On the Limits of the Quasi-Steady-State Method to Predict the Energy Performance of Low-Energy Buildings

The recent European energy policies progressively introduced more restrictive energy performance requirements aimed at achieving the nearly zero-energy building target for all new buildings and major renovations. To check compli-ance with these requirements, the building energy performance can be evaluated through different calculation methods, as widely presented in literature. The pre-sent article is aimed at identifying in which boundary conditions (e. g. climate, use category, building size, thermal insulation level) a simplified steady-state calculation method can predict with sufficient accuracy the energy performance of low-energy buildings if compared with a dynamic simulation model. The anal-ysis was performed on two building types, representative of the Italian residential typology, located in three different climatic zones and characterised by two insu-lation levels. The insulation levels fit the U-values of the notional reference build-ing, established by the Italian legislation for checking compliance with energy performance requirements in two different steps; the first level is in force until 2020, while the second level is that of a reference nearly zero-energy building in force from 2021 onwards. The building energy performance, in terms of net en-ergy needs for space heating and space cooling, was assessed by means of both the monthly calculation method of CEN standards and the detailed simulation model of EnergyPlus. Consistency options were applied to the models to guaran-tee that their outputs could be comparable. The quasi-steady-state method demonstrated to predict the cooling energy need quite well, but to lose in accura-cy when the weight of the thermal transfer in the energy balance increases

The Energy Performance Assessment of nZEBs: Limitations of the Quasi-Steady State Approach

The European Directive 2010/31/EU on the energy performance of buildings (EPBD recast) establishes the target of nearly Zero Energy Buildings (nZEB) for all new buildings and major renovations of existing buildings by the end of 2020. This paper investigates the accuracy of the quasi-steady state method, according to the Italian technical specification UNI/TS 11300, in predicting high performance buildings’ energy consumptions. Both the terms of the building energy balance and the simplified dynamic parameters are assessed by comparing the simplified model with dynamic numerical analysis. The two calculation models are applied to some real low energy buildings, which are representative of the Italian building stock. The envelope U-values are assumed as complying with Italian official nZEB requirements. Weather data from some Italian locations, two inertial mass configurations and different system operating chedules are considered. The comparison between the dynamic and static calculations for low energy buildings’ energy performance assessment reveals some discrepancies: the quasi- teady state model generally overestimates the energy need for space heating and underestimates the energy need for space cooling; the gaps are bigger among various Italian locations and inertial mass configurations than among different system operating schedules. The reasons of this gap are discussed in the paper. It is highlighted that in some particular cases the national regulations should introduce the dynamic numerical analysis as reference calculation model

Refurbishment of the residential building stock toward the nearly-zero energy target through the application of the building typology

Directive 2010/31/EU requires since 2019 the new public buildings and since 2021 all the new buildings to be nearly zero-energy (nZEB). In Italy, as in many geographical contexts, the existing buildings represent the majority of the building stock and equally the largest and most cost-effective energy saving potential. This study presents the energy performance calculations carried out by means of quasi-steady state method for some Italian reference buildings refurbished into nZEB. The results are presented in terms of “packages of measures” and potential energy reductions. The differences among measures depending on building type and climatic conditions are discussed

The Rebound Effect after the Energy Refurbishment of Residential Buildings towards High Performances

In the last decades, governments worldwide have promoted energy efficiency improvements in order to reduce the building energy consumptions and CO2 emissions. In many geographical contexts, the largest and most cost-effective energy saving potential is in the existing housing stock renovation. For this reason, many energy efficiency policies are focused on the energy refurbishment of the existing buildings. Though the energy consumption of buildings is supposed to decrease after a retrofit, several studies show that the energy performance does not increase as much as it would be expected and that a significant gap between the estimated and the real energy savings - called rebound effect - occurs. This deviation can partly depend on the model used for the energy performance evaluation, but changes in the occupants’ behavior after a thermal retrofit of an existing dwelling are also revealed. The present paper examines the influences of occupant behavior on the energy savings for some retrofitted Italian residential representative buildings. Some typical use patterns are defined according to statistics of the national census of population and dwellings and the expectations of the building occupants are specified before and after the retrofit. The main objective is to investigate the elasticity of the energy consumption in function of the occupancy parameters before and after the application of high energy efficiency improvements. The analysis is carried out by means of a simplified energy performance assessment model. The outcomes of this study consist in defining synthetic indicators for the quantitative assessment of the rebound effect

Diversidade genética de actinobactérias utilizando BOX-PCR e REP-PCR

Os microrganismos apresentam um importante papel na produção de compostos de interesse para a indústria farmacêutica. Estudos em biologia molecular apontam o potencial de produção de metabólitos secundários por bactérias do gênero Streptomyces. São microrganismos Gram positivos distribuídos em diferentes ecossistemas terrestres e aquáticos e de difícil identificação, em vista disso, as técnicas mais modernas de identificação baseiam-se no sequenciamento da região 16S do DNA ribossomal, porém, sem uma discriminação exata entre espécies relacionadas. Técnicas de DNA fingerprint vêm sendo aplicadas para resolver questões de identificação dos diferentes microrganismos e a aplicação de primers específicos a certas regiões fornece padrões de amplificação que se mostram eficientes à identificação de uma gama de organismos. As técnicas de fingerprint BOX-PCR e REP-PCR empregam primers com elementos repetitivos, gerando padrões de bandas característicos a cada amostra, utilizado como forma de identificação de cepas bacterianas. O presente trabalho objetivou observar diversidade genética dos isolados de actinobactérias coletados em solo antártico, utilizando a técnica BOX-PCR e REP-PCR. Foram comparados os perfis de amplificação de 49 amostras e 36% destas agruparam-se com similaridade superior a 90% em ambas reações. Também se observou a presença de um fragmento de tamanho comum nos isolados analisados com o primer BOX-A1R

The significant imbalance of nZEB energy need for heating and cooling in Italian climatic zones

Building energy performance requirements aiming at the nZEB target have been recently established by the national legislation. In Italy, the requirements are verified through the notional reference building, whose U-values are reduced in two steps: up to 2018 and since 2019 for public buildings, and up to 2020 and since 2021 for all other buildings. This might cause a reduction of the heating need but an increase of the cooling need. The objective of the study is to investigate in which conditions and extent a significant imbalance of the energy needs occurs. Different building types and climatic zones are considered

Application of Dynamic Numerical Simulation to Investigate the Effects of Occupant Behaviour Changes in Retrofitted Buildings

The term rebound effect is commonly used in literature to identify the gap between the estimated and the real energy savings due to changes in the occupant behaviour after a building energy retrofit. In the present article, the rebound effect for some Italian residential building types is investigated through dynamic simulation. The energy efficiency measures determining the highest rebound effect are identified and discussed. The results point out that the major renovation generally leads to the highest benefits as the efficiency measures are mutually reinforced. In contrast, single measures may lead to the opposite goal of increasing the energy consumption

Temporal variation of bacterial population and response to physical and chemical parameters along a petrochemical industry wastewater treatment plant

The petrochemical industry has played a considerable role in generation and release of waste in the environment. Activated sludge and facultative lagoons are commonly used for domestic and industrial wastewater treatment due to their low-cost and minimal need for operational requirements. Microorganisms present in wastewater treatment plant (WWTP) are responsible for most nutrient removal. In this study, microbiological and physicochemical parameters were used to estimate changes in bacterial community in a petrochemical industrial WWTP. The activated sludge was the place with higher heterotrophic bacterial quantification. Denitrifying bacteria was reduced at least 5.3 times throughout all collections samples. We observe a decrease in the total Kjeldahl nitrogen, oxygen demand and phosphate throughout the WWTP. In this work, we also use Matrix-Assisted Laser Desorption Ionisation-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for bacteria isolates identification comparing with 16S rDNA sequencing. The MALDITOF MS allowed the identification of 93% of the isolates and only 5% show different results from 16S rDNA sequencing showing that the MALDI-TOF MS can be a tool for identifying environmental bacteria. The observation of microbial community dynamics in the WWTP is important in order to understand the functioning of the ecological structure formed in a specific environment