Hecu – high energy efficiency solution for condensing units fitted with DC compressors.

Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
HECU – high energy efficiency solution for
condensing units fitted with DC compressors.
Ing. Giovanni Tonin
Application Specialist
Business Unit Retail Marketing dept.
CAREL INDUSTRIES S.p.A. - Brugine (Padova)
12th of June, 2015
XVI European Conference Milano

1.  Target application
2.  Regulations
3.  Hecu sistema
4.  Control algorithm
5.  Comparison of ON-OFF vs DC technology
6.  Natural refrigerants
7.  Conclusions
Summary

Small stores, such as convenience stores, service stations,
small discount supermarkets or corner shops, are a segment
with a higher rate of growth than larger stores such as
supermarkets and hypermarkets.
This growth is the result of both new openings and retrofits
of existing stores.
~ + 27%
Growth rate per year
(worldwide mkt survey)
Target application
400000

410000

420000

430000

440000

450000

460000

470000

480000

490000

500000

2014
2015
2016
2017

Total
Condensing
Unit

source

Directive 2009/125/EC of the European Parliament and of the Council (Energy Related
Product, ERP, also called “Ecodesign”), defines:
• the minimum COP (coefficient of performance) for units with a capacity of less than 5 kW,
• the minimum SEPR (seasonal energy performance ratio) for units between 5 and 50 kW.
To fulfil these requirements, it will be important to use technology that can modulate
capacity based on effective system requirements, thus also reducing condensing unit
energy consumption.
Regulations: Energy Performance

HFCs
will
become
less
available
and
more
expensive

The main pillar of the new EU 2014 F-Gas regulation
is the reduction of emissions by moving to lower
GWP solutions.
The aim is to reduce the total quantity of CO2
equivalent placed on the EU market by 79% before
2030.
GWP
up
to
2500

January
2020

GWP
up
to
150

January
2022

Regulations: EU 2014 F-Gas

Typically, the refrigeration system in these stores is made
up of one or more condensing units, mostly medium
temperature units, and a variable number of refrigerated
units (typically around five), either showcases or cold
rooms.
Traditional system:
•  ON-OFF compressor
•  1 to 3 configuration or 1 to 1 configuration (i.e. 3 ref. units require 3 independent CDUs)
•  Stand alone and not optimized operation of the units
Hecu sistema 1/3
ON-OFF COMPON-OFF COMPON-OFF COMPON-OFF COMP

•  The use of DC compressors
allows condensing unit capacity
modulation across a range from
a minimum of 20 rps to a
maximum of 120 rps.
(17%-100%)
•  Serial connection between the
condensing unit and each
refrigerated unit inside the store
permits information to be
exchanged in real time.
Hecu sistema:
•  DC compressor
•  Up to 5 refrigerated units
•  Synchronized operation thanks to serial communication
DC
COMPRESSOR

Hecu sistema 2/3
SERIAL

COMMUNICATION

Hecu sistema 3/3
Other important benefits are:
• DC technology has also low operating noise, making it ideal for
installations in residential areas
• With Hecu sistema it is possible to obtain a fine regulation that means
stable product temperature and gives optimal food preservation
• Wide range of remote monitoring systems in order to optimize system
performance, carry out preventive maintenance and analyze energy
consumption
• It Includes guided procedure to configure the unit (Wizard) and to
configure the system (Fast commissioning) together with a wide number
of optimized default

Condensing unit operating conditions are affected
considerably by outside temperature
65% of the time the condensing
unit operates at part loads
between 50% and 80%
only 8% of the time at full load
The unit operates at part loads for most of the time
The temperature varies throughout the day and year
Control algorithm: part load operation

Smooth Lines function
is used to optimise evaporator capacity based on actual cooling demand, allowing more
effective and stable control of cabinet temperature.
This function modulates the temperature inside the cabinet exclusively using the
electronic expansion valve, and adjusting the superheat set point by adopting accurate
PI control.
Control:
1.  If the control temperature is
approaching the set point
2.  SH set point is increased
3.  To reduce cooling capacity to the
refrigerated unit
Control algorithm: refrigerated unit

FLOATING SET POINT
CALCULATION:
1.  Request from each evaporator
2.  Capacity of each evaporator
3.  Defrost status of each evaporator
Moving from the minimum to maximum set point, the DC compressor will
decrease its speed, operating at high efficiency and avoiding ON-OFF cycles.
The wide range of modulation allows the compressor
to precisely follow the floating set point.
Control algorithm: condensig unit

We will now examine three different situations involving a system made up of
•  1 condensing unit
•  3 showcases (3000W, 2000W, 1000W)
Control algorithm 1/4
MULTISPLIT
PIPING

Same
refrigerant
speed
along

the
sucAon
line
to
help
the

return
of
the
oil

All the temperatures of the refrigerated units
are below the set point.
The set point of the condensing unit moves rapidly
to the maximum value , providing less cooling
capacity and more energy saving.
There is cooling demand from all the
refrigerated units.
The largest (3000W) has the highest
demand.
The set point of the condensing unit moves
rapidly to the minimum value so as to provide
maximum cooling capacity.

There is cooling demand from all the
refrigerated units.
The smallest (1000W) has the highest
demand.
slowly to the minimum value to provide
maximum cooling capacity.
All the temperatures of the refrigerated
units are below the set point and then
reach the set point.
The set point of the condensing unit
moves to the maximum value and stops
when all the set points are reached

Unit 1 no demand
slowly to the minimum value until all the set
points are reached and remains at that value
Unit 2 with cooling demand
Unit 3 is defrosting
The temperatures of these 2 refrigerated
units are below the set point and then
reach the set point.
Unit 3 is still defrosting
The set point of the condensing unit moves to
the maximum value and stops when all the set
points are reached

ON-OFF TECHNOLOGY
•  R404A refrigerant
•  Fixed set point
•  3 refrigerated units (4000 kW)
DC TECHNOLOGY
•  R410A refrigerant
•  Floating set point
•  3 refrigerated units (4000 kW)
•  Wide range for capacity modulation with DC
compressor
•  At part loads, this solution reduces refrigerant
flow-rate through the heat exchangers, thus
increasing efficiency
•  DC technology also features better motor energy
efficiency
•  No capacity modulation with ON-OFF compressor
•  The heat exchangers are used at design conditions,
with lower energy efficiency
•  ON-OFF technology sees “cycling losses” every time
the compressor is started
Pressure
Enthalpy
Increased
efficiency
Pressure
Enthalpy
Design
condition
Comparison of ON-OFF vs DC technology 1/2

The energy saving is given by:
•  adjustment of evaporator set point by advanced control algorithm;
•  higher thermodynamic efficiency by changing capacity according to load;
•  higher motor energy efficiency.
Estimated monthly power consumption for both types of system.
Comparison of ON-OFF vs DC technology 2/2
0

5000

10000

15000

20000

25000

Total
ConsumpJon(kWh)

DC
unit

ON-‐OFF
unit

Total energy saving of 27%
for the climate profile of
Rome.

In accordance with the new F-Gas regulation, in force as of 2014 and with the objective of reducing the
use of HFC refrigerants by 79% before 2030:
•  R404A (GWP 3920) until 1st January 2020
•  R410A (GWP 2090) until 1st January 2022
Current refrigerants used are:
•  R404A (GWP 3920)
•  R410A (GWP 2090)
Efficiency can be increased even in less favorable climates,
using the same algorithms as analyzed previously.
For condensing unit manufacturers, such a combination represents
a truly effective response to the new requirements.
Condensing
units
need
be
ready
to
operate
on
natural
refrigerants.

This
system
is
going
to
combine
the
high
energy
eﬃciency
of
DC
compressors
with
the

use
of
natural
refrigerants
such
as
CO2.

Natural refrigerants

•  Considerable energy saving results obtained by DC technology and advanced
control algorithms
•  Significant reductions in operating costs for the user, and consequently an
estimated return on investment (ROI) of 12-18 months
•  Optimum food preservation with more stable product temperature
•  Lower operating noise, making this technology ideal for installations in residential
areas
•  Wide range of remote monitoring systems in order to optimize system performance,
carry out preventive maintenance and analyze energy consumption
•  Guided configuration procedures and a vast choice of standard settings that maximize
usability
Conclusions

Thank you for your attention!

Hecu – high energy efficiency solution for condensing units fitted with DC compressors.

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