Category Archives: BACKGROUND

Previous Projects

The Fraunhofer Institute for Solar Energy Systems (Freiburg/Breisgau, Germany) and the company UFE Solar GmbH (Berlin, Germany) started with preliminary tests and first investigations concerning seasonal heat storage based on the adsorption process in 1995. Research work was continued with financial aid of the European Commission and the Austrian Federal Ministry of Transport, Innovation and Technology (BMVIT) in the project HYDES (High Energy Density Sorption Heat Storage for Solar Space Heating). In this project, the principle technical feasibility of the sorption storage system was proved. The experience gained during this project will be of use in the frame of the new project MODESTORE which is also funded by the European Commission and on the Austrian national level by BMVIT. The work in this project started in April 2003 and will be continued for three years.

Basic Principles of an Adsorption Heat Storage System

In sensible and latent heat storage devices heat is stored together with its
corresponding amount of entropy. In these so-called direct heat storage media, heat

— i. e. energy — is transferred directly to the storage medium. The achievable energy density is limited by the entropy storage capacity of the material. Otherwise the adsorption process is a reversible physico-chemical reaction suitable to store heat in an indirect way. This kind of thermal storage allows to separate energy and entropy flow. The storage capacity is not limited to the maximum of entropy intake. The energy density can be much higher if entropy is not stored directly in the medium. Therefore a heat source and a heat sink is involved both during the charging and discharging process to withdraw or collect the necessary entropy. The storage works like a heat transformer on the principle of a chemical heat pump. During adsorption of water vapour, a phase chance takes place between vapour and liquid phase on the surface of the in this project used silica gel. The released adsorption enthalpy consists of the evaporation enthalpy of the working fluid and the binding energy of the adsorption pair.

The working principle involves several different phases illustrated in figure 1 and described below:

1. Charging process (desorption, drying of silicagel): heat from a high temperature source is fed into the device, heats the silica gel and vapour is desorbed from the porous solid. The desorbed vapour is led to the condenser and condensed at a lower temperature level. The heat of condensation has to be withdrawn to the environment.

2. Storage period: the dry adsorbent is separated from the liquid working fluid (the connecting valve is closed). As long as these components stay separate heat storage without losses is possible if the sensible heat involved is neglected.

3.

Charging

Storage

Discharging

Desorption

Adsorption

High temperature heat

Water vapour

Low temperature heat

Condensation

Water vapour

Liquid

water

Evaporation

Low temperature heat

Discharging process (adsorption, loading of silica gel with water vapour): the valve between the evaporator and the adsorber is opened. The liquid working fluid evaporates in the evaporator taking up heat at a low temperature level. The vapour is adsorbed and releases the adsorption heat at a higher temperature level. This is the useful heat.

Figure 1: The working principle of an adsorption heat storage.

There are several quantities and process parameters important when the potential energy density of a sorption pair for heat storage applications is evaluated. The main ones are:

1. Temperature lift: it depends on the current loading level of the sorbent and is a material property.

2. Adsorption enthalpy: it consists of the evaporation enthalpy of the working fluid and the binding energy of the adsorption pair. A high specific evaporation enthalpy is a must for high energy densities, therefore water is one of the primary candidates.

3. Sensible heat and process management: an intelligent system design and process management along with good insulation is essential.

4. Energy density: the energy per unit volume is the quantity of primary interest. It is the product of specific energy (energy per mass of sorbent) and the bulk density ps.

After due consideration, the process of thermo-chemical heat storage with the adsorption pair silica gel and water was selected. Silica gel is a very porous and vitreous substance. The material is made up mainly of SiO2 and is extracted from aqueous silicic acid. The equipment installed in the laboratory of AEE-INTEC in Gleisdorf/Austria is filled with commercial silica gel GRACE 127 B. This silica gel consists of spherical particles with a diameter of two to three millimetres. Its bulk density is 790 kg/m3, the interior surface is 650 m2/g. The high energy density, the quantity of primary interest, is achieved by a high evaporation enthalpy, the polarity of water and the large interior surface of silica gel. Additional components like heat exchangers reduce the energy density if the whole system is considered. The system is evacuated to enable water vapour transport without use of mechanical energy. The vapour pressure add up to 10 to 50 mbar in the system.

Monitoring: Energy Balance

The analysis of the temperature performance can be combined with the energy balance of the building. Table 2 shows the essential values required to evaluate the thermal building performance in summer.

The heat gains can be taken directly from measurements (i. e. internal heat gains) or have been calculated (i. e. solar heat gains) from the building geometry, material properties and meteorological data.

The heat losses are mainly caused by ventilation. Consequently, the air change rate determines the heat loss in each building. (Notice: The Lamparter building gets additionally cool supply air from an earth-to-air heat exchanger during the working hours.)

The heat storage capacity is (almost) identical in each building for the daily period. Since the building constructions are very similar, the heat storage capacity for longer cycle periods are (almost) identical, too.

Table 1: Energy balance (working days) room temperature (only working hours) for the

summer period 2002 and 2003.

Lamparter

Pollmeier

Fraunhofer ISE

heat gains (internal + solar)

252 Wh/(m2 d)

184 Wh/(m2 d)

282 Wh/(m2 d)

mean air change rate (day)

4 — 7 h-1

2 — 3 h-1

3 — 5 h-1

mean air change rate (night)

6 — 8 h-1

1 — 6 h-1

5 — 8 h-1

heat storage capacity

25 Wh/(m2 Kbhrs

25 Wh/(m2 K) 24hrs

25 Wh/(m2 K) 24hrs

2002 2003

2002 2003

2002 2003

ambient air temperature [°C]

21.4 23.6

21.8 24.2

22.5 27.0

room air temperature [°C]

23.4 24.8

23.2 24.6

24.6 27.4

temperature difference [K]

2.0 1.2

1.4 0.4

2.1 0.4

On the one hand, it was found in the previous Section that all buildings responded to changes of the ambient air temperature faster in 2003 than in 2002. Obviously, the buildings’ thermal inertia could not compensate for the high ambient air temperatures because the available heat storage capacity had been already utilised completely. On the other hand, the excess temperature is smaller in 2003 than in 2002.

Theoretical study

Simulation is a powerful tool to evaluate and optimise the system design. Accuracy of the performance of any model depends on the algorithm used and the accuracy of the data used.

The model was created using standard TRNSYS v. 15.0 components [1]. TRNSYS is an acronym for a ‘transient simulation program’. The model output is the free floating indoor air temperature. Model input variables are: the global and diffuse horizontal radiation, the outdoor air temperature and relative humidity and wind speed. The model includes the parameters describing the building which mainly concern the components geometry, materials thermophysical properties and surfaces optical properties. Thermophysical properties of the building materials and glazing optical properties are selected from [3]. Model simulation has been carried out using the measured input variables averaged and under-sampled at 1 h time step.

The floor has been treated as a wall with boundary conditions connected to the outdoor air temperature through an added insulation layer. The resistance of this added insulation was calculated as a function of the path length of the heat transfer through the soil layer using a technique recommended by [1].

Infiltration considered as air change rate has been averaged by a simple, single-zone approach based on the Lawrence Berkeley National Laboratory model (Sherman and Grimsrud 1980), indicated in [1]. This calculations are subject to high uncertainty, [1] indicates that: "The model has exhibited average errors on the order of 40% for many measurements on groups of houses and can be off by 100% in individual cases (Persily 1986)”.

An equivalent homogeneous multilayer wall is used to represent the ceiling. The soil reflectivity is supposed to be 0.2 and standard values for the convective heat transfer coefficients are adopted. The indoor air temperature is supposed to be homogeneous. When simulating a building in transient regime initial conditions must be specified. A estimation has indicated three days to reach the steady simulated thermal behaviour. Therefore the first three days has not been considered for analysis.

The time evolution of the simulated indoor air temperature is presented in Figure 8, its means is 20.1 °C and its standard deviation is 1.2 °C.

There are many sources of uncertainty when using modelling to assess the thermal performance of a proposed building. Sources of uncertainty can be categories as [10]: abstraction (concessions made to accommodate the design to the computer representation, e. g. building geometrical simplifications), database (the element to be modelled may not mach the information contained in the database and assumptions have to be made), modelled phenomena (simplification on the physical processes modelled, e. g. thermal contact with the ground), solution methods (e. g. in resorting to numerical discretisation techniques a discretisation error is introduced to the solution).

Studies have shown that the uncertainties can be quite substantial on model results. Uncertainties will be analyze in future works.

Illumination control loop

This means that the main fuzzy controller, considering the measured external and internal conditions and set point values as inputs, Fig. 3. Example of a 3D surface for non-linear

determines the set point mapping between inputs and output as fuzzy model

position of the roller blind as implemented in illumination fuzzy controller. output. PID controller is of type

PID/V, which means that it executes the velocity PID algorithm, and the output value defines the dimension for which the actuator must change its current position. In our case this means the alternation of the roller blind position. The input values for PID/V are: the desired position of the roller blind, which is defined as output signal of the main fuzzy controller and the temporary measured position of the roller blind. The output signal is calculated from the current difference between the desired and the measured roller blind position. The output signal provokes the appropriate movement of the actuator, i. e. roller blind. The main illumination fuzzy logic controller has two inputs: set point inside illumination and the difference between the inside illumination and the set point illumination. A decisive factor for window geometry alternations is "illumination” fuzzy controller with proper semantic background. It is also important to set properly the other parameters in the algorithm: parameters of the PID controller, filter time constants, sampling times and priorities of the loops.

Possible illumination oscillations are in the range of 1000 to 5000 lx or even more in short time periods. Therefore, it is more difficult to achieve efficient daylight regulation than thermal regulation. The two filters realized in filter blocks are included to damp the possible too fast and frequent oscillations of the roller blind movements caused when the external solar radiation is extremely changeable. Proper setting of the filter time constants means smoother roller blind movement. We want to exclude too frequent roller blind moving, since it is annoying to the occupants.

The first step in designing the fuzzy controller is to specify the control input and output variables and the domains for these variables. Fuzzy partitions including the corresponding linguistic terms have to be specified for these domains. This means that the unit intervals are completed with membership functions (fuzzy subsets), i. e. membership degrees are assigned to numerical values. The number and the shape of the membership functions for each variable must be defined. For the purpose of the control engineering the triangular membership functions are used. In our case the Sugeno type (IDR BLOCK

Fuzzy Logic Controller Designing Tool, 1999) of the controller is used, where fuzzy partition is done only for the input domains. These fuzzy partitions and the linguistic terms associated with the fuzzy sets and subsets represent the database of our knowledge base. The next step is to define the control rules using the linguistic terms associated with the fuzzy sets as they appear in the fuzzy partitions of the domains. On the basis of the preliminary experiments and observations of the optical process in the test chamber, the set of linguistic rules is designed for the control of the roller blind positioning to maintain the desired inside illumination. Methods to design the fuzzy controller are crisp; the obtained control function is always crisp.

The first approximation of the fuzzy controller does not result in an optimal control behavior. To improve the control behavior, tuning of the fuzzy controller through iterative procedure of experiments is necessary. The changes are considered depending on how well the fuzzy controller is able to handle the process. The possible modifications are: Redefining the domains of the variables. The adjustment of fuzzy sets offers several possibilities: changing the fuzzy partitions of the domains, adding and deleting membership functions, reshaping and rearranging membership functions. For each fuzzy variable up to seven memberships functions can be included.

• Alternating the rules in the set.

• Exchanging the logic operations in some rules, i. e. choosing other logic operators.

• Adjusting the consequences of the individual rules.

The redesign is necessary, when the controlled variable (in our case inside illumination) deviates too much from the set point values. With a trial-and-error optimization of the designed fuzzy controller the control performance is improved.

THE DAYLIGHT PROJECT

The good project for daylight application should be made in an early phase of the project so to get a good level of integration [6]. It is important to know the characteristics of lighting that the room required, the activity that is supposed to be performed inside, the right position of the standing people and so on. Only when all these variables are well known it is possible to determine the sizes and the shapes of the transparent components, giving the quantity of natural light and their distribution in the wall [7].

At the end the whole lighting project should be checked by using of tables, plots abacus and codes [8].

The standard gives the formula to calculate the Daylight Factor:

DFm = Af x Ti x e x у / [( 1-pim) x Atot]

Af glass surface of the windows [m2]

Ti glass transparency

e window factor (ratio between the

window lighting and the sky radiance) у window factor reduction coefficient

(dependent on the protrusion of the wall respect the window) pim indoor surface average reflection

value

The transparency is the value of the optical transmittance for the PV component as it has been measured, depending on the optical transmittance of the transparent part and on the cell density.

In our case a project for the refurbishing of an health centre for mental disease to an university campus, with parts of the buildings available even to the inhabitants of the town.

Figure 4. A pictorial view of the intervention. The PV facades are the black zones.

In particular that building will be partially destroyed and then rebuilt, but keeping the original look by keeping the pristine outside walls, see figure 4.

In one block two PV plants will be installed in the facade acting as a sun screen by using the glass/glass technology and the spacing of the cells.

In the first case the PV modules will develop around the length of the building and should provide a good lighting on the working planes; in order to avoid the glaring and at the same

Figure 5. A rendering of the lighting project.

The second plant develops on the whole slanted surface aimed as a sun screen, the most of the lighting is provided by the side clear glassy fagade. The overheating and the glaring diseases are so reduced by using a large cell density for the photovoltaic fagade and the self shadowing of the remaining old building walls.

By using the above formula and the data shown in table 3, a daylight factor of 3.7 is obtained. This is a very good value for the use of the room as office

time to allow a good vision of the outside environment, the modules are designed on the purpose, as it can be possible to see in figure 5.

Af

Ti

Є

¥

P

cm2

PV modules

68949

30

0.5

1

windows

25380

90

0.5

1

walls

934200

0.5

ceiling

127700

0.7

floor

127700

0.3

average

1189600

0.5

DF

3.67

%

Table 3. Parameters used for the calculation of the daylight factor.

The PV modules beyond shadowing the sun they also reduce the overheating due to excess of insolation at summer. To eliminate the self shadowing of the cells the use of frames with Vasistas mechanisms for opening are considered.

CONCLUSIONS

The sun light can be efficiently used fro daylighting with many advantages; a saving on the energy bill can be gained and the increasing of the comfort from optical, thermal points of views. The diffusion of the building integrated photovoltaics in form of fagade and sun screen and the new concept for projecting the PV module according its multifunction aspect making available semitransparent or translucent module created a good potential for that application. In that case some optical characterization could prove to be important and that work presented a methodology ENEA undertook in order to investigate the optical

transmittance. That value combined with the density of the cells are parameters that are

needed for the daylight factor determination to be used in the lighting project

The paper showed as an example that replacing a traditional glass fagade with Photovoltaic

resulted on the reduction of the day light factor so giving an improvement for the comfort of

the room. By using the density of the cells the glaring effect can largely reduced if not

avoided.

Methods and Approach

The investigations are based on a combination of daylighting simulations using Radiance [RAD] with methods used for the design of experiments (DOE) [Sch97]. The simulation allows for reproducible sky conditions.

The goal is to find the qualitative and quantitative influence of elementary architectural, i. e. structural, measures on the daylight quality in interior spaces.

The DOE methodology allows multi-dimensional factor variation at minimum experimental expense. The DOE plans containing all necessary experiments show two essential charac­teristics:

• All factors are varied in discrete steps, i. e. not continuously, with the number of steps being as small as possible. Thus in the simplest case, these are two steps defining the lower and upper border of the experimental space.

• All variables are linearly transformed so that the bounds of definition range from -1 to +1. This leads to DOE matrices with orthogonal columns, DOE plans of general validity (independent of the natural variable dimensions), and to the possibility of a direct quan­titative analysis of effects.

Base case is a room lit by one un-obstructed vertical window. Two more investigations show two windows each, in two facades adjacent to and facing each other, respectively. Two variations of an obstructed single window case and two roof lighting designs complete the research work. A few restrictions apply:

• In cases with one window only, its horizontal position is central. The results do there­fore not apply for strong asymmetric placements of the window. In cases with two win­dows, the symmetry restriction holds for one of them.

• All numbers are based on a CIE overcast sky with a sun elevation of 60° above the horizon.

• All daylight openings are rectangular.

• All room geometries are rectangular except for the roof geometries in the toplit cases.

• The interior optical description is limited to the uniform average diffuse reflection coeffi­cients of floor, walls and ceiling.

Three criteria have been looked at in [Sic03]: the average daylight factor D, the daylight factor in a room depth of 4 m, D4, and the daylight factor regularity, G, which is the ratio of minimum to mean daylight factor. The most useful criterion is D. It serves as a measure for the total amount of daylight inside under overcast conditions. The regression analysis re­sults for this criterion are presented here.

Thermal Properties

In order to calculate the total solar energy transmittance (g-value) [5], the secondary heat flux Is must be calculated. The thermal simulation program HEAT2 was used to estimate the heat flow into the room caused by the absorption on the back of the reflective layer and in the glass itself. It was assumed that the glass bars were positioned 1 mm from the outer glass pane. The bars themselves had a diameter of 10 mm, and the distance from the bars to the inner glass pane was 12 mm.

g

With the secondary heat flux Isec heat, the direct and diffuse intensities (Isec dir, Isec diff) and the incident global radiation Ig given, it is possible to compute the g-value:

Fig. 7 g-value of the system (в = 90°) for days with Idir = 0 (cloudy) and Idjr > 300 W/m2

(sunny).

04

0.00

1.00

0.90

0.80

0.70

0.60

Cl)

0.50

O)

0.40

0.30

0.20

0.10

0 730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760

Time [h]

Fig. 8 g-value of the tilted system (в = 30°) for days with Ib = 0 (cloudy) and Ib > 300

W/m2 (sunny).

The g-value was also estimated for the tilted system, with a slope of 30° (Fig. 8). One can see that the g-value for cloudy weather increases slightly while the one for sunny weather decreases. The latter comes from the fact that, especially in summer when radiation is strongest, we don’t get multiple reflections and so the absorptance on the darkened side remains small. This effect will be more pronounced for the secondary heat flow in this case.

As mentioned before (see Fig.4) a considerable part of the direct radiation is absorbed on the blackened side of the reflective layer. This will lead to a secondary heat flux into the room. In order to get a feeling for how much of the g-value is radiation that can be used for illumination and how much is heat radiation depending on the absorbed power, the amount of heat flowing into the room was computed with HEAT2. Figure 9 shows that even for the в = 0 case in summer the maximum heat flux into the room does not exceed 80 W/m2. For the tilted case (в = 30°) the secondary heat flow is even smaller (Fig.10).

40.0

30.0

20.0

10.0

0.0

0 730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760

Time [h]

Fig. 10 Secondary heat flow into the room arising from the absorption on the blackened
side of the reflective layer, tilted case (в = 30°).

0 —

0

730 1460 2190 2920 3650 4380 5110 5840 6570 7300 8030 8760

Time [h]

Fig. 11 Contribution of the secondary heat flux (black) and the diffuse radiation (grey) to

the g-value, vertical case.

The percentile contribution of the secondary heat flux and the visible diffuse radiation to the g-value is plotted in Figure 10 for the vertical case. As one can see, the secondary heat flux Isec heat contributes only about 30 % to the total g-value, whereas the diffuse radiation transmittance makes up the greater part and should be sufficient to illuminate the room. For the tilted case Isec heat will contribute about 40% in winter and 15% in summer.

Conclusions

As has been shown, the system efficiently shuts out the direct radiation. This reduces glare. Even though the main part of the direct radiation is absorbed by the blackened side of the reflective layer, overheating should not be a problem, if the glass bars are positioned close to the outside glass pane, as the heat will be conducted that way.

Regardless of the system’s properties for direct radiation, the transmission for the diffuse radiation will be around 60% throughout the year, guaranteeing a high illumination level in the room.

Improvement could be made using photochromic layers, which would darken only on the focusing line). This would make a mechanical adjustment superfluous.

[1]

Improved case

The improved case of the SIEEB resulted from the advanced technological solutions and control strategies such as sun shading, radiant ceilings, displacement ventilation and maximizing natural and minimizing artificial lighting. In the DOE simulations, these strategies are simulated as described below:

Sun shading: the values of direct and diffuse solar radiation are reduced to 50% during summer and 80% during winter.

Radiant ceilings: the set points for thermal comfort conditions corresponding to dry bulb temperature is increased by 1°C for summer and is decreased by 2°C for winter.

Displacement ventilation: reducing the values of fresh air volume by 20%.

Lighting: high efficient lamps and control sensors (dimming)

The above hypotheses considered for simulating the advanced technological solutions and control strategies are quite reasonable and are expected to calculate the values of energy savings reasonably well.

Energy Demand — Improved Case

J FMAMJ J ASOND

Month

Figure 5 shows the monthly energy demand for cooling, heating and lighting & equipments corresponding to improved case of SIEEB preliminary design.

Figure 5. SIEEB (Improved case) — Monthly Energy Demand

The potential load reductions based on advanced technological solutions and control strategies are shown in figure 6. It has been observed that for improved case the annual energy load reductions for cooling, heating and lighting & equipments can be achieved up to 30%, 23% and 20% respectively.

2. Conclusions

A methodology for the energy efficient design of the Sino-Italy Environment & Energy Building (SIeEb) is presented. It has been shown that using various advanced technological solutions and control strategies in the SIEEB, an appreciable amount of energy savings can be achieved. Since the results, presented here, are in comparison with a reference case in which the building envelope is already optimised, therefore, compared to a baseline building, constructed as per the current practices in China, the

Energy Load Reduction

□ Reference Case □ Improved case

Figure 6. SIEEB (Improved case) — Energy Load reduction

SIEEB is expected to contribute much higher amount of energy savings. SIEEB is an ecological and energy efficient pilot building and represents a model for a new generation of sustainable buildings. SIEEB can also be seen as an ideal case for assessing the benchmark for implementing the clean development mechanism (CDM), aimed to reduce CO2 emissions according to the accounting procedures defined within Kyoto protocols (IPCC, 2000).

References

J. Chang, Dennis Y. C. Leung, C. Z. Wu, Z. H. Yuan (2003), ‘A review on the energy production, consumption, and prospect of renewable energy in China’, Renewable and Sustainable Energy Reviews, 7, 453-468.

F. Butera, S. Ferrari, N. Aste, P. Caputo, P. Oliaro, U. Beneventano and R. S. Adhikari (2003), ‘Ecological design procedures for Sino-Italian Environment and Energy Building : Results of Ist Phase on the Shape Analysis’, Proc. PLEA-2003 Conference, Santiago, Chile, November 2003.

DOE-2 Manuals (Version 2.1) (1980), US National Technical Information Service, Department of Commerce, Springfield, Virginia, USA.

J. Chen (2003) Sustainable Buildings: the Chinese Perspective, Challenges and Opportunities, Presented at the COP-9 Conference, December 1-12, 2003, Milan, Italy.

IPCC(2000), Website www. ipcc. ch.

CRYOGENIC OBJECT SUPERINSULATION CHARACTERISTIC

After the superinsulation invention by P. Petersen, quite a little time has passed — only several decades. However the concept of superinsulation operation mechanism has suffered

multiple variations. In the course of time these models have allowed to develop a modern superinsulation.

P. Petersen placed screens made of aluminium foil in a vacuum volume and separated them by means of glass-fibre mats. Instead of foil, a polymer film with thin aluminium layers being applied on its both sides is most widely used now.

A number of competing concepts exists as to the heat transfer mechanism in superinsulation. These concepts were sufficiently true in order to develop a sufficiently effective superinsulation. However, in the process of operation of big cryogenic objects, researchers have noted that our ideas on thermal processes in superinsulation are not correspond to reality.

Using the latest views on superinsulation, one can make the following definition.

Screen-vacuum heat insulation (superinsulation) is a system of parallel or concentric (coaxial) gas-permeable metal films applied on a substrate being separated from other by a porous padding manufactured from a material with a high heat resistance coefficient providing a small degree of heat radiation absorption and a small degree of accommodation of the inter-screen gas molecule energy at a high and stable adsorption ability of the metal films.

At the present time, a polyethyleneterephthalate film with the thickness of 12-15 p. m with thin layers of aluminium of 0.5 p. m thick being applied thereon on both sides are widely used as screens [10, 11]. A low heat conductivity of the film and a small thickness of the aluminium layer reduce the heat transfer along the layers and increase the superinsulation effectiveness in industrial products. For the insulating pad thin-fibre (with the fibre thickness up to one micron) glass materials with low gas release are used. As the distance between the screens is sufficiently large (the packing density normally lies within 10-50 screens/cm), the screen-vacuum insulation operates most effectively at practically the same low pressure values as the pure vacuum insulation, i. e. at the pressure values below 10-2 Pa. However the effectiveness of such insulation is far higher than the vacuum and powder-vacuum insulation. The present-day industrial superinsulation provides a heat flow at the level of 0.3-0.5 W/m2. Such heat inflow values are realised at the screen number of 45-75, i. e. at the thickness values less than 0.1 m and a small insulation layer mass [11]. The best superinsulation samples within the temperature range of 10 — 350K are characterised by the effective heat conductivity coefficient equal to (2-3)*10-5 W/(m*K), i. e. significantly less that with other heat insulation types. This parameter provides for the preferable superinsulation application for the protection against heat inflows of devices operating at cryogenic temperatures. [11].

A peculiarity of superinsulation is the non-additivity of thermal resistance in respect to the number of screens and the fact that the thermal resistance of insulation practically cease increasing when a certain number of layers has been reached [12].

Design Principles

The Renewable Energy Centre is the first commercially developed building to be carbon neutral and entirely self-sufficient in energy. Indeed the various integrated renewable energy systems will, over any year, generate a surplus. This will be fed into the electricity grid for the use of the community.

The project brief was the conversion and extension of the former Ova ltine Egg Farm to provide 2,665 m2 of headquarters office accommodation for RES. This was to be carried out using, so far as economically practical, a range of renewable energy measures and employing ‘best practice’ sustainable strategies. RES was assisted in this objective by the contribution from the EC Framework 5 Programme. This funding was conditional on the adoption of a radically innovative approach to resolving sustainable issues and the involvement of a pan-European design and development team. On the basis of this innovative content, RES requested that additional facilities for visitors and parties who might wish to see and learn about the building and its energy systems.

Accordingly, the design principles upon which the development is based were to:

• Provide a fully operational head office which meets the commercial needs and conditions of the property market

• Provide exhibition, conference and facilities for the use of RES and visitors to the building

• Deliver a building that minimises energy consumption and the use of scarce resources and that contributes positively to local economic and community needs

• Deliver a building whose energy consumption is provided entirely from on-site renewable energy sources

• Integrate seamlessly the social, technical and aesthetic aspects of the project.