Case study: Laboratory opts for electrification
New laboratory building is fully electrified to help achieve energy efficiency
With sweeping local energy ordinances banning natural gas use in buildings throughout California, some building owners are electing to evaluate electrification ahead of building code mandates. For a recent Bay Area client, their new laboratory project proved to be an exciting opportunity to explore what it would take to fully electrify the facility.
The project is a seven-story laboratory and office building equipped with 60% laboratory space and 40% office space. Due to the air-change driven nature of lab projects, building heating is the dominate load for a building of this type, even with the relatively mild Bay Area climate. This is a result of high laboratory air change rates, the preheating of 100% outside air and high amounts of reheat at the zone level.
Initially, the project was on track to use high-efficiency gas-fired condensing boilers for the space heating and domestic hot water heating. While in design, the design team investigated what it would take to electrify the building systems and eliminate natural gas — all while maintaining the buildings reduced energy demand.
The first step was ensuring the base building design included energy efficiency measures to reduce building energy consumption, regardless of the method of generating cooling and heating. These included:
- High-performance window glazing and wall construction.
- Decoupled ventilation and space conditioning for office spaces to reduce reheat loads.
- Auto sash closers on fume hoods.
- Variable flow rate exhaust fans with exhaust air velocity and plume height varied based on measured wind speed.
Domestic hot water electrification was a simple primary equipment modification. The generation method switched from a gas water heater to an air source heat pump, located in the mechanical penthouse.
Water-cooled chillers and high-efficiency gas-fired condensing boilers were first chosen as methods to provide chilled water and heating hot water to the building. While the project team could have replaced the gas-fired boilers with electric boilers and achieved electrification, overall energy performance would have been sacrificed. Air source heat pumps would have provided a better method of electrification, however when compared to California’s Title 24 Energy Code, air source heat pumps still would result in an energy penalty when compared to the Code baseline.
The design team analyzed the annual building heating and cooling load profiles and a simultaneous load was identified. It was determined that by incorporating a heat recovery chiller, 48% of the annual heating demand could be electrified. While this was significant, it wasn’t nearly enough to fully electrify the building.
The addition of a run around heat recovery coil was analyzed next. While this technology is useful in extreme climates, it isn’t as useful in the mild Bay Area climate. The run around coil increased the annual heating met with electricity to 57% of the annual demand — providing only an additional 9% increase beyond that provided by the heat recovery chiller.
The building exhaust air remains a constant 70°F to 75°F year-round. By linking a heat recovery chiller with energy recovery from the exhaust air, the design team was able to electrify more than 99% of the annual heating demand. During the remaining peak heating conditions, a small electric boiler will provide any remaining heating.
Due to the infrequent use for short periods of time, the inefficiencies of the boiler are not significant on overall building heating energy. The heat recovery chillers also reject heat to the exhaust air, thus eliminating the need for the cooling towers. The change from water-cooled chillers and gas-fired boilers to heat recovery chillers and exhaust air energy recovery was not only more energy efficient, but it was more water efficient as it eliminated cooling towers completely from the project.
In addition to the energy and water savings that electrification brought to the project, the elimination of natural gas and change in the mechanical systems resulted in less than a 2% increase in project cost for owner. The main driver for full electrification of the building, however, was the reduction of greenhouse gas emissions, resulting in a 43% reduction in emissions.
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