Category Archives: Sonar-Collecttors

Thickness K K cm w/mq K w/mq K External structural walls external plaster 1,5 Poroton Aktuell with insulation plaster 49 0,22 internal plaster 1,5 e x t Roof tiles 1 e air chamber 5 r waterproof layer 0,5 0,26 n Extrude polystirene insulation 12 a precompressed wood slab 1,5 i Pavement ventilated air chamber 50 solaio pignate e travetti precompressi 15 massetto 5 0,46 f Extrude polystirene insulation 5 a radiant pavement 10 c ceramic 1 e s Windows abete wood frame 6 1,67 low-e glass in layer 2 (solar gain) 0,4 argon gas chamber 1,2 1,1 1,5 glass 0,4 Tab. 1 — Characteristics of the external surfaces . The space heating energy demand

The house has been simulated with the DEROB LTH (Dynamic Energy Response Of Buildings) version 00.04, developed by the Swedish Department of Building Science belonging to the Lund Institute of Technology. Natural ventilation has been considered

2609 kWh/y for heating (29 kWh/m2y)

Fig. 8 — Model developed by DEROB LTH simulation programme

during the whole year.

The results indicate that the volume A will re and 2812 kWh/y for cooling (30 kWh/m2y). This is a lower demand compared to the heating demand of a typical Italian residential building.

4.2 The heating systems (solar and biomass)

Since the energy consumption for heating is low, a great part of it could be covered by a solar heating system. Therefore two solar heating systems have been designed: a water solar system with solar collectors to cover a great part of the heating demand and the DHW needs (Costruzioni Solari s. r.l.[16]) and an air solar system (Solarwall[17]) to preheat the inlet air during the winter sunny days. The

Fig. 9 — Conventional solar system winter behaviour

solar system will heat the house through a radiant pavement system at low temperature. The whole solar system is integrated with a wood stove to cover the complete heating demand during the coldest period.

The water solar system

Fig. 10- Solar water system for space and domestic water heating scheme

Six solar thermal collectors of 1,9 sq meters each and one boiler of 700 litres for the space heating system are located in the south wall as reported in figure 9. The solar system scheme is reported in figure 10. This system should cover from 64% to 100% of the heating demand. In order to increase this percentage, a solar air system has been designed.

Days/ month

Month

Days /month

Average daily radiation in the sloped surface

Average

system

efficiency

(Qa) Daily

average

thermal

energy

available/ sq

m

(Qa) Monthly thermal energy available/ sq m

Monthly

thermal

energy

available

(Ea) monthly

energy

demand

Surplus/integ

ration

% solar fraction

kWh/m2 day

kWh / m2 day

kWh / m2 month

kWh/

month

kWh/

month

kWh/

month

%

31

January

31

3,14

0,40

1,26

39

443

600

— 157

74%

28

February

28

3,42

0,40

1,37

38

437

542

— 105

81%

31

March

31

3,81

0,45

1,72

53

606

600

6

101%

30

April

0

0

0,50

0

0

0

31

May

0

0

0,50

0

0

0

30

June

0

0

0,50

0

0

0

31

July

0

0

0,50

0

0

0

31

August

0

0

0,50

0

0

0

30

September

0

0

0,50

0

0

0

31

October

0

0

0,50

0

0

0

30

November

30

3,04

0,45

1,37

41

467

581

— 113

80%

31

December

31

2,73

0,40

1,09

34

385

600

— 215

64%

365

TOTAL

151

3,23

0,47

1,36

205

2.338

2.923

80%

Table 2 — Heat production and the coverage (in %) of the solar system.

Proven Designs for very Low Energy Housing — Swiss Experience

Daniela Enz and Robert Hastings Architecture, Energy & Environment AEU GmbH Kirchstrasse 1, CH-8304 Wallisellen Tel. +41 -1 883 17 16 /17 daniela. enz@aeu. ch, robert. hastings@aeu. ch

Fig. 1: Collage of Swiss Low Energy buildings

To help architects plan very low energy housing for the first time, reference values can be useful for making critical decisions affecting performance. The authors have analyzed documentation from 20 Swiss projects built to extreme low energy standards, such as the Passivhaus and Minergie-P Standard. The results illustrate how Swiss house-builders have adapted German and Austrian Passivhaus concepts to local housing markets. The number of such high performance houses in Switzerland is still small but interest by home owners and subsequently by architects is growing. An initial sampling of the key values for the envelope and technical solutions are presented here. It is noteworthy, that for some key design parameters, a few projects lie quite outside the average, yet still achieve excellent energy performance by compensating in other parameters. This demonstrates that there is indeed considerable design freedom for engineering high performance housing.

SHS and CSE, a twinned saving energy process

A. J. Vazquez, C. Sierra,

CENIM-CSIC, Av. Gregorio del Amo, 8, 28040-Madrid. Spain (UE)
avazquez@cenim. csic. es

Introduction

One field of big interest inside the frame of Solar Energy applications is that of application to materials. A lot of work was done in different groups joined to biog installations. Odeillo, Denver, Tashkent, etc. In most of the cases the work done was on high temperature ceramic materials. In the Denver Institute of DOE more work was done on metallic materials and also in China an UK, several papers on heat treatment of metallic materials, welding, etc. were performed.

Our group start their work on this topic in the ‘90 with large installations such as those of PSA, Almeria (Spain-UE), later with CNRS, Odeillo (France-UE) and IFS, Tashkent (Uzbekistan).

Several works were made also with a simulator consisting in a 7 kW Xenon lamp and more recently we install a Fresnel lens equipment to get surface modification of Metallic Materials (1-3).

The most recent application consist in the combination of Concentrated Solar Energy with this Fresnel equipment with the Self High Temperature Synthesis to produce coatings of intermetallics. In this paper we will describe the basic Fresnel equipment and the application to the SHS to produce coatings [7-9].

The main aspect of the Fresnel CSE equipment is that of price, size a power density. Price is lower, ca. 15.000 €, size is small and power density, in Madrid installation, is enough good, ca. 250 W sq. cm., i. e. 2500 kW sq. m.

All this characteristics makes this equipment suitable to be used in any research institute or university Department of materials because it falls inside the budget of any research group. The advantages of this equipment are clear:

1. — It is an installation that increases the direct power density ca. 4.000 to 5.000 times

2. — The power density achieved is enough high to produce a lot of metallurgical processes

a. — all typical heat treatments used in metallurgy: quenching, tempering, stress relieving, thermal fatigue, etc.

b. — gas-metal reactions, e. g., nitriding of Ti alloys

c. — melting processes such as coating alloying and cladding, welding, etc.

d. — recently SHS is combined to obtain coatings

e. — any other metallurgical process.

3. — It is strong and very easy to control and can be used as a teaching tool to students in the Materials career and as a research tool as we are doing.

4. — It is the best equipment to transmit to all future professionals working in materials the idea that CSE can be used only for heating sanitary water at home, desalinate brackish or sea water, or to produce electricity, etc. but it can be used in very high temperature applications with small installations.

All the work we did in the past is devoted to transmit this idea: SCE can be used in as many metallurgical operations as we can imagine. We have the tool and it is only a matter of imagination to apply it to real applications. But to start is a need that young students know this real and near possibility to their lives, because most of them don’t know large installations exists.

2. — OBJECTIVE

DEC characteristics and limitations

The standard DEC systems currently used for air-conditioning are mostly based on solid sorbent, and show a process path similar to the one shown in Figure 1. These systems present thermodynamic limits, which affect the process performance. In particular:

— Limited dehumidification efficiency: the dehumidification process is nearly adiabatic. The heat of condensation and the heat of bonding released during the sorption process causes an increase in temperature of the air and the sorption material; the latter results in a lower sorption potential.

— Cooling potential not completely exploited: the return stream is saturated before entering the heat exchanger wheel (7) but it leaves with a state far distant from saturation. If it could be humidified during the heat exchange process, the potential uptake of heat and thus the potential cooling would be far higher.

— Low efficient processes sequence: during the standard DEC process the supply air is heated, i. e., during the dehumidification (1)-(2) and then cooled by means of the heat recovery wheel (2)-(3). The sequence is not efficient since one of the aims of the process is the air temperature reduction. Moreover the sequence of the two processes (i. e., dehumidification and heat transfer) sets thermodynamic limits of the cycle and restricts the applicability of the cycle in severe conditions, i. e., conditions at high ambient air temperature and humidity.

Furthermore conventional DEC technology, following the scheme of Figure 2, is not used for small size systems (typically below 3000 m3/h). The main reason is that they result economically not convenient in comparison to other technologies. Furthermore on small capacity plants technical problems such as leakages between return and supply air are more difficult to tackle with success [2].

Guidelines

From basic considerations such as shown in Figure 2, some general remarks may be given for the planning of a solar assisted air conditioning system:

■ If the thermally driven cooling system runs with a comparatively low COP and a fossil fueled heat source backup is foreseen, a high average solar fraction is required in order to achieve significant primary energy savings. This has to be ensured by a proper design of the system, e. g. a large solar collector area, sufficient storage volumes and other measures in order to maximise the use of solar thermal system.

■ A conventional electrically driven compression chiller may be used as backup system alternatively to a heat backup. In this concept, each unit of cold provided by the solar thermally driven chiller reduces the cold to be delivered by the conventional chiller. This

approach leads to primary energy savings even at low values of solar fraction. The solar system then serves mainly to reduce the electrical energy consumption.

■ If a heat backup system using fuels is applied, any replacement of fossil fuels by fuels from renewable souces such as biomass will increase the fossil fuel conversion factor and thus decreases the primary energy consumption of the thermally driven system.

■ A solar thermally autonomous air conditioning system does not require any other cold source and therefore always works at the limit with a solar fraction of 1.0.

■ The utilisation of the solar collector system should be maximised in any case, e. g., by supplying heat also to other loads such as to the building heating system and for hot water production.

More information on guidelines, design approaches and examples for solar assisted air­conditioning is provided in the following projects:

— International Energy Agency (IEA) Solar Heating and Cooling Programme (Task 25, Solar Assisted Air-Conditioning of Buildings) /3/;

— Solar Air Conditioning in Europe (SACE), funded by the EC /4/;

— CLIMASOL, funded by the EC, actually in process and finished 2005 /5/.

What is Building Integration?

The term "building integration” is not well defined. For an architect it is mainly the integration of a solar heating system in the design, for the engineer it is a technology to have the collector as part of a building. For an installer it is a matter of integration with the heating system of the house and the project developer sees building integration more as an aspect of the building process. This can be further explained with some examples. A collector on an existing roof that replaces roofing material, is technically integrated, but not aesthetically. On the other hand an architect may design a collector that is a design feature and not integrated in a building component, but an integral part of the design. In

this paper we define building integration as any form of integration of a solar heating system in the building.

The paper gives an overview of the trends in the world in the field of building integration as part of the architecture of a building, the technology of integration, the integration in the building process and the standards and regulations.

Status of building integration

The thermosiphon systems that are common at lower latitudes are mainly installed on flat roofs and not integrated. The forced-circulation systems are mostly installed on top of the existing roofing. The trend is to replace the roofing material so that the collector is in the

roof and not on top of the roof.

Fig. 1: example of not integrated thermosiphon systems

Fig. 2: example of roof integrated solar heating system (Austria)

For new buildings with a solar heating system, the collector is in general in some way integrated, but for existing buildings the solar heating system is mostly not integrated.

Discussion and conclusion

A proper model for the regulating strategy of the system is needed to predict the distribution of gains and losses via the Solar Window. The complexity and interrelations between the different functions is a challenge for the modelling, which needs to integrate the spatial surrounding. A detailed model could be of much use for a regulation of an automated system for best performance and comfort.

The level of automation for the system is object for further studies. A range of products with different standard, from fully manual to fully automatic, is a likely development. It is however of importance that the control-function can be overridden manually at all times due to direct response from the user.

Performance of the system has been analysed separately for passive gains, active thermal gains and PV electricity yield. According to the proposed regulating schedule, passive gains are estimated to 210 kWh/m2 annually. However, it is not examined how much of this is usable. The performance of the fully concentrated PV/T absorber is estimated to 79 kWh/m2 of electricity, and at least 155 kWh/m2 of heat for domestic hot water. Following the proposed regulating schedule, these figures might be reduced. For a more accurate and integrated analysis, long-term outside measurements will be made for the full window prototype with PV/T absorbers.

Cost estimations are dependent on where the system border is drawn, since the system also is the building envelope. For comparison with conventional solar energy systems, it might be fair to withdraw the window and sunshade cost if the same is done for the building material the conventional collector replaces. Production cost for the Solar Window excluding the glazing is estimated to approximately €250/m2, but more thorough calculations need to be made.

Acknowledgements

This work was supported by the Swedish Energy Agency and Formas, the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning.

Automation of Central Receiver Systems Plants

Figure 1. Detail of the operation of the heliostat field and CRS at CIEMAT-PSA

From the point of view of automatic control, a Central Receiver System (CRS) plant may be decomposed, almost in a first approximation, in two subsystems. The first one is the Heliostat Field (HF) and the second one is the Receiver and Power System (RPS), sited at the top of the tower. Figure 1 shows both components interacting. The HF reflects incoming solar radiation in predefined aimpoints. Following this natural decomposition the control system of the CRS is divided into two functional blocks: the HF Control System (HFCS) and the RPS Control System (RPSCS).

each heliostat of the HF in the desired

The basic objective of the HFCS is to position coordinates all the time, depending on the PS demands. The global objective of the HFCS is the generation of a uniform time-spatial distribution of the temperature onto the volumetric receiver (in the case of the PSA CRS), by controlling the timed insertion of group of heliostats associated to predefined aimpoints in the receiver, by modifying the aimpoints coordinates and by changing heliostats from one group to another during operation. This is accomplished by applying an aimpoint strategy over the HFCS [1].

From the control viewpoint, due to the requirements of the operation, the HFCS can be considered a hard real time system and thus, it requires a real time support system [2] to guarantee the adequate positioning of the heliostats at due time. Moreover, the HFCS must permit easy integration with the RPSCS, without losing the real time capabilities. The work that is being developed at present in PSA-CIEMAT is oriented towards the development of a real time distributed control system for the HFCS. The RT-CORBA [3] technology helps to integrate heterogeneous computing platforms and has been selected to implement the communications between the different data acquisition and control sytems. In this case, the RPSCS has been implemented in LabView over Windows XP OS. This control system is described in [4] in more detail. The HFCS is being developed in C++ language using the ISO POSIX C 1003.1c API interface, over LynxOS operating system. The real time logical interface to the PSCS is being implemented using The Ace ORB (TAO) RT-CORBA implementation [5-8]. The TAO CORBA distribution is widely used for industrial and scientific purposes (http://www. cs. wustl. edu/ schmidt/TAO. html).

Preliminary tests have been performed at CIEMAT-PSA using a Cluster Beowulf platform based in a switched 100 Mb/s Ethernet network and low computing resources nodes. The experiments have successfully demonstrated the low overhead and latency that TAO introduces in two-way inter-objects calls. Depending of the test performed the total cost in time of the overhead introduced by CORBA layers (at client and server objects) and network delays are lower than 5 ms in the worst cases [9].

Using RT-CORBA in the HFCS software design, a real time logical interface to the physical field (heliostats) is provided to the rest of computers and systems connected to the network domain. These computers may interact with this logical interface with independence of the operating system and programming language, which augments and promotes the heterogeneity and overcomes the constraints imposed by proprietary technologies. An example of interaction promoted by RT-CORBA is the periodical request of coordinates from each heliostat of the HF from the LabView application in the RPSCS (figure 2).

Ethernet Network RT-CORBA

Power Stage Control System He liostat Fie 1 d C otitrol System

LabView Interface IEEE POSIX 1003 Лс

Soft Rea] Time Operating System Hard Real Time Operating System

Figure 2. Distributed control system based on RT-CORBA middleware

The main objective of the RPSCS is to regulate the pressure and temperature of the steam generated with the heat collected in the solar receiver. Figure 3 shows the components of the RPS at the CESA facility at CIEMAT-PSA. Briefly it is composed of:

• Solar receiver.

• Storage tank.

• Air-water/steam heat exchanger (HEX).

• Process load (in the figure formed by a steam turbine and a condenser).

• Actuation components: K1 and K2: valves; G1 and G2: blowers; B1: water pump; V1: steam valve.

Figure 3. Diagram of the power system of the CESA facility at CIEMAT-PSA (courtesy of J. D. Alvarez)

The system operates as follows: the concentrated solar radiation heats of the air flowing through the volumetric receiver. The air temperature gradient through the receiver can be controlled via the actuation over K1 and G1, so the output temperature of the receiver is regulated controlling the air mass flow rate m1 over the K1-G1-Receiver branch. This is the first control loop. The control algorithm implemented at present is an classical PID with anti-windup controller.

In a similar way, the air mass flow rate entering the HEX is controlled by acting on K2 and G2.

The second control loop must control the energy flux at the HEX inlet, by extracting/impelling air from/to the storage tank depending among other variables on the solar radiation conditions, receiver state, etc. This control loop is also based in a classical PID with anti­windup controller.

The RPSCS is under development at present. One of the steps that is being carried out is the development of a reliable dynamic model of the process. This model is being implemented using the object oriented modelling language for physical systems Modelica [10]. Figure 4 shows the model interface with similar layout than the real system. The object oriented methodology preserves the original topology of the real plant in the model, so any component from the real plant can be described by a model representing it. Finally all the models are connected in the same way the components are connected in the real plant.

From the control viewpoint, the RPSCS signals are:

Thermal Storage Tank

Figure 4: Modelica model of the Power System

Even in the case of good control of the conditions of the inlet energy into the evaporator, variations in the outlet steam conditions in the water-steam circuit are produced. To control the outlet steam temperature/pressure it is necessary to control the pump B1 and valve V1. The control loop of the pump B1 is characterised by having a long delay (the length of the tubes is about 1330 m) and thus the actual control system based on a three state on/off controller is being changed by a Smith Predictor-based control loop [4].

• Mass flow rate through the blowers. This variable could be controlled by manipulating u1, u2, u3 and u4 represented in figure 3. This assumption is nearly true due to the almost ideal mass flow generator characteristic observed in the blower-valve sets in both loops: storage-receiver and storage-HEX mesh.

• Incoming inlet radiation at the solar receiver. This is a perturbation variable and the source of energy for the whole process.

• Mass flow rate through the water pump. The characteristic of this pump is being studied, and it seems to be highly nonlinear.

• Steam valve opening fraction.

The model output signals are all the variables that will be controlled: pressure and temperature at the inlet of the air-water heat exchanger; pressure and temperature at the inlet of the process load (main control objective), and the temperature of the storage tank. These controlled variables are also shown in figure 3.

Laboratory test results

SolarChill

03-03-2004

3-03-2004 06:00

3-03-2004 10:00

3-03-2004 14:00

0

1000

900

800

700

E

600

500

400

T3

ro

300

200

100

—— Current

—— Irrad

3-03-2004 18:00

The vaccine cooler has been tested in climate chamber at DTI. The holdover time for the vaccine cooler was measured to be about four days at 32 °C ambient temperature. For the upright version, the hold-over time is one day less due to the geometry and smaller ice volume. The tests have been used to determine the necessary PV panel size for the selected locations. As the critical parameter is the minimum current for start of the compressor, it was decided to use a panel with a short circuit current of 2.5 times the start current. In this way it is ensured that the compressor will also start at most overcast days, but the economical optimum may be found at a smaller panel size.

Fig.2 Typical current consumption on a good solar day. The many spikes in the early morning represent non-succesful start attempts.

Innovative bidirectional video-goniophotometer combining transmission and reflection measurements

Marilyne Andersen, Christian Roecker, Jean-Louis Scartezzini

Solar Energy and Building Physics Laboratory (LESO-PB), Swiss Federal Institute of Tech­nology (EPFL), CH — 1015 Lausanne, Switzerland

This paper describes the design process and setting up of a novel bidirectional go — niophotometer, relying on digital imaging and allowing the combination of transmis­sion and reflection measurements. As its measurement principle is based on the projection of the emerging light flux on a rotating diffusing screen towards which a calibrated CCD camera is pointed (used as a multiple-points luminance-meter), sev­eral strong constraints appear in reflection mode due to the conflict of incident and emerging light flux: for five out of the six screen positions (unless incidence is nor­mal), the incident beam must penetrate in a way that it is restricted to the sample area only; in addition to this, when the screen obstructs the incoming light flux, a special opening in the latter is required as well to let the beam reach the sample. The practical answer to these constraints, detailed in this paper, proved to be reliable, appropriate and efficient.

Introduction

(a) Arbitrary screen position p (b) Screen position p+1

Figure 1: Detection of transmitted light flux for two consecutive screen positions p and p+1.

To allow the integration of advanced daylighting systems in buildings and benefit from their potential as energy-efficient strategies, a detailed knowledge of their directional optical prop­erties is necessary. These properties are accurately described by the Bidirectional Transmis­sion (or Reflection) Distribution Function, abbreviated BT(or R)DF, that expresses the emerg­ing light flux distribution for a given incident beam direction (Commission Internationale de l’Eclairage, 1977). An original experimental method for their assessment, illustrated in Fig­ure 1 was first developed for transmission measurements (Andersen et al., 2001): the light emerging from the sample is reflected by a diffusing triangular panel towards a CCD camera, which provides a picture of the screen in its entirety. Within six positions of the screen and camera around the sample (each separated by a 60° rotation from the next one), a complete investigation of the transmitted or reflected light is achieved.

This innovative approach brought several major advantages when compared to characteriza­tion techniques requiring a sensor to be moved from one position to the other (Papamichael et al., 1988; Bakker and van Dijk, 1995; Aydinli, 1996; Breitenbach and Rosenfeld, 1998; Apian-Bennewitz and von der Hardt, 1998): a significant reduction of the BT(R)DF data assessment time (a few minutes instead of hours per incident direction) and a continuous information about the transmission (reflection) hemisphere, whose resolution is only limited by the pixellisation of the images.

The camera is used as a multiple-points luminance-meter and calibrated accordingly. A luminance mapping of the projection screen is carried out by capturing images of it at differ­ent integration intervals, thus avoiding over and under-exposure effects, and appropriately combining the latter to extract BT(R)DF data at a pixel level resolution.

Material samples showing large range of luminances can thus be handled without any loss of accuracy, while an appreciable flexibility is allowed in the data processing (Andersen, 2004).

For BRDF measurements (reflection mode), however, additional constraints appear due to the conflict of incident and emerging light flux.

For five out of the six screen positions (unless incidence is normal), the detection princi­ple can be kept identical as in transmission mode (Figure 2(a)), except that light flux must penetrate the measurement space in a way that the beam is restricted to the sample area only. As there is one position (all six for normal incidence) where the screen obstructs the incoming light flux, a special opening in the latter is required to let the beam reach the sam­ple, producing a blind spot at that specific screen position (and only in reflection mode), as illustrated in Figure 2(b).

(a) Unobstructed penetration (b) Screen hole

Figure 2: Detection of reflected light flux.

The design process of the instrument combining BTDF and BRDF measurements is pre­sented in this paper, and the mechanical components specifically developed to answer to these constraints in a practical and efficient way are described.