Desired Indoor Temperature Research Articles

Evaluation of a Kirigami-inspired double-skin adaptive façade for natural ventilation and solar harvesting to enhance indoor environment and energy performance

A novel kirigami-inspired design concept for an environmentally responsive adaptive façade is presented and evaluated for the objectives of solar energy harvesting and adaptive ventilation through controllable surface orientation and opening. The concept is a double-skin façade where the outer skin includes a straight cut kirigami-inspired adaptive component. Controllable actuation of the kirigami-inspired section opens the outer skin for ventilation while also changing the orientation of the outer surface for solar tracking. The primary objective of this study is to evaluate the potential benefits for this concept integrated within a building façade for solar energy harvesting, air changes, and indoor temperature control. As such, a computational study is used to estimate the proposed facade concept's performance within various generalized building-environment scenarios. The methodology is detailed to computationally estimate the potential environmental performance of this concept with respect to solar harvesting with adhered solar panels, as well as air changes and HVAC cost for associated interior spaces. The example scenarios include various building components, from a single room to multiple building stories, and two geographic locations with significantly different environmental conditions, and both daily and yearly performance estimates are shown. The component is most effective when the outdoor temperature is near to the desired indoor temperature and wind speeds are mild, but can still reduce HVAC usage for more disparate temperatures. For example, in the scenarios shown the component can eliminate HVAC use for a 5°C difference between outdoor and indoor temperature and reduces HVAC usage for temperature differences up to 15°C. Moreover, the component has the potential to significantly increase net energy generation, with yearly performance estimated for the scenarios to be as much as 25% greater than that of a flat closed façade. However, the component cut parameters can have a significant impact on environmental performance, and thus require careful design consideration.

Evaluating building-level parameters for lower-temperature heating readiness: A sampling-based approach to addressing the heterogeneity of Dutch housing stock

The Dutch government aims to eliminate natural gas for residential heating in 1.5 million homes by 2030. One strategy is connecting existing dwellings to lower-temperature district heating (DH) systems, although these dwellings might require energy renovations. The heterogeneous dwelling stock causes varying renovation needs that complicate the energy transition. The present study addresses this issue by assessing the building-level parameters affecting the readiness of the Dutch terraced-intermediate and apartment types for lower-temperature heating (LTH) supplied by DH systems. A sampling-based approach was employed to capture variability within these dwelling types, addressing the limitations of archetype-based methods. The findings suggest a sample size of 1300 to represent the variations in these dwelling types. Parametric simulations and machine learning methods were used to identify significant building-level parameters for medium-temperature (MT: 70/50 °C) and low-temperature (LT: 55/35 °C) supply levels. These include heating setpoints (desired indoor temperature) and ventilation-related parameters (ventilation system type and air infiltration rate), followed by fabric-related parameters (roof, glazing, wall, ground, and door insulation) and geometric properties (orientation, compactness ratio, and window-to-wall ratio). Additionally, radiator oversizing also impacts LTH readiness. These results broadly apply to the studied dwelling types, although feature importance varies by supply temperature and dwelling type. The findings can guide stakeholders in assessing current conditions and prioritising renovation measures, aiding the development of targeted renovation solutions. Encompassing the representative variations within studied dwelling types enhances the robustness of the results. However, incorporating more refined data could improve the accuracy of the findings, better supporting the energy transition of these dwellings.

Temperature-adaptive rooftop covering with synergetic modulation of solar and thermal radiation for maximal energy saving

The energy consumption for maintaining desired indoor temperature accounts for 20% of primary energy use worldwide. Passive rooftop modulation of solar/thermal radiation without external energy input has a great potential in building energy saving. However, existing passive rooftop modulation techniques failed to simultaneously modulate solar/thermal radiation in response to rooftop surface temperature which is closely related to the building thermal loads, leading to limited or even counter-productive overall energy saving. Here, we report the development of a surface temperature-adaptive rooftop covering with synergetic solar and thermal modulations. The covering, made of a scalable metalized polyethylene film, demonstrated excellent solar absorptance modulation (72.5%) and thermal emissivity modulation (79%) in response to its temperature change from 22°C (indoor heating setpoint) to 25°C (indoor cooling setpoint), and vice versa. Building energy simulations demonstrate that the proposed rooftop covering can achieve all-season energy savings across all climate regions.

A simplified economic model and case study for recovery ventilation based on SPECO method

Covid-19 further revealed the significance of ventilation by air conditioning systems. Most common split heaters and resistance heaters recirculate the indoor air without ventilation process. Ventilation wastes energy consumption by the building. However, adding an air-to-air heat recovery unit seems a quick solution to reduce the wasted heat of the ventilation process. Nonetheless, recovery unit means further pumping power (pressure drop through the air-to-air heat exchanger), capital cost, additional fans and their electricity consumption, exergy costs and so on. Hence, the profitability of the recovery unit depends on outdoor temperature, desired indoor temperature, electricity price of the region, exergy loss and also the aforementioned factors. In this research the general standard Specific Exergy Costing theory is employed and simplified as an economic strategy for recovery ventilation. The model not only is able to predict the profitability of the ventilation process using air-to-air heat exchanger, but also it is an optimization tool for air-to-air heat recovery units as provided as a case study in this paper.

Simplified Energy Model and Multi-Objective Energy Consumption Optimization of a Residential House

Some analyses state that buildings contribute to overall energy consumption by 20–40%, which, in the context of the recent geopolitical energy crisis, makes them a critical issue to study. Finding solutions for better energy management in buildings can have a significant impact on the energy sector, thus reducing EU energy dependencies and contributing to the fulfillment of the REPowerEU goals. This paper focuses on proposing a simplified model of a residential house considering the main appliances, heating and cooling, a photovoltaic system, and electric vehicle recharging. Weather and solar irradiance forecasts are taken into account. The model predicts the energy demands of a house based on online weather forecasts and the desired indoor temperature. The article also focuses on the analysis of how weather forecast uncertainty affects energy demand prediction. This model can be used to better understand and predict the energy demand of either a single house or a set of houses. A multi-objective optimization approach that takes into account the preferences of users/inhabitants is developed to provide a compromise between the price paid for the electricity and temperature comfort. The authors plan to apply the proposed model to a residential house’s real-time control system. The model will be tuned, its predictions will be tested, and it will be used for energy demand optimization.

Parameter identification approach to represent building thermal dynamics reducing tuning time of control system gains: A case study in a tropical climate

As one of the main consumers of primary energy globally, buildings have been among the main targets for implementing energy efficiency solutions, such as building control strategies that maintain occupant comfort and reduce operating costs. The design of such control schemes relies on a thermal model of the building to predict indoor temperature. The model should be sufficiently accurate to describe building dynamics but simple enough to remain optimal for control purposes. This paper proposes a methodology to identify thermal RC networks to model building thermal dynamics of a residential buildings located in humid and rainy climates, a topic not widely covered in current literature. The candidate models for the methodology are determined through a parameter dispersion study, which consists of training the models multiple times and checking if the parameters converge to a single value regardless of their initial value. Then the effect of the training dataset characteristics on model performance is studied. The methodology is established and then tested in a residential case study in Panama from these conclusions. Results show that a linear model with few parameters and trained with only 10 days of data can successfully represent a system with prominent nonlinear phenomena. The model with the best performance during active operation has a validation root mean square error of 0.36°C, which is satisfactory for controller design purposes. The model is then used to tune a proportional integral derivative controller, successfully employed to maintain the desired indoor temperature. Using the identified model to calibrate the controller avoids tedious trial and error procedures.

Heating Sizing Power Reduction in Buildings Connected to District Heating with Dynamically Controlled DHW Setback and Flow Limiters

Space Heating (SH) substations in District Heating-based (DH) systems are typically dimensioned at the design outdoor temperature without accounting for internal and solar heat gains. In residential buildings, the total required DH power typically also includes the need for Domestic Hot Water (DHW). This practice results in oversized substations and high DH design flow rates, which, due to heat gains and building thermal mass utilization in building operation, rarely, if ever, occur. Modern buildings maintain the desired indoor temperature with lower heating power by controlling the SH supply temperature with an outdoor-air-dependent heating curve and heating water flow with room unit thermostats. Applying a dynamic heating control algorithm can be considered one option to reduce the required DH power and optimize the DH network. Another possibility to decrease the needed power is controlling the DH flow by prioritizing DHW production and limiting the DH flow for SH. This study proposed a novel sizing method for the DH substation that quantifies the effects of dynamic control and flow limiters. Building models with detailed hydronic plants, accounting for internal heat gains, and using conventional and dynamic heating controls were developed in the IDA Indoor Climate and Energy simulation tool. The results show a potential DH side power reduction of up to 25%.

A fractional order PID controller using MACOA for indoor temperature in air-conditioning room

Aiming at controlling indoor temperature of each air-conditioning room equipped with fan coil unit (FCU), this paper proposes a hybrid control system to deal with such problem, in which a fractional order PID controller for indoor temperature (IT-FOPIDC) and a three-position controller for supply air volume (SAV-TPC) are used to maintain steady indoor temperature, respectively. For the key problem of tuning parameters of IT-FOPIDC, a modified ant colony optimization algorithm (MACOA) is reconstructed, and it is tested to be feasible by the simulation results. Thus, an algorithm using this MACOA is designed to adaptively solve the satisfied values of five parameters of IT-FOPIDC to further upgrade the control quality of indoor temperature from software. In the meanwhile, SAV-TPC manipulates the corresponding flow rate of supply air discharged from FCU to provide the dynamic variation of cooling or heating load to an air-conditioning room. So these two controllers work together for achieving the desired indoor temperature. The corresponding numerical simulation of this hybrid control system is carried out and the results indicate that this algorithm using MACOA is reliable to tackle the key problem of tuning parameters of IT-FOPIDC so that the control quality of indoor temperature is obviously improved. Moreover, for the same IT-FOPIDC, the control performance of the other intelligent optimization algorithms is compared to that of the proposed algorithm using MACOA under the same scenario, simulation results also show the latter is superior to the former in terms of analyzing the dynamic responses of indoor temperature, which may offer the corresponding reference guides for regulating the key performance parameters in HVAC& R engineering.

Experimental Analysis of a Solar Energy Storage Heat Pump System

This paper introduces a novel solar-assisted heat pump system with phase change energy storage and describes the methodology used to analyze the performance of the proposed system. A mathematical model was established for the key parts of the system including solar evaporator, condenser, phase change energy storage tank, and compressor. In parallel to the modelling work, an experimental set-up of the proposed solar energy storage heat pump system was developed. The experimental data showed that the designed system is capable of meeting cold day heating demands in rural areas of Yanbian city located in Jilin province of China. In day-time operation, the solar heat pump system stores excess energy in the energy storage tank for heating purposes. A desired indoor temperature was achieved; the average coefficient of performance of solar heat pump was identified as 4.5, and the system showed a stable performance throughout the day. In night-time operation, the energy stored in the storage tank was released through a liquid-solid change of phase in the employed phase-change material. In this way, the provision of continuous heat for ten hours was ensured within the building, and the desired indoor air conditions were achieved.

Adaptive optimization of heating curves in buildings heated by a weather-compensated heat pump

This article is concerned with the weather compensated heating of buildings by means of air-to-water heat pumps. A novel adaptive method is proposed for on-line optimization of the heating curve that defines the relation between the heating temperature and the outdoor temperature. Parametrization of the linear heating curve with two reference points is presented, with the aim of providing good tracking of the desired indoor temperature by adaptively adjusting the reference points of the heating curve. Two adaptation strategies are investigated, and a wide range of adaptation constants is explored. The use of these methods is demonstrated on two different buildings, simulated in Transient System Simulation Tool (TRNSYS). The simulation model was validated on a reference building. The results of adaptive optimization show good performance, which is comparable to and even better than the performance based on referential optimal static heating curves.

Wall Cladding Effects and Occupants’ Perception of Indoor Temperature of Typical Student Apartments in Surabaya, Indonesia

Abstract Three types of apartment claddings in Surabaya, Indonesia were studied to analyze their effect into bedroom temperature. They were glass windows in a niche, glass door in a balcony, and glass windows on a plain wall with glass door in a balcony. On-site temperature measurement was recorded and complemented with questionnaire surveys of occupants’ perception regarding room temperature. The study showed that an apartment cladding with the largest proportion of opaque material combined with a balcony offered an indoor temperature of up to 9 °C lower than the outdoor compared to the other cladding types. Nevertheless, 72 % of occupants participated in this study, who use air conditioners during night time, including one with the cladding with the largest temperature difference claimed that the indoor temperature before air-conditioners was still too warm, which triggered air-conditioners initial time more than 10 minutes to achieve the desired indoor temperature. It indicated that the opaque material time lag played a significant role in heating the room during night time when the air-conditioner is about to be operated.

Nonlinear benefit-cost optimization-based selection of insulation material and window type: A case study in Turkey

In this study, we maximize the energy savings of a hypothetical household by choosing an optimal insulation material with its optimal thickness and also the optimal window type. We develop a nonlinear mixed integer optimization model that maximizes the net present value of the benefits obtained by insulation over the lifespan of the house. Savings are calculated based on the gains from the electricity usage for air conditioning during cooling-required days and the fuel usage for heaters in heating-required days. The heat transfer calculations consider conductive, convective, and radiative components simultaneously. The optimization model takes the climate conditions of the region where the house is located, the consumer's desired indoor temperature, and the properties of the insulation options; then, it returns a combination of selected insulation materials with its optimum thickness and window type as output. We applied the optimization model developed to hypothetical houses in four different climatic regions of Turkey for different lifespans. For all reasonable lifespans, the model choses stonewool as the ideal insulation material. For high interest rates, single windows or double-glazed windows are preferable, but as the interest rate decreases and the net present value of the energy-savings increases, the model prefers triple-glazed windows as the ideal material. Erzurum, a city in climatic region 4, characterized by very cold winters and cool summers, was found to require the highest optimum insulation thickness, and the economic return resulting from the above-mentioned energy-saving actions was also found to be the highest in the case of Erzurum. In all the regions, the energy-saving investments were found to be feasible via applying the feasibility assessment techniques of net present value and payback period. The model developed in this study is applicable to any household as long as the required input data are available.

Annual energy analysis of concrete containing phase change materials for building envelopes

This paper examines the annual energy and cost savings potential of adding microencapsulated phase change material to the exterior concrete walls of an average-sized single family home in California climate zones 3 (San Francisco, CA) and 9 (Los Angeles, CA). The annual energy and cost savings were larger for South- and West-facing walls than for other walls. They were also the largest when the phase change temperature was near the desired indoor temperature. The addition of microencapsulated phase change material to the building walls reduced the cooling load in summer substantially more than the heating load in winter. This was attributed to the cold winter temperatures resulting in nearly unidirectional heat flux on many days. The annual cooling load reduction in an average-sized single family home in San Francisco and in Los Angeles ranged from 85% to 100% and from 53% to 82%, respectively, for phase change material volume fraction ranging from 0.1 to 0.3. The corresponding annual electricity cost savings ranged from $36 to $42 in San Francisco and from $94 to $143 in Los Angeles. From an energy standpoint, the best climate for using building materials containing uniformly distributed microencapsulated phase change material would have outdoor temperature oscillations centered around the desired indoor temperature for the entire year.

Diurnal thermal analysis of microencapsulated PCM-concrete composite walls

This paper examines the benefits of adding microencapsulated phase change material (PCM) to concrete used in building envelopes to reduce energy consumption and costs. First, it establishes that the time-dependent thermal behavior of microencapsulated PCM-concrete composite walls can be accurately predicted by an equivalent homogeneous wall with appropriate effective thermal properties. The results demonstrate that adding microencapsulated PCM to concrete resulted in a reduction and a time-shift in the maximum heat flux through the composite wall subjected to diurnal sinusoidal outdoor temperature and solar radiation heat flux. The effects of the PCM volume fraction, latent heat of fusion, phase change temperature and temperature window, and outdoor temperature were evaluated. Several design rules were established including (i) increasing the PCM volume fraction and/or enthalpy of phase change increased the energy flux reduction and the time delay, (ii) the energy flux reduction was maximized when the PCM phase change temperature was close to the desired indoor temperature, (iii) the optimum phase change temperature to maximize the time delay increased with increasing average outdoor temperature, (iv) in extremely hot or cold climates, the thermal load could be delayed even though the reduction in daily energy flux was small, and (v) the choice of phase change temperature window had little effect on the energy flux reduction and on the time delay. This analysis can serve as a framework to design PCM composite walls in various climates and seasons and to take advantage of time of use electricity pricing.

Energy saving potential of night ventilation: Sensitivity to pressure coefficients for different European climates

The suitability of night ventilation to reduce the cooling demand in buildings can be evaluated by coupling Airflow Network Models to Building Energy Simulation tools. To estimate wind-induced ventilation, pressure coefficients (Cp) on the building envelope are key inputs, as well as local wind speed and direction. Cp data obtained by primary sources such as measurements or CFD simulations are considered the most reliable but can be difficult to obtain. An easy alternative are Cp secondary sources, such as databases providing literature data correlations. Therefore an issue arises regarding the choice of the source of pressure coefficients.This paper investigates the effects of Cp from primary and secondary sources on the predicted energy saving potential of night ventilation of an isolated office building for several European climates and some relevant design conditions and simulation parameters. Different Cp sources produce a dispersion of Cp data and differences in the calculated night ventilation rates up to 15%. Contrary to what might be expected, these differences influence only marginally the resulting passive cooling effects. Overall a stronger impact is observed for the colder climates, where higher temperature differences occur between desired indoor temperature and night-averaged outdoor temperature. Finally, for the building under study, the choice of the Cp source appears less crucial than the choice of other building simulation parameters, such as the internal Convective Heat Transfer Coefficient. This study can support building designers towards accurate energy simulations of naturally ventilated buildings.

Modelling ventilation rate, balance temperature and supplemental heat need in alternative vs. conventional laying-hen housing systems

An Excel-based spreadsheet model has been developed to delineate ventilation rate (VR), supplemental heat need ( H s ), balance temperature ( t bal , outdoor temperature below which H s is required to maintain the desired indoor temperature), energy use and cost for H s in alternative (aviary and enriched colony) vs. conventional cage laying-hen houses. The model was applied to the Midwestern U.S. housing characteristics (same land footprint) and winter weather conditions (−30 °C to 5 °C ambient temperature, and a constant relative humidity or RH of 70%). Effects of hen stocking density, target indoor temperature and RH ( t i , RH i ), building insulation, and light period vs. dark period on VR, t bal and H s were examined. For the housing characteristics considered and target indoor condition of 25 °C and 60% RH, t bal for the alternative housing systems was found to be 2.0–2.6 °C higher than that for the conventional cage counterpart. The supplemental heater capacity would need to be 20.5–22.0 kW per 10,000 hens for the aviary houses (107,000-hen capacity) and 17.6 kW per 10,000 hens for the enriched colony house (124,000-hen capacity). Annual H s was estimated to be 0.09 and 0.12 MJ [kg egg] −1 for the enriched and aviary houses, respectively. The corresponding H s cost (in US dollars) would be, respectively, 0.11 and 0.15 US cent [kg egg] −1 at a wholesale liquid propane (LP) fuel price of $0.32 l −1 ($1.21 gal −1 ) or 0.26 and 0.35 US cent [kg egg] −1 at a retail LP fuel price of $0.75 l −1 ($2.84 gal −1 ). Among all the influencing factors considered, t i and RH i setpoints had more pronounced impacts on t bal and H s . The analysis indicated that H s energy cost for the alternative housing systems in the Midwestern USA is less than 0.3% of the total production cost. The simulation model was validated with measured heating energy use by a commercial aviary house in northern Iowa and the difference between the predicted and field-measured H s values was less than 5%. This interactive model can be readily used for analysis of other laying-hen housing, climatic conditions, and/or management scenarios.

Air conditioning versus heating: climate control is more energy demanding in Minneapolis than in Miami

Energy demand for climate control was analyzed for Miami (the warmest large metropolitan area in the US) and Minneapolis (the coldest large metropolitan area). The following relevant parameters were included in the analysis: (1) climatological deviations from the desired indoor temperature as expressed in heating and cooling degree days, (2) efficiencies of heating and cooling appliances, and (3) efficiencies of power-generating plants. The results indicate that climate control in Minneapolis is about 3.5 times as energy demanding as in Miami. This finding suggests that, in the US, living in cold climates is more energy demanding than living in hot climates.

The influence of the zone's indoor temperature settings on the cooling/heating loads for fixed and controlled ventilation

In this study, the thermal performance and the energy requirements of a building single-zone are investigated for both the cooling and heating seasons by employing a thermal-network model. The model has six primary heat-flow paths, in order to take into account the position of insulation in the building envelope, and two secondary paths for the ventilation and the cooling/heating unit. The desired indoor temperature of the zone is defined by a pair of preset points of a thermostat. The energy demands and the resulting indoor temperature variations are determined for fixed ventilation as well as for temperature-controlled ventilation. Computer results for both seasons show how the combined influence of slab structure formations, the desired indoor temperature and ventilation control affect the cooling and heating loads.

Pioneering new indoor temperature standards: the Pakistan project

Field surveys of thermal comfort have been conducted summer and winter in the five climatic regions of Pakistan to help the Pakistani Government to replace existing inappropriate indoor temperature standards. Results are presented which show large variations in desired indoor temperature with climate and season. The reasons for the differences are explored and an indication of the way in which responsive indoor temperature standards, which encourage the use of passive architecture and save energy in air-conditioned buildings, might be framed is presented.

Effects of Global Warming on Energy Use for Space Heating and Cooling in the United States

This study uses a three-step approach to estimate the impact of global warming on U.S. energy expenditures for space heating and cooling in residential and commercial buildings. First, average results from six different global circulation models are used to estimate the change in heating and cooling degree days in five U.S. climate zones associated with a 1° centigrade (C) global warming. Second, the change in degree days is mapped into a corresponding change in U.S. energy use for space conditioning, taking account of differences in population and baseline space conditioning intensity levels across regions, under the assumption that desired indoor temperature is unaffected by climate change. Finally, we estimate the associated change in energy expenditures. We find that a global warming of 1ଌ would reduce projected U.S. energy expenditures in 2010 by $5.5 billion (1991 dollars). This contrasts with earlier studies which have suggested modest global warming would increase U.S. expenditures on space conditioning energy.