Sun, Light and Heat: Light Control and Optimizing
Energy
in Offices and Other Buildings
Daylight is solar energy. This is a trivial statement but comes
lightly to the background when speaking of solar energy use. Photovoltaic
modules and solar collectors make the sun's energy usable, but technologies
that provide for optimal light efficiency in buildings and that
make "living and working with the sun" enjoyable also
use solar energy.
Measures taken to save electricity for lighting or conserving
energy for heating are activities - a fact that the president
of EUROSOLAR, Herman Scheer, does not tire of stressing. And in
fact it seems as though the concept of passive solar energy use
or of a "passive building" veils everything that is
done here: effective daylight use and control as well as energy
optimizing are the characteristics of three buildings that we
present in cooperation with the BINE Information Service (BINE
Informationsdienst).
Sun installation in the German Museum of
Technology in Berlin. A fascinating play oflight
and shadow - but also an intelligent solution for transporting light:
Collector mirrors and reflectors project sunlight into a tunnel that
one passes through when entering the exhibit hall. Photo: BINE Information
Service
The Institute for Solar Technologies (Institut für Solartechnologien)
in Frankfurt/Oder, Germany, an office building in Weilheim/Teck
and the German Museum of Technology in Berlin are examples of an
energy concept in which sunlight and heat play central roles. Daylight
technology (systems that control and transport sunlight) and the
protection of exhibit pieces against radiation as well as favorable
room climate are central for the museum building. That spaces with
cozy qualities and considerable energy conservation potential are
also possible in buildings that aren't used for dwelling is shown
by projects sponsored by the Federal Ministry for Economy and Technology
(Bundesministerium für Wirtschaft und Technologie (BMWi)) for
the research of "solar building".
High Work Place Quality - Low Costs for Lighting
and Heat
Many factors influence how well someone feels at work-therefore
also influencing job performance output. Among these are a comfortable
temperature, good air quality, and the most natural and glare-free
light possible. For the Solar Center in Frankfurt/Oder, an energy-optimized
building both was realized that offers: year-round comfortable work
conditions and low energy demand. The modularly constructed façade
system replaces the outside wall and at the same time guarantees
the best possible supply of daylight and fresh air. In effect, this
synergy façade combines the function of the building's walls
with the tasks of household technology.
The windows are equipped with outside blinds over which a rigid
daylight control system is installed-artificial light is only activated
by a light detector when needed.
Modular façade system on the south side of the Solar Center
in Frankfurt/Oder. Photo: BINE Information Service
Integrated in the balustrade area of the façade are thermal
air collectors and a photovoltaic system. Behind that is a heating,
air-conditioning and ventilating machine with a heat exchanger.
This pence of equipment is connected to the active flow of air
via a connection canal between the window's two panes of glass (gap
between the conventional pane and the heat-insulating pane). In
winter the incoming air is heated over the air collector and then
led to the heat exchanger. There, another rise in temperature follows
due to the heat energy absorbed from the used air. Afterwards the
pre-heated outside air comes to a convection heater in the room.
Schematic diagram of the façade with air ventilation
(winter operation). Graphic: BINE Information Service.
This is then simultaneously supplied with fresh air and heated.
On sunny days the output from collectors and the heat gain for the
room's heating system are both adequate, and the used air is then
led outside through the space between the windowpanes. Over the
course of a year the photovoltaic system delivers the needed energy
for the operation of the ventilation system. The collectors are
turned off in the summer via a summer-winter circuit because the
warm outside air comes in direct contact with the heat exchanger
and there the cooler inside air can cool it. On very hot days cold
water from an underground reservoir flows through the heaters, turning
the heating system into a cooling system. Soil serves as the cold
source.
The concept fulfills the planners' expectations: The thermal heating
and ventilation heating demands for the technology area are around
58 kilowatt hours per square meter and year and meet the requirements
of the Energy Conservation Act (Energieeinsparverordnung (EnEV)).
The energy demand for lighting and office technology was more than
halved compared to a conventional building. And those working in
the rooms are content: The lighting conditions are experienced as
pleasant and adequate, and even during the summer rooms don't become
overheated.
Energy Efficiency without Extra Costs: Office Building
as a Passive Building with Solar Heat and Solar Electricity
The first passive office building in the German state of Baden-Wuerttemberg
has been standing in Weilheim/Teck since the beginning of 2000.
Its ecological design concept, the corresponding architecture and
the economical aspects are convincing: Despite the difficult requirements
for building ecology and the considerable energy conservation, one
square meter of office area costs less than 1,000 € (ca. $
900) - no more than a conventionally constructed building.
The building uses the sun's energy both actively and passively.
By avoiding transmission and ventilation heat losses the energy
demand for heating was reduced to under 15 kilowatt hours per square
meter and year-making a conventional heating system as unnecessary
as active air conditioning.
Office building "Lamparter" as seen
from the west. Photo: BINE Information Service
Passive cooling during the summer is achieved by a variety of methods
including shadow elements, ground soil heat exchangers and night
ventilation. Elements in place for lighting control minimized the
need for artificial lighting, which is at just 7.2 kWh/m² per
year. Strict cost controls even made it possible to use funds from
the budget to provide for solar heating and solar power systems.
Warm Water and Electricity from the Sun
In the entire building there are no heaters - the job of distributing
heat is taken over by the ventilation system. With the help of temperature
gauges warm air can be separately led to the top floor, or the north
or south side. Used air is vented out from the common areas (conference
rooms, stairways) of every floor, led to a heat exchanger and finally
vented outside. In this way about 85 % of its heat can be absorbed
by incoming air. Additionally, on cold days the outside air's temperature
can be raised by an average of 4.6 Kelvin by using an earth-to-air
heat exchanger. A connected bivalent condensing boiler provides
the remaining needed heat. At 10.6 kWh/m², the actual heating
energy demand is even lower than the planned value.
Passive office building "Lamparter": Energy
supply system. Graphic: BINE Information Service
Contributing to the electric current supply is a 67 square meter
photovoltaic system that is mounted on the flat roof and pent roof
of the building. The estimated 6 to 7 megawatt hours (MWh) produced
yearly correspond to 6.5 kWh/m² of electricity based on the
net heated floor area. By heating potable water, a solar thermal
system supports the gas heating system with 1.5 kWh/m² per
year, and because the demand for this water is very low at just
2.6 liters per person per day, water heating can be up to 93 % covered
by solar means. Outside the main heating period the water heating
system runs for just one hour per day. Therefore it is accepted
that the water temperature fluctuates. Overall, solar energy provides
20.9 kWh/m² of the needed primary energy with solar-produced
electricity covering about half of the energy used for lighting
and the ventilation system.
Comparison of primary energy requirements for building
technology in kilowatt-hours per square meter per year (kWh/m²).
Graphic: BINE Information Service
Controlling and Transporting Light - The German
Museum of Technology in Berlin
With a usable floor area of 20,000 square meters, the expansion
building of the German Museum of Technology is subdivided into departments
for air and sea travel as well as accommodations for a library,
workshops, a lounge and catering areas. In order to protect exhibit
pieces from direct solar radiation, they were placed on the north
side. The additional accommodations open towards the south and are
characterized by a transparent façade design.
With an energy concept, which meanwhile the museum is presenting
in multimedia to bring visitors closer to the rising energy-efficient
technology, it was also possible to reach a low energy standard
here.
The Berlin Institute for Construction, Environment and Solar Research
Ltd. (Berliner Institut für Bau, Umwelt und Solarforschung
GmbH (IBUS)) and the Fraunhofer Institute for Building Physics (Fraunhofer
Institut für Bauphysik) in Stuttgart conducted the project's
implementation over many years.
Expansion building of the German Museum of Technology
in Berlin, right of the exhibit hall with a hanging C-47 "Skytrain"
and sometimes affectionately referred to as the "Gooney Bird".
Photo: BINE Information Service
Despite demanding requirements it was still possible to get by
without air-conditioning and the high energy needs associated with
it. Planners stabilized the inside humidity (important for a museum)
through the use of hygroscopic materials (the expanded clay in walls
and wood-block paving on floors attract and absorb moisture and
therefore dry the air in the museum).
Light and Shadow
The overhead light layout and the implementation of the daylight
systems were optimized in detailed studies under an artificial sky.
On the east façade, for example, it was effective to develop
a daylight system that obtains the attractive city view, yet at
the same time is able to fulfill its function of a visor against
the sun and additionally has light-controlling qualities. Here the
planners installed large lamellas at every story of the building.
An inner transparent lamella wing was installed with an outer wing
made of perforated metal. Depending on the angle of the lamella
the degree of daylight screening can be varied without reducing
the illumination.
The floor areas of the museum that are further in and cannot be
supplied with daylight by the facades led to the idea of installing
a daylight transportation system along the paths that visitors take
in the exhibit areas. Using three systems, planners bring sunlight
into the building.
Sun-tracking Fresnel lenses collect daylight that is then led all
the way to the foyer in the second floor via fluid light tubes.
There, four daylight tubes are supplied with sunlight by this transport
system.
Left: Light collectors (tracking Fresnel
lenses). Right: Light tubes as a transportation system in further-in
parts of the museum. Photos: BINE Information Service
A so-called sun installation throws sunlight into a well, which
one walks through when entering the exhibit area. This occurs with
the use of a mirror system that is composed of a single-axis sun
tracking collector mirror (heliostat) and a stationary reflector.
Left: Heliostat. Right: The systems fulfill the lighting
needs of the further-in interior parts of the building. Photos: BINE
Information Service
A concave mirror (heliostat) with a surface area of about 14 square
meters together with lighting reflectors supplies the interior of
the museum with sunlight. With this modifiable system the various
lighting tasks in the exhibit area can be met.
Material and pictures BINE: www.bine.info
(project information 7-9/01….in German) / Solarserver editor:
Rolf Hug
