Workshop on energy efficiency opportunities while phasing-down HFCs Cooling Efficiency: technologies Presentation by Ray Gluckman July 9th 2018, Vienna Presentation Contents Scope for energy efficiency improvements Understanding key
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Presentation Transcript
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Workshop on energy efficiency opportunities while phasing-down HFCs Cooling Efficiency: technologies Presentation by Ray Gluckman July 9th 2018, Vienna<br>
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Presentation Contents Scope for energy efficiency improvements
Understanding key efficiency issues
efficiency: a step-by-step approach
Some examples illustrating:
the excellent potential for efficiency improvements
impact on capital costs
impact of refrigerant selection<br>
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Significant Potential to Improve Efficiency<br>
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Achieving the technical potential there are plenty of opportunities to improve efficiency
what is preventing better uptake of the potential?<br>
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Some Key Principles during next two sessions we will see many examples of:
efficiency improvements related to new equipment (Session II)
efficiency improvements related to existing equipment (Session III)
to help understand efficiency opportunities
what are the key design and operational factors that influence energy use?
let’s start by comparing a refrigeration system with moving a weight……<br>
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Moving a weight downhill is easy<br>
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Moving it back up the hill requires energy<br>
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Moving it back up the hill requires energy The energy required depends on:
The size of the weight, W
The height difference, d (the “vertical lift”)
Practical factors e.g. roughness of the ground W d<br>
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Refrigeration: moving heat on a “thermodynamic mountain” hotter
Temperature
colder Weight = a quantity of heat we need to move
Vertical lift = temperature we need to move it through
= “temperature lift”<br>
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If a colder heat sink is available, cooling is free (heat “rolls downhill”) hotter
Temperature
colder - not realistic or sustainable!<br>
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But, always worth checking for “free cooling” options some good possibilities e.g.
data centre cooling, especially if located in cool climates
food factories – hot product pre-cooling after cooking
cold process streams that need heating
e.g. boiling liquid methane at LNG terminals
but less helpful for “mainstream” RAC applications e.g.
domestic refrigerators
bulk storage and retailing of chilled or frozen food
room air-conditioning in hot countries<br>
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Most RACHP applications – heat has to move “uphill”<br>
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Most RACHP applications – heat has to move “uphill”<br>
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How is the heat moved “uphill”?<br>
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How is the heat moved “uphill”?<br>
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How is the heat moved “uphill”?<br>
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How is the heat moved “uphill”? Evaporating temperature Te must be lower than product temperature
Condensing temperature Tc must be higher than the available coolant<br>
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Why is temperature lift so important? RACHP efficiency is VERY sensitive to temperature lift
just 1 degree C of extra lift:
typically leads to 2% to 4% increase in energy consumption
it is very easy to create many degrees C of unnecessary temperature lift
through poor design
through poor operation
incorrect control settings<br>
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Recent Press Release – 22nd June 2018 India seeks mandatory 24oC AC setting
campaign launched by India’s energy minister Shri R K Singh
he advised:
every one degree C increase in AC temperature setting saves 6%
many commercial establishments use 18 – 21 oC set point
saving achievable by simply adjusting a control<br>
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Reminder: efficiency rules for lifting a weight The energy required depends on:
The size of the weight, W
The height difference, d (the “vertical lift”)
Practical factors e.g. roughness of the ground W d<br>
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RACHP “Heat Mountain” Energy Efficiency Rules Minimise the heat load e.g.
free cooling
better building structure / insulation
less “cold end” auxiliary power (evaporator pumps and fans, lights etc.)
less warm air ingress (e.g. doors on display cases)
Minimise the temperature lift e.g.
bigger heat exchangers
changes to temperature set points
avoiding fouling of heat exchangers (e.g. frost, oil, debris etc.)
Address “practical factors” e.g.
high efficiency compressors
high efficiency thermodynamic cycle
good performance at part load
correct choice of refrigerant These are just a few of the many different measures that may influence design or operational efficiency!
Some will be described in Sessions II and II<br>
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Example of a practical factor: variable operating conditions RACHP equipment designed for a peak condition – the “design point”
highest heat load in highest ambient temperature
but equipment spends most of life at other operating conditions
if designer ignores the “operating envelop” of the system
it is likely that much energy will be wasted<br>
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Impact of efficiency improvement on costs most efficiency measures have a good financial return for end user
any extra capital cost often recovered in 1 – 3 years from energy savings
“big picture” issues can significantly improve financial case
potential savings in peak demand and requirements for new power stations
value of CO2 emission reductions
but, end user has no benefits from these savings
some efficiency measures achievable with no extra capital cost or reduced cost
especially as efficiency technologies become mature
or, if heat load reduced, refrigeration system is smaller (e.g. doors on display cases)<br>
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Example of Maturing Technology – US Refrigerators from Briefing Note A (figure 7)
75% energy reduction
50% price reduction<br>
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Refrigerant Selection good choice of refrigerant is important
it is one of the “practical factors” that influence efficiency
selection will typically influence efficiency by 5% to 10%
other factors are likely to create greater efficiency improvements e.g.
heat load reduction
minimising temperature lift
good maintenance
refrigerant leakage must be avoided
can reduce efficiency significantly<br>
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Concluding Comments many excellent opportunities to improve RACHP efficiency
using a structured approach can help maximise potential
based on:
Minimising the cooling load
Minimising the temperature lift
Accounting for variable operating conditions
Selecting the most efficient refrigeration cycle, refrigerant and components
Designing effective control systems
Checking operating performance and correcting any faults<br>
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Contact Details Ray Gluckman
Gluckman Consulting
email: ray@gluckmanconsulting.com
Tel: +44 1932 866344 Fact Sheets about Kigali Amendment:
www.gluckmanconsulting.com/kigali-amendment/
Fact Sheets about low GWP alternatives to HFCs:
www.gluckmanconsulting.com/low-gwp-alternatives-to-hfcs/<br>
