Category Archives: EuroSun2008-4

Analysed projects

The design projects discussed in this paper were carried out as graduation projects in the years 2006 to 2008. The projects were carried out in the master Integrated Product Design which is focused on the product development from product idea to a production ready product design. The project duration was approximately 6 months. Due to this limitation not all details of the product design could be worked out and the designers set priorities on which details are most important within the project. Also due to the dime limitation, the projects ended when the product designs were in or at the end of the third phase. The projects are discussed in chronological order.

3.1. Pupil Locator

The pupil locator is to be used for children’s ski classes to avoid that pupils get lost or too far away from the group. The pupil locator works with a device worn by the pupils that communicates its location to the instructor’s handheld device. Additionally the pupils can call for help; the instructor sees their location on the handheld device and can easily find them back. The pupil’s device had to be solar powered. The main design challenges for the product were to select a suitable energy efficient technology, to select an appropriate way for the pupils to carry the device and PV cells with them and to incorporate the electronics and PV modules in the product in such a way that comfort of wearing, maintenance and reliability of the system were optimal. The final design is a vest (see figure 4) incorporating the electronics and four PV panels. The panels are attached and electrically connected with metal press-studs. They can be easily replaced when broken, or reused for another vest. Although the PV panels are rigid, the flexibility of the vest is maintained by using four panels instead of one.

image462

Fig. 4. Front and back view of the Pupil Locator vest.

Solar Cooling — A Proven New Technology Christian Holter

S. O.L. I.D Gmbh
PuchstraBe 85, A-8020 Graz

Tel.: ++43/316/292840, Fax ++43/316/292840-28, www. solid. at
c. holter@solid. at

S. O.L. I.D. has more than 10 years experience in the construction and financing (using contracting models) of solar thermal plants from 25m2 to 7000m2. Since 2003, a number of solar cooling projects have also been carried out. Currently 13 projects with a total cooling power of 1,6 MW and collector area of more than 4.000 m2 (2.8 MW) are already operational. For these projects, the solar plant covers most of the cooling demand and in some cases, as conventional back-up systems aren’t always available, the required cooling is 100% supplied by the solar cooling plant.

There are also several more projects with a total cooling power of several MW currently in the detailed planning phase.

Five different cooling machines were used in these projects; three commercial coolers using Lithium Bromide with water and two custom-made coolers using Water-Ammonia absorption technology.

Three different collector types were also used. As well as the standard large area plate collector and a specially developed model of the same, vacuum tube collectors were also applied on an experimental basis to make a direct comparison with the optimised flat plate collectors.

The projects are all commercial plants where functionality is a must (with the exception of the test plant in our own office). By means of service contracts or guarantees, S. O.L. I.D. is able to take over responsibility for the performance of the plants. The systems are remotely monitored and continuously evaluated. The typical contracting model where the plant is financed by the contractor was not possible for these projects as they were mostly in markets where contracting is not yet financially practicable. The daily operation of the various projects has highlighted the importance of accurate designing, optimisation potential of the components, and the need for precise coordination of the complete system.

Server cooling demand

Fig. 4 shows a comparison of the cooling demand of the server room and the building itself. On the left hand side, caused by the constant heat input of the data processing equipment, a relatively constant demand over the year can be observed for the server room. In the present case, the demand is about 20 times higher than the cooling demand of the building. On the left hand side, the remaining cooling demand for the server is shown when the free cooling scheme using ambient air is applied. It can be seen that the demand for cooling the server room can significantly be reduced to almost 1/3.

In addition to the distinctive reduction of the cooling demand, the variation of the demand over the year has changed significantly, too. It can be seen that the cooling demand is mainly remaining during the summer months and is completely removed during winter times. Thus, with this change of the profile, an integration of a solar thermal driven air conditioning system seems to be possible.

Fig. 4: Comparison of cooling demand for the building and the server room. On the left hand side, the total
cooling demand resulting from the heat input of the server is presented, on the right hand side, the remaining
cooling demand for the server when using fresh air cooling is shown.

Development of a multifunctional semi-transparent facade collector

M. Hermann*, T. E. Kuhn, M. Rommel

Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg, Germany
* Corresponding Author, Tel.: +49 7 61 / 45 88 — 54 09, Fax: +49 7 61 / 45 88 — 94 09
michael. hermann@,ise. fraunhofer. de

Abstract

The collector proposed in this paper is a semi-transparent combination of a solar collector and an angular-selective sun-shading device. The absorber of the collector features an array of small openings between the channels which lead to angular-selective properties and to a semi­transparent appearance. The casing of the collector is made from transparent materials. For example, the absorber is mounted between two (or more) glass panes. This means that a person inside the building can look through the collector. The complete window-like collector thus acts as a multifunctional building component which uses solar energy for heat production as well as daylighting and simultaneously provides solar control and glare protection. The multifunctional collector described here is in an early stage of research and development. First investigations concentrated on basic construction possibilities and raytracing simulations. The main tasks within the future work will be the evaluation of different feasible absorber constructions as well as an assessment of the component’s behaviour regarded both as a solar collector and as a transparent, window-like building component. An important focus is on architects’ specifications in order to offer them new perspectives for using solar energy in an attractive and innovative way. The work on the development of this new multifunctional collector will be carried out within a European project together with industry partners.

Keywords: Fa? ade collector, building integration, daylighting, shading

1. Introduction

Solar thermal collectors are state-of-the-art, not only as roof installations, but also integrated into fa? ades, where they can replace a part of the wall and its insulation. In contrast to these opaque constructions, the collector proposed in this paper is a semi-transparent combination of a solar collector and an angular-selective sun-shading device. A part of the solar energy irradiated on the building surface is absorbed in the collector and thus reduces the cooling load of the room behind it during summer months. Additionally, the heat gained from the collector can be used to drive a solar cooling system. An impression of how such semi-transparent fa? ade collectors could look like is given in Fig. 1. The semi-transparent appearance is obtained by a number of small openings between the fluid channels. The openings are built in a way which leads to a three-dimensional structure und thus to a shading behaviour which is dependent on the incidence angle of the sun. They can be produced e. g. by cutting and bending small fins or long lamellae between the fluid channels out of the absorber sheet (Fig. 2). There are also a number of other possibilities to produce the openings. The development

image439

and assessment of angular-selective shading devices without the additional function of a solar absorber is an important field of research at Fraunhofer ISE ([1, 2]), and some of theses devices already exist on the market (Fig. 3). Since the tasks of the collector are both gaining solar energy by heating a fluid and protecting the room from overheating, new challenges arise concerning development as well as technically characterizing this new building component in a sufficient and adequate way with respect to all its physical properties.

Fig. 3: Angular-selective sunshade senn® (clauss markisen Projekt GmbH).
The lateral dimensions of each each profile are 4 mm x 5 mm

Indexes used

2.1.1. Coefficient of reduction Lighting index Cm

The solar factor of a glazing — Seq, is defined as the product of the lighting index Cm, which depends on the quality of the solar protection by the coefficient of transmission of the glazing, S which depends essentially on the type of glazing (see Figure 2). The coefficient Cm allows to determine the performance of the solar protection on the glazing. Cm is determined by the fraction between the total solar energy that comes through the glazing with and without the use of solar shadings. This energy includes the diffuse and direct solar radiation. The more Cm is closed to 0, the more the solar protection is effective.

image468

Figure 2 : Solar radiation through the window and calculation of the solar factor Seq

2.1.2. Daylight autonomy

As it was defined previously, the reference daylight factors used in Europe are not adapted to tropical climates. The use of a parameter such as the daylight autonomy turns out to be more suitable. Indeed, this coefficient quantifies for a typical year, the percentage of time when the required illumination is available in terms of working requirements.

Thanks to combined use of the three softwares previously presented, it is possible to obtain for each study, the daylight autonomy, the illuminance from the point of view of work as well as the lighting index Cn. In terms of outputs, DAYSIM allows to obtain a mapping of the illuminance level in different points as well as the daylight autonomy of the room [9]. The Energy Plus software allows to obtain the solar radiation through the glazing, then allows to determine lighting index [8].

URBAN HEAT ISLAND EFFECT ON HEATING AND. COOLING DEGREE DAYS DISTRIBUTION IN MENDOZA’S. METROPOLITAN AREA. ENVIRONMENTAL COSTS

E. N. Correa1*, C. de Rosa1 and G. lesino2

1 INCIHUSA — LAHV. Instituto Ciencias Humanas Sociales y Ambientales — Laboratorio de Ambiente
Humano y Vivienda. (CONICET — CCT-Mendoza). C. C.131 C. P. 5500 — Mendoza. Argentina

2 INENCO — Instituto de Investigaciones en Energias No Convencionales — U. N.Sa.- CONICET.
Universidad Nacional de Salta. Avda. Bolivia 5150 — CP 4400 — Salta Capital — Argentina.

ecorrea@lab. cricyt. edu. ar

Abstract

This paper presents the geographical distribution of heating and cooling degree-days in Mendoza’s Metropolitan Area (MMA) taking into account the influence of urban heat island’s intensity over the heating and cooling energy requirements in the city and quantifies the green house gases emissions derived from that impact.

The value of HDD and CDD has been calculated from temperature data recorded at 16 fixed weather stations installed within MMA’s, measuring temperature and humidity in the urban canyons during a full yearly cycle. The calculation is performed using the Erbs’s method and the interpolated data for the considered metropolitan area are mapped using GIS software.

The results obtained have been compared with those obtained from the meteorological standards data computations, indicating that there is an under-estimation of CDD for the city’s center of approximately 20% respect to the value obtained from the meteorological station values, and in the case of HDD there is an over-estimation close to 50%.

Keywords: HDD and CDD; Urban Heat Island; Mendoza’s metropolitan area; energy consumption, climate change.

1. Introduction

The influence of weather on energy consumption, particularly on fossil fuel demand, has been widely reported in the past [1]. Although the energy used in the construction is a function of the climate and of the final use or destination of buildings (public offices, scholar, residential; etc), it is also of the city’s architectural features, which modify the local climate as well, generating a microclimate. Particularly the differences between de air temperature in cities respect to de rural or edge area is known like “heat island effect”. Particularly, MMA, presents a heat island effect whose maximums reach the 10 °C, in winter as well in summer, with an average value of 6°C throughout the yearly cycle [2].

Studies performed during the last decade which correlate energy consumption with the heat island effect, have demonstrated that for cities of more than 100,000 inhabitants, the energy consumption during pick hours is raised by 1.5 to 2.0 % for each degree in the city’s temperature’s increase [3]. Particularly in Argentina, the residential demand of electric energy represents more than 40% of the distributor’s total demand and shows growth’s rates that increase every year since 2002. At the same time, the installation of air conditioned equipment in the country is growing steadily; and is known that the increased use of household electric appliances is the cause greater energy demand.

According to the INDEC (National Institute for Statistics and Census), the production of air conditioned equipment grew a 250% between 2000 and 2005

Besides, it contributes to the increase of environmental pollution in two ways: directly, given that higher urban temperatures operate as a catalyst of the chemical reactions of the combustion gases present in the atmosphere, generating larger quantities of smog; the smog production increases by 5 % for each 0.5 °C of the maximum temperature increased above 20 °С; and in an indirect way, since the increase of the energy consumption required for additional cooling, causes that the generating plants emit larger quantities of combustion gases (CO2, CO, NOx, SOx, water vapour and methane); all responsible for global warming or green-house effect and the acid rain, among the best known environmental effects.

Often the discussion is about how hot or cold is the city, in terms of thermal comfort; in this case it is simple enough to measure the air temperature. But in some cases, it is important to find a way of measuring the impact of the temperature increase over the energy consumed and the air quality of the city. In this sense the degree-day method is a well-known and the simple method used in the heating, ventilating and air-conditioning industry to estimate heating and cooling energy requirements in buildings. The severity of a climate can be characterized concisely in terms of degree-days. But in general the degree days calculations are performed taking into consideration the meteorological data provided by standard meteorological stations which are situated generally in the city’s surroundings.

For this reasons this paper explore the geographical distribution of heating and cooling degree-days in MMA taking into account the influence of urban heat island’s intensity over the heating and cooling energy requirements in the city and quantifies the green house gases emissions derived from this impact.

On other hand degree days affect urban dwellers not only in terms of energy consumed, also the growth rate of many organisms is controlled by temperature. Diverse concepts related to degree — days are used to connect plant growth, development, and maturity to air temperature. In addition degree-days are linked to air quality and health problems. The modification of the urban ecological balance plus the worsening of life quality affect the city’s sustainable condition.

It is well well-known the energetic and environmental crisis that affects our planet as a result of the irresponsible way of using natural resources during the last century. The energy performance of buildings has taken on a greater significance with the setting of domestic and international targets for the reduction of greenhouse gas emissions. Energy use is the largest contributor to these emissions. It is expected that the results presented in this paper and their availability fill a gap in information needed by building designers and engineers for simplified energy calculations and construction of buildings with rational energy use and minimal emissions in the city of Mendoza.

2. Methodology

The studies performed by Oke [4] offer a valuable help to collect meteorological data in urban areas. It is possible to obtain results of acceptable quality over the heterogeneity of the urban areas, but this requires paying careful attention to the principles and concepts specific to urban areas. In this work, the guidelines suggested by the WMO on “Instruments and Observing Methods”, report Nr. 81 entitled “Guidance to Obtain Representative Meteorological Observations at Urban Sites”

[4] are applied.

With the purpose of quantifying of Urban Heat Island intensity; the thermal behaviour of the city was monitored in a continuous fashion, during a complete yearly cycle, starting from January 2005, 16 fixed points, equipped with automatic stations, measuring temperature and humidity in the urban canyons every 15 minutes, were installed. The stations installed are of the type: H08- 003-02, two channel logger with internal temperature and user-replaceable RH sensors, temperature measurement range: -20 to 70 °С, temperature accuracy: +/- 0.7° at 21°C, RH measurement range: 25 to 95 % RH (user replaceable RH sensor), RH accuracy: +/- 5% RH. The sensors were placed at a height of 2.5 m from the street level floor [4], within perforated PVC white boxes, in order to avoid irradiation and assure an adequate air circulation. Figure 1 presents the locations of fixed measurements within MMA and their installation features.

The severity of a climate can be characterized concisely in terms of degree-days, but in general, the degree-day’s calculations are performed taking into consideration the meteorological data provided by standard meteorological stations which are generally located in the city’s surroundings. Particularly in Mendoza city the three stations corresponding to the National Meteorological Service of Argentina are placed on opposite sides of the city’s edge and the third one in a central position of a densely forested large urban park. See red stars figurel.

image518

Fig 1. Locations of fixed measurements within MMA and installation features of them.

The degree-day method estimations are accurate if the internal temperature, thermal gains and building properties are relatively constant. In the study, the calculation of heating and cooling degrees days has been carried-out from the registered data, applying the method developed by Erbs, to each series of data, as it is described in Al-Homud [5]. The monthly degrees-day values were calculated according to equation 2.1. In the equations, Ta is the monthly average temperature; D m is the amount of days of the month; aDy is the standard deviation of the monthly average temperature respect to the annual average temperature and aDm is the standard deviation of the daily average temperature respect to the monthly average temperature.

DD m=o m (D m) 15 *[h/2+ln (e-ah+ e+ah)/2a]

(ec.2.1)

Where:

h= (T base — Ta)/ [a m (D m) 1/2] for the heating degree days

(ec. 2.2)

h= (Ta — T base)/ [a m (D m) 1/2] for the cooling degree days

(ec. 2.3)

a=1.698 (D m) 1/2

(ec. 2.4)

a m= 1.45-0.29 Ta+0.664 a y

(ec. 2.5)

The calculations have been made using 18 °C bases for the computations, this temperature has been selected from the distribution graph of the energy consumptions versus the registered average temperatures [1], the tendency curve of this distribution shows a point of inflexion around 18°C. The degree-days obtained have been compared with those corresponding to the weather station airport (- 32,85°, 68,78° longitude and 700 m. a.s. l. of altitude) located in the NE sector of the city’s outskirts.

Although the zoning obtained from the collected data during 2005, does not have meteorological rigor, because greater extensions time series are required, its value is to point-out the range of the urbanization impact on the HDD-CDD parameters calculation. Table 1 shows the comparison between the data registered by the airport’s station during 2005 versus the data registered in the 90’s. It is observed that the monitored year does not display atypical behaviour that underestimates the conclusions derived from this study.

Table 1. Average temperatures registered by the Airport’s station for the 90’s and during 2005.

Month

Jan.

Feb.

Mar.

Ael

May

June

July

Aug.

Sept.

Oct.

Nov.

Dec.

Airport 90’s f°C|

24,9

23,5

19,9

15,4

11,6

7,7

7,3

9,9

13,1

17.5

21,7

24.1

Airport 2005 [°C]

25,3

24,2

20,3

14,8

121

95

89

10

12,6

18

23,8

25,1

The heating and cooling degree-day calculated from the data registered by each fixed station within the urban grid have been interpolated with the purpose of zoning their distribution within Mendoza’s Metropolitan Area (MMA). The interpolations have been done using the IDW method (distance’s inverse), which, compared to the Krigging Universal and the Spline methods, has demonstrated to be the most accurate, since it minimizes the quadratic error. In order to ease the calculations, the number and distance to neighboring points to be taken into consideration, should avoid those too distant and restrict them to a determined number. A variable radius, with a maximum limit of 2,000 m and a number of 12 points has been considered for the analysis. Their cartographic representation and digitalization in (GIS) was made using Arc. View 3.6.

To predict the impact over the global warming emissions that produce the heat island effect, the calculations were made taking into consideration de percentage variation between the urban HDD and CDD values and those calculated from the data registered at the airport. The factor emission values derived from the electricity generation and natural gas production in Argentina are expressed in kg of CO2 and were taken from the information provided by National Direction of Energetic Prospective. With the scope of compare the annual emissions, this values was expressed by MJ, considering: Natural Gas PCI=8400 kcal/m3 and 1KWh =3.6 MJ.

Table 2. Factor emission values of electricity generation and natural gas production in Argentina.

Natural Gas emission

1,951 Kg CO?/m3

0,232 Kg COTMJ

Electricity emission

0,459 Kg CO2/ kWh

0,127 Kg CO2/MJ

(*) Source: National Energy Department

3. Results

Monitoring results

1.2 PV facade system results

The systems have been monitored since their installation at June 2005, for the facade, and December 2005, for the park.

Fig. 4 presents the values of the monthly averages of the daily energy produced in the facade, per installed peak power. In general, this system produces more energy in winter periods with a maximum average daily production of 47.3 kWh at November 2007. The production minimum occurred at June 2005 with a daily average production of 20.2 kWh.

image409

Month

Fig. 4. PV facade — Monthly average of the daily energy produced, per installed peak power.

At Table 3 we present the yearly irradiation and yearly energy produced by PV Facade system. The average yearly irradiation measured in the vertical facade, is about 1 155 kW/m2 and the energy production is about 977 kWh per kW of peak power installed.

Year

Power

Irradiation

Production

(kW)

(kWh/m2)

(kWh/kW)

2006

12.16

1 118

950

2007

12.16

1 193

1 004

Table 3. Yearly energy produced by PV Facade system, per installed peak power.

System efficiency, primary energy and CO2 emission

A major impact on the energy consumption and CO2 emissions is related to the efficiency of the heating and/or cooling system, its efficiency on production, emission, control and distribution. Conventional systems used in Passivhaus buildings must have a high performance level, should have low levels of emissions and primary energy consumption.

The energy consumption of a building can be expressed in terms of equivalent consumption in primary energy — Tons of Oil Equivalent — or in terms of CO2 emissions. However, the conversion factors are country dependent on the energy mix and the way the energy is generated. Renewable energy is favourably a good choice.

3.7 Appliances and lighting

The adoption of high-efficiency appliances can significantly reduce the total energy consumption. Whenever possible the design should rely on daylight and minimize the use of artificial light. Although inefficient appliances can help reduce heating loads in winter, this is a very inefficient way to heat a house. Also, internal gains from inefficient appliances increase summer cooling loads and the overall net energy balance is usually negative.

There are simple and effective passive strategies that minimize or reduce the energy consumed. Adopting them depends mainly on the occupants’ behaviour. Using the washing machines during night when the energy demand is reduced and cheaper, drying the linen in the sun instead of in a tumble dryer, switching off appliances instead of relying on standby mode are just a few examples.

Study of Different Curtainwall Facade Options

1.4. South-Facing Curtainwall Facade Scenarios

The impact of the five different south-facing curtainwall facade scenarios described in Table 2 on a building heating and cooling load was studied for the three cities identified in Table 1. For each scenario, the curtainwall was assumed to consist of 50% of a multi-layer glazing system as a vision section, and 50% of either spandrel panels or multi-glazing BIPV assemblies as the non-vision section. All the multi-layer glazing systems (with and without PV) were assumed to have low-e coating, 6mm glass panes, 20mm air cavities and aluminium framing with 19mm thermal break and insulating edge spacers. The vision sections characteristics were obtained with FRAMETMplus [13] using the curtainwall framing system. The U-value and SHGC were evaluated at 2.03W/m2oC and 0.39 for the double-glazed system, and 1.2 W/m2oC and 0.28 for the triple-glazed system.

Table 2. South-facing curtainwall facade scenarios.

#

Vision Section (50%)

Non-Vision Section (50%)

1

Double-glazed

Spandrel (U-value=0.55 W/m2oC)

2

Double-glazed

BIPV configuration A

3

Triple-glazed

BIPV configuration B

4

Triple-glazed

BIPV configuration C

5

Triple-glazed

Spandrel (U-value=0.55 W/m2oC)

Detailed thermal simulation of classified facade systems

The classification of fa? ade systems by “morphological” aspects, i. e. form, dimension, construction, material, function etc. led to a great variety, (23 parameters and up to six variations per parameter in the morphological box). The number of classified solutions could dramatically be reduced, if only the physical properties were considered, which had an influence on the energy demand. It was possible to reduce the 23 parameters to six energy relevant parameters: window/fa? ade (Awindow), mean heat transmittance of fa? ade (Um), heat gain coefficient of glass (gG), heat gain coefficient of shading devices (FC), light transmittance of glass (TL), equivalent air change rate (neq). For each parameter there are defined five equidistant values, the bandwidth between lowest and highest value given by minimal building standards and best practice solutions (Table 1).

Table 1. Equidistant steps and bandwiths of relevant parameters (U-values of opaque and transparent elements

were combined to a mean faqade value)

north

East

south

west

0,300

0,475

0,650

0,825

1,000

0,150

0,290

0,440

0,580

0,720

0,500

1,080

1,650

2,230

2,800

0,370

0,460

0,560

0,650

0,740

1,0000

0,8125

0,6250

0,4375

0,2500

0,510

0,585

0,660

0,735

0,810

0,180

1,010

1,840

2,670

3,500

image377

In total there were 15,625 facade combinations to be simulated by TRNSYS for each of the (four) major fa? ade orientations. All simulations were carried out under the same boundary conditions, such as office floor plan and weather data.