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Architectural integration is a major issue in the development and spreading of solar thermal technologies. Yet the architectural quality of most existing building integrated solar thermal systems (BIST) is quite poor, which often discourages potential new users. In this paper, the results of a large web survey on architectural quality, addressed to more than 170 European architects and other building professionals are presented and commented. Integration criteria and design guidelines established and confirmed through the analysis of these results are proposed. Subsequently, a novel methodology to design future solar thermal collectors systems suited to building integration is described, showing a new range of design possibilities. The methodology focuses on the essential teamwork between architects and engineers to ensure both energy efficiency and architectural integrability, while playing with the formal characteristics of the collectors (size, shape, colour, etc.). Finally a practical example of such a design process conducted within the European project SOLABS is given; the resulting collector is described, and integration simulations are presented.
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Solar Energy
journal homepage: www.elsevier.com/locate/solener
Criteria and policies to master the visual impact of solar systems in urban
environments: The LESO-QSV method
Maria Cristina Munari Probst, Christian Roecker
Laboratoire d’Energie Solaire (LESO), Ecole Polytechnique Fédérale de Lausanne(EPFL), Switzerland
ARTICLE INFO
Keywords:
Urban acceptability
Solar policies
Architectural integration quality
Visual impact
Solar map
Criticity
ABSTRACT
Increased use of solar collectors in buildings is necessary but poses major challenges in existing built environ-
ments, especially where architectural quality is an issue. The large size of solar systems at the building scale
requires careful planning, as they may easily end up compromising the aesthetics of buildings, threatening the
identity of entire contexts. A new method named LESO-QSV(for Laboratoire d’Energie SOlaire – Qualité-
Sensibilité-Visibilité) has been developed to help authorities promote solar energy use while preserving the
quality of pre-existing urban areas. The vision underlining the approach is that solar integration is possible also
in delicate contexts, if appropriate design efforts and adequate cost investments are made. The issue is then no
longer to be in favour or against the use of solar systems in cities, but rather to define appropriate local levels of
integration quality, and to identify the factors needed to initiate smart solar energy policies able to preserve the
quality of pre-existing urban contexts while promoting solar energy use.
The LESO-QSV method helps tackle these issues with clear and objective proposals:
First it clarifies the notion of architectural integration quality and proposes a simple evaluation method, based
on a set of criteria derived from pre-existing literature.
Then it helps authorities set and implement local acceptability requirements, introducing the notion of ar-
chitectural “criticity” of city surfaces (LESO-QSV acceptability). The concept of “criticity”, at the basis of the
whole approach, is defined by the Sensitivity of the urban context where the solar system is planned, combined
with its Visibility (close and remote) from the public domain. The more sensitive the urban area and the more
visible the system (high “criticity”), the higher the need for integration quality. In practice, authorities will be in
charge to set the desired integration quality levels for each of the defined “criticity” situations, considering local
specificities (energy context, available energy sources, political and social considerations, city identity and to-
pography, among others). To help authorities set these quality expectations, the software LESO-QSV Grid has
been developed. It illustrates the acceptance impact of pre-defined sets of quality requirements, using a large
number of integration examples (150 emblematic cases). These detailed examples are provided to show au-
thorities how to objectively evaluate integration quality, but they also constitute a large set of learning examples,
good and bad, for architects, installers and building owners.
Finally the method proposes a way to tailor solar energy policies to local urban specificities by mapping the
architectural “criticity” of city buildings surfaces, and crossing this information with a city solar irradiation map
(LESO-QSV crossmapping), hence completing the characterization of the building surfaces with the potentially
required effort of integration.
1. Introduction
In the last decade global warming has become a major concern for
the community, leading political authorities to take increasingly drastic
actions in order to achieve energy savings and encourage the use of
renewable energy sources. In the built environment these new concerns
have led to the introduction of strict energy standards whose
requirements continue to rise.
In Switzerland, many standards and regulations have been estab-
lished, both voluntary (Minergie, Minergie P, Eco, A) and mandatory
(SIA 380/1), clearly indicating a trend towards a zero energy balance of
buildings.
In Europe, the framework is equally strict. A recent directive of the
European Parliament rules that from 2020 onwards, each and every
https://doi.org/10.1016/j.solener.2019.03.031
Received 21 September 2018; Received in revised form 26 February 2019; Accepted 10 March 2019
Corresponding author at: Laboratoire d’Energie Solaire EPFL, Station 18, 1015 Lausanne, Switzerland.
E-mail address: christian.roecker@epfl.ch (C. Roecker).
Solar Energy 184 (2019) 672–687
Available online 17 April 2019
0038-092X/ © 2019 Published by Elsevier Ltd on behalf of International Solar Energy Society.
T
new building will have to meet the requirements of the NZEB standard
(Nearly Zero Energy Building). For public buildings these requirements
will have to be fulfilled starting January 2019. As stated by the
Commission, “Nearly zero-energy buildings need to have very high
energy performance”, and “The low amount of energy that these
buildings require has to come mostly from renewable sources”.
(Directive 2010/31/EU European Union Parliament).
In order to meet these new standards, it will no longer suffice to cut
heating needs through an effective insulation of the envelope – it will
also be necessary to plan and enforce new, long-lasting strategies for the
production of operational power.
Its abundant availability and flexible use makes solar energy natu-
rally one of the resources that we will turn to in priority (Fig. 1, left).
A combination of passive and active solar energy is in fact able to
meet the various energy requirements of buildings in an effective and
economically sustainable way (Fig. 1, right):
– appropriate daylighting strategies are able to decrease artificial
lighting needs to a minimum;
passive collection of solar energy through windows can cover a very
large part of heating needs;
– solar thermal collectors are an excellent solution to produce hot
water, for domestic use and space heating.
– photovoltaic modules can provide the power for household appli-
ances and lighting, and can also operate a heat pump.
Clearly though, a consistent implementation of all these strategies
will not be possible without a global architectural reflection. On the one
hand, the position and size of openings play an essential part in lighting
and passive heating strategies; on the other hand, the size of active solar
systems is such that these systems have a major impact on building
appearance (Dessi, 2013). As much as new insulation requirements
have changed the way the materiality and language of the envelope are
conceived, the use of solar technology will have a radical influence on
the layout of buildings’ exposed surfaces. Without the skills needed to
integrate these new elements in a consistent design, the result will fail
to be satisfactory from an architectural point of view.
2. Energy versus architecture?
The new energy regulations and mandatory solar fractions for
electricity and domestic hot water are introducing new materialities
and geometries in buildings, which are leading to new forms of archi-
tectural expression that will slowly modify our city landscapes. NZEB
designers most often choose a compact geometry (optimizing the heated
volume/envelope losses ratio) and then need to artificially expand the
envelope surface to intercept a higher amount of solar radiation and
convert it through dedicated solar devices into electricity or heat
(Fig. 2).
This increased use of active solar collectors in buildings is clearly
necessary and welcome, but brings major challenges, especially in al-
ready existing built environments. The large size of solar systems at the
building scale asks for thoughtful planning, as these systems may end
up compromising the quality of the building, threatening the identity of
entire contexts (Fig. 3).
Accepting to sacrifice architectural quality to promote solar spread
can be very counterproductive, leading right to the opposite effect in
the long term. Animated discussions are already ongoing in most cities
between “solar pros” on one side, concerned by the urgency of max-
imizing renewable energy use and asking for total freedom to install,
Fig. 1. Left: Building energy evolution (Switzerland); Right: Available solar technologies in relation to the different energy needs.
Fig. 2. New Solar Buildings (left: 3M office building, Milan, M.Cucinella; right: Endesa pavilion, IAAC, Barcelona).
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
673
and architects and building heritage institutions on the other side, ex-
pressing their worries about the urban impact of such systems and
asking for a restriction of their use to certain urban contexts only.
3. The LESO-QSV mediation solution
De facto, both concerns of maximizing solar energy spread and
protecting the architectural quality of the built environment are justi-
fied, and both should possibly be satisfied at the same time.
This is even more true when considering that good architectural in-
tegrations can often be possible even in very critical contexts, under the
condition that appropriate design and cost investments are made
(Fig. 4).
Starting from these considerations, and convinced that the devel-
opment of solar energy in cities is one of the prominent challenges of
the near future, we looked for an “inclusive“ solution adressing Energy
and Architecture.
As the issue is then no longer to be in favour or against the use of
solar energy systems in cities, we propose to define minimal local levels
of integration quality, and to identify the factors needed to establish
smart solar energy policies able to preserve the quality of pre-existing
urban contexts while allowing solar energy use.
The LESO-QSV(Quality-Sensitivity-Visibility) approach (Munari
Probst and Roecker, 2011,2015) gives clear and objective answers in
this debate:
(a) First it introduces the innovative notion of “Architectural criticity“
of city surfaces, in relation to their need for integration quality (see
Section 4).
(b) Then it clarifies the notion of “Architectural integration quality”,
proposing a simple and objective evaluation method (see Section
5);
(c) Based on a) and b) it helps authorities set and implement precise
“Local acceptability requirements” (“LESO-QSV acceptability”, see
Section 6);
(d) d) Finally it proposes a way to tailor “Solar energy promotion po-
licies” to local urban specificities by combining architectural “cri-
ticity“ and solar irradiation information (”LESO-QSV-crossmapping“,
Fig. 3. Solar renovation at Schloss Walbeck-Castel, Germany (XVIII century).
Fig. 4. Photovoltaic system integrated on the roof of Aula Pierluigi Nervi, Vatican.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
674
see Section 7).
4. Architectural “criticity” of city surfaces
Good integration quality is always desirable, but not always crucial,
or even necessary. To facilitate the spread of solar energy, expectations
toward integration quality may be reduced where the perceived impact
of the installed system on the urban quality is lower.
In order to structure this idea, the new concept of “criticity” of city
surfaces is introduced, which is at the basis of the whole LESO-QSV
approach. The “criticity” of a surface defines the impact that mod-
ifications on that surface can have on the perceived global quality of the
context.
Two main factors are defining the criticity of city surfaces: the ar-
chitectural sensitivity of the building/urban context of the surface lo-
cation, and the visibility of that surface from the public domain.
4.1. System visibility
The visibility of the surface from the public domain is one of the two
factors influencing criticity. The higher the visibility of the surface from
the public domain, the more important its impact on the perceived
context identity. As for the context sensitivity, visibility is articulated
into three levels High,Medium and Low. The visibility has two compo-
nents: visibility from close range (close visibility) and from far away
(remote visibility) (Figs. 5 and 6).
For the first one, the determining elements will be the geometry of
the buildings and of the public space, while the second will be influ-
enced by the topography of the city and its surroundings.
A detailed description of the practical ways to assess the visibility of
city surfaces and the impact various city configurations have on this
factor is given in Appendix A.An automatized geometric calculation
tool is also under development at Ecole Polytechnique Fédérale de
Lausanne (EPFL). The first promising results are presented in a PhD
thesis just completed at EPFL (Florio, 2018).
4.2 Context sensitivity
The pre-existing quality of an urban context/building clearly in-
fluences the level of quality we can expect an integration to fulfil. If the
pre-existing context has no clear identity, nor other specific
architectural qualities, it is not pertinent to ask for a perfectly designed
and integrated solar system. By contrast, it seems very important to
push for integration quality in valuable areas or buildings.
To practically structure the issue, the QSV method proposes to
classify the sensitivities of existing contexts into 3 categories:
High sensitivity (heritage protected or meaningful contexs/build-
ings);
Medium sensitivity (contexts/buildings with no specific archi-
tectural/urban qualities, but with a meaningful identity for the
community, like most post world war residential or tertiary urban
developments);
Low sensitivity (contexts with poor urban/architectural qualities,
and no specific identity, like many recent industrial/commercial
urban developments) (Fig. 7a–c)
This categorization is meant to be coherent and coordinated (even if
simplified), with both the city zoning defined in the building regulation
codes, and the official categorization of protected areas and buildings
released by national and regional Heritage commissions (Fig. 7d).
In a situation of rehabilitation or new affectation of a neighborhood
the sensibility categorisation should clearly refer to the projected quality
level planned by the authorities, and not to the present status.
4.3. Derived “criticity” matrix
To structure the issue of architectural criticity of city surfaces and
related needs for integration quality, a matrix,called “criticity grid”, is
established by crossing the three identified levels of visibility (low-
medium-high, Figs. 5 and 6) with the three identified levels of sensi-
tivity (low-medium-high, Fig. 7), defining nine different criticity si-
tuations for which quality expectations will have to be set (cf. chap. 6).
As shown in Fig. 8, the matrix displays a “criticity gradient” of in-
creasing sensitivity, from the top left corner to the bottom right.
5. Assessing architectural integration quality
Requesting a certain level of integration quality implies being able
to assess quality. Often this is considered a matter of personal taste, but
recent studies have confirmed the existence of implicit criteria shared
by the architects community and actually leading architectural
Fig. 5. Visibility of city surfaces from the public domain.
Fig. 6. Remote visibility is influenced by city topography.
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integration quality perception (Krippner and Herzog, 2000; Munari
Probst, 2008; Munari Probst and Roecker, 2012).
To be perceived as integrated, the system has to be designed as an
integral part of the building architecture. This means that all the formal
(i.e. visual) characteristics of the solar energy system, have to be co-
herent with the global building design logic (Munari Probst, 2008):
collectors field size and position
visible materials
surface textures
colours
modules shape/size
jointing system
Identifying these key characteristics opens the way to an objective
evaluation procedure.
5.1. Evaluation procedure
Based on these findings the LESO-QSV approach proposes a sim-
plified qualitative assessment method, grouping the above described
integration characteristics into three global sets of characteristics,
leading to three integration criteria. This makes the procedure lighter
while keeping the evaluation as objective as possible (Fig. 9).
The quality evaluation consists then in assessing separately the level
of coherence of the three sets of characteristics with the global building
logic – coherence of the System Geometry, the System Materiality and the
Modular Pattern - using a three-level scale (fully coherent - partly co-
herent – not coherent).
This allows to concentrate sequentially on the specific character-
istics of the integration while evaluating their level of coherence:
– First the system geometry is evaluated, considering the size of the
collectors field, its shape and its position in relation to the building.
– Second, the coherence of the system materiality is evaluated, con-
sidering mainly the colour, texture and reflexivity of the modules.
Finally, the pattern formed by the juxtaposition of modules and their
jointing system is considered, to rate the coherency of the modular
pattern.
(In the cases where the most critical visibility situation is the remote
visibility (§ 4.1, Fig. 6) this last criteria can often be validated as fully
coherent, as the modular pattern is no longer perceived from afar.)
This being a global qualitative evaluation, the partial results cannot
be expressed by numbers and cannot be synthesized in a single mean
value; hence the choice to represent each partial evaluation as a co-
loured arc of a circle (green, yellow or red, according to the level of
coherency) to be combined with the others to form a complete three
sectors circle expressing the global system quality (Fig. 9).
Fig. 8. Criticity matrix and gradient.
Fig. 7. (a, b, c) different degrees of sensitivity of existing urban context – (d) Swiss ISOS offcial mapping of heritage protected enclosure.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
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5.2. Criteria evaluation examples
The following examples show the system evaluation principles ap-
plied to existing cases, demonstrating the idea of separate evaluations
for each of the three global criteria (see Figs. 10,11 and 12).
partly coherent not coherent
Fig. 10. Different levels of “System geometry” coherency.
Fig. 9. Integration quality evaluation method: criteria grouping – sectors evaluations– resulting quality circle.
partly coherent not coherent
Fig. 11. Different levels of “System materiality” coherency.
partly coherent not coherent
Fig. 12. Different levels of “Modular pattern” coherency.
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Fig. 13. Continous vs discrete scale evaluation: explaining apparent discrepancies.
Fig. 14. Discrete vs continous evaluation scale and examples of cross evaluations by MAS students in Architecture.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
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5.3. Evaluation scale, discrete vs continuous
Proposing only three discrete values for qualifying the integration
has the major advantage of greatly simplifying the tool, but it somehow
reduces the possibilties of nuancing the appreciation.
To evaluate the impact of this simplification a continuous scale has
been proposed to take this aspect into consideration (Fig. 13). This al-
lows to evaluate the integration using the continous scale and to then
read the result considering the three coloured “zones”, giving the dis-
cretized evaluation score.
The continous scale helps evaluators set the discrete values, and can
also explain why two expert’s evaluations, once discretized, can slightly
differ on particular cases.
The closer the “linear” evaluations are to a limit, the higher the risk
of getting different discretized appreciations. For example, the closer a
green evaluation is to the yellow zone for an expert, the higher the
chances of getting different results (green or yellow) when the case is
analysed by a different person (Fig. 13 System materiality). The ap-
proach was effective, as shown in the validation section below.
5.4. Validation
To validate the process of quality evaluation, the approach has been
tested in several academic courses and seminars dedicated to solar in-
tegration and has been used as teaching material (Munari Probst and
Roecker, 2009;Munari Probst, 2015a,b).
Participants were asked to individually evaluate integration cases,
placing coloured stickers on the linear scales. As shown in the examples
in Fig. 14, while not totally uniform, the participant’s evaluations
showed a very good general coherency, well validating the approach. A
relatively low spread due to subjectivity and to the qualitative character
of the evaluation process still does exist, but it indicates rather a
variability in the intensity than a fundamental difference in perception.
This procedure can be very useful when operating within specialized
commissions having to find a consensus over the evaluation of delicate
situations/objects.
Altogether this shows that the method can be considered reliable,
and the discretization into a three-value scales a satisfactory practical
choice.
A complete “case description and evaluation” sheet has also been
developed, which uses the adapted version of the continuous-discrete
evaluation scale (Section 6.2,Fig. 17).
These sheets are used within the Grid Software (Chapt. 6.1) and for
education purposes (Chapt. 6.2)
6. “LESO-QSV Acceptability”
With a reliable method to evaluate integration quality finally
available, quality expectations can be set for each criticity situation (see
Chapter 4).
However, the quality level to be required for each criticity situation
of the matrix is neither absolute nor constant, but depends on many
local and temporal factors, such as city identity and image, energy
context, availability of other renewable energy sources, quality and
availability of market products for good integration solutions, political
orientation, economic structure, etc.
For this reason the method does not provide one set of absolute
quality requirements, but offers flexibility.
A specific tool, the LESO-QSV GRID software (§6.1) is provided to
support authorities in establishing their own grid of local quality ex-
pectations, which will be more or less severe depending on the local
reality. Three predifined grids, of different “severity levels” are pro-
posed (Fig. 15), and the application provides the possibility to elaborate
acustom grid, to adress specific situations.
Note that in the acceptability phase, as only the number of sectors of
each colour is relevant, no specific position in the circle is attributed to each
criterion.
Fig. 15. Different possible levels of severity for the acceptability grid (from left to right : standard, permissive, demanding).
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
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6.1. LESO-QSV GRID software
To help authorities set these requirements, a multi-purpose software
simulation tool has been developed, called LESO-QSV GRID (Fig. 16).
Quality expectations are represented by the same three circle-sector
symbols used for the evaluation of the integration quality described in
Section 5. Three “standard” sets of quality requirements with gradual
severity (demanding - standard – permissive, Figs. 15 and 16/1) are
available for authorities to choose from, together with the additional
option of setting a fully customized grid. As can be seen in the ex-
amples, most propsed grids will have a “severity gradient” matching
somehow the criticity gradient.
To help authorities choose the most appropriate “acceptability
grid”, a large selection of integration cases is displayed (Fig. 16/3) that
shows in real time which integration approaches would be accepted and
which ones would have to be rejected with the selected settings. The
examples database can be scrolled through, showing the effect of the
acceptability grid over a very extensive set (more then 150 real cases)
of integration approaches and criticity situations.
The same software is intended to be used, with minor adaptations,
also as an education tool for architects, authorities, installers and
building owners. The wide palette of examples provides inspiration
from good examples, shows errors to be avoided or gives ideas on how
to improve the quality of a project which would be rejected in its
present state.
It can also help municipalities explain in an interactive and visually
convincing way how the method works and justify to users possible
project rejections.
Selection buttons are available in the bottom part of the screen to
display a chosen subset of integration examples in selected situations
(system visibility/context sensibility/integration quality level…)
(Fig. 16/5)
1
2
4
5
6
3
Fig. 16. Main screen of the LESO-QSV GRID program : 1 – Acceptability grid of the specific city: i.e. required integration quality for each criticity level f (system
visibility; context sensitivity). These are the criteria to be met for the installation to be accepted; 2 – Acceptability grid setting bar (for Municipality use only):
integration requirements can be selected by using pre-established grids (more or less severe), or built to measure; 3 – Integration examples showcase: a database of
more than 150 cases is shown according to a selected filter setting (5). This showcase is meant to: help Municipalities set an appropriate acceptability grid by showing
the impact in acceptancy of pre-defined sets of quality requirements; present a model for authorities of how to objectively evaluate integration quality; inspire
architects, installers, building owners… ; 4 – Case details window: The window appears while clicking on a specific case. The detailed evaluation of quality becomes
visible, together with other more precise information and additional pictures of the case; 5 – Filter bar: The case studies can be filtered according to solar system type,
position, dimension, context sensitivity, system visibility, integration quality; 6 – Accepted/not accepted cases button filter.
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6.2. Educational use of the LESO-QSV GRID database
To better valorize the education potential of the database, more
then 150 cases can be accessed and downloaded as separate case sheets
classifying and describing in some detail each installation example and
using both the discrete and the continous evaluation scale (Fig. 17).
These cases were collected with the help of the the students of different
courses at EPFL and at IUAV (Venice) who were asked to collect existing
solar integration examples and use the sheets as learning material to classify
and analyse each case (more than 500 examples were collected in three
years of teaching in three different courses on the topic of Architecture and
Solar energy (Munari Probst and Roecker, 2009).
The proposed selection is meant to give a significant and compre-
hensive outlook of the different approches available today to integrate
active solar strategies in buildings. New, existing and historical build-
ings are equally represented with respectively 50, 62, and 44 cases
each. For each category, different integration approches, solar products,
integration qualities and criticity situations are proposed, all together
Fig. 17. Case study description and evaluation sheet example, with continuous evaluation scales and final discretization.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
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informing extensively on the state of the art of the topic.
The cases can then be used as unique education material, providing
at the same time a collection of integration references and a set of
educated evaluations.
The integration examples, good and bad, inform students, architects
and building owners on present possibilities and limits in terms of
products and technologies, within various architectural contexts.
To ease its use, the complete collection can be sorted according to
various criteria of interest: building type; system size (small, medium,
large), system position (roof or façade), solar technology (PV, solar
thermal, hybrid), integration approach (basic to enhanced); etc.
6.3. Implementing the LESO-QSV method locally
As the main goal of the method is to help Municipalities manage the
impact of active solar systems locally, all the needed practical elements
to handle the acceptability have been prepared in the form of a “user
kit”. This kit includes a method implementation manual, a quality
evaluation manual, the described GRID software and the set of example
sheets. A customized “Application form” for approbation/rejection of
new installations is also produced, using the “severity grid” established
by the local authorities (Fig. 18).
Once an application form is filled by a citizen for a proposed
installation, the local QSV commission can accept or refuse it, using the
detailed quality evaluation to explain which aspect of the system needs
to be improved in case of refusal, possibly allowing to correct the
proposed system.
7. LESO-QSV “Crossmapping” tool
While the above described tools are reactive, and meant mainly for
context protection and users education, another tool derived from the
QSV criticity concept, called “LESO-QSV Crossmapping”, is conceived
as proactive and meant for energy policy planning.
Presently, the only information available to planners and authorities
to make decisions on solar policies (promotion, regulations, financial
incentives, among others) is the amount of solar energy received by the
various city surfaces, usually displayed on solar maps (GIS). These maps
vary in accuracy and detail levels but their only goal is to assess the
gross solar irradiation potential of city surfaces, without concern for
their urban specificities. As shown in Fig. 19, these integration related
specificities do have a major impact on solar application real potential
and should therefore also be made available to planners. To cover this
need, the “LESO QSV-Crossmapping” tool proposes to map the archi-
tectural criticity of city surfaces, as defined in Section 4, and to su-
perimpose this information over the available GIS solar irradiation
Fig. 18. Proposal of application form.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
682
map. This allows to weight the pure irradiation potential of each sur-
face with the expected architectural integration effort needed to collect
it.
Differentiated policies and educated decisions can then be based on
this more comprehensive information, keeping in mind that solar in-
tegrations are possible also in delicate situations (Fig. 4). In these cases
though, design efforts and cost investments will probably be higher. If
extra efforts cannot be afforded, it might be preferable to postpone the
operation, as poor integrations usually end up just discouraging new
users. By contrast, if well designed, such examples can be among the
strongest driving forces for the solar change, repaying by far their extra
cost.
7.1. Next steps
The criticity map mentioned above indicates for each city surface its
visibility from the public domain, and its sensitivity in relation to the
urban context. A process to automatically establish the visibility of the
surfaces in the 3D models of cities is currently being developed at the
EPFL LESO-PB Laboratory, as part of a PhD thesis (Florio, 2018). The
information related to surface visibility should not only consider the
purely physical visibility from the public domain, but should also take
into account the hierarchy of the different points of view in relation to
their importance for the perceived city identity (the view from a major
city square being usually more crucial than the one from a secondary
parking lot).
Possible crossed graphic representations of insolation and criticity
are currently under development in the Laboratory.
8. Conclusion
As more and more pressure is building up to increase the use of solar
energy as a replacement for fossil energies, there is an urgent need for
new responsible ways to implement the solar collecting elements in
urban contexts.
We have presented a new method able to concile the spread of ac-
tive solar solar systems in buildings with the protection of existing
urban environments. The method is based on the novel concept of city
surfaces criticity, as a function of visibility from the public domain and
architectural sensitivity of urban environments. Criticity is used to set
the quality expectations for solar integrations in the different situations.
The needed objective integration criteria have been defined and a
simple qualitative evaluation method proposed.
A software program has been produced to assist municipalities in
the practical application of the method. The program with its 150
commented integration cases will also serve as education tool for stu-
dents, architects and the general public.
Finally, a new element for urban solar planning is introduced by
combining criticity of city surfaces with their irradiation potential and
finally establish smart solar promotion strategies.
We strongly believe that the concepts of urban criticity” and ar-
chitectural integration quality at the basis of the LESO-QSV method offer
practical means to implement such responsible policies. We do hope
that all together the inferred tools will contribute to the elaboration of
valuable solutions to the problematic “Solar Energy Promotion and
Urban Context Protection” equation.
The method has been used within the recent works of IEA SHC Task
51 “Solar Energy in Urban Planning” (IEA SHCP Task 51 2018;Munari
Fig. 19. LESO QSV Crossmapping tool (roof irradiation data from http://www.uvek-gis.admin.ch/BFE/Sonnendach?lang=fr; Sensitivity plan from ISOS: http://
data.geo.admin.ch/ch.bakbundesinventar-schuetzenswerte-ortsbilder/PDF/ISOS_4397.pdf.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
683
Probst and Roecker, 2016) as a basis to assess the quality and accept-
ability of the different solar integration approaches proposed by the set
of case studies collected within Subtask C, and as core resources in three
courses currently taught at EPFL (Ecole Polytechnique Fédérale de
Lausanne, Switzerland) and University IUAV in Venice (Italy).
In November 2016 the method was rewarded by the Innovator of
the Year Prize rets Framtidsbyggare in Sweden (Prize rets
Framtidsbyggare, 2016), and recently the city of Malmö in Sweden and
the village of Valangin in Switzerland have shown a strong interest to
implement it as a pilot project.
A professional supporting structure to help municipalities and
heritage preservation commissions implement the method is currently
under finalisation with the support of the innovation transfer programs
Enable and Innoseed of EPFL.
Acknowledgments
This work was financially supported by :
– The Swiss Federal Office for Energy(OFEN)
– The Swiss Federal Institute of Technology of Lausanne(EPFL).
– The Innoseed Incentive Program at ENAC/EPFL.
– The Enable Technology Transfer Program at EPFL.
The authors wish to thank herewith the following persons :
– Laurent Deschamps, Paul Becquelin, Sebastien Hausamann and
Julien Grandin for their support in developing the software LESO-QSV
GRID.
– Barbara Smith for revising and proofreading the english.
– Ariane Delahaye for her support in developing the graphic layout
of the software and the example sheets.
– Professor Maria Wall for supporting the method and promoting its
diffusion.
– André Catana from the Technology Transfer Office at EPFL for his
continuous support.
– All the Innoseed commission members at EPFL.
Appendix A. Assessing visibility levels in standard urban situations
As presented in the main text, the visibility has two components: visibility from close range (close visibility) and from far away (remote visibility)
(Section 4.1 Figs. 5 and 6).
While the second will be influenced by the topography of the city and its surroundings, for the first one, the determining elements are the
geometry of the buildings and of the public space. It is therefore possible to pre-estimate the visibility levels for the most paradigmatic city
configurations.
A first simplified estimation of the impact of city geometry has been done by calculating the variablity of the surface vision angle (β) according to
viewer distance, building height and roof tilting (Fig. A1).
The table below (Fig. A2) shows the values both of β (degrees) and of the actual visibilty reduction (% of viewed surface) for different relevant
city situations:
– Various roof types : flat roof - roof tilting at 25°- roof tilting at 40°- roof tilting at 60°
– Various building heights; from 1 to 6 floors (most buildings higher than 6 floors have flat roofs!)
– Various distances of view: across a street of 5 m. (medieval city street); 10 m. (medium city center carriage street); 20 m. (wide city center
carriage street/suburb street with buildings located far from plot boundaries); 30 m. (small city square); 100 m. (large city square).
A series of visual simulations (Figs. A3 and A4) have allowed to establish that below 10% (β < 6°) the surface can be considered not critical at all
(low visibility). Starting at around 40% (β = 24°) and up, the surface starts to become very visible (high visibility). Between these two limits, the
visibility can be considered medium (the system details are not clear but the presence of the system is well perceived).
Analysis
Plotting on the same graph (Fig. A5), the visibility of roofs as a function of building heights, tilt angles and observer distances allows to extract
very significant findings:
in narrow to medium wide city streets (up to 10 m.) building roofs are invisible, unless the building is extremely low and the roof extremely tilted. In
Fig. A1. Vision angle (β).
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
684
these situations the only concern may be the remote visibility from the surroundings, mainly depending on the city topography.
In medium to large city streets or in suburb areas where buildings are located far from the plot boundary (around 20 m. width), the visibility is still
generally quite moderate, but steep roof tilting (40° or more) becomes a major concern; depending on the building height it will in fact induce a
medium to high visibility.
Finally , when the building is in front of a large space such as a city square (50 m. or more), the crucial factor for visibility becomes the roof tilting,
while the building height starts to have a much reduced impact. Medium tiltings (around 20°) always result in medium visibility, while high
tiltings (around 40°) always lead to a high visibility.
A more comprehensive calculation process, aiming at automating the calculation of visibility of city surfaces based on available city 3D re-
presentations (eg LIDAR) has been conducted at EPFL-LESO in the form of a PhD thesis (Florio, 2018). This work takes into consideration city
topography, visual obstructions, as well as all the different angles of vision) (Munari Probst and Roecker, 2015; Florio et al., 2016, 2017, 2018).
5 6 7 8
Fig. A4. Simulations of the visual impact of distance on a 3 floors building with a 25° tilted roof (upper numbers refer to situations in Fig. A5).
1 2 3 4
Fig. A3. Simulations of the visual impact of roof tilting on a 2 floor building seen from a 10 m distance (upper numbers refer to situations in Fig. A5).
Fig. A2. Values of β and of the actual visibilty reduction (% of viewed surface) for different vision distances, building height, roof tilting.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
685
References
Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on
the energy performance of buildings http://eur-lex.europa.eu/legal-content/EN/
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Dessi, 2013. Methods and tools to evaluate visual impact of solar technologies in urban
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Munari Probst, M.C., Roecker, C., 2011. Urban acceptability of building integrated solar
systems: Leso QSV approach. Proceedings ISES 2011. Kassel, Germany.
Munari Probst, M.C., Roecker, C., 2015. Solar energy promotion & urban context pro-
tection: LESO-QSV (Quality-Site-Visibility) method. PLEA Architecture in (R)evolu-
tion, Bologna IT.
Florio, P., Roecker, C., Munari Probst, M.C., Scartezzini, J.-L., 2016. Visibility of building
exposed surfaces for the potential application of solar panels: a photometric model.
UDMV Workshop, Liège.
Florio, P., Munari Probst, M.C., Schüler, A., Roecker, C., Scartezzini, J.-L., 2018. Assessing
visibility in multi-scale urban planning: a contribution to a method enhancing social
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tegration of solar energy systems. In: Proceedings Eurosun 2000, Copenhagen,
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tion criteria and guidelines. Deliverable T.41.A.2 of IEA SHC 41 Solar energy and
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Florio, P., Schüler, A., Munari Probst, M.C., Scartezzini, J.-L. Visual prominence vs ar-
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web-shared photos. CISBAT 2017, Lausanne.
Florio, P., 2018. Thése EPFL 8826; Towards a GIS-based Multiscale Visibility Assessment
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Fig. A5. Visibility [%]as a function of observer distance.
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IEA SHCP Task 51 Solar Energy in Urban Design, 2018 (http://task51.iea-shc.org/pub-
lications).
Munari Probst, M.C., Roecker, C. Promoting Solar Energy While Preserving Urban
Context; SHC Solar Update – May 2016.
Prize rets Framtidsbyggare: Innovator of the year2016. Sweden November 15th 2016.
http://aretsframtidsbyggare.se/wp-content/uploads/2016/05/Pressmeddelande-
rets-Framtidsbyggare-161116.docx.
Academic courses
MC Munari Probst, Master course “Energie Solaire et Architecture”, Ecole Polytechnique
Fédérale de Lausanne (EPFL) since 2015.
MC Munari Probst, 2015b. Master course “SOLAR ENERGY & ARCHITECTURE”.
Università IUAV di Venezia, Italy, since.
Munari Probst, M.C., Roecker, C., 2009. Bachelor course“Intégration architecturale de
l’Energie solaire”. Ecole Polytechnique Fédérale de Lausanne (EPFL) since.
M.C. Munari Probst and C. Roecker Solar Energy 184 (2019) 672–687
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... When the PV and ST technologies are integrated into the building facade, they acts as a multifunctional integral elements (Grete, Prof, and Mnal, 2001;Buker and Riffat, 2015); they do not only fulfill a technical energy purpose (i.e. heating, cooling, and power) but also contribute to the building fabric from an architectural and materials perspective (Hestnes, 1999;Munari Probst and Roecker, 2007). Also, they could affect the amount of heat transfer through the building envelope, and accordingly the energy demand in the building, since they change the thermal resistance of the building envelope (Lai and Hokoi, 2015). ...
... Several architectural criteria have been defined in the framework of the International Energy agency project Task 41 ''Solar Energy and Architecture" for BIPV formal integration quality, (Munari Probst and Roecker, 2012;IEA, 2013). Based on these criteria and previous literature (Munari Probst and Roecker, 2007Dessì, 2011;Probst and Roecker, 2011), two evaluation aspects are proposed in this research; formal and functional aspects. The analysis processes are fully logical and not affected by the preferences of individuals. ...
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Nowadays, society is becoming increasingly conscious of the adverse effect of energy use on the environment, contributing to the depletion of fossil fuels and increasing global warming. Because of the substantial contribution of building energy to these concerns, the intention should be not only to improve building energy efficiency but also to promote the use of renewable technologies, especially solar energy. Today building-integrated photovoltaic (BIPV) and building-integrated solar thermal (BIST) technologies are recognized by building designers as innovative technology for clean energy and greenhouse gas reduction, especially in cities, where multi-story buildings are dominant with limited roof area. For the Mediterranean area, the high level of solar radiation and plentiful sunny hours make it appropriate for solar system installation, however, the development of solar energy is still limited. Moreover, due to the high population growth rate, lack of local resources, high energy price, and urbanization, one of the priorities in the Mediterranean area is to promote the energy efficiency of the building both on the supply side and demand side. Therefore, this research aims to investigate the potential of installation of the photovoltaic (PV) and solar thermal (ST) technologies in the new multi-family residential building envelope in the Mediterranean area, taking Amman, Jordan, as a case study. The focus of this research is on the typical multi-family residential buildings in Amman, as it is the city where about 50% of the new construction in Jordan is taking place, and the residential buildings are the major consumers of energy and electricity in Jordan. The multi-family buildings also form about 75% of the total housing stock in Jordan. The typical multi-family building studied here is composed of five main floors, contains ten residential apartments; the area of each apartment is 150 m2. It is assumed that the building is located in a common residential urbanized zone in Jordan, with 6 m sides offset and 8 m back offset, assuming that one side is facing the main street, and all the buildings have a maximum allowable height of 15 m. All the architectural parameters related to the multi-family buildings have been defined through analyzing the residential building stock in Jordan. In order to achieve the research aim, the possibility of reducing the energy demand of the typical multi-family building in Amman, Jordan, through passive and architectural design strategies was firstly investigated. After that, different performance criteria were evaluated, mainly quantitative criteria including energy consumption, energy production, and life cycle assessment (energy, carbon, cost). In addition to the qualitative criteria, including visibility and functionality, the purpose here is to emphasize the substantial function of BIPV systems. Each performance criterion was assessed alone. Then, all the performance criteria results were presented in a decision support matrix, which can be used as a comparison to evaluate and identify the solar system's application of choice, based on the criteria of the user. Moreover, a new energy index was formulated to evaluate the overall annual energy performance of BIPV design in terms of multifunctional effects on building energy. Different methods were adopted in this research; the qualitative criteria were evaluated based on the literature review analysis, while the quantitative criteria were evaluated by using different simulation software, previous literature review, and spreadsheet calculations. 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The energy demand was calculated on an hourly basis for a period of a whole year. The results from the simulation analysis, related literature and guidelines were adopted to conduct a life cycle assessment through spreadsheet calculation, to determine the long-term performance in terms of energy and carbon emissions, as well as cost considerations, taking into account the current market practice. The cradle-to-grave approach was adapted for the environmental life cycle assessments. The general conclusion of this research is that installing the PV modules into the multi-family buildings envelope in Amman, Jordan, makes a positive contribution in terms of energy performance, as PV systems can cover up to 97% of the new building electricity demand when they are installed on both the roof and south façade, and up to 43% is covered by installing the PV modules into the south facade. Regarding the environmental life cycle assessment, the results proved the carbon saving potential of all the proposed PV systems, as the energy payback time (EPBT) is between 1.5- 3.5 years and the carbon payback time (CPBT) is between 3.4- 7.8 years. However, for the life cycle cost assessment the result showed that due to high capital cost and low cost of electricity, neither system is currently feasible for investment, as the payback time (PBT) is between 9.0- 16 years. However, with future advances in each system and more efficient designs, the payback periods would become tangible and therefore yield better performances. Lastly, the results were used to derive a decision support matrix aimed at providing a friendly approach to facilitate the implementation of solar building applications.
... Uopšteno, neprovidni solarni kolektori su obično integrisani u neprovidne elemente fasade ili krova. STS sistemi koji su arhitektonski prijatni, imaju dobar materijal i kompoziciju boja, koji se dobro prilagođavaju ukupnoj modularnosti, stvaraju zadovoljavajuću kompoziciju koja će rezultovati dobrom integracijom i visokim arhitektonskim kvalitetom [10,15]. ...
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Buildings were recognized as large energy consumers, and they represent great potential for energy savings through the implementation of a wide range of measures for improving of energy efficiency. Through numerous directives and procedures that have been adopted over the past 30 years, the building sector is committed to the use of renewable energy sources. Among the solutions to the global energy problem, as well as the problem of excessive emissions of greenhouse gases, primarily CO2, which directly affect global warming, the use of solar energy is one of the most acceptable environmental solutions. In the recent years, a new aspect of the application of solar systems in the construction sector has been developed - their integration into the building envelope. This paper presents an overview of the latest research related to solar thermal systems integrated into the building envelope. The current status in the field of technology of solar thermal systems integrated into the building envelope is presented in paper. Different types of these systems that can be integrated into the building envelope are described, and their basic performance is presented. Possible applications of solar thermal collectors in different parts of the building envelope (facade, roof, overhangs, balcony) are also described and presented. By applying these systems, it is possible to significantly influence to the reduction of energy consumption in the building sector, as well as environmental pollution by reducing CO2 emissions.
... It represents a technology that integrating photovoltaic arrays with building envelope, which could provide required energy for building. Although the amount of solar radiation on the vertical surface is 30% less than that on the optimally angled surface, the realization of these techniques avoids heat overproduction and increases the flexibility of the energy system [17]. In recent decades, BIPV has been proved to be a promising and sustainable approach for building renovation [15] [70]. ...
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The purpose of this investigation is to summarize modular façade construction using renewable energy features in different aspects. Researches done so far primarily focusing on building envelop have shown various constructions of building enclosure without energy usage. This paper mainly focuses on modular façade renovation system programmes of European Horizon 2020 [34] and IEA ECBCS Annex 50 Prefabricated Systems for Low Energy Renovation of Residential Buildings in terms of construction, material, installation and thermal performance. Four aspects of construction, material, installation and thermal performance are adopted to evaluate these practices. Related website, paper and report from European commission constitute the database providing for review. Final results illustrate that all modular façade systems mentioned above could be classified into three layers: interior; module and exterior layer, taking charge of disparate functions. Both insulation and energy usage achieve the innovative envelop constructions manufacture. Integrating the renewable energy resources utilization technique into insulated building façade system is the core of this innovative projects achievement.
... When PV technologies are incorporated into building facades, they function as multi-functional integral components (Buker & Riffat, 2015;Farkas et al., 2012;Probst & Roecker, 2011); it provides more than a technical energy purpose. Additionally, it contributes to the architectural and material fabric of the buildings (Hestnes, 1999;Probst et al., 2007). It may also affect the amount of heat transmitted through the building envelope. ...
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Photovoltaic energy-generating has attracted widespread attention, because of its efficiency and environmental benefits. As the number of buildings floors increases, the area of the façade grows substantially larger than the roof, which led to increasing the potential for a solar system installed on the vertical walls, although they receive less solar radiation than roof surfaces. As a result, it has become critical to assess the solar installation possibilities on buildings’ roofs as well as facades in the early design stage. Accordingly, the aim of this paper is to present a method to evaluate the suitable area on the building surfaces for photovoltaic installation, taking Apartment buildings in Amman, Jordan as a case study. The methodology is based on the assessment of the incident solar radiation on different surfaces, considering the shading effect from surrounding buildings in the most common residential urban zone in Jordan, and architectural suitable areas for PV installation. Different simulation software was used, Autodesk Ecotect simulation software was used to calculate the incident solar radiation on the building surfaces and IDA ICE 4.8 simulation software to predict the overshadowing area. The main findings of this study show that conducting a solar potential in the early design stage is critical to defining the most suitable surfaces for PV installation. Moreover, the highest potential envelope part of installing the solar photovoltaic technologies is the roof because it is unshaded and received the highest solar radiation, followed by the south façade with about 40% less received solar radiation. This study can contribute to supporting energy and urban planners in determining the best locations for solar photovoltaic installations on building surfaces.
... As such, a review of precedent active integrated envelopes and facades (AIFs) is relevant. Buildingintegrated technologies have been reviewed in such focus areas as photovoltaics [7], thermal collection and life cycle analysis [8], concentrating technologies [9,10], and architectural integration [11]. To the authors' knowledge, an investigation coupling a highconcentration/daylighting system such as BITCoPT to a full-building scale application and distribution strategy-designed specifically to leverage envelope-wide collection-has not yet been undertaken. ...
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... From a technical and engineering point of view, the utmost possibilities of architectural integration presented by the solar systems are undisputed. Just thinking of individual modules dimensions (absorbers and cells), the pipes' stiffness for transporting hot water in comparison with cables transporting electricity, lastly, the produced energy characteristics: electric energy or thermal energy is intended for consumption in the immediate vicinity of the place where it is produced, while electricity can also be transported over large distance [2]. However, the envelope possibility and the vertical facade generally present well sunny and large surfaces, further more they represent the public shape of the building for which energy issues are sacrificed in favor of architectural consistency. ...
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... It is preferable to adopt the concept of coherence of the photovoltaic solutions used within the architectural concept [24], rather than focusing on the assessment of the objective quality of the installation itself, considering the relational compatibility of the BIPV system with the compositional principles of the envelope and with its technological and type-morphological characteristics. To adapt to different buildings and contexts, photovoltaic systems should provide maximum flexibility in relation to a number of architectural integration parameters. ...
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... Research reveals a broad consensus regarding the perception of high-quality architectural design and the existence of implicit criteria that are shared by the architectural community (Kaan & Reijenga, 2004;Munari Probst & Roecker, 2007. The acknowledgment of solar modules as an integral part of a building requires coherence of formal aspects of solar energy systems such as geometry, material and module as well as fi eld size and form with the building design. ...
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Cities play a key role in facing the challenges of climate change and building envelopes serve as the representative face of the built environment while simultaneously offering opportunities to integrate climate and energy active technologies such as solar energy or building greenery. Thus, they are able to contribute to climate protection as well as to climate adaptation and liveability. To exploit these potentials, the district scale has proven to be effective and manageable, benefitting from synergies among buildings and infrastructures. However, district development and reno-vation needs to cope with limited urban surfaces and a variety of civil-society, political and economic stakeholders with partially conflicting objec-tives and claims. Thus, a balancing and prioritization of different technological measures and design options for building envelopes is required, considering urban planning, architectural, energy, climate, biodiversity and other aspects beyond the envelope context. This research work develops a holistic, district-scale design and decision support in early design stages to promote high performance and resilient building envelope solutions. The methodology is based on a multi-criteria decision analysis (MCDA) approach in order to account for the complexity of design decisions. It provides a transparent and structured process to systematically evaluate and compare different envelope designs in five categories. A modular structure allows the adaptation of the decision support system according to individual decision contexts and criteria as well as to the assessment scale from a single building up to a whole district. Based on a default decision context, a wide target system and associated criteria were derived and the evaluation and aggregation principles were developed. To offer intuitive application, the theoretical concept was implemented into a user-friendly digital tool. In conclusion, the tool offers support to investors and developers, architects and urban planners as well as municipal and private business decision makers in objectively comparing and communicating different design scenarios in a structured workflow to make robust implementation, investment or funding decisions. Used during early design stages, it can promote district concepts with high energy and climate performance and resilience and reduce reservations about the architectural quality of solar and greening systems and their integration in sensitive urban environments. Perspectively, a more sophisticated MCDA method will be applied in order to use the full potential of MCDA to model and display various stakeholder perspectives as default option in the framework of a case study.
Article
In this paper, a novel concept of an unglazed solar thermal facade collector (USTFC) was developed based on a commercially available metal cladding facade system. A detailed mathematical model of USTFC was developed. To validate the developed mathematical model, five prototypes of the USTFC, different in design, were prepared and experimentally tested. To demonstrate the application potential of the USTFCs for a solar domestic hot water (SDHW) system, a whole year simulation analysis was performed in the TRNSYS simulation software using the validated mathematical model under three different climatic conditions (Stockholm, Prague, and Barcelona). The simulation results showed that the efficiency of the USTFC-based SDHW system is strongly dependent on climatic conditions. The highest SDHW system efficiency of 14.5% was obtained for Prague and the lowest SDHW system efficiency of 11.7% was obtained for Barcelona. The influence of the solar storage volume to the collector field area ratio on the performance parameters of the presented SDHW system was also investigated. It was found that a value of 35–45 l/m² can be used as the first estimation for the preliminary USTFC-based SDHW system configuration.
Chapter
The role of public transportation is important as one of the foremost modes of utilities in cities, in achieving user comfort and welfare. Transport would help to transfer people from one place to another, and with the high population density, the demand for transportation, whether cars or buses, has increased. Thus, it has become a major source of pollution in the world; in general, and particularly, in the Arab Republic of Egypt. Hence, the researchers, from developing countries, have discussed the problem extensively within the academic literature, contemplating innovative and smart solutions to address such problems by working to reduce greenhouse gas emissions. This paper aims to provide practice for recording, illustrating, and discussing the tardiest technologies that are considered a change or revolution in public transportation sector systems. The role of modern electric transportation, which is environmentally friendly low-carbon means, is adopted by many developed countries, including the Arab Republic of Egypt as part of social sustainability. As a consequence, the researcher emphasizes the importance of governments, authorities, designers, and planners’ role in building up a framework for the design of environmentally friendly charging centers within the Arab Republic of Egypt to operate electric public transit without any further cost. This could be accomplished through the usage of solar energy panels, PV, by designing modern architectural methods to connect PV panels with charging centers and work them into sustainable centers, where many developed countries and some Arab countries also have now proceeded to sweep up this concept, trying to use it in order to improve city welfare. ©2016 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of IEREK, International experts for Research Enrichment and Knowledge Exchange.KeywordsPublic transportElectrical transportPV panelsEnvironmental pollutionFriendly environmental charging centers
Thesis
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Urban areas are facing a growing deployment of solar photovoltaic and thermal tech-nologies on building envelopes, both on roofs and on façades, essential for the realization of the Swiss Energy Strategy 2050. This process often occurs regardless of the desirable archi-tectural integration quality in a given urban context, which depends on socio-cultural sensitivi-ty and on the visibility of the solar modules from the public space. Visibility and visual impact are recurrent decisional factors in spatial planning processes, with practical implications in-cluding touristic and real estate promotion, outdoor human comfort, way finding, public feeling of security and advertisement. In this thesis, the definition of visibility under a geometrical, physical and psycho-physiological perspective is explored, several quantitative indicators being described and test-ed. The objective is to provide a scale-dependent methodology to assess the visibility of build-ing envelope surfaces exposed to solar radiation, which could host solar modules, in urban areas. A visibility index is determined for inclusion as a variable in a multi criteria method, cover-ing areas from the strategic broad territorial scale to the district level, including neighborhoods and clusters of buildings. Accomplished research includes the estimation of public visual inter-est on the basis of crowd-sourced photographic databases, complementing geometry-based parameters such as cumulative viewsheds and solid angles. At each scale, the visibility index is systematically overlapped on an urban sensitivity layer issued from land use and on a spatial representation of the solar energy generation potential, at an appropriate level of detail. Results indicate that stakeholders can reasonably expect to harvest a serious amount of solar energy by means of building integrated solar systems without crucially affecting public perception. In the study area located in the city of Geneva (Switzerland), more than 50 m2 / building of non-visible envelope surface receiving sufficient solar radiation for an economically viable solar re-furbishment is available over half of the buildings. Solar thermal collectors or PV panels in-stalled on scarcely visible surfaces, mainly situated in courtyards, far from the streets or in deep urban canyons, could cover about 10% of the annual heating demand or alternatively, the same share of electricity needs on a district basis. At the same time, plenty of highly visible areas remain available for high-end solar deployments, which could also serve pilot and demonstration purposes.
Article
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Urban areas are facing a growing deployment of solar photovoltaic and thermal technologies on building envelopes, both on roofs and on façades. An effective solar energy planning process considers social acceptance, in relation to the landscape alteration induced by the solar modules. “Visual impact” is often considered as a major component of social acceptance but comprehensive visibility assessment models are lacking at the scale of the city. This paper presents a scale-dependent methodology to assess the visibility of building envelope surfaces exposed to solar radiation, which could host solar modules, in urban areas. A match between annual solar radiation, visibility and socio-cultural sensitivity of the built environment are proposed in a multi-criteria decision framework. Results are illustrated for the city of Geneva (Switzerland), as a case study: a partial overlap between highly sensitive urban areas and high visual interest is identified at the broad, strategic planning scale. In a second more detailed phase, a frequency breakdown of buildings is provided, according to the (non-) visible share of useful roof area for solar energy production. Less visible roofs are more likely to be situated in courtyards, far from the streets, in deep urban canyons or on low-pitched roofs. The outcomes indicate that stakeholders can reasonably expect to harvest a serious amount of solar energy by means of building integrated solar systems without crucially affecting public perception. In Geneva, more than 50 m2 / building of non-visible roof surface receiving sufficient solar radiation for an economically viable solar refurbishment is available over half of the buildings. This method is valuable for large districts or cities (i) to spot more / less visible building sets and to estimate adapted precinct refurbishment strategies; (ii) to compare visibility on a common conventional basis and to detect zones deserving further investigations at the finer scale.
Article
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Architectural integration of solar technologies in the built environment is a challenge: one of the key tasks is the identification of homogeneous zones of intervention as a function of the solar energy potential and “criticity”, a combination of the socio-cultural value of the urban context (sensitivity) and the visibility from the public space [1].
Conference Paper
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Urban areas are facing a growing deployment of solar technologies on the built exposed surfaces such as roofs and façades. This transformation often occurs without consideration of the needed architectural quality, which depends on the context sensitivity and on solar technologies visibility from public space. The definition of visibility is explored in this paper, and major assessment methods are described. Specifically, a Cumulative Viewshed Algorithm (CVS) is compared with a novel backward raytracing Illuminance Metric Approach (ILL). Results from a test-case in Geneva show how CVS better describes visibility from a remote perspective, while ILL is a promising and fast method for closer viewpoints, especially in urban canyon environments.
Conference Paper
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Research summary Increased use of solar collectors in buildings is necessary but poses major challenges in existing built environments, especially where architectural coherence is an issue. The large size of solar systems at the building scale requires careful planning, as they may end up compromising the aesthetics of buildings, threatening the identity of entire contexts. A new method named Leso‐QSV has been developed to help authorities preserve the quality of pre‐existing urban areas while promoting solar energy use. The method is based on the concept of architectural " criticity " of building surfaces. The level of "criticity" of a surface is defined by the Sensitivity of the urban context and by the Visibility of this surface from the public domain: the more sensitive the urban area, the more visible the surface, the higher its " criticity " (Fig.1), and consequently, the need for Quality in integration. The method is composed of two complementary tools, "Leso‐QSV Acceptability" and "Leso‐QSV Crossmapping". The first is meant for city protection and is addressed to authorities, to support assessing solar systems acceptability: a simple integration quality evaluation method is proposed, and software is provided to help adapt acceptability requirements to city specificities. The second is addressed to planners. It maps the architectural criticity of city surfaces and superimposes it with the GIS solar irradiation map, so as to weight the solar potential of each surface with the expected architectural integration effort. The result shows the interest/difficulty to use the various city surfaces for solar energy production, and helps tailor energy policies to city specificities. The vision underlining the approach is that solar integration is possible also in delicate contexts, if appropriate design efforts and adequate cost investments are made. If these investments cannot be afforded it may be better to postpone the operation, as poor integrations usually end up just discouraging new users. By contrast, if well designed, such examples can be among the strongest driving forces for solar change, repaying by far their extra cost.
Article
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Although mature technologies at competitive prices are largely available, solar thermal is not yet playing the important role it deserves in the reduction of buildings fossil energy consumption. The generally low architectural quality characterizing existing building integrations of solar thermal systems pinpoints the lack of design as one major reason for the low spread of the technology. As confirmed by the example of photovoltaics, the improvement of the architectural quality of building integrated systems can increase the use of a solar technology even more than price and technique. This thesis investigates the possible ways to enhance the architectural quality of building integrated solar thermal systems, and focuses on integration into façade, where the formal constraints are major and have most impact. The architectural integration problematic is structured into functional, constructive and formal issues, so that integration criteria are given for each architectural category. As the functional and constructive criteria are already recognized by the scientific community, the thesis concentrates on the definition of the formal ones, yet underestimated or misunderstood. The results of a large European survey over architects and engineers perception of building integration quality are presented, showing that for architects formal issues are not a matter of personal taste, but that they relate to professional competences, and consequently can be described. The solar system characteristics having an impact on the formal quality of the integration are identified (formal characteristics), the related integration criteria are assessed, and finally integration guidelines to support architect integration design work are given. The limits imposed by the collectors available in the market are pointed out, showing that the lack of appropriate products is nowadays the main barrier to BIST (Building Integrated Solar Thermal) architectural quality. A methodology for the development of new solar thermal collectors systems responding at the same time to energy production needs and building integration requirements is defined. The importance to ensure, within the design team, the due professional competences in both these fields is stressed. Three progressive levels of system "integrability" are defined in the path leading to the concept of "active envelope systems" and the main role of facade manufacturers is highlighted. The methodology is applied to unglazed and glazed flat plate systems, and new façade system designs are proposed that show the relevance of the proposed approach.
Article
The LESO-PB has been working on the architectural integration of photovoltaic elements with the financial support of the Swiss Federal Office of Energy since 1990. In this paper, we discuss the advantages and the feasibility of the integration of photovoltaics, focusing on the following test-installations:— The DEMOSITE, an international exhibition centre of photovoltaic building elements, which was set up to inform potential users (architects, authorities and anybody who might commission a building) about the architectural integration possibilities of photovoltaics.— Two new photovoltaic systems integrated into buildings on the campus of the Swiss Federal Institute of Technology: (1) cladding on the facade of one of the buildings of the Department of Electricity, and (2) an innovative flat roof installation situated on the building of the Department of Materials where photovoltaic panels are mounted on low supports of reinforced concrete.
Article
The way solar systems are used in buildings is different from what it used to be. Buildings are no longer designed to use just passive solar energy systems, such as windows and sunspaces, or active solar systems, such as solar water collectors. In fact, the words passive and active no longer make sense, as the newer buildings combine several of these technologies. They may be both energy efficient, solar heated and cooled, and PV powered, i.e. they are simply “solar buildings”. The paper discusses the various approaches in building integration of solar systems, and presents a number of successful examples. It also presents some of the work being done on improving the design processes to account for the need for a holistic approach to solar building design.