An investigation into the energy and control implications of adaptive comfort in a modern office building

PhD ThesisAn investigation into the potentials of adaptive comfort in an office building is carried out using fine grained primary data and computer modelling. A comprehensive literature review and background study into energy and comfort aspects of building management provides the backdrop against which a target building is subjected to energy and comfort audit, virtual simulation and impact assessment of adaptive comfort standard (BS EN 15251: 2007). Building fabric design is also brought into focus by examining 2006 and 2010 Approved Document part L potentials against Passive House design. This is to reflect the general direction of regulatory development which tends toward zero carbon design by the end of this decade. In finishing a study of modern controls in buildings is carried out to assess the strongest contenders that next generation heating, ventilation and air-conditioning technologies will come to rely on in future buildings. An actual target building constitutes the vehicle for the work described above. A virtual model of this building was calibrated against an extensive set of actual data using version control method. The results were improved to surpass ASHRAE Guide 14. A set of different scenarios were constructed to account for improved fabric design as well as historical weather files and future weather predictions. These scenarios enabled a comparative study to investigate the effect of BS EN 15251:2007 when compared to conventional space controls. The main finding is that modern commercial buildings built to the latest UK statutory regulations can achieve considerable carbon savings through adaptive comfort standard. However these savings are only modestly improved if fabric design is enhanced to passive house levels. Adaptive comfort can also be readily deployed using current web-enabled control applications. However an actual field study is necessary to provide invaluable insight into occupants’ acceptance of this standard since winter-time space temperature results derived from BS EN 15251:2007 constitute a notable departure from CIBSE environmental guidelines

Evaluation of energy and indoor environmental performance of a UK passive house dwelling

The preliminary findings of the energy and indoor environmental performance of a Passive House dwelling in North East of England is presented in this paper. This dwelling is designed to comply with the Passive House Standard (certified by the International Passive House Association) which aims to reduce energy consumption and carbon emissions. The property benefits from advanced building fabric design and materials, PV array, mechanical ventilation with heat recovery system (MVHR) and high efficiency domestic hot water storage vessel to minimise operational carbon emissions. Power generated by the PV panel, imported grid electricity and mains gas consumption of this house are monitored by a proprietary monitoring package; and data of indoor temperature, relative humidity and resident occupancy at several different locations in the dwelling are also recorded. A computational model of this property was developed using DesignBuilder software. The model was validated using the data monitored on site; and is used to predict and evaluate the performance of the house. The initial findings of this study shows the advantages of Passive House in achieving high thermal comfort and good indoor air quality with much lower energy consumption compares to the national averag

Building-integrated rooftop greenhouses: an energy and environmental assessment in the mediterranean context

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.Postprint (published version

Towards 2050 net zero carbon infrastructure:a critical review of key decarbonization challenges in the domestic heating sector in the UK

One of the most challenging sectors to meet “Net Zero emissions” target by 2050 in the UK is the domestic heating sector. This paper provides a comprehensive literature review of the main challenges of heating systems transition to low carbon technologies in which three distinct categories of challenges are discussed. The first challenge is of decarbonizing heat at the supply side, considering specifically the difficulties in integrating hydrogen as a low-carbon heating substitute to the dominant natural gas. The next challenge is of decarbonizing heat at the demand side, and research into the difficulties of retrofitting the existing UK housing stock, of digitalizing heating energy systems, as well as ensuring both retrofits and digitalization do not disproportionately affect vulnerable groups in society. The need for demonstrating innovative solutions to these challenges leads to the final focus, which is the challenge of modeling and demonstrating future energy systems heating scenarios. This work concludes with recommendations for the energy research community and policy makers to tackle urgent challenges facing the decarbonization of the UK heating sector.</p

A multi-zone, fast solving, rapidly reconfigurable building and electrified heating system model for generation of control dependent heat pump power demand profiles

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

Building-integrated greenhouses raise energy co-benefits through active ventilation systems

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 ReviewedObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats SosteniblesObjectius de Desenvolupament Sostenible::7 - Energia Assequible i No ContaminantPostprint (published version

Improving urban metabolism: bi-directional energy and environmental benefits of rooftop greenhouse and building integration

Rapid global urbanisation in 21st century results in cities consuming vast resources but also offering unique opportunities for more integrated and circular resource management. This work investigates potential benefits of urban agriculture and buildings integration through a demonstrator building (ICTA). Actual building and integrated Rooftop Greenhouse (iRTG) data demonstrate wide thermal profiles across ICTA six levels and the potential for heat exchange within the building. Calibrated model monthly results indicate reduced building heating needs resulting from iRTG inclusion. However, more modest GSHP electrical cooling reductions resulting from plant transpiration showed reversing potential which requires more in-depth analysis of underlying principles.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 Muñoz 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 María de Maeztu program for Units of Excellence in R&D (MDM-2015-0552).Peer ReviewedPostprint (published version

Pervasive sensing as a mechanicsm for the effective control of CHP plant in commerical buildings

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

Effect of tilt angle on the performance of a thin-film photovoltaic system

Solar energy is among the cleanest and most sustainable ways to enhance electrical supply's resiliency and reliability for domestic and industrial use. A Photovoltaic (PV) system is the most effective way of capturing solar energy. Long-term warranty, low-cost maintenance, and vast resource availability, solar power generation has an advantage over other approaches. Thin-film technology PV cells are a new kind of solar cell that offers an efficient technique of generating electricity from sunlight. The thin-film PV technology (FFMAT-10, Renovagen, UK) used in this study can supply 0.9 to 1.6 kW of energy to the fast-fold energy hub. The hub’s system status and configuration display battery power input, battery’s state of charge, thin-film PV power and AC power output. Two fast-fold mats (with a surface area of 25.3 m2) were connected to the energy hub. Increasing energy demand coupled with frequent power outages, and inaccessibility of electricity in rural areas necessitates the usage of PV systems at their best performance level. The study objective, therefore, sought to assess the effect of tilt angle on the performance of the thin-film PV system. The study was conducted at Kimicha in Kirinyaga County Kenya, and Juja, Kenya at tilt angles between 0o to 30o. The results indicated that the mean peak PV power for Kimicha was 347.8±231.9 W at 5o and 517.7± 131.3 W at 15ofor Juja. The maximum solar radiation during the study period was 1086.4 ±211.4 W/m2 for Juja and 973.5±219.93 W/m2 for Kimicha. From the study, it was realized that an optimal tilt angle yields optimum solar radiation that translates to maximum power production. Even though the study was conducted in two different regions, it may be applied to any other geographical location. The outcome of the study aids in acquiring self-sustaining power in the most remote locations where electricity is scarce as well as improving energy security