SUSTAINABILITY
Winter
HP
HP
HP
RU
RU
Heating radiator
Radiant panels
Heating battery (water)
Heating battery (water)
Domestic hot water (clean)
Dirty water
recovery Heat
Hot water (clean)
Dirty water heat recovery
Summer HP HP HP RU RU
Aerothermal or
geothermal HP HP HP
mode from cold
Hot
Cooling mode with recovery
RU RU Aerothermal
Thermal solar panels
Figure 7. Winter/summer distribution of energy production equipment.
low-temperature heating solutions which until then were unsuitable, like heat pumps. Indeed, while heat pump-type thermodynamic machines offer outstanding performance at low temperatures (up to 45˚C/50˚C), their performance collapses at high water temperatures. As a result, it becomes worthwhile to
separate heating production from domestic hot water production, as it requires a minimum temperature of 60˚C. After identifying combined heating and
cooling needs in order to optimise the installation’s performance, it is preferable to install refrigeration units with water condensers to recover available thermal energy, rather than release it into the environment. The use of storage tanks can absorb slight differences in phase and maximise the use of this recovered energy. This combination is analysed on a seasonal level but also day to day to balance needs between day and night (Fig 6). The association of these energy
recovery refrigeration units with reversible heat pumps (operating in heating mode in winter and air conditioning mode in summer) helps limit or even reduce investment, thanks to the partial pooling of hot and chilled water production, while securing the energy supply. Heat pumps supplying heating in
winter will switch to air conditioning mode in summer. A single pump will be kept in heating mode, notably to cover reheating needs after dehumidification. If a heat pump or unit fails in summer, all heat pumps will switch to air conditioning mode, and the energy recovered from refrigeration units will cover residual heating needs (Fig 7). This partial redundancy of equipment
associated with the site’s secure electricity supply (power generators, Enedis supplies, high voltage loops) ensures a continuous heating and cooling supply. In this production diagram, geothermal solutions – until now rarely used due to their investment cost – become financially relevant due to the energy savings created by optimising the performance of heat pumps and subsidies that can be
IFHE DIGEST 2024 Cold battery Fan coil
Cooling equipment
Figure 8. Simplified diagram type associating reversible heat pumps and recovery refrigeration units.
received via the Fonds Chaleur. A good understanding of the heating capacity of the subsoil allows drilling to be calculated in accordance with thermal characteristics and sustainability: For geothermal probes, the annual review between recovered and returned energy must be balanced to ensure resource sustainability. Production is supplemented by air condensation refrigeration units for peak needs in summer (Fig 8). As indicated previously, there must be a special focus on domestic hot water production. Other than pre-heating through refrigeration unit energy recovery (insufficient to reach a temperature of 60˚C), production can be covered by high-temperature heat pumps. However, as high-temperature heat pump performance is mediocre at low outdoor temperatures, it is preferable not to use outdoor air directly as a cooling source, but to use an intermediate mid- temperature network to improve performance and achieve satisfactory results. With this aim, DHW production by heat pumps is paired with hybrid solar panels combining photovoltaic and thermal energy, a technically appealing solution. The heat released by the photovoltaic cells is absorbed by a water loop limiting
4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
Typical hospital
their rise in temperature, and thus extending their life span and ensuring stable performance over time, while the electricity produced supplies the High- Temperature HP supply and distribution pumps. The recovered heat is used in the same way as in a conventional solar thermal system.
Conclusion Following an initial stage to improve the envelope and implement effective waste energy recovery systems that has reduced the energy consumption of the hospital buildings, a new phase is underway to transition to zero-carbon energy sources. This will help to drastically reduce the carbon emissions linked to the energy consumption of the healthcare facilities. This means that their initially significant carbon footprint will become insignificant compared to the carbon footprint from construction. Efforts will then be focused on savings in terms of construction materials and, notably, the use of biosourced materials. Combined with limited land development, the ambition to reduce carbon emissions will also result in a significant increase in energy and functional renovation operations at existing buildings and sites in the future (Fig 9).
Approximate carbon impact of a hospital over 50 years
Performance envelope:
•Reduced heating and cooling needs
•Efficient systems
•Recovery of waste energy
Frugal hospital
Current transition
Use of carbon- free energy sources:
•Electricity
•Renewable energy
Low-carbon hospital
n Goods and services n Energy n Water n Development Figure 9. Changes to a hospital’s carbon footprint over time. 21
Decrease in materials:
•Reduction of basements and the use of concrete
•Use of
biosource materials
Hospital using low impact materials
IFHE
Tonnes CO2
/M2
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