Abstract
Within the European Union, buildings account for around 40% of the energy use and 36% of CO2 emissions, thus representing a significant challenge in the context of recent EU directives that require all new buildings to be nearly zero-energy by 2020. Reduced consumption of water, and hot water in particular, provides a significant opportunity to reduce energy consumption. While there have been numerous studies pertaining to the water-energy nexus of residential buildings, the complexity of water networks in larger buildings has meant that this area has been relatively unexplored. The paper presents a comprehensive investigation of the hot water use profile, associated energy use, on-site pumping energy use, carbon emissions, and solar energy harvesting potential in an Irish university building over periods before and after water conservation efforts. Total water-related energy consumption (including the heating and pumping losses) were analysed using the WHAM model and modified pumping energy expressions. The results revealed that water heating including losses contributed to as high as 30% of total building energy consumption, and stringent water conservation measures reduced the average hot water use rate by 8.5 m3/day. It was found that 10% of the total pumping energy was constituted by pump start-ups. Simulation results for solar harvesting potential in the study site found that around 60% of water heating energy demand could be met by solar energy in the new water demand scenario. The study results can act as a benchmark for similar buildings, and the model combination can be emulated in future studies.
Highlights
The energy and water performances of buildings are two main legislations of EuropeanUnion (EU)
That means that with a small area, and with a little investment, the system could yield more than half of the heating energy demand. These analyses showed that water conservation helped to reduce energy use in the building, and to reduce the infrastructural and installation costs of renewable energy systems in the building—albeit the present solar energy system (20 kWh/day) installed in the building was insufficient to meet the daily water heating energy demands except for on weekends
This study has conducted a comprehensive characterisation of water-energy interactions in a large building before and after implementing water conservation measures, which was lacking in previous papers
Summary
The energy and water performances of buildings are two main legislations of EuropeanUnion (EU). The energy and water performances of buildings are two main legislations of European. According to the European Commission [1], buildings constitute around 40% of the energy use and 36% of CO2 emissions in EU; its directive on energy performance of buildings requires all new buildings to be nearly zero-energy buildings (nZEB) by 2020. In Ireland, all new buildings will have to achieve a 60% improvement in energy performance by 2020 from current levels, and 20% of the primary energy use must be supplied by renewable energy sources [3]. For all existing buildings in Ireland, major renovations (more than 25% of the total floor area) must be carried out to achieve the nZEB targets [3].
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