Once built, the Solar House will be used as research stand; the building (materials, structure, design) represents a set of un-changeable variables, while the hybrid thermal system management, for thermal comfort is subject of monitoring and optimization.

The steps to be followed are thus:

• Climatic data acquisition and refining;

• Energy input/output data acquisition and analysis, for the three systems: solar-thermal, heating pump and PV;

Thermal energy calculation, emphasizing the contribution of the renewables:

+ EHP +) = Egas

By careful management of the solar-thermal and heating pump outputs the energy used from the back-up source has to be minimized towards zero.

If not feasible, for extreme winter temperatures (below -25oC) than the re-design of the solar-thermal system and of the heating pump must be considered focusing on the optimal ratio between the two heating sources.

• Electrical energy calculation: AEtotal = Eused — Ereceived = Eused — Epv

The Solar House will host the research laboratories with rather large energy consumers. Thus, regarding the power consumption, the data will give answers to the best use of the renewable energy in the field climatic conditions.

The use of power control management systems in reducing the global energy consumption represents a further development step.

The initial sizing, based on software use, of the solar-thermal and heating pump systems considered all the materials and design data. The research must also give answers to the questions related to the use of modelling software: the degree of reliability of the simulated data vs. the concrete measurements and the consequences at technical, functional and financial levels, when adapting the design to concrete climatic data.

2. Conclusion

The integrated use of solar-thermal, heating pump and solar PV systems can support the low energy building concept, for residences with an adequate architecture. The paper presents the application of this concept in the Solar House in the Centre Product Design for Sustainable Development, Transilvania University of Brasov. The Solar House acts as a research stand and allows design optimisation. The research opens opportunities for various combinations of the three renewable energy systems, according to the beneficiaries needs and adapted to specific climatic conditions.

References

[1] EU Parliament and Council, Directive COM(2008) 30 final.

[2] D. J. Treffers, et al., Energy Policy, 33 (2005) 1723 — 1743.

[3] B. de Meester, et. al, Building and Environment, (2008), doi:10.1016/j. buildenv.2008.01.004

[4] Baden, S., et. al Proceedings of 2006 ACEEE Summer Study on Energy Efficiency in Buildings, American Council for an Energy Efficient Economy, Washington DC, August 2006

[5] W. W. Clark, Larry Eisenberg, Utilities Policy, (2008), doi:10.1016/j. jup.2008.01.009

[6] V. Badescu, B. Sicre, Energy and Buildings, 35 (2008) 1085-1096

[7] Y. Wang, et al., Applied Energy, 83 (2006), 989 — 1003

[8] X. Xu, S. Van Dessel, Building and Environment, 43 (2008), 1785 — 1791

[9] F. Cuadros, et al., Energy and Buildings, 39 (2007), 96-104

[10] G. A. Florides, et al., Energy, 25(2000), 915-937

[11] I. Visa, A. Duta, Bulletin of the Transilvania University of Brasov, BRAMAT Proceedings (2007), CD

[12] I. Visa, et al. Proceedings of the 22nd European Photovoltaic Solar Energy Conference, Milano, (2007), CD

2.1. Day/night storage systems

As an alternative or in conjunction with direct night ventilation, we will consider two types of passive cooling systems based on thermal storage of the meteorological day/night oscillation that is carried by ventilation (fig. 2):

• The so-called air-soil heat exchanger, in which the air passes through an array of pipes buried under or next to the building, for the meteorological day/night oscillation to be dampened by charge/discharge in the soil. The daily heat wave propagation extends on approximately 15-20 cm around the pipes, so that latter can be arranged in a compact geometry, with inter-axial distance of approximately 50 cm, immediately under the building, and if necessary in multi­layer.

In the case of our study, we choose pipes with 12 cm diameter, for a specific flow of 100 m3/h per pipe (2.5 m/s). With such a configuration 10 m of pipes make it possible to reduce the

day/night amplitude to 41%, and 20 m of pipe to 17% (exponential damping), for a phase-shift which remains lower than an hour.

• The thermal phase-shifting device, in which the storage material is homogeneously distributed within the ventilating duct, in order to increase the heat-transfer surface and to decrease the penetration distance to thermal mass. Providing a homogeneous airflow and a good convective exchange, it then becomes possible to delay the day/night oscillation almost without dampening, for the night cooling peak to be available in the middle of the day.

In the case of our study we choose a storage material consisting of 13/16 mm diameter PVC tubes that are filled with water, piled up perpendicular to the airflow, with a 2 mm spacing between tubes. With a duct cross-section of 50 x 50 cm subject to a specific flow of 100 m3/h (0.39 m/s average interstitial velocity between tubes), the system enables an 8 h phase-shift with

1.6 m length, respectively a 12 h phase-shift with 2.4 m (linear phase-shifting), for a residual amplitude higher than 80%. This system hence not only differs from the buried pipes in terms of thermal behavior, but also in terms of an almost 10 times inferior storage volume.

First of these systems was subject of several case studies and theoretical analysis [2, 3], whereas second arises from a theoretical work that gave rise to recent lab developments [5]. They have both been object of theoretical developments, in particular in term of well validated analytical models [4, 5], which are used in this study.

Tables 1 also show that radiation attenuation parameters R, n, k, a, ax and xa all decreased with wavelength between 0.3 to 0.8 gm and then increased with wavelength beyond these wavelengths for these films. The parameters were found to increase with increasing thickness (Tables 2). In general, these parameters were high in the UV and NIR region but low in the visible region. This seems to confirm the fact that these films are opaque to UV and NIR radiation, but are transparent in the visible.

Again, for Snl2 film of thickness 11.7 x 10-9m, the absorption coefficients are around 6.2 to 3.2 x 106m-1 in the UV and from 1.1 to 3.3 x106m-1 in the NIR. The values of absorption coefficient for MnBr2 and FeCl2 are similar. Absorption peaks were found to occur around 325nm for Snl2, 323 for mnBr2 and 420 forFeCl2. the values of the absorption coefficient in the visible are as low as 0.6 to 2.2 x 106m-1 for Snl2 film, and 0.7 to 2.8 x 106m-1 for MnBr2 films. For FeCl2 film, it is from 0.12 to 5 .3 x 106 m-1. The optical constants n and k increased markedly with wavelength, especially around the absorption peaks. Fig. 4 shows a sample of variation of n and k with wavelength for these films. The figure shows that both n and k decreased exponentially with wavelength in the visible region. Hence these films behave like

transparent insulators [63]. The shape of the transmittance/absorbance curves (fig.2) and the values of the transmission parameters and attenuation parameters show that halides of manganese exhibit properties that would make them better candidates for visible transmitting films. These films have broader-band high UV absorption. This means that all UV radiation will be absorbed by such films. They also have high visible transmission which means that they will allow high level of visible transmission. Their NIR absorption is also high enough to shut off high temperature radiation.

The UV and NIR absorption of Tin halide films (fig.1) are not high enough to cause complete extinction of these radiations. Although these seem to have improved visible transmittance, their UV and NIR absorption would allow substantial high energy and thermal radiation to be admitted into buildings interiors. This may cause unnecessary overheating which will be unwanted in cases where very low in door temperature is the emphasis. When moderate temperature is the demand, Sn halide films will be deal. On the other hand, Fe halide have complete near UV absorption over a very narrow band. Also, their visible transmittance starts later in the spectral region well into the visible (i. e. from about 550 nm as shown in fig.3). Also, the visible transmittances are not as high as those of Sn or Mn halides. Thus, these films might allow some unwanted radiation into the building from the NIR and also suffer from loss of visible radiation. Hence ‘day light’ level might be low for these films. They might therefore be useful in situation where day lighting is not of great importance and where moderate temperature is the emphasis.

Table 3 shows that maximum visible transmission decrease with thickness only for films of the same type. No such variation exists between thickness and transmission for all the films viewed together (Table 4). These result shows that both the materials concerned and the thickness of film play important roles in determining the optical properties of films. It was also observed that thickness affect both the wavelength of the onset of absorption and the wavelength of absorption threshold. Hence thicker films have lower onset of absorption but higher fundamental or threshold wavelength. Thinner films have higher onset of absorption, but lower threshold wave length as shown in Fig. 1-3 and in the table 5. Thus the wavelength of onset of absorption decreases and shifts well into the UV region with increasing thickness. These relationships between thickness and onset of absorption and fundamental wavelength exist only for films of the same materials and not for all the materials viewed together. It was also observed that Fe halide films and even Mn halide films exhibit colour changes with respect to transmitted and reflected lights. These films might therefore be also useful as phototropic materials [3, 62-64].

3. Conclusion

Analysis of the optical parameters of Sn, Mn and Fe halides show that these films are transparent in the visible but opaque in the UV and NIR regions. Such films can be used as optical shutters to UV and NIR radiation but as transmitters to visible radiation. These films are therefore designated in this work as visible transmitting films VTF. They could be used as selective coatings for building windows. Such windows would be capable of shutting off high energy (UV) and high thermal (NIR) radiation but admit only visible radiation for “daylighting”. Window with these properties could be used in warm climate where emphasis is on warding off UV and IR radiation and admitting only visible radiation into buildings. This will create a comfortable cool and conducive indoor temperature environment. Thus a kind of natural air-conditioning can be achieved by using these VTF coated windows. Fe and Mn

halide films which also exhibit colour changes with respect to transmitted and reflected lights could be useful as phototropic materials.

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Energy analyses of solar faqade collectors and systems behaviour usually come from ideal south orientation of collectors without influence of shading by close objects. However, faqade collectors are more exposed to possible shading problems compared to roof installations. Solar collectors integrated into the building faqade in urban environment could encounter problems of providing sufficient yearly solar irradiation on the surface due to existing or potential future shading by close objects. This issue should be considered in early design procedure and coordinated with urban planning to guarantee the solar energy access to the building faqade by means of geometric relationships through distances among the buildings and their heights, orientation of streets and obstacles producing the shades (artificial, natural). The situation when the solar faqade installation cannot be built up due to unsuitable parameters (e. g. shading problems) or even the already built solar installation is disvalued by subsequent urban development should be avoided. The possible reduction of solar energy incident on the faqade collectors by static shading (neighbouring buildings) or variable shading (surrounding high-grown vegetation) can critically affect the overall energy performance and economic parameters of designed solar system. The problem of faqade shading is more accented in the city centres or dense housing estates due to higher concentration of high-rise buildings than in family houses districts. Presented shading analysis is therefore focused on urban environment in larger housing estates.

Two of the most promising technologies for efficient use of fossil energy are the Combined Heat and Power plant (CHP) and the high performance heat pump. In The Netherlands, several small (micro) CHP plants are available for application in dwellings. In analogy to high efficiency boilers, a so called HRE quality mark is being introduced for units with a Primary Energy Ration (PER) of 140% or more.

Alternatively, state of the art heat pumps achieve a Seasonal Performance Factor (SPF) of 2.5-3 for DHW and 4-5 for space heating. Assuming an electrical efficiency of 50% in the electricity plant, this translates to a PER of 140% for DHW and 220% for space heating. Application of such a unit with a thermal output in the 2-5 kWth-range would save an additional 15-20 kWh/m2a in our terrace dwelling.

2. Summary

Table 2 below summarizes the effect of the different scenarios. The first scenario is the base case consisting of the Passive House concept plus a 3 m2 vacuum tube solar collector and a 150 l storage

vessel. Additionally, in case 2 domestic electricity is reduced by 39% using standby killers and A-label appliances. Here, innovative measures such as low energy coolers are not yet included. Most of the measures in scenario 2 fall under the first step of the Kyoto pyramid. The target of 75% reduction can be reached by adding 16 m2 of PV modules in optimum orientation.

In scenario 3, the area of the solar collector is increased from 3 to 8 m3 and the storage vessel from 0.15 to 0.6 m3. In this scenario, the target is nearly reached and only 4 m2 of PV are needed to reach it. Of academic interest is that a 16 m2 collector will reach the target without the need to install any PV.

Finally, replacing the boiler with a high efficiency heat pump will help reach the target without the need for additional PV cells.

5. Conclusion

A reduction of 75% of the total (primary) energy consumption in a Dutch terrace dwelling appears very well possible with an integral approach based on the Passive House concept in combination with a solar collector to maximise the amount of passive and active solar energy. In addition, standby killers and application of label A appliances are applied to substantially reduce the electricity consumption.

As a final touch, the application of either 4 m2 of PV cells or the application of a high efficiency heat pump will help reach the target. More innovative measures are being studied, but their effect is not included in these results.

The project is supported by SenterNovem in the EOS-LT framework (Energy Research Subsidy, Long Term).

References

[1] http://www. passiv. de

[2] Opstelten, I. et. Al (2007). Potentials for energy efficiency and renewable energy sources in The Netherlands, World Sustainable Energy Days, Florence.

[3] http://epp. eurostat. ec. europa. eu

[4] Basisonderzoek Elektriciteitsverbruik Kleinverbruikers (2000), EnergieNed

[5] W. Weiss et. al., Solar Heat Worldwide edition 2008, Solar Heating & Cooling programme,

International Energy Agency

[6] NEN 5128 Energieprestatie van woonfuncties en woongebouwen-Bepalingsmethode, ICS 91.120.10,

March 2004

The detailed evaluation of the 23 questionnaires returned by the LESO-SEB occupants made it possible to get a good understanding of which typical lighting related problems may be bothering occupants in ADS-equipped offices the most. The MAV and nconcerned-values as defined in Subsection 3.1 are used in Table 1 to quantify the annoyance of different typical problems. First of all, we observe that the maximum MAV is 34% and the maximum number of directly concerned occupants nconcerned is 6. These low values underline the general impression that occupant

satisfaction within the examined ADS-equipped is quite good. Furthermore, Table 1 shows that all problems scoring MAVs of 20% or higher are related to situations where too much daylight is bothering the occupants. Specific interviews with the six concerned occupants revealed that four of them manage to quickly “resolve” those “daylight overprovision”-problems using the blind systems in most cases. Two of them, however, found it not so easy to quickly resolve these problems. When looking at the nconcerned-value of problem 6, one might find it surprising that it equals 3 instead of 2. This means that there is one occupant who is not particularly annoyed by “daylight overprovision”-problems, but who still feels that those problems are not so easy to resolve in the rare cases where they occur. Agreement with problem 5 was found to be 17% with three directly concerned occupants. Those three occupants were found to often work with completely lowered window blinds and do therefore often not benefit from the advantages of their daylighting systems. The workplace of the person directly concerned by problem 7 is located at a considerable distance from the window.

An energy balance is applied in each node and is represented by a network thermal resistance as we can see in Figure 2.

 

T 1 T я.

 

Fig. 2. Thermal network for the solar chimney.

Following the methodology reported by Ong [7] and Duffie and Beckman [8], the energy balances produce a system of 5 algebraic equations, and such equations can be expressed as the following array (1):

Where column [Tg, b Tg,2, Tw, Tf, b and Tf2], is the unknown temperature vector. It represents the both glass cover temperatures, the metallic vertical plate temperature, and both air fluid temperatures respectively.

The temperature vector is calculated by solving the matrix system. All the heat transfer coefficients are determined from the literature references, as well as the optical properties for the materials, Table 1 shows these values.

Where every coefficient is defined in the nomenclature, for i = 1, channel one, and for i = 2, channel two. The convective heat transfer coefficients for natural convection, are determined after applying the Nusselt correlation, for laminar flow, equation (2), for turbulent flow, equation (3),

[10] .

Nut = 0.68 + (0.67Ra.025)/[1 + 80.492/Pr)9/16J/9 Ral < 109,

N. = {0.825 + (0.387Ra 11<5)/[1 + (0.492/Pr)9/16fmf Ra > 109,

Prandtl number, Rayleigh number, and Grashof number are defined by equations (4), (5) and (6) respectively.

The volumetric coefficient of expansion /3, is defined by equation (7), and it is evaluated at a mean temperature by equation (8). All thermophysical properties are evaluated at T.

Pf, t = 1/Tm„ , IS (1/K) T + T )

g,1 w, t

2

The top loss coefficient and the wind heat transfer coefficient are evaluated by equations (9) and (10), respectively, where V, is the wind velocity in (m/s).

h = 5.7 + 3.8V

The radiation heat transfer coefficient from the glass cover to the sky, is evaluated by equation

(11) , where T is the sky temperature, defined by equation (12).

h = os (T + T)(T2 + T2)(T — T)/(T — T )

rs, t g ,t g, t s g, t s g, t s g ,t a, t

T = 0.0552 Г5 (12)

The solar irradiance covering the glazing, and the transmitted solar irradiance covering the metallic plate, at both sides, are defined by equations (13) and (14), respectively.

sg, t = ag, tG (13)

S =t a G (14)

w, t g, t w, t

It is convenient to defined an aspect ratio At and a theoretical parameter Mt by equations (15) and (16) respectively.

The mass flow rate through each channel of the solar chimney was determined by using an equation proposed by Bansal et al., [11], equation (19).

РоЛл l2SLc fat — T )

л,/1+а;д

The thermal efficiency was determined using the following equation, (20), [7]

m c, ІТ — T )

n = GG *100

WLG

In order to allow an easy application and implementation of the program, a documentation “solar kit” has been developed.

The “solar kit” includes a guideline document and a standard format for public calls for tenders based on quality and reliability as key-criteria for design and installation. This first outcome can be surely considered a valuable step towards the standardisation of the solar integration procedures, even though many aspects still have to be faced.

The guideline document for the implementation of the Programme is addressed to the jails Directorates and to the technicians who have to arrange the tender and evaluate the proposals.

The main aims of this document are:

• Explaining and making clear the administrative procedures for the Programme implementation;

• Defining the prisoners training contents and activities;

• Providing useful instruments and criteria for the compilation of the call for tender and, more in

general, for the comprehension of the solar thermal plants operation’s principles.

Within the “solar kit”, besides the guidelines, the jails Directorates receive also all the documents useful for the correct execution of the Solar Programme and in particular they are provided with:

1. The “Prisoners Standard Training Programme” for achieving a qualification certificate as “Solar Thermal Plant Installation and Maintenance Operator”;

2. A “Standard Technical Inspection Questionnaire” for the collection of data on heat demand quantification and on site characterization;

3. A “Standard Contract Specifications”;

4. A “Standard Technical Specifications” for solar thermal plant design, provision and installation.