Indoor Temperature Set Research Articles

Decision Support for Intelligent Energy Management in Buildings Using the Thermal Comfort Model

The main objective of this paper is to present a transparent Decision Support System (DSS) for the energy managers of buildings, which can assist them in setting indoor temperature set point, based on the feedback received by the occupants. Within the proposed DSS, the Thermal Comfort Validator (TCV) tool is introduced, a fully responsive and cross-platform web-app which exploits the Predicted Mean Vote comfort theory by considering real-time feedback of the occupants. The TCV facilitates the detection of the range of accepted temperature inside a building, by correlating “real” with “predicted” thermal comfort, to overcome the limits of the standardized approaches. The proposed system can reveal an important potential for achieving energy savings by means of dynamic event driven data collection and processing, while ensuring high levels of comfort.

A Study on Winter Season Measurement Results to cope with Dynamic Pricing for the VRF System

The dynamic pricing of electricity, where the electricity rate increases in a time zone with a high demand for electricity is typically applied to a building whose power reception capacity is greater than a certain size. This includes the time of use(TOU) electricity pricing in Korea which can induce the effect of reducing the power demand of a building. Meanwhile, a VRF (Variable Refrigerant Flow) system that uses electricity is regarded as one of the typical heating and cooling systems along with central air conditioning (central HVAC) for its easy operation and application to the building. Thus, to reduce power energy and operating costs of a building in which the TOU and VRF systems are applied simultaneously, we suggested a control for changing the indoor temperature setting within the thermal comfort range or limiting the rotational speed of an inverter compressor. In this study, to describe the features of the above-mentioned control and verify its effects, we evaluated the results obtained from the analysis of its operation data. Through the actual measurements in winter operations for 73 days since mid- December 2014, we confirmed a reduction of 10.9% in power energy consumption and 12.2% in operating costs by the new control. Also, a reduction of 13.3% in power energy consumption was identified through a regression analysis.

Experimental Comparison between CAV Control and CO<sub>2</sub> Ventilation Control Approaches with Respect to Energy Saving of Air Conditioner

The objective of this study was to investigate the efficiency of the CO2 control ventilation to enhance energy saving compared with constant air ventilation (CAV) approach of air conditioner. To this end, a small air-conditioner room of 20 square meters was used as the testing room. A carbon dioxide (CO2) sensor was installed inside to measure indoor air quality while two enthalpy sensors were installed both inside and outside for indoor and outdoor air enthalpies online monitoring. The algorithm of CO2 control ventilation used is to compare the CO2 difference between inside and setpoint; when the inside CO2 concentration is lower than the setpoint, the controller will sent a signal to stop the fresh air intake and exhaust air fans. Measurement were conducted for three indoor temperature set points namely 24, 25 and 26 oC. The indoor CO2 level was set at 900 ppm, 800 ppm, 700 ppm and 600 ppm The results of measured electrical power consumption showed that CO2 approach when compared to the CAV approach could save 21.82%, 18.28%, 2.26% and 0.45% and ventilator save 64.19%, 53.4%, 16.8% and 1.26%, for the four CO2 concentration indoor setpoints considered respectively. Simple mathematical relationships were also derived to estimate the energy saving using the CO2 control ventilation. This CO2 control ventilation could be mainly applied for the air condition room of Thailand.

Energy and cost associated with ventilating office buildings in a tropical climate.

Providing sufficient amounts of outdoor air to occupants is a critical building function for supporting occupant health, well-being and productivity. In tropical climates, high ventilation rates require substantial amounts of energy to cool and dehumidify supply air. This study evaluates the energy consumption and associated cost for thermally conditioning outdoor air provided for building ventilation in tropical climates, considering Singapore as an example locale. We investigated the influence on energy consumption and cost of the following factors: outdoor air temperature and humidity, ventilation rate (L/s per person), indoor air temperature and humidity, air conditioning system coefficient of performance (COP), and cost of electricity. Results show that dehumidification of outdoor air accounts for more than 80% of the energy needed for building ventilation in Singapore’s tropical climate. Improved system performance and/or a small increase in the indoor temperature set point would permit relatively large ventilation rates (such as 25 L/s per person) at modest or no cost increment. Overall, even in a thermally demanding tropical climate, the energy cost associated with increasing ventilation rate up to 25 L/s per person is less than 1% of the wages of an office worker in an advanced economy like Singapore’s. This result implies that the benefits of increasing outdoor air ventilation rate up to 25 L/s per person — which is suggested to provide for productivity increases, lower sick building syndrome symptom prevalence, and reduced sick leave — can be much larger than the incremental cost of ventilation.

Simulation of energy saving potential of a centralized HVAC system in an academic building using adaptive cooling technique

Application of adaptive comfort temperature as room temperature set points potentially reduce energy usage of the HVAC system during a cooling and heating period. The savings are mainly due to higher indoor temperature set point during hot period and lower indoor temperature set point during cold period than the recommended value. Numerous works have been carried out to show how much energy can be saved during cooling and heating period by applying adaptive comfort temperature. The previous work, however, focused on a continuous cooling load as found in many office and residential buildings. Therefore, this paper aims to simulate the energy saving potential for an academic glazed building in tropical Malaysian climate by developing adaptive cooling technique. A building simulation program (TRNSYS) was used to model the building and simulate the cooling load characteristic using current and proposed technique. Two experimental measurements were conducted and the results were used to validate the model. Finally, cooling load characteristic of the academic building using current and proposed technique were compared and the results showed that annual energy saving potential as much as 305,150kWh can be achieved.

Indoor Thermal Comfort: The Behavioral Component

This is a study of how indoor temperature settings have changed over time in the United States based on data from the Energy Information Administration’s, Residential Energy Consumption Survey (RECS). It is shown that Americans have moderately raised indoor temperature settings during the heating season over the past thirty years. It is also shown that most Americans keep their homes relatively cool in the summertime and are generally averse to implementing temperature setbacks. It is revealed that occupants in lower-income homes tend to set their thermostats higher in winter than other income groups, but that the most intense cooling tends to take place in both low-income and high-income homes. As expected, renters tend to heat and cool more intensively than homeowners. Getting Americans to change their temperature settings in order to save energy is not easy even though it comes with the promise of financial savings. The use of programmable thermostats thus far has proved unsuccessful. Greater utilization of social marketing to achieve energy savings is suggested, as well as a renewed effort on the part of electricity suppliers to work more closely with homeowners as part of the rollout of the “smart grid”.

Thermal comfort in offices in summer: Findings from a field study under the ‘setsuden’ conditions in Tokyo, Japan

Post Fukushima disaster, the energy consumption perspective in Japan has changed. It initiated unprecedented exercises towards energy saving and produced interesting results. These included the ‘setsuden (energy saving)’ campaigns, which promoted the minimum indoor temperature setting of 28 °C in summer. However, there is no scientific basis for this recommendation. Japan does not have adaptive comfort standards and the ASHRAE standard-55 does not include the data from the land of the rising sun. In this context, we conducted a thermal comfort field study in four office buildings in Tokyo for three months in summer 2012. We measured all the four environmental and the two personal variables. Through a paper based field survey, we interviewed 435 occupants who returned 2402 questionnaires.The occupants' comfort temperature was found to be 27.2 °C. Thermal acceptability was very high at 89% even when 26% of the environments were outside the three central categories of the thermal sensation scale. PMV always significantly overestimated the sensation owing to a wide range of adaptations by the subjects. The indoor air speeds were low, indicating a need for ceiling fans. In 50% of the environments the indoor temperature was more than the 28 °C limit. As the buildings were designed for AC mode, running them in NV mode posed challenges. This study calls for elaborate field studies in offices in Japan for the development of custom made adaptive comfort standards.

An Evaluation of the HVAC Load Potential for Providing Load Balancing Service

This paper investigates the potential of providing intra-hour load balancing services using aggregated heating, ventilating, and air-conditioning (HVAC) loads. A directload control algorithm is presented. A temperature-priority-list method is used to dispatch the HVAC loads optimally to maintain customer-desired indoor temperatures and load diversity. Realistic intra-hour load balancing signals are used to evaluate the operational characteristics of the HVAC load under different outdoor temperature profiles and different indoor temperature settings. The number of HVAC units needed is also investigated. Modeling results suggest that the number of HVAC units needed to provide a ±1-MW load balancing service 24 hours a day varies significantly with baseline settings, high and low temperature settings, and outdoor temperatures. The results demonstrate that the intra-hour load balancing service provided by HVAC loads meets the performance requirements and can become a major source of revenue for load-serving entities where the two-way communication smart grid infrastructure enables direct load control over the HVAC loads.

Analysis of the thermal environment in a mushroom house using sensible heat balance and 3-D computational fluid dynamics

An environmental prediction model was developed for optimal ventilation in a mushroom house utilising a sensible heat balance and a three-dimensional (3-D) computational fluid dynamics (CFD) model. The respiration of the mushrooms and the use of a low-capacity cooler were considered. A mushroom-house-specific ventilation equation was developed to calculate the ventilation rate for a given environmental condition. Calculated ventilation rates were compared with the experimentally measured data for the indoor temperature set to the optimum for growing mushrooms (16.2 °C) with varying outdoor temperature. There was good agreement between the measured and predicted rates (0.2–5.1% error). Calculated ventilation rates (from the sensible heat balance) were used as an input parameter for 3-D CFD model, eliminating the need for experimental measurement of ventilation rate. 3-D CFD simulations were conducted using the same environmental condition to establish the local heat distribution in a mushroom house. The simulation results for temperature were compared with the experimental data at several different locations in a mushroom house and showed negligible errors. The CFD model was also used to improve heat distribution of a mushroom house. It was predicted that enhanced cooling and more uniform temperature distribution could be achieved just by changing the direction of airflow from air inlet ducts and/or installing small fans onto them, but not by changing the directions of airflow from a cooler. This would be a more economical than replacing a cooler or redesigning the entire structure. The model could be used to predict the environmental conditions over different locations in a mushroom house without the need for experimentally determining the ventilation rate.

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.

Waste-to-energy based greenhouse heating: exploring viability conditions through optimisation models

An optimisation approach is proposed in order to assess the technical and economic feasibility of a renewable-energy-based greenhouse in North-Eastern Italy. A floor heating system that can exploit a low-temperature heat flow coming from the condenser of a waste-to-energy plant is chosen for the greenhouse and designed developing a non-linear optimisation model, solved by a genetic algorithm. In order to determine under what conditions the combination of a floor-heating-based greenhouse with a waste-to-energy plant can be profitable, a mixed integer optimisation model is introduced to allow selection of the minimum cost fuel solution as a function of different design variables of the greenhouse, such as indoor temperature settings and floor area. The ranges within which the renewable energy solution can lead to significant savings in comparison to traditional fossil fuel are identified both from the point of view of costs and of environmental impact. Furthermore, the sales prices for waste heat that would make investment in the renewable energy solution attractive for potential entrepreneurs are given.

Conditioning strategies of indoor thermal environment in warm climates

Commenting on some negative effects of traditional conditioning strategies of indoor thermal environment in warm climates, the authors present a fundamental concept of thermal comfort and acceptability, new air-conditioning strategies by using fluctuating air movement based on the findings of human responses to transient thermal environment, and a prediction of energy saving caused by elevated indoor temperature settings. In addition, how to meet the requirement of providing human-beings a healthy, comfortable and affordable indoor air temperature, and to achieve a goal of sustainable development are also discussed in this paper.

Energy requirements for conditioning fresh air and the long-term savings with a membrane-based energy recovery ventilator in Hong Kong

A study of the energy requirements for conditioning ventilation air and the yearly performance of a membrane-based energy recovery ventilator (MERV) in Hong Kong is carried out. The weather data are classified into six process regions in the psychrometric chart and the percentage of annual hours in each region is determined to describe different energy requirements. The variations in the amount of required heating and cooling energy are calculated for different indoor temperature and humidity set points. It is found that the required annual energy is primarily used to remove moisture from fresh air, with only a small fraction used for sensible cooling. The energy for heating in cold weather is negligible. Energy recovery ventilators are employed to study the possible annual energy savings. Hour-by-hour calculations disclose that in hot and humid regions like Hong Kong, about 58% of the energy required for conditioning fresh air could be saved annually with an MERV, which recovers both latent and sensible energy, while only about 10% of the energy could be saved with a traditional sensible-only energy recovery ventilator (SERV). The more humid the weather, the more superior is an MERV in comparison with an SERV.

Indoor temperature changes in retrofit homes

The behavioral response (e.g. changes in indoor temperatures, attention to window and door openings) to residential technical efficiency improvements (e.g. attic insulation, storm windows) is an important and largely unresolved issue. Although there is considerable discussion concerning the extent to which households take back some of the energy savings due to technical efficiency improvements in increased comfort, there is almost no empirical evidence on the subject. Detailed electricity billing data (from mid-1981 to mid-1983) were analyzed for 79 households that received financial assistance from the Bonneville Power Administration to retrofit their homes in mid-1982. The mean retrofit expenditure in these homes was $1900; the mean reduction in annual electricity use was 4700 kWh, of which 83% was due to reductions in space heating electricity use. Analysis of the electricity billing data suggests that these households increased their indoor temperature settings after retrofit by almost 1 °F on average. This temperature increase led to an estimated average loss of almost 600 kWh of electricity saving. In other words, roughly 10% of the energy saving due to retrofit was taken back in terms of increased comfort. These results concerning changes in indoor temperatures should be viewed cautiously because of limitations in the analytical method and the large variation across households.