SolairHP Project: First results of summer
campaign
Online, November 11th, 2021
L. Gugliermetti, M. Pieve, L. Saraceno, R. Trinchieri
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ENEA-IPSE Lab
ENEA is the Italian National Agency for New Technologies,
Energy and Sustainable Economic Development
The IPSE laboratory works on the Process
Engineering and Systems for Energy
Decarbonization

ROME

The lab is part of the ENEA’s Energy Technologies
and Renewable Energy Sources Deparment and it
is inside the Energy Production, Storage and UseDivision.
It is located inside the Research centre of “LaCasaccia” in Rome
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SOLAIR-HP
Call: Decr. 30/06/2014 ex art. 10, c 2, lett. b) D.I. 26/01/2000 per RdS 2012-2014
Funding: 1.4 M€ (cofunded)
Period: 04/2018 – 03/2022

Partners:

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SOLAIR-HP: objectives
The project is aimed at developing and testing an innovative transcritical CO2 heat pump.
The main features are:
••

•
••

Air-solar dual source CO2 HP for airconditioning of buildings and DHWproduction.
Photovoltaic Hybrid Solar Panels(PVT) used as thermal exchanger
directly connected to refrigerant.
Six operative modes (cold, heat,DHW and mixed)
7÷10 kW of thermal power
GWP = 1

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SOLAIR-HP: Placement
Placement:
ENEA Casaccia - Roma
The Heat Pump is located at the Research Centre of«La Casaccia» in Rome.
The system is installed in an open environment tosimulate the real operative conditions.

Auxiliaries:
The heat pump is supported by auxiliaries system able
to:• Dispose up to 7/10 kW of thermal power (cold/hot),• Cold and Hot tanks (300 and 500 l),• Fine control of mass flow rate by means of
bypasses and pumps inverters.

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SOLAIR-HP: Schematics
The schematic of the SOLAIR-HP is visible in figure. By using the three-way valves it is possible to switch theoperative mode of the heat pump. The system is composed by several components:• Heat Recovery Exchanger: to increase the superheating of
the fluid before the compressor• Lamination valve: to control the upper system pressures• PVT exchanger: to improve system efficiency using the sunirradiation• Air finned coil: alternative to PVT exchanger• Cold and hot storage tank: for thermal storage purposes• Inverter controlled compressor: to control the system powerand efficiency

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SOLAIR-HP: Operations
The heat pump can be operated in 6 different modes depending on what it is wanted to produce.

#1-2 «Winter» Heating with DHW  H2O at Tmax 60 °C#3-4 «Winter with PVT» Heating with DHW  H2O at Tmax 60 °C using the PVT#5 «Summer» Cooling with water at 12-7 °C#6 «Heating and Cooling» Cold and Hot water Tmax 60 °C and Tmin 7 °C

IT Workshop for IEA-HPT ExCo MeetingModes #1-2: «Winter»#1-2: «Winter» Heating with DHW  H2O at Tmax 60 °C
Loop layout:

Hot exchanger

Heated Water

Cycle:

Recovery

Air Finned
Coil

Lamination
valve

Compressor
Receiver/Separator

IT Workshop for IEA-HPT ExCo MeetingModes #3-4 «Winter with PVT»
«Winter with PVT» Heating with DHW  H2O at Tmax 60 °C using the PVT
Loop layout:

Hot exchanger

Heated Water

Cycle:

Recovery

Lamination
valve
PVT

Compressor
Receiver/Separator

IT Workshop for IEA-HPT ExCo MeetingMode #5 «Summer»#5 «Summer» Cooling with water at 12-7 °C
Loop layout:
Cycle:Air Finned
Coil

Recovery

Lamination
valve

Cooled waterColdexchanger

Compressor

Receiver/Separator

IT Workshop for IEA-HPT ExCo MeetingMode #6 «Heating and Cooling»#6 «Heating and Cooling» Cold and Hot water Tmax 60 °C and Tmin 7 °C
Loop layout:

Hot exchanger

Heated Water

Cycle:

Recovery

Lamination
valve

Cooled waterColdexchanger

Compressor

Receiver/Separator

IT Workshop for IEA-HPT ExCo MeetingResults: #5 mode
Period: 24/08/2021 – 01/10/2021
Mode: #5 «Summer»
Environmental temperaturesCompressor frequency effectTmin 23,2 °C
Tmax 32,1 °C
Tavg 27,5 °C

IT Workshop for IEA-HPT ExCo MeetingResults: #5 mode
Energy Efficiency Ratio Vs compressor frequency and fan speed•The EER depends on fanspeed and compressorfrequency.

•There are no improvements toincrease fan speed after a
specific point (depending onthe compressor frequency)•

Environmental temperature
affects negatively the efficiency

Going under 50% of compressor can damage the heat pump

IT Workshop for IEA-HPT ExCo MeetingResults: #5 mode
Energy Efficiency Ratio Vs compressor frequency and fan speed•

At higher compressor
frequencies the EER lowers•

The optimal fan speed increases
with the compressor frequency•

Environmental temperature
affects negatively the efficiency•

The effect of environmental
temperature lowers at highcompressor frequency

Going over 80% of compressor was not necessary due to the target coolingpower of 10 kW

IT Workshop for IEA-HPT ExCo MeetingResults: #5 mode
Total cooling capacity and the ERR at different compressor speeds and fan speed•

Data showed at the sameenvironmental temperature•

At higher compressor
frequency the EER lowers•

Cooling power rises with thecompressor speed with a goodregulation•The ERR reaches its maximum
at 80% of fan speed, the airfinned coil is oversized•

The cooling power reaches itsmaximum at 80% of fan speed,
the air finned coil is oversized

IT Workshop for IEA-HPT ExCo MeetingResults: #5 mode
Automatic and manual lamination valve control comparison•

The lamination valve can act
manually or automatically incooling mode•

The percentage represents
how much the valve is open•

The automatic control works
quite well•With manual control a higher
power is possible but with alower EER•

Closing too much the valve canlead to overtemperatures

Data showed at 60% of compressor frequency and 70% of fan speed

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Conclusions
Innovative sun-assisted CO2 transcritical heat pump
- Eco-friendly refrigerant (GWP = 1)
- Max renewable share exploitation- Integration with solar panels

Test on summer mode (conditioning)
EER and its relation with compressor frequency, fan speeds andlamination degrees
DHW and cooling water tests ongoing (mode #6)
Winter test will be made during upcoming winter (innovative PVT usage)
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Contacts:
raniero.trinchieri@enea.it
maurizio.pieve@enea.it
luca.saraceno@enea.it

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