A low-carbon built environment pursuit depends on deep de-carbonization of the energy supply and using renewable energy sources. While this is well-known in principle, a switch to all electric building systems as a strategy for de-carbonization is still a new concept. The concept is simple enough, but we are now faced with an interesting transition period as technology and innovation lead to new models of electrification, distributed energy resources, and modernization of the utility grid. All-electric buildings can be designed to make best use of this electric infrastructure.
Wondering how? Read on.
Understanding the Need
To reduce carbon emissions globally, electric utilities across United States (and across the globe) have evolved with increasing percentage of renewable energy sources. In United States, the renewable energy penetration at utility scale has grown from 9 to 18% over the last 10 years. Renewable energy sources can be utility scale systems paired with storage, but there has been a surge in building level distributed energy systems. As utilities’ renewable energy portfolio and distributed renewable energy sources’ capacity continues to expand, the modern electric grid – aka grid of the future – is likely to provide electricity with significantly lower carbon emissions that support all-electric building designs.
Electric fuel mixes across regions currently vary greatly. A review of regional utility fuel mix is key in determining how much impact electrification of built environment may have on carbon emissions. Higher the penetration of renewable energy sources (or other carbon emission free fuels such as nuclear), greater will be the benefit of electrifying buildings. Comparing the national averages of some countries and regions in figure 2 below shows that generating 1,000 Btus of energy using electricity almost always leads to fewer CO2 emissions (ignoring demand side equipment efficiency such as using a heat pump or boiler). This is because most electric utilities use a mix of fuels – coal, natural gas, nuclear and renewable sources – that result in varying carbon emissions. The deep penetration of no-carbon fuel sources in utility fuel portfolio, in California for instance, helps greatly in making electricity a cleaner source of energy.
It makes common sense therefore, for buildings and communities to be equipped and designed to be able to take advantage of low carbon electric infrastructure. For distributed energy resources (DERs) such as PVs and electric storage, one can then argue that since the electric grid is likely to get cleaner, that it is better to wait for the cleaner electricity to become available instead of making expensive on-site capital investments. Need for frequency regulation, eliminating electricity transmission losses, increased resiliency provided by an all-electric infrastructure at building level are strong reasons for not just electrifying buildings, but also for future-proofing buildings with electrification and pairing with reasonable amount of on-site generation.
An Approach for All-Electric Projects
Ultimate benefits of all-electric built environment are lower carbon emissions, lower air pollution and increased resiliency. An all-electric project encompasses not just the actual buildings, but also the site including distributed energy sources. The impact of decisions made at the building & community level have serious implication on electricity transmission network and ultimately on the carbon emissions of power plants. A holistic approach that considers the constantly varying relationship between buildings (demand), distributed energy sources (on-site supply) and utility grid (off-site supply) is crucial to create a long-term low carbon impact.
One way to tackle an all-electric building project is to take a layered approach – designing buildings and communities (masterplans) with strategies that are nimble and can adapt to the changing carbon content of the grid. The next layer is to be cognizant of the effect that building / masterplan level strategies have on utility network and ultimately the power plants and be equipped to react to the utility scale demands.
At the building scale, the approach can be twofold: 1) To lower the electrical demand of buildings by using existing deep knowledge of designing ultra-low energy buildings, and 2) To design the electrical systems to respond to external signals: real-time carbon emissions, cost or energy so that the load can be manipulated. A simple example of this idea would be to delay the need for space cooling by using thermal mass or phase change materials, in order to avoid a certain hour when the carbon content of electricity is high. The same strategies and concepts used for energy efficiency and peak demand reduction for avoiding costly demand charges can be adapted for low-carbon buildings. These strategies can do double duty as the time when it is costliest to use electricity may not be the same time the carbon content is high and that is where ability to make data driven decisions becomes key. Digitization of buildings is an important tool to make data driven decisions. Digitization enables data collection and processing of data to trigger changes to building’s electric use to respond to the variability of utility’s carbon content. Being able to make changes to individual energy uses in buildings on daily basis or sometimes even hourly based on external signals is key. With demand response now becoming common, the fundamental infrastructure for the utilities to provide signals and buildings to read these signals already exists.
The next step is to simply use this setup to lower the carbon emissions related to the building. The ability to balance building demand with on-site electric generation paired with energy storage is key to maximize the use of on-site renewable energy resources. The idea here is to give buildings ability to utilize the renewable energy produced on-site for themselves and minimize transmission losses. On-site renewable energy paired with storage also enables projects to control their carbon emissions on an hourly basis, rather than depending on the grid’s carbon emissions that cannot be controlled by individual buildings. This involves selecting appropriate on-site renewable energy generation and storage technology that pairs well with building demand profile. A smart way to control these resources is to switch between utility grid’s electricity and on-site renewable energy based on the real-time carbon content. A microgrid / private network with controllers that enable this switch is critical when on-site renewable energy and energy storage are available for buildings.The last piece of this chain is recognizing the effect of building’s energy consumption on utility network and power plant’s carbon profile. Although as buildings designers we can’t control this directly, the amount of net metered electricity, major demand response strategies, and use of energy storage can lead to an unstable grid and create problems due to hours of low demand followed by a sudden surge. This was famously demonstrated in the 2015 California duck curve3 and grid or economic curtailment of German wind power in 20164. Being able to quantify and estimate these effects are therefore the last, but not the least, important task. All electric buildings can be a natural extension of a modern grid that respond to changing carbon content of the electric grid and uses it to minimize carbon emissions.
An Approach for All-Electric Projects