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A major concern for sustainable development is urban systems energy consumption. A possible way to gain additional whole system energy efficiencies is to integrate rooftop greenhouses (iRTG) on unoccupied roofs. This work presents actual environmental data (2015–2018) and calibrated energy modelling results to analyze the energy symbiosis between an iRTG and the host building. Simulation results illustrate that annually 98 kWh/m2 of heating energy is passively recovered (84% during night time) from the building by the iRTG. Conversely the iRTG insulating capacity resulted in annual energy saving of 35 kWh/m2 for the host building (equal to 4% of the building’s annual energy needs). When combined an overall 128 kWh/m2 of net energy savings and 45.6 kg CO2 eq/m2 of savings are realised via iRTG. On average, iRTG daytime temperatures can be 5.1 °C warmer (summer) and -4.3 °C cooler (winter) than the building. This presents major potentials for recovery and exchange of heating and cooling energy flows through integrating heating and ventilation air conditioning systems of the building and iRTG. Hence, iRTGs can provide a source of renewable energy as well as a sink for building exhaust air to improve energy efficiencies of urban built environment and urban agriculture. The authors are grateful to the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya for the award of a research scholarship (FI-DGR 2018) to Joan Muñoz-Liesa; to the Universitat Autònoma de Barcelona for the award of a research scholarship (PIF-2017) to Martí Rufí-Salís; to the Spanish Ministry of Economy and Competitiveness (MINECO) for the financial support to the research project Fertilectiy II “Integrated rooftop greenhouses: energy, waste and CO2 symbiosis with the building. Towards foods security in a circular economy” (CTM2016-75772-C3-1-R; CTM2016-75772-C3-2-R). Authors also acknowledge financial support from the Spanish Ministry of Science, Innovation and Universities, through the “María de Maeztu” program for Units of Excellence (MDM-2015-0552). This work was additionally enabled by the Càtedra JG Ingenieros – Universitat Politècnica de Catalunya and the UK Engineering and Physical Sciences Research Council grand EP/P001173/1. Authors also thank Oriol Baeza, Prof. Xavier Gabarrell, Prof. Joan Rieradevall and the ICTA-UAB staff for their very valuable supporting advise and help.

Buildings and greenhouses consume vast amounts of energy and natural resources for heating and ventilation. It is still unclear how the synergetic effect of combining greenhouses and buildings' forced waste airflows could improve both systems' energy efficiency. This study quantified the energy recovery potential of exchanging airflows in a rooftop greenhouse (iRTG) integrated with an office building HVAC system in a Mediterranean climate. Using monitored and calibrated energy model data, the results showed that the iRTG can act as a solar collector and as a sink for a building's low-grade waste heat. The magnitude of harvested thermal energy that could be recirculated into the building by the integrated HVAC system was 205.2 kWh/m2y-1 and was limited by greenhouse low transmissivity (54%). The magnitude of building exhaust air was 198 kWh/m2y-1 at temperatures sufficient to heat and cool the iRTG. Compared to a passive ventilated configuration, the integration of active ventilation strategies doubled the energy benefits. Building ventilation requirements directly determined building and greenhouse waste flows and energy benefits, which increased by 63.1% when air changes per hour moved from 1.59 to 3.16. Overall, this demonstrates that greenhouse and building functionalities could be coupled to contribute to urban circularity and sustainability. The authors are grateful to the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya (Catalonia) for the award of a research scholarship (FI-DGR 2020) to Joan Muñoz-Liesa. Authors also acknowledge financial support from the Secretaria d'Universitats i Recerca del Departament de Recerca i Universitats de la Generalitat de Catalunya for the grant awarded under AGAU 2020 PANDE 00021 and the Spanish Ministry of Science, Innovation and Universities, through the “María de Maeztu” program for Units of Excellence in R&D [CEX2019-000940-M]. This work was additionally enabled by the Càtedra JG Ingenieros – Universitat Politècnica de Catalunya and the UK Engineering and Physical Sciences Research Council grant EP/P001173/1. Authors are also grateful to Elisa López-Capel, Sostenipra research group and ICTA-UAB staff for the very valuable support, advice and help. Peer Reviewed Objectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenibles Objectius de Desenvolupament Sostenible::7 - Energia Assequible i No Contaminant

Fruits are high moisture agricultural produce rendering them highly perishable hence the danger of postharvest losses is also lurking when there are inadequate storage facilities. The losses result from physical, chemical, and physiological changes that are triggered by the loss in moisture content. Preservation of fruits using available and affordable technologies (such as charcoal coolers) can benefit small-scale farmers in minimizing postharvest losses. An evaporative charcoal cooler 4 m long, 4 m wide, and 2.5 m high providing a 40 m3 storage capacity was utilized in the study. The cooler with a 150 mm wide cavity filled with charcoal had a perforated pipe connected to a 1000-litrecistern raised at 2.5 m above the ground and connected to a water pump (Pedrollo PKm 60, Italy) that kept the charcoal wet by a drip system. The pump and the three axial fans (REC-21725 A2 W, USA) rated 180 cubic feet per minute (CFM) and 2600 revolutions per minute (RPM) were powered by fast fold thin-film PV (FFMAT-10, Renovagen, UK) system connected to a 10-kWh rated energy hub (FFENERGYHUB-10, Renovagen, UK). Temperature, relative humidity and product quality parameters (weight loss, total soluble solids, vitamin C content and firmness were evaluated).The evaporative cooler temperatures reduced significantly (P

With increasing the efforts towards modernization of residential buildings and changing their functionality towards more proactive players in the networks, energy management systems can be regarded as an important contributing solution. Although several approaches have been developed in the literature for energy scheduling of buildings, the effect of occupants comfort as an objective function on the decision making process and its influence on the energy exchange between dwelling units requires more investigations. This study proposes a multi-objective energy management strategy for a group of active buildings (ABs) that form a residential microgrid (RMG), making a trade-off between operational cost of community and comfort level of its occupants. A building-to-building strategy is developed which benefits from rooftop photovoltaic output to supply the RMG loads. Also, the significance of electric vehicles in helping the community to achieve its techno-economic goals is investigated, taking into account the driving behaviour of users. A mixed integer linear programming model is introduced, benefiting from lower computation time and achieving a global optimal solution. The simulation results show the necessity of considering the cost and comfort simultaneously. Besides, the effect of building collaboration and electric vehicles in achieving the community’s goal is observed.

This paper proposes a method for applying engineering design principles to a type of energy system called a smart local energy system. Axiomatic design theory is used to develop a series of knowledge domains about a demonstrator energy system, the knowledge domains describing the different facets of customer, functional, solution and construction elements that make up the system as a whole. An aspect of axiomatic design theory called large flexible system theory is applied to a small subset of the demonstrator system to create a knowledge base about the operational modes of the system. The knowledge base ensures that an operational schedule for the system can be produced that maintains the integrity of the system design.

The authors are grateful to the Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya for the award of a research scholarship (FI-DGR 2016) to Joan Munoz Liesa; the Spanish Ministry of Economy and Competitiveness (MINECO) for the financial support of the research project Fertilectiy II “Integrated rooftop greenhouses: energy, waste and CO2 symbiosis with the building. Towards foods security in a circular economy” (CTM2016-75772-C3-1-R; CTM2016-75772-C3-2-R) and the Maria de Maeztu program for Units of Excellence in R&D (MDM-2015-0552).

Sustainability certifications like BREEAM, LEED, and China's sustainable green building award certification scheme encourage installation of technologies that save mains water and grid electricity. Among these are rainwater harvesting systems, ultralow water use appliances, photovoltaic panel systems, and intelligent building management systems. In reviewing the performance of two award-winning university buildings over respective periods of sixteen and four years, we found that such systems delivered only 28–71% of their potential resource savings. These performance gaps arose from various technical and social issues (pump failures, tank leakages, poor alignment of demand and supply with limited storage, low photovoltaic panel efficiency, poor user acceptance, etc.), but the consequences were exacerbated by inadequate asset management that resulted in long system downtimes, in some cases for 2–5 years. Repair, maintenance, and upgrading expenses then combined with lower than anticipated water and electricity bill savings that ultimately meant that, for the most part, there was no prospect of earning a return on capital expenditures. Continuous monitoring of building water consumption by an external service provider was the most effective resource and cost saving solution in this study, as it required no capital expenditure, and revealed a 1640 l/h leakage, without putting high demands on the building management. In contrast, little value was obtained from 25 water-related sensors installed as part of a “building-as-a-lab” project because of inadequate post hand-over support. Robust post-commissioning operation should become a key criterion for sustainable building innovation, and this should be reflected in green awards and rating systems.

Short ‘product lives’ and disposable packaging result in premature disposal of valuable resources. Industrialisation, mass production and global supply chains have resulted in a disconnect between people, places, materials and design. Upcycling is reuse of discarded materials which results in an increase in ‘value’. We discuss the potential for creative upcycling to reconnect people with materials and establish cultures and communities of making. The reaction of the public to creative reuse is explored by creating a cafe structure made entirely from recycled materials, and this provides the starting point to consider the contexts in which upcycling occurs, the motivations for (and barriers to) reuse and upcycling, the potential benefits of upcycling in the context of affluent Western 'consumer' societies, and the scope for designers to imbue objects with the potential for creative reuse. We argue that designing to enable creative upcycling allows the future lives of objects to be contingent on context and culture, rather than being prescribed by the designer, with potential for widespread social, economic and environmental benefits.

The electrification of heating is expected to grow in the UK domestic sector, and this has increased interest in the effects that this may have on low and high voltage network operation. However, Electrified heating profiles that alter with control decisions can only be obtained from dedicated building modelling that energy system modellers do not usually have the expertise to perform, yet these are required for meaningful studies. This work outlines a novel method for modelling air source and ground source heat pump power demand profiles using a multi-zone physics based building modelling framework with building fabric, thermohydraulic, and air flow subsystems. The novel setup framework allows detailed building layout, fabric and control properties to be assigned by analysts with no prior building modelling expertise. Once fully assigned, the building model can be used to generate heat pump power demand profiles at sub minute resolution. Upon testing, a single daily run of the model could be executed in 17 s. The model was then validated against real life test house data, under various control and weather conditions. A small relative error (typically within 10%) was observed between modelled and actual cycle lengths, and modelled and actual heat and electricity demands. Due to its rapid solution rate, the model is of significant value to energy efficiency and distribution network studies, where large demand profile sets that are sensitive to detailed retrofit and control considerations are often essential. The model has been made openly available.

The building performance monitored over one year of a Conventional House and a Passive House in North East England is presented in this paper. These two houses which differ in building fabric, the type of ventilation and thermal storage, the use of different energy and residents’ occupancy result in distinct building energy performance and indoor air quality. According to the measurement data, the primary energy demand of the Conventional House and Passive House were 169.85 kWh/(m2a) and 64.11 kWh/(m2a) while the annual average indoor temperature of the two properties maintained at 17.7°C and 22.0°C, respectively. A simulation study was conducted by DesignBuilder software to improve the Conventional House’s energy and indoor environmental performance using passive retrofitting methods, aiming to reduce the primary energy demand, the space heating demand of the property and enhance its general indoor air environmental performance. The DesignBuilder models were validated by monitored data and used to predict the performance of the Conventional House after retrofitting, and then compared it with the Passive House. The results indicate the reduction of space heating demand is by about 80% compared to its current status. The findings showed that there was a huge potential for conventional house retrofitting using passive energy saving methods in northern England.

A new domestic air-source heat pump model is proposed which can be parameterised either from field data, experimental data or manufacturers’ standard rating data. The model differs from the much more prevalent system-side regression models for these types of heat pumps in that it operates on refrigerant-side variables. This makes it more suited to detailed performance analyses of heat pumps in service. Because both field data and manufacturers’ data can be used for parameterising the model, it can be used to investigate problems associated with the building performance gap where a heat pump is used. A new type of efficiency-based compressor model is developed which enables compressor performance to be directly compared with alternatives and a model of defrosting is included by introducing a new defrost discounting term. Results tested using data from a field monitoring site and from a laboratory installation show good predictive behaviour by the model especially at low source air temperatures. When the model is fitted using manufacturer’s standard rating data, a performance gap is evident when compared with the model fitted to field data but the gap is generally nominal.

Buildings worldwide consume approximately 45% of primary energy sources, making it the single largest energy consumption sector. The importance of improving a building’s energy performance was emphasized by the government with the enforcement of sustainable building policies. Article 9 of the Directive 2010/31/EU of the European Parliament and the Council (19th May 2010) on the energy performance of buildings states the importance of stimulating refurbishment of existing buildings into near zero-energy buildings. However, the effectiveness of the process depends on the basic building structure and the refurbishment designs. Hence, methods to find the effective strategies for retrofitting and modelling to predict energy reduction is vital. Unlike the previous studies, this paper presents a method for a deep building retrofit based on the whole building’s thermal analysis specifically for cooling demand countries. This work set against recommended best practice office building energy benchmarks in Malaysia, and following a comprehensive building audit, a retrofit strategy was proposed based on target building’s thermal analysis with cooling demand reduction in particular focus. It was found that 71% of the building’s heat gain emanated from its lighting system and solar heat gain through windows. A 40.2% reduction in the building’s cooling load is estimated to reduce 47% of the total energy consumption. A comparison of the actual and simulated energy results suggested that the simulation made under predicted the energy reduction by 4.3%.

While photovoltaic (PV) technology is considered a renewable energy source, it nonetheless has a degree of environmental impact. In order to completely capture the net environmental gain of a PV system, its necessary to conduct a life cycle analysis (LCA). This paper attempts to summarise the latest developments of two prominent crystalline, i.e. single crystalline (sc-) and multi crystalline (mc-) silicon PV systems with regards to their environmental performance and sustainability. The PV life cycle is assumed to begin at pre-production, after which PV module production, operation, installation geography, and finally recycling/disposal are also included. The embodied energy requirement, energy payback time (EPBT), and greenhouse gas (GHG) emission for crystalline silicon PV technologies were reviewed, summarised and evaluated. All environmental impact results were further discussed to highlight existing constraints in previous LCA studies. Both sc-Si and mc-Si share Siemens process during manufacturing, however sc-Si requires the additional Czochralski process which results in higher embodied energy requirement and EPBT for sc-Si technology. Therefore while sc-Si retains a higher conversion efficiency, this increased electrical energy output for a given surface area is still not enough to lower sc-Si׳s EPBT to levels comparable to ms-Si. Higher conversion efficiency however means that sc-Si panels outperform mc-Si on space efficiency. A set of recommendations for further work form the concluding parts of this work, in particular full examination of LCA of hybrid c-Si given that it combines the best features of sc- and mc-Si PVs, and currently, there is very little data available on hybrid c-Si.

This work uses high resolution data from 130 electricity sub-meters to characterise a 12,500m2 commercial building as a virtual power plant (VPP) by assessing magnitude and duration of electrical loads suitable for demand response (DR). In 2018, the building had a peak hourly demand of 48 W/m2 and its electricity consumption (183.2 kWh/m2/yr.) was within low to medium range of air-conditioned UK portfolio. Deferrable loads from heat pumps, air handling units, lifts, lighting, circulating pumps and dry air coolers were used to illustrate building's DR capability over a maximum duration of 4 h per DR cycle. On average, deferrable loads form 46.4% of total building electricity consumption and across a 4-hour DR cycle can be characterised as having an initial power (and stored energies) of 28 kW (401 ± 117 kWh); 109 kW (571±82 kWh); and finally 138 kW (625±18 kWh) for 100%, 41.5% and 24.6% of time respectively. Following a DR event, the HVAC ability to restore original indoor climate was found to be at least twice as fast as climatic drift during the event. A linear regression model was found to be weak in using external temperature to predict the magnitude of aggregated deferrable loads.

In electrical or thermal appliances, heat (thermal energy) must either be added into or removed from a system to maintain operational stability. Heat pipes can enhance the heat transfer capabilities without needing a significant temperature gradient between heat sources and heat sinks. The effectiveness of heat pipes is due to the latent heat of phase change of the working fluid within (i) condensation and (ii) evaporation stages. The latent heat of phase change greatly exceeds the sensible heat capacity. Heat pipes may rely on gravity, wicks, centrifugal force or in some cases even a magnetic field to help return condensate flow from the condenser to the evaporator. Wicks in heat pipes are classified into three groups: sintered, groove and mesh types. This review attempts to cover various types of heat pipes such as thermal diodes, variable conductance, pulsating, etc. The application of nanotechnology in heat pipes can be separated into two groups: nanoparticles and nanobubbles, with the latter receiving considerably less attention than the former. The hybridisation of heat pipe technology is also possible and has been discussed along with its future research potential.

Unidad de excelencia María de Maeztu MdM-2015-0552 A sustainable and secure food supply within a low-carbon and resilient infrastructure is encapsulated in several of The United Nations' 17 sustainable development goals. The integration of urban agriculture in buildings can offer improved efficiencies; in recognition of this, the first south European example of a fully integrated rooftop greenhouse (iRTG) was designed and incorporated into the ICTA-ICP building by the Autonomous University of Barcelona. This design seeks to interchange heat, CO2 and rainwater between the building and its rooftop greenhouse. Average air temperatures for 2015 in the iRTG were 16.5 °C (winter) and 25.79 °C (summer), making the iRTG an ideal growing environment. Using detailed thermophysical fabric properties, 2015 site-specific weather data, exact control strategies and dynamic soil temperatures, the iRTG was modelled in EnergyPlus to assess the performance of an equivalent 'freestanding' greenhouse. The validated result shows that the thermal interchange between the iRTG and the ICTA-ICP building has considerable moderating effects on the iRTG's indoor climate; since average hourly temperatures in an equivalent freestanding greenhouse would have been 4.1 °C colder in winter and 4.4 °C warmer in summer under the 2015 climatic conditions. The simulation results demonstrate that the iRTG case study recycled 43.78 MWh of thermal energy (or 341.93 kWh/m2/yr) from the main building in 2015. Assuming 100% energy conversion efficiency, compared to freestanding greenhouses heated with oil, gas or biomass systems, the iRTG delivered an equivalent carbon savings of 113.8, 82.4 or 5.5 kg CO2(eq)/m2/yr, respectively, and economic savings of 19.63, 15.88 or 17.33 €/m2/yr, respectively. Under similar climatic conditions, this symbiosis between buildings and urban agriculture makes an iRTG an efficient resource-management model and supports the promotion of a new typology or concept of buildings with a nexus or symbiosis between energy efficiency and food production.

Commercial greenhouses are often referred to as the optimum heat dump for very low grade waste heat from a variety of sources. However availability, temperature levels and fluctuations in the availability necessitate a very different approach towards production planning as compared to traditional systems where energy supply is adapted to production demand and not the converse. In this study, a commercial ornamental plant nursery that had switched its heat supply from natural gas to utilizing the waste heat of a commercial CHP system in 2007 was analysed. The differences between production planning and temperature regimes before and after switching to waste heat were compared. Furthermore, the degree of utilization of the waste heat available was evaluated. The study undertaken showed three main results: Firstly, greenhouses present a good opportunity for the use of the low grade waste heat. However production needs to be planned very carefully to facilitate the production of high quality plants, for which traditional cultivation planning is unsuitable. Secondly, when planning on utilizing the heat (7.1 GWh th /a) of a CHP system which is sized based on electricity output (6.7 GWh el /a), to the full capacity, additional users need to be found and ideally heat storage integrated. Currently heat utilization amounts to less than 45% (3.1 GWh th ) in total. Especially in summer most of the heat is discarded. Thirdly, several scenarios for utilization optimization were considered. The scenarios described allow for an increase of heat utilization to 62% or 4.4 GWh th using some of the heat to run absorption chillers to provide cooling in summer and storing excess heat in long term heat stores (300 MWh th ) to reduce the additional gas demand. The results of the economic evaluation show that the integration of a cold store, supplied by the coolth by using an absorption chiller is financially attractive with a resulting payback period of 2.9 years, whilst consideration of integration of a PCM heat store is far from being viable with a payback period of almost 300 years.

Energy and environmental data is collected from 5 tower blocks each containing 90 apartments to create two representative calibrated energy models. Three towers (heated by individual natural gas boilers) characterise medium (137.3 kWh/m2/yr.) and two (heated by electrical night storage heaters) characterise low (75.4 kWh/m2/yr.) thermal demands when benchmarked against actual UK domestic portfolio. Across 2020–2040 time horizon, an uncertain landscape is represented by 12 fuel carbon intensity and 14 economic scenarios in order to examine building fabric upgrade, without or in conjunction with centralised CHP engines, GSHP and biomass boilers in the case study towers. Out of 18 retrofit options examined, 7 or 8 solutions (under annual fuel price rises of 2% or 5.2% respectively) can provide lifetime CO2e mitigation at unit costs that fall below the upper bounds of carbon capture and storage technologies (US$143/tCO2e). If carbon taxation were to be used to enable full recovery of retrofit capital expenditure with no government subsidy, the lowest tax level observed belongs to a transition to centralised biomass from decentralised natural gas boilers requiring US$111/tCO2e (in 2020), while deep retrofits (i.e. plant and fabric) require much more punishing carbon taxes with 2020 figures ranging from US$233/tCO2e to US$1665/tCO2e.

A recently completed, EPSRC-funded project researched the use of low cost, pervasive sensing to monitor building environmental conditions and occupant interactions as a means to reduce the uncertainties associated with the creation of a building model for refurbishment options and smarter control appraisal. This paper gives a brief introduction to the pervasive sensing system as established within the project and describes its use to enable simulations of the multi-input, multi-output (MIMO) control of a combined heat and power (CHP) unit in a commercial building context. Within the project, data from pervasive sensing was used to calibrate a simulation model of an office building and impose occupant-related inputs at the time step level as a means to reduce modelling uncertainty. The MIMO input parameters considered include space temperatures, heat store temperatures, electricity demand and electricity tariff, while the output parameters include space heat supply, heat stored, electricity utilised locally or exported, and CHP unit fuel use. The simulation model was used to compare performance when the CHP unit is subjected to conventional and MIMO control. It is demonstrated that the pervasive sensing approach enables control that delivers enhanced energy performance.

Model calibration Measured energy data Local weather data Building performance simulation Energy Plus Hourly data Sensor deployment Case study building a b s t r a c t A large number of randomly interacting variables combine to dictate the energy performance of a building. Building energy simulation models attempt to capture these perturbations as accurately as possible. The prediction accuracy of building energy models can now be better examined given the widespread availability of environmental and energy monitoring equipment and reduced data storage costs. In this paper a set of two calibrated environmental sensors together with a weather station are deployed in a 5-storey office building to examine the accuracy of an EnergyPlus virtual building model. Using American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guide 14 indices the model was calibrated to achieve Mean Bias Error (MBE) values within ±5% and Cumulative Variation of Root Mean Square Error (CV(RMSE)) values below 10%. The calibrated EnergyPlus model was able to predict annual hourly space air temperatures with an accuracy of ±1.5 ◦ C for 99.5% and an accuracy of ±1 ◦ C for 93.2% of the time.

A recently completed, EPSRC-funded project researched the use of low cost, pervasive sensing to monitor building environmental conditions and occupant interactions as a means to reduce the uncertainties associated with the creation of a building model for refurbishment options and smarter control appraisal. This paper gives a brief introduction to the pervasive sensing system as established within the project and describes its use to enable simulations of the multi-input, multi-output (MIMO) control of a combined heat and power (CHP) unit in a commercial building context. Within the project, data from pervasive sensing was used to calibrate a simulation model of an office building and impose occupant-related inputs at the time step level as a means to reduce modelling uncertainty. The MIMO input parameters considered include space temperatures, heat store temperatures, electricity demand and electricity tariff, while the output parameters include space heat supply, heat stored, electricity utilised locally or exported, and CHP unit fuel use. The simulation model was used to compare performance when the CHP unit is subjected to conventional and MIMO control. It is demonstrated that the pervasive sensing approach enables control that delivers enhanced energy performance.