SUSTAINABILITY


energy into thermodynamic energy through water evaporation and steam pressurisation, then into mechanical energy by moving a rotor to obtain electricity by creating an electromagnetic field.


In France, the electrical mix – i.e. the


distribution of different sources of primary energy to produce electricity – is significantly dominated by nuclear and renewable energy. As its composition is mainly from nuclear and renewable energies, French electricity has a low carbon footprint (Fig 4). It should be noted that, at a given time


– ‘t’ – the energy mix of electricity varies. In winter, to cover additional heating demand, RTE needs to fire up gas-fired thermal power plants, mechanically increasing the carbon footprint of a consumed kWh. In France, the average carbon footprint of an electrical kWh depends on usage (Table 2). With regards to UHNs, each network


has its own energy mix, and therefore the carbon footprint of the kWh is unique to each facility. These values are regulated and published in the annexes of the decree of 15 September 2006 on the energy performance diagnosis (Table 3). Once the consumption profiles are


known, sources of renewable and waste energy identified, and the region’s energy supply mapped, it is possible, based on a range of energy production types, to build technical architecture unique to the project.


Technical architecture of energy production Before offering an example of technical architecture, we will explain some production principles adapted to use for healthcare buildings.


Production principles l Production of solar DHW:Within renewable energies, solar can be used in healthcare facilities in various ways. Given the regular and relatively


600,000 500,000 400,000 300,000 200,000 100,000 0


Cold source


Compressor


pressure steam


Low


Cycle reversal valve


pressure steam


High


source


Hot


pressure liquid


Regulator Figure 5. How a heat pump works.


significant needs for domestic hot water, linked to accommodation departments (around 50 litres of domestic hot water per day, per bed), thermal solar energy is particularly well suited to any type of healthcare facility (nursing home, follow- up and rehabilitation, hospital, etc.). Solar energy can be used directly through a transfer via heat exchangers or combined with intermediate heat pumps allowing a back-up source to be avoided (or at least to limit its use). In particular for direct transfer, the size of the installation must be calculated with low consumption assumptions to avoid any overheating likely to cause damage to the solar panels. Photovoltaic solar energy is a simple,


relatively cheap solution that is separate from the facility’s operations, which can be consumed on site or resold, and whose installation can potentially be entrusted to a third-party investor. Finally, so-called hybrid solar panels


combining photovoltaic and thermal energy are quite an appealing technical solution. The heat released by the photovoltaic cells is absorbed by a water loop, limiting their rise in temperature, and thus extending their life span and ensuring stable performance over time. The recovered heat is used in the same way as in a conventional solar thermal system.


Breakdown of cooling consumption


300,000 250,000 200,000 150,000 100,000 50,000 0


Low


pressure liquid


High


l Heat pump and recovery refrigeration unit: To properly appreciate the recovery potential of a healthcare facility, we must understand how a heat pump works. A heat pump (or HP) is a thermodynamic machine working on the principle of energy exchanges when a fluid changes states. In addition to the energy required to raise the temperature, it takes additional energy to change from one state to another; from liquid to gas. For liquid water, a quantity of energy is provided to raise the water’s temperature to 100˚C; sensitive heat. Then once at 100˚C, another quantity of energy is injected to transform liquid water into gas; latent heat.


Using an electrical source, an HP


alternates between rest (liquid to steam, capturing energy) and compression (gas to liquid, returning energy) phases to transfer energy from one place to another. So in refrigeration unit (RU) mode, an HP absorbs energy from a cold source to cool, to return it to a hot source. This waste energy is either recovered or lost. The HP works by exchanging with water (groundwater, a distribution network), the ground (geothermal probe), or air (released waste heat) (Fig 5). From an energy point of view, a heat pump at full load produces around 3 kWh of refrigerating energy (EER) and 4 kWh of thermal energy (COP) from 1 kWh of electricity.


Suggested zero-carbon technical architecture for a hospital site The example of technical architecture proposed below corresponds to an architecture designed for a hospital in the Paris region with a surface area of approximately 20,000 m2


, with a surgical


department with around ten rooms, a critical care unit, and over two hundred inpatient beds. In recent years, controlling the


building’s envelope has helped drastically reduce heating and power needs of emitters and encouraged the creation of


Breakdown of heating consumption


n Cooling consumption covered by heat pumps n Cooling consumption covered by refrigeration units


n Heating consumption covered by heat pumps n Heating consumption covered by recovery from refrigeration units


Figure 6. Estimated distribution of coverage of heating and cooling needs of a hospital building between HP and energy recovery RU – considering 80 per cent recoverable recovered energy.


20 IFHE DIGEST 2024


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January February March April May June July August September October November December


kWh


kWh


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