Conference PaperPDF Available

INTEGRATED ROOFTOP GREENHOUSES AND GREEN SKYLINE CITIES

Authors:

Abstract and Figures

The paper proposes a new strategy against the global warming, which if applied on large scale is able to turn our cities into green oasis, decreasing their actual carbon footprint and increasing their carbon offset. Our approach is to replace conventional roofs with integrated rooftop greenhouses IRTG, which are connected with the interior of the building by controlled flows of energy, oxygen, carbon dioxide and water. The main IRTG feature is the tight human-plant symbiosis ensured by a two flows ventilation system , conveying O2 enriched air from RTG to building and CO2 enriched air from building to RTG. To be applicable at large scale with no particular infrastructure demands, IRTGs systems are provided with renewable energy devices suited to the local climate: heat pumps (water to water for building's basement and air to air for greenhouse), solar panels, etc. and also with Internet of Things equipment. Such way IRTGs can harvest local renewable energy resources (geo-thermal, solar, wind, etc.), store them and manage them together with the water resources. Besides future dedicated projects, inserting IRTGs into the existing urban infrastructures is possible, depending of the buildings' condition, so nowadays cities may be gradually turned into Smart Green Skyline Cities.
Content may be subject to copyright.
Green Buildings, Technologies and Materials
INTEGRATED ROOFTOP GREENHOUSES AND GREEN SKYLINE CITIES
Prof. Marius M. Balas1
Assoc. Prof. Jelena Nicolic2
Prof. Ramona Lile1
Assist. Prof. Mihaela Popa1
Assist. Prof. Roxana Beiu1
1 Aurel Vlaicu University of Arad, Arad, Romania
2 Polytechnic University of Catalonia, Barcelona, Spain
ABSTRACT
The paper proposes a new strategy against the global warming, which if applied on
large scale is able to turn our cities into green oasis, decreasing their actual carbon foot-
print and increasing their carbon offset. Our approach is to replace conventional roofs
with integrated rooftop greenhouses IRTG, which are connected with the interior of the
building by controlled flows of energy, oxygen, carbon dioxide and water. The main
IRTG feature is the tight human-plant symbiosis ensured by a two flows ventilation sys-
tem, conveying O2 enriched air from RTG to building and CO2 enriched air from build-
ing to RTG. To be applicable at large scale with no particular infrastructure demands,
IRTGs systems are provided with renewable energy devices suited to the local climate:
heat pumps (water to water for building’s basement and air to air for greenhouse), solar
panels, etc. and also with Internet of Things equipment. Such way IRTGs can harvest
local renewable energy resources (geo-thermal, solar, wind, etc.), store them and man-
age them together with the water resources. Besides future dedicated projects, inserting
IRTGs into the existing urban infrastructures is possible, depending of the buildings’
condition, so nowadays cities may be gradually turned into Smart Green Skyline Cities.
Keywords: roof top greenhouse, building metabolism, renewable energy, computer
model, urban sustainability.
INTRODUCTION
Each oxygen molecule we breathe was produced by photosynthesis. Oxygen is very re-
active, without the presence of plants most of our resources would be fixed into diverse
inorganic compounds. Unfortunately, especially starting from the Industrial Revolution
around 1760, our civilization intervened into the natural balance of the atmosphere, re-
placing huge amounts of oxygen with carbon dioxide, as a result of burning fuels and
deforestations. CO2 is causing global warming because of the greenhouse effect. This
tendency put in danger our very future and as rational and responsible beings, we must
find solutions for a new sustainable technological establishment, before being too late.
The last decade witnessed the beginning of an historical shift towards low foot-printed
and high offsetting carbon dioxide technologies. The political will of the majority of the
countries to oppose global warming has been officialised by the the 2015 United Nations
Framework Convention on Climate Change of Paris [1].
18th International Multidisciplinary Scientific GeoConference SGEM 2018
Practical solutions to materialize the 2015 Paris Convention are not easy to find and the
shift towards green, recyclable and low energy materials and for the efficient exploita-
tion of the renewable energy is expensive even for the rich countries. Our belief is that
the actual building and renewable energy technologies have reached the maturity stage,
offering a wide variety of products at settled prices. We witness a favourable conjunc-
ture for questing and testing new concepts, in the sense of the Paris Convention’s.
Our approach assume the following arguments:
We must rebuild a sustainable balance between humans and plants at planetary scale;
The only meaningful resource we dispose is represented by our cities;
Simple and cheap solutions for chronical issues are not to be expected, a multidisci-
plinary and holistic approach is needed, in the sense of the System Engineering, includ-
ing Physics, Civil Engineering, Renewable Energy and Water Management, Human and
Plant Physiologies, Architecture and Urbanism, Information Technology, Economy, etc.
Binding so many elements into a single feasible entity is possible only if we will be
able to identify and to grow synergies between them.
The strategic target is to build a new relationship between cities and agriculture.
CITY AND AGRICULTURE
Traditionally, people were living in villages and towns, while agriculture was practiced
on the surrounding lands. That was natural, given the big surfaces of land demanded by
the traditional outdoor agriculture to feed the population. Agriculture was to be found
inside cities only during food crises (consequences of natural or political catastrophes,
sieges, etc.) We consider the actual climate changes as a major crisis in development, so
we draw our focus on how to bring again agriculture into our cities. This trend is now of
high interest for the scientific research. One can identify two significant approaches:
Urban Agriculture (UA) [2], [3], etc. working on modalities to cultivate plants into
cities. At present, UA is a growing trend with a broad variety of typologies, from high-
tech to traditional, from private terraces to public gardens. UA brings numerous ad-
vantages: it promotes sustainable development, food safety and affordability, environ-
mental and food education, local economy, biodiversity and therefore it should be in-
cluded in cities urban and management plans.
Building-Integrated Agriculture (BIA) [4], [5], working on modalities to cultivate
plants into or onto buildings. Since usual urban land surfaces are severely insufficient
for agriculture, the only sustainable option is BIA onto buildings that is to overlap hu-
mans and plants habitats. This idea is not new, Rooftop Greenhouses (RTG) are well-
known for decades. Replacing traditional roofs with greenhouses exerts some construc-
tive difficulties, offering instead the presence of plants and better insulations for build-
ings. However, RTGs have failed to overcome the demonstrative stage, due to a weak
economic efficiency. The newest concept in this sense, the Integrated Rooftop Green-
house (IRTG), seems to be destined to a better future [6], [7], [8]. Integrating RTGs
with buildings means simply to introduce controlled air, energy and water exchanges
between them, creating an indoor humans-plants symbiosis, with numerous advantages
for both sides, given their complementarity: integrated energy, water and gases manage-
ment, improving the building metabolism, on the account of the surrounding renewable
energy and water resources [6]. These connections are lacking at conventional RTGs.
The implementation target moved from industrial parks [9] to office buildings [10].
Green Buildings, Technologies and Materials
THE BARCELONA INTEGRATED ROOFTOP GREENHOUSE
The first IRTG prototype is to find in Barcelona, as a result of the FertileCity Project.
The Institut de Ciència i Tecnologia Ambientals (ICTA) IRTG is located in the Autono-
ma University Campus of Bellaterra, Barcelona, Spain. The building was designed and
built in 2014 as a compact, multi-functional volume, with energy efficiency and mainly
employing the BIA concepts. The building’s area is 7,200 m2 distributed in 6 plants with
offices, laboratories, common spaces, parking and warehouses. The building has two
RTG spaces of around 125 m2 that are integrated into the building’s roof and make up
the ICTA-iRTG (Fig.1), aiming to grow crops by hydroponic technology and also pro-
moting the humans-plants symbiosis. That allows to maintain the ideal conditions indi-
cated by FAO for the cultivation of vegetables in Mediterranean areas (14 °C to 26 °C).
Figure 1. The ICTA building with the Integrated Rooftop Greenhouse [6]
A notable initiative towards the increasing of the IRTG areas in cities uses airborne sen-
sors, Light Detection and Ranging (LIDAR) and Long Wave Infrared (LWIR) [11].
SPECIFICATIONS FOR AN INTEGRATED ROOFTOP GREENHOUSE
It is known that interdisciplinary and complementary bodies of knowledge, organized
according to the Systems Engineering principles, are able to achieve performances be-
yond the sum of the individual components’ performances [12]. Having this in mind, we
propose a generic IRTG system, descripted by a set of specific features:
1) IRTG must take advantage of all the renewable energy and water resources that are
available in the urban environment (sun, wind, geothermal, rain water, wasted water,
etc.). That is why, among other features, they must be conceived as Renewable Energy
Exploitation Systems (harvesting, storage, local optimal use, etc.). The practical solu-
tions should be adapted to the urban environment. Instead of bulky and dangerously ro-
tating wind turbines, air-to-air heat pumps should be used. Photovoltaic panels are not
necessary because urban buildings are provided with electricity. Instead, they should be
replaced by solar thermal systems, able to store the solar energy generated by the green-
house effect. The main renewable energy device, namely the water-to-water heat pump,
should use ground-coupled heat exchangers instead of water wells, because phreatic wa-
18th International Multidisciplinary Scientific GeoConference SGEM 2018
ters in urban regions are unreliable and insufficient for high buildings’ concentration.
Integrating such heat exchangers into buildings’ foundations seems feasible.
2) An opportune development of the IRTG concept should begin, as in the case of the
industrial buildings, automobiles trains or air-plains, with a network that is providing
connectivity and is integrating sensors, actuators, communication devices and distribut-
ed controllers able to take smart decisions. In other words, the IRTGs must be turned
into iRTGs, Intelligent RTGs, an Internet of Things subject.
3) In sum, the iRTGs must be conceived as Smart City basic cells. The IRTG architec-
ture confers an inherent capacity for managing in an integrated and smart way the re-
newable energy, water and gases resources that are to find in our cities.
4) Due to these features, the iRTG electricity, water and gas consumption should not
exceed in any mean an equivalent conventional building consumption. Turning an exist-
ing conventional building into an iRTG should not affect the existing infrastructure.
Such way, according to the disposable resources, one can gradually transform the
nowadays cities into future Green Skyline Cities, composed exclusively of iRTGs.
Fig. 2. A generic Integrated Rooftop Greenhouse system
Green Buildings, Technologies and Materials
AN INTEGRATED ROOFTOP GREENHOUSE MATHEMATICAL MODEL
We are introducing a generic IRTG structural model composed by differential equations
with constant parameters for the main physical processes (at this stage), which will be
eventually validated and non-linearized using experimental data and optimized by
neural networks or genetic algorithms, according to a previously used methodology
[13].
The model subsumes the following parameters: V[m3] volumes, ρ[kg/m3] air density, ca
[J/kg·oK] air specific heat, T[oC] temperature, D[m3/s] air flows, α [W/m2·oK] mean
heat transfer coefficients through walls, S[m2] radiant surfaces, N number of persons,
Po[W] mean power emitted by a person, PGE[W] power of the greenhouse effect, P[W]
heating/cooling power, τ[s] time delays, C[kg/m3] concentrations, Q[kg/m3·s] gas
emission flows (by plants and persons). U is the recirculation factor, thus [1-U(t)]
represents the fresh outside air proportion in a ventilated air flow. Index G refers the
greenhouse, index B the building, index RTG the IRTG ventilation system and index E
the environment.
Equation (1) is modeling the evolution of the RTG temperature, under the influence of
the air changes with the environment and the underneath building, the presence of the
greenhouse effect, the presence of people and the action of the heating/cooling
equipment:
VG∙ρ∙caTGt
dt 1‐UGt∙DGt∙ρ∙ca∝G∙SG∙TEt‐TGtNG∙PoPGEG
PGt‐GDB→Gt‐B→G∙ρ∙ca∙TBt‐TGt (1)
Equations (2) and (3) model the RTG oxygen and carbon dioxide concentrations under
the influence of the air changes with the environment and the underneath building, and
of the presence of people (QO2, QCO2) and plants (QO2G, QCO2G):
VGdCO2Gt
dt 1‐UGt∙DGt∙CO2Et‐CO2Gt‐NG∙QO2QO2G
DB→Gt‐B→G∙CO2Bt‐CO2Gt (2)
VGdCCO2Gt
dt 1‐UGt∙DGt∙CCO2Et‐CCO2GtNG∙QCO2QCO2G
DB→Gt‐B→G∙CCO2Bt‐CCO2Gt (3)
18th International Multidisciplinary Scientific GeoConference SGEM 2018
Fig. 3. A Matlab-Simulink implementation of the IRTG model
Equations (4), (5) and (6) model in the same way the building’s variables:
VB∙ρ∙caTBt
dt 1‐UBt∙DBt∙ρ∙ca∝B∙SB∙TEt‐TBtNB∙PoPGEB
PBt‐BDG→Bt‐G→B∙ρ∙ca∙TGt‐TBt (4)
VBdCO2Bt
dt 1‐UBt∙DBt∙CO2Et‐CO2Bt‐NB∙QO2
DG→Bt‐G→B∙CO2Gt‐CO2Bt (5)
VBdCCO2Bt
dt 1‐UBt∙DBt∙CCO2Et‐CCO2BtNB∙QCO2QCO2B
+DG→Bt‐G→B∙CCO2Gt‐CCO2Bt (6)
INTELLIGENT ROOFTOP GREENHOUSE EXPERT CONTROL
The automated control is essentially bounded between the Optimal Control (OC) and
Soft Computing (SC). OC is able achieve optimal performances in what concerns one or
several performance indexes: speed, accuracy, costs, etc. OC relies on quantitative anal-
ysis and numerical representation of knowledge. OC may be successfully applied when
one dispose of precise and detailed knowledge about the controlled plant.
The SC is opposite, relying on qualitative analysis and symbolic knowledge representa-
tion (linguistic, graphical, etc.) The most popular SC technique, the expert control, emu-
lates the way human operators take decisions. SC is recommended when our knowledge
about the controlled plant is imprecise, uncertain or approximate. For iRTGs that are
heating, ventilation, air-conditioning systems (HVAC), very nonlinear and time vari-
able, the expert control is considered to be ideal since the early 80s, especially because
humans and plants are tolerant to weather parameters’ variations (temperature, humidity
and air composition), so accuracy and precision are not crucial. Instead, SC features
such as stability, adaptation, robustness and prediction, are most necessary [14].
The Expert Systems consist in:
Green Buildings, Technologies and Materials
a) Bases of control/decision rules of IF-THEN type, heuristically designed by special-
ists in the application’s domain (not necessarily and in computer science); if the rules
are of fuzzy type, the system becomes a Fuzzy Expert System [15].
b) Inference algorithms, using the rules to synthesize the output control actions.
The following linguistically expressed rules are illustrating this method.
IF TE is Cold AND TB is Cool THAN UB is 1: the fresh air admission is closed preserv-
ing energy into the building; the building is ventilated through RTG
IF TE is Cold AND TG is Cool, and PGE is low THAN UG is 1: no fresh air into RTG,
preserving energy during cold nights
IF TE is Cold AND TG is Cool, and PGE is High THAN UG is Min: maximum amount of
fresh air, taking advantage of the greenhouse effect, during cold sunny days
IF TE is Warm AND TB is Cool THAN UB is Min: warm air from outside
IF CO2G is High AND TG is Not Cool THAN DG
B is ON: RTG provides O2 to building
IF CO2G is Low THAN DG
B is OFF: when the plants are not producing O2
IF CCO2B is High THAN DB
G is ON: the building provides CO2 to RTG
CONCLUSIONS
The paper deals with a new green building concept, the Integrated Rooftop Greenhouse
(IRTG), resulting after connecting a rooftop greenhouse with the underneath building,
by controlled flows of energy, water and gases: O2 enriched air from rooftop greenhouse
to building and CO2 enriched air from building to rooftop greenhouse. IRTG supports
an efficient integrated management of energy, water, CO2 and O2, that is gathering the
disposable renewable energy resources: sun (by greenhouse effect), wind (by air to air
heat pumps), geothermal (by water to water air heat pumps), and water resources (rain
water, household grey water, water vapors), storing and delivering them wherever and
whenever needed inside the IRTG system.
A prerequisite for the IRTG to successfully fulfill the above tasks is to benefit of all
available knowledge about the physical phenomena that are taking place within it as
well as of the data on the actual values of external and internal weather parameters. In
this purpose the paper provides a mathematical structural IRTG model, capable to assist
the sizing of the system in most respects: architectural solutions, construction materials,
sizing of the components (renewable energy, water management, ventilation fans), as
well as the testing of the control algorithms. In order to meet the emerging Smart Cities
specifications, the IRTG must be updated to an Intelligent RTG (iRTG), adequately con-
nected to join the Internet of Things. Due to the smart use of renewable energies, iRTG
energetic footprint is very low so the existing buildings could be upgraded to iRTGs
without perturbing the existing urban infrastructure, according to their condition.
This is leading us towards the possibility to extend the use of iRTG at the scale of a
whole city, The Green Skyline City a structure with increased carbon offset capacity due
to the massive presence of plants, able to oppose the global warming.
ACKNOWLEDGEMENT
18th International Multidisciplinary Scientific GeoConference SGEM 2018
The authors would like to thank the Spanish Ministry of Economy and Competitiveness
(MINECO) for the financial support for the research projects Fertilecity I (CTM2016-
75772-C3-1/2/3-R AEI/FEDER, UE) and Fertilecity II (CTM2013-47067-C2-1-R) and
for the María de Maeztu program for Units of Excellence in R &D (MDM-2015-0552).
REFERENCES
[1] United Nations. Framework Convention on Climate Change, Adoption of the Paris
Agreement, 2015, https://unfccc.int/resource/docs/2015/cop21/eng/l09r01.pdf.
[2] Eigenbrod C., Gruda N., Urban vegetable for food security in cities: a review, Agro-
nomy for Sustainable Development, Springer Verlag/EDP Sciences/INRA, vol. 35/issue
2, pp 483-498, 2015.
[3] Goldstein B.P., Hauschild M.Z., Fernandez J., Birkved M., Urban versus conven-
tional agriculture, taxonomy of resource profiles: a review, Agronomy for Sustainable
Development, vol. 36/issue 9, pp 4-24, 2016.
[4] Delor M., Current state of Building-Integrated Agriculture, its energy benefits and
comparison with green roofs: summary, The University of Sheffield, UK, Feb. 2011.
[5] Benis K., Reinhart C. F., Ferrão P., Building-Integrated Agriculture (BIA) In Urban
Contexts: Testing A Simulation-Based Decision Support Workflow, Conference: Build-
ing Simulation, San-Francisco, USA, August 2017.
[6] Ceron-Palma I., Oliver-Solà J., Sanyé-Mengual E., Montero J.I., Rieradevall J.,
Barriers and Opportunities Regarding the Implementation of Rooftop Eco.Greenhouses
(RTEG) in Mediterranean Cities of Europe, Journal of Urban Technology, November,
2012, pp. 1-17.
[7] Montero J.I., Baeza E., Muñoz P., Sanyé-Mengual E., Stanghellini C., Technology
for Rooftop Greenhouses, In: Orsini F., Dubbeling M., de Zeeuw H., Gianquinto G.
(eds) Rooftop Urban Agriculture. Urban Agriculture. Springer, Cham, pp. 83-101, 2017.
[8] Sanyé-Mengual E., Oliver-Solà J., Montero J.I., Rieradevall J., An environmental
and economic life cycle assessment of rooftop greenhouse (RTG) implementation in
Barcelona, Spain. Assessing new forms of urban agriculture from the greenhouse struc-
ture to the final product level, The International Journal of Life Cycle Assessment,
Springer, issue 20, pp. 350-366, 2015.
[9] Sanyé-Mengual E., Ceron-Palma I., Oliver-Solà J., Montero J.I., Rieradevall J.,
Integrating Horticulture into Cities: A Guide for Assessing the Implementation Potential
of Rooftop Greenhouses (RTGs) in Industrial and Logistics Parks, Journal of Urban
Technology, vol. 22/issue 1, 2015, pp. 87-111.
[10] Pons O., Ana Nadal, Sanyé-Mengual E., Llorach-Massana P., Cuerva E., Sanjuan-
Delmàs D., Muñoz P., Oliver-Solà J., Planas C., Rovira M. R., Roofs of the future: roof-
top greenhouses to improve buildings metabolism, Procedia Engineering, Creative Con-
struction Conference 2015 (CCC2015), Elsevier, issue 123, pp. 441 – 448, 2015.
[11] Nadal A., Alamús R. Pipia L., Ruiz A., Corbera J., Cuerva E., Rieradevall J., Josa
A., Urban planning and agriculture. Methodology for assessing rooftop greenhouse po-
tential of non-residential areas using airborne sensors, Science of The Total Environ-
ment, vol. 601–602, 1 December 2017, pp. 493-507.
Green Buildings, Technologies and Materials
[12] Oliver D.W., Kelliher T.P., Keegan J.G. Jr., Engineering Complex Systems with
Models and Objects, McGraw-Hill, 1997, pp. 85–94.
[13] Balas M.M., Duplaix J., Bouchouicha M., Balas S.V., Structural modeling of the
wind's influence over the heat flow of the greenhouses, Journal of Intelligent and Fuzzy
Systems, John Wiley & Sons, Special Issue: Soft Computing and Applications, vol.
19/issue 1, pp. 29-40, 2008.
[14] Balas M.M., Buchholtz M., Balas S.V., Expert Control for the Coupled Tanks
Greenhouse, Soft Computing Applications: Proc. of the 6th International Workshop Soft
Computing Applications (SOFA 2014), Springer, vol. 2, pp. 939-948, 2016.
[15] Yordanova S., Merazchiev D., Lakhmi Jain, A Two-Variable Fuzzy Control Design
with Application to an Air-Conditioning System, IEEE Transactions on Fuzzy Systems,
vol. 23/issue 2, pp. 474 – 481, April 2015.
ResearchGate has not been able to resolve any citations for this publication.
Conference Paper
Full-text available
Building-Integrated Agriculture (BIA) in urban areas is claimed to be environmentally sustainable vis-à-vis conventional commercial agriculture practices by reducing food miles, minimizing land and water use and improving yields. However, as it is operated in controlled indoor environments, BIA can be highly energy-intensive. In order to better understand the influence of local foodshed characteristics, climate conditions and farm properties on the environmental performance of BIA systems, this article applies a performance-based parametric simulation workflow for BIA that incorporates daylight, energy, crop growth and water models, to (a) Rooftop Greenhouse (RG) farms and (b) Shipping Container (SC) farms located in the cities of Lisbon, Singapore, Paris and New York. Results show that – while RG farms can significantly reduce GHG emissions under all the tested climates – SC farms may only have a positive overall environmental impact in megacities located in colder climates, that seasonally rely on long distance food imports.
Article
Full-text available
Air-conditioning systems provide optimal conditions for work, human health, and quality of living. At the same time, they are one of the greatest household energy consumers. Therefore, the Building Energy Management System sets high demands on their control, aiming to reduce energy consumption while ensuring indoor comfort. The classic control technique cannot satisfactorily deal with the energy-efficient stabilization of basic interacting microclimate parameters. The fuzzy logic approach offers intelligent means for the stabilization of the coupled temperature, humidity, and fresh air supply with low energy requirements. The aim of this study is to develop a model-free design method for a two-variable PI fuzzy controller for temperature and humidity control that ensures indoor comfort and reduces energy consumption by supervisory fuzzy tuning.
Article
Full-text available
Global food production faces great challenges in the future. With a future world population of 9.6 billion by 2050, rising urbanization, decreasing arable land, and weather extremes due to climate change, global agriculture is under pressure. While today over 50 % of the world population live in cities, by 2030, the number will rise to 70 %. In addition, global emissions have to be kept in mind. Currently, agriculture accounts for around 20–30 % of global greenhouse gas emissions. Shifting food production to locations with high demands reduces emissions and mitigates climate change. Urban horticulture increases global food production by exploiting new locations for cultivation. However, higher land prices and urban pollution constrain urban horticulture. In this paper, we review different urban cultivation systems throughout the world. Our main findings from ecological, economical, and social aspects are: (1) Urban horticulture activities are increasing globally with at least 100 million people involved worldwide. With potential yields of up to 50 kg per m2 per year and more, vegetable production is the most significant component of urban food production which contributes to global food security. (2) Organoponic and other low-input systems will continue to play an important role for a sustainable and secure food production in the future. (3) Despite the resource efficiency of indoor farming systems, they are still very expensive. (4) Integrating urban horticulture into educational and social programs improves nutrition and food security. Overlaying these, new technologies in horticultural research need to be adopted for urban horticulture to increase future efficiency and productivity. To enhance sustainability, urban horticulture has to be integrated into the urban planning process and supported through policies. However, future food production should not be “local at any price,” but rather committed to increase sustainability.
Article
Full-text available
Purpose Rooftop greenhouses (RTGs) are increasing as a new form of urban agriculture. Several environmental, economic, and social benefits have been attributed to the implementation of RTGs. However, the environmental burdens and economic costs of adapting greenhouse structures to the current building legislation were pointed out as a limitation of these systems in the literature. In this sense, this paper aims to analyse the environmental and economic performance of RTGs in Barcelona. Methods A real RTG project is here analysed and compared to an industrial greenhouse system (i.e. multi-tunnel), from a life cycle perspective. Life cycle assessment (LCA) and life cycle costing (LCC) methods are followed in the assessment. The analysis is divided into three parts that progressively expand the system boundaries: greenhouse structure (cradle-to-grave), at the production point (cradle-to-farm gate), and at the consumption point (cradle-to-consumer). The applied LCIA methods are the ReCiPe (hierarchical, midpoint) and the cumulative energy demand. A cost-benefit analysis (CBA) approach is considered in the LCC. For the horticultural activity, a crop yield of 25 kg · m−2 is assumed for the RTG reference scenario. However, sensitivity analyses regarding the crop yield are performed during the whole assessment. Results and discussion The greenhouse structure of an RTG has an environmental impact between 17 and 75 % higher and an economic cost 2.8 times higher than a multi-tunnel greenhouse. For the reference scenario (yield 25 kg · m−2), 1 kg of tomato produced in an RTG at the production point has a lower environmental impact (10–19 %) but a higher economic cost (24 %) than in a multi-tunnel system. At the consumption point, environmental savings are up to 42 % for local RTGs tomatoes, which are also 21 % cheaper than conventional tomatoes from multi-tunnel greenhouses in Almeria. However, the sensitivity assessment shows that the crop efficiency is determinant. Low yields can produce impacting and expensive vegetables, although integrated RTGs, which can take advantage from the residual energy from the building, can lead to low impacting and cheap local food products. Conclusions RTGs face law limitations that make the greenhouse structure less environmentally friendly and less economically competitive than current industrial greenhouses. However, as horticultural systems and local production systems, RTGs can become an environmentally friendly option to further develop urban agriculture. Besides, attention is paid to the crop yield and, thus, further developments on integrated RTGs and their potential increase in crop yields (i.e. exchange of heat and CO2 with the building) are of great interest.
Article
Full-text available
Today 50 percent of the world's population lives in cities. This entails an excessive exploitation of natural resources, an increase in pollution, and an increase in the demand for food. One way of reducing the ecological footprint of cities is to introduce agricultural activities to them. In the current food and agriculture model, the fragmentation of the city and the countryside means energy use, CO2 emissions from transport, and large-scale marketing requirements. Rooftop Eco.Greenhouses (RTEG) consist of a greenhouse connected to a building in terms of energy, water, and CO2 flows; it is a new model for a sustainable production, an eco-innovative concept for producing high quality vegetables and improving the sustainability of buildings in cities. The main objective of this study is to examine the barriers and opportunities regarding the implementation of RTEG in Mediterranean cities in Europe. The work method consisted of discussion seminars involving an interdisciplinary group of experts in the area of agronomy, architecture, engineering, environmental sciences, industrial ecology, and other related disciplines. The barriers and opportunities of RTEG take into account social, economic, environmental, and technological aspects and were determined and analyzed according to three scenarios of implementation: residential buildings, educational or cultural buildings, and industrial buildings. We would highlight the interconnection of the building and the greenhouse as an opportunity of RTEG, making use of water, energy, and CO2 flows between both, as well as the decrease in food transportation requirements. The methodology applied to the study was positive due to the interdisciplinary participation of experts which facilitated a global vision of the implementation of the project.
Chapter
Rooftop greenhouses (RTGs) can generate significant advantages provided RTGs and buildings are connected in terms of energy, water and CO2 flows. Beyond the production of high-value crops, environmental benefits such as re-use of waste water, application of residual heat and absorption of carbon dioxide are derived from urban RTGs. Social benefits viz the creation of employment, social cohesion and so on are also important assets of RTGs. This chapter is focussed on RTGs technology. RTG share many common aspects with conventional greenhouses, but at the same time RTGs show attributes that should be discussed separately. Synergies such as using residual heat, rain water for irrigation, CO2 exchange, etc. are part of the common metabolism greenhouse-building. This chapter will concentrate on the available technology from conventional greenhouses which is more suitable for RTGs, particularly concerning greenhouse structure, covering materials, climate control and soilless cultivation systems.
Article
The integration of rooftop greenhouses (RTGs) in urban buildings is a practice that is becoming increasingly important in the world for their contribution to food security and sustainable development. However, the supply of tools and procedures to facilitate their implementation at the city scale is limited and laborious. This work aims to develop a specific and automated methodology for identifying the feasibility of implementation of rooftop greenhouses in non-residential urban areas, using airborne sensors. The use of Light Detection and Ranging (LIDAR) and Long Wave Infrared (LWIR) data and the Leica ALS50-II and TASI-600 sensors allow for the identification of some building roof parameters (area, slope, materials, and solar radiation) to determine the potential for constructing a RTG. This development represents an improvement in time and accuracy with respect to previous methodology, where all the relevant information must be acquired manually.
Article
Urban agriculture appears to be a means to combat the environmental pressure of increasing urbanization and food demand. However, there is hitherto limited knowledge of the efficiency and scaling up of practices of urban farming. Here, we review the claims on urban agriculture’s comparative performance relative to conventional food production. Our main findings are as follows: (1) benefits, such as reduced embodied greenhouse gases, urban heat island reduction, and storm water mitigation, have strong support in current literature. (2) Other benefits such as food waste minimization and ecological footprint reduction require further exploration. (3) Urban agriculture benefits to both food supply chains and urban ecosystems vary considerably with system type. To facilitate the comparison of urban agriculture systems we propose a classification based on (1) conditioning of the growing space and (2) the level of integration with buildings. Lastly, we compare the predicted environmental performance of the four main types of urban agriculture that arise through the application of the taxonomy. The findings show how taxonomy can aid future research on the intersection of urban food production and the larger material and energy regimes of cities (the “urban metabolism”).
Article
Recently, the application of rooftop greenhouses (RTGs) to integrate agriculture into cities has increased, although the area where they can be potentially implemented has not been quantified yet. Consequently, this paper aims to design a guide to evaluate the potential implementation of RTGs in industrial and logistics parks and to apply the guide to the case study of Zona Franca Park (Barcelona, Spain). Eight percent of the rooftops were identified as feasible for a short-term implementation of RTG, according to the defined technical, economic, legal, and agricultural criteria. Estimations indicated that the annual tomato production in this area could account for almost 2,000 tons, which is equivalent to the yearly tomato demand of 150,000 people. Besides, this production could substitute imported tomatoes, and avoiding their distribution would represent savings of 65.25 t of CO2 eq·m−2.
Article
The paper presents the structural modeling of the wind's influence over the heat flow of a greenhouse, starting from recorded data of an experimental greenhouse. A structural model is much more versatile than a synthetic one, however greenhouses are complicated and highly non-linear, and therefore such a model should be built by aggregating several elementary sub-models with physical significance. The paper is aiming to identify a sub-model for the windy dry nights. The modeling method consists in the identification of the sub-models with low order systems with nonlinear coefficients and their optimization using genetic algorithms. The knowledge of the wind's influence over the thermal behavior of buildings and vehicles help us to improve the designing of such products. Two case studies are presented: a passive greenhouse provided with a heat pump/wind generator renewable energy source and a railway coach. The simplicity of such models encourages implementations at micro-controllers /DSP levels.