At the United Nations Climate Change Conference in Paris in 2015, countries agreed to keep a rise in global temperatures “well below 2 degrees C” above pre-industrial levels and to “pursue efforts to” limit the temperature increase to 1.5 degrees C.
Subsequently, the Intergovernmental Panel on Climate Change (IPCC) was invited to provide advice on the impacts of global warming of 1.5 degrees C, with the aim of strengthening the response to the threat of climate change. The resulting IPCC Special Report was published in October 2018.
Anthesis was privileged to be invited to the Royal Meteorological Society Conference in Westminster to explore the implications and challenges detailed in the IPCC report. There are significant implications for the built environment and building energy systems.
Setting the scene
The following should first be understood:
- Discussions and the setting of a 1.5 C or 2 C temperature rise target are political in nature. The scientific community has not set these targets, neither has it declared that they are ‘safe’ with respect to risks to the climate system. However, the scientific community is defining what the likely impacts are in certain contexts at these temperatures
- Some impacts are very directly related to temperature rise e.g. risk of wildfires, risk to coral reefs. Some are less so
- Some environmental systems may be resilient to relatively short periods of higher temperatures some are not. E.g. if a high climate change temperature occurs for a short duration (e.g. 5 to 10 years), then falls back from mitigations this may wipe out most coral reefs, which cannot grow back even after a ‘short’ duration event
- Any reductions in global warming reduce risk to the environment and reduce the cost of adapting to this risk
Action required in building energy systems to achieve 1.5 C
With these consequences in mind, we can consider the action required in building energy systems to achieve a 1.5 C target. These are briefly considered in the IPCC Meeting a Global Temperature of 1.5 degrees C presentation, which also makes the following key points:
- Change needs to be rapid – defined as the next 10 years
- Change is required in all systems
- Change needs to be stringent
This means any technology not currently deployed on a commercial basis is an unlikely solution to the problem. No one sector can solve the problem, but all need to contribute. And the change and improvements in performance need to be measurable and demonstrable. The implications are:
- No reliance on magic bullets. For example, a simple switch to hydrogen from natural gas is not likely to be feasible in the timescale, as this is technology yet to be commercialised, although it may have a role in the medium to long term
- All aspects of the built environment (e.g. manufacturers) will need to address climate change in their technologies, manufacturing approach and distribution systems
- More metering and monitoring will be required to understand and measure system performance and close the performance gap
With respect to the key strategies required to ‘transition’, the IPCC presentation focuses on the energy sector, which has a logical extension to the built environment.
1. Energy Efficiency
With a requirement that final energy demand remains relatively static or even falls compared to 2010 levels. For the built environment this will likely mean:
- Insulate new and existing buildings, to reduce space heating demand. An interesting approach proposed by Denmark is the concept of the ‘Economic level’ of insulation in buildings. This is the level of insulation required in existing and new build structures (a different figure applies to each category) to minimise demand to the point it is more economic to install a renewable heating system over more insulation.
- Increased use of heat pumps, over direct electric heating. Direct electric heating may be applicable in small point of use applications and for temporary use (e.g. cabin type heaters), but the requirement for an increased level of energy efficiency will drive the use of heat pumps in many larger systems. This may be promoted by the increased relative price in electricity, already forecast by some parties to increase by 50% in real terms over the next 10 years to pay for existing electrical renewable energy policies
- Increased use of storage, including thermal storage (water or fabric based). This may be in part driven by the use of heat pump systems, but will also be required to smooth out demand and improve system efficiency. Ground based thermal energy storage is also one of the few current technologies that can store renewable energy interseasonally.
- The use of Heat Networks, to allow the distribution of waste heat across the urban environment. Waste heat may arise from cooling, dispatchable power generation, energy from waste or industrial processes, capturing and using this will be a key energy efficiency requirement.
2. Electrify Energy End Use
The key issue not addressed by the IPCC report is the mechanism of energy distribution. Most of the UK’s building energy is distributed by the gas, not the electricity network. Therefore, the following observations are relevant to this statement:
- Direct electric heating is unlikely to be the solution, because of the energy efficiency driver
- Transport (vehicles) are also electrifying, and may electrify faster than building heating systems. Both are competing for existing electrical energy supply and in theory, low cost off peak electricity. There is a limited availability of this, whichever demand gets there first will win the ‘land grab’ for it. In doing so it may mean that UK electricity demand is flattened and ‘low cost, off peak’ is no longer so ‘off peak’ or ‘low cost’. For air-based heat pumps the performance loss arising from operating in the cooler night hours also needs to not exceed the cost saving from operating on any ‘low peak’ electricity.
- Heat pumps are likely to be key as an energy source, however changes to refrigeration systems are likely to drive users towards water based systems. Energy efficiency for machines tends to increase with scale, therefore it is likely heat pumps will also contribute to district systems, particularly when seeking to couple a high temperature source (e.g. industry, sewage heat recovery, water source or large scale ground interseasonal heat storage) with demand
- Where energy density or electrical supply restrictions merit it, energy distribution between buildings for heating and hot water is likely to be water based. This may be in the form of ambient loop, or conventional district systems.
3. Decarbonising the Power Sector
The built sector may contribute with embedded generation i.e. more roof mounted PV, and in some circumstances local wind turbines, however the built environment is reliant on the centralised power system. This is likely to require substantial investment in the electrical distribution network and additional renewable energy generation, both of which are likely to increase the real price of electricity.
The trickiest problem to tackle is the requirement for dispatchable power generation i.e. controllable power on demand. Batteries may help with some of the day to day variations in power supply and demand, but are unlikely to solve the wider system problem, or provide interseasonal storage for excess solar generation in summer for use at points of maximum demand all associated with winter.
4. Substituting Residual Fossil Fuels with Low Carbon options
Dispatchable power generation currently involves either hydro power (geographically limited in the UK) or a combustion based system. Alternative fuels include energy from waste, and biofuels (biogas, wood, crop residue, sewage sludge etc). We have excluded nuclear energy for the purposes of this piece because of other associated political and engineering issues. Combustion based systems naturally entail some nitrous oxide (NOX), particulate matter (PM) and black soot emissions, and these also need factoring into the wider climate change debate, as well as the air quality challenge facing the urban environment.
Again, these options are probably best dealt with centrally, rather than on a building by building process, either through exhaust treatment or possibly carbon capture and storage. However, it should be noted that these systems will by the nature of their operation produce waste heat, therefore a wide area water based distribution system will likely be key to move heat from these centralised or decentralised sources to buildings which are heat users.
- Rapid change is required in the built environment to mitigate the risk of climate change
- The built environment, as a key energy consumer, has a significant role in mitigating this risk
- Measurement and monitoring will be key to see where we are and how we improve
- Equipment electrical efficiency, the measured electrical carbon factor and electricity cost will likely dominate building design considerations and real carbon performance in the medium to long term
- Thermal and battery storage will be required to smooth out demand, but currently, only geothermal storage can help solve variations in interseasonal energy demand
- Heat pumps are likely to play a key part in decarbonising building heating. These are likely to be producing heat as low grade temperature hot water
- We are likely to see more low temperature water networks to make better use of the low grade heat from heat pumps and other waste heat sources
- Interconnection of waste heat sources with heating demand is likely to drive district and communal heating system development in certain areas
- The expansion of electrical supply and distribution infrastructure (with their associated waste heat sources)will be a key determinator in the cost and selection of different heating system approaches for existing and future buildings
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