HEAT PUMPS AND REDUCTION OF DEPENDENCE ON NATURAL GAS

THE RESULTS OF A STUDY SHOW THAT HEAT PUMPS IN A RESIDENTIAL ENVIRONMENT COULD BE CRUCIAL IN A DECARBONISATION PERSPECTIVE. TO GET THEM OFF THE GROUND, A LONG-TERM STRATEGIC PLAN WOULD BE NEEDED

Michele De Carli*, Marco Marigo*, Laura Carnieletto* and Filippo Busato**

*Università degli studi di Padova

**Università Mercatorum Roma. Presidente AiCARR

In 2007, the 4th Assessment Report (chapter “The physical science basis”) of the IPCC (Intergovernmental Panel on Climate Change) established the anthropogenic responsibility of climate change due to the accumulation of CO2 in the atmosphere.

A few years later, Figure 1 appeared, “the figure that changed everything…” (Macchi, 2022), which illustrates with disarming evidence how the concentration of carbon dioxide in the atmosphere has increased indisputably (observe the last section, which is almost vertical) due to human activities and the development of energy demand that resulted after the industrial revolution. The need for decarbonisation is therefore not one of the possible scenarios, it is an imperative. To the environmental aspect, which is far from negligible as it could cause objective difficulties for humankind (starting from the agri-food sector), the geopolitical factor has recently been added, with a war that threatens, among other things, the security and the conditions of supply of natural gas in our country. From these considerations comes an investigative stimulus on the contribution of heat pumps in the residential sector to the decarbonisation of Italy. This analysis, which is addressed to our nation and cannot and should not be generalised, has fallen into the specificity of gas consumption in the residential sector and the climatic and urbanisation variety of the peninsula, which must be taken into account in the interpretation of the most suitable plant solutions in the different areas.

Natural Gas Consumption For Residential Heating

Natural gas consumption in the residential sector is 19.7 billion cubic metres (ARERA Source) [1]. The use made of gas at the residential level is about 80% for heating needs, while the remaining 20% can be considered divided between domestic hot water production and cooking food.

On the basis of regional gas consumption for distribution networks and taking into account climatic conditions, gas consumption was distributed at regional level. In this way, it was possible to find an indicative value of gas consumption per building, also taking into account the ISTAT data of population, residential area and average household composition [2]. The gas values, broken down regionally and by residential unit, are shown in Figure 2 in terms of specific energy.

HEAT PUMPS FOR HEATING: STATE OF THE ART

High-temperature heat pumps normally use the R134a fluid (Figure 3) which allows for greater temperature differences between evaporation and condensation than the R410A fluid normally used for medium and low-temperature plant terminals. Given the low heat demand in climate zone B and the low incidence of radiator installations in this area, it can be assumed that heat can be supplied by direct expansion or medium and low temperature machines. In climates C, D, E and F, on the other hand, it is assumed that systems with existing radiators and boilers are present. In these cases, for a high-temperature heat pump (usually with a scroll compressor) it could be possible to work at a limit of 70 °C of delivery temperature for the radiator system with 0 °C of external temperature. This temperature would therefore make it possible to meet energy requirements of up to 0 °C in all climatic zones. In climatic zones C and D, therefore, it is possible to cover all the energy needs required by the building by means of a high-temperature heat pump (as highlighted for a sample building shown in Figure 4 In climatic zones E and F, it may be possible to cover the energy requirement of the building by means of a high-temperature heat pump up to 0 °C for climatic zone E and up to -1 °C for climatic zone F (as highlighted for a sample building shown in Figure 5). Under these conditions, based on some work carried out on different archetypes, it can be said that it covers about 87% of the energy needs for a climatic zone E, while it reaches 72% of the total winter thermal needs in a climatic zone F, assuming that it works cautiously in alternating operation.

INTENSIVE USE OF HEAT PUMPS IN RESIDENTIAL HEATING: SOLUTIONS FOR DIFFERENT CLIMATES

Taking into account the coverage of heating needs with the above values, an analysis was carried out to verify the coverage for heating in the different regions. This first analysis did not consider the possibility of generating

Potenza degli edifici e fornita dalle PDC per un alloggio tipo

FIGURE 5. Average power required by the building (solid line) and average power provided by a heat pump (dotted line) that meets the thermal peak under 0 °C design conditions for climatic zone E (green) and F (blue) domestic hot water with the heat pump, nor the effect of the introduction of induction plans on decarbonisation at national level. The result achieved led to a 72% reduction in gas in the residential sector, corresponding to 14.2 billion Nm3 of gas. The result is very relevant because climatic zones F weigh less than other climatic zones representing areas with less population than other climatic zones. Considering an average COP of 2.8 for heat pumps, it would mean a reduction of 87 TWh of final energy (-64% of energy), 25 TWh (-18%) of primary energy, 48 TWh of non-renewable primary energy (-34%). This result means an increase in electricity consumption of 48.6 GWh, which is 17% more than the Italian electricity production of 2020 (280 TWh). With regard to costs, considering 0.86 €/Nm3 of gas and 0.25 €/kW, the conversion from boilers to heat pump would not lead to a significant difference in costs. However, the conversion from natural gas to heat pump would lead to an 18.7% reduction in natural gas in Italy, resulting in less dependence on states with reduced political stability.

A POSSIBLE FIVE-YEAR PLAN

The average installable power per housing is about 3.3 kW, which would result in a maximum installable power of 33 GW of installable thermal power. Assuming a cost of €2,000/kW for the heat pump alone and €1,500/kW for the installation, this would mean €67 billion for the production of heat pumps and €50 billion of finance directed to the plumbing sector and manufacturers. Considering the current turnover of the heat pump sector (€2.5 billion), this means that if you want to achieve the installation of heat pumps throughout the residential sector you would need to quintuple the current production of heat pumps, a goal that could be achieved if there was the political will to do so. To this end, it is necessary to think about different incentive options for the installation of these products, as well as the production and supply of standardised systems facilitating the design (of machines and the thermotechnical planner) and the installation of production systems. The plumbing sector today counts for about €20 billion, therefore the installation should not be a problem, although it is also necessary in this case to increase the manpower for this sector.

DECARBONISATION AND REDUCTION OF DEPENDENCE ON NATURAL GAS: RESULTS IN THE MEDIUM TO LONG TERM

If the prospect of decarbonisation sees a decisive contribution in the adoption of heat pumps as a generation system, it must be framed within a slower process, but with which synergy is created, of energy requalification of buildings. In addition to stimulating demand, however, it is also necessary to consider the industrial and productive aspects for which it is necessary, as is being done for renewables, to launch ambitious and long-term policies.

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