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The paper deals with the multi-objective optimization of the HVAC control in museums. Scientific literature, technical standards and museums stakeholders mainly focus on the single-objective of artefacts conservation. However, a major attention should be paid at visitors' comfort and energy consumption, without compromizing artwork integrity. In this work, we propose and apply a methodology to find the best control of the air-handling unit to concurrently optimize the three objectives. The proposed methodology is based on the achievement function method and finds the Pareto-optimal value of the HVAC control variables over the operational period. The priority given to each objective can be customized by changing the reference point of the achievement function. The method is applied to a museum in Italy hosting paper artworks during summer. Both exhibition room and HVAC system are simulated through an in-house dynamic model. The results show that all three objectives are improved with respect to typical fixed setpoint values (i.e., T = 23 °C and RH = 50%). Depending on the reference point, different profiles of indoor hygrothermal parameters are found; in any case, improvements of each of the objective functions indexes (equivalent lifetime multiplier for artwork preservation, predicted percentage of dissatisfied, and energy consumption) are obtained with respect to fixed setpoint strategy. The multi-objective optimization of museums with paper artworks in summer periods encourages low indoor temperatures. This would lead to slightly increased energy consumptions, which can be limited, by reducing the ventilation rate to 3–3.5 1/h instead of the typical 4–5 1/h. • The multi-objective methodology optimizes museums HVAC control in each timestep. • Objective functions are artwork preservation, visitors' comfort, and energy saving. • Objectives priority is chosen by changing the optimization reference point. • All objectives are concurrently improved with respect to fixed-setpoint strategies. • A case study compares different control strategies and objectives priorities. [ABSTRACT FROM AUTHOR]

• Replacement of thermal generator is a simple and efficient building retrofit action. • Three generators are compared using environmental, energy and economic metrics. • A building stock energy model for Italy has been defined (4 buildings, 3 climates). • Heat pumps are preferrable for emission reduction, but lead to high operative costs. • The flexibility of hybrid heat pump allows for high savings on all the objectives. In many countries, old inefficient generators are used for heating purposes. A way to improve energy efficiency in those countries can be the choice of the most suitable heating generators to replace the current ones, without the inconveniences caused by other retrofit measures. In this context, we present a methodology to choose the most appropriate generator through dynamic simulations applied to building stock energy models. Economic, energetic, and environmental parameters guide the choice. The methodology is applied in the Italian residential building scenario, where the most widespread heating device is traditional boiler. Three options are considered: condensing boiler, heat pump, and hybrid heat pump (an alternative-working system with a condensing boiler and heat pump). For a detailed analysis, a white-box bottom-up building stock energy model is defined, through a statistical analysis, consisting of four building typologies in three different external climates. An hourly dynamic building-system simulation has been performed to obtain energy performance, emissions, and operational costs. The results have demonstrated that condensing boiler allows limited economic, environmental, and energy savings (8 - 14 %), compared to traditional boiler. The highest economic savings are obtained with the hybrid heat pump (20 %), while the heat pump alone leads to higher costs, but the highest savings in emissions and non-renewable primary energy (25 - 50 %). The flexibility offered by the hybrid heat pump allows to obtain high savings in different cost scenarios, but also to further reduce CO 2 emissions by implementing an environmental-based control strategy. [ABSTRACT FROM AUTHOR]

The scientific literature lacks methodologies for assessing HRES investments because of complex interactions among HRES components, conflicting objectives, and uncertainty in the energy demand. This work fills this gap by presenting a methodology to assess long-term investments in HRES for off-grid buildings. To strengthen the reliability of the assessment, the methodology exploits an HRES optimal synthesis, sizing and operation simulating the system and embodying the interactions among HRES components for both electrical and heat generation, the building loads evaluation, and the verification of the effect of uncertainties in the energy demand. These aspects have already been investigated, but, to our best knowledge, have never been considered in a concurrent and integrated way. The resulting designs are optimised through an NSGA-II algorithm that minimises the system CO 2 emissions and differential cost with respect to a solution that does not use renewable energy sources. The soundness of the solutions is evaluated through a scenario analysis and a sensitivity analysis using the Morris method. The applicability of the proposal was verified through a case study in an off-grid facility, showing possible savings up to 47 k€ and 320 t CO 2. The methodology is thus strongly consistent with the building decarbonisation addresses set by the policymakers. • The methodology optimises HRES synthesis, sizing and control in off-grid building. • The methodology is applied to a case study of a farm hostel in Italy. • The Pareto frontier is created considering environmental and economic aspects. • Five optimal solutions are analysed, distinct for total costs and caused emissions. • Scenario and sensitivity analyses corroborate the robustness of the solutions. [ABSTRACT FROM AUTHOR]