Prioritising energy efficiency measures in Maltese restaurants

The 2018 Energy Performance of Buildings Directive (EU) 2018/844, focuses on building energy renovation. With the increase in tourists and working opportunities in Malta, the restaurants’ sector is experiencing a business boom. Despite this sector being a major energy consumer, the energy performance of restaurants in Malta has been given little attention. This paper investigates the energy performance of four representative restaurants in Malta. Refrigeration accounted for the highest share of 40% electricity consumption, followed by kitchen exhaust ventilation, domestic hot water and space cooling, which accounted for about 50%, while lighting consumed only 6%. Energy saving potential was primarily identified for refrigeration, water heating and air-conditioning. Although, the fuel sources used for cooking equipment accounted for more than 50% of the overall energy used in these restaurants, electricity is the fuel of primary concern as on average it contributes to 70% of total carbon emissions and results in the highest operational cost. The total potential of carbon emission savings was found to be 17%, when the recommended energy efficiency measures are applied. A benchmark of 14.51 kWh primary energy per person served was established for energy-efficient restaurants. This paper provides evidence-based results that are useful for policy makers to introduce fiscal incentives to support the transition of Maltese restaurants to nearly-zero energy status.peer-reviewe

Building energy renovation and smart integration of renewables in a social housing block toward nearly-zero energy status

Like other islands, Malta experiences great challenges to secure its energy supply and independence. Deep renovation of buildings to nearly zero energy and addressing “smart-readiness” are widely believed to contribute to solving such challenges, while meeting the exigencies of the 2018 European Union energy performance of buildings directive (EPBD). Nearly zero energy buildings benchmarks for residential buildings in Malta have been defined using established EPBD cost-optimal methodologies, however these guidelines detailing a one-step and one benchmark definition approach neglects peak loads, building-grid interaction requirements and energy storage. To counteract these inadequacies, this research proposes an innovative multi-criteria approach adapted from ISO 52000-1:2017 standard, which supports the new EPBD requirements for optimizing comfort and addressing energy poverty. This is carried out by first optimizing adaptive comfort in “free-running mode,” before switching to mechanical space heating and cooling. When implementing this approach on a case study of an existing 40-family social housing block undergoing deep renovation, it was found that the discomfort hours have been reduced drastically, while the peak demand for the remaining discomfort hours requiring mechanical heating and cooling has been halved. Despite such positive impact of passive measures, the research has quantitatively demonstrated that given Malta’s temperate climate, such measures have lower impact on the energy rating of the building, when compared to that achieved with active and renewable energy (RE) measures. Thus, the proposed multi-tier benchmarking approach ensures that each energy efficiency measure is appropriately weighted on its own merits, rather than lumping all measures under a single benchmark indicator. With regards to smartness indicators for load matching and grid interaction, a detailed analysis using system advisor model software demonstrated that battery energy storage systems have the capacity to match the RE supply to the demand, although this approach is still far away from being cost-optimal. The research concluded that RE incentives should therefore move away from feed-in tariffs and subsidize direct energy use, storage, and load matching given their high costs. Furthermore, the cost-optimal analysis should also quantify the costs of thermal discomfort, energy poverty and grid mismatch, to ensure a holistic approach to deep renovation of buildings.peer-reviewe

Feasibility study of a heat recovery system in an office building in Malta

The new Energy Performance of Buildings Directive (EU) 2018/844 has brought about a new drive to renovate existing buildings, especially for heating and cooling systems, whereby heat recovery techniques have become the order of the day. However, the real energy and financial benefits of applying such techniques have not been studied in Malta, which has a temperate Mediterranean climate. Thus, this study has performed a technical and financial analysis of using different heat recovery options for the most common office type, that is a medium-sized flatted office, using EnergyPlus dynamic simulation tool and multiple linear regressions. Results showed that the coefficient of performance of the air-conditioners, the window to wall ratio and the cooling set-point temperatures, have the greatest impact, while heat recovery has an insignificant contribution to energy efficiency, thus making it rank low in the list of energy efficiency priority measures for medium-sized offices in Malta.peer-reviewe

An innovative approach to manage uncertainties and stock diversity in the EPBD cost-optimal methodology

The EU Energy Performance of Buildings Directive (EPBD) 2010/31/EU is a step in the right direction to promote near zero energy buildings (NZEB) in a step-wise manner, starting with minimum energy performance and cost optimal thresholds for “reference buildings” (RBs) for each category. Nevertheless, a standard method for defining RBs does not exist, which led to a great divergence between MS in the level of detail used to define RBs for the EPBD cost-optimal analysis. Such lack of harmonisation between MS is further evident given the resulting large discrepancies in energy performance indicators even between countries having similar climate. Furthermore, discrepancies of 30% or higher between measured energy performance and that derived from the EPBD software induces uncertainty in the actual operational savings of measures leading to cost-optimality or NZEB in the simulated environment. This research proposes a robust and innovative framework to better handle uncertainties in the EPBD cost-optimal method both in the building software input parameters and in the global Life Cycle Costings (LCC), making the EPBD more useful for policy makers and ensuring a more harmonised approach among MS. The concept behind the proposed framework is the combination of a stochastic EPBD cost-optimal approach with Bayesian bottom-up calibrated stock-modelling. A new concept of “reference zoning” versus the “reference buildings” approach is also introduced in this research, which aims at providing a simpler and more flexible aggregation of energy performance for the more complex commercial building stock.peer-reviewe

EPBD cost-optimal analysis for non-residential buildings in Malta

The Energy Performance of Buildings Directive (EPBD) 2010/31/EU requires EU Member States to calculate the cost-optimal levels of minimum energy performance requirements for new buildings and buildings that undergo major renovation. The European Commission Delegated Regulation (EU) No 244/2012 and accompanying Guidelines 2012/C 115/01 establish a comparative methodology with regards to number of reference buildings for each building category, number of energy efficiency measures to be implemented in the study and the minimum level of cost analysis that is required. This paper fulfils the above requirements but also introduces an innovative approach that goes beyond the minimum requirements for the cost-optimal study, whereby a two-stage optimisation approach was undertaken. The first stage focuses on choosing a representative set of combined building envelope measures that cover the full range of possible energy performance levels, in such a way that these lie along the line of minimum space conditioning costs, known as the Pareto Front. While the second stage applies combinations of energy systems’ upgrades to the selected iterations of stage 1. The scope is to minimize the time cost of these cost-optimal studies without sacrificing on their effectiveness or creating biased results. Cost optimal and nearly-zero energy levels were found for homes for the elderly, hotels, offices, restaurants, shops and sports complexes. Results showed that cost optimal levels are best achieved through upgrades of energy systems and solar shading rather than building envelope U-value upgrades for all building categories. This is primarily a result of the mild Mediterranean climate of Malta. Solar water heating and solar photovoltaics have shown to be cost optimal for all categories, except where these cannot be installed such as in shops and restaurants. Shading, heat pump water heaters and high efficiency air-conditioning systems have also been identified as cost-optimal measures.peer-reviewe

ZeroCO2 buildings – how low can we go : a case study of a small hotel in Gozo

This study has shown that a new typical hotel building in Malta can reduce its CO2 emissions by more than 75 % over a chosen reference scenario with a relatively reasonable payback period of approximately 8 years. Such a reduction in CO2 emissions is possible by tackling the main energy consumer for hotels i.e. energy consumption for hot water. Various Energy efficiency and renewable energy combination of measures were considered in this study, however air to water heat pumps combined with roof and facade mounted photovoltaic's produced the lowest CO2 emissions. Policy to achieve near zero energy/CO2 emissions hotels should therefore focus on implementing renewable energy solutions for generating hot water and facilitating the transition of integrating renewable energy with the facade.peer-reviewe

Interreg Europe zeroco2 project - action plan for Malta to promote near zero co2 emission buildings

Buildings are responsible for 36 % of CO2 emissions in the EU. The Interreg Europe project entitled ZEROCO2 ‘‘Promotion of Near Zero CO2 emission buildings due to energy use” aims at addressing policies, actions and investments to facilitate the transition of buildings to nearly Zero CO2 emission buildings due to energy use (NZCO2EB). The project is made up of eight partners from eight different regions and has a duration of 4 years. Project phase 1 (2016-2018), dedicated to interregional learning, has been completed. This paper summarises the deliverables of project phase 1, with a special emphasis on Malta’s market needs and policy action plans required to ease its transition to NZCO2EB. It is envisaged that in project phase 2 (2018-2020), the priority policy action plans identified in this paper will be implemented. This will enable Malta to reduce its operating CO2 emissions from buildings, while assisting the country to reach its 2020 energy efficiency (EE), renewable energy (RE) and nearly zero energy in building (NZEB) targets.peer-reviewe

Optimising mechanical ventilation for indoor air quality and thermal comfort in a Mediterranean school building

The growing concern over indoor air quality (IAQ) and thermal comfort in classrooms, especially post-COVID-19, underscores the critical need for optimal ventilation systems to bolster students’ health and academic performance. This study explores the potential for improving indoor air quality and thermal comfort in the most energy- and cost-optimal manner using a demand-controlled ventilation (DCV) system coupled with a carbon dioxide control sensor. This is achieved through precooling via night purging in summer and by introducing warmer corridor air into the classroom in winter. The methodology employs both computer simulation and a real-world case study. The findings reveal that while natural ventilation in winter can achieve IAQ standard (EN 16798-1) thresholds for classrooms under favourable outdoor conditions, it results in uncontrolled and excessive energy loss. The retrofitted DCV system, however, maintained CO2 levels below the recommended thresholds for at least 76% of the year depending on classroom orientation and only exceeded 1000 ppm for a maximum of 6% of the year. This study also indicates that utilising the external corridor as a sunspace can further enhance the system’s efficiency by preheating incoming air. This comprehensive study highlights the significant potential for integrating mechanical and passive solutions in school ventilation systems. This contributes to the attainment of the United Nations Sustainable Development Goal 11 and ensures healthier and more energy-efficient learning environments that benefit both students and the environment.peer-reviewe

A novel approach to determine multi-tiered nearly zero-energy performance benchmarks using probabilistic reference buildings and risk analysis approaches

The Energy Performance of Buildings Directive (EPBD) mandates European Union Member States (MS) to conduct cost-optimal studies using the national calculation methodology (NCM), typically through non-calibrated asset-rating software. Nearly zero-energy building (NZEB) levels must be derived for each chosen Reference Building (RB), which are generally defined using deterministic parameters. Previous research proposed an innovative cost-optimal method that replaces ‘non-calibrated deterministic RBs’ with ‘probabilistically Bayesian calibrated reference building (RB)’ to better handle building stock uncertainties and diversities when deriving benchmarks. This paper aims to develop a framework to address two research gaps necessary for the successful application of the innovative cost optimal method: (1) providing objective criteria for defining NZEB benchmarks and (2) propagating uncertainties and financial risk for each defined benchmark. A robust approach for defining NZEB benchmarks according to four different ambition levels (low, medium, high, and highest) was developed by objectively considering distinct points from multiple cost-optimal plots employing different financial perspectives. Risk analysis is then performed for each defined benchmark by propagating risk from the posterior calibration parameter distributions to visualize and statistically quantify the financial risk, including robust risk, that the private investor could face for reaching each derived benchmark ambition level. The innovative cost-optimal methodology that incorporates the developed framework was applied to a hotel RB case study. The results showed that the developed framework is capable of deriving distinct benchmarks and quantitatively uncovering the full financial risk levels for the four different renovation ambition levels. The current cost-optimal method was also performed for the hotel case study with the RB defined determinitically and using the non-calibrated NCM software, SBEM-mt v4.2c. It was found that the financial feasibility and energy-saving results per benchmark are significantly more realistic and transparent for the proposed innovative cost-optimal method including a better match between the simulated and metered energy consumption with a difference of less than 1% in annual performance. Thus, the performance gap between calculated and actual energy performance that is synonymous with the EPBD methodology, as reported in the literature, is bridged. The case study also showed the importance of the risk analysis. Performing the cost-optimal analysis for a Bayesian calibrated RB using the mean value of the posterior calibrated parameter distributions without propagating uncertainty produced highly optimistic results that obscured the real financial risk for achieving the higher ambition levels of the NZEB benchmarks. Consequently, the developed framework demonstrated a time-bound tightening approach to achieve higher energy performance ambitions, improve risk transparency to private investors, and facilitate more targeted policies towards a net zero-carbon status. Thus, the proposed method considering parameter uncertainty and calibrated RBs is instrumental for devising robust policy measures for the EPBD, to achieve a realistic and long-lasting sustainable energy goal for European buildings.peer-reviewe

Exploitation of indoor illumination for typical flat dwellings in the Mediterranean area

The 2018/844 Energy Performance of Buildings Directive (EU) has widened the scope of appropriate design of buildings from a pure energy performance and carbon emissions perspective to a wider scope that includes indoor comfort, and indoor air quality among others. To this effect, external parameters, especially solar energy, have a strong impact on the energy performance of buildings in Mediterranean regions, which requires careful consideration when it comes to benefiting from natural lighting while avoiding solar overheating. This paper addresses the considerations of natural lighting in the deep renovation of a housing block in the Mediterranean climate of the Republic of Malta, comparing some of the usual illuminance ranges to achieve optimal conditions based on international recommendations. DesignBuilder v7.0.0.102 has been the selected software to model the building that has been calibrated through experimental measurements. The model enabled the natural lighting conditions in the building evaluated and the effectiveness of suggested improvements to be determined. Results pointed out that the building under study satisfies the international standards about the prevention of visual discomfort only. Increasing the size of windows in identified zones, especially the first floor, was found to help improve other natural lighting characteristics. One of the proposed designs (Model 6) that replaces single-glazed with double-glazed windows that include an external spectrally-selective coating would significantly improve access to natural light bringing the building closer to the recommended levels of Annual Sunlight Exposure and reducing artificial lighting usage by up to five times. The relocation of room spaces could also reduce the use of artificial lighting.peer-reviewe