Energy and Greenhouse Gas Emission Assessment of Conventional and Solar Assisted Air Conditioning Systems

Energy-related activities are a major contributor of greenhouse gas (GHG) emissions. A growing body of knowledge clearly depicts the links between human activities and climate change. Over the last century the burning of fossil fuels such as coal and oil and other human activities has released carbon dioxide (CO2) emissions and other heat-trapping GHG emissions into the atmosphere and thus increased the concentration of atmospheric CO2 emissions. The main human activities that emit CO2 emissions are (1) the combustion of fossil fuels to generate electricity, accounting for about 37% of total U.S. CO2 emissions and 31% of total U.S. GHG emissions in 2013, (2) the combustion of fossil fuels such as gasoline and diesel to transport people and goods, accounting for about 31% of total U.S. CO2 emissions and 26% of total U.S. GHG emissions in 2013, and (3) industrial processes such as the production and consumption of minerals and chemicals, accounting for about 15% of total U.S. CO2 emissions and 12% of total ...

In this paper, a theoretical study of the thermal performance for hybrid solar air conditioning system was presented to investigate the system performance and suitability for the hot climate with a new control system strategy. The system consists of a vapor compression unit combined with evacuated tubes solar collector and water storage tank. A three-way valve is controlled by a proportional integral derivative (PID) controller to regulate the 3-way valve opening towards the solar system to achieve the minimum temperature of refrigerant leaving the condenser (degree of subcooled), in order to enhance the overall COP of the unit. The governing thermal equations concerning the hybrid solar air conditioning system was applied and solved using engineering equation solver (EES) Software. The results showed that the compression ratio of the uncontrolled hybrid solar system is lower than the compression ratio of the conventional one by 5 %, and this ratio could be increased to 28 % when the control system has been used. Also, the minimum value of the power consumption is 830 W at R=0.1 and Tamb =45 oC, while the maximum value is 994 W at R=1 for the same conditions. The power consumption of the uncontrolled system is lower than the power consumption of the conventional one by 7 % and increases to 23 % by using the control system. An acceptable agreement can be achieved when validating the theoretical model results with experimental results.

Heating and cooling energy trends and drivers in buildings

Simultaneous satisfaction of both thermal and visual comfort in buildings may be a challenging task. Therefore, this paper suggests a comprehensive framework for the building energy optimization process integrating computational fluid dynamics (CFD) daylight simulations. A building energy simulation tool, IDA Indoor Climate and Energy (IDA-ICE), was coupled with three open-source tools including GenOpt, OpenFOAM, and Radiance. In the optimization phase, several design variables i.e., building envelope properties, fenestration parameters, and Heating, Ventilation and Air-Conditioning (HVAC) system set points, were selected to minimize the total building energy use and simultaneously improve thermal and visual comfort. Two different scenarios were investigated for retrofitting of a generic office building located in Oslo, Norway. In the first scenario a constant air volume (CAV) ventilation system with a local radiator in each zone was used, while an all-air system equipped with a demand control ventilation (DCV) was applied in the second scenario. Findings showed that, compared to the reference design, significant reduction of total building energy use, around 77% and 79% in the first and second scenarios, was achieved respectively, and thermal and visual comfort conditions were also improved considerably. However, the overall thermal and visual comfort satisfactions were higher when all-air system was applied.

Vehicle electrification stands as a pivotal catalyst for effecting a low-carbon transition within the transportation sector. End-of-life (EoL) battery treatment, which is mainly aimed at facilitating material recycling, provides considerable co-benefit in reducing greenhouse gas (GHG) emissions. This study assesses the life-cycle GHG emissions from battery production, and examines the impact of three EoL battery treatment strategies: second use, regeneration, and recycling. Prospective scenarios of GHG emissions from electric vehicle battery production in China are further provided. The results show that under the Business as Usual (BAU) scenario, GHG emissions peak at 36 million tons in 2030, with 18 million tons for LFP and 18 million tons for NCM, and decrease to 11 million tons in 2060, with 4 million tons for LFP and 7 million tons for NCM. GHG emissions have more reduction potential as the collection rate increases and the proportion of different strategies applied changes. In a scenario with improved collection rates, GHG emissions would be reduced by 21% in 2060 compared to BAU. In a prioritized regeneration scenario, GHG emissions can be reduced by 32% in 2060, with 64% of lithium resources being supplied by regenerated batteries. In a prioritized second use scenario, GHG emissions can be reduced by 104% in 2060, which involves replacing 27 kilotons of lithium input and mitigating 13 million tons of GHG emissions related to the energy storage system. In light of these findings, we advocate for policy recommendations aimed at fostering the advancement of EoL battery treatment technologies and expediting the transformation of battery manufacturing processes towards carbon neutrality.

Investigation on correlation of energy consumption of multi-buildings on campus area

IEA EBC annex 53: Total energy use in buildings—Analysis and evaluation methods

In the hybrid coolingsolar systems , a solar collectoris used to convertsolar energy intoheat sourcein order to super heat therefrigerant leave thecompressor,andthisprocess helpsin the transformation ofrefrigerant state from gaseous statetothe liquid statein upper two-thirdsof thecondenserinstead of the lower two-thirdssuchas in thetraditional air-conditioning systems and this willreduce theenergyneeded torun the process ofcooling.In this research two hybrid air-conditioning system with an evacuated tube solar collector were used, therefrigerant was R22 and the capacity was 2 tons each.The tilt angle of the evacuated tube solar collector was changed and the solar collector fluid was replaced into oil instead of water.A comparison wasin the amount ofcurrentconsumptionof the two systems at the same operating conditions.The currentconsumptionof the hybrid coolingsystemwith the changed tilt angle and replaced fluid wasless thantheunchanged oneby(38% - 58%), meaning that there was a current consumption saving as a result of tubes tilt angle and solar collector fluid changing.

In the hybrid coolingsolar systems , a solar collectoris used to convertsolar energy intoheat sourcein order to super heat therefrigerant leave thecompressor,andthisprocess helpsin the transformation ofrefrigerant state from gaseous statetothe liquid statein upper two-thirdsof thecondenserinstead of the lower two-thirdssuchas in thetraditional air-conditioning systems and this willreduce theenergyneeded torun the process ofcooling.In this research two hybrid air-conditioning system with an evacuated tube solar collector were used, therefrigerant was R22 and the capacity was 2 tons each.The tilt angle of the evacuated tube solar collector was changed and the solar collector fluid was replaced into oil instead of water.A comparison wasin the amount ofcurrentconsumptionof the two systems at the same operating conditions.The currentconsumptionof the hybrid coolingsystemwith the changed tilt angle and replaced fluid wasless thantheunchanged oneby(38% - 58%), meaning that there was a current consumption saving as a result of tubes tilt angle and solar collector fluid changing.

Planetary Health Diet in a hospital cafeteria: Increasing employee satisfaction and reducing greenhouse gas emissions and costs

Case study and theoretical analysis of a solar driven two-stage rotary desiccant cooling system assisted by vapor compression air-conditioning

Modeling and optimal control of an energy-efficient hybrid solar air conditioning system

The energy saving issues are becoming necessary worldwide, as excessive consumption of energy leads to the consumption of a larger amount of fuel, increases environmental pollution and negatively affects the ozone layer. In Iraq, in particular, the demand for central air conditioning systems and home air conditioners with high electrical capacity has become increasingly clear in the recent years. Air conditioning systems within residential and public buildings, as well as government facilities became a necessity for good internal comfort, which was driven by desertification, high temperature, air pollution and increased population, resulting in increased consumption of electric power and pressing of power plants. Aiming at usage of renewable energy sources, the proposed system uses solar collectors as auxiliary solar thermal compressors and integrate them with air conditioning systems. The proposed solution will increase the cooling system efficiency, reduce electricity consumption and pollution.

In China, the continuously increasing amount of municipal solid waste (MSW) has resulted in an urgent need for changing the current municipal solid waste management (MSWM) system based on mixed collection. A pilot program focusing on source-separated MSW collection was thus launched (2010) in Hangzhou, China, to lessen the related environmental loads. And greenhouse gas (GHG) emissions (Kyoto Protocol) are singled out in particular. This paper uses life cycle assessment modeling to evaluate the potential environmental improvement with regard to GHG emissions. The pre-existing MSWM system is assessed as baseline, while the source separation scenario is compared internally. Results show that 23 % GHG emissions can be decreased by source-separated collection compared with the base scenario. In addition, the use of composting and anaerobic digestion (AD) is suggested for further optimizing the management of food waste. 260.79, 82.21, and -86.21 thousand tonnes of GHG emissions are emitted from food waste landfill, composting, and AD, respectively, proving the emission reduction potential brought by advanced food waste treatment technologies. Realizing the fact, a modified MSWM system is proposed by taking AD as food waste substitution option, with additional 44 % GHG emissions saved than current source separation scenario. Moreover, a preliminary economic assessment is implemented. It is demonstrated that both source separation scenarios have a good cost reduction potential than mixed collection, with the proposed new system the most cost-effective one.

In this paper, an experimental study of the thermal performance for hybrid solar air conditioning system was carried out, to investigate system suitability for the hot climate in Iraq. The system consists of vapor compression unit combined with evacuated tube solar collector and liquid storage tank. A three-way valve was installed after the compressor to control the direction flow of the refrigerant, either to the storage tank or directly to the condenser. The performance parameters were collected by data logger to display and record in the computer by using LabVIEW software. The results show that the average coefficient of performance of hybrid solar air conditioning system (R=1) was about 2.42 to 2.77 and the average power consumption was about 1.1 to 1.12 kW when the ambient temperature was about 34.2 to 39.7 ˚C, while the average coefficient of performance of conventional system (R=0) was about 3.23 and the average power consumption was about 1 kW when the ambient temperature was about 30.8 to 34.3 ˚C. It can be concluded that the use of the hybrid solar system in Iraq with its current form could not be saved electricity.