The study reported in this paper was conducted between October and December 2007 [3] . A number of approaches were used to investigate energy utilisation at different levels of detail. A Utility Cost Analysis and a Walk-Through Audit were the first techniques implemented to better understand day — to-day, seasonal and longer-term variations [4] . The lifestyle of the occupants was also noted to understand any particular trends in energy use.

The Walk-Through Auditing phase involved identifying all appliances, which used electricity and / or water for operation. The position, brand name, model number, power rating and all other details pertinent to the operation and characterisation of the equipment were taken and input to appropriate spreadsheets, which would enable a more thorough analysis. It was noted that there were no gas — operated appliances on site. Table 1 shows a listing of the main appliances on the premises.

The first two phases of the energy study were followed up by a more intense evaluation of appliance usage and consumption trends. Plug-in meters were used for the low power appliances, such as audio­visual equipment, refrigerators, computers, etc., while clamp-on logger meters were used on heavier

loads, namely, the electric cooker and oven, washing machine, tumble dryer and the electrical backup heater in the solar tank. Electricity consumption of appliances in stand-by mode was also monitored in order to understand energy utilisation in a more holistic way.

Direct and diffuse irradiances on a horizontal surface measured during 30 years period at the meteorological station in Warsaw (Bielany) and averaged in a special way [2] have been used as input data for simulation of solar energy availability at the Research Center Jablonna. These averaged input solar data are presented in Fig.2.

Building envelope constitutes opaque and transparent surfaces with different orientation and inclination. The location of these surfaces causes different availability of solar radiation and in consequence influences in different way on the magnitude of solar energy incident on surfaces under consideration. Solar hourly irradiations on tilted surfaces with different orientation that constitute the envelope of the EDI building of the Research Center Jablonna have been calculated using the anisotropic diffuse solar radiation model described in mathematical way by the HDKR model [4]. The results of calculations are presented for some selected cases of surfaces orientation and inclination [3], that have been under special consideration because of their probably application (location) in the EDI building envelope.

Gs

The analysis of availability of solar radiation on surfaces with different orientation and inclination gives indications for shaping the building envelope.

As part of the International Energy Agency’s (IEA) "Solar Heating and Cooling" implementing agreement, the working group "Advanced Housing Renovation with Solar and Conservation" Task 37 was set up with the goal of describing renovation standards that are possible today, looking into and discussing new developments and implementation strategies at an international level. The focus is on joint national and international renovation projects in residential buildings whose energy consumption for heat and cold supply (space heating, hot water, auxiliary systems, and ventilation) was to be reduced by a factor of four below the national standard [1, 2]. As most of the participating countries are located in moderate or cold climates the focus is on the energy for heat supply.

In new buildings the so called “passive house technology” with an energy demand for heating of 15 kWh/m2KFAa could be stated as state of the art even though a thorough quality assurance is needed to achieve this goal. An energy supply for these buildings based on locally produced renewable energy in order to achieve net zero energy buildings is shown in various demonstration projects [3]. The development of concepts and their application to the existing building stock is the core working program of the IEA Task 37.

A common understanding of energy terminology and areas related to these parameters is a prerequisite for a successful work on an international level. UE indicates energy used in the building, EE indicates end energy at site including distribution and storage losses e. g.; PE indicates primary energy using national conversion factors for heat and electricity. The following definitions were used for area related energy characteristics: The heated net floor area NFA for the measurement analysis and Ause as an artificial area derived from the heated gross volume Ause = 0.32*V in energy calculations related to the German building code EnEV. In table 2 both areas are given, in some cases there is a significant difference. KfW40 and KfW60 indicates an primary energy demand of 40 kWhPE/(m2Ausea) for heating and DHW or 60 kWhPE/(m2Ausea) respectively. It’s a standard set by the German Kreditanstalt fur Wiederaufbau KfW. The 3-Liter-house aims for 30 kWhPE/(m2Ausea) with the same reference areas. The passive house standard is defined as 120 kWhPE/(m2NFAa) for the total energy consumption including all electrical household appliances, the heating energy demand is limited to 15 kWhUE/(m2NFAa). The zero house approach uses the same calculation scheme as the passive house standard but includes a full renewable supply on an annual balance level.

An analysis of measurements taken for completed renovation concepts provides the basis for further developments of energy efficiency measures and energy supply concepts. This paper focuses on the analysis of energy consumption and supply systems in realized projects.

1. Projects

Within IEA Task 37 more than 25 buildings from Europe and Canada will be documented and analyzed. Due to the availability of detailed measured data the German subset of buildings was chosen for a more detailed analysis. Tab. 1 shows the German buildings documented in this study. Some of the projects presented here were promoted as part of the German Funding Program ENOB, some of them as part of dena’s pilot project "Niedrigenergiehaus im Bestand" ("Renovating for low energy consumption") [4, 5].

The buildings studied were renovated from 2003 — 2007. In the process, primary energy demand for heating and domestic hot water was reduced on the average by 80 — 90 %, which was around 50 % below the current requirements of the German building directive EnEV (Fig. 1). Furthermore, in some projects more ambitious goals, such as zero-energy concepts (Blaue Heimat, Roter Block), the passive house standard (Hoheloogstr., Tevesstr.), or the 3-liter standard (Freyastrasse) were pursued. During renovation, no one was living in the houses [6], [7] and [8]. The key building data are listed in Tab. 2. The measurements were evaluated for Rislerstrasse, Blaue Heimat and Freyastrasse [9], [10], detailed measurements are ongoing for all projects.

The two buildings in Rislerstrasse are three-storey residential complexes built in 1961. Similar layouts and designs allow us to compare the KfW40 energy standard, which was the goal for Rislerstrasse 1 — 5, to the KfW60 standard for Rislerstrasse 7 — 13. The main difference in these two buildings is the ventilation system. The building with the KfW40 standard has an air exchange system with heat recovery, while the KfW60 building has a simple exhaust ventilation system. A 60 kW gas-condensing boiler provides heat with the support of a solar thermal system (24 m2 and 29 m2 with 750 l of buffer storage, 500 l hot water tank).

In Heidelberg, Blaue Heimat is a three-story residential building constructed in 1951 to round off a block; it underwent thorough renovation. The energy renovation concept includes thermal optimization of the building envelope, the installation of a central air exchange system with heat recovery, and a gas-fired cogeneration unit (50 kWel/80 kWth) with a 3000 l buffer tank. This serves two not yet renovated neighbouring buildings as well. The goal was to offset all carbon dioxide emissions over the year to become a "zero house" [7]. Two 92 kW low-temperature boilers were already installed and were retained to cover peak loads. Radiators distribute heat into the rooms.

The project at Freyastrasse 42 — 52 in Mannheim are two-story buildings from the 1930s designed as terraced houses. Each unit has a separate air exchange system with heat recovery. Various systems were used and investigated for the distribution of heat. Overall, five types of systems were studied: three air heating systems with various control systems; a radiator heater; and a panel heating system. A cogeneration unit (Stirling motor 0.85 kWel/6 kWth) and a 185 kW gas-condensing boiler, both of which were installed in an adjacent building, provide heat. Hot water comes from an instantaneous system to reduce losses in storage and distribution.

Measurements were based on the monthly readings of heat counters and power meters (Rislerstrasse 05/06 and 06/07; Blaue Heimat 06/07 [9]) as well as on detailed measurements (Freyastr 05/06 [10]). The heated floor area was used for comparisons of specific consumptions (see Tab. 2). Fig. 2 shows values measured for consumption of useful energy, end energy, and primary energy for heating, hot water, auxiliary energy, and ventilation. Fig. 3 shows the energy flow chart.

M. Kosir1* , Z. Kristl1, A. Krainer1

1 IUniversity of Ljubljana, Faculty of Civil and Geodetic Engineering, Chair for Buildings and Constructional

Comlexes, Jamova cesta 2, 1000 Ljubljana, Slovenia
Corresponding Author, mkosir@kske. fgg. uni-lj. si

Abstract

Automated regulation of building envelope can substantially advance the functioning of its components, consequently improving internal living and working conditions in buildings. The present paper deals with a dynamically automated control of shading in buildings during mid­seasons. The developed automated system is based on fuzzy logic controllers and is installed in purposely build test cell with an opening on the southern side. The system is conceived as a thermal and illuminance controller of internal living and working environment, but for the purpose of experiments presented in this paper only the thermal control loop was used. The focus of presented experiments was the investigation of the influence of shading device automation on the reduction or elimination of cooling loads in buildings during spring and autumn. Proper functioning and fine-tuning of the fuzzy controller was achieved through a series of tests conducted in spring time. Experimental results showed that with adequate level of automation movable shading devices can substantially reduce cooling loads during mid-seasons.

As a consequence internal environmental conditions can be made more comfortable for the users and the energy consumption of buildings can be reduced.

Keywords: automated control, automated shading, fuzzy controller, cooling load reduction

1. Introduction

Internal living conditions in temperate climate during mid-seasons can be in most cases attained by properly regulated building envelope. With adequate shading of transparent parts overheating of internal spaces can be reduced or completely eliminated. During mid-seasons (spring and autumn) the amount of available solar radiation can be high and at the same time the external ambient temperatures can be relatively low. In such conditions the impact of properly regulated shading on the internal temperature can be substantial. Additional positive effects can be attained by implementing natural ventilation and radiative cooling during night time. The automated regulation system presented in this paper was designed according to the above described presumptions about thermal conditions during spring and autumn.

In temperate climate weather during spring and autumn is exceptionally varied and prone to rapid changes. Because of these climatic characteristics the control of movable shading elements has to be automated if adequate response of the system is desired. Automated control of shading devices incorporated in the building envelope has to assure optimum balance between aspects of energy consumption and internal living and working conditions [1, 2]. Best results can be obtained by

applying advanced control systems based on the developments in the field of “artificial intelligence” technologies. One of the possibilities is a system based on fuzzy logic, which (if properly tuned) can be

The presented fuzzy system was realised as a thermal and illuminace fuzzy controller for the internal living and working environment. The basic controller architecture was built around two fuzzy control loops, the first for thermal conditions and the second for illuminance. The controller operated in real­time conditions as well as in real environment. The whole system was designed for an experimental test cell with south oriented window. The dimensions of the cell were 1 m x 1 m x 1 m and the south oriented window was 1 m x 1 m double glazed float glass with air fill and wooden frame. The whole cell was constructed from 20 cm thick aerated concrete blocks with ventilated roof and ground to prevent influences of the immediate surfaces on the interior. The small volume of the cell, large surface of glazing, low accumulation mass and poor thermal insulation meant that the thermal behaviour of the cell would be exaggerated in comparison to real buildings. This was done intentionally as to enable quick execution of experiments where thermal processes in the cell become obvious in relatively short time. The experiments presented in this paper were designed with the intention to test the possibilities of automated shading and reduction of cooling loads in buildings during mid-seasons.

The optimum specific sense temperature is estimated from the result of areal heat load, natural room temperature, and evaporation rate of the perspirable building. For example, Figs.9 and 10 show the relationship between natural room temperature (average in summer) of un-air-conditioned room (B/K and E/U) in Tokyo and the total evaporation rate (in summer) for each specific sense temperature. Furthermore, Figs.11-14 show the relationship between heat load (sensible heat) in summer and the total rate of evaporation (in summer) for various areas and for each specific sense temperature. The result of Tokyo in Figs. 9 and 10 shows that the average natural room temperature decreases and the amount of evaporation become bigger as the sense temperature lowers. Similar tendencies are seen in various areas. From Fig.12, as for the decrease rate of the heat load to the change in the sense

Fig.9 Relationship between average natural room temperature Fig.10 Relationship between average natural room temperature and total evaporation rate in room B/K in Tokyo and total evaporation rate in room E/U in Tokyo

Fig.11 Relationship between specific sense-temperature, Fig.12 Relationship between specific sense-temperature,

seasonal total sensible heat load and evaporation rate in Sapporo seasonal total sensible heat load and evaporation rate in Tokyo

Naha (May-Oct.)
100
80 $ A. 60 40 о Рч > 20
100
80
60
0
Fig.14 Relationship between specific sense-temperature, seasonal total sensible heat load and evaporation rate in Naha
Fig.13 Relationship between specific sense-temperature, seasonal total sensible heat load and evaporation rate in Osaka

temperature (in Tokyo), the inclination is the largest between 30 °C and 25 °С, though the increase inclination of the amount of evaporation becomes also large. 25 °C is considered as one standard of the set specific sense temperature in Tokyo. At the specific sense temperature of 25 °C in Tokyo, the average nature room temperature of LD room decrease by 0.9 °С and the energy-saving rate becomes 28% by autonomous perspiration, as compared to the non-perspiration case in summer. As the optimum specific sense temperatures, 25 °С in Sapporo and Osaka, and 30 °С in Naha can be proposed from the simulation result of Sapporo, Osaka, and Naha, the same way. In this case, the energy-saving rate becomes 65%(Sapporo), 29%(Osaka) at the sense temperature of 25 °С and 18%(Naha) at 30 °С respectively. Moreover, at each optimum specific sense temperature, the average nature room temperature of LD room in summer lowers by about 0.6 °С in Sapporo, 1.0 °С in Osaka, and 0.8 °С in Naha respectively, as compared to those of non-perspiration.

5. Conclusion

As one of the functions of heat dissipation of human bodies, the author took up the perspiration function and applied it biomimetically to passive cooling in buildings. A perspirable building, the walls and roofs of which can perspire with the use of thermo-sensitive hydrogel was developed. The improved perspirable roof to strengthen nonflammability was examined. The details of the perspirable building and the passive cooling effects and energy saving effects by means of evaporative cooling were examined. The experimental and theoretically simulated results of the perspirable building showed that passive cooling effects and energy saving effects by evaporation were great, as compared to those of the building unable to perspire. Further the areal optimum specific sense-temperatures of the perspirable roof with thermo-sensitive hydrogel were predicted by analyzing the simulation results of room temperature and thermal load in a typical Japanese detached house perspirable.

Acknowledgement

The author acknowledges Dr. Ikusei Misaka, Takenaka Corporation, Mr. Hiroshi Oka and Mr. Takeshi Maruyama, Kohjin ^.,Ltd., Mr. Tetsuji Oshibe and Mr. Fumio Tani, Nitto Boseki ^.,Ltd. and, Dr. Hiroaki Kitano, Mr. Takeshi Iwata, Miss Miyuki Moriyasu and Mr. Taichiro Nagatani, Mie University, for their kind cooperation in the execution of the study.

References

[1] Y. Ishikawa et al., Development of a Solar Control Window Utilizing the Seasonal ^ange in Solar Altitude, Journal of Technology and Design, Architectural Institute of Japan, No.6, 1998

[2] Y. Ishikawa et al., Development of a Solar ^nlrol Window with Rotating Blind of Different Thermal Characteristic Slats, Journal of Technology and Design, Architectural Institute of Japan, No.10, 2000

[3] Y. Ishikawa, Passive doling Effect of Water Evaporation in Perspirable Building, EuroSun2006, 2006

[4] Y. Ishikawa, A Study on Simplified Room Temperature Calculation of Multi-room Building Roof Sprayed and Thermal Effect of Roof Spraying (Part. 1), Transactions of Heating, Air-conditioning and Sanitary Engineers of Japan, No.30, 1986

[5] Y. Ishikawa, A Study on Simplified Room Temperature Calculation of Multi-room Building Roof Sprayed and Thermal Effect of Roof Spraying (Part.2), Transactions of Heating, Air-conditioning and Sanitary Engineers of Japan, No.30, 1986

The convection heat transfer between the glass layer of the PV laminate and the exterior follows the Newton’s law of cooling. In 1984, Sharples [16] concluded that the linear correlations obtained for solar collectors, are also valid for ventilated facades. The convective heat transfer between the last layer of the rear glass and the room also follows the Newton law of cooling but the convective heat transfer coefficient is affected by the HAVC system of the building.

4.5 Thermal and Solar radiation. Spectral and angular dependency

The semitransparent PV laminate is divided in two equivalent surfaces: the opaque surface, formed by the sum of the PV cells surfaces and the semitransparent surface, which is the sum of the transparent spaces of the PV module.

The opaque surface has an external glass layer, the EVA layer and the PV cells. The product tau-alpha (та) is the optical property to be determined. The angular dependence was deeply analysed by Parretta

[12] who concluded that an equivalent refractive index, higher than the glass refractive index, must be used. Since reflection at the interface EVA/PV cell is diffuse, the PV absorptance will be independent from the incidence angle and the angular dependence will only affect the transmittance of the glass and EVA joint. The incidence angle modifier (IAMPV) will be used. This IAM will be obtained, for the beam radiation, using Fresnel equations of the air/glass interface.

In the semitransparent equivalent surface an overall hemispherical value has been obtained from the spectral dependency of each layer (glass, EVA and Tedlar). The optical properties of the rear glass are obtained from the TRNSYS database. The angular dependence must include the reflections between the semitransparent surfaces, thus, the net radiation method [17] will be used.

The thermal radiation between the semitransparent surface and the rear glass; between the last layer of the rear glass and the adjacent room and the radiation between the glass of the PV laminate and the sky is determined by solving the net heat transfer between two infinite grey surfaces.

3.3. Low-e coatings

The results of the test box testing of different surfaces are presented as detected light signal versus time. When the signal is high the light beam hits the detector undisturbed and there is no condensation. When condensation occurs the light beam is scattered by the small water drops and the detector signal drops. This is illustrated in figure 2 for three different samples, ordinary glass, low-e glass and hydrophilic (self cleaning) glass. The heating power was dissipated inside the box to generate a realistic heat flow through the glass in order to simulate a real window condition. It can be seen that for the low-e coated glass the signal never dropped, which indicates that no condensation occurred on that surface. For the self cleaning coating and uncoated glass, condensation appeared at the same time, but it disappeared sooner from the self cleaning glass There is also a tendency that the signal for the self cleaning glass is higher than for the uncoated clear float, indicating less scattering. It is, however, not possible to draw any detailed conclusions from the signal level since the illuminated area on the glass surface was very small. In figure 3 the corresponding pane temperatures are shown. The temperature of the self cleaning glass is always the same as for the clear float since the emissivity is the same. It can be clearly seen that the surface temperature of the low-e sample is always a degree or so higher than for the other surfaces with high emissivity, thus preventing condensation.

1st International Congress on Heating, Cooling, and Buildings " ‘ 7th to 10th October, Lisbon — Portugal * Fig. 3 temperature versus time for the samples in fig 2 4.2. Hydrophilic coatings During the period September — December external condensation occurred during 36 days as shown in Fig. 4. We can see some clear trends in the condensation formation. One is that the frequency of full condensation decreases as we move into the winter period, while the frequency of lighter condensation increases. The fact that daytime condensation becomes more common as the days become shorter is to be expected as is the fact that frozen condensation occurs more during winter climatic conditions than when it is milder. During September condensation typically occurred during the night and when the temperature dropped to around 10°C. As we moved into winter the temperature when condensation formed became lower and in some cases condensation actually occurred at sub zero outside temperatures. It should be noted that when condensation was formed it was always formed on both windows, although the appearance was different and the time of evaporation was different. This can be seen in the following photographs.
12
□ ondensation Ш moderate cond daytime frozen
c ф
6
.2 4
c ф c о
2
0
10 month
Figure 4. Frequency of external condensation on the tested windows during September — December 2008

In the morning of September 12, condensation was formed on both tested windows. At 06:20 the hydrophilic properties had started to work. The water had formed a film rather than drops and the view was only slightly distorted, but far from obstructed as was the case for the uncoated float glass surface. At 07:20 all condensation was completely gone from the hydrophilic surface, while the uncoated surface was still full of condensation. This is illustrated in Fig. 5. The bottom picture shows the two windows in the light of the early morning sun. The difference in appearance is quite dramatic. The outside temperature was 9oC. It is not known at which time the condensation was initially formed.

In the morning of October 31, there was condensation on both windows as shown in Fig. 6. The air temperature was zero. It turned out that the condensation was frozen, and hence sheeting on the hydrophilic surface was inhibited. The view was obstructed through both windows in about the same way. A pattern on the Pilkington Activ surface indicates that water has been running down the surface but was frozen during the process. Exactly how this happened was not investigated.

4. Conclusions

The results of these tests clearly indicate that during around 30 mornings with condensation from September to December, the view through the window with the hydrophilic coating was always better than the view through the window with no external coating, except at the rare occasions when the condensation froze. Moreover the condensation evaporates much sooner from the hydrophilic surface. The low-e coating would probably completely eliminate the problem, but it is also important to make sure the transmittance is sufficiently high. Moreover, the hard coatings tend to be slightly rough and tend to be more difficult to clean than uncoated glass. This could be a major disadvantage with this coating on the external surface. These basic experiment verifies that the external condensation problem “created” by modern glass coating technology (low-emissivity coatings) can also be cured by modern glass coating technology (hydrophilic coatings or low-e coatings). None of the tested surfaces is very expensive so that using them on the external surface should be affordable. They both also would have other benefits than the one tested here and are in fact both marketed for other properties.

Acknowledgements

The two windows and the test samples used for the investigation were provided by Pilkington Floatglass AB. The low-e hard coating was Pilkington K-glass and the hydrophilic one was Pilkington Activ. Kevin Sanderson, Pilkington European Technology Centre, Lathom, UK, is acknowledged for his involvement in the project.

References

[1] T. Muneer, N. Abodahab, Frequency of condensation occurrence on double-glazing in the United Kingdom, Energy Conversation and Management, 39(8),717-726, 1990

[2] M. Thyholt, S. Geving, Utvendig kondens pa vindusruter, Norsk VVS: tidskrift for varme, ventilation og sanitaerteknikk, 11, 28-31, 2000 (In Norwegian)

[3] B. Jonsson, Berakning av forekomst av utvandig kondens pa energieffektiva fonster, Technical Report AR 1999:40, SP Byggnadsfysik, Boras (1999) (In Swedish)

[4] H. K. Pulker, Coatings on glass, in: G. Sidall (Ed.), Thin Films Science and Technology, Vol. 6, Elsevier, Amsterdam, (1999)

[5] I. Hamberg, JSEM Svensson, TS Eriksson, CG Granqvist, P arrenius and F Nordin, Radiative cooling and frost formation on surfaces with different thermal emittance: theoretical analysis and practical experience, Applied Optics, vol. 26, no.11, (1987)

[6] A Werner and A Roos, Condensation tests on glass samples for energy efficient windows, Solar Energy Materials and Solar Cells, 91, 609-615 (2007)

[7] A Werner, External Water Condensation and Angular Solar Absorptance — Theoretical Analysis and Practical Experience of Modern Windows, PhD Thesis, Acta Universitatis Upsaliensis, Uppsala, Sweden (2007) ISBN 978-91-554-6830-9

[8] A Werner, A Roos and P Nilsson, Design and evaluation of a detection system for external water condensation on low U-value windows, Sensors and Actuators A, 138, 16-21 (2007)

[9] A Werner and A Roos, Simulation of different coatings to avoid external water condensation on low U — value windows, Optical Materials, 30, 968-978 (2008)

S. Furbo1* and J. M. Scultz1

1 Department of Civil Engineering, Technical University of Denmark, Brovej, Building 118, DK-2800 Kgs.

Lyngby, Denmark

* Corresponding Author, sf@byg. dtu. dk
Abstract

Outdoor long-term side-by-side laboratory measurements during a Danish summer elucidate how much the transmittance for a glass cover can be improved in practice by antireflection treatment of the glass surfaces. The influences of water caused by rain and dew and dirt on the glass surfaces are included in the measurements.

During the test period the solar transmittance for the glass is increased by 8% due to the antireflection treatment of the glass surfaces. The measured transmittances are 2-3% lower than calculated transmittances based on measurements for the clean glasses. The antireflection treatment has no significant influence, negative or positive on the transmittance reduction caused by water and dirt attached to the glass surfaces during the summer period.

Keywords: Cover glass, antireflection treatment, solar transmittance, long term measurements

1. Introduction

Investigations have shown that the transmittance of a clean glass cover is increased by 5-9% by equipping the glass cover with antireflection surfaces by means of a liquid-phase etching by Sunarc Technology A/S [1]. The increase from 5 to 9% depends on the incidence angle. The investigations were carried out for different incidence angles in an outdoor solar tracker.

The surfaces of glass with the antireflection treatment are hydrophilic, which influences the time it takes for water caused by rain or dew to disappear from the surfaces. The hydrophilic surfaces might also influence the amount of dirt attached to the glass surfaces. The transmittances for cover glasses with and without antireflection treated surfaces might therefore in practice be different than the transmittances for the glass covers calculated based on measurements for clean glasses.

This paper describes long term measurements of the transmittance for an antireflection treated glass and a normal glass carried out as side-by-side tests in an outdoor laboratory test facility. The measured transmittances are compared to theoretically calculated transmittances based on transmittance measurements for clean glasses.

Just like for direct night ventilation, in which airflow may be increased at night to bring fresh air into the building, one can also consider preceding systems with airflows more important than the strict minimum air-change value, as long as the ventilation temperature is lower than the building.

Basing an occupation of 2 people per office, the base airflow during occupation is set at 72 m3/h per office (1.3 ach), dropping at night to 6 m3/h (0.1 ach).

As an alternative, we will also consider following 3 options of controlled flow:

• Same nominal flow (72 m3/h), however also activated at night if the ventilation temperature is fresher than the building.

• Twice the base flow (144 m3/h), activated according to the same thermal condition (else reduced to the base flow).

• Four times the base flow (288 m3/h), activated according to the same thermal condition (else reduced to the base flow).

Such increased ventilation strategies imply adapting of the storage sizes, as well as adapted distribution systems (ducts and fans). They also imply electric overconsumption, which is to be kept as low as possible. While we will limit our study to the thermal contribution of these systems, we stress that the problem of electricity should eventually be studied carefully.

2.2. System integration and control

Since the investigated systems base on day/night charge/discharge, they must be irrigated 24/24 h. Control of the airflow injected into the building hence must take place by way of a valve at storage exit, with an upstream fan always running at nominal capacity.

At night, because of dampening or phase-shifting, temperature at storage output is warmer than ambient. Instead of single-mode operation, these storage devices may hence also be used in

alternative mode with direct night cooling from ambient, with a control strategy injecting air into the building from which ever cooler source. Because of continuous irrigation of the thermal storage, such a strategy however requires a second fan for direct night ventilation.

We shall finally explore the potential of evaporative cooling, as a complement to inertial or direct ventilation. Latter potential will be examined for a constant 50% efficiency (humidification up to 50% of the potential given by the differential between dry and wet bulb temperatures).

Latter configurations will finally be evaluated both for the case of a free-floating building, as for backup by auxiliary cooling during occupation (26.5°C set-point).

3. Simulation

Simulation over the summer period (May-September) is carried out in two steps, with an automated overall approach:

• For each of the four meteorological data sets, the storage systems are pre-simulated for constant airflow, by way of specific analytical models developed previously [4, 5].

• Control of the systems, humidification and building response are then simulated within Trnsys.

C. U. OKUJAGU

department of Physics University of Port Harcourt, P. M.B 5323 Port Harcourt Nigeria.

info@okujagu. com

Abstract

Analysis of photomicrographs and spectral transmittance characteristics of some single metal Suphide and halide films reveal that there is a physical relationship between the material’s structure and the photo-optical properties the nucleation pattern during growth and the area of application of the films. Some important areas of application of such films are:- Spectral splitters, protective coating and selective window coatings. It was observed that sulphides of silver and lead which have very large grain that tends toward continuous films can be used as infrared transmitting spectral splitters for heating plants in conventional green house agriculture (CGHA) and continuous environment agriculture (CEA), since they can absorb all UV-VIS radiation but transmit NIR radiation into the green house. Lead Halide films which have moderate grains that are more uniformly spread show partial UV-VIS transmission and partial VIS and NIR reflection from about 650nm and can be used as photo thermal protective coating for photovoltaic solar cells. Tin and manganese Halide films with smaller compacted continuous structure show high UV absorption at 359nm, high NIR reflection at 850nm and high visible transmission from 350nm to 850nm hence can be used as cooling coating for warm climates.

1. Intriduction

The concept of structure of thin films has different aspects which are varied with respect to their morphology (mono or poly crystals or the so called amorphous structure) [1-3]. It may also indicate the crystalline structure or the geometric exterior of films [1]. In terms of crystalline structure, it may be necessary to define the nature of films i. e whether the films consist of mono or poly — crystals or are amorphous. If materials are crystalline, it is also necessary to determine the size (nanocrystals or microcrystals), shape (oval, circular, or clinical), orientation and grain boundary of the crystallite units, [2, 4-5]. It may also be useful to introduce density n (r) of crystalline atoms as a function of the distance (r) from a chosen atom [4]. For poly-crystals n(r) is not an isotropic function. Hence in the direction along the lattice row (h, k, l) there is an equidistance maxima at the site of the atoms. This indicates high order in the crystal [1]. In a very fine crystal powder with units consisting only one elementary cell, n (r) however is an isotopic function of r. For such crystals “short range” order still persists in the immediate neighborhood of an atom, where as the long range order has disappeared [1]. On the other hand, the exterior geometry of films has to do with the surface microstructure of the films [2, 4]. Such structures include grain size distribution, grain boundaries, grain shape, grain orientations, nucleation patterns during growth of films and the surface smoothness or otherwise of the films. The grain size with all the grain size properties are the most widely used expressions for the geometrical exterior (surface microstructure) [2]. This is because they are somewhat representative of the geometrical features of films and have profound influence on the properties and behavior of materials (such as spectral behaviour), more than the other structural parameters of the film [3-5]. The grain size of films and materials is exceptionally important also because it can be used to analyze or compute the other grain size distribution

properties where direct measurement technique is not available. Although grains are three­dimensional features, their size and properties are also normally estimated by one — or two — dimensional measurements on planar surfaces through the specimen volume. Hence a wide range of parameters can be used to describe grain size [1-8]. These are:

Average grain diameter d,

Average grain area A

Average number of grains per unit area, N A Average intercept length L 3

Average number of grains intercepted by line of a fixed length, N Average number of grains per unit volume, N r, and Average grain volume L v

Of these descriptions of grain size, only the last two spatial parameters provide a measure of the true grain size and grain size distribution [1]. The others are planar parameters and they are based on measurements of various geometrical parameters of the microstructure, which change as the spatial grain size is altered. For example, the first three parameters provided a single number estimate of the grain size, which is useful for structure-property correlation, but give no information about the grain size distribution. Hence grain parameters are actually measured and expressed in terms of the parameters together.