In coporation with the Institute of Thermal Engineering at the Graz University of Technology arsenal research applied expert tools in order to support the ENERGYbase planning team by providing scientific expertise. Herewith the energy performance of ENERGYbase office building has been considered and analysed in an early phase of the planning procedure and additionally some important advises and analysis in order to optimise the energy system performance were

developed and conducted. The scientific support actvities were based on using simulation expert tools and were mainly focused on following emphasis:

• Scientific support of an integrative planning procedure:

Challenging is both the complexity of planning and the integration of non-standard technologies and systems in such a building project. Therefore an integrative planning approach has been applied in order to achieve the ambitious ENERGYbase project targets by involving scientific energy experts in the communication process from the beginning on. arsenal research as a centre of excellence for sustainable buildings and energy systems has scientifically supported the planning team and did essential contribution and advice in time, especially related to the HVAC concept and renewable energy systems. The scientific support was mainly based on operating expert tools — like transient building an system simulation and computational fluid dynamics CFD (2)- and herewith generated results and their comprehensive analysis and intepretation have been presented and discussed on project planning meetings.

• Assessment of the energy and thermal building performance:

The overall ENERGYbase concept meaning both the architectural and energy system design aims to achieve high values of energy efficiency, to use of renewable energy sources and to provide an strongly improved user indoor comfort. In order to assess the thermal building performance of the office building arsenal research applied the simulation environment TRNSYS (3) and developed a comprehensive and flexible building modell. Due to this approach the impact on the ENERGYbase building performance by changing energy and/or comfort relevant parameter could be quantified based on the current status of planning. Consequently a continious assessment of the energy building performance improved the quality of planning, especially with regard on pre-defined energy and comfort targets.

• Detailed analysis on selected energy systems

The indoor temperature of ENERGYbase offices is controlled by thermal mass activated construction elements. Due to the fact that the heat transfer of the thermal mass activation is limited arsenal research modelled and simulated this low temperature distribution system in order to confirm whether the internal and external loads of ENERGYbase offices can be rejected or additional equipment has to be integrated. Furthermore by using transient system simulation arsenal research gave advice which control strategy of the thermal mass activated construction elements results into a low energy demand and a sufficient indoor comfort.

The indoor humdity of ENERGYbase offices is controlled by an air-conditioning system which uses a solar thermally driven desiccant evaporative cooling technology (DEC). This solar-assisted air-conditioning system is an non-standard system which uses solar heat to regenerate the dehumidification unit. Because the DEC system technology is characterised by thermodynamic limits arsenal research modelled and simulated the system performance and assessed the overall system design and concept.

• Detailled comfort analysis of south oriented offices

The architectual ENERGYbase design and the concept of the south faced facade allows a high ratio of daylight use in the entire office building which enables a significant reduction of electricity demand for artifical lighting. Additionally special internal jalousies guide daylight into the deepness of the south offices which improves daylight comfort. arsenal research did scientific studies on the thermal comfort for an future ENERGYbase users which would be placed near to the

south faced facade. Different types of internal jalousie were modelled and investigated regarding their impact on thermal comfort.

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:

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

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).

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.

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)

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.

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].

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.

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.

Yukio Ishikawa

Division of Architecture, Graduate School of Engineering, MIE University, JAPAN
1577, Krima-machiya-cho, Tsu-city, Mie-prefecture, 514-8507, Japan
Corresponding Author, ishikawa@arch. mie-u. ac. jp

Abstract

The author has been investigating passive cooling systems in buildings with their environment controlled biomimetically and autonomously by simulating the physiological functions of animals and plants. The author directed his attention, making an attempt to apply it to evaporative cooling in buildings, to the perspiration function, one of the functions of heat dissipation of human bodies. A perspirable building with a perspiration function in its walls and roofs has been researched and developed. Those walls and roofs can absorb and desorb water autonomously, depending on their temperatures, water absorption below a certain specific sense — temperature, desorption above it. This paper describes the details of the perspirable building, development of the improved perspirable roof and experimental results of thermal performance of the roof. Further the seasonal passive cooling effects and energy saving effects are predicted by the theoretical simulation of room temperature and thermal load in a typical Japanese detached house perspirable. Also described are the areal optimum specific sense-temperatures of the perspirable roof.

Keywords: perspirable building, evaporative cooling, thermo-sensitive hydrogel, biomimetics

1. Introduction

There has been a growing tendency to attain a desirable living environment in buildings by energy saving and low global emission with the use of natural energy resources and natural environment.

Since we need both heating and cooling in Japan, it is necessary to investigate passive cooling in summer as well as passive heating in winter. From this viewpoint, the author has been investigating passive systems in buildings where the environment is controlled biomimetically and autonomously by simulating the physiological functions of plants and animals. As an energy saving building in the next generation, the building called as an environment-harmonized biomimetic building, has been developed, which simulates the environment physiology mechanism of a human body and other organisms. The human physiology mechanism such as perspiration, respiration, gooseflesh and shiver is simulated and applied to environment symbiosis and environment control in buildings. According to the concept, the building wall (roof and external wall) which can autonomously vary thermal insulation performance and the window which can autonomously vary the insolation shading performance, for example, were developed[1,2]. As one of the approaches, following the previous paper[3], this paper introduces research and development of a perspirable building which simulates heat dissipation by

perspiration as a thermo-control mechanism in the human body physiology. To begin with, an outline of a perspirable building is described, and the experimental result of thermal performance of the improved perspirable roof is shown. In addition, estimating the areal optimum specific sense temperature of the perspirable building by theoretical simulation, in which the autonomous perspiration (water absorption and desorption) of wall and roof becomes possible at a certain temperature (the specific sense temperature), the areal thermal effect of the autonomous perspirable building is shown, compared with the one of non-perspirable.

Many authors have made analysis of cavities or ventilated fa? ades under buoyant flows. However they are all limited to laminar symmetric boundary conditions. Within this research a methodology based on

Reynolds Averaged Navier Stokes (RANS) CFD simulations is used over laminar and asymmetric flows. The main scope is to obtain reliable correlations for Nu and for the mass flow rate.

The important physical properties of the window for the energy and day-lighting performance are the thermal transmittance, the total solar energy transmittance and the light transmittance. These parameters are defined in European and international standards and are usually known as the U — value, g-value, and xv-value, respectively [9,10]. The U-value is expressed in the unit W/m2K and is thus equal to the thermal conductivity of the window. The g value, also called solar factor or solar heat gain coefficient, is given as the fraction of incident solar power entering through the window. It includes radiation absorbed by the window and then reemitted to the inside of the room. It is a dimensionless unit with a value between 0 and 1, and is frequently expressed in percent. The light transmittance is the fraction of visible light directly transmitted through the window. In international literature the U-value is usually quoted for the complete window, including frame and edge. However, in this paper the given U — and g-values are for the center of the glass. The g — and Tv-values are quoted for the glazed area and only for normal incidence. A detailed characterization of the window performance requires that these properties are also known for oblique angles of incidence of solar radiation [11]. For the appearance of the window also the light reflectance and colour rendering are of importance, but they do not usually enter energy calculations. Individual panes are also characterized by the thermal emissivity of the coated surface. The hemispherical emissivity is calculated from the normal emissivity which is given by the equation s=1-R, where R is the near normal infrared reflectance. The emissivity of uncoated glass is 0.84 while low — emissivity coatings can have values as low as 0.03.

Low-emissivity coatings for solar and thermal control of modern windows have led to a revolution in window technology. With emissivity values below 0.10 W/m2K windows with U-values well below 1 W/m2K can readily be manufactured and still have high light transmittance. This can be compared to a standard double glazed window with a U-value of around 2.7-3.0 W/m2K. Solar control coatings with double silver layers can have light transmittance which is a factor of two

higher than its solar transmittance. This is almost identical to the maximum possible limit. In general we talk about low-e windows for cold climates and solar control windows for hot climates. The low-e window is characterised by a low U-value and a high g-value. Solar control windows tend to have low g-values and may or may not have low U-values, depending on the window type. Some solar control glazing products are based on absorption in the glass itself and not on a coating. Some solar control coatings are low-emissivity coatings and some are not. Low-e solar control coatings are usually based on one or two thin silver films and are also known as solar selective coatings. They are highly reflective in the near infrared part of the solar spectrum.