Air Conditioning Load Research Articles

Thermal Comfort Evaluation of Rooms Installed with STPV Windows

Thermal comfort is an important aspect to take into consideration for the indoor environment of a building integrated with a semi-transparent Photovoltaics (STPV) system. The thermal comfort of units with photovoltaic windows and that of conventional windows, which is an ordinary without PV, were evaluated via on-site tests and questionnaires. Using the thermal comfort investigation of the test rig, the maximum difference in air temperature was found to be around 5 °C between test unit and comparison unit. The predicted mean vote (PMV)–predicted percentage dissatisfied (PPD) value of the test unit was better than that of the comparison unit. It was observed that on sunny days, the PMV value ranged from 0.2 (nature) to 1.3 (slightly warm) in the test unit, and that of the comparison unit was 0.7 (slightly warm) to 2.0 (warm), thereby providing better thermal comfort, especially during mornings. The maximum difference in PPD values was found to reach 27% between the two units at noon. On cloudy days, the difference was negligible, and the thermal sensation between the foot and the head were almost the same. Fifty respondents were asked to complete a carefully designed questionnaire. The thermal sensation of the test unit was better than that of comparison unit, which corresponded with the test results. Thermal, lighting, acoustic, and other environment comfort scores were combined, and the acceptance of the test unit with the STPV windows was found to be 73.8%. The thermal sensation difference between men and women was around 5%. Thus, during summer, STPV windows can improve the thermal comfort and potentially reduce the air-conditioning load.

Exergoeconomic analysis and optimization of innovative cascade bi-evaporator electricity/cooling cycles with two adjustable cooling temperatures

This article works with performance improvement of the conventional combined cooling/power (CCP) cycles to augment energy and exergy efficiencies of the previous systems. For this target, a conceptual configuration of cascade ejector refrigeration system (CERS) is proposed and is joined with organic Rankine cycle (ORC) to generate power and cooling outputs. The introduced CCP system can generate cooling load at two various temperatures for freezing and air-conditioning usages. For power sub-cycle, basic ORC and recuperative ORC with turbine bleeding are selected as topping cycles. Thermodynamic and exergoeconomic assessments of the cycles are done, leading to provision of the working criteria of the systems. Also, an extensive parametric evaluation and single- and multi-criteria optimizations are conducted. With this regard, the optimum air-conditioning load, freezing load, net electricity, energy efficiency, exergy efficiency, and total sum unit cost of the product (SUCP) for the modified system are obtained 44.18 kW, 35.33 kW, 64.03 kW, 48.32%, 65.3%, and 404 $/GJ, respectively. More consequentially, the generator is clarified as the premier portion of destruction, followed by ejectors. Moreover, it is exhibited that the system’s SUCP can be decreased as generator pressure, heat source temperature, and condenser temperature increase, or evaporators superheated temperature and evaporators pressure decrease.

Aggregate Control Strategy for Thermostatically Controlled Loads with Demand Response

The improvement of intelligent appliances provides the basis for the demand response (DR) of residential loads. Thermostatically controlled loads (TCLs) are one of the most important DR resources and are characterized by a large load and a high degree of control. Due to its distribution characteristic, the aggregation of TCLs and their control are key issues in implementing the load control for the DR. In this study, we focus on air conditioning loads as an example of TCLs and propose a simple and transferable aggregate model by establishing a virtual house model, which accurately captures the aggregate flexibility. The deviation of the aggregate model is analyzed for the model evaluation. An air conditioning DR control scheme is proposed based on the aggregate model; it has the advantage of simple implementation and convenient control for the individual units. Simulations are performed in Gridlab-D to evaluate the accuracy and effectiveness of the proposed model and control method.

Experimental investigation on the performance of solar chimney for reduction of vehicle cabin soak temperature

Vehicle cabin soak temperature is dire and in some cases is a life-threatening for any living organism trapped inside it. Also, it dictates the thermal comfort level upon entry, air conditioning (AC) load, and fuel consumption. This study is the first attempts to experimentally evaluate the impact of integrating a solar chimney (SC) on a vehicle exposed to direct sunlight in terms of its cabin soak temperature (CST), thermal comfort, AC power, and driving ranges. Therefore, outdoor thermal soak tests on two identical vehicles were carried out. The results confirmed a significant reduction of the soak cabin temperature, decreasing the cabin soak air temperature by 20.5 °C (max). This reduction can lead to a significant effect on the initial thermal solar loads, thereby exposure time to high temperature environment (thermal stress and anxiety) can significantly be reduced, while also enhance interior air quality, improve vehicle fuel economy, an 85% reduction in compressor power, increasing driving range by 26.25 km within the city drive cycle and 17.5 km on the highway cycle while operating the AC system, and reduce tailpipe emissions while preserving the integrity of the cabin’s interior from cracking and fading. It can be concluded that the proposed strategy is able to achieve the highest cabin temperature reduction ever compared to other passive approaches.

Novel Incentive Mechanism for End-Users Enrolled in DLC-Based Demand Response Programs Within Stochastic Planning Context

In this paper, a novel direct load control (DLC) planning based on providing free energy credits to residential end-users for their heating, ventilation, and air conditioning load during demand response (DR) events is proposed. The obtained credit can then be used by the end-users during relatively higher price periods free-of-cost to enable them lowering their energy procurement costs. Furthermore, the resulting reduction in the total household energy consumption considerably decreases the critical load demands in power systems, which is of vital importance for load-serving entities in maintaining the balance between supply and demand during peak load periods. In this regard, the aforementioned energy credits-based incentive mechanism is proposed for end-users enrolled in the DLC-based DR program, as a new contribution to the existing literature, testing it in a stochastic day-ahead planning context.

Analysis of solar and battery requirements for hybrid DC/AC powered households in the USA

US households consume more electricity compared to other developed countries due to the fact that majority of the US household loads are inefficient. As a result, deployment of residential solar PV cost is increased given the high-power consumption and becomes less viable. Utilities are also increasingly applying surcharges to customers with solar PV installations because of direct impacts to the grid, making purely solar PV installations unattractive. This is especially in the case for low-income households, where they are seemingly shut out from participating in the energy economy given the penalties and the costs. This research primary focus is to make Installed Cost Benchmarks for Residential Solar Photovoltaic with Energy Storage costs more affordable for an average-income home owner in the USA; one approach is to reduce power consumption within the household by adapting DC appliances. So, a compelling means towards reducing household load is to convert a portion of household electrical loads such as LED lighting, air conditioning, ceiling fans, and electronic loads to DC. Secondly, optimizing size of solar panels and battery and without the need for energy export, it compensates for surcharges and recover return on solar investment. Data provided in this paper gives an insight into adapting suitable hybrid DC/AC architecture for three different types of households associated with five different geographical regions based of different climactic conditions spread across the USA. The systems are distinguished by the degree to which redundant AC to DC conversion stages are reduced, which will be inversely proportional to cost. This paper shows that deployment of DC distribution within the house will result in lower average cost and better returns on solar and battery investment than revealed by the NREL study. Also, outlines the costs and savings of different architecture that can be adaptable based on the type of the house, location, savings, and affordability. Only this paper shows the benefits occur due to the reduced number of solar panels and battery storage required when compared to conventional AC powered households. The end goal of this work is to increase the adoptability of solar PV across a more diverse population with a particular focus on low-income households.

Thermodynamic analysis of hybrid cooling system integrated with waste heat reusing and peak load shifting for data center

A hybrid cooling system aimed at enhancing energy, exergy and economic efficiency of data center is proposed. The proposed system combines a high cooling efficiency spray cooling system, a waste heat reusing absorption chiller and a peak load shifting chilled water storage. This combination is implemented by replacing the condenser of spray cooling system with the generator of absorption chiller, and storing cooling capacity of absorption chiller during off-peak time to supplement the cooling load during on-peak time. A thermodynamic model is developed based on energy and exergy balance. Parametric sensitivity analysis is performed to investigate the effects of spray cooling inlet temperature, chilled water temperature, cooling water temperature and ambient temperature on the energy saving efficiency, exergy efficiency and operation cost. Comparison study and economic analysis are conducted based on Dawning 5000A supercomputer in Shanghai, China. Sensitivity analysis results show that the effect of spray cooling inlet temperature is the largest, while the effects of chilled water temperature and cooling water temperature are the smallest. At appropriate condition, the absorption chiller and chilled water storage could totally eliminated the cooling load of air conditioner during on-peak time. The energy saving efficiency, exergy efficiency and operation cost saving could be up to 51%, 17%, and 71% with the cost payback period as low as 286 days.

The Significance of the Adaptive Thermal Comfort Limits on the Air-Conditioning Loads in a Temperate Climate

The building industry is regarded a major contributor to climate change as energy consumption from buildings accounts for 40% of the total energy. The types of thermal comfort models used to predict the heating and cooling loads are critical to save energy in operative buildings and reduce greenhouse gas emissions (GHG). In this research, the internal air temperatures were recorded for over one year under the free floating mode with no heating or cooling, then the number of hours required for heating or cooling were calculated based on fixed sets of operative temperatures (18 °C–24 °C) and the adaptive thermal comfort model to estimate the number of hours per year required for cooling and heating to sustain the occupants’ thermal comfort for four full-scale housing test modules at the campus of the University of Newcastle, Australia. The adaptive thermal comfort model significantly reduced the time necessary for mechanical cooling and heating by more than half when compared with the constant thermostat setting used by the air-conditioning systems installed on the site. It was found that the air-conditioning system with operational temperature setups using the adaptive thermal comfort model at 80% acceptability limits required almost half the operating energy when compared with fixed sets of operating temperatures. This can be achieved by applying a broader range of acceptable temperature limits and using techniques that require minimal energy to sustain the occupants’ thermal comfort.

Feasibility study on Coordinated Control of Heating Ventilation and Air Conditioning Loads and Battery Energy Storage System for Improved Performance of FastADR Response

Abstract Fast Automatic Demand Response (FastADR) system is one of the expected measures to control electricity demand of consumers so that the electricity supply – demand balancing in a short time horizon is improved. Due to their high power consumption in business buildings, Heating Ventilation and Air-conditioning (HVAC) loads are one of the promising candidates on demand-side for FastADR. However, HVAC loads do not perfectly follow external control signals due to the operational characteristics. Although Battery Energy Storage System (BESS) can be useful for supplementing power consumption of an HVAC load in following FastADR signal, its State of Charge (SOC) should be recovered quickly in order to prepare for the next FastADR signal or other purposes, and to reduce the energy capacity of BESS. This paper proposes and numerically demonstrates a coordinated control of HVAC loads and BESS to restore BESS’s SOC without affecting total electricity load and indoor temperature.

Economic Evaluation of Micro-Grid System in Commercial Parks Based on Echelon Utilization Batteries

The rapid growth of the air-conditioning load leads to a further increase in the peak-to-valley difference of the load, which has affected the steady operation of the power grid. An economic evaluation method of the controlled air-conditioning load combined echelon utilization batteries in the micro-grid system of a commercial park participating in the demand side management is discussed in this paper. Through the study of the optimal control mode of air-conditioning load groups, taking the user comfort and the fairness of the air-conditioning control into consideration, an orderly control model of the air conditioning is developed by the improved state-queue (ISQ) control algorithm. Echelon utilization batteries are introduced into the micro-grid system of the commercial park, and a coordinated optimization allocation and economic evaluation model of the micro-grid system in the commercial park is established. The particle swarm optimal algorithm (PSO) and the artificial bee colony algorithm (ABC) are employed to solve the model. The simulation tests of the actual operating data in the commercial park in Shanghai of China show that the controlled air-conditioning load can improve the optimal allocation of resources and promote the energy utilization rate by participating in the demand side management. The optimized regulation of the air-conditioning load not only improves the user’s comfort but also reduces the cost of the purchasing electricity from the grid. When the purchasing cost of the unit capacity for the echelon utilization batteries is less than 254.5391 USD/kWh, the economy of the echelon utilization batteries is better than the conventional energy storage batteries. The method presented in this paper provides a theoretical basis for the echelon utilization of retired electric vehicle batteries (REVBs) and has certain engineering application prospects.

Recommended Air Conditioner Temperature Based on Probabilistic Power Flow Considering High-Dimensional Stochastic Variables

Current power management systems face multiple reliability challenges associated with integrating a population of air conditioner (AiCo) loads into future grids. These challenges, such as the AiCo overload issue, result in a substantial discrepancy between supply and demand during the summer peak, and a few power consumers have to bear the pain of switch power brownouts. The main theme of this paper is the engineering application of AiCo control laws considering the flexible tradeoff between power economics and thermal comfort. The recommended AiCo operating temperature should be reproduced according to different micrometeorological environments. The novelty of the study is that the air conditioner temperature is recommended based on probabilistic power flow (PPF) considering high-dimensional stochastic variables. A fast calculation method is presented to solve PPF calculation problems based on singular value decomposition, principal component analysis and a polling method. This experiment aims to obtain different PPF results corresponding to different AiCo operating temperatures. The effectiveness and efficiency of the proposed method are verified by comparing the method with the Latin hypercube sampling algorithm in a 118-bus power system. Numerical tests verify the benefits of nonnegative matrix factorization and the stochastic response surface method (SRSM) for PPF calculations considering high-dimensional stochastic variables.

Hierarchical Control of Air-Conditioning Loads for Flexible Demand Response in the Short Term

Increased wind power penetration and load demands lead to an increase in the peak-valley difference, which challenges system stability. This paper presents a hierarchical control strategy to coordinate multiple units of aggregated air-conditioning (AC) loads for power regulation to help reduce the peak-valley difference. First, the independent system operator (ISO) determines the purchased reserve capacity according to the roughly expected regulation effect, and the range of adjustable instructions is derived based on the purchased reserve capacity to help reduce the computation burden. Second, the economy optimizations between the ISO and load aggregators (LAs) are carried out to determine the distribution of purchased control units for AC. Third, after implementing unified planning by the ISO, the LAs deliver the scheduling instructions, including the triggering times and unit numbers, to the AC units to achieve short-term power regulation. Additionally, the scheduling accuracy can be set by changing the scale of the AC control units according to the requirements of the instructions. The simulation results show the effectiveness of the proposed control framework in Lianyungang, with 1000 control units participating. The method proposed in this paper could relieve the burden of the peak-valley difference effectively with less economic expenditure.

Optimal Scheduling Method for a Regional Integrated Energy System Considering Joint Virtual Energy Storage

Energy storage equipment is an important part of integrated energy systems, but the construction and operational costs of it are great. Therefore, it’s difficult to apply energy storage equipment on a large scale. As an alternative measure, adjusting controllable loads including electric vehicles (EVs) and air conditioning loads jointly can transfer loads across time periods and reduce variation difference between heat and electric loads. These controllable loads can be regarded as “virtual energy storage system”. Managing the charging of EVs and heat storage of buildings, a joint virtual energy storage system including electric energy storage and thermal energy storage is proposed in this paper. Then, these models are integrated into a scheduling model for regional integrated energy system (RIES). The charging/discharging power management of joint virtual energy storage systems can be realized by arranging the charging of EVs based on vehicle-driven rules and by adjusting building indoor temperatures within the temperature comfort range. Finally, simulations are carried out to demonstrate the effectiveness of the scheduling method. Simulation results show that the RIES optimal scheduling model considering joint virtual energy storage can reduce operational costs. The stability of RIES is improved with the combination of virtual electrical and thermal energy storage.

Demand Response From the Control of Aggregated Inverter Air Conditioners

Inverter air conditioners (ACs) account for a large proportion of air conditioning loads in many countries and, thus, contribute significantly to the peak loads in these areas, especially in summer. On the other hand, as an important category of thermostatically controlled load with thermal energy storage capability, inverter ACs also have the potential to provide considerable flexibility for electric power systems that are faced with increasing challenges posed by high penetration of renewable power generation. This paper focuses on the demand response from the control of the aggregated inverter ACs for load reduction. A virtual energy storage system (VESS) model that encapsulates the room with an inverter AC was established based on the electric model of an inverter AC and the thermodynamic model of a room. Based on the VESS model, a virtual state of charge (VSOC) priority-based load reduction control method with temperature holding and linear recovery strategies was proposed. The VSOC priority based control was designed to decrease the negative impact of load reduction on customers’ thermal comfort from the perspective of the whole AC population. The temperature holding strategy was designed to reduce the electric power of an AC while ensuring that the indoor temperature is always below the allowable limit. The linear recover strategy was proposed to reduce the load rebound after load reduction. Four cases were studied regarding the operation and load reduction of the 100 inverter ACs, and the simulation results verified the models established and the effectiveness and advantages of the proposed load reduction control method.

スーパーマーケットのエネルギー消費に関する研究 (第13報) 空調負荷計算と冷却負荷計算の組み合わせによる省エネルギー効果の検討

スーパーマーケットのエネルギー消費に関する研究 (第13報) 空調負荷計算と冷却負荷計算の組み合わせによる省エネルギー効果の検討

Statistical analysis of air conditioning peak loads of multiple dwellings

Evaluation of the aggregated air-conditioning load of multiple dwellings is important for demand response through the optimum control of numerous air-conditioners (A/Cs), for development of smart-city or smart-community technologies. However, past studies have mainly focused on the characteristics of A/C load in a single household. With this background, the authors conducted statistical analysis of time-series data for A/C electricity consumption in 489 dwellings in Osaka, Japan, and 20 dwellings in Kuala Lumpur, Malaysia to grasp the feature of aggregated A/C load of multiple dwellings. The findings of this analysis are followings: 1) the aggregated A/C load peak per dwelling decreased by almost 50% as the number of dwellings increased from 1 to 10, due to the offset of the diverse time-patterns of A/C load. 2) The occurrence of the top 2.5% A/C load shows strong time and date dependency for an A/C load aggregated by many dwellings:

Reduction in Carbon Dioxide Emission and Energy Savings Obtained by Using a Green Roof

ABSTRACT Green roofs have good heat preservation and insulation performance, which plays an important role in reducing air-conditioning load and reducing carbon dioxide emissions. Experimental research and numerical simulation analysis on the energy-savings and ecological benefits of green roofs in hot summer and cold winter areas in Wuxi, China (31°N, 120°E) are carried out. The experimental results show that a new type of Buddha grass can absorb 1.79 kg of CO2 and release 1.3 kg of O2 per square meter per year. In addition, the annual carbon emission reduction of the green roof in Wuxi was 9.35 kg m–2, and the emission reduction benefit of the green roof was calculated to be USD $1.02 m–2 a–1. The energy consumption simulation shows that the green roof per unit area can save 11.53 kWh per year, and the annual quantitative ecological benefit of a green roof is USD $3.37 m–2. The calculated dynamic investment return is 10 years. A green roof has the benefits of heat preservation and insulation; meanwhile, it can reduce energy consumption. It is also worth mentioning that its energy-saving potential and ecological benefits are substantial, and the investment payback time is short, which makes it worth promoting in a large area.

A Renovation Proposal for Zero-Energy Houses: Outline of Building Planning and Evaluation of Thermal Environment

Considering the effects of electricity shortages caused by natural disasters in Japan, residential energy efficiency is essential. In addition, excessive housing stocks in Japan have highlighted the importance of expertise in renovation methods for zero-energy houses (ZEHs). Therefore, we designed and built a ZEH as a refurbishment of steel-structure industrialized housing to acquire knowledge on ZEH design and renovation. The renovation uses a highly insulated volume against a low insulation volume, which is assumed to be an existing house. The space between the low-insulation wall facing the outside and the high-insulation wall surrounding the main living space functions as a sunroom and called a loggia. By opening and closing the inside and outside windows according to the season and time of day, the loggia functions as a passive system to reduce the air-conditioning load. In this paper, the outline of the building plan of the experimental house and the evaluation of the thermal environment are presented.

Mathematical Modeling for Prediction of Heating and Air-Conditioning Energies of Multistory Buildings in Duhok City

Present endeavor is devoted to estimate the air-conditioning and heating energies or loads of modern buildings in Duhok City, Iraq using new mathematical models. Many parameters have been considered in current modeling, namely, area of building, number of storeys and types of the common materials of the building walls. Regression analysis is performed to formulate new mathematical linear and nonlinear models for the loads. In addition, Fuzzy logic is utilized in the third model employing Sugeno's regulation. The outcomes reveal that the reasonable matching is achieved between the proposed models and mechanical engineering analytical solutions of heating and air-conditioning standards. Consequently, high correlation coefficient as more than 85% is determined between the predicted values of the models and analytical results. The linear model shows perfect matching with the analytical outputs more than the other proposed mathematical formulations.

A bilayer interaction strategy for air‐conditioning load aggregators considering market‐based demand response

With considerable portion of air-conditioning load in total power consumption, air-conditioning load aggregators are authorised to participate in power market by aggregating large amounts of air-conditioning load with or without ice storage system. This paper studies on a bilayer interaction strategy for air-conditioning load aggregators considering market-based demand response, on the basis of a hierarchical deregulated day-ahead market architecture. In the upper layer, load aggregators submit their bids to independent system operator (ISO), after evaluating their load regulation potential. With the aim of minimising load dispatch cost, ISO optimises the dispatch schedule and informs each LA of its bid-winning capacity under a pay-as-bid pricing scheme. In the lower layer, air-conditioning load aggregator adopts a flexible control strategy to optimise the control actions in an effort to maximise its own benefits, as well as keeping indoor temperature within the temperature range in the contract and achieving the desired aggregated demand response capacity allocated by ISO in the upper layer. Thermal dynamic characteristics and corresponding power consumption characteristics of air-conditioning load control strategies are analysed. The resulting model is a mixed-integer non-linear optimisation problem. Finally, simulation verifies the feasibility and effectiveness of the proposed strategy.