*2.2. Inventory Data*

The life expectancy of the whole system (20 years) and corresponding components was obtained from existing literature and warranty documents produced by manufacturers (Table 1). A sensitivity analysis has been performed to assess the effect on the environmental impacts of changes in the life expectancy of the S-LHTES-PCM system (see Section 2.3). The S-LHTES-PCM system reaches a solar fraction of heat supply equal to 56% [19]. Since the total annual energy consumption of the house is 3723 kWh [11,19], this means 2085 kWh are provided by the S-LHTES-PCM system (41,700 kWh in 20 years). It is worth noting that the annual energy consumption of 3723 kWh is typical of a low-energy single-family house built according to the passive house standard located in a Danish climate (similar weather conditions as in the UK). The total energy consumption is the sum of two contributions: the space heating demand (2031 kWh) and the domestic hot water demand (1692 kWh) [11,19]. To calculate the domestic hot water demand, a daily water consumption equal to 99 L/day was considered (33 L draw off at 7.00, 12:00, and 18:00), assuming a supply temperature of 50 ◦C and a cold-water temperature of 10 ◦C. The space heating demand was calculated on an hourly basis using a building energy simulation tool and the weather data of the Danish climate (similar weather conditions as in the UK). The space heating system was a low-temperature system (floor heating).

The inventory data for the S-LHTES-PCM system is detailed in Table 2. Scientific articles have been used as the main source of primary production data, including the amount and type of raw materials and the electricity and heat consumption during production [11,19,20]. Where there was no information available in the literature, the manufacturer's product catalogues were consulted [21–23]. The database Ecoinvent v3.7 [24] was used as the primary source for background data, while the NREL USLCI database [25] was used to fill data gaps. The following sections describe the inventory data in more detail.

**Figure 1.** System boundaries for a latent heat thermal energy storage system with phase change materials (PCM), including solar collectors and hot water tanks. (Other materials include rubber (solar collector) butyl acrylate (expansion vessel), acrylonitrile butadiene styrene (stratifier and activation device) and cast iron, aluminium, and polyvinylchloride (pumps)).

**Table 1.** Lifetime expectancy of all the components used in a solar energy and latent heat thermal energy storage system with phase change material.


**Table 2.** Inventory data for a solar energy and latent heat thermal energy storage (S-LHTES) system with phase change material (PCM). All values are expressed per 1 kWh of heat produced by the system.


<sup>a</sup> Other materials: Rubber (solar collector) 0.4 g; butyl acrylate (expansion vessel) 0.2 g; cast iron (pumps) 0.4 g; aluminium (pumps) 0.006 g; and polyvinchloride (pumps) 0.01 g and acrylonitrile butadiene styrene (activation device and stratifier) 0.04g.
