Category Archives: Sonar-Collecttors

The domestic water heating

Up to this point, only room heating demand has been considered without taking into consideration the domestic hot water demand. The DHW demand is constant during the whole year, and in this case two persons would need 106 kWh/month that means 1273 kWh/year, almost half value of the room heating needed.

If this thermal energy load is added to the previous total heating demand, and is covered by the pellets/wood boiler, 147 kg of pellets is needed to cover the 100% demand, (27 Euro for the whole season), a small quantity compared to the Italian energy demand standards. This solution has two advantages: the usable solar energy is greater (since will be less solar energy wasted) and the pellets/wood boiler will be used for a longer time, decreasing the pay back time of the heating system.

Fig. 12 — Photovoltaic system scheme

4.5 The electricity demand

A grid connected photovoltaic system of 2,1 kWp provides the whole electricity demand (Figure 12).

21 PV panels of 100 Wp each organised in three strings are positioned in the upper surface on the south solar wall.

Building envelope

orientation [°devation from S]

Fig. 9: weighted U-value walls Fig. 10: weighted U-value windows

As could be expected, the majority of houses are extremely well insulated and have high quality windows.

The graph Fig. 9 includes U-values for walls from 0.06 — 0.25 W/m2K. The impressively low U-value of 0.06 W/m2K comes from a very new construction type "space frame”. The "space house” walls are 60 cm think and consist of a wooden space truss filled with cellulose (Fig. 11). The high value of 0.25 W/m2K comes from a project which was a renovation of a historic building and the insulation thickness was limited. The U-value of our projects averages 0.14 W/m2K. This is even below the target value of 0.15 W/m2K the Passivhaus Standard recommends not to exceed.

Also, the weighted U-value of the windows (Fig. 10) at 0.81 W/m2K corresponds very well to the passivhaus standard recommendation of 0.8 W/m2K. The very low U-value of the windows in the space frame project of 0.31 W/m2K was easily possible because of the thick wall construction, which allowed a double window construction with very good glass and frames (Fig. 11)

The window area to facade area lies between 15 and 40 percent, with the majority of houses having approximately a 25% window to wall ratio. The exceptions are the projects with special facade constructions, i. e. “Lucido” or transparent insulation (Fig. 12).

Fig. 12: Window to facade ratio

Fig. 11: Space house, Liedertswil (CH): construction of the whole house, wall construction and a double window (Architect: David Muspach, Basel)

Air tightness, on the other hand is very important to high performance, with the majority of projects having a measured tightness between 0.3 and 0.9 [1/h] at 50 Pa over and under pressure. The average lies at 0.6 [1/h], which fulfils exactly the passivhaus and Minergie-P standard target. The exceptions are again projects with special facades and understandably, the retrofitted existing building project. For four of the twenty projects no air tightness data is available(F/g. 13).

EXPERIMENTAL PROCEDURE

2.1. — Direct coating

In the hole of the samples equiatomic amounts of Ni and Al powder are introduced and is pressed uniaxially. Several amounts are added and press several times up to introduce ca. 2 g.

When the sample is in position on the focal point the cover of the Fresnel lens is put out and the NiAl begin to be heated. When the ignition temperature is achieved the reaction starts and in 0,2 sec. is completed. A wave is visible starting in the center of the sample, the heatest spot, where the melt of NiAl happens as a consequence of the high evolution of heat. going to the outside and back. A second wave returns because the outside of the samples is the coolest and then the solidification of the melted NiAl happens in the opposite sense.

The melted NiAl produces a coating on the steel when the amount of NiAl is higher than 0,6 g. The reason, as explained in a previous paper, is that when the amount of reactive powder increases temperature increases and there is more time to produce de mutual diffusion of Ni and Fe to have good adherence [8]

To increase this adherence some other tests were made. They consist in the introduction of a layer of Ni powder under the mixture of AlNi powder. When the SHS reaction was performed, the adherence was better except in the sides because in the vertical walls there were not the intermediate layer of Ni [9] The coating consists in a layer of Ni, reach in Fe in the lower part and poor in Ni in the upper part because of the diffusion.

2.2. — Saving in energy

The main advantage of this combination of SCE and SHS is that of no fuel consumption in the preparation of a coating of a intermetallic whose melting point is over 1600 K. The only
energy consumption in the whole process is that of electroplating and that of equipment following the sun.

Another advantage of this kind of combined processes is that the time of reaction is very small, ca.0,2 sec; that means

Conclusion

This paper demonstrate the possibility to produce coatings with a high temperature performance on steel obtained without any consumption of energy except free solar energy and exothermic chemical energy that is also non polluting energy.

Materials obtained are high temperature materials whose fabrication obliges to a high energetic consumption according traditional production routes.

This presentation try to encourage the imagination of scientific and engineers to identify and develop all possibilities we have at hand to follow in industrial development with a strong reduction in non renewable polluting energetic materials without CO2 production.

Additionally this equipment is presented as the most suitable to perform research a pilot research working with materials. Due to its lower total cost it can be buy by any department in materials of any university or research centre as an ordinary research tool but mainly as a way to show students and post graduate and industrials the possibilities of CSE, combined or not with SHS, in the near future.

It is only a matter of imagination and, certainly, a matter of complementary work to be done mainly in the field of control to obtain a automatic equipment.

Literature

[1] I Garcia, G. P. Rodriguez, J. J. Damborenea, A. J. Vazquez, , (2002), ”CSEFL (concentrated Solar Energy with Fresnel Lenses): an Ecological Option for Surface Modification of Materials”. International Forum on Renewable Energies FIER’2002 Tetouan, Maroc, pp. 228-234

[2] I. Garcia, J. Sanchez Olias and. A. J. Vazquez, (1999) "A new method for materials synthesis: Solar energy concentrated by Fresnel lens", Journal de Physique IV, France 9, 435-440

[3] I. Garcia, J. Sanchez-Olias, J. de Damborenea y A. J. Vazquez, (1998), "Sintesis de nitruro de titanio mediante laser y energia solar concentrada", Rev. Metal. Madrid 34,2, 109-113.

[4] Quncheng Fan, Huifen Chai and Zhihao Jin, (2001), “Dissolution-precipitation mechanism of self-propagating high-temperature synthesis of mononickel aluminide”, In Intermetallics, 9 pp. 609-619

[5] J. J. Moore, H. J. Feng (1995) “Combustion synthesis of advanced materials: Part I. reaction parameters”, Progress in Materials Science 39 (4-5), pp. 243-273.

[6] J. J. Moore, H. J. Feng, (1995) “Combustion synthesis of advanced materials: Part II. Classification, applications and modelling”, Progress in Materials Science 39 (4-5) pp. 275-316.

[7] J. Sanchez Olias, I. Garcia, A. J. Vazquez, (1999), "Synthesis of TiN with solar energy concentrated by a Fresnel lens”. Materials Letters 38 379-385

[8] C. Sierra and Vazquez A. J., (2004)“NiAl coatings on carbon steel by SHS assisted with Concentrated Solar Energy: mass influence on adherence”, International Conference on the Physics, Chemistry and Engineering of Solar Cells (SCELL-2004),in press

[9] C. Sierra and Vazquez, A. J. (2004), “NiAl coatings on carbon steel by SHS assisted with concentrated Solar Energy. Influence of powder”, in press

The ECOS performance assessment: computer simulations

Mathematical modelling activities which focused on the creation of a simplified algorithm capable to represent the heat and mass transfer processes within the ECOS have been carried out [3]. The dynamic model, describes the transient heat and mass transfer processes within the air conditioner. The algorithm was implemented aiming to create a software tool capable to carry out a large number of simulations in an acceptable time. It allows the assessment of the energetic performance at different supply air conditions (i. e., temperature and humidity) and thereby to simulate a whole process consisting of the three phases, namely adsorptive air-conditioning, regeneration and pre-cooling.

It was assumed that two heat exchangers are periodically operated. While one heat exchanger dehumidifies and cools the outside air, the other one is regenerated with hot air and then pre-cooled with outside air. The duration of the regeneration and pre-cooling phases have been assumed 80% and 20% of the adsorptive phase length (from here on referred as duration of the cycle), respectively. Moreover it has been assumed that a heat recovery component operates between exhaust air and outside air during the regeneration, resulting in a pre-heating of the regeneration air stream. The heat recovery efficiency, considered constant, was set to 0.8. The simulation’s aim was to assess the process performance in hot and humid climates, therefore the following ambient air conditions were assumed: temperature 35°C, humidity ratio 20 g/kg. The return air conditions used (typical for an office building) are: air temperature 26°C and relative humidity 50%.

Using the above mentioned dynamic model a set of simulation run was performed, with a time-step of 0.01 sec. A preconditioning run (i. e., iterative simulation of an initial time period until temperatures and/or fluxes stabilize at initial values) of all the three phases was carried out before each actual calculation.

The assessment of the ECOS performance has been accomplished in terms of: supply air temperature, supply air humidity ratio and coefficient of performance (COP). The latter is calculated as follows:

Cop = Qs"i’ p|y

Qreg

Qsuppiy denotes the air-conditioning work and it is assessed as:

t=t*

Qs"pply ^msupply ’ (hamb hs"pply) [kJ]

t=0

where hamb and hsupply are the specific air enthalpy at ambient and supply air conditions during each time step t, respectively. The limits for the integration range from zero (i. e., beginning of the cycle) to t* (i. e., cycle duration). The supply air mass flow rate is expressed as m supply.

Qreg, is the amount of energy used for the sorptive material regeneration during a cycle, and it is expressed as follows:

t=0.8-t*

Qreg “ Jmreg ’ (hrec _ hreg) [kJ]

t=0

where hrec is the specific air enthalpy at the exit of the heat recovery device operated between the ambient and the exhaust air streams. hreg is assessed using the same humidity ratio of ambient air and the regeneration temperature set for the given simulation. Once structural heat exchanger characteristics (i. e., plates material and dimensions, flow characteristics, sorptive material and its coupling with the plates, see table 1) have been fixed, the system performance is a function of the way the system is operated. In particular the cycle duration
(interval of the periodic operation) and the regeneration temperature are strongly influencing the ECOS energetic behaviour. In order to analyse the system performance a parametric study through computer simulations has been carried out.

The study has been worked out varying the regeneration temperature in a range of temperatures consistent with the aim of using solar energy as heat source (i. e., Treg 60-95°C). The cycle’s duration (t*) ranges between 150 and 600 seconds. A summary of the above mentioned data is given in table 2. In the ECOS process adsorption phase the values of the supply air temperature and humidity ratio vary within the same cycle. The variation is caused by the non-continuity of the process since the two variables change according to the rate of water vapour load of the sorbent material. Therefore, for each cycle an average value of the supply air temperature and humidity ratio has been calculated and used during the performance assessment process.

Solar Cooling Light calculation tool

Within the SACE project, an easy-to-handle computer tool for pre-feasibility studies was created which provides a draft assessment of a reasonable value of collector area and storage size for a given building and climate and for a given solar collector type. Pre­condition is the availability of a defined formatted input file, containing both, meteorological data and load data. A number of files has already been prepared for different European locations and load structures and is delivered with the program. Further configuration of the desired system is done in the main input screen of the tool, i. e. the efficiency coefficients specifying the solar collector, the driving temperatures of the thermal cooling equipment and a global thermal COP have to be specified. More distinctions between the different thermal cooling processes are not made.

The program calculates on base of an hour-to-hour comparison of delivered heat from the solar system and required heat for cooling and for building heating annual values of the solar fractions for heating and cooling and net collector efficiencies. Automatically, a parametric study for different specific collector areas (expressed as m2 of collector area per m2 of conditioned room area) and for different specific hot water storage sizes (expressed as hours of storing the peak cooling load) is carried out. Figure 3 shows an example of the output of such a calculation. The SolarCoolingLight tool is available for free and may be downloaded from the SACE webpage.

Technology for building integration

The technology for building integration has several aspects. One of the most important items is the roof integration.

The collector is part of the watertight barrier of the building and care must be taken especially with fixing the collector between the roof tiles. A safer way is the construction with the collector on top of the roof tiles, but this is aesthetically a poorer solution and does not save on building material.

The pumped systems have a better possibility for building integration than the thermosiphon systems. The storage tank
that has to be above the collector limits the possibilities for building integration. A solution that is practised by Solahart is to have the tank inside the house in the top of the attic and on the bottom of the sloped roof.

Fig. 8 The solar ridge for roof integration [1]

Recently a new invention in building integration has been carried out in the Netherlands. The solar ridge makes it possible to integrate a domestic solar hot water system in the ridge of the roof. In this case a south facing roof is no longer needed. This solution is also very suitable in some older (traditional) buildings.

Daylighting Analysis

In investigating the daylighting of skylights, it can be assumed that they are behaving as luminaries — having a major role in the lighting features of the interior space. To be able to analyze the daylighting characteristics of various skylights and to be able to measure and follow the quality and quantity of transmitted illumination — it is necessary to understand the exact role of the skylight as they are being an important and dominant part of the overall daylighting system. There is not enough precise information on these daylighting systems, and because of this, it is difficult to predict precisely the quality and quantity of illuminance and the light distribution in the interior, and it is difficult to precisely design and accurately dimension the actual daylighting system to meet all the necessary functional, structural and daylighting requirements. The skylights — being the luminaries of the daylighting system — will distribute and modify the external illumination in the interior space:

• the positioning and geometrical characteristics of skylights precisely defines a portion of the exterior space — and practically this portion of the exterior space will be acting as the luminarie of the interior space,

• the different structural parts of the skylights will determine the illumination and light distribution characteristics in the interior space.

The geometry and positioning of the skylights together with their structural characteristics will result the illumination and light distribution in the interior space. The resulted illumination quantities and — distribution can be measured and analyzed in the reference plane of the interior space.

Input — Sky

daylighting system (skylight + lightwell)

Output

E ref. plane = f (interior geometry) Figure 2: Daylighting System I/O

Development of the Thermo Chemical Accumulator (TCA)

Chris Bales, Hogskolan Dalarna, Solar Energy Research Center (SERC) 78188 Borlange, Sweden. e-mail:cba@du. se

Fredrik Setterwall, Fredrik Setterwall Konsult AB, Backvagen 7c, 192 54 Sollentuna, Sweden, e-mail: fredrik. setterwall@comhem. se

Goran Bolin, ClimateWell AB, Instrumentvagen 20, 12653 Stockholm, Sweden. email: goran. bolin@climatewell. com

The Thermo Chemical Accumulator (TCA) is a chemical heat pump driven by low temperature heat that has integral heat storage with high energy density. This makes the device very suitable for solar cooling. The working pair consists of Lithium Chloride and water, and energy is stored and released by desorption and absorption of water under near vacuum conditions. In contrast to most absorption processes and chemical heat pumps, the TCA works with three phases: solid, solution and vapour. This results in near constant operating conditions during charge and discharge, independent of state of charge. This paper describes the fundamental working principles of the TCA as well as a simple steady state model for the TCA. A temperature difference between theoretical and effective temperature in the reactor during absorption and desorption was required in order to get reasonable agreement with measurement data of a prototype TCA machine. For absorption, this value for subcooling was 15°C, which is significantly higher than has been found for low-temperature absorption chillers, indicating potential for improvement. For desorption the value was 7.5°C. The TCA has desorption temperatures of below 100°C for ambient temperatures below 40°C, which is relatively low. The temperature lift depends on the cooling rate supplied and varies from 15°C for the design cooling rate of 5 kW per TCA unit and 30°C inlet temperature to the reactor, to 20°C for a cooling rate of 2.5 kW. The energy density for storage was 180 kWh/m3 for the tested prototype.

Background

In many countries there is a continual increase in the demand for comfort cooling of buildings. This is reflected in the increase in the number of room air conditioners sold in southern Europe, as exemplified in Greece where the number of units sold more than doubled to 200000 units between 1990 and 2000 (Papadopoulos et al., 2003). Most of these were small units, with over 70% having a cooling capacity of less than 3.5 kW. These are predominantly electrically driven compressor heat pumps, resulting in peak electricity demand during the hottest periods and amplifying the heat island effect in large towns where the local ambient temperature is much higher than in surrounding areas. These units also use refrigerants that are either damaging to the ozone layer or are powerful greenhouse gases or both. Due to recent EU regulations regarding the phasing out of ozone depleting substances (2000), the cost of owning units with such substances will increase.

There are thus several reasons to develop alternatives to the vapour compression heat pump for providing comfort cooling: reduction of the peak electricity load during hot periods; replacement of refrigerants that are ozone depleting and/or strong greenhouse gases; and reduction of the heat island effects in large towns. In order to reduce the electricity load, thermally driven cooling processes have been developed and some have
been applied commercially. The commercial units use either absorption or adsorption cycles.

Fig.5 After freeze in the temperature inside the vaccine compartment is kept within the design range 0-8 oC. Tamb = 20 oC . Conclusion and perspectives

The SolarChill has been developed in a fruitful co-operation between leading appliance manufacturers and international organisations, setting the desired properties of the product. It has been proven that it is fully possible to run a solar refrigerator without battery or start capacitor, both elements that would decrease the reliability. This opens up for a more general acceptance and dissemination of solar refrigeration, not only in the health sector, but also for commercial or domestic use. Some obvious future applications for this product could be milk chilling, vending booths for food and beverages, recreational purposes or as a grid independent household refrigerator.

Even after an expected WHO approval, there is still basis for optimisation, such as:

— minimisation of the module area for specific climatic regions

— optimisation of the control strategy in order to minimize the needed PV-power

— further simplification and cost reduction of the construction

The authors sincerely wish to thank the sponsors and project partners for their very constructive assistance and participation in this project.

References

PV-POWERED VACCINE COOLER WITH ICE PACKS AS POWER BACKUP Soren Gundtoft, Danish Technological Institute,2003

SOLCELLEDREVET K0LESKAB UDEN BLYAKKUMULATOR (In Danish)

Project report to Danish Energy Agency, Danish Technological Institute, June 2002

Project flyer:

http://www. uneptie. org/ozonaction/library/tech/solarchill. pdf Compressor data sheet:

http://www. danfoss. com/compressors/pdf/product_news/bd_solar_09-03_cx30e302.pdf

Measurement space envelope

The measurement space envelope for combined BTDF and BRDF measurements, shown on Figure 4(a), consists of a carbon fiber cap strengthened by a structural metallic frame; this frame also supports a static stainless-steel perforated sheet on which a moving synthetic strip can glide. The role of the synthetic strip is to select the elliptic hole through which the incident light’s path will be adequately controlled (according to altitude 61); at the same time, it prevents light from entering the measurement space through any other opening. Its unique aperture is therefore circular, slightly larger than the largest ellipse (i. e. the one associated to normal incidence); the chosen 10° step in altitude ensures that a 15 cm diameter hole never overlaps two consecutive entrances.

(a) Goniophotometer in reflection mode (b) Metal sheet with cut-out ellipses

Figure 4: Structural components of the BT&RDF goniophotometer.

The determination of the actual position and dimensions of the ellipses cut out from the metal sheet required a multiple stages process for an optimal incident light control:

• First, the theoretical geometric properties of the ellipses were determined based on trigonometric considerations, assuming a perfectly parallel beam reaching an elliptic surface of apparent horizontal axis 15 cm and vertical axis 15- cos61.

• Then, the ellipses dimensions were adjusted to the real incident beam, of imperfect collimation and thus producing blurred regions around the uniformly illuminated area, responsible for parasitic reflections. Once the optimal source distance was determined, different elliptic shapes were tried out to compare the achieved sample surface illumi­nation. The most efficient compromise was established between optimal uniformity over the whole sample area and lower parasitic light flux; this was done for each ellipse individually, as more relative blurredness appeared for smaller ellipses. The determined shapes, cut out of cardboard sheets, were tested successfully; they led to only few percent of non-uniformly illuminated sample area while guaranteeing an
average relative blurredness area lower than 10%. It can be noted that these remain­ing parasitic reflections were reduced to a negligible level by adding a ring of highly absorbing material (“velvetine”) around the sample.

• Finally, the positions of the ellipses on the metal sheet had to account for the frame manufacturing imperfections (see above). The metal sheet was thus mounted tem­porarily on the frame, allowing to centre the ellipses thanks to a plumbline course driven by a progressive platform inclination. Their positioning was thereafter verified by pointing a fixed laser on the central axis and tilting the device to get each ellipse’s centre coincident with the laser spot; this test showed that an appropriate accuracy was achieved (± 0.05 cm deviation). Before sending the metal sheet for cutting out, these positions were adjusted to a flat configuration of the sheet (i. e. to its neutral fiber), to avoid slight shifts due to the sheet’s thickness.

The resulting perforated metal sheet is shown on Figure 4(b); its inside surface is covered with “velvetine” (reflection factor lower than 1%).