Simultaneous Heating and Cooling with CO2 High-Temperature Heat Pumps

The fundamental principle of heat pumps is to absorb heat at low-temperature levels and dispense it as useful heat at a higher temperature.

A heat pump uses heat sources that are normally technically not usable. For instance, a heat pump can increase the temperature of geothermal energy from 10 °C to 40 °C. In addition to geothermal energy, it can utilise surface water and seasonal heat stores as heat sources.

But a heat pump only lives up to its full potential in terms of performance and sustainability when it converts waste heat from industrial production, exhaust air from air-conditioning systems, or waste heat from chillers and then makes it available as heat output at a higher temperature level. Using a heat pump generates significant energy savings because it optimises such processes.

With the help of CO2, a natural refrigerant – whose technical name is R-744 – it is possible to achieve effective temperatures of up to 110 °C.

This opens up applications in the fields of district heating, heat provision in industrial process and drying technology.
CO2

Standard heat pumps are usually inadequate for heating potable water. When water is heated, temperatures of 60 to 70 °C need to be achieved in order to remove the risk of legionella. These high temperatures are usually generated by means of inefficient electrical element heating.

Thermeco2 high-temperature heat pump
High-temperature heat pumps like Engie’s thermeco2 can provide both Low Temperature Hot Water (LTHW) and Domestic Hot Water (DHW) without the need for supplementary electrical heating.

CO2 is harmless to use (classified as A1), cheap to procure, and, with a GWP of 1, has no harmful effects on the earth’s atmosphere.

CO2 (in subcritical mode) has become standard for use in refrigeration – for instance, in the cooling and storage of food. 

At higher temperatures (supercritical mode), it is possible to implement heat pump applications that are highly efficient in their respective temperature ranges. Supercritical applications are a relatively new field of application for CO2 as a refrigerant.

CO2 is predestined for all applications that require cooling and heating at the same time, such as an air-conditioned hotel with a swimming pool and sauna, for example.

In the long term, a trend towards natural refrigerants seems likely, due to the F-gas Regulation, which is currently leading to restrictions on volumes of halogenated refrigerants.

Refrigeration and heat pump technology is key to the future of energy-efficient building services design. If we stop generating power from fossil fuels and instead generate it from renewable energy sources whose availability is permanently shifting, we will need storage facilities to provide load balance. Thermal storage can provide this load balance. CO2 is a highly suitable refrigerant for efficient thermal energy storage. In case of excess power in the grid, hot and/or cold thermal energy storage units can be charged with a CO2 heat pump and discharged again when power becomes scarce.

The range of CO2 heat pumps from ENGIE Refrigeration comprises eleven performance classes between 45 and 1,440 kilowatts. Currently machines in the performance class of 500 to 1,000 kilowatts are the most popular. Models are also available in a hygienic stainless steel design, making them ideal for sensitive applications such as the food industry.

Sirus are agents for ENGIE Refrigeration in Ireland, supplying and installing thermeco2 Heat Pumps – Contact us on 01 460 2600 for more information. Our Applications Engineers are on hand to discuss the suitability of CO2 High-Temperature Heat Pumps for your application.

F-gas Regulation

The F-gas Regulation published by the European Parliament and European Council came into effect on 1 January 2015. Since that date, refrigerant filling capacities have been weighted according to their global warming potential. The F-gas Regulation is intended to reduce the volumes of fluorinated greenhouse gases (F-gases) put into circulation in the EU by 79% from 2015 levels down to 35 million tons of CO2 equivalent by 2030. This objective is to be achieved by three measures in particular:
F-Gas Phase Down 2015 - 2030
  1. A step-by-step restriction of the F-gases available on the market; by 2030, they should be down to 21 per cent of the amounts generated in the reference years of 2013 to 2015 (phase-down scenario; see figure)
  2. Prohibiting the sale of refrigerants with high GWP values
  3. Extending existing regulations on leak tests, certification, disposal and labelling

GWP – global warming potential of refrigerants

The GWP value (global warming potential) is a CO2 equivalent that determines the relative greenhouse potential of a chemical compound. This measure describes the average warming effect on the earth’s atmosphere over a specific period (usually 100 years). It thereby specifies how much a defined mass of a specific greenhouse gas contributes towards global warming when compared to the same mass of CO2. For example, the GWP for the refrigerant R-134a for a period of 100 years is 1430. This means that one kilogramme of R-134a will contribute 1430 times as strongly to the greenhouse effect within the first 100 years of being released as one kilogramme of CO2.
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