high-temperature heat pumps | HiRef S.p.A.


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High-temperature heat pumps for decarbonization

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  • Technology

Year: 2023

The decarbonization process that is underway in Europe directly involves the HVAC (heating, ventilation and air conditioning) sector with challenging goals: to achieve net zero by 2050.


Clean energy and well-being for us and future generations

The decarbonization process that is underway in Europe directly involves the HVAC (heating, ventilation and air conditioning) sector with challenging goals: to achieve net zero by 2050.
For this goal to be legally binding, the Commission for Europe's Green Deal has proposed legislation on climate, energy, transport and taxation that requires net greenhouse gas emissions to be reduced by at least 55 percent by 2030 compared to 1990 levels.

This means making a commitment to reduce the amount of carbon dioxide (CO2) and emissions of other greenhouse gases (GHGs), such as methane (CH4), nitrous oxide (N2O) and fluorinated gases (F-gas) that are produced and released into the atmosphere. The expectation? To increase well-being and improve the health of citizens and future generations.

Decarbonization fully involves the HVAC sector for three reasons:

- Heating and cooling of buildings and data centers consume an enormous amount of energy.
- Air conditioning and cooling systems historically use fossil fuels or fluorinated gases (F-gas) to operate.
- Air conditioning and refrigeration involves all buildings and processes, especially industrial and technological, that we encounter in our daily lives, from the home to the workplace, sports and health care, to the products we use and the food we consume.

The net-zero carbon building

The goal is to have more and more near-zero energy buildings (NZEB, Nearly Zero Energy Building), capable of "functioning" by almost completely negating its energy needs. Even better, a NetZero i.e., zero-emission building should be designed with a view to adaptability, deconstruction and reuse through materials that can be redeveloped and have zero or less of an emissions impact, throughout its life cycle and from all sources: building, energy grid and water use first and foremost.

What areas of interest?

Firstly, the light commercial sector: residential buildings, hotels, hospitals, public service facilities and industries, whether new constructions or existing buildings to be upgraded through energy efficiency and combustion heat generator replacement.

The contingent critical issues related to geopolitical events, which are leading to rising natural gas and energy prices, are an added impetus for the divestment of natural gas and/or oil heating boilers in favor of renewable options for heating and cooling.

The key role of high-temperature heat pumps

First of all, when is "high temperature" defined? The UNI EN 14511-2: 2018 technical standard considers air-to-water and water-to-water systems with an outlet flow temperature of and/or above 65 °C.
To promote decarbonization, the heat pump is a strategic building block toward net zero.

The heat pump efficiently conditions rooms by giving up (in cooling) or taking heat from the outdoor environment to raise it to the required temperature and transfer it to the heating system through the use of electricity. This technology is sustainable because the heat pump is integrated with a unified grid such as wind, or natural source like groundwater or combined heat and power (CHP) to use zero-carbon energy. Or it can be connected to on-site renewable sources, such as where there is a photovoltaic system, or a mix of both for electricity supply.

A high-temperature heat pump can be used for both heating and cooling as well as for domestic hot water. It is capable of operating even at an outdoor temperature of -20 °C, ensuring hot water at high temperatures even under this condition.

It can also be installed in existing buildings with conventional terminals because the higher flow temperature of the indoor device allows it to supplement the radiators already in the building.

High-temperature heat pumps with natural refrigerants and Low GWP

Energy transition promotes the adoption of environmentally friendly refrigerant gases that reduce global warming potential. The new gases are sustainable and together with technological development, which leads to improved thermodynamic properties, allow the scope of application of heat pumps to be expanded with particularly interesting potential for the tertiary, industrial and data center sectors, in a smart city logic.

European F-Gas legislation envisages a gradual reduction in the CO2 emissions generated by refrigerants by 2030, indicating which can be used and which fluorinated greenhouse gases will have to be decommissioned.

(Directive (EU) 2019/1937 and repealing Regulation (EU) No 517/2014)

What are Low GWP Refrigerant Gases?

We play an active role toward energy transition, which is why HiRef air conditioners and heat pumps already use low-GWP refrigerants.

Hydrofluoro-olefins (HFOs) are the fourth generation refrigerant gases designed to meet the Kyoto Protocol's stringent greenhouse gas emission guidelines.
Among these HiRef prefers:
, a gas with a very low GWP of 7 and an ODP of 0. In high-temperature heat pumps for commercial and industrial uses, a screw compressor using R-1234ze(E) boasts a wider working range; the temperature of water produced with this refrigerant can reach up to 90°C.
is the flammability class A1 alternative to R-1234ze(E). Its GWP is 299.

The Hydrofluorocarbons (HFCs) we use include:
, which has an Ozone Depletion Potential (ODP) index of 0 and a low GWP value of 466. This is 78% less than the refrigerant R-410A, which it replaces, with also better cooling capacity and higher efficiency.
, a mixture of hydrofluorocarbons and hydro-olefins (HFCs + HFOs). Its GWP is 573, which is about 56% less than the GWP value of R-134a, making it an excellent substitute.

Among natural gases we use CO2 and hydrocarbons (HC) R-290, R-600a.

Propane refrigerant R-290
is a naturally available pure hydrocarbon that is highly flammable and explosive, so it falls under ASHRAE safety category A3. It has a very low GWP, 3, and ODP of 0.
Isobutane R-600a
is also environmentally friendly with a low GWP of 3, an ODP of 0, and it is rated A3 for its flammability. It boasts low energy consumption and can achieve produced water temperatures of up to 90°C

Toward ultra-high temperature heat pumps

In 2023, HiRef R&D developed and tested a heat pump that produces hot water up to 120°C using screw compressors, tube bundle, and R-1233zd refrigerant.

We already have a heat pump prototype in development for 2025 using Isopentane refrigerant R-601a, a hydrocarbon, which will be capable of producing hot water up to 160°C. These new products open up application possibilities toward new sectors such as cement, pharmaceuticals, paper and starch processing, dryers, and coatings with important advantages in industrial process management as well as room comfort.