Category Archives: EuroSun2008-4

Measures to reach the target of 75% energy reduction

Starting from the middle bar in figure 1, the question is how to further reduce the primary energy consumption of a dwelling, in particular the (net) electricity consumption. Following the Kyoto pyramid, the three steps to reduce energy consumption are (in this order): 1) reducing energy demand, 2) application of renewable energy and 3) efficient use of fossil energy. Let’s explore how far we can
go in each step. In relation to the renovation concepts, building related measures are of particular interest.

Solarch.-Vision

Solarch.-Vision is a perspective, plan or etc. diagram which shows the situation of the building skin under the kind/unkind faces of the sun. It brings a brand new vision to the architects, urban designers and landscape architects to discover the advantage/disadvantage of decisions about kind/unkind faces of the sun in each location through the design process.

By selecting a city from the list or entering the available data of a location such as latitude, elevation, turbidity, monthly average of min. and max. temperatures, the architect could define the building site. As the codes of Solarch.-Vision(by author #1) has been developed on MAXScript(the built-in scripting language for 3ds Max and Autodesk VIZ.), it is easy for the architect to use 3dsMax or any other CAD software to model everything needed. Next the architect would set up the date and time definition of analysis, and by selecting the cameras it is possible to observe an extraordinary solar diagram.

image170

Fig. 7. Yearly Solarch.-Vision of building complex in Tabas(left), Shiraz(middle) and Hamedan(right)

image171

Fig. 8. The situation palette from red(in undesirable shade/shine) to blue (in desirable shade/shine)

image172

Fig. 9. Solarch.-Vision in summer(left) and winter(right)

10th October, Lisbon — Portugal *

Подпись: Delete | Подпись: Hide Diagonal Edges

North Direction: 0.0 t

Подпись: + solarch Vision

Sky Radius (km):

1150000000.0

Sky Origin:

Fig. 10. Solarch.-Vision rollouts in Autodesk 3ds Max

1. Conclusion

The method and software described in this article will help architects, urban designers and landscape architects of the world to design better with the sun in the early next years; but still there are many problems that a proper architecture must solve.

References

[1] Samimi Mojtaba, “Thesis: From the Sun to the Architect”, Library of the Faculty of Architecture and Urban Planning, Shahid Beheshti University, Tehran, 2007.

[2] Samimi Mojtaba, Parvizsedghy Laya, Adib Morteza, “A New Approach for Solar Analysis of Buildings”, SERP, WORLDCOMP’08, Nevada, 2008.

[3] Remund J, Kunz S., “METEONORM”, Bern METEOTEST, Fabrikstrasse, 2003.

[4] Tahbaz Mansore, “The Sun and Building Orientation”, Library of the School of Architecture, Shahid Beheshti University, Tehran, 1983.

[5] Olgyay Victor, Olgyay Aledar, “Solar Control & Shading Devices”, Princeton University Press,

image176Princeton N. Y., 1976.

Energy-efficient buildings in Norway — from low energy standards to net zero energy buildings

M. Haase1* , I. Andresen1, B. Time1, and A. G. Hestnes2

1 SINTEF Building and Infrastructure, Trondheim, Norway
2 NTNU, Faculty of Architecture and Fine Arts, Trondheim, Norway
* Corresponding Author, matthias. haase@sintef. no

Abstract

For typical energy efficient office buildings different energy concepts are studied and the role of the building envelope in each of the concepts is described. The total energy consumption is simulated for four different construction standards and the results are compared. First, the Old Norwegian standard from 1997 was studied and the resulting energy savings of special construction details is shown. Then, the resulting energy savings of the New Norwegian regulations (TEK 2007) are calculated. Then, different energy concepts are applied to a typical office building and the resulting energy savings are shown. Finally, possibilities for on-site renewable energy production to reach zero net energy buildings are explored.

The results show that significant efforts are needed in order to bring Norwegian buildings up to the passive house standard. In particular, significant improvements of construction details regarding insulation levels and air tightness of the envelope are needed. Also, efficient heat recovery systems are crucial. A careful design of super-efficient envelope systems and building geometry can lead to zero net energy buildings in Norway.

Keywords: climate, energy concept, sensitivity, simulation

1. Introduction

In order to realize energy performance requirements of a higher standard according to today’s and future Technical Regulations, it is necessary to develop new design strategies without sacrifices in other performance codes, standards or guidelines. Prior experience related to the introduction of new energy performance requirements has shown that the design energy performance levels are either not met, or they are fulfilled at the expense of indoor climate, technical quality (e. g. moisture related problems), or architectural quality. Therefore it seems appropriate to determine the parameters of building design that have the biggest influence on energy consumption of buildings. Special focus has been put on the building envelope and some parameters that have an influence on the building load [1]. A lot of work has been done for residential buildings and thus this paper focuses on office buildings [4].

Heating Systems and Strategies

image346

This building was since the early phases of the project planned to maximize the solar gains into the building through the windows facing south. The envelope of the building is external insulated, with 5 cm thick in a single masonry wall and has 10 cm insulation on the roof. The building has a solar thermal system to assist the auxiliary heating system, for the winter season when necessary. In fact, this auxiliary system has been used very rarely mainly in the north part of the building in periods with a sequence of days with no sun. In the heating season, the heat produced in the PV system in the fa? ade is recovered by natural convection to heat the south facing rooms.

1.1. Winter thermal performance

During these two year monitoring campaign (February 2006 until February 2008) the building showed a very good thermal behaviour in the south part of the building, where the mean temperatures varies between a mean minimum of 17°C to a mean maximum of 24°C. In the north part of the building, the temperature are a quite bite lower than in the south part of the building, 1 to 2°C, which consequently imply the use of some auxiliary heat source. Table 1 presents the mean values for the winter months, and it is very important to see that during daytime (Tdaily) the mean temperatures are always above 20°C.

Table 1. Mean Temperatures

(external, internal mean, internal mean maximum, internal mean minimum and internal mean daily).

Feb06

2

О

<

О

ON

Dec06

Jan07

Feb07

2

О

<

о

"-j

Dec07

ос

о

І

Feb08

10.3

16.0

10.8

10.9

12.9

12.8

9.8

11.5

12.2

21.4

21.5

19.4

19.6

19.7

20.3

18.7

19.9

19.7

23.7

24.0

23.0

23.3

22.6

22.9

21.6

22.8

22.6

16.0

20.1

17.4

17.6

18.0

18.7

17.1

18.3

18.0

20.7

22.5

22.5

21.1

20.9

21.6

19.9

21.2

20.9

Figure 3 presents the hourly temperatures, in the 3 levels of the building, for the coldest month in winter (January 2007), where it is possible to see that during day time the temperatures are always above 20°CC, except days 9, 10, 11, 17 of January where some extra heating was needed.

Edificio Solar XXI — INETI Temperatures de ar interiores vs exterior

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Fig. 3. Hourly temperatures in Solar Building XXI in January 2007

Grain Size Distribution Analysis

An idea of the degree of grain size uniformity (i. e grain size distribution) can be obtained using the grain size distribution method. It involves measuring the area of the largest observed grain Amax and diving it by the average grain area A. the ratio of Amax/A for a uniform grain size distribution in metal is given in the range of 1.8 to 2 [2-5] The greater the degree of non uniformity the higher the ratio of Amax/A

i. e Gd = Amax/ A 15

Another method of estimating the grain size distribution is to use the porosity factor given as:

f

100 1

v

 

BulkDensity
TheorreticalDensity y

 

Pt

 

Where for example the Theoretical Density of a material BX is given by

(M. wt of B x Density of B) (M. wt of X x+)ensitv of X) Mol wt of BX

Mol wt of BX

Shadow and incident solar radiation on external surfaces

Fig.5 shows the shadow ratio on the south window of the living room (LD) in winter sunny day (February 17). The shadow ratio of the no adjacent houses Case A is 0% in the daytime. To the contrary, the shadow ratio of the adjacent houses Cases B and C were about 100% by the adjacent houses except for 14:00 from 13:00. Fig. 6 shows incident solar radiations of the south window of the living room in winter sunny day (February 17). Daily total incident solar radiations for the no adjacent Case A and adjacent Cases B and C were 38.2kWh and 7.0kWh, respectively. Daily total incident solar radiations for the adjacent Cases B and C reduced by 80% against the no adjacent Case A.

In summer, since the solar altitude is high, the south surface does not receive the shadow by adjacent houses. Fig.7 shows the shadow ratio on the west surface in summer sunny day (August 9).

image070 Подпись: 6 5 й 4 3 2 1 0 Подпись: Л image073

The shadow ratio of adjacent houses Cases B and C were about 100% by the adjacent houses in the afternoon. Fig.8 shows incident solar radiations of the west surfaces in summer sunny day (August 9). Daily total incident solar radiations for the no adjacent Case A and the adjacent Cases B and C were 139.6kWh and 65.6kWh, respectively. Daily total incident solar radiations for the adjacent Cases B and C reduced by 53% against the no adjacent Case A. This result is the same also for the east surface.

Solution Approaches for the Problem

For the solution of the problem basic principles can be summarized like; for collectors and storages;

• Gathering the collectors and tanks

• Organizing of system components

• Harmony with the building

• Providing aesthetical sufficiency.

When the flexibility of individual applications and the economy of natural convection systems are taken into consideration as the dynamics of common usage, it is clear that solution approaches has

to include both the individual usage and central systems.

The central systems are which transfer the heat that is gained from the collector area to a collective storage and enables each user of the building to benefit from the hot water in distinct units. It is obvious that, these systems can be configured in many ways depending on the utilization purpose, economy, qualitative and quantitative of the load and requirements of the users. As these systems are going to be large scale applications they have to be designed carefully and with the

help of computer programs which takes local climate take into consideration. One of the most important issue in these systems is to balancing the payments of different hot water consumptions of the users. And for this it is required to develop advanced technical and technological engineering approaches. It is apparent that the central system’s first investment costs are more expensive then individual systems. However, in long term the central systems are more economical, healthiness, permanent and can provide high quality solutions.

The individual usage systems can be described as an application form that allows to each user to install his/hers solar energy system in a pre-defined private area. When the economical and practical barriers of central systems are taken into consideration this approach which provides practical solutions are more effective for expanding the applications in short term. In this system approach which aims to gather and organize the collector and tank regions so as to allow individual usage; standardization, durability, user friendly installation, constructional infra-structure, maintenance, repair, recycling are the other important issues besides basic principles mentioned above.

By considering these application forms, 2 basic approaches can be mentioned for preventing the visual pollution caused by the systems:

1. Invisibility of systems,

• To obstruct the system visibility

• To use building integrated systems that seems like conventional material.

2. Integration of systems to building,

• Usage of building integrated systems

• Usage of systems as a building component as pergola, fender, parapet, eaves and etc)

Basic aspects for concentrating photovoltaics

The concentrating solar systems use reflective (flat or curved mirrors) and refractive (mainly Fresnel lenses) optical devices. These solar energy systems are characterized by their concentration ratio (CR, or simpler C) and can be combined with “linear focus” (2D) or “point focus” (3D) absorbers for low (C<10X), medium (C<100X) or high (C>100X) ratios, respectively. Concentrating systems with C>2.5X must use a system to track the sun, while systems with C<2.5X can operate with stationary concentrating devices. The low concentrating ratio systems (C<10X) are of particular interest for the photovoltaics as they are of linear geometry and thus one tracking axis is enough for their efficient operation. The distribution of solar radiation on PV module and the temperature rise of it affect the electrical output. The uniform distribution of the concentrated solar radiation on PV surface and the application of a suitable cooling mode contribute to an effective system operation, considering the achievement of the maximum electrical output. In low concentration photovoltaics, flat and curved reflectors, Fresnel lenses and dielectric lens type concentrators have been studied. The performed works can be grouped in systems with V-trough reflectors [1-4], achieving concentration ratios up to two with east-west or north-south orientated reflectors, CPC (Compound Parabolic Concentrator) type reflectors [5-10], which are usually static and CR<2.5, refractive concentrators of 3D acrylic lens [11-13] and linear Fresnel lenses [14-16]. Comparison results give an idea about the benefits of concentrating photovoltaics and point-focus concentrating systems with a fixed flat plate PV module [17-19] show that the concentrating systems produces 37% greater electrical energy than the flat PV modules.

In the University of Patras, research works on low concentration photovoltaics have been performed last years [20-25]. PVs can be combined with thermal collectors to form hybrid photovoltaic/thermal systems, which can be used to buildings contributing to the reduction of the required available roof or faqade installation surface area. In PV/T system applications and considering that the electricity is of priority, the operation of PV modules at lower temperatures is necessary in order to keep PV cell electrical efficiency at a sufficiently higher level [23]. This demand limits the effective operation range of PV/T system thermal unit in lower temperatures and the extracted heat can be mainly used for low temperature thermal needs (space heating and natural ventilation of buildings, air or water preheating, etc). To overcome it, the system can be combined with a typical thermal collector system circulating the preheated water of PV/T unit in the lower part of it [24]. The PVs and the PV/T systems can be combined with linear concentrators, as of Fresnel lenses or flat type and Compound Parabolic Concentrating (CPC) reflectors to achieve cost effective solar energy conversion systems [25]. This subject is very interesting for the practical application of the photovoltaics, which would result to a wider application of these solar energy conversion systems.