ENERGY EFFICIENT AIR CONDITIONING Esmail Mokheimer ME Dept., KFUPM
Workshop Main Topics • Introduction • How AC works and Basic Definitions • Vapor compression against vapor absorption cycles • Cooling and heating by heat pumps • Electric heating against heating by heat pumps • Technology and Performance & Cost –Efficiency Relations • Pay-Back periods for Efficient/Costly AC’s • Sizing of Air Conditioner (cooling Load Calculation)
Introduction • The electric power consumption has increased tremendously, especially in highly economically growing countries such as Saudi Arabia. • In such countries, air conditioning became necessary for life at home and in public areas due to the large demand for comfort. • Electrical energy consumption due to air conditioning (A/C) in buildings is tremendous, especially in Saudi Arabia.
Introduction • The growth of demand for electrical energy in Saudi Arabia, far exceeds the growth of the power being generated. • This is mainly attributed, according to the SEC annual report (2003), to the increased number of customers and to the rise in climate temperature, which implicitly means the growth of the air conditioning electric power consumption.
Introduction • This growth of demand for electrical energy is expected to continue according to the data collected from the ministry of planning and the latest data from the Saudi Electric Company, SEC.
Energy Consumption in Residential Air Conditioners • With this direct relation between the air conditioning loads and the Electric load on the national network, it is necessary to seek the possible strategies that can reduce the power consumption of air conditioners.
Introduction: What is Air Conditioning • Air conditioning is linked to our feeling of comfort through controlling the temperature and humidity. • The primary function of air conditioning is cooling in hot regions and heating in cold regions. although all systems filter the air and some also provide adjustments to the humidity levels. • More generally: Air conditioning is to provide a thermally comfort, clean and healthy environment to the occupants.
How Air Conditioner/Refrigerator works?Let us ask first ; What we need to do? Cool inside the Refrigerator Cool in Summer Heat in Winter
How to achieve this? • By circulating a fluid between the cold and hot environments. • This fluid can exist at lower temperature than that of the cold environment such that it can absorb heat from it • Then we help this fluid after absorbing the heat from the low temperature environment to raise its temperature to a temperature higher than that of the warm ( hot environment) so that it can reject the heat to the hot environment. • Low temperature is achieved at low pressure and high temperature is linked to high pressure. • So, we need to create vacuum (low pressure) near the cold environment and high pressure near the hot environment
How to create the vacuum and high pressure? • By compressor… (suction or vacuum) at the compressor inlet and high pressure can be achieved at the compressor outlet
How to create the vacuum and high pressure? This is called vapor compression cycle?
How to create the vacuum and high pressure? High pressure is achieved by the pump Vacuum is achieved by absorption This is called vapor absorption cycle?
Coefficient of Performance The efficiency of a refrigerator (cooling air conditioner) is expressed in terms of the coefficient of performance (COP). The objective of a refrigerator is to remove heat (QL) from the refrigerated space. The objective of a refrigerator is to remove QLfrom the cooled space. Can the value of COPR be greater than unity?
Heat Pumps The objective of a heat pump is to supply heat QHinto the warmer space. The work supplied to a heat pump is used to extract energy from the cold outdoors and carry it into the warm indoors. Can the value of COPHP be lower than unity? What does COPHP=1 represent? for fixed values of QLand QH
Coefficient of Performance of cooling Air conditioning systems The efficiency of a refrigerator (cooling air conditioner) is expressed in terms of the coefficient of performance (COP). EER is the Energy Efficiency Ratio The objective of a refrigerator is to remove QLfrom the cooled space. EER = 3.412 COP 1 BTUIT = 1.05505585262 kJ 1 W = 3.412 Btu/h
Saudi standard SASO 2663/2012:Energy labeling and minimum energy performance requirements for air-conditioners
Saudi standard SASO 2663/2012:Energy labeling and minimum energy performance requirements for air-conditioners Star rating to be applied from 3 stars and above only
The analysis revealed that improving the villa AC units' energy efficiency ratio (EER) according to the proposed plan can save up to $ 59.12 billion (based on the average oil prices of 2010) and can reduce the Carbon Dioxide emission by 177.21 million tons over the first 16 years of implementing the plan.
What actions are needed Governmental Regulations and rules need to be developed and applied such as: • Building codes stressing the thermal insulations (SASO). • Variable Tariff for the electric energy cost that increases with the consumption (SEC). • Putting MEPS for AC (SASO)
Basic Definitions • Air conditioners use a system of compressors, coils, fans, pipes and controls to remove heat from the home. • The main four components of AC system are • the compressor, • the evaporator and condenser (Heat transfer) coils, • the expansion valve in addition to • the refrigerant. • A refrigerant is the medium used to transfer heat through this closed loop system. • AC systems work mainly according to the following simple thermodynamic cycle
Basic DefinitionsBasic Vapor Compression Cyclehttp://www.sfsb.hr/test/testhome/vtAnimations/animations/chapter09/refrigeration/index1.html
Basic Definitions • The AC also comprises some accessories to have it properly operates. • Some of these accessories are: • the fans and fans’ motors, • the controllers that control the operation of the system such as the thermostat, etc.
Basic DefinitionsWhat Are MEPS, EER and SEER • MEPS is an abbreviation of Minimum Energy Performance Standard. • MEPS are to be put for different products by a governmental authority such as SASO. • The Energy Performance or efficiency level of an air conditioner is determined by its Energy Efficiency Ratio (EER) or "seasonal energy efficiency ratio" (SEER).
Basic DefinitionsWhat Are MEPS, EER and SEER • The SEER rating is technically defined as the cooling output provided by the unit during its normal annual usage period divided by its total energy consumption. • More simply, the SEER rating is similar to the miles-per-gallon rating for automobiles.
Basic DefinitionsWhat is EER and SEER • EER is used for cooling and COP is used for heating. • The units of EER or SEER: • The American standards as well as the present SASO use the BTU/(Wh). So, their EER are in order of 10 (13-19) • The European and the ISO standards use the W/W. So, their EER are in order of ones (about 3-5)
Significance of Operational EfficiencyFor every $100 spent to cool your home using an 8.0 SEER air conditioner, a 14.0 SEER air conditioner should cost you approximately $57 and $ 39 for SEER = 18.Actual savings will depend on the efficiency of your current system compared to the efficiency of a new system and on the Tariff for Electric Power Cost.
Technology and Performance • Energy efficient Technologies of refrigeration systems has gradually been improved with help of control schemes utilizing the more flexible components.
Technology and Performance • New Technologies and innovations are merging recently to the market of air conditioning and refrigeration. • These technologies and innovations cover almost all the basic components of the vapor-compression refrigeration and air conditioning cycles (e.g. the compressor, the heat transfer surfaces, the throttling, the fans, the thermostats and the refrigerant).
Technology and Performance • From the above literature One can conclude that to enhance the Ac performance, there are: • Technologies that involve changes and modifications in the Main 4 components of the AC System. • Technologies that involve changes and modifications in the basic accessories of the AC System. • Technologies that involve adding new accessories to the basic AC unit. • Technologies related to the controllers of the AC operation.
Technology and Performance • Technologies that involve changes and modifications in the Main 4 components of the AC System. • Enhance the Heat transfer • Improve compressor efficiency • Use thermostatic & Electronic Expansion Valves. • Use Alternative Refrigerants
Technology and PerformanceHeat Transfer Enhancement • Increase Frontal Coil Area and Increase Tube Rows.
Technology and PerformanceHeat Transfer Enhancement • Increase Fin Density. • Improve Fin Design • Spraying Condensate onto Condenser Coil • Hydrophilic-Film Coating on Fins
Technology and PerformanceHeat Transfer Enhancement • Improve Tube Design via using Grooved or rifled tubing Photos from ZAC, factory
Technology and PerformanceImprove Compressor Efficiency • AC System efficiency can be improved by simply utilizing more efficient compressors. • Compressorefficiency is improved through the use of high-efficiency motors, high-grade materials in thepumping mechanism, and advanced production methods and equipment. • The most commonly used types are Reciprocating, rotary and scroll compressors.
Technology and PerformanceImprove Compressor Efficiency Variable-Speed Compressors. The advantages of variable-speed compressors are: • 1) they can match changing loadsvery well, better than switch control mechanisms, • 2) in low-speed operation their noise level islow, • 3) they reduce indoor temperature fluctuations, • 4) they improve seasonal energy efficiencyperformance
Technology and PerformanceImprove Compressor Efficiency Variable-Speed Compressors. The control of variable-speed compressors is accomplished through the use of either: • 1) electronic adjustable speed drives (ASD) at an induction motor or • 2) electronically commutated motors (ECM).
Technology and PerformanceThermostatic and Electronic Expansion Valves • The capillary tube and the short tube orifice are pressure-reducing devices that connect the outlet of the condenser to the inlet of the evaporator. • They are designed to provide optimum energy characteristics at one design point.
Technology and PerformanceThermostatic and Electronic Expansion Valves • Thermostatic expansion valves (TXV) are another type of flow control device. • They regulate the flow of liquid refrigerant entering the evaporator in response to the superheat of the refrigerant leaving it. • TXVs can adapt better to changes in operating conditions such as those due to the variation in ambient temperatures, which affect the condensing temperature. • As a result, TXVs can improve equipment seasonal energy efficiency performance.
Technology and PerformanceThermostatic and Electronic Expansion Valves • Electronic expansion valves are similar to TXVs but, since they can be controlled by electronic circuits, they give the additional flexibility to consider control schemes that are impossible for conventional TXVs (ASHRAE 1998).
Technology and PerformanceUsing Alternative Refrigerants • R-22 and R-134a are currently used in all air-conditioning and heat pump equipment. • R-22 is a hydrochloroflurocarbon (HCFC) and demonstrates ozone depletion potential (ODP), its production and use have been targeted for elimination (By 2030). • On the other hand R-134a is a HFC and does not have ODP.
Technology and PerformanceUsing Alternative Refrigerants • Though R-134a poses no danger to the ozone layer, it is a "greenhouse gas" with a fairly high global warming effect of 1300 times that of carbon dioxide. • The Europeans are seriously considering phasing it out starting in 2009.
Technology and PerformanceUsing Alternative Refrigerants • Two alternatives have shown promise; • 1) R-407C, • 2) R-410A. However, both have demonstrated shortcomings when compared to R-22. • Systems with R-407C yield efficiencies that are approximately 5% less than those charged with R-22, • while R-410A exhibits significantly higher compressor discharge pressures.
Technology and PerformanceUsing Alternative Refrigerants • The refrigerant R-410A is one of the substitutes currently accepted as a replacement for the commonly used HCFC-22 (also known as R-22). • The new material is marketed under the trade names AZ-20, Suva 9100 and Puron. • An air conditioner using R-410A has slightly different specifications than traditional cooling systems. • Higher pressures are needed for the refrigerant to have the same cooling effect.
Technology and PerformanceUsing Alternative Refrigerants • This increased pressure requires design changes in the compressor and piping. • However, efficiency of this new refrigerant is comparable with the older product. • There are models currently available that have a SEER (Seasonal Energy Efficiency Ratio) of 18. • Moreover, the new refrigerant Ikon B has excellent potential to be a quickly developed product with commercial success
Technology and Performance • Ikon B refrigerant is one of an advanced family of nonflammable, non-ozone-depleting refrigerants that have good cooling capacity. • Ikon B also has low global warming potential • Tests at the Department of Energy (DOE)’s Oak Ridge National Laboratory gave a 20-25% higher coefficient of performance versus R-22.