5.3 Renewables Active Systems

Approximately one-third of global final energy consumption (125 of 400 EJ annually) can be attributed to residential and service sector buildings (IEA, 2018; IEA/UN, 2018) where it is primarily used for space heating & cooling (40%) and domestic hot water production (20%). Given that most of the world’s energy is derived from fossil fuels, buildings are correspondingly responsible for ~38% of global CO2 emissions. Depressingly, emissions from buildings and the construction sector rose in2019, underlying the need to cut use of fossil fuels radically and rapidly in buildings to mitigate the climate crisis (Hamilton & Rapf, 2020). Despite technical and market advances in renewable energysystems and legislative efforts around the world to decarbonise, we remain heavily reliant on fossil fuels to meet the heating, cooling and electricity needs of our buildings. Central to this seemingly intractable problem is the “Energy Trilemma” which describes three (often competing) priorities for energy systems:• Sustainability: Increasing evidence of a worsening climate crisis together with our growing awareness of degraded habitats and biodiversity loss has led to a global political consensus that fossil fuel use must be phased out in the next few decades.• Security and reliability: Energy supplies must be dependable so that the lives and livelihoods of building occupants are not disrupted by intermittent power failures or fuel supply shortages. The global market in fossil fuels has provided a reliable supply of energy (to those who can afford it) for many decades, interrupted only occasionally by wars, civil unrest, or other political problems. By contrast, renewable energy resources (e.g., wind and solar) are typically intermittent in nature and require energy storage infrastructure to maintain supply continuity and ensure that supply meets demand.• Affordability: Energy supplies must be affordable to enable building occupants to undertake essential daily activities and maintain safe and comfortable environments. High fuel and electricity prices lead to energy poverty which retards economic development and leads to poor health outcomes (and even death) for occupants of buildings in climates where space heating or cooling is required.