Interfacing a solar photovoltaic system with the national electricity grid in Malta

A 1.8 kWp grid-connected solar photovoltaic system is being monitored at the Institute for Energy Technology, since June 1996. The average performance ratio for 22 months of operation was found to be 0.715, which translates to a final yield of 3.44 kWh/kWp/day. The average final efficiency was found to be 7.6%. These values exclude the month of October 1997, during which the system was not operating. Problems encountered, relating to the interface between the electric utility grid and the PV system are discussed.peer-reviewe

Lifestyle trends for heating and cooling in Maltese households

According to the EU Directive 2009/28/EC Malta is obliged to reach a 10% renewable energy share of the total final energy consumption by the year 2020. Due to the challenging targets, Malta seems to be finding it hard to achieve the agreed trajectories. Renewable energy applications in an island state like Malta are hard to achieve due to various constraints, including: lack of space, multiple land-uses and land-use conflicts, few natural resources, low social acceptance, lack of financial resources, lack of expertise, and lack of capacity building. Hence, it would be more feasible to also focus on energy efficiency in buildings which is one of the major consumers of energy on the island. More than 30% of the energy production in Malta is used by buildings, including households. Primarily, this is where the authorities lack information, in the light of heating and cooling of air and water heating in buildings. This paper investigates the status-quo of existing lifestyle trends for space heating and cooling, and water heating, in Maltese households. The scope is to evaluate the potential of shifting to more energy efficient systems that can positively contribute towards the decline of energy consumption in houses, and thus indirectly help to attain the renewable energy targets set for year 2020 and beyond. Energy behaviour and attitudes of Maltese citizens have also been analysed.peer-reviewe

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

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

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

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

Contribution of solar applications towards achieving a renewable energy target for Malta

Based on applied research and demonstration activities carried out during the past decade at the Institute for Energy Technology, solar photovoltaic applications offer a good prospective towards achieving a significant percentage of Malta’s electricity needs. This paper summarises the most important conclusions reached, describes the current installed systems in Malta, sets the achievable targets and discusses the challenges that face the widespread applications of this technology. Moreover, consideration is given to the widespread applications of solar water heating systems and their contribution towards lowering electricity consumption.peer-reviewe

Statistical analysis of particulate matter data in Doha, Qatar

Pollution in Doha is measured using passive, active and automatic sampling. In this paper we consider data automatically sampled in which various pollutants were continually collected and analysed every hour. At each station the sample is analysed on-line and in real time and the data is stored within the analyser, or a separate logger so it can be downloaded remotely by a modem. The accuracy produced enables pollution episodes to be analysed in detail and related to traffic flows, meteorology and other variables. Data has been collected hourly over more than 6 years at 3 different locations, with measurements available for various pollutants – for example, ozone, nitrogen oxides, sulphur dioxide, carbon monoxide, THC, methane and particulate matter (PM1.0, PM2.5 and PM10), as well as meteorological data such as humidity, temperature, and wind speed and direction. Despite much care in the data collection process, the resultant data has long stretches of missing values, when the equipment has malfunctioned – often as a result of more extreme conditions. Our analysis is twofold. Firstly, we consider ways to “clean” the data, by imputing missing values, including identified outliers. The second aspect specifically considers prediction of each particulate (PM1.0, PM2.5 and PM10) 24 hours ahead, using current (and previous) pollution and meteorological data. In this case, we use vector autoregressive models, compare with decision trees and propose variable selection criteria which explicitly adapt to missing data. Our results show that the regression tree models, with no variable transformations, perform the best, and that attempts to impute missing values are hampered by non-random missingness

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