Category Archives: BACKGROUND

Combination of microstructures and optically functional coatings for solar control glazing

Gunther Walze, Peter Nitz, Jurgen Ell, Andreas Georg, Andreas Gombert, Wolfgang Hossfeld, Fraunhofer-Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg, Germany

New developments in large scale micro structuring of surfaces offer a wide range of applications in glazings with solar control and light redirecting properties. In many cases, e. g. when using prism arrays or Compound Parabolic Concentrator (CPC) arrays, the geometry of these structures allows to coat single facets of the structure selectively with optical coatings. This selective coating technique offers a way to further improve the optical performance. First prototypes of prismatic arrays with face-selective surface coatings have been realized and their hemispherical and direct transmission has been measured. Furthermore, a gaschromic switchable coating and a switchable mirror have been applied face-selectively. We will give an overview of the realized systems and discuss the results of the measurements. We will also give an outlook of some further concepts for the use of optically functional coatings or layers combined with light redirecting surface structures.

PRELIMINARY STUDY OF SMALL SCALE SOLAR TEST. CELLS FOR SOLAR THERMAL EVALUATION OF. BUILDING COMPONENTS

G. Alvarez+, M. J. Jimenez and M. R. Heras*

*CIEMAT.. Renewable Energy Department. Av. Complutense No. 22. Madrid, Spain.
28040. Tel/Fax: 91 346 6344. Email: mrosario. heras@ciemat. es,
mjose. Jimenez@.ciemat. es

+CENIDET, Mechanical Engineering Department. Prolong. Av. Palmira s/n. Col. Palmira.
Cuernavaca, 62490, Morelos, Mexico. Tel/Fax: +52 777 312-7613.
gaby@cenidet. edu. mx.

ABSTRACT

This paper presents a preliminary study to validate small scale solar test cells for thermal evaluation of building components such as windows and roofs. The description and performance of the scale test cells are described. The validation of the thermal performance was made with the real test cell Passys indirectly by applying the classical averaging method that was initially used for the Passys cells to determine overall heat loss coefficient, UA, and the solar heat gain, gA. The use of this methodology was selected, as a first approach, to evaluate the viability of the study of scale test cells. Our preliminary results indicate that some percentage differences were high for some tests. Therefore, it is necessary to increase the period of time of the measurements of the scale test cells, in order to use dynamic system methods to reduce the percentage differences of UA and gA.

INTRODUCTION

In the decade of 1970 and 1980, the applications of solar energy to buildings were encouraged in order to be more conscious of the conservation of energy. New materials for roofs, walls and windows appeared and the need to have detailed information about the solar thermal performance of the components in buildings was required. Thus, the thermal evaluation to characterised components of buildings using test cells was increasingly used. However, the solar thermal evaluation of components of buildings using small scale solar test cells have had very little attention and might be very valuable tool for an engineer, architect or contractors. The advantages of small scale test cells are their low cost (compared with full scale cells), data can be taken under carefully controlled conditions and they can be moved easily and be located in different places in order to investigate the influence of building materials of a selected region. Around this topic, there has been very few previous studies with small scaled solar test cells. Grimmer et al. in 1979 considered small test cells with some basic elements of passive design for the thermal modelling of passive solar heated building designs. He emphasized the theoretical considerations that have to be made about the modelling of those systems. Werner in 1986 used scaled modules that helped to determine the glazing design for conservation of energy. Mora et al. in 2003 reported a test cell used to characterise the heat transfer and
zonal mass by natural convection. About thermal evaluation of components of buildings, there have been some thermal studies in full scale cells. These cells have been developed in Europe since 1985, Vandaele et al. presented an overview on them in 1993, Hahne and Pfluger reported significant hardware improvements in 1996, and presently these testing capabilities are quite consolidated and the most recent research projects have been focused in improving testing procedures and application of techniques for dynamic data analysis. There have not been reported methodologies of small scale cells to test the components of buildings in warm climates connected with the consumption energy of an air conditioning system.

This paper presents a preliminary study of a small scale solar test cells and a comparison with the thermal performance of full scaled Passys test cells, using the classical average method that was used to characterised the Passys cells at the beginning (ISO 9869, 1994). The use of this methodology was selected, as a first approach, to evaluate the viability of the study of small scale test cells to test components of buildings such as roof and windows. The methodology gives information about the overall heat loss coefficient and the solar heat gain of the small test cell.

SUPERINSULATION MODERNISATION URGENCY

A rapid growth of interest in superinsulation has been noted in 1970-80s and has been connected with the development of cryogenic engineering, space engineering, aviation, surface and underwater sea fleet. An interest in superinsulation was also resumed in the end of 1990s and in the beginning of the 21st century. The development of hydrogen power industry in the symbiosis with nuclear power industry is a part of prospective national programs of a number of developed states. The placement of a nuclear reactor in the world ocean water area for hydrogen production and liquefied hydrogen transportation to an island
is one of the prospective projects of the Japanese power industry development. In order to store reserves of liquid hydrogen, oxygen and other liquefied gases, effective cryogenic reservoirs and pipelines will probably be required.

The volatility of most effective reservoirs is 0.8-1% per day of the total amount of liquid being stored.

Giant dimensions of present-day reservoirs determine a large amount of expenses on manufacture of the internal and external reservoir shells. In order to optimise expenses, the external shell is manufactured from a low-alloyed steel. The latter circumstance leads to increased gas releases of inter-lattice hydrogen into the heat-insulating cavity. The hydrogen content in the casing metal of most spread modern cryogenic reservoirs is 9.5-11 cm3/100 grams of metal. Zeolites being most widely used in Russian cryogenic engineering in cryoadsorption pumps comparatively well absorb hydrogen in the range of 20.2K and considerably worse at higher temperature.

As a result of long-term reservoir utilisation without a possibility to conduct of obligatory process of technological TIP blowings of heat-insulating cavities (HIC) and KSN regeneration, the amount of residual hydrogen in HIC achieves significant values. The reason of the hydrogen concentration increase in HIC can be both the inter-lattice hydrogen of structural materials and hydrogen inflowing (or diffusing) through microleaks from the internal vessel at the storage of hydrogen therein as well as from the atmosphere. The consequence of it is a considerable increase of the cryogenic liquid volatility. The situation being considered is much more related to the emergency categories and manifests itself to the full extent quite rarely. However engineers dealing with the operation of such systems can rather often observe the phase of appearance of several occurrences of this situation at the normal functioning of the reservoir too, especially at the final stage of the routine maintenance interval.

The New Buildings

In order to provide for the new uses, the existing buildings had to be radically altered and extended. However, the local planning authority required that the views of the outside of the building must remain largely unchanged. Both the ‘coach house’ and ‘horseshoe’ buildings had to be converted for modern office use with, in addition, exhibition, catering, conference, meeting, and main plant spaces.

The conversion of the coach house was relatively straightforward: the building fabric was upgraded to meet contemporary office use and the courtyard was enclosed by inserting a new steel structure. The conversion of the horseshoe was more complex. The construction between the two towers, except for the timber roof structure, was entirely demolished, the ground floor was lowered, the upper level floor and the roof reinforced, and the outer external wall rebuilt. The ground floor was extended into the courtyard by 5m and a new single storey link, incorporating the main entrance, was placed between, and connecting, the two wings of the horseshoe. Turf was planted on the roof of the new office space.

A third entirely new building was introduced close to the northern perimeter of the site. So as not to intrude in the landscape, this building was partly sunk into the ground and the excavated earth banked up against the north wall. This building provides storage for the harvested biomass crop. Its roof comprises the hybrid photovoltaic/thermal array.

Pay back time

The only sorption system for heating and cooling that is well established in the (Western European) market is the Robur pumped ammonia/water system. However this system is far bigger than the average house system. From sorption systems for houses only costs of prototypes, of future projections and of early market introduction (Nefit) are available. We based a cost curve on the Robur system (catalogue price of 11.810 euro at 36.6 kW condenser/absorber power = 330 euro/kW) and on information from the early market introduction and prototypes. In this way we came to a cost curve in which the price per kW is decreasing with increasing condenser/absorber power (see figure 8).

Table 1 gives the values of other cost parameters that were used for the calculation of the simple pay back time (pay back time without interest, depreciation and inflation).

Table 1 Values of cost parameters

Costs natural gas small consumers

0.38

euro/m3

Costs electricity small consumers

0.15

euro/kWh

Investment solar system (including installation)

400

euro/m2

Dimension solar system

8

m2

=> Investment solar system (including installation)

3200

euro

Extra installation costs sorption system

300

euro

Investment compression airconditioning (reference)

700

euro

In figure 9 we can see that with this cost structure a sorption system without solar system can only be cost effective for the existing houses (average and big) and not for the more energy efficient newly build houses (minimum and reference). In newly build houses the space heat demand is not high enough to make this system feasible. For the market segment of average and big existing houses a condenser/absorber power higher than 3 to 4 kW is not attractive.

When we add a solar system (figure 10) the simple pay back time becomes longer than 15 years for all options. In these calculations no tax credits or subsidies were accounted for. When there is already a solar system with the right dimensions available in the house, the pay back time of adding the sorption system becomes comparable to figure 9.

Again the system is more attractive for the average and big house (existing houses) and less for the minimum and reference (newly build). There is now a clear optimum for the average house (at 2 to 3 kW) and for the big house (at 3 to 4 kW).

Technology

There are numerous sorption processes that could be used for a solar sorption heating and cooling system. The most common sorption process that is used for cooling (LiBr/water) is however not suitable as a heat pump, because it cannot operate below 4 oC. The other common sorption process is ammonia/water. Recently in Austria the Solarfrost development was launched. This ammonia-water-hydrogen absorption/diffusion heat pump is especially designed for driving temperatures below 100 oC. The system can thus be driven by a standard solar hot water system. Other developments in ammonia/water in the Netherlands
are the Nefit diffusion/absorption heat pump and the Remeha pumped ammonia/water heat pump. These companies do not consider the adaptation of their heat pump for solar cooling. Another group of sorption processes that can be used is the sorption of vapour in solid materials like water/silica gel (Sortech) or water/zeolite (Vaillant)

In existing buildings the weight and the height of the system are important success factors (especially in the Netherlands, were we do not have cellars). In this respect the pumped ammonia system and the Sortech solid sorption system are potentially better than the Solarfrost diffusion/absorption system, because of the large pipe diameters at high pressure that are needed for the self pumping ammonia system. Moreover the diffusion/absorption system does not have the possibility to adjust from heating operation in winter to cooling in summer, because the condenser/absorber temperature is fixed by the hydrogen pressure.

A solar sorption cooling/gas driven heat pump is technically a feasible system (see also the work of IEA task 25 [Henning, 2004]). Because of the large number of circulation pumps that are needed (at least a solar pump, a generator pump, an evaporator pump and a condenser/absorber pump) parasitic power consumption is a point of attention in further developing the solar sorption system.

Safety

In The Netherlands there are no regulations for the application of ammonia in houses (at less than 2.5 kg of ammonia). However the application of ammonia at 15 to 25 bar can be hazardous when leakages occur in closed spaces (like attics or cellars). The water/silica gel of the Sortech system or the water/zeolite of the Vaillant system is in no way hazardous. The system pressure will stay below the ambient pressure (at condenser/absorber temperatures below 100 oC). Silica gel or zeolite is not hazardous.

Developments

Ecofys is one of the partners in the European Modestore project. In this project a technical test of the Sortech solid sorption system is performed in Germany, Finland, Austria and The Netherlands. The first system has just been installed in The Netherlands this spring and monitoring will be performed during the summer of 2004 and the winter 2004/2005.

Acknowledgement

This project was supported by the NEO (New Energy Research) programme that is implemented by NOVEM (Netherlands Agency for Energy and Environment) commissioned by the Dutch ministry of economic affairs.

Conclusions

• A sorption system without solar system can be cost effective for average and big existing houses. In newly build houses the space heat demand is not big enough. Sorption with solar for heating and cooling is not (yet) cost effective for the Dutch cost structure (without subsidy of tax credit).

• Optimal condenser/absorber power for cooling and heating is around 3 to 4 kW for the market segment of average and big existing houses. This is equivalent to an evaporator power of around 1 to 1.5 kW.

References

1. BAK, Survey natural gas use in houses in the Netherlands, Energiened, Arnhem, 2001.

2. Hennig H.-M. (ed.) Solar-Assisted Air-Conditioning in Buildings, Springer Verlag, Vienna, 2004.

3. Herold K. E. Absorption Chillers and Heat Pumps, CRC press, New York, 1996.

Laboratory building ”ECN-31” in Petten

The sun shading PV modules have been added to this old laboratory building (1963) as part of the renovation process. The south facade had a problem with overheating in the summer. The problem was a reason for the way the PV modules have been used. Shaped as the external louvres system that forms a separate facade (about 80 cm from the building), the PV modules protect the interior against excessive solar heat gain in the summer. Their external location efficiently prevents the „greenhouse effect” that occurs when sun rays enter the inner space via glazing. In summer, sun rays fall onto opaque PV modules. In this way desirable shading of the building is provided. During
winter, when the inner space heating is needed, solar radiation contributes to passive solar heating. Owing to sun shading modules, arrangement and their angle of inclination, the sun rays are able to enter the building, warming up the southern zone of the inner space. Likewise in summer, PV modules’ usage affects thermal environment in winter and is in charge of thermal comfort of the user.

The same applies to the lighting environment. The PV modules’ usage contributes to providing diffused daylight both in the winter and in the summer when the direct solar radiation is most frequent. In the sunny days, the sunlight diffusion is obtained due to sun rays’ deflection against PV modules’ surface, which is the result of the optimal PV modules’ position. This prevents strong contrast, shadow patterns and glare effects from appearing in the inner space.

view from the inside

mobile PV modules

fig.4 the ’’shadowvoltaic system”

To facilitate visual contact with the outer surroundings, a movable row of the sun shading PV modules has been designed. This allows the user to set their position according to his will and sustain visual contact with the outside. The rest fixed rows (of which two are visible from the interior) partially interfere with the contact. However they very slightly affect the visual comfort of the user (fig.4).

Simplified representation of the radiant pattern in urban environment

G. Scudo, A. Rogora, V. Dessi
Politecnico di Milano, Dip. BEST
Via Durando 10, Milano

gianni. scudo@Dolimi. it

alessandro. roaora@Dolimi. it

valentina. dessi@Dolimi. it

Materials of built environment (in a broad sense: building materials for pavements and facades, shading devices, vegetation and water) have an important role in modifying microclimate and comfort conditions in urban space.

Materials surface temperature depends on energy balance which is given by solar and thermal radiation budget (short wave and wave radiation),plus convective (and conductive) flows.

In town context usually convective flows at pedestrian level are low, so the influence of materials is mainly due to radiant exchanges.

Fig 1 Surface temperature of typical “urban material” in summer afternoon in Milan

Also evaporation of water influence very much surface temperature both in vegetation and in pavement or ground ( in summer midday surface temperature of a tree crown can be a little lower than air temperature, let’s say 35 K in Milano, while grey concrete is around 50 and asphalt around 60°)

While the general effect on microclimate of building material in specific urban context and configurations have been largely inquired by microclimatologist (summer and winter heat island effect, albedo distribution, radiant fluxes in canyons… see Akabari et al., Oke, Santamouris…), the specific effect of single materials have been only recently inquired.

In example Asaeda inquired the role of heat capacity of different materials (asphalt, concrete, sand layer and soil) coming to the conclusion that low heat conductivity materials (asphalt) rise day temperature, while high heat conductivity ones ( concrete) raise night temperature: they are not therefore good performing materials for open space; at the contrary bare soil or highly water permeable materials have a much better microclimatic performance due to the low conductivity and the cooling effect of water evaporation.

This paper proposes to evaluate the variation of the radiant behaviour of an indiferenziated open space as it is perturbed from the energy point of view.

If we think of an unlimited and unique material paved open space, we’ll have omogeneus envirnmental conditions in all of its extension.

This condition can be considered as the reference case because the performance of the space depends only on the general conditions of the site (latitude, sky openess, season, radiation, etc.,) and the pavement materials.

A physical element in the open space, of any nature, alters the condition of it introducing local variation in which intensity and extension depend on the nature of the element.

From the geometric point of view the defined elements are: punctual, linear and spacial (deriving by the combination of linear elements).

We consider points those objects (plants, umbrellas, tents, fountains, etc.,) assimilable to mondimensional elements; their effect spreads to around changing the conditions of temperature and thermal balance in a decreasing and oriented way (anisotropic) for a defined spacial area.

The changing effect is different for each time period of the day.

A linear element is a vertical blade, with different layer and technology. The effect of the temperature and thermal balance variation can be described trought a variation curve analysed in the central point of the blade (infinite, i. e. without border effect), that change in the different time period of the day.

The presence of the blade defines three distinct environmental conditions: the ones perturbed before and after the blade, and the one in which the perturbation due to the shading element is not perceivable.

The variations depend on the change of the radiant field introduced by the different distribution of the solar radiation, on the capacity of accumulation and riemission of the radiant energy by the vertical and horizontal surfaces, on the wind and the irradiation conditions.

A continous facade of buildings is assimilable to a linear element.

A single linear element represents a road with a certain width whose one facade isn’t influenced by the presence of the other one in the opposite side.

Two facades of heightness of 24 m distant from each other 50 metres influence each other in a negligible way. The more close distances require some verifications and considerations.

This paper focus on the analysis of the radiant field variation due to the presence of the "blades” expressed in terms of D/H ratio.

For the spacial elements, it is intended "rooms”, realized by the different technologies (forest, pergola, canyon, corner, etc.,) in which the changing effect of the conditions of temperature and thermal balance is described, in the other way for the different time periods of the day, by the specific values of the environmental conditions (absolute values, about 33°C, or easier, parametrized values with respect to the air temperature, 4°C less of the air temperature).

This paper focuses the attention mainly on the linear elements. The influences depend on the different factors:


geografical

— climatical

— morphological

— technological

For simplicity we can consider only the summer season, for the latitude of 45° (Milan). The analysis have been done for the linear obstruction N-S and E-W oriented.

The first evaluation is related to the isolated blade, i. e. a road of infinite width (in which a facade doesn’t perturb the area close to the opposite facade).

If we analyse the MRT values in a creasing distance from the blade (for instance for each meter), we’ll find, for the five time periods of the day, specific values that can have plus or minus important differences from the MRT of a field not perturbed.

In this sample we show some points of two meters distant. The blade in the middle of the space means that there are sides facing to the south and the north.

Fig 4 The curve of the temperature trend in the E-W oriented street in summer in Milan

At noon the side facing to the south is completely reached by the solar radiation, and it means to have MRT values in between 33°C and 37°C.

As we approach to the vertical surface, the MRT increases; in fact the wall is reached by the solar radiation and riemittes in terms of thermal radiation (heat) in the infrared band.

In the side facing to the north there is an area always shaded. In this case, where there isn’t an important reirradiation, the MRT is about 19°C, without relevant variations.

Moving from the shadow to the sunlight the MRT increases, of about 13°C, reaching 32°C. Under the sun the MRT is almost costant except for a very light decrease as we go far from the wall.

This argument is true from the morning to the early afternoon, in which the area facing to the south is reached by the sun and the one facing to the north at least for a D/H in between 0,22 and 0,44 is shaded.

In this time interval, that includes three of the five in a day, the curve tends to arise until the 3 p. m.. For instance, the highest value in the area facing the south at 9 a. m. is 30°C, at noon is 37°C and at 3p. m. is 42°C.

In the side facing to the north the difference in the shaded areas between the 9 a. m. and the 3 p. m. is about 7°C; infact is 15,5°C at 9 o’clock, 19 at 12 and 22 at 3 p. m.. There is the same difference under the sun, from the 29°C at 9 a. m., at 36°C at 3 p. m..

In the side facing to the south the trend during the day is quite the same, except the two moments in which the sun appears and disappears, at 6 a. m and 6 p. m.. In these points the change is evidence by a gap of temperature.

The side facing to the north has some time periods reached by the solar radiation, between 9 a. m and 3 p. m., while for the rest of the time, it is shaded. The trend is linear. At 6 p. m. both areas are shaded: the MRT values decrease a lot (about 18°C in the area facing to the south and 10°C in the one facing to the north), considering the accumulated radiation. The temperature continues to decrease till 4 a. m. very rapidly. From this point and the rest the decrease is more gradually.

If we pass from a high value of albedo (0,8) to a low one (0,2), the MRT trends remain the same, as the value decreases of about 10-20%.

the

45

0

p7 p6 p5 p4 p3 p2 pi pi p2 p3 p4 p5 p6 p7

When the blade is N-S oriented, i. e. has the sides exposed to the east and the west trend of the temperature is more linear.

Fig 6 The curve of the temperature trend in the N-S oriented street in summer in Milan

In the morning the radiation reaches the area and the blade east oriented, as the area west oriented is shaded. Viceversa, in the afternoon the west oriented area is the one by the solar radiation reached, as the one east oriented is shaded. For this reason the two points close to the opposite blade have a temperature difference of 12 °C.

At noon the difference decreases, till 5°C and they are contemporary under the sun.

After this moment, the trend changes, i. e. the values on the east side become lower, as those on the west side become higher.

At 6 p. m. the values of the west side are about 10°C higher then those on the east side.

To consider a blade with the two sides is like to have a road of which is considered all the points of the road section from those nearest to the facade to those at the center.

The similarity between one blade in an infinite space and one road is possible only if we consider a quite wide road, in order to avoid the interference between the two facades. When the fronts tend to approach the trend of the curve are the same, but we have also to consider the combinated effect of the two facades. In general we can say that the nearer are the facades (increasing the D/H ratio), the higher are the MRT temperature values (at the same sun/shade condition).

Fig 7 shadow path overlapped to the sections of NS oriented streets

This effect is due mainly to a couple of factors: the first is a less sky openess, i. e. svf low values, correspondes to a reduced radiant exchange with the sky vault, the second is the higher exchange between the wall and the man — energy fluxes receptor.

We consider the road with dimensional ratio D/H equal to 0,52, 0,26 and 0,12 for to understand what type of the roads can be tought as a road with facing buildig of hightness of 18 meters (6 floors) and width of 50, 26 and 16 meters respectivey. It means that on the E-W oriented roads at noon the road isn’t reached by the solar radiation.

str ada100 st гada 50 str ada 26

At noon the difference of temperature from a D/H to that of higher is about 1,5°C.

Fig 8 Temperature curves for different D/H ratio

Obviously the less is the distance between the facades, the less is the quantity of radiation on the street section. This difference tends to increase in the late afternoon, when it is more evident the heat accumulation effect that spreads hardly.

Fig 9 time 6 p. m. MRT difference between different streets

(1) Nikolopoulou M., Steemers K., Thermal comfort and psychological adaptation as a guide for designing urban spaces, Architecture, City, Environment, Cambridge, Proc. PLEA 2000, James &James, London

(2) Katzshner L., Bioclimatic Characterization of Urban Microclimates for the Usage of Open Staces, Proc. Architectural and Urban Ambient Environment, Nantes (Fr), 2002

(3) Scudo G., Rogora A., Dessi V., “Thermal comfort perception and evaluation in urban space” EPIC 2002 AIVC, Lyon, (Fr), 2002.

(4) Asaeda T. and Ca Thanh V., Heat storage of pavements and Its effect on the lower Atmosphere, Atmospheric Env., Vol. 3°, No 3, 1996.

(5) SOLENE++ Guide d’Utilisation, Laboratoire CERMA, Ecole d’Architecture de Nantes

(6) http://www. meteotest. ch

(7) Santamouris M., Doulos L., Comparative study o almost 70 different materials for streets and Pavements. M. sc. Final Report University of Athens, Department of physics, Athens, 2001

(8) Dessi V., Evaluation of microclimate and thermal comfort in open space, PLEA 2001, The 18th Conference on Passive and Low Energy Architecture, Florianopolis (BR), 2001

(9) Dessi V. “People’s behaviour in an open space as design indicator — Comparison between thermal comfort simulation and users’ behaviour in an open space”, Passive and Low Energy Architecture (PLEA) International Conference, Toulouse, (Fr), July 2002.

Energy consumption in the tropics: an increasing demand

Over the last years the high demand in the use of air-conditioning systems in the residential sector have contributed to the increase in energy consumption levels. This is due basically to the low costs of electricity and household air-conditioning (A/C) systems allied to a social lifestyle change, demanding better comfort levels. Sales of air conditioning equipment have increased considerably over the past few years in all different regions of the world [1], especially small packaged A/C systems that can be easily installed by homeowners.

The elevated levels of thermal stress in these regions, combined with higher urban densities (which basically impairs the use of natural ventilation for some periods of the year) along with the use of houses not only for leisure purposes, but also as a work environment (requiring privacy, less noise and distance from pollution), are the most significant reasons to justify the use of A/C in the residential sector. But understanding A/C systems as the major consumers of energy, in addition to being a potential source of hazardous CFC emissions (through ozone depleting CFC refrigerants), makes their growth prohibitive, as their usage could offset the energy savings being achieved by more efficient use of lighting and/or heating. Pressures to install air-conditioning units will escalate further, in anticipation of the effects of global warming. It is therefore important to consider how they could be made more efficient, and more importantly: whether any viable alternatives exist.

Resources efficiency

Resource efficiency is a central principle of our world today. If we think about providing for today’s six billion people as well as the generations of tomorrow, resources of all types — physical, financial and human should not be squandered. We understand that energy is essential both to facilitate production and for its contribution to quality of life, the services it helps deliver — heating, cooling, light motive power, mobility, etc, and to enhance economic prosperity, personal comfort and leisure. Some of the most challenging environmental problems that mankind faces in the 21st century are directly linked with the production, transport, storage and use of energy.

Therefore, the importance of resources efficiency has grown dramatically in recent years, as preserving the environment is a key strategy to make the world’s ecosystem more economically and environmentally sustainable.

This research project (BR Ecoproject) is concerned with the appropriate use of resources through sustainable features, demonstrating throughout the design process how energy use can be minimized in this particular context.

Interfaces and procedures

In place of a CAD-Interface a universal solution was chosen, which is internally called "Lacgraph": digital pictures are taken of old as well as new construction plans, read in, and displayed on the screen where corrections can be added.

Figure 2: Example of a simple building model with air exchange and controlled heating

Following the definition of the properties of the walls, windows, and different zones of the building, a model of the building is automatically produced from the library blocks. The simulation for the determination of heating and ventilation demands can be started imme­diately. In addition to the automated model creation, it is possible to manually create models by copying library compo­nents into a project. These components can be wired and parameterised by masks on the user interface.

The connections between blocks corre­spond to the flow of both physical media, measurement and control data in a real system. Examples of the first including air, water and power while the meas­urement and control data refers to quan­tities such as temperature, pressure and humidity. All blocks are colour coded in “Lacasa’’ according to the functional group they belong to. In addition, model blocks can be used for the input of measurement data as well as for the ex­port of data generated during simulation.

System Technology

The technical planning of the system was done by a group of engineering companies, named Rittgen 1(Fachbereich Heizung, Sanitar, Luftung) and Becker 2(Fachbereich Elektrotechnik). Supervisor was the Staatsbauamt (LBB3) Trier.

Air Outlet

Rooms

Air Inlet

Ansaugturme

(mit Gitter)

——- !4U і =

Ansaugschacht

Heizkreis

Erdreich

Nacherhitzung/

-kuhlung

Figure 3: Scheme of the system of the Earth Heat Exchanger with Heat Recovery

!/ччгк,, …………. .. —…

05

The earth heat exchanger starts his function in the year 2000, but today the measurement system is already not completely installed.

The air flow from outside is 15 mT(h m2), or 20-30 mT(h-Person). The dimensioning foundation for this are the rules in [DIN 1946], which defines the higher flow of both calculation possibilities. The single flows are given in figure 3.

Ingenieurburo Josef Rittgen, Am Weidengraben 7, 54292 Trier Ingenieurburo Klaus Becker, Herzogenbuscher StraBe 1, 54292 Trier Landesamt Liegenschafts — und Baubetreuung

The air in and out volume flow can be regulated by frequency controlled ventilators with a pressure sensor signal. The air conditioning systems have momentarily to be started manually in the rooms.

An additional CO2-Monitoring System controls the air inlet stream between the two 80% and 100% ventilator power level. In order to keep the noise level under the limit of 40 dB in the lecture rooms, sound damper were installed. Finally the fresh air has to be cleaned with a fine dust filter of class F7.

The installed heat recovery system at the Umwelt-Campus, with the help of a 14kW electrical heat pump, guarantees a gap free and continuous working condition in winter. The pipes for the recovery heat exchange were mounted symmetrically parallel to the earth heat exchanger concrete air pipes.

The heat pump has fixed working hours and works continuously from 07:00 to 19:00 a clock during the lecture times and variable working times for special courses, seminars, workshops etc. at weekend. This kind of control is to be preferred because of the slow time dependence of the heat exchange processes. As a result of experiences, the earth around the air pipes needs approximately three days to get a stationary temperature load after a cooling down period. The intermittent heat exchange process and the distances in the pipe circuit are arguments against a temperature controlled working condition for the heat

The buildings of the Campus are provided with a complex sensor, measurement and actor system for the automation system, which supervises and controls with a central DDC[33] all parameters, equipments and functions. All pumps, valves, drivers, louvers and adjusting flap valves temperature and are time dependent controlled with a software, and most of the process data are to be stored and evaluated. For this, all over the building there are microprocessor controlled units (PCU’s[34]), wich are interconnected for communication via a LAN bus system.

Additional to the sensors for the building control, the earth for the heat storage and both concrete air pipes have 48 PT100[35] sensors (4-wires) and two pressure head sensors systems[36] for an indirect velocity measurement. 24 temperature sensors were for this purpose installed in the earth in distances of 6m, 17,5m, 30m and 54m.

With 16 more sensors, at the same distances, the inner surface temperature of the concrete pipes is measured sideways and on the top. The remaining 8 sensors are room temperature sensors, which are mounted approximately 20 cm away from the inner concrete surface of the pipes into the air inlet flow.

These data are used to guide the actual status of the air earth heat exchanger with D/A — converter[37] via a bus system to a central process controller. With this, it is possible to store all data for detailed analysis and to give information on public displays for students and visitors.