E. Salvador1*; R. David2; K. Lepetitgaland3; F. Lopes4 and G. dos Santos5

1 Eletrobras, Support Division, PROCEL, Av. Rio Branco 53/20, 20090-004 Rio de Janeiro, Brazil 2 Eletrobras, Energy Conservation Planning Division 3 Eletrobras, Brazilian Center of Information on Energy Efficiency — Procel Info 4 Eletrobras, Energy Efficiency Department 5 Eletrobras, Energy Conservation Nucleus of Research and Projects * Author for correspondence: salvador@eletrobras. com

Abstract

The Brazilian “National Electricity Conservation Program” — PROCEL runs regular surveys in the electric energy consumption market in order to assess the number of electric equipments owned by each household as well as their respective types and usage. These studies are not only used as valuable database to plan better the actions of this Program; they also evaluate its performance by identifying the level of penetration of the most efficient electric equipments within the residential sector in which PROCEL runs its main lines of action: to make available and to promote the most efficient technologies.

In the case of solar energy, PROCELs orientation is to encourage its wider use for water heating as well as to improve technological advance in heating solar collectors and thermal tanks.

In this context, the purpose of this work is to present an overview of: the usage and the efficient utilization of solar energy for water heating in Brazil; the evolution of energy efficiency in these types of equipments as well as the main technological advances in this sector.

Keywords: PROCEL Seal, water heating, solar energy, market assessment

1. Introduction

PROCEL was established in December 1985 by the Brazilian Government in partnership with the Ministries of Mines and Energy (MME) and of Trade and Industry (MIC) [1]. Eletrobras is the Brazilian holding for the generation, the transmission and the distribution of electric energy nationwide [2] in charge of the implementation of PROCEL. Its objective is to promote awareness about electric energy consumption in order to avoid waste and to lower the costs and the investments made to respond to the increasing demand in the electrical sector. PROCEL runs numerous activities through various sub-programs to foment the efficient use and usage of electric energy. In turn, these sub-programs focus at the level of different sectors such as Residential,

Trade, Industry, Education, Sanitation and Public Lighting [3]. Following the 2001 national electric energy crisis and the subsequent rationing of this input, PROCELs actions have been drawing more and more attention. PROCELs action frameworks are based on a nationwide survey, regularly ran, to assess the existing number, type and usage of electric equipments called Studies about the Ownership and the Utilization of Equipments (Pesquisa de Posse de Equipamentos e Habitos de Uso — PPH in Portuguese) [4] which assist the strategic planning of the Brazilian electrical sector and define PROCELs action priorities and its achievements.

The latest survey, ran in 2005, was supported by the Global Environment Facility (GEF) as part of the Energy Efficiency Project (PEE in Portuguese), the result of a partnership between the World Bank and Eletrobras_ the latter actuating as the institution obtaining and transferring the funds

donated to the Brazilian Government [5]. This survey was lead by the Papal Catholic University — Rio de Janeiro (PUC-RJ in Portuguese), hired by Eletrobras. It was run on equipments from sectors of both high and low voltages. Representative of the residential sector, for example, a total of 9,847 households [6], from 21 separate electric energy utilities, were investigated.

In Brazil, since 2007, projects encouraging the use of solar energy for water heating, in particular, have turned more and more common to meet the Mecanisms for Clean Progress (Mecanismos de Desenvolvimento Limpo-MDL in Portuguese). Indeed, heat generation at peak-hour represents a very high percentage of the total electric energy consumption in Brazil, because electric systems are designed and built to meet the maximum demand requested at any given time. Considering these facts, one can only ponder the unfortunate contribution to Global Warming and its subsequent negative effects on the environment.

I. Knight1*, M. Rhodes1, F. Agyenim1 and E. Ampatzi1

1 Welsh School of Architecture, Cardiff University.
Corresponding Author, knight@,cf. ac. uk

Abstract

This paper provides conclusions from a WERC-funded project undertaken to assess the potential for Solar Thermal Heating and Cooling Systems to reduce the carbon emissions from domestic properties in Wales, UK. The project is based on 4 main elements:

• the physical testing of a novel solar thermally driven air-conditioning system in the Welsh climate to ascertain the real-world and laboratory performances of the system as a whole and its principal components

• the characterisation of the Welsh Housing stock into 13 major construction types

• the thermal modelling of these 13 types to obtain their heating, cooling and DHW demands, and hence their ‘traditional’ carbon emissions and the ‘solar thermal’ carbon emissions

• the aesthetic and design issues to do with integrating such systems into domestic properties, and their potential effect on the overall system efficiency

This paper synthesises some of the findings from these elements to provide a first answer to the question about the potential contribution that Solar Thermal technologies could make to reducing the carbon emissions associated with heating, cooling and DHW use, from both new and existing housing in Wales. This paper presents these findings for each of the housing types individually, as well as for the domestic sector in Wales as a whole.

This information is of importance in establishing whether Solar Thermal should be part of the country’s future energy mix, and potentially how much it could contribute. The work is especially timely within Wales’ stated ambition for all new buildings to be built to zero carbon standards by 2011.

The main conclusion from this work is that the use of Solar Thermal for heating, cooling and DHW for domestic housing in Wales leads to predicted reductions between 10 — 25% in the total carbon emissions, regardless of the type or age of dwelling.

Keywords: Solar Thermal Cooling, Solar Thermal Heating, Carbon Emissions Savings, Existing Buildings, Solar Thermal DHW, Wales

1. Introduction

This paper presents the main findings from a physical and thermal modelling study of the potential for Solar Thermal Air Conditioning Systems (STACS) to reduce the carbon emissions from the domestic housing sector in Wales, United Kingdom. As an autonomous region of the United Kingdom, Wales is one of only 3 countries in the World which have a commitment to sustainability written into their constitution. It is now actively exploring how it might reduce its Carbon emissions as part of this remit. A Renewable Energy Route Map for Wales was published by the Welsh Assembly Government in 2008 [1] exploring how Renewable Energy systems might contribute towards this goal across all sectors of society.

Previous conference papers [2 — 4] have introduced the first findings from the project, looking at the operation of STACS systems and the Welsh Housing stock. This paper, along with other papers presented at the EUROSUN 2008 conference [5 — 7], complete the findings from this project to date.

This paper is in 3 sections:

• A short summary of the Welsh Housing stock showing the % of each type of house in Wales.

• A review of the modelling findings for the heating, cooling and DHW demands for each house type, with and without Thermal Energy Storage.

• A first assessment, based on the above sections, of the potential contribution that STACS might make to the annual heating, cooling and DHW demands in each type of housing, and hence the Carbon Emission reductions that might be achieved in the Welsh Housing sector as a whole.

Single float glass transmits the majority of solar radiation between 315 and 2500 nm and absorbs other wavelengths. In real-time situations non-perpendicular incidence angles of radiation, double or triple glazing, additional low-E coatings, glass coloring and layer of dust and dirt on the surface result in much lower transmission of solar radiation than declared. When taking into account dirt on glass in a city environment (e. g. correction factor 0.8) and solar incidence angle typical of temperate climates (e. g. correction factor 0.8), transmission of single glass for visible light decreases from 89% to 57%

(89 % x 0.8 x 0.8 = 57 %). To decrease thermal transmission of windows, double or triple glazing is used. U value of a double glazing with air filling is usually about 3.00 W/m2K. If the window system is improved by a low-E coating with Argon filling, U value drops to 1.16 W/m2K. However, lower U value also causes lower transmittance for the visual part of solar spectrum (tv = 78 %) and lower transmittance for the whole solar spectrum (g = 63 %). Further improvements of U values bring us to the use of triple glazing (double low-E coating and Argon filling (U = 0.60 W/m2K) of Krypton filling (U = 0.58 W/m2K)). As mentioned above, further lowering of U values cause even lower transmittance for solar radiation.

Students also discussed the concept of passive house in relation to inside environment quality and compared the passive and the bioclimatic concepts. The goal of the passive house is the reduction of heating energy use to less than 15 kWh/m2a. To reach this goal, glazing — which interests us most — has to be triple. This consequently reduces the dynamic communication between the inside and the outside environment. In the philosophy of the passive house design the reduced daylighting and cutting off the direct contact with external environment is viewed as collateral damage. But the concept of alienating people from natural environment is according to many studies harmful. The external environment is not hostile; on the contrary, it has simulative effects on body and mind. Daylight provides quality lighting, stimulates the sense of sight and is an important communication between the internal and external space [3]. Constant changes of light improve concentration and responsiveness. The same goes for hearing and the sense of smell. The bioclimatic concept, on the other hand, is based on simultaneous adaptation to external conditions and internal needs. The closer the building is able to follow these two profiles (temperature dynamics, solar and thermal radiation, relative humidity and air stratification), the more efficient it is. The unstable model represents the dynamic structure, which functions in real time. The goal of the above-described interventions in the framework of bioclimatic design is a healthy living and working environment with low energy use and not low energy use with physiological minimum.

Glazing properties have direct influence on the level of daylight in living and working environment and on energy balance of buildings. Low daylight levels have proven negative influences on comfort, health and efficiency of people as well as on energy used for lighting and cooling of spaces. Studies

carried out in the 70-ies in the USA showed possible energy savings for lighting of office spaces in the range between 15% and 20% if enough daylight was available (also regarding quality factors) [3]. Lately the advantages and positive effects of daylight on efficiency and sales increase were proven in the HGM study [4, 5] carried out in 2003. Of course, lower U value of glazing decreases transmission losses through the building envelope, but when designing non-transparent parts with U values 0.2 W/m2K or lower, the majority of heat losses are produced due to ventilation, not because of heat transmission. Because of the above-mentioned reasons and complex influences on the functioning of the entire building system, window properties are not a trivial question and deserve a systematic analysis.

C. Silvi

Gruppo per la storia dell’energia solare (GSES) — Via Nemorense, 18 — 00199 Rome, Italy

E-mail: csilvi@gses. it

Abstract

This poster presentation aims at introducing to the EuroSun 2008 participants the exhibition “Solar Cities From the Past to the Future: Scientific Discoveries and Technological Developments” opening in Rome in the spring of 2009. Now in its second edition, the first of which took place in 2006 at the Genoa Science Festival, the exhibition will be installed at two prestigious and symbolic venues, the Museum of Roman Civilization and the Central State Archive. In Genoa the message was: for thousands of years, and until just 200 years ago, human beings developed experience in building and operating cities run on solar energy alone. Can this experience be useful in designing the solar cities of the future? Is it possible to return to the use of the sun’s energy for lighting, heating and cooling buildings, for producing electricity, fuels, and construction materials for the cities of a technologically advanced world? The upcoming event in Rome will continue to explore these and other questions. Solar features of models of houses, baths, villas, preserved at The Museum of Roman Civilization, will be highlighted with the heliodon approach. The thesis that future or modern solar cities have their main roots essentially in the past will be reiterated.

1. Introduction

Renewable solar energy — what the sun sends us every day, the driving force of all forms of life on earth, of the winds and the water cycle, the growth of forests and other biomass — has always been, is and will always be the principal energy source on our planet.

All over the world, people used solar energy alone until barely 200 years ago, when fossil fuels — coal, oil and gas (actually fossilized forms of solar energy) — began to gain sway. Like nuclear fuel, these forms of energy are not renewable and eventually will be exhausted.

The use of renewable solar energy is thus an age-old experience marked by fundamental discoveries that made it possible to build cities that ran on solar energy alone, ranging from the discovery of fire, which enabled humans to use the solar energy stored in forest wood and other forms of biomass, to the discovery of agriculture and the birth of the first human settlements. The ancient Greeks’ discovery that streets and buildings can be oriented so as to exploit the sun’s light and heat directly and naturally gave birth to solar architecture. The Greeks’ idea was built upon by the Romans, as codified by Vitruvius in De Architectura, and handed down for centuries.

These discoveries characterize what I would call the primitive or ancient solar age. Though we take them for granted today, they are still of the greatest importance in our daily lives. It’s as if an ancient renewable-solar-energy soul were living on in the cities of our modern world, nearly forgotten and not accounted for

If our forbearers were able to build and run cities with renewable solar energy alone for thousands of years, is it not possible for us to do so in the future? This question was raised explicitly in the 1st edition of the exhibition “Solar Cities From the Past to the Future: Scientific Discoveries and Technological Developments” promoted and organized by the Italian Group for the History of Solar Energy (GSES), and the “Italian National Committee ‘The History of Solar Energy’” (CONASES), a multi disciplinary non profit entity established in 2006 by the Italian Ministry for Cultural Heritage and Activities. The exhibition was held during the Genoa Science Festival at the Doria Pamphilj Prince’s Palace from October 26 to November 7, 2006 [2][3].

The exhibition traced the evolution of the Italian human habitat from antiquity to the present day and with a look to the future. It recounted the changes in cities, architecture and energy and food — supply infrastructure, and the scientific discoveries and technological developments that marked the major stages in their history, for instance the Romans’ introduction of flat window glass 2000 years ago [1].

Visitors to the exhibition at the Prince’s Palace were able to explore solar city past, present and future with the aid of more than 40 posters, various videos, seminars and conferences. A brief video report of the exhibition is available on You Tube [4].

A city of modern or future solar age has its roots in the discoveries and inventions made during the Renaissance and the scientific revolution. One example of the progress made over the past five hundred years is the giant steps taken in the understanding how light works by great scientists such as Galileo, Leonardo, Newton, Huygens, Maxwell, Planck and Einstein. The explanation of the photoelectric effect by Einstein contributed to underscore other aspects of the structure of the atom, the nature of light and the electrical origin of the cohesive forces in molecules and matter. All this has opened fascinating prospects for the use of direct solar energy in the modern or future solar age, from solar cells with efficiency ratings of 50% or more to smart glass and photon solar architecture and city planning.

Will scientific discoveries and technological developments allow us to build the solar city of the future, a city powered solely by solar energy?

A thesis presented in Genoa by GSES and CONASES was that to bring the modem solar city into being we must intelligently combine and integrate the experience gained by the ancient cities — not only in terms of technical know-how, but also of art, culture, relations and communication — with the many solutions made available by the scientific discoveries and extraordinary technological developments of the past two hundred years, especially the most recent decades. In other words, as suggested by Norbert Lechner, “Use the best of the old and the best of the new.” [5]. This thesis will be reiterated in Rome’s exhibition.

Based on the results from the latest survey, it is estimated that 22.6% of the electric energy consumption of the residential sector is using an electric shower device (Figure 1) which instantaneously heats the water as it flows through it commonly called Instantaneous Electric Shower Device; in turn, this represents about 6% [7] of the electric energy consumption in the whole of Brazil (± 22 TWh).

The graph of the average residential load curve in Figure 2 reveals that it is at peak-hour_ normally between 06:00PM and 09:00PM_ that the use of electric shower as a water heating device is the most widely spread [1].

The value indicated in brackets in the key corresponds to the percentage in electric energy consumption for each domestic piece of equipment.

The load curve of the Brazilian Electrical System-BES, on a typical day, is shown in Figure 3 [11]. Fig. 2. Residential Average Load Curve (W) Fig. 3. Load Curve of the BES (MW)

These studies about the Ownership and the Utilization of Equipments (Pesquisa de Posse de Equipamentos e Habitos de Uso — PPH in Portuguese) coordinated by PROCEL/Eletrobras, are also meant at qualifying the type of ownership, using a customised questionary but with the same standards of measurement from other research institutes for relevant comparison. Through the careful analysis of the individual answers from end consumers regarding the use of their domestic equipments, it is possible to raise important data about living conditions and socio-economic information for example, as well as about the quality of the electric energy supply as a whole, market changes following the electric energy rationing of 2001, domestic appliances purchasing habits etc.

Table 1 shows a summary of the comparative data from the various surveys ran by PROCEL between 1988 and 2005 about instantaneous electric shower ownership in Brazil: it is clear that the number of households using this device increased over those 17 years.

In 2005, 42 % of all residencial electric showers were turned on between 06:00PM and 07:00PM causing the Brazilian Electrical System-BES to reach its maximum level in electric energy demand.

There was also a noticeable change of habits in the first hours of the day. Whilst in 1988, 10% of all households in the country had at least one person using this equipment between 06:00AM and 08:00AM, in 2005 this percentage had increased to 31%. (Figure 4).

According to Table 2, the Southern region not only has the highest index in electric shower use as well as the highest average ownership with 1.17 electric shower per household_ way above the national average of 0.89.

Futhermore, it appears that 21% of all interviewees, by 2005, had already switched electric shower devices for solar heating systems. A new demand is also emerging by means of the efforts of a few Brazilian municipalitiescouncils to integrate within their City Planning Directives the obligation, for all new buildings, to offer solar collectors installation facilities.

PROCEL has been focusing, with partner entities and enterprises, on promoting the technological development of equipments using solar energy for water heating.

Error! Reference source not found. shows the main dwelling types in Wales and the percentage of the total housing stock that each type occupies. It can be seen that the semi-detached house is by far the most common residential property type, accounting for 44% of the total housing stock, excluding year 2000 onwards properties. The data in bold type shows the building types modelled in this project. These models can be seen to represent around 50% of the total housing stock. A suitable Case Study of a pre-1919 terrace could not be found, but if we were to model this as well then 66% of the housing stock type would be covered.

No data for post-2000 dwellings

Rhodes et al [3] provides greater detail of the housing stock, including physical properties, improvements, etc., but it is clear that a large percentage of the housing stock was built before energy efficiency was a serious consideration.

From figure 1, taken from the Renewable Energy Route Map for Wales [1], we see that the domestic sector accounted for 23% of the total carbon emissions in Wales in 2003. The breakdown between electrical and thermal demand is not known.

For this paper the annual electrical demand for each of the dwellings is taken to be 3090 kWh [8].

At UL FGG KSKE two studies dealing with the influence of glazing properties on daylight levels and energy balance of a building were conducted. Our primary goal was to find out to what extend lower U value of windows influences daylight levels in buildings. In addition, we monitored energy balance of

buildings (transmission losses and solar gains) and compared benefits and deficiencies (can lower heating energy use compensate lower daylight levels).

In the first study [1] students collaborated in a joint comparative analysis carried out in the framework of seminars at two subjects: Building, Environment, Energy (UL FGG UNI — Construction course, 4th year) and Bioclimatic building (UL FGG VSS — Construction course, 3rd year) in academic year 2006/2007. The study comprised student-selected buildings for which the influence of changed glazing characteristics on internal environment and energy balance of buildings were calculated. The choice of buildings included a wide selection of types and geometries of buildings, from small residential houses, schools and larger public to office buildings (Fig. 1). Random selection of buildings (surface- to-volume ratios were among 0.10 and 1.00) covered current architectural production and ensured that the results were general enough to be statistically valid. For each of the 27 buildings students calculated yearly energy balance in a building (according to EN 832, all at the same location) and daylighting in a room of a chosen building (21. 3., 21.6., 21.9. and 21. 12. at 12:00 under standard CIE overcast sky) for two variants of commercially available window glazing:

1. double glazing, U = 1.40 W/m2K, g = 0.65, tv = 0.70

2. triple glazing, U = 0.60 W/m2K, g = 0.50, tv = 0.50

All the other input data remained the same (location, geometry of building, sizes of windows, U values of non-transparent parts, orientations, etc.). Daylighting calculations were carried out with a computer

tool SPOT1M v3.1 Sensor Placement + Optimization Tool. Heating energy demand according to EN 832 was calculated with computer tool GEnV 1.1.

In the case of 27 student-selected buildings, change of window glazing resulted in the average reduction of specific heating energy demand (Qn/Au) by 14.4%. At the same time the reduction of average illuminance level (Eav-eq) in rooms decreased by immense 25.3%. The reduction of the ratio of heating to daylight is almost 1:2 and is in some cases even higher. For instance, case P17-TS reached 0.7% reduction of heating energy demand and 29.2% reduction of daylight level in a chosen room. Similar result was obtained in case P19-TS where heating energy demand was reduced by 1.5% and the reduction of daylight was 27.8%. Only in three cases (P1-TS, P2-TS and P16-TS) the heating energy demand reduction was higher than the reduction of daylight levels in rooms (Fig. 2).

After students executed calculations of energy consumption and internal illuminance levels in their buildings for both types of selected glazing, they were expected to make a decision on the final configuration of their buildings external envelope in regards to their findings. In the end they had to make an argumented decision whether they were going to use triple or double glazing. In such a way students were encouraged to make an executive design decision on the basis of their own findings (executed calculations of energy demand for heating and internal illumination levels) and knowledge about building physics and internal environment that they accumulated during seminar course and lectures in their respective subjects. With such an approach to seminar work students are not just given information but are expected to use the tools and knowledge at their disposal to come up with the best solution for a certain case on the basis of their own experience. A valuable lesson for future civil engineers is learned — that interventions in one area of building design can influence other aspects of the building as well, and for optimal results a holistic approach is necessary.

Very similar results were obtained in an independent parallel study [2] carried out by the staff of KSKE. We studied a hypothetical single room object 4m x 6m x 2.5m with one south oriented window positioned on the shorter wall, for which we changed size and glazing characteristics. The window size varied from 14% (1/7 — K1 configuration) of floor area, 20% of floor area (K2 configuration), to 42% (glazing of entire wall — K3 configuration) of floor area. Two variants of window glazing characteristics were chosen:

1. double glazing, U = 1.12 W/m2K, g = 0.61, tv = 0.76

2. triple glazing, U = 0.74 W/m2K, g = 0.50, tv = 0.66

The U value of the non-transparent building envelope was U = 0.15 W/m2K. For easier comparison in both studies the same computer tools were used.

As expected, the analyses showed distinctly negative influence of triple glazing on daylighting of spaces compared to double glazing. Surprisingly, use of heating energy was minimally reduced when triple glazing was used. Energy balance of the K1 configuration with the smallest window opening (Az = 1/7 of floor area) was almost the same if double (Qn/Au = 68.33 kWh/m2a) or triple glazing (Qn/Au = 67.80 kWh/m2a) was used. The difference was only 0.78 %. At the same time the illuminance level (Eav) fell by 13.1 % when triple glazing was used. The reason for small differences of energy demand is the g factor and decreased solar gains (Qs), which are 18% lower when triple glazing is used, but the transmission losses (Qt) are reduced by only 9.2% (Fig. 3).

The actual values of heating demand reduction and illuminance levels deterioration differ compared to the first study, but the ratio between them is identical (when triple glazing is used, daylighting level is reduced by a factor 2 regarding heating energy demand). The results of both studies show a trend of extreme deterioration of daylighting in buildings and relatively small reduction of heating energy demand when triple glazing is used.

In the third configuration (K3 — window size is 42% of floor area) the size of glazing is 20% of the entire fa? ade area, which, compared to the first configuration, presents three times larger window area. As expected, transmission losses dramatically increase and double glazed configuration has 17.4% higher losses than the triple-glazed one. Regarding solar gains the situation is reversed; in the case of triple glazing the gains are 18.8% lower. In the context of the entire building heating energy demand is

by 7.0% higher when double glazing is used, but at the same time the average illuminance level is reduced by 14.6% (Fig. 4).

It is obvious that major part of heat losses originate from ventilation, when well insulated non­transparent envelope (U = 0.15 W/m2K) and quality glazing (U = 1.12 W/m2K, g = 0.61, tv = 0.76) are used. In the first configuration with double glazing 57 % of the entire heat losses belong to ventilation losses (Qv).

Reducing U value of glazing in buildings, which have 10% — 20% of glazed fa? ade area in the present state-of-art is not reasonable. The quantity of transmitted daylight disproportionally decreases compared to heating energy demand. Furthermore, the reduction of g and Tv factors has negative impact not only on solar gains and daylighting, but also on health and use of energy for electric lighting. Especially prolonged use of artificial lighting is the factor that additionally speaks in favor of window glazing with higher visual and solar transmittance.

2. Conclusion

Students collaborated in joint comparative analyses of the presented problem. They used 27 randomly selected buildings of various building types (small residential buildings, schools, and larger office buildings), geometries and configurations. For each building they calculated yearly daylighting under standard overcast CIE sky and heating energy consumption according to EN 832. The buildings were glazed with two variants of glazing systems (double glazing: U value 1.40 W/m2K, g = 0.65, tv = 0.70 and triple glazing: 0.60 W/m2K, g = 0.50, tv = 0.50). All other input data remained the same. The average of 27 buildings showed that by changing double-glazing for triple glazing heating demand of buildings reduced by 14.4%, but at the same time it deteriorated daylight levels in the reference rooms by dramatic 25.3% (Fig. 1). The proportions between the heating reduction and daylight levels were in some cases even more drastic and reached close to 50% of daylight reduction. Only in 3 cases the reduction of heating energy demand was larger than the reduction of daylight levels. A parallel analysis that was carried out independently, as an internal study at KSKE, showed similar results.

Both analyses showed the trend of drastic reduction of daylight levels in the reference rooms and at the same time small or even in some cases negligible improvement of the heating energy balance. The study showed that in moderate climate at the moment the technical maximum is double glazing with U value in the range of 1.1 W/m2K and transmissions about tv = 0.76 and g = 0.61. Both values are given for clean glass and perpendicular incidence angle. In reality we have to allow for correction factors and can expect even more evident differences. Daylight represents a very important element of wellbeing of users and directly influences the amount of electrical energy used for artificial lighting. At the same time lower g value reduces the possibility of solar heat gains. Considering the present characteristics of commercially available triple glazing we can justly ask ourselves, if wide use of such glazing can be justified.

References

[1] A. Krainer, M. Kosir, Z Kristl,. Analyses of glazing characteristics influence on internal environment in 27 randomly chosen buildings — partly realized by the students in the framework of the seminars Building — Environment-Energy (UL FGG UNI — construction, 4th year) and Bioclimatic buildings (UL FGG VSS — construction, 3rd year), UL FGG KSKE; 2007.

[2] A. Krainer, M. Kosir, Parametrical study of U value influence on daylghting and energy balance of a hypothetical one-space building — internal publication, UL FGG KSKE; 2007.

[3] A. Krainer, M. Kosir, Z. Kristl, M. Dovjak, Passive house versus bioclimatic house. Gradbeni vestnik letnik 57 (2008) 3, 58-68.

[4] L. Heschong, Windows and Classrooms: A Study of Student Performance and the Indoor Environment. Fair Oaks, Heschong Mahone Group. California Energy Commission, 2003.

[5] L. Heschong, Windows and Offices: A Study of Office Worker Performance and the Indoor Environment. Heschong Mahone Group. Fair Oaks, California Energy Commission, 2003.

The installation designed for Genoa has been completely revised for Rome, where there will be a much larger display space, longer opening time, site-specific models and documentation. In parallel to the exhibition, as in Genoa, a series of conferences, seminars, debates and shows will also be held. Details will be published in the fall.

2. The Exhibition at Museum of Roman Civilization

The Museum of the Roman Civilization is a unique venue for an exhibition on solar energy. The two sections, historical and thematic, present a synthesis of Rome’s history, from its origin to VI century B. C., and the various aspects of Roman expansion. It holds a large collection of reproductions and models that illustrate the history of the formation of the city of Rome and of the Empire, as well as the use of sun’s energy in hospitals, villas, baths, etc. [6][7].

The solar features of these buildings will be illustrated by the use of a heliodon, which will reproduce the sun’s path in various moments of the day as well as different seasons.

According to data from the Brazilian Association of Heating — ABRAVA in Portuguese [9], there was an increase in the sales of solar collectors in 2001 reaching 480,000 m2 _ way above the average of previous years. However, sales fell down in the following years to an average 350,000 m2 per year. Whereas countries like Austria and Greece attend up to 12% and 22% of their population respectively [10], with solar thermal energy, Brazil’s index doesn’t even reach 1%.

In order to understand better the current situation, it is important to take into consideration the high initial cost of installing solar systems in comparison to the much lower cost of acquiring an electric shower device in addition to how easy the latter is to install. These three factors represent a serious barrier to the growth of the solar energy market in Brazil.

As an example: a low-cost solar system, sold over the Internet [11] and made of PVC with only two solar collectors and a storage unit of 200 liters, has a price tag of about €400 excluding installation costs. The price tag of another equipment made of metals, subsequently offering better results, can reach double this value. In Brazil, one can easily buy an instantaneous electric shower device of 5,400 Watts for about €10 [12] with no extra installation cost as it is a quick and easy “Do It Yourself — DIY” job.

Another current barrier, is the absence, in some big Brazilian cities, of specialized companies or professionals to install the solar equipments as well as to maintain them.

The partial results of an on-going nationwide study, coordinated by PROCEL in partnership with Papal Catholic University-Minas Gerais (PUC-MG in Portuguese), point out the existence of a €40,000 solar water heating system for a gym’s swimming pool in a residential area of Rio de Janeiro which started causing problems ever since it was installed back in 2006. The company it was bought from still hasn’t been able to offer a practical solution for it to work properly and thus the use of the system was switched to a system using natural gas.

These examples indicate the delay of solar heating systems in penetrating the Brazilian market. Considering that 81.5% of all Brazilian households heat water to take showers, 90.8% of the time it is using electric energy while only 7.3% of the time it is using natural gas [4].

In 2000, as one of its main lines of action and within its solar energy heating dissemination strategy, PROCEL launched its awarding process of the PROCEL Energy Saving Seal (Figure 5) to solar collectors and thermal tanks in association with the National Institute of Norms, Measurements and Industrial Quality — INMETRO in Portuguese [13].

The purpose of PROCEL Seal is to stimulate the national production of more efficient equipments and domestic appliances giving consumers information and guidelines in order to buy more energy efficient equipments thus contributing towards technological development and the reduction of the environmental impact.

The PROCEL Seal is annually awarded to equipments with the most efficient indexes of energy efficiency, in its respective category, usually characterized with an “A” at the top of the National Energy Conservation Label — ENCE in Portuguese (Figure 6). Please note that for a couple of specific product categories, further technical and qualitative features are required of the equipments, to be checked and considered towards the awarding of the PROCEL Seal. (Example: the proven electrical safety of the equipment).

In order to be awarded the PROCEL Seal, the product is submitted to various technical tests run by impartial and competent labs indicated by PROCEL. The adhesion of the producing companies for labelling, to this day, is volunteered.

While at its beginning, the program counted only two participating product manufacturers, in 2007, 160 types of solar collectors were listed from 29 different manufacturers [13], representing more than 50% marketshare.

The PROCEL Seal has been awarded to solar collectors since 2000 thus contributing to the significant improvement of the performance of those currently available on the market.

Procel Seal Average ENCE

Fig. 7. Evolution of the average monthly production of specific energy from solar collectors

(kWh/month per m2)

Whilst the PROCEL Seal has been awarded to the thermal tanks of solar heating systems since 2002, these equipments have already been receiving the ENCE label since 2001. Until 2003 there were no difference in the criteria required for the awarding of the PROCEL Seal and the ENCE label. However, from that year onwards, distinctive indexes were established in relation to the specific loss of monthly energy for both of them, to be consistent with the PROCEL Seals indexes which are constantly upgraded.

Figure 8 shows the evolution of the specific loss of energy’s monthly average of 200 liters thermal tanks labelled between 2001 and 2007. The curve points out to the significant improvement of these equipments’ performance and available on the market over the years.

(kWh/month/liter)

In 2000, the university PUC-Minas Gerais and PROCEL, in partnership with the City Council of Contagem (Minas Gerais), took part in a project to install 100 solar water heating systems with a capacity of 200 liters each. This project was the largest of its kind in terms of the ratio scale/number of households, in Brazil. It also provided valuable data which allowed for the addition of solar heating systems on the list of electric energy utilities’energy efficiency projects thus meeting the National Agency of Electric Energy’s (ANEEL in Portuguese) legal requirements_ a compulsory investment of 0.5% of these companies’net income.

The Contagem’s Project corroborated an average reduction in electric energy consumption of up to 40%, depending on the type of heating systems installed, proportionate to savings of up to 60% in utility bills [14]. This project has demonstrated the financial viability of the use of solar heating systems for the lower-income population. Based on these results, the Electric Energy Distribution Utility of Minas Gerais (CEMIG in Portuguese) stimulated a number of this kind of projects which turned the state of Minas Gerais pioneer in the use of solar systems nationwide.

In 2005, PROCEL, in the context of PEE, acquired equipments to expand the technical capacity of the University PUC-MG’s Solar Laboratory which is responsible for testing solar collectors towards the ENCE and the PROCEL Seal labelling process. This technical expansion, thanks in particular to a solar simulator imported from Germany, allows for most of the tests to be ran indoors by the laboratory thus speeding up the overall process_ from a month to less that a week_ reducing the impact of the weather condition. This equipment is the first of its kind in the whole of Latin America out of 5 in existence in the whole world and it cost USD 500,000, donated by GEF (Figure 9).

In the same way, the Laboratory at the Technology Research Institute in Sao Paulo (IPT in Portuguese) benefited from PROCEL’s help in acquiring new equipments for tests on thermal tanks with the same positive effects.

There are various ongoing studies being carried out to demand the labelling of all solar collectors and thermal tanks with ENCE. However, to become compulsory, this process needs to clarify policies as well as to provide the minimum energy efficiency indexes to be indicated as established by the law #10.295 of 2001 [15], also known as “Energy Efficiency Law”. These initiatives will empower the sector to generate new mechanisms to further advance the quality of solar heating equipments.

In this context, the carrying out by PROCEL, in partnership with PUC-MG, of the studies mentioned earlier represent a new step since they are destined for the accurate assessment of solar heating systems’ installations found in Brazil today be it in: the residential sector (showers and swimming pools), the service sector (hotels, gyms and schools) or the industrial sector. Involving about 60 professionals such as university professors, researchers, consultants and scholarship holders from various large Brazilian cities such as Belo Horizonte, Rio de Janeiro, Porto Seguro, Brasilia, Campinas, the nationwide project’s main objective is to lay the strategic plan towards further technical development and dissemination of the solar energy in Brazil.

2. Conclusion

As the studies carried out by Eletrobras/PROCEL (PPH) have shown, the use of electricity is predominant for water heating amongst Brazilian households due to the overwhelming presence of electric showers as the device most commonly used for this purpose. The immediate consequence of this fact is reflected in the inflated demand during the electric system’s peak-hour.

It has been asserted that the consumption of electric energy for water heating in Brazil is overall considerably high and historical data is pointing out at an ongoing growth trend should no provision, whether political or technical, be made rapidly for this sector.

Thus, the use of solar energy for water heating in Brazil has huge growth potential since less than 1% of the population currently makes use of this type of energy. Taking these facts into consideration and notwithstanding the favorable climate in the country, with approximately 2,200 hours sunshine per year [10], one can assert that the most recommended alternative for this end use is to substitute the electric shower with alternative sources of energy such as solar energy. In this context, PROCEL has been achieving a series of carefully planned and controlled activities towards the dissemination and the stimulation in the use of solar heating systems in Brazil. These activites can count on the collaboration of significant business partners such as INMETRO, PUC — MG, IPT, ABRAVA as well as the Manufacturers’Association. These partnerships are essential to

reach the results sat through our objectives. One of PROCEL s main lines of action has been the structuring of the testing laboratories supporting ENCE and the PROCEL Seal’s labelling process.

Since the use of solar heating systems is not recommended in all regions nor all conditions, there are constant efforts made by manufacturers, laboratories and PROCEL itself not only to contribute to the overall improvement in the efficient consumption of electric energy, but also of water and electric safety in water heating electric equipments. Indeed, these equipments were amongst the first to be considered for labelling with ENCE. Despite all of these combined effortst and the results shown by the success of the projects already running, there is still a long way to go in order to encourage nationwide the expansion of the use of this water heating technology: one of the most important step is to add it in the financing program of popular housing.

Water heating solar equipments are currently being taken into consideration by the Ministry of Mines and Energy (MME) to be added to the existing energy efficiency law. This should be implemented as of the year 2009 which will represent a true landmark in the sector’s advances.

References

[1] PROGRAMA NACIONAL DE CONSERVACAO DE ENERGIA ELETRICA-PROCEL. Available at <http://www. eletrobras. com/procel.>.

[2] CENTRAIS ELETRICAS BRASILEIRAS-ELETROBRAS. Available at <http://www. eletrobras. com>.

[3] PROGRAMA NACIONAL DE CONSERVACAO DE ENERGIA ELETRICA. “Relatorio de Avaliagao de Resultados: Ano 2006”. Rio de Janeiro: Eletrobras, 2007. Available at: <http://www. procelinfo. com. br>. Accessed on: 15th of Dec. 2007.

[4] PROGRAMA NACIONAL DE CONSERVACAO DE ENERGIA ELETRICA. “Avaliagao do Mercado de Eficiencia Energetica no Brasil: Pesquisa de Posse de Equipamentos e Habitos de Uso da Classe Residencial no Ano Base 2005”. Available at: <http://www. procelinfo. com. br>. Accessed on: 15th of Sept. 2007.

[5] WORLD BANK. Available at <http://www. worldbank. org>. Project ID P039200. Accessed on: 17th of Sept. 2007.

[6] SOUZA, R. “Pesquisa de Mercado em Eficiencia Energetica”. Rio de Janeiro: Apresentagao dos Resultados, April 2007. Available at: <http://www. procelinfo. com. br>. Accessed on: 15th of Sept. 2007.

[7] EUROPEAN COMMISSION. “Market Study on Development of the Thermal Solar Market in Brazil”. Bruxelas: European Communities, 1999.

[8] OPERADOR NACIONAL DO SISTEMA ELETRICO (ONS). “Curva de Carga”. Available at: <http://www. ons. org. br>. Accessed on: 17th of Sept. 2007.

[9] FARIA, C. ABRAVA. “Aquecimento Solar”. Rio de Janeiro: Palestra na Camara de Vereadores do Rio de Janeiro, December 2006.

[10] RODRIGUES, D.; MATAJS, R. “Um banho de sol para o Brasil: o que os aquecedores solares podem fazer para o meio ambiente e a sociedade”. Sao Paulo: Vitae Civilis, 2005.

[11] LOJAS AMERICANAS. Available at: <http://www. americanas. com. br>. Accessed on: 24th of Oct. 2008.

[12] CASA & VIDEO. Available at: <http://www. casaevideo. com. br>. Accessed on: 24th of Oct. 2008.

[13] INMETRO. “Tabelas de Consumo de Energia Eletrica”. Available at: <http://www. inmetro. gov. br >. Accessed on: 17th of Sept. 2007.

[14] PEREIRA, E. “Aquecimento Solar de Agua para fins sanitarios”. Rio de Janeiro: Palestra na Camara de Vereadores do Rio de Janeiro, December 2006.

[15] AGENCIA NACIONAL DE ENERGIA ELETRICA-ANEEL. Available at <http://www. aneel. gov. br>. Accessed on: 17th of Sept. 2007.

Computer Thermal Modelling using TRNSYS [9] and ECOTECT [10] software programmes provided an estimate of the thermal demands in the dwelling types modelled, as well as the potential carbon savings achievable through changing the heating, cooling and DHW demands from being primarily met by natural gas to primarily met by Solar Thermal. An existing dwelling was chosen to be representative for each of the housing types highlighted in Error! Reference source not found. and was then physically surveyed in detail [3]. Each dwelling was then modelled in ECOTECT before exporting the physical details into the TRNSYS simulation software to undertaken the energy demand assessments.

Only 12 out of the 13 housing types have been modelled to date — the most recent house type has not yet been modelled. The ECOTECT model for the largest dwelling, house 3, is shown in figure 2 as an example of the modelling undertaken. This image shows how the Solar Thermal collectors have been arranged for this property for the purposes of assessing the potential solar yield.

Table 2. Predicted annual energy demands for electricity, space heating, space cooling and domestic hot water

It can be seen that the dwellings thermal demand generally reduces per m2 as their construction date gets closer to the present day. It can also be seen that the internal gains from electricity use also become more important in the overall energy balance as the houses become newer. There are anomalies as would be expected from Case Studies — in particular House 1 which is explained by it being a very energy efficient refurbishment. Interestingly, this house compares very favourably with House 11 built to 2000 regulations, showing the potential for bringing old housing stock back into use.