls to the water
pipelines. The now warmer water in the pipelines can however still be used. The pipelines run
beneath the nearby football field, which makes it possible to extend the football season, since
frost the field will not become frosty.
But it doesn’t stop there. Mounted on the roof of the Green Data Center, is a PV plant,
generating electricity that is used for the pumping the water back to the absorption cooling
unit. Another positive consequence of this could be that the Green Data Center contributes to
the visibility of PV plants in our community, which may have the effect that the citizens will
understand even more that solar energy works also in Sweden.
It should be noted that the technology of transforming RES-based district heating to cooling
via absorption, was originally realized in Växjö as a part of the SESAC project under the FP6Concerto initiative.
So, the Green Data Center is one interesting part of the never-ending efforts in Växjö to
reduce the overall energy use, reduce the electricity use and increase the use of renewable
energy. It is a project that fits very well in the general Fossil Fuel Free Växjö policy.
The Green Data Center has won the award for the Greenest Data Hall of Sweden 2012.
Promotional sentence
The Green Data Center in Växjö is a unique example on how energy can be reused for several
purposes in an efficient way, creating environmental and economic benefits for all involved
actors.
Action plan/timeline
In 2009, Wexnet realized that they needed a new server hall, and at the same time it was
obvious that the City of Växjö and the County Council also needed that. The ideas of working
together in one way or another started, but nothing really happened.
When the district cooling system was established in the area, the final idea was born, that it
was possible to take use of the district cooling to also cool the server halls. The contracts were
written in December 2011, and shortly after that the construction phase started. In October
2012, the Green Data center was inaugurated.
Energy and climate achievements
Since the Green Data Center has not been up and running a year yet, the effects are only
estimated, and they are estimated for the full use of the server halls. There are metering
systems in the halls that will give detailed measurements, so that each user will pay their share
of the energy costs etc.
The efficiency of server halls is measured in PUE-quotas, which is the total energy use for the
entire server hall divided by the energy use for the servers. For example, a PUE of 2 means
that the energy used (mainly) for cooling the servers is equal to the energy used for the servers
themselves. PUE can be 1.0 as best. Green Data Center has a maximum server capacity of 350
kW, and is estimated to have reached a PUE of 1.2. Available information from before this
investment shows a PUE of 1.7. This means the following:
Establishing a server hall with the server capacity of 350 kW and a PUE of 1.7, would need
5,212,200 kWh/year. With a realization of the Green Data Center, used to its maximum and
with PUE 1.2 would instead need 3,679,200 kWh/year. This means that the total maximum
reduction of electricity is 1,533,000 kWh (29 % saving). This would probably be achieved
also if the efficiency measures would be carried out in several smaller server halls, but by
combining them, it also generated an economic saving for all partners.
This is the result that is achieved if you still use electric cooling machines. The Green Data
Center is however using district cooling instead of electric cooling, which means that an even
bigger amount of electricity use is avoided. If we assume that 95 % of all the remaining
energy is used for cooling, this equals about 580,000 kWh that are supported by district
cooling instead of electricity.
The PV plant mounted on the roof of the Green Data Center is estimated to generate 17,000
kWh of electricity every year (about 7 % of all PV electricity in Växjö), which does not need
to be produced elsewhere.
This means that totally, Green Data Center reduces the needs for buying electricity by
2,130,000 kWh, and reduces the total energy use by 1,533,000 kWh.
Calculating decreased CO2 emissions due to reduced electricity use is tricky. It depends what
system boundaries you are using. The local electric mix generates about 0,015 kg CO2/kWh,
which means roughly 32 tons for the whole project. At the same time, it is possible to say that
the reduced need for electricity means that there is less need to produce electricity on the
margin in the North European electric market. This means that coal power plants can produce
less, which may emit as much as 1 kg CO2/kWh, or 2,130 tons. Depending on how you see it,
the truth is probably somewhere between these figures.
Beneficiaries/Target groups? Geographical scope?
The Green Data Center can be used by public or private actors. A secondary beneficiary is the
football club, which can use the football field in a longer period of the year. It is a bit difficult
to define the geographical scope of the project – it depends where the individual server halls
would otherwise be. However, with this solution, it would be considered a local project since
it is depending on the availability of the district cooling grid.
Innovative features to attract media
About 100 delegations of visitors come to the City of Växjö every year to learn from the
things that have been carried out here regarding our striving towards a fossil fuel free
community. This project will be yet another success story to talk about or showcase to the
visitors. Since it is a physical place it is also possible to go there, see the PV plants and talk
about how the surplus energy is being used in various steps.
We also believe that this can be yet another of all the actions taken place in Växjö, that can be
of high interest from national and international media. It will also to a higher extent be part of
our own communication material, as we continuously update it.
Media is believed to find this project interesting, and will in that case, contribute to spread the
experiences over the world.
Social and political acceptance and sustainability of the solutions developed
The project has been realized thanks to the cooperation of many local actors, from the public
and private sector. We cannot really claim that the citizens have been involved in the project,
but they benefit from it in a number of ways. The citizens involved in the football club, and
the people who enjoy football, have the possibility to use the football field in a longer period
of the year. Another important benefit for the citizens is financial. Since Wexnet is owned by
Växjö Energy, which is a municipally owned company, it means that this is in the end public
money that has financed the construction of the server hall. And since the creation of a
common server hall for a number of different actors has turned out to be very cost efficient, it
also means that the money that has been saved thanks to this instead can be used for other
purposes.
The organizations using the server halls pay for their use of it, which also means that the
Green Data Center is self-financing, and will not disappear or shut down after a few years.
Instead, it is another important part of our way towards a more sustainable energy system – in
this matter; it is mostly the ecological and economic dimensions of sustainability that are
addressed.
Transferability/replication potential
We believe that this is a project, which in many of its parts can be transferred to other parts of
Europe. All over Europe, electric cooling machines are used for the cooling of different kinds
of buildings. There is most likely a huge potential to take better use of the surplus energy
from the cooling. And even if the temperature of the air or water is somewhat higher after
cooling the first building, it should still be cold enough to provide cooling in another building.
With the Green Data Center project in Växjö, we have solved this with our existing district
cooling grid, which reduce the use of electricity to a minimum. We are very well aware of the
fact that district cooling grids based on district heating is not possible to implement all over
Europe. But the idea of taking use of the surplus energy in a more creative, smart and efficient
way is definitely transferrable. No matter how you will solve this, it will generate a more
efficient electricity use, and since electricity in Europe is produced from non-renewable
sources to a very high extent, this is also good for the climate impact.
Also, since server halls need cooling all around the year, the idea of using the warm flows
from the server halls to heat a football field is also transferrable, so is the way of working,
where private and public actors realize this kind of activity together.
Additional information
http://www.veab.se/Pages/Page.aspx?pageId=917
http://www.mynewsdesk.com/se/pressroom/vaxjoenergi-veab/pressrelease/view/wexnetbidrar-till-att-goera-vaexjoe-aennu-groenare-naer-groent-datacenter-invigs-i-vaexjoe-802384