Research in a New, Solar-Optimized Building: Fraunhofer
Institute for Solar Energy Systems (Fraunhofer Institut für
Solare Energiesysteme (ISE)) in New Quarters
For some weeks now, the approximately 300 employees of the Freiburg,
Germany Institute for Solar Energy Systems (Freiburger Instituts für
Solare Energiesysteme (ISE)) have been working under one roof. In light
of the field of activity of the institute, it is then understandable that
solar collectors are on the roof and photovoltaic modules are mounted
on the façade.
In all, the 20 kW nominal output PV modules and the 20 square meters
of collectors serve to actively use solar energy. That the building
complex counts as one of the outstanding solar office and industry
buildings can first be seen when one looks closer at transformed
energy concept.
Photo: The new Fraunhofer Institute for Solar Energy Systems
Work Place Quality, Functionality and Energy Efficiency
- the Central Components of the Building's Concept
Whereas before they were divided among eight different properties,
offices and laboratories are located under the single roof of the
13,000 square meter building designed by the Copenhagen architectural
firm Dissing + Weitling. Immediately, the ISE begins saving over
half a million dollars in rent for one year. Architecture and (solar)
technology entered a forward-looking partnership - according to
the motto of the planning team: "Exemplary Building with the
Sun". The guidelines were clear: efficient energy use, high
quality within the work place and a corresponding design. So the
ISE Building is by no means one of the spectacular solar buildings,
like, for example, the admirable "Heliotrop" building
in Freiburg by architect Rolf Disch. On the viewer, the new ISE
impresses a sense of objectivity and functionality.
Because of the north/south orientation of the land next to Heidenhofstrasse
northwest of down town, the planners decided for a longitudinal
building" with an associated opening axis (Traffic Line) as
well as three east/west oriented wings. An atrium with a shed roof
and photovoltaic modules receives visitors who enter through the
south-facing head of the building. Here the aesthetic aspects of
the building come into their own: It comes across as open, communicative,
and functionally elegant. The administration and central services
are housed in this part of the new building.
On the west side parallel to the building´s opening axis
the plant room, cleaning room and workshops are attached to each
other. The three story wings house in part the climate-controlled
laboratories on the north side and on the south side are offices,
which don't require an active climate control. The wings' flat roofs
take over the function of surfaces for open air experiments.
Graphic: The wings are oriented east/west, respectively, their
separation purposefully large with use of daylight taken into consideration.
Both the wings' structure and zoning combine passive solar energy
use in winter with low heat gain in summer.
Source: Fraunhofer ISE
Climate Control and Ventilation
Through integral planning, the numerous possibilities of passive
climate control for the offices should be completely exhausted.
By means of a dynamic building simulation the planning team determined
the necessary measures: Glass surfaces and specific types of glass
in the façade were matched; an effective, outside sun glare
shield on the outside is automatically controlled; the ventilation
is optimized.
In summer an air exhaust system working with the steel accent-ceilings
(they cool off faster than ceilings that are hung up) take care
of the building's cooling. The air is replaced up to five times
per night. Additionally, the skylights are opened by hand in order
to minimize any pressure loss, which could result considering the
high rate of airflow. Even long periods of hot weather don't represent
a problem; the concept assumes few days with room temperatures above
26 ºC.
An air/ground register for the cooling and preheating of intake
air is an additional component of the main building's ventilation
system: Seven 100-meter long pipes with widths of 25 centimeters
lie six meters deep in the work room of the excavated second level
basement of the building´s opening axis.To provide enough
fresh air for the offices in cold times of year there is an air
exhaust system: The ground air exchange averages 30 cubic meters
per person per hour.
The outside air flows through slit vents in the window frames into
the offices and through ventilation plate fins over the doors into
the floor. From there the exhaust air is centrally removed, its
heat recovered, which is then led to the laboratories.
Graphic: The ventilation concept of the main building.
Source: Fraunhofer ISE
Light and Lighting
Both doing without an air conditioning system for the offices and
the lighting control system, which provides agreeable daylight for
the workstations, save electricity. The roof- and façade-integrated
solar power system is able to precisely calculate the electricity
needed for the entire electric lighting system, and with its roughly
200 square meters it can provide for this need.
The wing structure of the building was chosen in order that the
employees of ISE not only receive light powered by solar energy,
but also receive enough sunlight-such a design increases incoming
sunlight. The orientation of the office space minimizes disadvantageous
east and west facades. For example, architectures confront the blinding
low sun throughout the year from these directions. The façade
layout and design as well as the lighting were first chosen after
a light simulation. Architectures and engineers design a façade
with four functioning segments: balustrade, windows, blinds, and
skylights.
Set flush with the roof, the skylight allows as much light to enter
as possible; a continuous outside sunblind with two-part service
guarantees protection against the sun yet still allows enough daylight
in.
Graphic: The interaction of daylight and artificial light.
Source: Fraunhofer ISE
When it is completely shut the blinds close in front of the windows
while they stay in a level position in front of the skylight. Energy
efficiency also means reasonable saving: The ISE engineers decided
for an electronic lighting system without "standby" use.
The floor lighting of 75 lux (unit of illumination) takes over an
indirectly incandescent lighting system in each office whose electric
circuit is automatically switched off when enough natural light
is present. The individual workstations have desk lamps with 500
lux. Together, only ten watts per square meter of light output have
been installed in office areas, and in the halls just 6 W/m².
The yearly demand for artificial light is about 10 kilowatt-hours
per square meter.
Solar Energy Supply and Effective Energy Conversion
Despite all of the energy-saving measures and the heat recovery
from the exhaust air, the building's PV system and the solar thermal
system can only cover a fraction of the entire ISE demand: a gas-powered
block-type thermal power station (BTTP) combined with an absorption
refrigeration machine covers the high year-round energy demands
of clean-rooms, laboratories and production sites (i.e. electric
diffusion ovens with 300 kilowatt connected loads).
The waste heat, which can be used for heating in winter, can be
converted to cold air in the summer. This power/heat/cold combination
is only economical if the highly significant, failsafe electricity
supply is included in the calculation. This is guaranteed by the
BTTP, which also reduces the investment costs with which such a
system is normally associated.
Photo: View of one of the two modules of the block-type thermal
power station, model MDE.
Source: Fraunhofer ISE
After eight years the station should pay for itself, then it should
cost about 15 % less when compared to a conventional energy supply
that requires almost double the initial investment. Future considerations
are possible: If required or wanted, the BTTP can be replaced with
a fuel cell aggregate using natural gas.
The Characteristics (Data) Of Energy Supply
Table: Fraunhofer ISE
Electric current
kW
Heat
kW
Cold
kW
Area
m2
BTTP
Boiler
AKM
KKM
PV
Collector
230
-
-
20
370
690
-
-
350
780
-
-
20
The solar components of the energy supply are noticeable - even
if they are hardly noticeable to the eye due to their clever integration
into the building's façade. The solar power system delivers
a total of 20 kilowatts, of which 10 kilowatts peak output (kWp)
are modules hung onto the wing facades, another 7 kWp is delivered
by solar cells in the insulation glass at the southern part of the
shed roof construction of the atrium and 3 kWp are integrated into
the south end Façade of the the building´s opening
axis. With a g-value of 24 % (energy transmittance based on solar
radiation), the modules take on both functions of heat and sun protection.
Collectors with an entire surface area of 20 square meters contribute
three-fourths of the warm water demand of the lunchroom.
Through measures taken to save energy and because of efficient
energy supply, the heating needs of the institute should be around
40 % below the level set by the Heat Conservation Provision (Wärmeschutzverordnung),
and they should not rise due to future equipment or functionality
upgrades. If the BTTP were also operated nights, then the primary
energy needs would sink further. If this makes sense, however, should
be checked - up until now the costs of producing energy onsite during
nighttime hours exceed the supply price for electricity supplied
by conventional, mostly fossil sources.
Three kilowatts of photovoltaic output are integrated into the
south side façade of the new building's opening axis. The
modules provide both heat insulation and sun protection functions.
Source: Fraunhofer ISE
After all employees have successfully moved in and after the inauguration
takes place on November 23, the team that has worked on the building
will continue to do so: Continuous monitoring and evaluation of
the building is to take place in accordance with the research project
"Solar Building: Monitor (SolarBAU: Monitor)", sponsored
by the Federal Ministry for the Economy and Technology (Bundesministerium
für Wirtschaft und Technologie (BMWi)).
The ISE will give architectures, engineers, building planners,
building owners and building specialists, as well as other interested
parties, the opportunity of expert tours through the new building
(Architecture: Dissing + Weitling, Copenhagen). Points of emphasis:
daytime light use, passive cooling for a high quality work place
in a low energy-use environment as well as the integration of solar
energy systems for energy supply.
Tours through the building take place during the following dates
(15 - 16.30, Price: 15 DM (about $ 7) / person): Friday, October
12, 2001;
Friday, December 14, 2001;
Friday, February 8, 2002;
Friday, April 19, 2002. Source: Fraunhofer ISE
You can also find information on the Internet at www.solarbau.de
Also read the Solar-Report over the ISE Creativity and Continuity
- Solar Research in Theory and in Practice
Material and Pictures: Fraunhofer Institute for Solar Energy Systems
(Fraunhofer Institut für Solare Energiesysteme ISE), 79100
Freiburg, Germany.
Solarserver Chief Editor: Rolf Hug.
