pcm tower botanical garden berlin study tour notes
DESCRIPTION
Notes from recent Gale & Snowden study trip to Berlin as part of our TSB work on the Passivoffice development at Devongate.TRANSCRIPT
Design for Future Climates Research
Technology Strategy Board (TSB)
Innovative PCM applications to limit overheating in buildings
Study Tour, Germany
April 2012
Notes
Gale & Snowden Architects & Engineers
April 2012
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 2 of 7
PCM Applications, Study Tour
Germany, April 2012
Notes
Prepared by: Tomas Gaertner
Checked by: David Gale
Project: PassivOffice
Version: 1
Date: April 2012
Job No: B1113
Reference: B1113 CCA Passive Office\Reports\PCM Applications Germany Study Tour Notes
Rev No Comments Date
Gale & Snowden Architects Ltd
18 Market Place
Bideford
Devon EX39 2DR
T: 01237 474952
F: 01237 425449
www.ecodesign.co.uk
Company No. 5632356
VAT Registration No. 655 9343 06
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 3 of 7
1.0 Introduction
The following details the findings and observations from the Gale & Snowden PCM Applications Study
Tour to visit the ‘Great Pavilion’ in Berlin’s Botanical Gardens.
2.0 Details of the Victoria House/Great Pavillion
2.1 Introduction
Building name: Victoria House, ‘Great Pavilion’ in Berlin’s Botanical Gardens
Completed: 1906, refurbished in 2009
Floor area: 1750m², 60 m long, 29 m wide and 26.5 m high
Building type: tropical green house
No of Floors: 2 including a basement
Figure 1: The Great Pavilion, Botanical Garden Berlin
The Victoria House (also known as ‘the Great Pavilion’) at the Botanical Garden in Germany's capital
Berlin is one of the largest greenhouses in the world. It was built in 1907, covers an area of about
1,750 m2 and has a capacity of 40,000m3. The average temperature inside is maintained at 30 °C and
air humidity is kept high. Over a period of three years the building underwent a complete restoration
(completed in 2009) in order to maintain the historical basic structure and to reduce energy
requirements by 50%. Refurbishment work included a new façade and glazing system, new heating
and ventilation and installation of ‘PCM towers’.
2.2 Key features
The refurbishment of the building included an innovative application of phase change materials to
control internal temperatures and to reduce energy demand for heating and cooling.
Two approximately 12m high towers have been placed at either end of the green house. To blend in
with the tropical plants they have been designed as hollow giant trees.
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 4 of 7
Their purpose is to guarantee an optimal vertical temperature distribution in the greenhouse. The core
of these towers is filled with aluminium panels containing a special PCM (in this case salt hydrates)
operating at 25°C.
A ‛phase-change material‛(PCM) is a substance with a high ‛heat of fusion‛ which, melting and
solidifying at a certain temperature, is capable of storing and releasing large amounts of energy.
PCMs, such as water, paraffin, salt hydrates, etc. are able to absorb, store and release large amounts
of heat or cold at comparatively small temperature change by changing their physical state, as for
example from solid to liquid, solid to solid or through evaporation of the storage material. The heat
stored is called latent heat, therefore materials are also referred to as ‚LATENT HEAT STORAGE
MATERIAL‛.
The towers at the Great Pavilion store ‚heat‛ or ‚coolth‛ depending on the ambient air temperature.
During the day the air at the roof of the greenhouse heats up due to solar gains. An extractor fan at
the top of the tower pulls in the air and pushes it down the tower, past the PCM panels and down to
the plants. On its way down heat is absorbed from the air and stored in the PCM, provided cool air to
the plants. During the night the air at the top of the green house cools down. This air is again pulled
in via the extractor fan, heated by the energy stored in the PCM material on the way down and
supplied as warm air at plant level.
According to the engineer involved with the development of the PCM panels, key to optimise the
performance of the PCM is ventilation. The PCM needs to be exposed to adequate, constant air flow
across its surface to effectively store and release energy. Where these materials are built into walls or
ceilings (e.g. as an additive to plasters and plasterboard) the surrounding material (e.g. gypsum) and
furniture/wall coverings provide a too high thermal insulation which reduces the effectiveness of the
PCM.
An ideal technical solution would be a combination with a fan driven ventilation system that controls
the air flow across the PCM surface. Using containers with large surface to volume ratio, made of
highly conductive material (e.g. aluminium) for the PCM further increases its potential to store and
release heat.
Figure 2: Rubitherm PCM panel used at the Great Pavilion, Berlin (Photo: Rubitherm)
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 5 of 7
2.3 Technical Details (per tower)
Manufacturer: Rubitherm GmbH Ventilation Volume: 7,500 m³/h Pressure drop: 50 Pa Fan Power: 1.1 kW Heat Storage capacity: 110 kWh / cycle (8 h/d) PCM – mass: ca. 3000 kg
2.4 Monitoring Results
Figure 3: Temperature monitoring ‘Victoria House’ (Source: Rubitherm GmbH) and schematic of
cooling tower (the black line represents ambient air temperature at high level, red line
represents air temperature at the top end of the towers, pink line indicates air
temperature at the supply side at the bottom of the towers)
According to a monitoring study carried out by the manufacturer of the PCM panels the system
effectively moderates ground level temperatures. As can be seen from figure 1, with the ventilation
system to the towers switched off, the ambient air temperature at ground level follows the high level
temperature but with a ~3 degree temperature difference. This difference is explained with the cooling
effect from the ground, transpiration cooling from plants and the effect of heat rising.
When the towers are ‘switched on’ internal temperatures at ground level are maintained at even
temperature range of ~27 degree C throughout the day. The system appears to provide effective
cooling via heat storage during the day and supplements the heating over night. The manufacturer
confirmed that additional heating during night needs to be provided all year round.
Rubitherm estimates that with this system operating on approximately 200 days per year (= 200 cycles) ca. 22,000 KWh of energy can be saved (equivalent to 5 tonnes of CO2).
2.5 Design for Future Climate (D4FC) Adaptations
The ‘PCM towers’ at the Great Pavilion represent an innovative solution to moderate high daily
temperature swings within buildings.
This method could be applied to office buildings where high ‘non-useful’ internal heat gains during
working hours could be stored providing a cooling effect.
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 6 of 7
Instead of simply removing the heat, the stored energy could be used during the heating season to
maintain background heating when the building is not in use and thus contribute to reducing the
energy demand of a system.
If combined with a MVHR system that already forms part of most low energy office buildings, the
effectiveness of the PCM could be optimised whilst at the same time providing a more cost effective
solutions.
Further investigations are required to establish how this methodology could be implemented into the
design and services strategy of a modern office building and also how a retrofit solution might work.
2.6 Images
Figure 4: one of the PCM towers at the Graet Pavilion, Botanical Gardens Berlin
Gale & Snowden Architects Notes from PCM Applications, Study Tour, Germany
April 2012 Page 7 of 7
Figure 5: Supply opening at the bottom of the tower