Takeaways from the 2015 ASHRAE Energy Modeling Conference
I recently took part in the first annual ASHRAE LowDown Showdown modeling challenge sponsored by the Department of Energy and the National Renewable Energy Laboratory. I was on the IES VE Team which won the Best Energy Use Results Award. We partnered with eight other energy modelers from other leading performance simulation firms across the country to create a Zero Net Energy Building. It was a great competition and I am excited to share my experiences from this fantastic learning event.
ZER0 NET ENERGY (ZNE) COMPETITION
Each team was given the same challenge; to design a ZNE office building with the following characteristics:
- Office, 53,600 SF, 3 floors above grade.
- Minimum Window to Wall ratio: 30%
- Climate: Optional
- Building Form: Limited only by the team’s creativity
- Building Minimum Energy Code: ASHRAE 90.1-2010
- Occupants & Ventilation: 268 and ASHRAE 62.1-2007 minimum
- IT Room / Mini Data Centre: 4 racks @ 1,500 Watts
- Elevators: Two, located in the core of the building
I am happy to report that our team won the Lowest Energy Award!
THE PATH TO A ZNE BUILDING
1) Effective Goal Setting
When our team first got together, we all agreed that we wanted to create a realistic and executable design, something that was not prohibitively expensive to build in the future, and met all the relevant ASHRAE Standards for HVAC and comfort. The second thing we agreed upon was the selection of our challenging climate zone – Boulder, Colorado. We felt that the large range in external dry bulb temperature and humidity would allow us to showcase the variety of solutions that can be deployed to minimize energy consumption in both heating and cooling seasons. Our team was made up of some of the best energy modelers in the country and we wanted to show what we could achieve when given the surprisingly open-ended competition scope. Even though we all work in different states and companies, we had similar workflows, which made it easier to collaborate and each team member also found a place to contribute their own niche expertise into the final building. Through the process we all learned a lot from each other.
2) Climate Responsive Envelope
In our first design charrette we created a baseline model to determine a renewable energy potential in addition to a target EUI reduction, which is an integral part of the ZNE Building design workflow. We identified two main goals in site selection – exposed westerly façade to take advantage of westerly winds for natural ventilation and an exposed south façade to take advantage of passive solar heat gain during the summer months. This was an interesting step of the process for me, as typically the site has already been selected when I am brought on board. We optimized the envelope to work with the surrounding climate, rather than against it, and opened up the external façade with windows and louvers to facilitate natural ventilation when external temperatures and humidity levels are favorable. The most innovative feature of our building was a sawtooth façade to catch the westerly winds and bring them into the building. We also designed an atrium to funnel wind towards our building oriented vertical axis wind turbines. Both were important design features due to the relatively low wind speeds available in the area.
3) Detailed Proof of Concept
One of my main responsibilities was the internal and external computational fluid dynamics (CFD) modelling. I built up a commercial area of Colorado in the VE, which can be achieved extremely fast in IES VE as you can simply import straight from open street maps. I used this city of models to quantify the effect of the surrounding buildings on the solar energy experienced by our building, in addition to the wind velocities reaching the natural ventilation louvres and our vertical axis wind turbines. This was an important step in the proof of concept analysis for our atrium and cool towers design. I also used CFD to ensure optimum levels of thermal comfort were achieved in the occupied spaces using PPD, Operative Temperature Analysis and Particle Tracking.
If you want to learn more, I encourage you to watch this 20 minute presentation about our final design.