Urban Energy and Environmental Modelling: The case of green roofs

Η διδακτορική αυτή διατριβή διερευνά την εφαρμογή της τεχνολογίας των πράσινων οροφών, ως λύση βασισμένη στη φύση, για τη βελτίωση της βιωσιμότητας στις αστικές περιοχές με διαφορετικά κλιματικά και γεωμετρικά χαρακτηριστικά, με έμφαση στα κτίρια κατοικιών και γραφείων. Η καταλληλότητα των εναλλακτικών επιλογών έχει αξιολογηθεί με τη βοήθεια ενεργειακής, περιβαλλοντικής και οικονομικής μοντελοποίησης. Τα αποτελέσματα αυτής της μελέτης καταδεικνύουν κυρίως την εξοικονόμηση ενέργειας σε μεμονωμένα κτίρια που μπορεί να φτάσει έως και 35%, μειώσεις εκπομπών κατά 3-10 τόνους CO2, 2-6 kg NOx και 7-18 kg SO2 ανά κτίριο ανά έτος, καλές οικονομικές προοπτικές για εφαρμογή από μεμονωμένους χρήστες, μετά την εφαρμογή συντηρητικών μειώσεων κυμαινόμενων από 6% έως 35% του αρχικού κόστους εγκατάστασης και, τέλος, βελτίωση της θερμικής άνεσης μέσα στο αστικό περιβάλλον, με την μείωση της θερμοκρασίας στο ύψος ενός πεζού, να κυμαίνεται στους 0,35 Κ. Ειδικά όταν πρόκειται για συστηματική και ευρεία εφαρμογή των πράσινων οροφών σε επίπεδο πόλης, η συγκεκριμένη λύση φαίνεται να μπορεί να αποτελέσει ένα μακροπρόθεσμο μέτρο άμεσης και έμμεσης περιβαλλοντικής αναβάθμισης. Αυτή η δυνατότητα θα πρέπει να αποτελέσει ένα πρόσθετο κίνητρο για τους αρμόδιους φορείς να υιοθετήσουν πολιτικές που προάγουν το σχεδιασμό και την υλοποίηση έργων πράσινων οροφών σε κτίρια των αστικών κέντρων.The objective of this doctoral research is to explore green roofs, as a nature-based solution, for improving the sustainability in urban areas of various climatic characteristics and different geometrical formations, with a focus on residential and office buildings. The appropriateness of these options has been assessed with the aid of energy, environmental and economic modelling. The results of this study indicatively demonstrate energy savings in individual buildings than can reach up to 35%, emission reductions of 3-10 tons of CO2, 2-6 kg of NOx and 7-18 kg of SO2 per building per year, good economic prospects for individual users, with only modest reductions (varying from 6% to 35%) in green roofs’ installation cost and, finally, reduction of urban air temperature reaching up to 0.35 K. Especially when it comes to city-level upgrades, green roofs can be either an immediate or a long-term measure for sustainable urban development. This potential should be an additional incentive for the responsible statutory and administrative bodies to adopt policies that economically promote the design and implementation of urban green roof retrofitting projects.Member of the committee: Stylianos Yiatros, Associate Professor, Department of Civil Engineering and Geomatics, Cyprus University of Technology Member of the committee: Symeon Christodoulou, Professor, Department of Civil and Environmental Engineering, University of CyprusComplete

Quantifying the water-energy nexus in Greece

Published in the 14th International Conference on Environmental Science and Technology (CEST2015), volume 1, pages 1769-1774, ISBN 978-1-5108-1427-

A study on hot-water production of hotels in Cyprus: Energy and environmental considerations

Hotel units are responsible for a significant proportion of energy consumption and carbon dioxide emissions in the tourist sector. This paper focuses on the energy and environmental performance of hot-water production systems utilized by high class hotels in Cyprus in order to formulate appropriate carbon emission mitigation strategies. The main systems used are boilers fired by Liquefied Petroleum Gas or Diesel oil, air-source heat pumps and flat plate solar collectors. The results show that the combination of air-source heat pumps with flat plate solar collectors leads to the lowest primary energy consumption. Therefore, improving the sustainability of the tourism sector in Cyprus requires to phase out the usage of boiler systems that are currently in use in almost all four star and five star hotels and promote the use of solar thermal systems in combination with air-source heat pumps. These findings are relevant for island states and other popular tourist destinations sharing similar characteristics with those of Cyprus and provide a framework for national authorities to plan an appropriate energy and environmental upgrade of the hotel stock

Implementation of green roof technology in residential buildings and neighborhoods of Cyprus

Green roofs are considered as an appropriate nature-based measure to increase the environmental resilience of cities. This paper examines this technological solution applied to typical urban residential buildings in the Mediterranean island of Cyprus, with respect to energy, environmental, and economic aspects. The analysis shows a clearly positive energy and environmental contribution of green roofs. Although such an investment does not seem to be cost-effective in residential buildings, sensitivity analysis demonstrates that green roofs become financially favorable compared to flat roof constructions with only modest reductions in their current installation cost. Moreover, green roofs offer environmental benefits that are currently difficult to monetize, which can clearly improve urban resilience to climate change. In order to quantify the impact of green roof installations on the surrounding environment, the analysis was expanded from the individual building perspective to neighborhood scale implementation, using appropriate simulation software to evaluate the contribution of green roofs to urban heat island mitigation. Focusing on the ambient air temperature at the pedestrian level, a noticeable decrease was estimated

Green roofs dissemination regarding their potential contribution in addressing the UHI effect

The article aims at summarising the state of the art in the efforts of researchers and innovators to find viable solutions to mitigate the urban heat island (UHI) effect. This effect is loosely connected with the greenhouse effect, however, it certainly creates a severe negative synergy together with it. As green roofs are a well-known answer how to address the UHI effect, the ways how to make their massive and global deployment convenient are discussed. Initially, the differences and similarities between urbanisation in developed and developing countries are described. Then the paper depicts solutions, especially synergic ones, for making the dissemination of green roofs viable, such as rainwater and energy harvesting or urban agriculture. Then the authors conclude that retrofitting the existing roofs is the only method for reaching the desired scale and discuss available business models necessary for introducing the prosumer approach to the retrofitting

Energy, environmental and economic assessment of electricity savings from the operation of green roofs in urban office buildings of a warm Mediterranean region

Green roofs are an important technique to efficiently mitigate adverse environmental impacts of buildings. This study focuses both on energy conservation and sustainability related aspects of two alternative green roof solutions applied to a typical urban office building in representative climatic areas of Cyprus in the Eastern Mediterranean. Simulations regarding the buildings’ energy demand were conducted using EnergyPlus software. Based on these results and using an in-house developed algorithm, the primary energy consumption for each alternative solution was computed, assuming variable refrigerant flow air-to-brine heat pump as heating and cooling system, coupled with a calculation of the associated emissions of carbon dioxide, nitrogen oxides and sulphur dioxide. The analysis shows a reduction in primary energy consumption up to 25% in heating and up to 20% in cooling operation, thanks to the use of green roofs, and a corresponding reduction in emissions. The economic viability of the proposed green roof solutions was also examined, taking into consideration both monetary and environmental costs. The results show that the green roof solutions increase the lifetime cost up to 40,000 €, however they can lead to additional environmental and economic benefits which are hard to quantify