It’s All About Timing: How to Minimize Carbon Emissions from Grid Electricity
A Follow-Up from Greenbuild 2021 by Paige Colao
We all know that using energy produces carbon emissions. But did you know when you use energy is almost as important in reducing carbon? This is the concept explored by “The Future of the Grid and its Impact on Buildings” presentation at Greenbuild 2021* (Richardson, et al. 2021).
Every year, buildings are becoming more energy efficient through new technology, and the grid is getting ‘cleaner’ as more renewable electricity is being produced. The net effect of both these actions – reducing the amount of energy used by buildings and more grid electricity coming from renewable sources – is reduced carbon emissions from building operations. But that’s only half the picture. We need to start thinking about how emissions from grid-purchased electricity are dynamic, like the weather – something that changes every day, changes with the seasons, and depends on the region.
Grid electricity is created by several different types of sources – coal fired power plants, nuclear power plants, hydropower, solar farms, wind farms, and more. Depending on the time of day, the time of the year, and what region of the grid, carbon emissions from electricity production change. Different types of electric producers come ‘on and off’ the grid at different times. Electricity from solar, for example, is only being created during the day. Using the same amount of electricity in the day would produce fewer carbon emissions than using the same amount of electricity at night. Similarly, electricity production from renewable sources can change based on the time of year. In the northern hemisphere, there is more solar electricity generation in the summer than in the winter because there are more hours of daylight.
What this means is simple: carbon emissions from electricity usage depend on not only how much grid electricity a building uses, but also when it uses that electricity. This causes a conundrum for designers and facility managers. The ‘cleanest’ times of day for the grid are often not the times in which we use the most energy in our buildings.
What can be done? In short, limiting electricity shifting energy loads to cleaner times of the grid, designing for responsive energy systems, and charging/storing energy.
Here are some strategies for facility or property managers:
- Shift when electricity is used to cleaner times on the grid
- Use majority of energy from 10 AM – 2PM
- Use as little energy as possible from 5 PM – 9 PM
- Consider grid-interactive software which can respond to price, demand, and emissions signals
- Look at carbon emissions from the grid in real time from websites like electricityMap or WattTime and adjust energy usage accordingly
- Sync devices with compressor cycles to cleaner moments (refrigerator example in the slide below) (Richardson, et al. 2021)
- Thermal or battery storage: e.g. topping up very insulated hot water tanks or charging large batteries during cleaner times of the grid can allow users to deploy that energy on demand when the grid is less clean
What can developers do to reduce carbon emissions from buildings which use grid electricity?
- Maximize on site renewable energy
- Design buildings based on the emissions profile of their part of the grid, and making sure energy use can be flexible (e.g. turn on or off when the grid is clean/dirty)
- Design in-building thermal storage, battery storage
- Design all electric buildings with geothermal or air source heat pumps, but try to reduce electric resistance heat as much as possible
- Consider electrochromic glass
- Consider dynamic responses to maximize energy efficiency
- Economizer cycles
- Controls that respond to weather
- In-floor sensors for thermal mass
- Automatic window actuators and blinds
- Grid-interactive software which can respond to price and demand signals
This presentation was fascinating and packed with new insights to share with our Pittsburgh and Erie 2030 District partners. We’ve known for some time that electrification is essential to decarbonizing our building operations – the next step is making sure our buildings can respond to grid emissions for even greater carbon reductions.
*Richardson, H., Torcellini, P., Kaneda, D., & Turnbull, P. (2021). Greenbuild International Conference and Expo. In Greenbuild 2021. San Diego, CA; Greenbuild & USGBC. Retrieved October 22, 2021, from https://vimeo.com/608581179.