Air Conditioning Requirements Research Articles

An innovative process design of seawater desalination toward hydrogen liquefaction applied to a ship's engine: An economic analysis and intelligent data-driven learning study/optimization

Integrating heat recovery applications with heavy engines during transportation is critical for achieving sustainable production and reducing the irreversibility associated with the power production process of the engine. In this regard, the current paper introduces a novel waste heat recovery method utilizing the hot flue gas released by a 1-MW ship's engine to yield liquefied hydrogen from seawater desalination while simultaneously meeting the ship's air-conditioning requirement. In addition, a techno-economic analysis and an advanced feasibility study/optimization are conducted. The process employs reverse osmosis desalination to generate freshwater fed to a water electrolyzer for hydrogen production. The needed power is supplied from an organic flash cycle coupled with an ejector-based bi-evaporator refrigeration cycle. The first cooling loop of the refrigeration cycle offers air-conditioning, while the low-temperature loop yields cooling for the Claude hydrogen liquefaction cycle. A comprehensive feasibility assessment is conducted from the thermodynamic, economic, and environmental viewpoints, and accordingly, an intelligent data-driven learning approach is implemented for performing different multi-criteria optimization scenarios. This approach uses an artificial neural network with a multi-objective grey wolf optimization method. The LINMAP method is employed to reach the most favorable scenario and identify the optimal solution. The findings indicate that the flash temperature attains the highest mean sensitivity index measured at 0.377. Moreover, the best optimization scenario is associated with the exergy efficiency, CO2 emission reduction, and liquefied hydrogen cost as objective functions, calculated at 11.39 %, 22.31 kg/MWh, and 10.25 $/kg, respectively.

A probabilistic bottom-up modelling approach for synthetic load profiles within the energy efficiency management of cruise ship cabins

A reliable estimate of the electrical demand is a decisive factor in the design of electric board systems on cruise ships. This applies to all areas of the ship, including the hotel area with its up to several thousand cabins, which account for a non-negligible share of the total energy demand. In this paper, a simplified bottom-up model that can depict the electrical demand cabins with high temporal resolution and thus support marine and electrical engineers in developing future on-board power grids is presented. Key-card data will be used as a basis to easily access the behaviour of passengers on board. Another benefit is that the key data of the electrical consumers can be easily adapted to different types of ships and cabins. By including the ships route it is possible to precisely calculate the heat input through the glazing at any time of day and to determine its effect on the air-conditioning requirement. The model presented here is therefore not limited to certain regions but can be used globally. The functionality of the model is demonstrated on the example of a Caribbean cruise where the average electrical demand of a cabin is determined to 1.6 kWh per day.

Heat Policies and AC Availability in US Prison Systems

BACKGROUND AND AIM Climate change will increase the number of hot days and heatwaves leaving incarcerated populations particularly vulnerable to extreme heat due to their lack of agency and control over their heat exposure. Previous prison heat policy analysis has not utilized Heat Index to provide context for the implementation of policies or had access to air-conditioning data. We aimed to examine the coverage and gaps of US prison system heat policies and air-conditioning access. METHODS Prison heat policies were identified using 52 prison system (50 states, DC, and Federal Bureau of Prisons) websites and complemented by state legislation. Heat policies were analyzed using the National Weather Service’s (NWS) Heat Index Calculator on maximum reported temperature values. Facility-level air-conditioning data for 18 prison systems were public or received through public records requests by UCLA’s COVID-19 Behind Bars, with facility function, capacity, and heat risk collected from federal, state, and the Intercept’s Climate and Punishment datasets. RESULTS Half of the prison systems had publicly-available heat policies (n=52), of which 81% included temperature values (n=21). 64% of heat indices using maximum indoor temperature (n=14) would be classified as "caution” and 63% of heat indices using temperatures when respite resources would be provided (e.g. extra water) (n=8) were classified as "extreme caution” by the NWS assuming 50% relative humidity. 18% of facilities (n=374) lacked AC access completely. Among these, 55% of non-air-conditioned facilities (41,000 operational capacity) are at "severe or extreme heat risk”. Overall, 23% of facilities whose function includes serving heat-sensitive populations (n=202), lack any air-conditioning despite their heat risk. CONCLUSIONS This study emphasizes the need for national correctional temperature policies and air-conditioning requirements to protect the thermal health of those who live and work in carceral facilities. KEYWORDS environmental justice built environment prison

Experimental analysis on heat mitigation potential of stacked coir fiber mat and perlite as an alternative for green roof

Depleting non-renewable resources and global warming motivated researchers to focus on passive cooling solutions to minimize the internal temperature of buildings. The benefits of using stacked coir mat and perlite in wet and dry conditions are tested for their cooling capacity compared to green roofs are explored in this research work. The benefits are quantified in terms of heat flow and temperature variations in a field experiment, and they are compared to a conventional bare roof in a tropical region in the Indian subcontinent (8.9142oN, 76.632oE). The heat transfer to the inside of the roof for dry coir mat paved, stacked coir mat and perlite bed, stacked wet coir mat and wet perlite bed, and extensive green roof system with coir mat as retaining layer are reduced by 38.43%, 63.21%, 55.3% and 56.97% respectively. This study evaluated the evaporative cooling capacity of wet coir mat and wet perlite, which have given almost near cooling capacity of green roof for 24 h. Considering its low maintenance and low initial cost, the usage of the stacked coir fibre mat with perlite shows a compatible reduction in heat transfer through the roof slab as that of the green roof. The coir insulation with perlite will undoubtedly reduce the energy requirement for heating ventilation and air conditioning (HVAC) systems to a greater extent.

Thermodynamic investigations on PDC based solar air conditioning system

Global warming is raising the ambient temperature and thus resulting in increased air conditioning requirements. The increase in power requirements of air conditioning systems, in turn, burdens the electricity needs and more electricity generation further adds to global warming. In such situations, the availability of solar energy and its utilization for air conditioning systems appears a potential solution to a certain extent. This paper deals with the thermodynamic analysis of a parabolic dish based air conditioning system working on vapour absorption refrigeration cycle for the H2O and LiBr combination as working fluid. Thermodynamic modelling was used to assess the impact of changing the initial concentration of lean solution and the varying condenser temperature under the atmospheric conditions of that region during peak air conditioning demand months on several parameters such as coefficient of performance, cooling effect, and exergetic efficiency of the system. At 45 percent of the initial LiBr concentration in weak solution, the system’s highest coefficient of performance is attained.

Potentials and limitations of direct air capturing in the built environment

This concept study presents an approach for resolving the trade-off between energy-efficient building operation and the provision of hygienically harmless indoor air quality. A novel coupling of HVAC-systems (heating, ventilation and air conditioning systems) with DAC-technology (direct air capturing technology) is proposed to separate CO2 in the exhaust air of buildings and recirculate the CO2-depleted air back into the building. In a mainly theoretical approach, the corresponding potentials and limitations of the novel HVAC/DAC-coupling in recirculation mode are evaluated. For that purpose, CO2-loads in the feed and exhaust air of four buildings located in Germany were measured using calibrated non-dispersive infrared (NDIR) sensors with pyroelectric detection principle. Subsequent numerical model simulations resort to typical meteorological data as well as building operation parameters grouped in different scenarios. The measurement and simulation results were assessed with regard to: (i) the unique possibilities of a HVAC/DAC-coupling in recirculation mode for the improvement of indoor air quality, (ii) the energy saving potentials through reduced air conditioning requirements enabled by a HVAC/DAC-coupling in recirculation mode, and (iii) the potential allocation of CO2 separated from building exhaust air for energetic and/or material reutilization in decentralized systems. In conclusion, a HVAC/DAC-coupling in recirculation mode can not only reduce the energy demand of buildings but also facilitates access to unutilized CO2-resources transported in the built environment and additionally offers the potential to improve indoor air quality. However, a suitable DAC module for operation in indoor air is not yet commercially available.

Evaluation of hybrid evaporative-vapor compression air conditioners for different global climates

Currently, a majority of global residential air-conditioning requirements are met using cooling systems based on the vapor compression cycle (VCC). To meet the future demand for space cooling and to reduce the corresponding environmental impact, there is a need for alternative cooling systems which require less resources and exhibit a higher coefficient of performance (COP). One of proposed alternatives is called the hybrid evaporative-vapor compression (HEVC) cycle, which utilizes adiabatic latent cooling in combination with the VCC. In this paper, we conducted a feasibility analysis of a HEVC system by comparing its performance to that of VCC for various global climates. To accomplish this, we developed and validated models to simulate the performance of residential VCC and HEVC systems. ASHRAE weather data and design conditions were then used to compare the performance of the two systems. In general, HEVC systems are best suited for hot arid climates with energy reduction greater than 20%. Conversely, humid climates are not suitable for HEVC adoption due to degraded performance of evaporative coolers in these climates. In addition to comparing the energy savings from HEVC systems, it is also critical to analyze their water consumption. Generally, climates that benefit the most from HEVC technology tend to also experience water scarcity issues. Thus, both the energy savings and water consumption of HEVC systems must be analyzed to guide the discussion on their adoption.

Modeling, Design and Construction of a Zero-Energy PV Greenhouse for Applications in Mediterranean Climates

This paper concerns the design, modelling, and construction of a high-efficiency mini PV greenhouse performing as a Nearly Zero Energy Building (NZEB). The greenhouse is equipped with a semi-transparent roof-mounted photovoltaic system (3 kWhp) that feeds an air-source heat pump providing cooling and heating. The PV-generated power can be also stored in a battery. A dynamic simulation model (EPlus) of the real greenhouse is developed to predict its performance and investigate beneficial control strategies. The hourly profiles of different variables (energy, temperatures, illuminance) are deeply investigated. The energy-saving strategies, as reflective shading and controlled natural ventilation, prove to reduce the yearly energy needs by 30%. The energy storage model is developed by the Authors and coupled with hourly solar production. The PV electric model includes the temperature effect on module performance, the inverter efficiency curve, and the battery state of charge. The coupled dynamic analysis shows that the photovoltaic plant meets the air conditioning requirements for 94% of the hours of operation and that the energy surplus could feed the grid with approximately 1355 kWhel per year. The validation of the present model will be possible with future measurements and monitoring of the greenhouse once operating in place.

Experimental Study on The Transient Regeneration of Multi- Coaxial Cylindrical Layers of Cloth Material Impregnated with Calcium Chloride Solution.(Dept.M)

Desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement, associated with desiccant cooling, is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effect of variables such as air inlet temperature, air mass flow rate and initial desiccant concentration on the regeneration process are of great interest. In the present experimental work a high performance bed that combines good mass transfer characteristics with low pressure drop is used. The bed consists of multi-coaxial cylindrical layers made up of cotton cloth as a holder for liquid calcium chloride desiccant. The accumulated mass of evaporated water as well as the solution concentration during the regeneration period is assessed based on the variables listed above. The solution concentration and accumulated mass of regenerated water are correlated with air inlet temperature, air mass flow rate and desiccant initial concentration. The functional correlations developed should be useful in the design of such regenerators.

Exergetic design and optimisation of LNG cold energy utilisation system for dual-fuel main engine of a container ship

In this paper, a 9200 TEU container LNG fuel-powered ship is used as a prototype ship, and combined with the cooling load requirements of on-board cold storage, desalination and air conditioning, a...

Impacts of a warmer world on space cooling demand in Brazilian households

Air Conditioning (AC) appliances are a highly effective adaptation strategy to rising temperatures, thus making future climate conditions an important driver of space cooling energy demand. The main goal of this study is to assess the impacts of climate change on Cooling Degree Days computed with wet-bulb temperature (CDDwb) and household space cooling demand in Brazil. We compare the needs under three specific warming levels (SWLs) scenarios (1.5 °C, 2 °C and 4 °C) to a baseline with historically observed meteorological parameters by combining CDDwb projections with an end-use model to evaluate the energy requirements of air conditioning. The effects of the climate change were isolated, and no future expansion in AC ownership considered. Carbon dioxide (CO2) emissions associated with AC energy demand are also calculated. Results show an increase in both average CDDwb and AC electricity consumption for the global warming scenarios in all Brazilian regions. The Northern region shows the highest increase in CDDwb (187% in CDDwb for SWL 4 °C), while the Southeast presents the highest AC energy consumption response (326% in the AC energy consumption for SWL 4 °C) compared to the baseline. At the national level, CDDwb and the AC energy consumption in all SWLs scenarios grow by 70%, 99% and 190%, respectively.

Investigation of indoor air quality and thermal comfort condition in airport terminal buildings

PurposeThis paper aims to measure the thermal comfort conditions and indoor air quality parameters, through on-site measurements taken in the areas mostly occupied by the passengers and airport staff. Terminal buildings consist of areas with various functions. Heating, ventilation and air conditioning requirements vary from area to area, thus leading to challenges in the management of indoor environment quality. Therefore, the study focuses on investigating the indoor environment conditions in various areas of the terminal buildings.Design/methodology/approachIn this study, the thermal comfort and indoor air quality were evaluated based on the parameters [CO2 concentration, relative humidity, temperature, predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD)] collected for summer 2019 from different zones inside the International Dalaman Airport terminal building located in the southwest of Turkey. The measurements were performed in the areas mostly occupied by the airport staff and passengers (check-in area, security control areas, international departure lounge, domestic departure lounge and baggage claim hall).FindingsAs a result of the study, it was observed that the CO2 concentration was 480–965 ppm, the relative humidity was 51.9–75.8% and the temperature was in the range of 23.9°C–28.3°C inside the airport terminal. The PMV values were determined to be in the range of −0.23 to 0.67, and the PPD values 5–15%, which are used to measure the thermal comfort conditions.Originality/valueThere has been limited study on the determination of the indoor air quality in airport terminals and the investigation of the thermal comfort conditions. However, in this study, indoor air quality and thermal comfort conditions were determined by on-site measurements in the five mostly occupied areas by passengers and employees in the terminal building.

Numerical heat transfer analysis and development of a heat removal system for an unshaded parked car in sunny day: computational fluid dynamics study

Increase in air temperature inside a parked car cabin causes negative impacts such as low thermal comfort, health risk for the passengers/pets inside the cabin, increased fuel consumption due to higher air-conditioning requirements. The present project focuses on methods to reduce the cabin temperatures for a car parked in unshaded condition. CFD analyses along with experimental validation have been performed with the use of different proposed cabin temperature control methods such as use of electrochromic tint on windshield, use of inlet and outlet vents, lowering of windows and combinations of these. Commercial CFD package ANSYS Fluent has been utilized to develop a numerical model for car cabin temperature distribution assessment when a parked car is subjected to solar load at different locations inside the cabin such as dashboard, seats and boot. A solar surface to surface radiation model is used in conjunction with solar calculator to capture the solar radiation that included change in position of the sun. A 5:1 scale down model of car cabin has been used for experimental validation with the help of help of PT-100 resistance thermometers. Good reduction in cabin temperatures has been observed for all the proposed cooling methods with 14 °C reduction for the combined tint, vents and lowered windows case.

Study on Desiccant and Evaporative Cooling Systems for Livestock Thermal Comfort: Theory and Experiments

The present study considers evaporative cooling and desiccant unit-based air-conditioning (AC) options for livestock AC application. In this regard, proposed systems are investigated by means of experiments and thermodynamic investigations. Air-conditioning requirements for animals are theoretically investigated and temperature-humidity index (THI) is estimated. A lab-scale heat mass exchanger based on the Maisotsenko-cycle evaporative cooling conception (MEC) is set up and its performance is evaluated at different ambient air conditions. In addition, a desiccant-based air-conditioning (DAC) unit is thermodynamically evaluated using a steady-state model available in the literature. The study focuses on the ambient conditions of Multan which is the 5th largest city of Pakistan and is assumed to be a typical hot city of southern Punjab. The study proposed three kinds of AC combination i.e., (i) stand-alone MEC, (ii) stand-alone desiccant AC, and (iii) M-cycle based desiccant AC systems. Wet bulb effectiveness of the stand-alone MEC unit resulted in being from 64% to 78% whereas the coefficient of performance for stand-alone desiccant AC and M-cycle based desiccant AC system was found to be 0.51 and 0.62, respectively. Results showed that the stand-alone MEC and M-cycle based desiccant AC systems can achieve the animals’ thermal comfort for the months of March to June and March to September, respectively, whereas, stand-alone desiccant AC is not found to be feasible in any month. In addition, the ambient situations of winter months (October to February) are already within the range of animal thermal comfort.

Energy conservation potentials of an office buildings in Northern Nigeria: A case study of Katsina secretariat complex

<p>The importance of energy conservation in our contemporary world cannot be overemphasized, efficient utilization of energy has significant impact in improving economy at all levels of human endeavour. No doubt, adequate and appropriate utilization of energy especially electrical energy boosts up any organizational developmental activities. Recently, research interest has emphasis towards efficient energy utilization and energy conservation as the effective means of reducing energy consumption in buildings thereby reducing its maintenance cost. This paper investigated and analysed the energy consumption characteristics of Katsina state secretariat complex for the period of 3 years (i.e. from 2014 to 2016) based on site surveys and analysis of the energy end users present, using the records of electricity utility bills and Automotive Gas Oil (AGO), being the two energy carriers of the complex. Records have shown that, the secretariat complex average electricity and AGO annual consumptions were found as 1045661.95 kWh and 116650.33 litres of AGO (which is equivalent to 1250491.54 kWh) respectively. The investigation revealed a distinct consumption pattern, indicating peak energy consumption during the hot months of April to August due to significant air conditioning requirements. The result of the investigation of the energy conservation potentials in the secretariat complex have shown that, energy savings of up to 6.5% of the total energy can be achieved by switching-off all security lights during the day. While turning off the air conditioners in the early morning hours of between 8am to 10am would provide a saving of up to 19% of the total energy. Furthermore, a saving of 16.5% of the total energy can be achieved when the incandescent lamps are replaced with the energy efficient ones. The energy conserving measures (ECMs) followed in this research has shown significant savings in terms of both energy and cost, and if well implemented can give way for a sustainable energy management of similar office buildings in future.</p>

Experimental investigation into cleanroom contamination build-up when applying reduced ventilation and pressure hierarchy conditions as part of demand controlled filtration

The use of cleanrooms is increasing and the expectation is that this growth will continue in the coming decade. When compared to an average office building, cleanrooms consume large amounts of energy due to their high Air Change Rates (ACRs) and strict air conditioning requirements. Application of Demand Controlled Filtration (DCF) is a means to reduce the (fan) energy demand. The question is whether the air quality is compromised at reduced ACR and overpressure conditions in the non-operational hours of a cleanroom. In a cleanroom mock-up, experiments have been performed to investigate the particle concentration build-up for different cases with DCF, including an extreme case with zero ACR and zero pressure difference. For the DCF conditions and the specific case study, conditions for particle concentration outside the cleanroom, that may still provide high-quality Good Manufacturing Practices (GMP) conditions in the cleanroom, are derived from the results. Furthermore, it assumes DCF application via occupancy sensing, i.e. starting DCF 30 min after the last person left the cleanroom. When applying DCF for a normal workweek (production 08:00–17:00), fan energy savings higher than 70% can be obtained without compromising the air quality requirements under normal circumstances. DCF, in combination with a reduced pressure difference, therefore is regarded as a feasible solution to reduce the energy demand of cleanrooms when the personnel in the cleanroom are the main source of contamination. These results are obtained for the presented case study. Though assuming a conservative approach, confirmation of these outcomes for other cleanrooms is recommended.

Generation, Distribution and Utilization of an Electrical Energy in Industrial and Domestic Buildings

If we look back few years into the past, we come to know that with the rapid development of human societies, day to day modern life and smart industries, etc. becomes so hungry and greedy for electrical energy. Today, Electrical energy is being consumed by every single machine used in almost each and every application. Conventional and nonrenewable sources like coal, oil, gas, etc. have been depleting very fast, and the world should now shift more towards renewable sources like solar, wind, tidal, etc. for harnessing electricity. Electricity consumption is increased in the industrial and domestic sectors due to the increased comfort (air conditioning) requirements, increment in the usage of power-consuming devices and the sudden increment in building occupancy area. This paper shows the current status of demand and supply scenario of electrical energy in the world and India. Generation capacities as per the renewable and nonrenewable sources in India have been discussed in detail. Almost 45% share of the electrical energy consumed in the industrial or commercialized and domestic buildings is consumed for air conditioning purposes. the brief discussion is presented in this paper on the sales and distribution of the air conditioning units and future possibilities in the same field as per the sustainable development scenario.

Land Use Changes in a Peri-Urban Area and Consequences on the Urban Heat Island

The effect of urbanization on microclimatic conditions is known as “urban heat islands”. In comparison with surrounding rural areas, urban climate is characterized by higher mean temperature, especially during heat waves and during nights. This results in a higher energy requirement for air conditioning in buildings and in a greater bioclimatic discomfort for urban populations. The reasons of this phenomena are ascribable principally to the increase of solar radiation storage and to the decrease of dissipation of water by evapotranspiration in urban environment respect to rural ones. The aim of this paper is to give a quantification of the air temperature increase due to an urbanization process. This quantification is conducted by comparing surface energy balance (incoming and outcoming radiation and turbulent fluxes) in urbanized area versus rural areas. This quantitative approach will be validated using a fluidodynamic model (Envi-Met) in a case study area representative of one among the various regional models of urban area growth. In particular, the model of expansion of small towns around big cities (2003–2008 land use changes) of a plain near-urban area in the Po Valley region (Italy) was used.

Envelop Insulation for Energy Efficient Smart Buildings in India

The building sector is amongst the largest energy consuming sector across the world. Within the building sector, about 75 percent of the total energy is consumed by the residential buildings. The energy sector is directly and indirectly associated with greenhouse gas emissions, since majority of energy sector is dependent on fossil fuels, which are primary source of emanation. Building energy requirements are comprised of need for lighting, air conditioning and other home appliances operations. Air conditioning requirement is derived from the climatic condition in which a building exists. The building components such as walls, roof and windows are exposed to solar radiation and outside air temperature. Heat is conducted from exterior environment into the interior of the building envelop through these channels, wherein majority (approx. 60%) is conducted by walls and roof. Envelop insulation is considered as an efficient retrofitting measure to reduce heat gain from walls and roof, thereby need of air conditioning to remove that heat. In this work, envelop insulation has been designed for the Indian residential buildings existing in the three climate zones of India, i.e. warm-humid, hot-dry and composite climate zones. Electricity saving potential in an insulated envelop and associated life cycle cost saving analysis is carried out considering the application of four commercial insulation materials namely, expanded polystyrene, fiberglass, polyurethane foam and extruded polystyrene. It was concluded that at the design temperature 25˚C, annual electricity saving potential in retrofitted wall per unit area varies from 9 kWh to 16 kWh, whereas in case of roof it varies from 18 kWh to 28 kWh per unit area per year. Fiberglass is observed as the most cost effective insulation material, considering life cycle performance of the insulation material for all the climate zones.

Thermodynamic investigation of a new combined cooling, heating, and power (CCHP) system driven by parabolic trough solar collectors (PTSCs): A case study

A new solar-based, combined cooling, heating, and power system is designed and developed for the school of engineering at Urmia University in Urmia, Iran. The proposed arrangement consists of a solar subsystem with parabolic trough solar collectors, an organic Rankine cycle, two heating processes, and two single-effect absorption chillers. The system is thermodynamically studied for the summer air conditioning requirements, considering genuine energy demand and variable solar radiation in three different operational modes (solar, solar and storage, and storage modes). The influences on the system performance are assessed of varying three main variables including the number of days, organic Rankine cycle pump inlet temperature, and organic Rankine cycle turbine inlet pressure. The results demonstrate that the highest cooling, heating and electrical loads in the summer air conditioning are 896.9 kW, 228.5 kW, and 1500 kW, respectively. The energy load is provided by employing 449–1625 number of PTSCs throughout the year. Furthermore, for summertime the energetic and exergetic analyses reveal that the energy efficiency of the system in the solar mode, solar and storage mode, and storage mode is found to be 98%, 47.3%, and 98%, respectively. Accordingly, the exergy efficiencies were equal to 17%, 8.3%, and 17%.