The second post in our series re-capping the Sustainable Built Environment Conference September 19th and 20th in Toronto will feature a presentation by Arborus Consulting group’s R. Hutcheson, S. Jorens, and D. Knapp on “Low carbon heating for commercial buildings using grid-supplied electricity during Off-peak periods.” It is a very fascinating idea that holds a lot of potential (as our notes below show). You can download the full presentation here.
-“Design approach to achieving affordable low-carbon heating solution and reap the significant economic benefits of a high quality indoor environments”
– “De-carbonizing” requires switch from fossil fuels > usually means switching to electricity. Heating in a northern climate requires a lot of energy. On-site generation is often too expensive for heating.
– Ontario’s electrical grid has mixed generation: hydroelectric, nuclear, natural gas, renewables, bio-gas. The overall “Carbon Intensity” of the grid varies according to the “mix of generators on-line” at any given time.
-The off-peak period uses little to-no natural gas, therefore it has a lower carbon intensity.
– The first step in a low-carbon building solution is a high performance envelope. This also improves occupant comfort by reducing the cool radiation from the exterior surfaces.
– With a high performance envelope the possibility now opens to heat using “low water temperature heating”… this is the highest efficiency heating delivery approach. I.e. generation via condensing boilers and delivery via radiant slab. This is the second step to a low-carbon building.
– “Ventilation is the most significant component of the building heating requirements. Using a Dedicated Outdoor Air System (DOAS) reduces volume of supply air. DOAS can be connected to CO2 monitors to shut of ventilation during un-occupied hours. Additionally they can be combined with a Heat Recovery system.
– Off-peak periods have the lowest Greenhouse Gas emissions. But using off-peak electricity requires a method of storage to meet on-peak demand. Thermal storage (i.e to use for heating later) is a good way of storing the off-peak energy.
– Water and/or other mass is a good thermal storage option. In the case of water it would be heated to eventually supply the radiant floor. Ceramic bricks can be heated to higher temperatures and require less volume (see Steffes Electric Thermal Storage system — warning the site is quite superficial)
– If all of the above options (i.e #1 High Performance Envelope, #2 Low Temperature Water Heating, #3 Dedicated Outdoor Air System + Heat Recovery, #4 conversion to off-peak electricity) it is possible to reduce the heat load by almost 64% (in a base building), but most importantly reduce the GHG emissions by almost 90%!
– The benefit is two-fold, a reduction in energy use and increased occupant comfort. If this is framed in terms of improving employee productivity, then the costs of these features will be rewarded with a very good return on investment.
Overall we feel that this idea warrants a lot more thought and ultimately we hope to integrate the idea of using off-peak electricity and thermal storage into our high efficiency retrofits (i.e we already implement the first two-three features. 🙂
