Enhancing The Efficiency Of New And Existing Cooling Systems

Enhancing The Efficiency Of New And Existing Cooling Systems
Dr Robert Lamb CEng FInstR Group Sales & Marketing Director Star Refrigeration Ltd Industrial Refrigeration Plant Operating & Aftercare - What's The cost. In this presentation we look at energy costs associated with refrigeration and chiller systems and how these can be affected by assessing the cooling requirements as well as careful system design and control.

Why Should I Focus On Enhancing Efficiency?
There are two key business drivers for improving the efficiency of cooling systems. The first is the environment and the need to meet carbon reduction targets to comply with their corporate and social responsibility commitments.

This graphic from NASA in the US hows the rise in the average surface temperature of the planet since 1880, when modern records began. Temperatures shown are yearly average numbers. The global average surface temperature in 2012 was the ninth warmest since Nine of the 10 warmest years in the modern meterological record have occurred since Higher temperatures are attributed to increased levels of heat-trapping greenhouse gases in the atmosphere, especially carbon dioxide which comes from human burning of fossil fuels like oil, coal and gas.

Using ancient air bubbles trapped in ice we can see what the Earth's atmosphere and climate were like in the distant past. Today’s carbon dioxide (CO2) levels are higher than they have been at any time in the past 400,000 years. During ice ages, levels were around 200 parts per million (ppm) and increased to around 280 ppm during interglacial periods. In 2013, CO2 levels surpassed 400ppm for the first time in recorded history. This recent relentless rise in CO2 shows a remarkably constant relationship with fossil-fuel burning, and can be well accounted for based on the simple premise that about 60 percent of fossil-fuel emissions stay in the air. If fossil-fuel burning continues at a business-as-usual rate, CO2 will continue to rise to levels of order of 1500 ppm. The atmosphere would then not return to pre-industrial levels even tens of thousands of years into the future. Credit: Data: National Oceanic and Atmospheric Administration. Some description adapted from the Scripps CO2 Program website, "Keeling Curve Lessons.“ Graph and text from climate.nasa.gov website

The second reason for improving efficiency is profit.

The data shown in the above graph comes form the Department for Energy and Climate Change (DECC) 2012 Energy and Emissions Projects, Annex F. It projects electricity cost will rise by more than 40% over the next 18 years, peaking around 2025/6. Reasons for these rises include increases in fossil fuel costs and investment by energy companies in renewable and nuclear energy. Increases in electricity costs will affect businesses in terms of profitability. Do nothing and profitability will reduce and could eventually lead to your demise. Data taken from DECC – 2012 Energy and Emissions Projection Annex F

Total Cost Of Ownership
Capital Aftercare Energy Total Cost Of Ownership Energy plays a major part in the life cycle cost of cooling equipment and can be 70% to 80% of the total. Focusing on improving efficiency will reduce the total cost of owners. This is best done at the design stage but retrofitting enhancements also provides benefit.

Start Measuring Star Measuring
The first step in improving efficiency is to start measuring so that you can benchmark. Adding electric meters is low cost but the benefits are massive as you are able to track where the energy is consumed and can then take steps to improve.

What Factors Affect Efficiency?
Equipment Operation Cooling Load Efficiency Equipment Selection Operating Temperature What Factors Affect Efficiency? There are numerous factors that affect the efficiency of a cooling system. Four key aspects are: The actual load itself The temperature that is being maintained and at which energy is rejected Equipment efficiency How the equipment is controlled, particularly at reduced load and in changing ambient conditions

Cooling Load Efficiency What Factors Affect Efficiency? The actual load itself

What Make Up The Cooling Load?
Ambient Temperature Insulation Air/Moisture Ingress Product Load Electrical Load People Defrosting What Makes Up The Cooling Load? There are numerous factors which introduce energy in the form of sensible and latent heat into buildings, chambers or process cooling equipment. These include: A temperature gradient between the ambient and inside of a chamber/building results in heat flow from hot to cold through the building fabric, doors and other apertures Insulation acts as a barrier to the flow of heat into buildings, pipes, vessels etc. Air and moisture ingress through doors and other apertures Electrical loads from motors, lighting and other electrical and mechanical equipment The introduction of warm product such and food or chemical reactions Respiration and the energy emitted by people working inside a temperature controlled environment Where moisture has deposited on evaporators within a chamber, there is the periodic requirement to defrost. This is not a 100% efficient process, adding energy into the surroundings. Efficiency of defrost depends on the type of system installed (e.g. electric, hot gas etc). Lets look at some ideas for reducing the incoming load and improving efficiency

Reducing The Cooling Load
Eliminate Poor Door Control Ambient Air = +32°C/70% RH Chamber = +2°C 1m3/s air ingress = 101kW Refrigeration CoP = 3 Refrigeration Power = 33.7kW Electrical Cost = 6p/kWhr Eliminating Cooling Load? Poor door control is a major source of air and moisture ingress into a refrigerated chamber. The left hand images shows a poor seal around a refrigerated lorry, whilst the right hand image shows a damaged door. Both are for a chilled facility at +2°C. On a warm, humid day, where the ambient air is +32°C and 70% RH, air entering the building and being cooled to the +2°C condition requires 101kJ/m3 of heat extraction. This corresponds to 101kW of energy. Assuming an efficient cooling system with a CoP of 3, this means 33kW of electrical energy is required to remove this heat and at 6p/kWhr, this equates to a running cost of over £17,695 per year. This excludes the additional load from defrosting! The load and operating cost would increase by a further 40% if the chamber was at -25°C (i.e. a freezer). This demonstrates the importance of good door control.

Insulation Thickness Panel Thickness (mm) U Value (W/m2K) 50 0.39 60 0.31 80 0.25 100 0.2 125 0.16 150 0.13 175 0.11 200 0.1 220 0.09 Eliminating Cooling Load? Insulation of buildings reduces the heat gain into a building when the outside temperature is greater than the inside. Insulations ability to reduce heat gain can is calculated using its U value. The table above shows the insulation U value for difference thicknesses of the widely used panel material Polyisocyanurate (PIR). This indicates the flow of energy per m2 and per degree K of temperature difference between inside and out. The lower the U value, the great the insulation’s ability to prevent heat gain into the building.

Insulation Thickness Eliminating Cooling Load? The graph shows how the heat gain per m2 of insulation decreases with thickness. It is important to get the correct balance of thickness. Too thin and it will have an adverse affect on the cooling load. However, the affect of increased insulation tails off as thickness increases and eventually increasing thickness will have negligible affect and the benefit will be outweighed by the increase in capital cost. For example, for cold store applications, the optimum benefit is gained up to 150mm of thickness

Free Cooling Free Cooling It is also important to look ambient temperature and decide whether cooling can be done using outside air for part of the years. This is possible where the temperature of the room/chamber or fluid being cooled is relatively high compared to ambient. The graph shows average UK temperatures per month and we see for a quarter of the year, the ambient in most of the UK is below 10°C and less than 15°C for 6 months of the year. Through careful selection of air handling equipment, it is possible to use free cooling for many months of the year where room temperatures are above 15°C (e.g. office, ambient warehouses and data centres)

Free Cooling Data Centre Free Cooling Data centres are major consumer of electrical energy in the UK. They consume MW of power to run the IT equipment and then MW of power to extract and reject this heat to atmosphere. The great news is that with advances in IT equipment design, it is now possible to extract heat from the electronics at increasingly higher temperatures. In this case, we look at providing water at 20°C. During warmer months, this requires mechanical refrigeration but as the temperature falls, we are then able to begin to switch to free cooling. In winter conditions, all cooling is possible without the need to run compressors.

Switch To LED Lighting Original Install: 7 x 250W lights Continuous Operation 15,330 kWhr/yr LED Install: 7 x 48W lights Intelligent Operation 2,943 kWhr/yr 24/7 Operation 80% Saving 85% to 90% with intelligent control Improved visibility LED Lighting Lighting is a continuous load for many buildings including offices and warehouses. The heat omitted by lighting enters the room and is then extracted by the cooling equipment. This is a double penalty as you are not only paying for the lighting electricity but also the refrigeration or air conditioning power to remove the heat. The development of LED lighting and intelligent control began in offices, homes and other ambient temperature facilities, reducing lighting load through lower energy bulbs but also the use of intelligent lighting control which switches lights off when areas are unoccupied. More recently, this technology has been implemented in temperature controlled warehouses, particularly cold storage facilities. This is an early example of such a facility where a trial was undertaken to demonstrate the benefit of LED lighting. The seven existing sodium based lights consumed 250W each and had to be left on 24/7 due to the time taken to warm up again if switched off. They were replaced by 7 off 48kW LEDs. This immediately reduced lighting power by more than 80% and with intelligent control, the annual saving is between 85% and 90% based on aisle usage. The reduction in energy has the added benefit of lowering load on the refrigeration plant. For a typical cold store, every 2kW saving in lighting energy reduces the refrigeration plant power consumption by 1kW.

Cooling Load Efficiency Operating Temperature What Factors Affect Efficiency? The temperature that is being maintained and at which energy is rejected

Evaporating Temperature
Cooling Temperature Having reduced the heat gain into a space, the next key factor affecting cooling efficiency is the temperature being maintained. The above graph shows the affect of a 1K increase in operating temperature on cooling efficiency for a fixed heat of rejection temperature (i.e. ambient). The higher the cooling temperature, the greater the efficiency.

Case Study - Room Temperature Change
Example – Changing Room Temperature Over the past few years, retailers have looked to increase temperatures within warehouses along with improved temperature control. In this example, store temperatures were increase by an average of 2K in the frozen and chill areas.

Temperature Monitoring At the same time independent monitoring software was installed to measure store temperature at product level around the warehouse rather than the existing probes which were adjacent to the room coolers. The system collects data at 10 minute intervals and this is then stored for records and regulatory compliance. The installation of probes close to product resulted in the need to recommission the refrigeration plant control due to difference in store temperature of as much as 1.5K between cooler and floor. This was a beneficial affect, in that the control temperature was raised.

Measured Saving At 5 UK DCs Cooling Temperature The net result were savings of 11% to 21% based on measured data taken over two 12 month periods (before and after the temperature change). Taking a pessimistic 10% of this changing being attributed to the change in probe position and variations in ambient temperature the net effect is an average 7% saving across all 5 DCs. This is in line with the theoretical savings 3% to 4% saving per 1K

Additional Benefit Adding the temperature monitoring provided the added benefit of providing excellent temperature control across the store, ensure all areas are within specification.

Case Study – Data Centre Chillers
Data Centre Case Study This graph shows a data centre application where the customer was looking to increase to chilled water temperature to optimise efficiency. The graph shows how chiller CoP increases at higher water temperatures, increasing efficiency by 25%.

Case Study – Data Centre Chillers
Data Centre Case Study Assuming continuous operating throughout the year and an average temperature of around 15°C to 20°C, the estimated energy saving is around £10k per year.

Condensing Temperature
Moving to condensing temperature, a 1K increase reduces the plant efficient. For the frozen and chill applications, we’ve assumed an evaporative condenser, whereas the A/C is based on air cooled. This explains the greater reduction vs the chill application. Overall, the increase is close to 3% per 1K rise.

Minimising Condensing Temperature
Keep Condensers Clean Electronic Expansion Valves Avoid Air Recirculation Efficiency TEV EEV Condensing Temperature Ideas for minimising condensing temperature include: Avoid air recirculation – This results in warm air circulating back onto the condenser, raising the air on temperature. Location of the condenser is important, along with the need to ensure sufficient fresh air. Also avoid discharging air directly onto a wall. Keep condensers clean – A clean condenser means the maximum efficienct. Dirt, bags, leaves etc for a barrier to heat transfer and reduce efficiency, thus increasing condensing pressure and power. Fit electronic expansions valves (EEVs) – Traditional thermostatic expansion valves (TEVs) require a minimum condensing pressure difference to operate correctly and to prevent liquid return to the compressor. EEVs don’t require this pressure difference, allowing the condensing pressure to modulate with ambient temperature without the risk of liquid returning to the compressor. Temperature Time

Cooling Load Efficiency Equipment Selection Operating Temperature What Factors Affect Efficiency? Equipment efficiency

Main Electrical Consumers - Refrigeration
Electrical Consumption Compressor = 90% Condenser = 5% Evaporator(s) = 5% Main Electrical Consumers – Direct Refrigeration Systems The images shows a typical, ‘direct’ cooling systems where refrigerant is circulated to the areas being cooled (e.g. cold store, chill store). The major electrical consumers for this type of system are the compressors, condenser and evaporator(s). The typical split for low temperature systems is 90% compressor, 5% condenser and 5% evaporator. This may increase is 70%/15%/15%, respectively for chill chamber cooling. PLANTROOM

Main Electrical Consumers - Chillers
Electrical Consumption Compressor = 75% Condenser = 15% Pump(s) = 10% SECONDARY CIRCUIT PUMP Main Electrical Consumers – Indirect Refrigeration Systems This next images shows a typical, ‘indirect’ cooling systems where the refrigerant cools a secondary fluid (e.g. water or glycol) and this is then is circulated to the areas being cooled (e.g. process equipment, air handling equipment, data servers). The major electrical consumers for this type of system are the compressors, condenser and secondary fluid pump(s). The typical split for low temperature systems is 75% compressor, 15% condenser and 10% evaporator. PLANTROOM

Evaporating Temperature
Compressor Selection It pays to look at different manufacturers of compressors for the same project. The graph shows differing coefficients of performance CoPs for the same duty from three suppliers of screw compressors. There is a 4% difference between the three which can be a considerable saving at larger cooling capacities. For example, for 250kW of motor power running 24/7/365, a 4% improvement in efficiency would reduce this by 10kW resulting in a nett saving of £5,000 per year.

Compressor COP Vs Temperature - Chillers
Data Centre Case Study Going back to our data centre application where the customer was looking to increase to chilled water temperature to optimise efficiency. The improvement in chiller CoP at higher water temperatures, increased efficiency by 25%.

Data Centre Case Study However, moving to a magnetic centrifugal compressor and higher water temperatures increases efficiency by up to 300%

Data Centre Case Study Replacing the screw chillers with centrifugals would result in further savings of around £15,000 per year per chiller based on a 20°C average ambient

Compressor Selection - Chillers
1MW Chiller For Data Centre Cooling Screw Chiller Centrifugal Chiller Compressor Performance Curves The secret behind these savings when switching to centrifugal compressors is the part load and low ambient performance. The left hand graph shows a standard screw compressor chiller with DX evaporator and its performance at various loads points and ambient temperatures. Due to the necessity to maintain head pressure across the expansion valve and the need to maintain a differential to drive the oil return system, the profile is flat at lower ambient temperatures. However, using the oil free centrifugal compressor and flood evaporators, it is possible to float condensing pressure down to much lower conditions where the centrifugal design delivers far high efficiencies.

Compressor Comparison - Chillers
Data Centre Case Study If we look at a 1000kW chiller, the savings are 4 times greater (4 x 250kW/compressors), resulting in savings of over £1.8M over 20 years operation based on predicted increases in energy costs as detailed earlier. This assumes 24 hour operation, which is reasonable for data centres.

Equipment Operation Cooling Load Efficiency Equipment Selection Operating Temperature What Factors Affect Efficiency? How the equipment is controlled, particularly at reduced load and in changing ambient conditions

Compressor VSD Case Study
Process Cooling Case Study Total Cost Of Ownership Energy plays a major part in the life cycle cost of cooling equipment and can be 70% to 80% of the total. Focusing on improving efficiency will reduce the total cost of owners. This is best done at the design stage but retrofitting enhancements also provides benefit. This example is for a variable process load requirement which used a number of chillers with fixed speed reciprocating compressors. The project retrofitted a variable speed reciprocating compressor to the trim chiller, with the remaining units only running a full load.

Process Cooling Case Study Total Cost Of Ownership This graph shows the benefit in CoP when using variable speed versus fixed speed compressors. The improvement can be as much as 30%.

Process Cooling Case Study Pre-Install Install Period Post-Install Total Cost Of Ownership Here is measured data showing the actual improvement in kWhr usage post installation per week. This equated to around 40,000kWhr or £2,400 per week with a payback of around 12 months on the compressor package and installation.

Compressor head pressure
Condenser Fans 16.6kW 33.3kW Off On Off On Fan control Compressor head pressure Without VSDs Without VSDs Condenser Fans Moving to auxillary equipment, condenser fans are another area of focus. The example is based on an evaporative condenser with two fans and shows the benefit of switching to VSD control. Without VSDs, two fans operate in a stepped manner with either one or both on (so power of 16.6kW or 33.3kW). Fans switch on as temperature rises but power required is often great than necessary. With VSD operation, the fans speed varies to match heat rejection requirements and ambient temperature. VSDs VSDs Temperature Temperature Time Time

Condenser VSD efficiency
Cooling System VSD Control Benefits of VSD control On off control works but is inefficient. Installing VSD control of the fan motors it is possible to match speed with the system load requirements. At full load, the power consumptions are similar for VSD control as fixed speed. Rejected heat On On Off Off

Cooling System VSD Control VSD Control As speed reduces, the power saving increase following the cube law. This means that at 75% speed, the power is around 42% On On Off Off

Cooling System VSD Control VSD Control As speed reduces further to 50%, the power requirement is only 12.5% On On Off Off

Condenser VSD Case Study
Example Calculation: Fan Motor 22 kW Days/Yr Days Hr/Yr Hrs Inverter Loss 5 % Fixed Speed Operation Air Vol (%) Time (%/yr) Power (kW) hr/Yr kWhr/yr 100 30 22 2,628 57,816 75 12 16.5 1,051 17,345 50 18 11.0 1,577 25 15 5.5 1,314 7,227 2,190 Total 99,733 DC Case Study This VSD control has been rolled out to a number of end users. The example calculation has been used to justify installation. It looks at both fixed and VSD speed operation based on 25% air volume increments and estimated % run times per year. For fixed speed fans, the air volume is assumed to be achieved through on off control of the fan over the year. For example at 75% air volume, the fan is on for 75% of the 1051 hours per year and off for the rest. This means that the average power usage is 75% of 22kW (16.5kW).

Example Calculation: Fan Motor 22 kW Days/Yr Days Hr/Yr Hrs Inverter Loss 5 % Variable Speed Operation Air Vol (%) Time (%/yr) Power* (kW) hr/Yr kWhr/yr 100 30 23.1 2,628 60,707 75 12 9.7 1,051 10,244 50 18 2.9 1,577 4,553 25 15 0.4 1,314 474 2,190 Total 75,978 Saving 23,754 DC Case Study Under VSD control, the fan runs continuously but slows down to meet the air volume requirement. This reduces power in line with the cube law and saves 24% power (even when including a 5% inverter loss) * Including Inverter Loss

Total Estate Estimated Savings 4 Sites 8 Condensers Calculations based on 8.5p/kWhr Site Total Fan Power (kW) Install Price Savings Additional Saving * Payback A 37 £34,828 £5,094 £1,245 5.49 B 74 £37,464 £10,188 £1,280 3.27 C 60 £33,494 £8,260 £1,390 3.47 D 44 £34,028 £6,058 £1,335 4.60 Total £139,814 £75,978 DC Case Study VSDs were rolled out to 4 DCs in the UK, each with 2 condensers and performance measured against the projected savings above. Additional savings were estimated over and above the electrical energy based on the condenser belts and motors lasting longer as they aren’t starting and stopping. * Maintenance savings – motors, belts, better control

The graph shows data over the first 3 months of data monitoring, with the red columns showing the cumulative savings for one site. The measured results were 13% higher than those predicted in the estimate with the difference attributed to the %s used in the estimates and changes in ambient conditions and building load. Measured savings 13% higher than estimates

Optimise Equipment Control Reduce Load
Summary Optimise Equipment Control Reduce Load Improving Efficiency Careful Equipment Selection Raise Operating Temperature Improving Efficiency Hopefully this short presentation provides some ideas for improving your businesses cooling efficiency. They things to remember are: Reduce your cooling load through looking at improvements in the building design, door control etc Look at whether you can increase the temperature at which existing room or fluids are being cooled to. Ensure you select the optimum efficiency equipment Look at ways of optimising equipment control to maximum efficiency. VSDs are a good place to start.

Star Refrigeration – From Humble Beginnings to the Natural Choice
Pioneering Natural Refrigeration Technology since 1970 More than 300 staff in 11 locations across the UK and a number of agents in Europe and Asia Has expanded from an industrial refrigeration company to a multi-faceted engineering group Pioneering development of sustainable solutions & natural refrigeration technology The Star Refrigeration group of companies offer a diverse range of products and services including design, manufacturing, contracting, aftercare, consultancy and training. Founded in 1970 by two mechanical engineers, Anthony Brown and Dr Forbes Pearson, and operating from the later home in Glasgow, Star Refrigeration first steps in the industrial refrigeration and heating business were small and tentative, after the two men were made redundant. But fast-forward 43 years, and the company has mature into a diverse business group with more than 300 staff in 11 locations across the UK and a number of agents in Europe and Asia - and it is the largest and most successful independent cooling and heating contractor in the UK. The largest and most successful independent cooling and heating contractor in the UK Star Refrigeration – From Humble Beginnings to the Natural Choice

Q & A Q & A

Enhancing The Efficiency Of New And Existing Cooling Systems

Similar presentations

Presentation on theme: "Enhancing The Efficiency Of New And Existing Cooling Systems"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Enhancing The Efficiency Of New And Existing Cooling Systems

Similar presentations

Presentation on theme: "Enhancing The Efficiency Of New And Existing Cooling Systems"— Presentation transcript:

Similar presentations

About project

Feedback