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Social housing buildings, throughout Europe, represent a consistent share of the existing building stock. Due to the increasing levels of urbanization, the social housing population in the cities has risen and, after the economic crisis following the subprime mortgage crisis and the pandemic, low-income families as well. The greatest part of social dwellings, those built in the previous century, is usually sub-standard from an energy and environmental point of view. This study reviews the existing literature documenting indoor environmental conditions and energy refurbishment interventions or programs to improve the energy efficiency of existing social buildings. By considering the high risk of energy poverty in social contexts, and the socio-economic conditions of tenants, the economic implications deriving from the energy retrofit were also evidenced. Relevant papers published between 2010 and 2024 were reviewed and were divided according to the reference scale, namely the building or the district scale. The review shows the need to improve the energy performances of social dwellings, both to reduce their energy demand and to improve the indoor microclimatic conditions and quality of life of tenants. Through a critical literature review approach, this study provides a contribution to the in-depth understanding of the role of social housing in the contemporary context, providing meaningful insights for formulating more effective and inclusive housing policies for the next future. [ABSTRACT FROM AUTHOR]

HVAC systems in buildings are composed of many subcomponents which consume energy in huge amounts. In recent years, energy consumption becomes very important aspect due to the lack of energy resources and environmental reasons. In terms of energy consumption, the components of HVAC systems account for large portion of total energy used in buildings. Therefore optimization of energy consumption in HVAC applications is an essential requirement in terms of thermodynamic and economic point of views. Besides, the efforts for decreasing energy consumption turn into economic recovery. It also provides benefits for human health and cleaner environment. In this paper, as originality, thermodynamic and economic analyses of an existing social and cultural building which has a heating and cooling area of 8852 m 2 are presented by comparing of a conventional HVAC and a VRF system. A novel contribution is given to the open literature by comparing two systems with actual data measured from the existing system. The other originality is to apply and test a VRF system to a complex-structured building. This study is a rare one which contains insulation, heating and cooling accounts of a building together. In this paper, VRF system is modelled to the existing building for the comparison of the conventional HVAC system. Both systems have been compared in terms of heating and cooling capacity, initial, operation and maintenance costs. It is found that the VRF system is more economic and efficient such that the VRF system is found to have 44% cost profit when compared with the conventional HVAC system. [ABSTRACT FROM AUTHOR]

Due to the lack of conventional energy and fragile ecological environment in the Tibet Plateau at an elevation of over 3000 m, renewable energy utilization is of great significance in environment protection and energy conversation. A field measurement of a groundwater source heat pump (GWSHP), a part of a solar assisted GWSHP heating system of an airport in the Tibet Plateau with the side of solar collectors broken down was conducted in this paper. Meanwhile, the indoor thermal environment in the terminal and dormitory heated by radiant floor was measured. The performance, economy of the GWSHP and indoor thermal environment were analyzed. At last, a comparison between the GWSHP and other heat pumps used in this region was made. The results showed that the coefficient of performance (COP) is about 5.0. Compared to conventional heat sources, the performance of the GWSHP is optimal in regard to both energy conservation and economic efficiency. There was a significant difference observed between the thermal environment in the terminal and dormitory. Accordingly, design considerations and regulation measures are recommended to improve the thermal environment. Compared with heat pumps used for heating in the Tibet Plateau so far, the GWSHP in this paper is better. [ABSTRACT FROM AUTHOR]

This paper aims to provide the current state of the art of solar sorption systems. Through comprehensive literature review of solar sorption systems, it was concluded that these technologies have several limitations and drawbacks. The low performance and the high cost are the main disadvantages of these technologies. However, solar cooling is considered attractive because solar radiation is in phase with the demand for cooling. Due to its attractiveness, the research is still going and focusing on solving the technical, economical, environmental problems, to achieve high performance and low cost of solar sorption systems. Improvements through investigating geometrical, system configurations, physical parameters, and operational modes on the performance of solar thermal sorption cooling systems are presented. A survey of the new configurations, novel additions, new techniques, new methodologies are also presented in this paper. Several cases studies in different climatic conditions are summarized. Economic feasibility for absorption and adsorption systems is discussed. It can be concluded that cost and energy effective solar sorption systems can be developed if suitable combinations of system components with operating conditions are selected. Finally, there is still the need for more research on solar sorption systems to make them both cost and energy competitive with the conventional cooling technologies. [ABSTRACT FROM AUTHOR]

• An optimization strategy model of district energy system under the direct reduction/increase goal of power load is presented. • The grid can directly control the energy consumption strategy in the form of instructions. • The proposed goal pays a certain price, but a large additional flexible utilization coefficient is obtained. • The energy compensation coefficient of the multi energy coupling system is mostly negative. With the wide application of regional centralized cooling (heating) system in the world and the growing maturity of energy supply technology, the focus of system optimization gradually transforms from technical optimization to strategic optimization to attain the common goals of economy and energy saving. Aiming at the operation strategy model of power grid interactive district energy system based on time-of-use (TOU) price proposed in previous research, this paper proposes new objective equations and constraints to explore the strategic deployment of district energy system when accepting the power grid requirements to reduce or increase the power load directly to improve the economy and energy efficiency of centralized cooling (heating) system. The modified optimization strategy model is used to respond to sudden demand response or power accidents. The strategy model can be directly controlled by the power grid, and the TOU price is no longer the main factor affecting the formulation of the strategy. In the face of sudden demand response or power accidents, the operation strategy optimization model proposed in this paper can guarantee the energy supply demand of users and optimize the economic benefits and energy efficiency of the systems. The operation strategies under various optimization objectives can be obtained through the simple input of energy loss of the pipeline and user cooling or heating load. The proposed model is suitable for the load allocation of energy system with single energy supply form and for the strategy optimization of multi energy coupling system. The accuracy and validity of the proposed model under various optimization objectives are verified based on experiment and simulative research. [ABSTRACT FROM AUTHOR]

Abstract: Photovoltaic (PV) connected systems are experiencing rapid market growth. This is due to the continually downward trend in PV cost together with government support programs. A scenario has been assumed to analyse the geographical market of PVs. The results provide clear evidence of the influence that some variables have on the profitability of PV investments. This study presents a model for minimising investment risk and maximising the return of a renewable energy portfolio in Italy. The value of the paper is in showing that the energy and CO2 reduction potential that can be reached through consumer-oriented policy measures, but the paper also looks at the effectiveness and social implications of such measures. Private households possess immense unused potential for energy reductions (and climate protection) that could be realised through gains in energy efficiency, behavioural changes, and extended use of low-emission energy. The focus of energy policy has been on businesses rather than on private households, which are only partly captured by direct policy measures. To achieve the goals of climate policies, the current political and scientific discussion increasingly considers measures that aim to reduce energy consumption in the private sector. Quantitative estimates are presented for economic indicators and will show the various effects of policy measures on the implemented household types. [Copyright &y& Elsevier]

Abstract Real-time power supply and demand balances are critical to ensure stable power frequency and quality power services. However, the growing integration of renewable energy increasingly challenges the power infrastructure because most of the renewable resources, e.g., solar and wind energy, are intermittent and difficult to predict. To meet stringent power frequency requirements, more fast reacting frequency regulation resources are being brought online among which grid-level batteries are the dominant ones. Buildings consume more than 73% of the electricity in the US, offering significant regulation reserve for the power grid. Variable-speed air-conditioning and heat pump systems are taking an increasing share of the market due to higher efficiency requirements imposed by federal agencies. In addition to efficiency benefits, variable-speed cooling/heating systems are also perfectly suited to provide frequency regulation service since these units can modulate their power continuously over a wide range. This paper presents a methodology and case study results for laboratory-based assessments of power frequency regulation service performance for variable-speed HVAC cooling equipment. The assessment methodology involves the use of both open- and closed-loop testing in psychrometric chambers. The open-loop testing quantifies the maximum possible performance of regulation services that is building independent, whereas the closed-loop testing provides representative performance for regulation services when the equipment must maintain comfort conditions for typical "virtual" buildings. Two air-conditioning units, a variable-speed packaged rooftop unit (RTU) and a split heat pump with an after-market variable-speed retrofit, were utilized for regulation tests performed in psychrometric chambers. Both open-loop and closed-loop regulation control strategies were developed and tested for this equipment. Open-loop test results showed that variable-speed HVAC equipment can provide high quality regulation service with performance scores of up to 0.98. With PJM historical wholesale energy and regulation prices, the estimated regulation credit can offset up to 48% of the electricity price. The closed-loop regulation control was shown to have negligible impact on indoor comfort with temperature fluctuations smaller than 0.1 °C. Power regulation also did not cause any efficiency degradation for the closed-loop tests. In fact, for more humid climate conditions, the electrical input for cooling can even be reduced with regulation control due to reduced moisture removal. [ABSTRACT FROM AUTHOR]

This paper presents a lighting control system based on natural light monitoring and on occupancy control, characterized by installation easiness, even for existing plants, and cheapness. The system is based on a smart control unit and lighting control devices that can be directly mounted on the lamps in series connection. The installation is noninvasive and does not require any changes in the wiring system, since the communication between each lamp and the control system is realized by means of a 2.4 GHz wireless protocol. The system functionality is ensured with any lamps, also with non-dimmable ones. Tests and functionality verifications on the system were performed in laboratory, proving the applicability to real cases and performances that are comparable to the ones achievable with dimmable LED lamps, but with a significant cost saving. Hypothesizing the application of the proposed system and of different control technologies and strategies to a real academic classroom case study, different lighting scenarios have been simulated. Obtained results allow quantifying the effects in terms of energy consumption and CO 2 emissions relative to such scenarios, achieving up to 69.6% of energy saving and 30.5% of CO 2 emissions avoided. From an economic point of view, the comparison between the proposed control system and commercial systems shows a shorter PayBack Period, from 9 to 5 years. [ABSTRACT FROM AUTHOR]

The application of retrofit actions to existing building stocks can improve the energy performance of the residential sector. In this context, particular attention should be given to historical buildings, which represent a large part of the Italian building stock. To improve the energy performance of them, adequate retrofit actions must be applied. Many studies and regulations have focused on identifying the best refurbishment measures. However, the selection of these measures is difficult due to restrictive regulations, which are dictated by the Ministry of Cultural Heritage and Activities, high retrofit costs, and variable climate zones. Thus, energy renovations in Italian buildings are not simple, and it is very difficult to find generic solutions that can be applied to buildings across the entire territory. In this paper, the authors investigated the most common retrofit solutions used in Italy, focusing in particular on the energy performance of historical building envelopes. First, energy performance analyses were conducted for two typical base cases in four different Italian cities using TRNSYS software, and some common retrofit measures were analysed. In some cases, the results showed Primary Energy saving of 44.6% (sample A) and 56.7% (sample B). Furthermore, these were used to identify different energy and economic impacts associated with the same refurbishment measures in different climatic contexts, highlighting the non-existence of a generic solution suitable for all regions or countries. [ABSTRACT FROM AUTHOR]

Using phase change material (PCM) into the building envelope is considered an effective thermal energy storage strategy to improve building thermal performance and reduce space heating/cooling loads. However, different phase transition temperatures and climatic conditions have a huge impact on application effect. This paper investigates the effects of walls containing PCM foamed cement on thermal performance and economy of single-story building in 5 different climate zones in China. The temperature, energy storage, energy consumption and the payback period for PCM foamed cement wall are analyzed by numerical simulation. The results indicate that the PCM foamed cement moderates the indoor and outdoor temperature differences in all 5 climate zones. Among which, Harbin (severe cold region) had the best increase in the south wall inner surface average temperature in January with an increase of 0.378 °C. The optimal phase transition temperature is close to the local annual average temperature except Harbin, and the energy saving rates are 20.17 % (Beijing), 15.87 % (Shenzhen), Shanghai(22.26 %), 37.02 % (Kunming). The shortest payback period is 5.95 years for the application of PCM foamed cement in Harbin, but in Kunming (mild region) at the current price, the investment cannot be recovered. [ABSTRACT FROM AUTHOR]

This paper studies the effects of energy efficiency measures on energy demand in the Krsan Castle, which is a cultural heritage complex in Istria (Croatia). The heating and cooling energy demand is calculated by means of a dynamic building energy model based on hourly weather data. The largest individual reductions are obtained with thermal insulation for the heating demand, and with external window shading and natural night ventilation for the cooling demand. Energy reductions of up to 80%, relatively to the existing state, can be achieved by energy retrofit projects which include thermal insulation, energy efficient windows, improved airtightness, mechanical ventilation with heat recovery and passive cooling techniques. The economic analysis revealed that payback periods between 10 and 16 years can be achieved by this kind of energy retrofit projects. [ABSTRACT FROM AUTHOR]

• An air conditioning system with thermoelectric modules is analysed and optimised. • Cooling investment and operating costs are discussed. • Heat exchangers are optimised based on economic indicators. • The economically optimised air conditioning system can be significantly overloaded. • TEC air conditioning is expensive but quiet, compact and environmentally friendly. The paper presents simulations of an air conditioning system based on thermoelectric modules. The proposed system is of a very simple structure, easy to control, scalable, noiseless, and harmless to the environment. The most important parameters that were to be changed were the number of modules, the electric current, and the size of the heat exchangers. The analyses were carried out for a commercially available thermoelectric module whose parameters were determined experimentally. The air conditioning system was analysed in terms of its cooling capacity and COP. Furthermore, it was optimized with economic criteria to achieve the highest cooling capacity of 1 dollar of total cost (electricity and investment) in a set period of device lifetime (ETCC – economic total cooling capacity). For 2400 h of device operation, at a temperature difference of 5 K and the average electricity cost in the EU, the optimized ETCC totals about 0.58 W/$. With the possibility of altering the inner geometry of the thermoelectric modules, the factor increased to 0.64 W/$. The test results showed that the device optimized in terms of ETCC did not operate with maximum cooling power and could be overloaded by about 30% in the reference working conditions. [ABSTRACT FROM AUTHOR]

Traditional air conditioning and heating systems in buildings are fossil fuel based energy systems, which take the main responsible for the carbon emissions. In contrast, using solar energy for air conditioning becomes one of the promising approaches to reduce energy consumptions and negative environmental impacts from buildings. University of California, Merced built a test facility to investigate the technology: solar cooling. The solar system has 54 m 2 external compound parabolic concentrator (XCPC) solar collectors to drive a 23 kW double-effect absorption chiller. This paper first provides the detailed energy performance analysis of the experiments conducted in August, 2012. The data collected from the experiments shows that the system could provide adequate cooling for a test facility between 11AM to 5PM in both sunny and cloudy days. The daily average collector efficiency is at the range of 36% to 39%. The average coefficient of performance (COP) of the LiBr absorption chiller is between 0.91 and 1.02 with an average of 1.0, and the daily solar COP is approximately at 0.374. In addition to the experimental investigation, a detailed life cycle economic and environmental assessment was also performed by comparing the solar systems to the conventional systems in two types of office buildings at three locations at California. Two different solar cooling system configurations were considered: (i) configuration 1 sizes the area of solar collectors and absorption chiller to meet the peak cooling demand, and uses natural gas as the only backup energy source; (ii) configuration 2 sizes the area of solar collectors and absorption chiller to meet half of the peak cooling demand, and uses natural gas as the backup energy source for the absorption chiller, while incorporates an electrical vapor compression chiller to meet the rest half of peak cooling demand. The annual performance predicts that the systems can achieve the annual solar fraction around 55–68%. And the configuration 2 achieves better life cycle economic and environmental performance than the configuration 1. Specifically, the configuration 2 can achieve lower present worth cost during the entire life span than the conventional systems. And both configuration 1 and 2 can reduce the life time carbon footprint by 35–70%. [ABSTRACT FROM AUTHOR]

Abstract: The age of European existing building stock and the very low growth rate make energy retrofit a critical issue at the moment. The spreading of good practices is strongly hampered by their cost effectiveness. National legislation thermal requirements for retrofitting works play a fundamental role. If they are too strict, the initial economic investment could be too high if compared with energy savings achievable. The paper refers to a case study of improving fabric thermal performance of stone masonry buildings located in Cagliari – Italy. They were built in 1950s. The economic feasibility of different energy efficiency retrofits is evaluated. Two different scenarios are analyzed: the former according to the earlier Italian legislation (valid from 2006 to 2008), the latter according to the latest and strictest measures (valid from 2010). The results show that heavy thermal performance upgrades, even though compulsory, are not completely cost-effective in a mild Mediterranean climate area as far as payback time is concerned. National subsidy policies can improve the economic return on the investment. The impact of present Italian incentives has also been evaluated. [Copyright &y& Elsevier]

Abstract: A water-cooled chiller system in an air-conditioned hotel can take up about one-quarter of the total electricity consumption and considerable amounts of water in the heat rejection process. This paper evaluates operating cost savings of a chiller system integrated with optimal control of cooling towers and condenser water pumps. A sophisticated chiller system model was used to ascertain how different control methods influence the annual electricity and water consumption of chillers operating for the cooling load profile of a reference hotel. It is estimated that applying load-based speed control to the cooling tower fans and condenser water pumps could reduce the annual system electricity use by 8.6% and operating cost by 9.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point of 29.4°C for cooling water temperature control. The ways to implement this advanced control for system optimization are discussed. [Copyright &y& Elsevier]

• Performance evaluation of GCPV system from monitoring of two years PV productions. • Calculation of PV derating factor from actual PV system output. • Error between simulation and actual performance is reduced using derating factor. • Performance of GCPV system increases 4.8% using optimal tilt angle and orientation. This paper presents the real performance of a 7.8 kWp grid-connected rooftop photovoltaic (PV) system from a field monitoring at a residential house under the feed-in-tariff scheme. The performance parameters of PV system were assessed based on the two-year energy production in 2018–2019. PVsyst software was used to find the best orientation and tilt angle for the selected area to increase the system performance. Next, the PV derating factor was calculated from the two-day data collection. The derating factor was used in the simulation of the system using HOMER Pro, and the economic parameters for 21 years project lifetime were predicted. The results show that the performance of the installed system was better for 2019 compared to 2018 due to the higher solar irradiance in 2019 and the malfunction of inverter in July to August 2018. The best performance ratio obtained from the recorded data was 75.72% and the average loss was 1.68 kWh/kWp/day. The annual capacity factor and overall system efficiency were in the range of 13%–16% and 10%–12%, respectively. The best tilt angle and orientation was 5° with the increment of annual energy production up to 4.8%. From the simulation, the error between the simulation and measurement results was high when the derating factor was assumed to be 100%. When the value used was based on the calculation obtained from data collection, the annual error was 1.7%, which is acceptable. Thus, the software is considered reliable assuming no component failure in the PV system. From the economic analysis, the annual net profit can be obtained was almost RM 3,000, and the payback period was in the range of 5–7 years. In addition, the installed PV system on the single house has the potential to reduce the CO 2 emission of approximately 7.45 tons/year. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the economic feasibility of both building an ice thermal storage and structure a time of rate tariff for the unique air conditioning (A/C) plant of the Grand Holy Mosque of Makkah, Saudi Arabia. The features of the building are unique where the air-conditioned 39,300m2 zone is open to the atmosphere and the worshippers fully occupy the building five times a day, in addition hundreds of thousands of worshippers attend the blessed weekend''s prayer at noontime, which escalates the peak electricity load. For economic analysis, the objective function is the daily electricity bill that includes the operation cost and the capital investment of the ice storage system. The operation cost is function of the energy imported for operating the plant in which the tariff structure, number of operating hours and the ambient temperature are parameters. The capital recovery factor is calculated for 10% interest rate and payback period of 10 years. Full and partial load storage scenarios are considered. The results showed that with the current fixed electricity rate (0.07$/kWh), there is no gain in introducing ice storage systems for both storage schemes. Combining energy storage and an incentive time structured rate showed reasonable daily bill savings. For base tariff of 0.07$/kWh during daytime operation and 0.016$/kWh for off-peak period, savings were achieved for full load storage scenario. Different tariff structure is discussed and the break-even nighttime rate was determined (varies between 0.008 and 0.03$/kWh). Partial load storage scenario showed to be unattractive where the savings for the base structured tariff was insignificant. [Copyright &y& Elsevier]

Increasing the energy efficiency with a vast impact in the residential building stock requires retrofit solutions that can be exploited with respect to a wide range of different building typologies and climates. Several tools and methodologies are nowadays available both for the assessment of building demands and for the individuation of optimum retrofit solutions. However, they are usually either too complex to be adopted by professionals or, on the contrary, oversimplified to account for the full complexity of a deep envelope and HVAC system retrofit. In this context, this paper describes a methodology developed to generate reliable information on retrofit solutions for typical buildings in different climatic conditions. Detailed numerical models are used to simulate a number of combinations of envelope and HVAC systems retrofit measures and renewable energy integration. Energy performance results are gathered in a database that allows comparing solutions, spanning over a range of more than 250,000 combinations of building types, age of construction, climates, envelope performance levels and HVAC systems configurations. Economic feasibility is also derived for each of the combinations. In this way, the accurateness of a detailed and validated calculation is made available to assist during the decision making process, with minimum computational effort being required by professionals: the variety and density of evaluated combinations allows to easily assess the performance of a specific case by interpolating among instances previously assessed. The applicability of the results to different climates and similar building typologies is verified by a comparison of the database results with a specific case dynamic simulation. [ABSTRACT FROM AUTHOR]

The concept of 'Active Building' refers to any building, such as factories, offices, homes, and other structures in the built environment, which are equipped to conserve, generate, store, and release energy in the UK. One such Active Building was built at Swansea University in the UK in 2018 and is currently used as a small office including well fare facilities. The objective of this study is to analyse the economic performance of an Active Building, incorporating building-integrated photovoltaics (BIPV) and lithium-ion (Li-ion) batteries with real building operational profiles and metered energy load profiles. The cost covers the capital cost of 22 kWp BIPV and 110 kWh Li-ion battery, and electricity cost from the electric grid with two types of time of use electricity tariffs - South Wales (SW) time of use tariff and Red, Amber, and Green (RAG) rates, and the potential carbon cost of electricity supplied from the Wales electric grid and generated from the Active Building. Four battery operational strategies are designed, and battery status of charge and electricity flow are monitored. The analysis is undertaken on the BIPV units with or without Li-ion batteries under various scenarios. The results show that the investment of BIPV units without Li-ion batteries can make a profit within the lifetime of BIPV in the current electricity market. However, the current Li-ion battery storage does not compensate for its capital cost from the reduced economic value obtained from the BIPV system when the electricity is curtailed. Even though the current economic analysis of the Active Building installing BIPV and battery is not convincing at the current capital price, this combination can enable the Active Building to be independent of the electric grid and to balance electricity demand and generation itself. The analysis will demonstrate the market conditions required to make these operational benefits cost-effective. [ABSTRACT FROM AUTHOR]